Studies on mycorrhizal inoculation on dry matter yield and root colonization of some medicinal plants grown in stress and forest soils.

PubMed

Chandra, K K; Kumar, Neeraj; Chand, Gireesh

2010-11-01

Five medicinal plants viz. Abelmoschatus moschatus Linn., Clitoria tematea L., Plumbagozeylanica L., Psorolea corylifolia L. and Withania sominifera L. were grown in a polypot experiment in five soils representing coal mine soil, coppermine soil, fly ash, skeletal soil and forest soil with and without mycorrhizal inoculations in a completely randomized block design. Dry matter yield and mycorrhizal root colonization of plants varied both in uninoculated and inoculated conditions. The forest soil rendered highest dry matter due to higher yield of A. moschatus, P. zeylanica and P corylifolia while fly ash showed lowest dry matter without any inoculants. P. cematea were best in coalmine soil and W. sominifera in copper mine soil without mycorrhizal inoculation. The mycorrhiza was found to enhance the dry matter yield. This contributed minimum 0.19% to maximum up to 422.0% in different soils as compared to uninoculated plants. The mycorrhizal dependency was noticed maximum in plants grown in fly ash followed by coal mine soil, copper mine soil, skeletal soil and forest soil. The mycorrhizal response was increased maximum in W. sominifera due to survival in fly ash after inoculation followed by P corylifolia and P cematea. Percent root colonization in inoculated plant was increased minimum of 1.10 fold to maximum of 12.0 folds in comparison to un-inoculated plants . The native mycorrhiza fungi were also observed to colonize 4.0 to 32.0% roots in plants understudy. This study suggests that mycorrhizal inoculation increased the dry matter yield of medicinal plants in all soils under study. It also helps in survival of W. sominifera in fly ash.

Soil suppressiveness to fusarium disease: shifts in root microbiome associated with reduction of pathogen root colonization.

PubMed

Klein, Eyal; Ofek, Maya; Katan, Jaacov; Minz, Dror; Gamliel, Abraham

2013-01-01

Soil suppressiveness to Fusarium disease was induced by incubating sandy soil with debris of wild rocket (WR; Diplotaxis tenuifolia) under field conditions. We studied microbial dynamics in the roots of cucumber seedlings following transplantation into WR-amended or nonamended soil, as influenced by inoculation with Fusarium oxysporum f. sp. radicis-cucumerinum. Disease symptoms initiated in nonamended soil 6 days after inoculation, compared with 14 days in WR-amended soil. Root infection by F. oxysporum f. sp. radicis-cucumerinum was quantified using real-time polymerase chain reaction (PCR). Target numbers were similar 3 days after inoculation for both WR-amended and nonamended soils, and were significantly lower (66%) 6 days after inoculation and transplanting into the suppressive (WR-amended) soil. This decrease in root colonization was correlated with a reduction in disease (60%) 21 days after inoculation and transplanting into the suppressive soil. Fungal community composition on cucumber roots was assessed using mass sequencing of fungal internal transcribed spacer gene fragments. Sequences related to F. oxysporum, Fusarium sp. 14005, Chaetomium sp. 15003, and an unclassified Ascomycota composed 96% of the total fungal sequences in all samples. The relative abundances of these major groups were highly affected by root inoculation with F. oxysporum f. sp. radicis-cucumerinum, with a 10-fold increase in F. oxysporum sequences, but were not affected by the WR amendment. Quantitative analysis and mass-sequencing methods indicated a qualitative shift in the root's bacterial community composition in suppressive soil, rather than a change in bacterial numbers. A sharp reduction in the size and root dominance of the Massilia population in suppressive soil was accompanied by a significant increase in the relative abundance of specific populations; namely, Rhizobium, Bacillus, Paenibacillus, and Streptomyces spp. Composition of the Streptomyces community shifted significantly, as determined by PCR denaturing gradient gel electrophoresis, resulting in an increase in the dominance of a specific population in suppressive soils after only 3 days. This shift was related mainly to the increase in Streptomyces humidus, a group previously described as antagonistic to phytopathogenic fungi. Thus, suitable soil amendment resulted in a shift in the root's bacterial communities, and infection by a virulent pathogen was contained by the root microbiome, leading to a reduced disease rate.

A Vesicular Arbuscular Mycorrhizal Fungus (Glomus intraradix) Induces a Defense Response in Alfalfa Roots.

PubMed

Volpin, H.; Elkind, Y.; Okon, Y.; Kapulnik, Y.

1994-02-01

Flavonoid accumulation and activities of phenylalanine ammonia-lyase (PAL), chalcone isomerase (CHI), and chitinase were followed during early colonization of alfalfa roots (Medicago sativa L. cv Gilboa) by vesicular arbuscular (VA) fungi (Glomus intraradix). Formononetin was the only flavonoid detected that showed a consistent increase in the inoculated roots. This increase depended only on the presence of the fungus in the plant rhizosphere; no colonization of the root tissue was required. CHI and chitinase activities increased in inoculated roots prior to colonization, whereas the increase in PAL activity coincided with colonization. After reaching a maximum, activities of all enzymes declined to below those of uninoculated roots. PAL inactivation was not caused by a soluble inhibitor. Our results indicate that VA fungi initiate a host defense response in alfalfa roots, which is subsequently suppressed.

The effects of arbuscular mycorrhizal fungi and root interaction on the competition between Trifolium repens and Lolium perenne.

PubMed

Ren, Haiyan; Gao, Tao; Hu, Jian; Yang, Gaowen

2017-01-01

Understanding the factors that alter competitive interactions and coexistence between plants is a key issue in ecological research. A pot experiment was conducted to test the effects of root interaction and arbuscular mycorrhizal fungi (AMF) inoculation on the interspecies competition between Trifolium repens and Lolium perenne under different proportions of mixed sowing by the combination treatment of two levels of AMF inoculation (inoculation and non-inoculation) and two levels of root interaction (root interaction and non-root interaction). Overall, the aboveground and belowground biomass of T. repens and L. perenne were not altered by AMF inoculation across planting ratios, probably because the fertile soil reduced the positive effect of AMF on plant growth. Both inter- and intraspecies root interaction significantly decreased the aboveground biomass of T. repens , but tended to increase the aboveground biomass of L. perenne across planting ratios, and thus peaked at the 4:4 polyculture. These results showed that T. repens competed poorly with L. perenne because of inter and intraspecies root interaction. Our results indicate that interspecies root interaction regulates the competitive ability of grass L. perenne and legume T. repens in mixtures and further makes great contribution for overyielding. Furthermore, AMF may not be involved in plant-plant interaction in fertile condition.

Inoculation of drought-stressed strawberry with a mixed inoculum of two arbuscular mycorrhizal fungi: effects on population dynamics of fungal species in roots and consequential plant tolerance to water deficiency.

PubMed

Boyer, Louisa Robinson; Brain, Philip; Xu, Xiang-Ming; Jeffries, Peter

2015-04-01

The effect of inoculation with two arbuscular mycorrhizal fungi (AMF) on growth and drought tolerance of cultivated strawberry (Fragaria × ananassa) was studied. Three treatments (a single treatment either of Funneliformis mosseae BEG25, Funneliformis geosporus BEG11 or a 50:50 mixed inoculation treatment of both species) were compared to uninoculated plants. Species-specific primers for qPCR quantification of F. geosporus and F. mosseae DNA were developed to quantify the relative abundance of each fungus in roots of strawberry under different conditions of water stress. Co-occupation of the same root by both species was shown to commonly occur, but their relative abundance varied with water stress (reduced irrigation of up to 40%). Greater root colonisation was observed microscopically under water stress, but this increased colonisation was often accompanied with decreased amounts of fungal DNA in the root. F. mosseae tended to become more abundant under water stress relative to F. geosporus. There was significant correlation in the fungal colonisation measurements from the microscopic and qPCR methods under some conditions, but the nature of this relationship varied greatly with AMF inoculum and abiotic conditions. Single-species inoculation treatments gave similar benefits to the host to the mixed inoculation treatment regardless of irrigation regime; here, amount of colonisation was of greater importance than functional diversity. The addition of AMF inocula to plants subjected to reduced irrigation restored plant growth to the same or higher values as the non-mycorrhizal, fully-watered plants. The water use efficiency of plants was greater under the regulated deficit irrigation (RDI) regime and in AMF-inoculated plants, but there were no significant differences between plants inoculated with the single or combined inoculum. This study demonstrated that the increase in plant growth was directly influenced by an increase in root colonisation by AMF when individual plants were examined.

Quantitative Phosphoproteomic Analysis of Soybean Root Hairs Inoculated with Bradyrhizobium japonicum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Tran H.; Brechenmacher, Laurent; Aldrich, Joshua T.

2012-11-11

Root hairs are single hair-forming cells on roots that function to increase root surface area, enhancing water and nutrient uptake. In leguminous plants, root hairs also play a critical role as the site of infection by symbiotic nitrogen fixing rhizobia, leading to the formation of a novel organ, the nodule. The initial steps in the rhizobia-root hair infection process are known to involve specific receptor kinases and subsequent kinase cascades. Here, we characterize the phosphoproteome of the root hairs and the corresponding stripped roots (i.e., roots from which root hairs were removed) during rhizobial colonization and infection to gain insightmore » into the molecular mechanism of root hair cell biology. We chose soybean (Glycine max L.), one of the most important crop plants in the legume family, for this study because of its larger root size, which permits isolation of sufficient root hair material for phosphoproteomic analysis. Phosphopeptides derived from root hairs and stripped roots, mock inoculated or inoculated with the soybean-specific rhizobium Bradyrhizobium japonicum, were labeled with the isobaric tag 8-plex ITRAQ, enriched using Ni-NTA magnetic beads and subjected to nRPLC-MS/MS analysis using HCD and decision tree guided CID/ETD strategy. A total of 1,625 unique phosphopeptides, spanning 1,659 non-redundant phosphorylation sites, were detected from 1,126 soybean phosphoproteins. Among them, 273 phosphopeptides corresponding to 240 phosphoproteins were found to be significantly regulated (>1.5 fold abundance change) in response to inoculation with B. japonicum. The data reveal unique features of the soybean root hair phosphoproteome, including root hair and stripped root-specific phosphorylation suggesting a complex network of kinase-substrate and phosphatase-substrate interactions in response to rhizobial inoculation.« less

Carbon economy of sour orange in response to different Glomus spp.

PubMed

Graham, J. H.; Drouillard, D. L.; Hodge, N. C.

1996-01-01

Vesicular-arbuscular mycorrhizal (M) fungal colonization, growth, and nonstructural carbohydrate status of sour orange (Citrus aurantium L.) seedlings were compared at low- and high-phosphorus (P) supply following inoculation with four Glomus isolates: G. intraradices (Gi, FL208), G. etunicatum (Ge, UT316), G. claroideum (Gc, SC186), and Glomus sp. (G329, FL906). Nonmycorrhizal (NM) seedlings served as controls. At low-P supply, increases in incidence of M colonization, vesicles and accumulation of fungal fatty acid 16:1omega(5)C in roots were most rapid for G329-inoculated seedlings, followed closely by Gi- and Gc-inoculated seedlings. Glomus etunicatum was a less aggressive colonizer and produced lower rates of fungal fatty acid accumulation in seedling roots than the other Glomus species. Nonmycorrhizal and Ge-inoculated seedlings had lower P status and growth rates than seedlings inoculated with Gi or G329. Glomus claroideum increased seedling P status, but growth rate was lower than for seedlings colonized by Gi or G329, suggesting higher belowground costs for Gc colonization. In P-sufficient roots colonized by Gi, Gc, or G329, starch and ketone sugar concentrations were lower than in P-deficient NM and Ge-inoculated plants. Under conditions of high-P supply where mycorrhizae provided no P benefit to the seedlings, colonization by Gc, Gi, and G329 was delayed and reduced compared to that at low-P supply; however, the relative colonization rates among Glomus spp. were similar. Colonization by Ge was not detected in roots until 64 days after inoculation. Compared to NM seedlings, growth rates of mycorrhizal seedlings were reduced by the three aggressive fungi but not by the less aggressive Ge. After 64 days, starch and ketone sugar concentrations were lower in fibrous roots colonized by Gc, Gi, and G329 than in NM roots, indicating greater utilization of nonstructural carbohydrates in roots colonized by the aggressive fungi. After 49 days, colonization by the aggressive fungi increased root biomass allocation which may have contributed to the lower growth rate of mycorrhizal seedlings compared to NM seedlings. Thus, Glomus spp. that were aggressive colonizers of roots at low-P supply were also aggressive colonizers at high-P supply, resulting in greater belowground C costs and growth depression compared with the less aggressive colonizer, Ge.

Co-inoculation of Lolium perenne with Funneliformis mosseae and the dark septate endophyte Cadophora sp. in a trace element-polluted soil.

PubMed

Berthelot, Charlotte; Blaudez, Damien; Beguiristain, Thierry; Chalot, Michel; Leyval, Corinne

2018-04-01

The presence of dark septate endophytes (DSEs) or arbuscular mycorrhizal fungi (AMF) in plant roots and their effects on plant fitness have been extensively described. However, little is known about their interactions when they are simultaneously colonizing a plant root, especially in trace element (TE)-polluted soils. We therefore investigated the effects of Cadophora sp. and Funneliformis mosseae on ryegrass (Lolium perenne) growth and element uptake in a Cd/Zn/Pb-polluted soil. The experiment included four treatments, i.e., inoculation with Cadophora sp., inoculation with F. mosseae, co-inoculation with Cadophora sp. and F. mosseae, and no inoculation. Ryegrass biomass and shoot Na, P, K, and Mg concentrations significantly increased following AMF inoculation as compared to non-inoculated controls. Similarly, DSE inoculation increased shoot Na concentration, whereas dual inoculation significantly decreased shoot Cd concentration. Moreover, oxidative stress determined by ryegrass leaf malondialdehyde concentration was alleviated both in the AMF and dual inoculation treatments. We used quantitative PCR and microscope observations to quantify colonization rates. They demonstrated that DSEs had no effect on AMF colonization, while AMF colonization slightly decreased DSE frequency. We also monitored fluorescein diacetate (FDA) hydrolysis and alkaline phosphatase (AP) activity in the rhizosphere soils. FDA hydrolysis remained unchanged in the three inoculated treatments, but AMF colonization increased AP activity and P mobility in the soil whereas DSE colonization did not alter AP activity. In this experiment, we unveiled the interactions between two ecologically important fungal groups likely to occur in roots which involved a decrease of oxidative stress and Cd accumulation in shoots. These results open promising perspectives on the fungal-based phytomanagement of TE-contaminated sites by the production of uncontaminated and marketable plant biomass.

Effect of two vesicular-arbuscular mycorrhizal fungi on the growth of micropropagated potato plantlets and on the extent of disease caused by Rhizoctonia solani.

PubMed

Yao, M K; Tweddell, R J; Désilets, H

2002-10-01

Two micropropagated potato cultivars, Goldrush and LP89221, were inoculated into sowing trays with either Glomus etunicatum or G. intraradices in a greenhouse. After 2 weeks, plantlets were transplanted into pots and roots were challenged 7 days later with Rhizoctonia solani. At different times after R. solani infection, disease severity, mortality rate, root colonization levels, various growth parameters, and shoot mineral content were evaluated. In Goldrush, only inoculation with G. etunicatum led to a significant reduction in disease severity, ranging between 60.2% and 71.2%, on both shoot and crown. This decrease was not observed in LP89221. Compared with the control plantlets, inoculation of Goldrush with G. etunicatum or G. intraradices reduced significantly the mortality rate by 77% and 26%, respectively, whereas vesicular-arbuscular mycorrhizal (VAM) fungi did not significantly influence the mortality rate in LP89221. In Goldrush, inoculation with G. etunicatum significantly increased shoot fresh weight, root dry weight and the number of tubers produced per plant, whereas G. intraradices only significantly increased the number of tubers. Tuber and root fresh weights of both potato cultivars were significantly reduced by R. solani infection. However, R. solani-infected plantlets of both Goldrush and LP89221, inoculated with G. etunicatum, produced significantly greater tuber fresh weight than non-VAM plantlets. In R. solani-infected plantlets of Goldrush but not LP89221, G. etunicatum and G. intraradices increased root fresh weight by approximately 140.3% and 76.5%, respectively, compared with non-VAM plants. The potato cultivars Goldrush and LP89221 responded differently to VAM fungal inoculation and to R. solani infection in terms of shoot mineral content.

Effects of arbuscular mycorrhizal fungi inoculation on carbon and nitrogen distribution and grain yield and nutritional quality in rice (Oryza sativa L.).

PubMed

Zhang, Xue; Wang, Li; Ma, Fang; Yang, Jixian; Su, Meng

2017-07-01

The importance of arbuscular mycorrhizal fungi (AMF) for nutrient uptake and growth in rice has been widely recognized. However, little is known about the distribution of carbon (C) and nitrogen (N) in rice under AMF inoculation, which can affect grain yield and quality. This study was conducted to investigate the distribution of C and N within rice plants under AMF inoculation and the effects on grain yield and quality. AMF inoculation significantly increased N accumulation and distribution in vegetative tissues at tillering, and N translocation into seeds from heading to maturity. Consequently, AMF inoculation more strongly impacted the distribution of N than that of C in seeds, with significantly reduced C:N ratios and increased protein content (by 7.4%). Additionally, AMF inoculation significantly increased grain yield by 28.2% through increasing the grain:straw ratio by 18.4%. In addition, the roots of inoculated rice exhibited greater change in C distribution, with significantly higher C concentrations, C accumulations, and C:N ratios at tillering and maturity. AMF inoculation affected the distribution of N in seeds and C in roots. As such, AMF inoculation may be a potential method for improving grain yield and quality. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Effects of root inoculation with bacteria on the growth, Cd uptake and bacterial communities associated with rape grown in Cd-contaminated soil.

PubMed

Chen, Zhao-jin; Sheng, Xia-fang; He, Lin-yan; Huang, Zhi; Zhang, Wen-hui

2013-01-15

Two metal-resistant and plant growth-promoting bacteria (Burkholderia sp. J62 and Pseudomonas thivervalensis Y-1-3-9) were evaluated for their impacts on plant growth promotion, Cd availability in soil, and Cd uptake in rape (Brassica napus) grown in different level (0, 50, and 100 mg kg(-1)) of Cd-contaminated soils. The impacts of the bacteria on the rape-associated bacterial community structures were also evaluated using denaturing gradient gel electrophoresis (DGGE) analysis of bacterial DNA extracted from the root interior and rhizosphere and bulk soil samples collected at day 60 after inoculation. Canonical correspondence analysis (CCA) was used to have a comparative analysis of DGGE profiles. Inoculation with live bacteria not only significantly increased root (ranging from 38% to 86%), stem (ranging from 27% to 65%) and leaf (ranging from 23% to 55%) dry weights and water-extractive Cd contents (ranging from 59% to 237%) in the rhizosphere soils of the rape but also significantly increased root (ranging from 10% to 61%), stem (ranging from 41% to 57%) and leaf (ranging from 46% to 68%) total Cd uptake of rape compared to the dead bacterial-inoculated controls. DGGE and sequence analyses showed that the bacteria could colonize the rhizosphere soils and root interiors of rape plants. DGGE-CCA also showed that root interior and rhizosphere and bulk soil community profiles from the live bacteria-inoculated rape were significantly different from those from the dead bacteria-inoculated rape respectively. These results suggested that the bacteria had the potential to promote the growth and Cd uptake of rape and to influence the development of the rape-associated bacterial community structures. Copyright © 2012 Elsevier B.V. All rights reserved.

Metabolomics Suggests That Soil Inoculation with Arbuscular Mycorrhizal Fungi Decreased Free Amino Acid Content in Roots of Durum Wheat Grown under N-Limited, P-Rich Field Conditions.

PubMed

Saia, Sergio; Ruisi, Paolo; Fileccia, Veronica; Di Miceli, Giuseppe; Amato, Gaetano; Martinelli, Federico

2015-01-01

Arbuscular mycorrhizal fungi (AMF) have a major impact on plant nutrition, defence against pathogens, a plant's reaction to stressful environments, soil fertility, and a plant's relationship with other microorganisms. Such effects imply a broad reprogramming of the plant's metabolic activity. However, little information is available regarding the role of AMF and their relation to other soil plant growth-promoting microorganisms in the plant metabolome, especially under realistic field conditions. In the present experiment, we evaluated the effects of inoculation with AMF, either alone or in combination with plant growth-promoting rhizobacteria (PGPR), on the metabolome and changes in metabolic pathways in the roots of durum wheat (Triticum durum Desf.) grown under N-limited agronomic conditions in a P-rich environment. These two treatments were compared to infection by the natural AMF population (NAT). Soil inoculation with AMF almost doubled wheat root colonization by AMF and decreased the root concentrations of most compounds in all metabolic pathways, especially amino acids (AA) and saturated fatty acids, whereas inoculation with AMF+PGPR increased the concentrations of such compounds compared to inoculation with AMF alone. Enrichment metabolomics analyses showed that AA metabolic pathways were mostly changed by the treatments, with reduced amination activity in roots most likely due to a shift from the biosynthesis of common AA to γ-amino butyric acid. The root metabolome differed between AMF and NAT but not AMF+PGPR and AMF or NAT. Because the PGPR used were potent mineralisers, and AMF can retain most nitrogen (N) taken as organic compounds for their own growth, it is likely that this result was due to an increased concentration of mineral N in soil inoculated with AMF+PGPR compared to AMF alone.

Interaction of Vesicular-Arbuscular Mycorrhizae and Cultivars of Alfalfa Susceptible and Resistant to Meloidogyne hapla.

PubMed

Grandison, G S; Cooper, K M

1986-04-01

The interaction between vesicular-arbuscular mycorrhizal (VAM) fungi and the root-knot nematode (Meloidogyne hapla) was investigated using both nematode-susceptible (Grasslands Wairau) and nematode-resistant (Nevada Synthetic XX) cultivars of alfalfa (Medicago sativa) at four levels of applied phosphate. Mycorrhizal inoculation improved plant growth and reduced nematode numbers and adult development in roots in dually infected cultures of the susceptible cultivar. The tolerance of plants to nematode infection and development when preinfected with mycorrhizal fungi was no greater than when they were inoculated with nematodes and mycorrhizal fungi simultaneously. Growth of plants of the resistant cultivar was unaffected by nematode inoculation but was improved by mycorrhizal inoculation. Numbers of nematode juveniles were lower in the roots of the resistant than of the susceptible cultivar and were further reduced by mycorrhizal inoculation, although no adult nematodes developed in any resistant cultivar treatment. Inoculation of alfalfa with VAM fungi increased the tolerance and resistance of a cultivar susceptible to M. hapla and improved the resistance of a resistant cultivar.

Cytokinin-producing, plant growth-promoting rhizobacteria that confer resistance to drought stress in Platycladus orientalis container seedlings.

PubMed

Liu, Fangchun; Xing, Shangjun; Ma, Hailin; Du, Zhenyu; Ma, Bingyao

2013-10-01

One of the proposed mechanisms through which plant growth-promoting rhizobacteria (PGPR) enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available regarding cytokinin-producing PGPR inoculation on growth and water stress consistence of forest container seedlings under drought condition. This study determined the effects of Bacillus subtilis on hormone concentration, drought resistance, and plant growth under water-stressed conditions. Although no significant difference was observed under well-watered conditions, leaves of inoculated Platycladus orientalis (oriental thuja) seedlings under drought stress had higher relative water content and leaf water potential compared with those of noninoculated ones. Regardless of water supply levels, the root exudates, namely sugars, amino acids and organic acids, significantly increased because of B. subtilis inoculation. Water stress reduced shoot cytokinins by 39.14 %. However, inoculation decreased this deficit to only 10.22 %. The elevated levels of cytokinins in P. orientalis shoot were associated with higher concentration of abscisic acid (ABA). Stomatal conductance was significantly increased by B. subtilis inoculation in well-watered seedlings. However, the promoting effect of cytokinins on stomatal conductance was hampered, possibly by the combined action of elevated cytokinins and ABA. B. subtilis inoculation increased the shoot dry weight of well-watered and drought seedlings by 34.85 and 19.23 %, as well as the root by 15.445 and 13.99 %, respectively. Consequently, the root/shoot ratio significantly decreased, indicative of the greater benefits of PGPR on shoot growth than root. Thus, inoculation of cytokinin-producing PGPR in container seedlings can alleviate the drought stress and interfere with the suppression of shoot growth, showing a real potential to perform as a drought stress inhibitor in arid environments.

Inoculation effects on root-colonizing arbuscular mycorrhizal fungal communities spread beyond directly inoculated plants

PubMed Central

Krak, Karol; Vosátka, Miroslav; Püschel, David; Štorchová, Helena

2017-01-01

Inoculation with arbuscular mycorrhizal fungi (AMF) may improve plant performance at disturbed sites, but inoculation may also suppress root colonization by native AMF and decrease the diversity of the root-colonizing AMF community. This has been shown for the roots of directly inoculated plants, but little is known about the stability of inoculation effects, and to which degree the inoculant and the inoculation-induced changes in AMF community composition spread into newly emerging seedlings that were not in direct contact with the introduced propagules. We addressed this topic in a greenhouse experiment based on the soil and native AMF community of a post-mining site. Plants were cultivated in compartmented pots with substrate containing the native AMF community, where AMF extraradical mycelium radiating from directly inoculated plants was allowed to inoculate neighboring plants. The abundances of the inoculated isolate and of native AMF taxa were monitored in the roots of the directly inoculated plants and the neighboring plants by quantitative real-time PCR. As expected, inoculation suppressed root colonization of the directly inoculated plants by other AMF taxa of the native AMF community and also by native genotypes of the same species as used for inoculation. In the neighboring plants, high abundance of the inoculant and the suppression of native AMF were maintained. Thus, we demonstrate that inoculation effects on native AMF propagate into plants that were not in direct contact with the introduced inoculum, and are therefore likely to persist at the site of inoculation. PMID:28738069

Inoculation effects on root-colonizing arbuscular mycorrhizal fungal communities spread beyond directly inoculated plants.

PubMed

Janoušková, Martina; Krak, Karol; Vosátka, Miroslav; Püschel, David; Štorchová, Helena

2017-01-01

Inoculation with arbuscular mycorrhizal fungi (AMF) may improve plant performance at disturbed sites, but inoculation may also suppress root colonization by native AMF and decrease the diversity of the root-colonizing AMF community. This has been shown for the roots of directly inoculated plants, but little is known about the stability of inoculation effects, and to which degree the inoculant and the inoculation-induced changes in AMF community composition spread into newly emerging seedlings that were not in direct contact with the introduced propagules. We addressed this topic in a greenhouse experiment based on the soil and native AMF community of a post-mining site. Plants were cultivated in compartmented pots with substrate containing the native AMF community, where AMF extraradical mycelium radiating from directly inoculated plants was allowed to inoculate neighboring plants. The abundances of the inoculated isolate and of native AMF taxa were monitored in the roots of the directly inoculated plants and the neighboring plants by quantitative real-time PCR. As expected, inoculation suppressed root colonization of the directly inoculated plants by other AMF taxa of the native AMF community and also by native genotypes of the same species as used for inoculation. In the neighboring plants, high abundance of the inoculant and the suppression of native AMF were maintained. Thus, we demonstrate that inoculation effects on native AMF propagate into plants that were not in direct contact with the introduced inoculum, and are therefore likely to persist at the site of inoculation.

Involvement of hexokinase1 in plant growth promotion as mediated by Burkholderia phytofirmans.

PubMed

Park, Jae Min; Lazarovits, George

2014-06-01

Potato plantlets inoculated with strain PsJN of the bacterium Burkholderia phytofirmans exhibit consistent and significant increases in plant growth under in vitro conditions, when compared with uninoculated plants. The greatest influence on the degree and type of growth enhancement that develops has been shown to be mediated by the sugar concentration in the agar media. Bacterial growth promotion has been suggested in other studies to be regulated by the sugar sensor enzyme hexokinase1, the role of which is activation of glucose phosphorylation. In this present study, we examined the co-relationship between root and stem development in potato plants treated with PsJN and the activity of hexokinase1. Plants grown in the presence of 1.5% and 3% sucrose showed increased levels of hexokinase1 activity only in the roots of inoculated plants, suggesting that the increased enzyme levels may be associated with root growth. Analysis for mRNA using reverse transcriptase did not reveal any significant differences in transcription levels of the gene between inoculated and uninoculated plants. When PsJN-inoculated plants were grown in 1.5% and 3% concentrations of glucose and fructose, stem height and mass, leaf number, root mass, and overall biomass increased. No growth promotion occurred when PsJN-inoculated plants were grown in 3% maltose. Subsequently, a hexokinase1 activity assay showed that PsJN-induced growth of potato plants was found to only occur when plants were grown in the presence of sugars that are recognized by the plant hexokinase1. The results suggest that PsJN may enhance sugar uptake in plants by direct or indirect stimulation of hexokinase1 activity in roots and this results in enhanced overall plant growth.

Endophytic Colonization of Rice by a Diazotrophic Strain of Serratia marcescens

PubMed Central

Gyaneshwar, Prasad; James, Euan K.; Mathan, Natarajan; Reddy, Pallavolu M.; Reinhold-Hurek, Barbara; Ladha, Jagdish K.

2001-01-01

Six closely related N2-fixing bacterial strains were isolated from surface-sterilized roots and stems of four different rice varieties. The strains were identified as Serratia marcescens by 16S rRNA gene analysis. One strain, IRBG500, chosen for further analysis showed acetylene reduction activity (ARA) only when inoculated into media containing low levels of fixed nitrogen (yeast extract). Diazotrophy of IRBG500 was confirmed by measurement of 15N2 incorporation and by sequence analysis of the PCR-amplified fragment of nifH. To examine its interaction with rice, strain IRBG500 was marked with gusA fused to a constitutive promoter, and the marked strain was inoculated onto rice seedlings under axenic conditions. At 3 days after inoculation, the roots showed blue staining, which was most intense at the points of lateral root emergence and at the root tip. At 6 days, the blue precipitate also appeared in the leaves and stems. More detailed studies using light and transmission electron microscopy combined with immunogold labeling confirmed that IRBG500 was endophytically established within roots, stems, and leaves. Large numbers of bacteria were observed within intercellular spaces, senescing root cortical cells, aerenchyma, and xylem vessels. They were not observed within intact host cells. Inoculation of IRBG500 resulted in a significant increase in root length and root dry weight but not in total N content of rice variety IR72. The inoculated plants showed ARA, but only when external carbon (e.g., malate, succinate, or sucrose) was added to the rooting medium. PMID:11274124

Co-Inoculation with Rhizobia and AMF Inhibited Soybean Red Crown Rot: From Field Study to Plant Defense-Related Gene Expression Analysis

PubMed Central

Gao, Xiang; Lu, Xing; Wu, Man; Zhang, Haiyan; Pan, Ruqian; Tian, Jiang; Li, Shuxian; Liao, Hong

2012-01-01

Background Soybean red crown rot is a major soil-borne disease all over the world, which severely affects soybean production. Efficient and sustainable methods are strongly desired to control the soil-borne diseases. Principal Findings We firstly investigated the disease incidence and index of soybean red crown rot under different phosphorus (P) additions in field and found that the natural inoculation of rhizobia and arbuscular mycorrhizal fungi (AMF) could affect soybean red crown rot, particularly without P addition. Further studies in sand culture experiments showed that inoculation with rhizobia or AMF significantly decreased severity and incidence of soybean red crown rot, especially for co-inoculation with rhizobia and AMF at low P. The root colony forming unit (CFU) decreased over 50% when inoculated by rhizobia and/or AMF at low P. However, P addition only enhanced CFU when inoculated with AMF. Furthermore, root exudates of soybean inoculated with rhizobia and/or AMF significantly inhibited pathogen growth and reproduction. Quantitative RT-PCR results indicated that the transcripts of the most tested pathogen defense-related (PR) genes in roots were significantly increased by rhizobium and/or AMF inoculation. Among them, PR2, PR3, PR4 and PR10 reached the highest level with co-inoculation of rhizobium and AMF. Conclusions Our results indicated that inoculation with rhizobia and AMF could directly inhibit pathogen growth and reproduction, and activate the plant overall defense system through increasing PR gene expressions. Combined with optimal P fertilization, inoculation with rhizobia and AMF could be considered as an efficient method to control soybean red crown rot in acid soils. PMID:22442737

Evidence for the endophytic colonization of Phaseolus vulgaris (common bean) roots by the diazotroph Herbaspirillum seropedicae.

PubMed

Schmidt, M A; Souza, E M; Baura, V; Wassem, R; Yates, M G; Pedrosa, F O; Monteiro, R A

2011-03-01

Herbaspirillum seropedicae is an endophytic diazotrophic bacterium, which associates with important agricultural plants. In the present study, we have investigated the attachment to and internal colonization of Phaseolus vulgaris roots by the H. seropedicae wild-type strain SMR1 and by a strain of H. seropedicae expressing a red fluorescent protein (DsRed) to track the bacterium in the plant tissues. Two-day-old P. vulgaris roots were incubated at 30°C for 15 min with 6 x 10(8) CFU/mL H. seropedicae SMR1 or RAM4. Three days after inoculation, 4 x 10(4) cells of endophytic H. seropedicae SMR1 were recovered per gram of fresh root, and 9 days after inoculation the number of endophytes increased to 4 x 10(6) CFU/g. The identity of the recovered bacteria was confirmed by amplification and sequencing of the 16SrRNA gene. Furthermore, confocal microscopy of P. vulgaris roots inoculated with H. seropedicae RAM4 showed that the bacterial cells were attached to the root surface 15 min after inoculation; fluorescent bacteria were visible in the internal tissues after 24 h and were found in the central cylinder after 72 h, showing that H. seropedicae RAM4 is capable of colonizing the roots of the dicotyledon P. vulgaris. Determination of dry weight of common bean inoculated with H. seropedicae SMR1 suggested that this bacterium has a negative effect on the growth of P. vulgaris.

Long-term tracing of Rhizophagus irregularis isolate BEG140 inoculated on Phalaris arundinacea in a coal mine spoil bank, using mitochondrial large subunit rDNA markers.

PubMed

Sýkorová, Zuzana; Börstler, Boris; Zvolenská, Soňa; Fehrer, Judith; Gryndler, Milan; Vosátka, Miroslav; Redecker, Dirk

2012-01-01

During the last decade, the application of arbuscular mycorrhizal fungi (AMF) as bioenhancers has increased significantly. However, until now, it has been difficult to verify the inoculation success in terms of fungal symbiont establishment in roots of inoculated plants because specific fungal strains could not be detected within colonized roots. Using mitochondrial large subunit ribosomal DNA, we show that Rhizophagus irregularis (formerly known as Glomus intraradices) isolate BEG140 consists of two different haplotypes. We developed nested PCR assays to specifically trace each of the two haplotypes in the roots of Phalaris arundinacea from a field experiment in a spoil bank of a former coal mine, where BEG140 was used as inoculant. We revealed that despite the relatively high diversity of native R. irregularis strains, R. irregularis BEG140 survived and proliferated successfully in the field experiment and was found significantly more often in the inoculated than control plots. This work is the first one to show tracing of an inoculated AMF isolate in the roots of target plants and to verify its survival and propagation in the field. These results will have implications for basic research on the ecology of AMF at the intraspecific level as well as for commercial users of mycorrhizal inoculation.

Rhizosphere Microbiomes Modulated by Pre-crops Assisted Plants in Defense Against Plant-Parasitic Nematodes

PubMed Central

Elhady, Ahmed; Adss, Shimaa; Hallmann, Johannes; Heuer, Holger

2018-01-01

Plant-parasitic nematodes cause considerable damage to crop plants. The rhizosphere microbiome can affect invasion and reproductive success of plant-parasitic nematodes, thus affecting plant damage. In this study, we investigated how the transplanted rhizosphere microbiome from different crops affect plant-parasitic nematodes on soybean or tomato, and whether the plant’s own microbiome from the rhizosphere protects it better than the microbiome from fallow soil. Soybean plants growing in sterilized substrate were inoculated with the microbiome extracted from the rhizosphere of soybean, maize, or tomato. Controls were inoculated with extracts from bulk soil, or not inoculated. After the microbiome was established, the root lesion nematode Pratylenchus penetrans was added. Root invasion of P. penetrans was significantly reduced on soybean plants inoculated with the microbiome from maize or soybean compared to tomato or bulk soil, or the uninoculated control. In the analogous experiment with tomato plants inoculated with either P. penetrans or the root knot nematode Meloidogyne incognita, the rhizosphere microbiomes of maize and tomato reduced root invasion by P. penetrans and M. incognita compared to microbiomes from soybean or bulk soil. Reproduction of M. incognita on tomato followed the same trend, and it was best suppressed by the tomato rhizosphere microbiome. In split-root experiments with soybean and tomato plants, a systemic effect of the inoculated rhizosphere microbiomes on root invasion of P. penetrans was shown. Furthermore, some transplanted microbiomes slightly enhanced plant growth compared to uninoculated plants. The microbiomes from maize rhizosphere and bulk soil increased the fresh weights of roots and shoots of soybean plants, and microbiomes from soybean rhizosphere and bulk soil increased the fresh weights of roots and shoots of tomato plants. Nematode invasion did not affect plant growth in these short-term experiments. In conclusion, this study highlights the importance of the rhizosphere microbiome in protecting crops against plant-parasitic nematodes. An effect of pre-crops on the rhizosphere microbiome might be harnessed to enhance the resistance of crops towards plant-parasitic nematodes. However, nematode-suppressive effects of a particular microbiome may not necessarily coincide with improvement of plant growth in the absence of plant-parasitic nematodes. PMID:29915566

Behavior of mercury in a soil-plant system as affected by inoculation with the arbuscular mycorrhizal fungus Glomus mosseae.

PubMed

Yu, Yang; Zhang, Shuzhen; Huang, Honglin

2010-08-01

Effects of inoculation with the arbuscular mycorrhizal (AM) fungus Glomus mosseae on the behavior of Hg in soil-plant system were investigated using an artificially contaminated soil at the concentrations of 0, 1.0, 2.0, and 4.0 mg Hg kg(-1). Mercury accumulation was lower in mycorrhizal roots than in nonmycorrhizal roots when Hg was added at the rates of 2.0 and 4.0 mg kg(-1), while no obvious difference in shoot Hg concentration was found between mycorrhizal and nonmycorrhizal treatments. Mycorrhizal inoculation significantly decreased the total and extractable Hg concentrations in soil as well as the ratio of extractable to total Hg in soil. Equilibration sorption of Hg by soil was investigated, and the results indicated that mycorrhizal treatment enhanced Hg sorption on soil. The uptake of Hg was lower by mycorrhizal roots than by nonmycorrhizal roots. These experiments provide further evidence for the role of mycorrhizal inoculation in increasing immobilization of Hg in soil and reducing the uptake of Hg by roots. Calculation on mass balance of Hg in soil suggests the presence of Hg loss from soil presumably through evaporation, and AM inoculation enhanced Hg evaporation. This was evidenced by a chamber study to detect the Hg evaporated from soil.

Subcellular Compartmentalization and Chemical Forms of Lead Participate in Lead Tolerance of Robinia pseudoacacia L. with Funneliformis mosseae

PubMed Central

Huang, Li; Zhang, Haoqiang; Song, Yingying; Yang, Yurong; Chen, Hui; Tang, Ming

2017-01-01

The effect of arbuscular mycorrhizal fungus on the subcellular compartmentalization and chemical forms of lead (Pb) in Pb tolerance plants was assessed in a pot experiment in greenhouse conditions. We measured root colonization, plant growth, photosynthesis, subcellular compartmentalization and chemical forms of Pb in black locust (Robinia pseudoacacia L.) seedlings inoculated with Funneliformis mosseae isolate (BGC XJ01A) under a range of Pb treatments (0, 90, 900, and 3000 mg Pb kg-1 soil). The majority of Pb was retained in the roots of R. pseudoacacia under Pb stress, with a significantly higher retention in the inoculated seedlings. F. mosseae inoculation significantly increased the proportion of Pb in the cell wall and soluble fractions and decreased the proportion of Pb in the organelle fraction of roots, stems, and leaves, with the largest proportion of Pb segregated in the cell wall fraction. F. mosseae inoculation increased the proportion of inactive Pb (especially pectate- and protein-integrated Pb and Pb phosphate) and reduced the proportion of water-soluble Pb in the roots, stems, and leaves. The subcellular compartmentalization of Pb in different chemical forms was highly correlated with improved plant biomass, height, and photosynthesis in the inoculated seedlings. This study indicates that F. mosseae could improve Pb tolerance in R. pseudoacacia seedlings growing in Pb polluted soils. PMID:28443111

Arbuscular Mycorrhizal Symbiosis with Arundo donax Decreases Root Respiration and Increases Both Photosynthesis and Plant Biomass Accumulation.

PubMed

Romero-Munar, Antònia; Del-Saz, Néstor Fernández; Ribas-Carbó, Miquel; Flexas, Jaume; Baraza, Elena; Florez-Sarasa, Igor; Fernie, Alisdair Robert; Gulías, Javier

2017-07-01

The effect of arbuscular mycorrhiza (AM) symbiosis on plant growth is associated with the balance between costs and benefits. A feedback regulation loop has been described in which the higher carbohydrate cost to plants for AM symbiosis is compensated by increases in their photosynthetic rates. Nevertheless, plant carbon balance depends both on photosynthetic carbon uptake and respiratory carbon consumption. The hypothesis behind this research was that the role of respiration in plant growth under AM symbiosis may be as important as that of photosynthesis. This hypothesis was tested in Arundo donax L. plantlets inoculated with Rhizophagus irregularis and Funneliformis mosseae. We tested the effects of AM inoculation on both photosynthetic capacity and in vivo leaf and root respiration. Additionally, analyses of the primary metabolism and ion content were performed in both leaves and roots. AM inoculation increased photosynthesis through increased CO 2 diffusion and electron transport in the chloroplast. Moreover, respiration decreased only in AM roots via the cytochrome oxidase pathway (COP) as measured by the oxygen isotope technique. This decline in the COP can be related to the reduced respiratory metabolism and substrates (sugars and tricarboxylic acid cycle intermediates) observed in roots. © 2017 John Wiley & Sons Ltd.

Maize water status and physiological traits as affected by root endophytic fungus Piriformospora indica under combined drought and mechanical stresses.

PubMed

Hosseini, Fatemeh; Mosaddeghi, Mohammad Reza; Dexter, Anthony Roger; Sepehri, Mozhgan

2018-05-01

Under combined drought and mechanical stresses, mechanical stress primarily controlled physiological responses of maize. Piriformospora indica mitigated the adverse effects of stresses, and inoculated maize experienced less oxidative damage and had better adaptation to stressful conditions. The objective of this study was to investigate the effect of maize root colonization by an endophytic fungus P. indica on plant water status, physiological traits and root morphology under combined drought and mechanical stresses. Seedlings of inoculated and non-inoculated maize (Zea mays L., cv. single cross 704) were cultivated in growth chambers filled with moistened siliceous sand at a matric suction of 20 hPa. Drought stress was induced using PEG 6000 solution with osmotic potentials of 0, - 0.3 and - 0.5 MPa. Mechanical stress (i.e., penetration resistances of 1.05, 4.23 and 6.34 MPa) was exerted by placing weights on the surface of the sand medium. After 30 days, leaf water potential (LWP) and relative water content (RWC), root and shoot fresh weights, root volume (RV) and diameter (RD), leaf proline content, leaf area (LA) and catalase (CAT) and ascorbate peroxidase (APX) activities were measured. The results show that exposure to individual drought and mechanical stresses led to higher RD and proline content and lower plant biomass, RV and LA. Moreover, increasing drought and mechanical stress severity increased APX activity by about 1.9- and 3.1-fold compared with the control. When plants were exposed to combined stresses, mechanical stress played the dominant role in controlling plant responses. P. indica-inoculated plants are better adapted to individual and combined stresses. The inoculated plants had greater RV, LA, RWC, LWP and proline content under stressful conditions. In comparison with non-inoculated plants, inoculated plants showed lower CAT and APX activities which means that they experienced less oxidative stress induced by stressful conditions.

Metabolomics Suggests That Soil Inoculation with Arbuscular Mycorrhizal Fungi Decreased Free Amino Acid Content in Roots of Durum Wheat Grown under N-Limited, P-Rich Field Conditions

PubMed Central

Saia, Sergio; Ruisi, Paolo; Fileccia, Veronica; Di Miceli, Giuseppe; Amato, Gaetano; Martinelli, Federico

2015-01-01

Arbuscular mycorrhizal fungi (AMF) have a major impact on plant nutrition, defence against pathogens, a plant’s reaction to stressful environments, soil fertility, and a plant’s relationship with other microorganisms. Such effects imply a broad reprogramming of the plant’s metabolic activity. However, little information is available regarding the role of AMF and their relation to other soil plant growth—promoting microorganisms in the plant metabolome, especially under realistic field conditions. In the present experiment, we evaluated the effects of inoculation with AMF, either alone or in combination with plant growth–promoting rhizobacteria (PGPR), on the metabolome and changes in metabolic pathways in the roots of durum wheat (Triticum durum Desf.) grown under N-limited agronomic conditions in a P-rich environment. These two treatments were compared to infection by the natural AMF population (NAT). Soil inoculation with AMF almost doubled wheat root colonization by AMF and decreased the root concentrations of most compounds in all metabolic pathways, especially amino acids (AA) and saturated fatty acids, whereas inoculation with AMF+PGPR increased the concentrations of such compounds compared to inoculation with AMF alone. Enrichment metabolomics analyses showed that AA metabolic pathways were mostly changed by the treatments, with reduced amination activity in roots most likely due to a shift from the biosynthesis of common AA to γ-amino butyric acid. The root metabolome differed between AMF and NAT but not AMF+PGPR and AMF or NAT. Because the PGPR used were potent mineralisers, and AMF can retain most nitrogen (N) taken as organic compounds for their own growth, it is likely that this result was due to an increased concentration of mineral N in soil inoculated with AMF+PGPR compared to AMF alone. PMID:26067663

Effects of the inoculation of Burkholderia vietnamensis and related endophytic diazotrophic bacteria on grain yield of rice.

PubMed

Govindarajan, Munusamy; Balandreau, Jacques; Kwon, Soon-Wo; Weon, Hang-Yeon; Lakshminarasimhan, Cunthipuram

2008-01-01

During a survey of endophytic diazotrophic bacteria associated with different rice varieties in Tamilnadu, some "endophytes" were obtained. Thirteen bacterial isolates from surface-sterilized roots and shoots were obtained in pure culture, which produced indole acetic acid (IAA) and reduced acetylene to ethylene. Polymerase chain reaction (PCR) amplification confirmed the presence of nif-H gene in all the isolates. Morphological, biochemical, and molecular characteristics indicated that all of them belonged to the genus Burkholderia One of them, MGK3, was consistently more active in reducing acetylene, and 16S rDNA sequences of isolate MGK3 confirmed its identification as Burkholderia vietnamiensis. Colonization of rice root was confirmed by strain MGK3 marked with gusA gene. The inoculated roots showed a blue color, which was most intense at the points of lateral root emergence and at the root tip. Transverse sections of roots, 15 days after inoculation, revealed beta-glucuronidase (GUS) activity within many of the cortical intercellular spaces next to the stele and within the aerenchyma. Nitrogen fixation was quantified by using (15)N isotope dilution method with two different cultivars grown in pot and field experiments. Higher nitrogen fixation was observed in variety Ponni than in ADT-43, where nearly 42% (field) and 40% (pot) of the nitrogen was derived from the atmosphere (% Ndfa). Isolate MGK3 was used to inoculate rice seedlings in a comparison with four other diazotrophs, viz., Gluconacetobacter diazotrophicus LMG7603, Herbaspirillum seropedicae LMG6513, Azospirillum lipoferum 4B LMG4348, and B. vietnamiensis LMG10929. They were used to conduct two pot and four field inoculation experiments. MGK3 alone, and combined with other diazotrophs, performed best under both pot and field conditions: combined inoculation produced yield increases between 9.5 and 23.6%, while MGK3 alone increased yield by 5.6 to 12.16% over the uninoculated control treatment.

Phenological and phytochemical changes correlate with differential interactions of Verticillium dahliae with broccoli and cauliflower.

PubMed

Njoroge, S M C; Vallad, G E; Park, S-Y; Kang, S; Koike, S T; Bolda, M; Burman, P; Polonik, W; Subbarao, K V

2011-05-01

Cauliflower (Brassica oleracea var. botrytis subvar. cauliflora) is susceptible to wilt caused by Verticillium dahliae but broccoli (B. oleracea var. italica subvar. cyamosa) is not. Infection of broccoli and cauliflower by a green fluorescent protein-expressing isolate of V. dahliae was examined using epifluorescence and confocal laser-scanning microscopy to follow infection and colonization in relation to plant phenology. Plant glucosinolate, phenolic, and lignin contents were also assayed at 0, 4, 14, and 28 days postinoculation. V. dahliae consistently infected and colonized the vascular tissues of all cauliflower plants regardless of age at inoculation, with the pathogen ultimately appearing in the developing seed; however, colonization decreased with plant age. In broccoli, V. dahliae infected and colonized root and stem xylem tissues of plants inoculated at 1, 2, or 3 weeks postemergence. However, V. dahliae colonized only the root xylem and the epidermal and cortical tissues of broccoli plants inoculated at 4, 5, and 6 weeks postemergence. The frequency of reisolation of V. dahliae from the stems (4 to 22%) and roots (10 to 40%) of mature broccoli plants was lower than for cauliflower stems (25 to 64%) and roots (31 to 71%). The mean level of aliphatic glucosinolates in broccoli roots was 6.18 times higher than in the shoots and did not vary with age, whereas it was 3.65 times higher in cauliflower shoots than in the roots and there was a proportional increase with age. Indole glucosinolate content was identical in both cauliflower and broccoli, and both indole and aromatic glucosinolates did not vary with plant age in either crop. Qualitative differences in characterized glucosinolates were observed between broccoli and cauliflower but no differences were observed between inoculated and noninoculated plants for either broccoli or cauliflower. However, the phenolic and lignin contents were significantly higher in broccoli following inoculation than in noninoculated broccoli or inoculated cauliflower plants. The increased resistance of broccoli to V. dahliae infection was related to the increase in phenolic and lignin contents. Significant differential accumulation of glucosinolates associated with plant phenology may also contribute to the resistant and susceptible reactions of broccoli and cauliflower, respectively, against V. dahliae.

Piriformospora indica Stimulates Root Metabolism of Arabidopsis thaliana.

PubMed

Strehmel, Nadine; Mönchgesang, Susann; Herklotz, Siska; Krüger, Sylvia; Ziegler, Jörg; Scheel, Dierk

2016-07-08

Piriformospora indica is a root-colonizing fungus, which interacts with a variety of plants including Arabidopsis thaliana. This interaction has been considered as mutualistic leading to growth promotion of the host. So far, only indolic glucosinolates and phytohormones have been identified as key players. In a comprehensive non-targeted metabolite profiling study, we analyzed Arabidopsis thaliana's roots, root exudates, and leaves of inoculated and non-inoculated plants by ultra performance liquid chromatography/electrospray ionization quadrupole-time-of-flight mass spectrometry (UPLC/(ESI)-QTOFMS) and gas chromatography/electron ionization quadrupole mass spectrometry (GC/EI-QMS), and identified further biomarkers. Among them, the concentration of nucleosides, dipeptides, oligolignols, and glucosinolate degradation products was affected in the exudates. In the root profiles, nearly all metabolite levels increased upon co-cultivation, like carbohydrates, organic acids, amino acids, glucosinolates, oligolignols, and flavonoids. In the leaf profiles, we detected by far less significant changes. We only observed an increased concentration of organic acids, carbohydrates, ascorbate, glucosinolates and hydroxycinnamic acids, and a decreased concentration of nitrogen-rich amino acids in inoculated plants. These findings contribute to the understanding of symbiotic interactions between plant roots and fungi of the order of Sebacinales and are a valid source for follow-up mechanistic studies, because these symbioses are particular and clearly different from interactions of roots with mycorrhizal fungi or dark septate endophytes.

[Influence of arbuscular mycorrhizal inoculation on growth and phoxim residue of carrot (Daucus carota L.)].

PubMed

Wang, Fa-Yuan; Chen, Xin; Sun, Xian-Ming; Shi, Zhao-Yong

2010-12-01

A pot culture experiment was carried out to study the influence of arbuscular mycorrhizal (AM) fungi on the growth and phoxim residue of carrot (Daucus carota L). Four levels of phoxim (0, 200, 400, 800 mg x L(-1)) and two AM fungal inocula, Glomus intraradices BEG 141(141), Glomus mosseae BEG 167 (167),and one nonmycorrhizal inoculum (CK), were applied to the sterilized soil. The plants were harvested after 5 months of growth and phoxim was irrigated into the root zone 14 d before plant harvest. Although decreasing with the increase of phoxim dosage, root infection rates of all the mycorrhizal plants were higher than 70%. Phoxim showed no significant dose effect on shoot wet weights and root yields, which were all increased by AM inoculation at four phoxim dosages. Phoxim residues in shoots and roots increased with the increase of phoxim dosage, but decreased by AM inoculation. In general, Glomus intraradices BEG 141 showed more pronounced effects on the growth and phoxim residue of carrot than Glomus mosseae BEG 167 did. Our results show a promising potential of AM fungi in carrot production and controlling pesticide residues.

Interaction of rhizosphere bacteria, fertilizer, and vesicular-arbuscular mycorrhizal fungi with sea oats.

PubMed

Will, M E; Sylvia, D M

1990-07-01

Plants must be established quickly on replenished beaches in order to stabilize the sand and begin the dune-building process. The objective of this research was to determine whether inoculation of sea oats (Uniola paniculata L.) with bacteria (indigenous rhizosphere bacteria and N(2) fixers) alone or in combination with vesicular-arbuscular mycorrhizal fungi would enhance plant growth in beach sand. At two fertilizer-N levels, Klebsiella pneumoniae and two Azospirillum spp. did not provide the plants with fixed atmospheric N; however, K. pneumoniae increased root and shoot growth. When a sparingly soluble P source (CaHPO(4)) was added to two sands, K. pneumoniae increased plant growth in sand with a high P content. The phosphorus content of shoots was not affected by bacterial inoculation, indicating that a mechanism other than bacterially enhanced P availability to plants was responsible for the growth increases. When sea oats were inoculated with either K. pneumoniae or Acaligenes denitrificans and a mixed Glomus inoculum, there was no consistent evidence of a synergistic effect on plant growth. Nonetheless, bacterial inoculation increased root colonization by vesicular-arbuscular mycorrhizal fungi when the fungal inoculum consisted of colonized roots but had no effect on colonization when the inoculum consisted of spores alone. K. pneumoniae was found to increase spore germination and hyphal growth of Glomus deserticola compared with the control. The use of bacterial inoculants to enhance establishment of pioneer dune plants warrants further study.

Plant growth promoting capability and genetic diversity of bacteria isolated from mud volcano and lime cave of Andaman and Nicobar Islands

PubMed Central

Venkadesaperumal, Gopu; Amaresan, Natrajan; Kumar, Krishna

2014-01-01

Twenty four bacterial strains from four different regions of mud volcano and lime cave were isolated to estimate their diversity, plant growth promoting and biocontrol activities to use them as inoculant strains in the fields. An excellent antagonistic effect against four plant pathogens and plant growth promoting properties such as IAA production, HCN production, phosphate solubilization, siderophore production, starch hydrolysis and hydrolytic enzymes syntheses were identified in OM5 (Pantoea agglomerans) and EM9 (Exiguobacterium sp.) of 24 studied isolates. Seeds (Chili and tomato) inoculation with plant growth promoting strains resulted in increased percentage of seedling emergence, root length and plant weight. Results indicated that co-inoculation gave a more pronounced effects on seedling emergence, secondary root numbers, primary root length and stem length, while inoculation by alone isolate showed a lower effect. Our results suggest that the mixed inocula of OM5 and EM9 strains as biofertilizers could significantly increase the production of food crops in Andaman archipelago by means of sustainable and organic agricultural system. PMID:25763031

Plant growth promoting capability and genetic diversity of bacteria isolated from mud volcano and lime cave of Andaman and Nicobar Islands.

PubMed

Venkadesaperumal, Gopu; Amaresan, Natrajan; Kumar, Krishna

2014-01-01

Twenty four bacterial strains from four different regions of mud volcano and lime cave were isolated to estimate their diversity, plant growth promoting and biocontrol activities to use them as inoculant strains in the fields. An excellent antagonistic effect against four plant pathogens and plant growth promoting properties such as IAA production, HCN production, phosphate solubilization, siderophore production, starch hydrolysis and hydrolytic enzymes syntheses were identified in OM5 (Pantoea agglomerans) and EM9 (Exiguobacterium sp.) of 24 studied isolates. Seeds (Chili and tomato) inoculation with plant growth promoting strains resulted in increased percentage of seedling emergence, root length and plant weight. Results indicated that co-inoculation gave a more pronounced effects on seedling emergence, secondary root numbers, primary root length and stem length, while inoculation by alone isolate showed a lower effect. Our results suggest that the mixed inocula of OM5 and EM9 strains as biofertilizers could significantly increase the production of food crops in Andaman archipelago by means of sustainable and organic agricultural system.

Ectomycorrhizal inoculation with Pisolithus tinctorius reduces stress induced by drought in cork oak.

PubMed

Sebastiana, Mónica; da Silva, Anabela Bernardes; Matos, Ana Rita; Alcântara, André; Silvestre, Susana; Malhó, Rui

2018-04-01

We investigated whether the performance of cork oak under drought could be improved by colonization with the ectomycorrhizal fungus Pisolithus tinctorius. Results show that inoculation alone had a positive effect on plant height, shoot biomass, shoot basal diameter, and root growth. Under drought, root growth of mycorrhizal plants was significantly increased showing that inoculation was effective in increasing tolerance to drought. In accordance, mycorrhizal plants subjected to drought showed less symptoms of stress when compared to non-mycorrhizal plants, such as lower concentration of soluble sugars and starch, increased ability to maintain fatty acid content and composition, and increased unsaturation level of membrane lipids. After testing some of the mechanisms suggested to contribute to the enhanced tolerance of mycorrhizal plants to drought, we could not find any by which Pisolithus tinctorius could benefit cork oak, at least under the drought conditions imposed in our experiment. Inoculation did not increase photosynthesis under drought, suggesting no effect in sustaining stomatal opening at low soil water content. Similarly, plant water status was not affected by inoculation suggesting that P. tinctorius does not contribute to an increased plant water uptake during drought. Inoculation did increase nitrogen concentration in plants but it was independent of the water status. Furthermore, no significant mycorrhizal effect on drought-induced ROS production or osmotic adjustment was detected, suggesting that these factors are not important for the improved drought tolerance triggered by P. tinctorius.

Isolation and characterization of a plant growth-promoting rhizobacterium, Serratia sp. SY5.

PubMed

Koo, So-Yeon; Cho, Kyung-Suk

2009-11-01

The role of plant growth-promoting rhizobacteria (PGPR) in the phytoremediation of heavy-metal-contaminated soils is important in overcoming its limitations for field application. A plant growth-promoting rhizobacterium, Serratia sp. SY5, was isolated from the rhizoplane of barnyard grass (Echinochloa crus-galli) grown in petroleum and heavy-metal-contaminated soil. This isolate has shown capacities for indole acetic acid production and siderophores synthesis. Compared with a non-inoculated control, the radicular root growth of Zea mays seedlings inoculated with SY5 can be increased by 27- or 15.4-fold in the presence of 15 mg-Cd/l or 15 mg-Cu/l, respectively. The results from hydroponic cultures showed that inoculation of Serratia sp. SY5 had a favorable influence on the initial shoot growth and biomass of Zea mays under noncontaminated conditions. However, under Cd-contaminated conditions, the inoculation of SY5 significantly increased the root biomass of Zea mays. These results indicate that Serratia sp. SY5 can serve as a promising microbial inoculant for increased plant growth in heavy-metal-contaminated soils to improve the phytoremediation efficiency.

Copper-resistant bacteria enhance plant growth and copper phytoextraction.

PubMed

Yang, Renxiu; Luo, Chunling; Chen, Yahua; Wang, Guiping; Xu, Yue; Shen, Zhenguo

2013-01-01

In this study, we investigated the role of rhizospheric bacteria in solubilizing soil copper (Cu) and promoting plant growth. The Cu-resistant bacterium DGS6 was isolated from a natural Cu-contaminated soil and was identified as Pseudomonas sp. DGS6. This isolate solubilized Cu in Cu-contaminated soil and stimulated root elongation of maize and sunflower. Maize was more sensitive to inoculation with DGS6 than was sunflower and exhibited greater root elongation. In pot experiment, inoculation with DGS6 increased the shoot dry weight of maize by 49% and sunflower by 34%, and increased the root dry weight of maize by 85% and sunflower by 45%. Although the concentrations of Cu in inoculated and non-inoculated seedlings did not differ significantly, the total accumulation of Cu in the plants increased after inoculation. DGS6 showed a high ability to solubilize P and produce iron-chelating siderophores, as well as significantly improved the accumulation of P and Fe in both maize and sunflower shoots. In addition, DGS6 produced indole-3-acetic acid (IAA) and ACC deaminase, which suggests that it may modulate ethylene levels in plants. The bacterial strain DGS6 could be a good candidate for re-vegetation of Cu-contaminated sites. Supplemental materials are available for this article. Go to the publisher's online edition of International Journal of Phytoremediation to view the supplemental file.

Effect of mycorrhizal fungi on the phytoextraction of weathered p,p-DDE by Cucurbita pepo.

PubMed

White, Jason C; Ross, Daniel W; Gent, Martin P N; Eitzer, Brian D; Mattina, Maryjane Incorvia

2006-10-11

Field experiments were conducted to assess the impact of inoculation with mycorrhizal fungi on the accumulation of weathered p,p'-DDE from soil by three cultivars of zucchini (Cucurbita pepo spp. pepo cv Costata Romanesco, Goldrush, Raven). Three commercially available mycorrhizal products (BioVam, Myco-Vam, INVAM) were inoculated into the root system of the zucchini seedlings at planting. In agreement with our previous findings, plants not inoculated with fungi accumulated large but variable amounts of contaminant, with root bioconcentration factors (BCFs, ratio of p,p'-DDE, on a dry weight basis, in the root to that in the soil) ranging from 10 to 48 and stem BCFs ranging from 5.5 to 11. The total amount of contaminant phytoextracted during the 62 day growing season ranged from 0.72-2.9%. The effect of fungal inoculation on the release of weathered p,p'-DDE from soil and on the subsequent uptake of the parent compound by zucchini appeared to vary at the cultivar level. For Goldrush, fungal inoculation generally decreased tissue BCFs but because of slightly larger biomass, did not significantly impact the percent contaminant phytoextracted. Alternatively, for Costata, BioVam and Myco-Vam generally enhanced p,p'-DDE accumulation from soil, and increased the amount of contaminant phytoextracted by up to 34%. For Raven, BioVam reduced contaminant uptake whereas Myco-Vam and INVAM increased contaminant phytoextraction by 53 and 60%, respectively. The data show that fungal inoculation may significantly increase the remedial potential of C. pepo ssp. pepo. The apparent cultivar specific response to mycorrhizal inoculation is unexpected and the subject of ongoing investigation.

Suppression of the root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] on tomato by dual inoculation with arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria.

PubMed

Liu, Runjin; Dai, Mei; Wu, Xia; Li, Min; Liu, Xingzhong

2012-05-01

Arbuscular mycorrhizal (AM) fungi and plant growth-promoting rhizobacteria (PGPR) have potential for the biocontrol of soil-borne diseases. The objectives of this study were to quantify the interactions between AM fungi [Glomus versiforme (Karsten) Berch and Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe] and PGPR [Bacillus polymyxa (Prazmowski) Mace and Bacillus sp.] during colonization of roots and rhizosphere of tomato (Lycopersicon esculentum Mill) plants (cultivar Jinguan), and to determine their combined effects on the root-knot nematode, Meloidogyne incognita, and on tomato growth. Three greenhouse experiments were conducted. PGPR increased colonization of roots by AM fungi, and AM fungi increased numbers of PGPR in the rhizosphere. Dual inoculations of AM fungi plus PGPR provided greater control of M. incognita and greater promotion of plant growth than single inoculations, and the best combination was G. mosseae plus Bacillus sp. The results indicate that specific AM fungi and PGPR can stimulate each other and that specific combinations of AM fungi and PGPR can interact to suppress M. incognita and disease development. © Springer-Verlag 2012

Drought tolerance conferred to sugarcane by association with Gluconacetobacter diazotrophicus: a transcriptomic view of hormone pathways.

PubMed

Vargas, Lívia; Santa Brígida, Ailton B; Mota Filho, José P; de Carvalho, Thais G; Rojas, Cristian A; Vaneechoutte, Dries; Van Bel, Michiel; Farrinelli, Laurent; Ferreira, Paulo C G; Vandepoele, Klaas; Hemerly, Adriana S

2014-01-01

Sugarcane interacts with particular types of beneficial nitrogen-fixing bacteria that provide fixed-nitrogen and plant growth hormones to host plants, promoting an increase in plant biomass. Other benefits, as enhanced tolerance to abiotic stresses have been reported to some diazotrophs. Here we aim to study the effects of the association between the diazotroph Gluconacetobacter diazotrophicus PAL5 and sugarcane cv. SP70-1143 during water depletion by characterizing differential transcriptome profiles of sugarcane. RNA-seq libraries were generated from roots and shoots of sugarcane plants free of endophytes that were inoculated with G. diazotrophicus and subjected to water depletion for 3 days. A sugarcane reference transcriptome was constructed and used for the identification of differentially expressed transcripts. The differential profile of non-inoculated SP70-1143 suggests that it responds to water deficit stress by the activation of drought-responsive markers and hormone pathways, as ABA and Ethylene. qRT-PCR revealed that root samples had higher levels of G. diazotrophicus 3 days after water deficit, compared to roots of inoculated plants watered normally. With prolonged drought only inoculated plants survived, indicating that SP70-1143 plants colonized with G. diazotrophicus become more tolerant to drought stress than non-inoculated plants. Strengthening this hypothesis, several gene expression responses to drought were inactivated or regulated in an opposite manner, especially in roots, when plants were colonized by the bacteria. The data suggests that colonized roots would not be suffering from stress in the same way as non-inoculated plants. On the other hand, shoots specifically activate ABA-dependent signaling genes, which could act as key elements in the drought resistance conferred by G. diazotrophicus to SP70-1143. This work reports for the first time the involvement of G. diazotrophicus in the promotion of drought-tolerance to sugarcane cv. SP70-1143, and it describes the initial molecular events that may trigger the increased drought tolerance in the host plant.

Drought Tolerance Conferred to Sugarcane by Association with Gluconacetobacter diazotrophicus: A Transcriptomic View of Hormone Pathways

PubMed Central

Vargas, Lívia; Santa Brígida, Ailton B.; Mota Filho, José P.; de Carvalho, Thais G.; Rojas, Cristian A.; Vaneechoutte, Dries; Van Bel, Michiel; Farrinelli, Laurent; Ferreira, Paulo C. G.; Vandepoele, Klaas; Hemerly, Adriana S.

2014-01-01

Sugarcane interacts with particular types of beneficial nitrogen-fixing bacteria that provide fixed-nitrogen and plant growth hormones to host plants, promoting an increase in plant biomass. Other benefits, as enhanced tolerance to abiotic stresses have been reported to some diazotrophs. Here we aim to study the effects of the association between the diazotroph Gluconacetobacter diazotrophicus PAL5 and sugarcane cv. SP70-1143 during water depletion by characterizing differential transcriptome profiles of sugarcane. RNA-seq libraries were generated from roots and shoots of sugarcane plants free of endophytes that were inoculated with G. diazotrophicus and subjected to water depletion for 3 days. A sugarcane reference transcriptome was constructed and used for the identification of differentially expressed transcripts. The differential profile of non-inoculated SP70-1143 suggests that it responds to water deficit stress by the activation of drought-responsive markers and hormone pathways, as ABA and Ethylene. qRT-PCR revealed that root samples had higher levels of G. diazotrophicus 3 days after water deficit, compared to roots of inoculated plants watered normally. With prolonged drought only inoculated plants survived, indicating that SP70-1143 plants colonized with G. diazotrophicus become more tolerant to drought stress than non-inoculated plants. Strengthening this hypothesis, several gene expression responses to drought were inactivated or regulated in an opposite manner, especially in roots, when plants were colonized by the bacteria. The data suggests that colonized roots would not be suffering from stress in the same way as non-inoculated plants. On the other hand, shoots specifically activate ABA-dependent signaling genes, which could act as key elements in the drought resistance conferred by G. diazotrophicus to SP70-1143. This work reports for the first time the involvement of G. diazotrophicus in the promotion of drought-tolerance to sugarcane cv. SP70-1143, and it describes the initial molecular events that may trigger the increased drought tolerance in the host plant. PMID:25489849

Contribution of the saprobic fungi Trametes versicolor and Trichoderma harzianum and the arbuscular mycorrhizal fungi Glomus deserticola and G. claroideum to arsenic tolerance of Eucalyptus globulus.

PubMed

Arriagada, C; Aranda, E; Sampedro, I; Garcia-Romera, I; Ocampo, J A

2009-12-01

The presence of high concentrations of arsenic (As) decreased the shoot and root dry weight, chlorophyll and P and Mg content of Eucalyptus globulus colonized with the arbuscular mycorrhizal (AM) fungi Glomus deserticola or G. claroideum, but these parameters were higher than in non-AM plants. As increased the percentage of AM length colonization and succinate dehydrogenase (SDH) activity in the root of E. globulus. Trichoderma harzianum, but not Trametes versicolor, increased the shoot and root dry weight, chlorophyll content, the percentage of AM root length colonization and SDH activity of E. globulus in presence of all As concentrations applied to soil when was inoculated together with G. claroideum. AM fungi increased shoot As and P concentration of E. globulus to higher level than the non-AM inoculated controls. The contribution of the AM and saprobe fungi to the translocation of As from root to shoot of E. globulus is discussed.

Endogenous rhythmic growth in oak trees is regulated by internal clocks rather than resource availability

PubMed Central

Herrmann, S.; Recht, S.; Boenn, M.; Feldhahn, L.; Angay, O.; Fleischmann, F.; Tarkka, M T.; Grams, T.E.E.; Buscot, F.

2015-01-01

Common oak trees display endogenous rhythmic growth with alternating shoot and root flushes. To explore the mechanisms involved, microcuttings of the Quercus robur L. clone DF159 were used for 13C/15N labelling in combination with RNA sequencing (RNASeq) transcript profiling of shoots and roots. The effect of plant internal resource availability on the rhythmic growth of the cuttings was tested through inoculation with the ectomycorrhizal fungus Piloderma croceum. Shoot and root flushes were related to parallel shifts in above- and below-ground C and, to a lesser extent, N allocation. Increased plant internal resource availability by P. croceum inoculation with enhanced plant growth affected neither the rhythmic growth nor the associated resource allocation patterns. Two shifts in transcript abundance were identified during root and shoot growth cessation, and most concerned genes were down-regulated. Inoculation with P. croceum suppressed these transcript shifts in roots, but not in shoots. To identify core processes governing the rhythmic growth, functions [Gene Ontology (GO) terms] of the genes differentially expressed during the growth cessation in both leaves and roots of non-inoculated plants and leaves of P. croceum-inoculated plants were examined. Besides genes related to resource acquisition and cell development, which might reflect rather than trigger rhythmic growth, genes involved in signalling and/or regulated by the circadian clock were identified. The results indicate that rhythmic growth involves dramatic oscillations in plant metabolism and gene regulation between below- and above-ground parts. Ectomycorrhizal symbiosis may play a previously unsuspected role in smoothing these oscillations without modifying the rhythmic growth pattern. PMID:26320242

Effect of arbuscular mycorrhizal fungi on trace metal uptake by sunflower plants grown on cadmium contaminated soil.

PubMed

Hassan, Saad Eldin; Hijri, Mohamed; St-Arnaud, Marc

2013-09-25

Trace metal (TM) pollution of soil is a worldwide problem that threatens the quality of human and environmental health. Phytoremediation using plants and their associated microbes has been increasingly used as a green technology for cleaning up TM-polluted soils. In this study, we investigated the effect of inoculating two arbuscular mycorrhizal fungal isolates, Rhizophagus irregularis and Funneliformis mosseae, on trace metal uptake by sunflower plants grown in soils contaminated with three different Cd concentrations in a greenhouse trial. Root colonization, plant dry mass, and plant tissue cadmium (Cd), zinc (Zn), and copper (Cu) concentrations in roots and shoots were determined after sunflower harvesting. We found that root mycorrhizal colonization rates were not significantly affected by Cd treatments. At low soil Cd concentration, R. irregularis-inoculated plants had significantly higher shoot Cd and Zn concentrations than plants inoculated with F. mosseae and non-inoculated plants. However, at high soil Cd concentrations, F. mosseae-inoculated plants had significantly lower shoot Cd and Zn concentrations and biological concentration factor (BCF) values than plants inoculated with R. irregularis and non-inoculated plants. Cadmium was mainly translocated in shoot tissues of R. irregularis-inoculated plants and sequestered in the rhizosphere of F. mosseae-inoculated plants. The results indicate that these AMF strains mediate different tolerance strategies to alleviate TM toxicity in their host plants and that inoculation with the R. irregularis strain can be used for Cd phytoextraction, whereas this F. mosseae strain can be useful for Cd and Zn phytostabilization of contaminated soil. Copyright © 2013 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jawdy, Sara S.; Gunter, Lee E.; Engle, Nancy L.

Here, the biological function of the plant-microbiome system is the result of contributions from the host plant and microbiome members. In this work we study the function of a simplified community consisting of Pseudomonas and Burkholderia bacterial strains isolated from Populus hosts and inoculated on axenic Populus cutting in controlled laboratory conditions. Inoculation individually with either bacterial isolate increased root growth relative to uninoculated controls. Root area, photosynthetic efficiency, gene expression and metabolite expression data in individual and dual inoculated treatments indicate that the effects of these bacteria are unique and additive, suggesting that the function of a microbiome communitymore » may be predicted from the additive functions of the individual members.« less

Does mycorrhizal inoculation improve plant survival, aggregate stability, and fine root development on a coarse-grained soil in an alpine eco-engineering field experiment?

NASA Astrophysics Data System (ADS)

Bast, A.; Wilcke, W.; Graf, F.; Lüscher, P.; Gärtner, H.

2016-08-01

Steep vegetation-free talus slopes in high mountain environments are prone to superficial slope failures and surface erosion. Eco-engineering measures can reduce slope instabilities and thus contribute to risk mitigation. In a field experiment, we established mycorrhizal and nonmycorrhizal research plots and determined their biophysical contribution to small-scale soil fixation. Mycorrhizal inoculation impact on plant survival, aggregate stability, and fine root development was analyzed. Here we present plant survival (ntotal = 1248) and soil core (ntotal = 108) analyses of three consecutive years in the Swiss Alps. Soil cores were assayed for their aggregate stability coefficient (ASC), root length density (RLD), and mean root diameter (MRD). Inoculation improved plant survival significantly, but it delayed aggregate stabilization relative to the noninoculated site. Higher aggregate stability occurred only after three growing seasons. Then also RLD tended to be higher and MRD increased significantly at the mycorrhizal treated site. There was a positive correlation between RLD, ASC, and roots <0.5 mm, which had the strongest impact on soil aggregation. Our results revealed a temporal offset between inoculation effects tested in laboratory and field experiments. Consequently, we recommend to establish an intermediate to long-term field experimental monitoring before transferring laboratory results to the field.

Fungal inoculation and elevated CO2 mediate growth of Lolium mutiforum and Phytolacca americana, metal uptake, and metal bioavailability in metal-contaminated soil: evidence from DGT measurement.

PubMed

Song, Ningning; Wang, Fangli; Zhang, Changbo; Tang, Shirong; Guo, Junkang; Ju, Xuehai; Smith, Donald L

2013-01-01

Fungal inoculation and elevated CO2 may mediate plant growth and uptake of heavy metals, but little evidence from Diffusive Gradients in Thin-films (DGT) measurement has been obtained to characterize the process. Lolium mutiforum and Phytolacca americana were grown at ambient and elevated CO2 on naturally Cd and Pb contaminated soils inoculated with and without Trichoderma asperellum strain C3 or Penicillium chrysogenum strain D4, to investigate plant growth, metal uptake, and metal bioavailability responses. Fungal inoculation increased plant biomass and shoot/root Cd and Pb concentrations. Elevated CO2 significantly increased plants biomass, but decreased Cd and Pb concentrations in shoot/root to various extents, leading to a metal dilution phenomenon. Total Cd and Pb uptake by plants, and DGT-measured Cd and Pb concentrations in rhizosphere soils, were higher in all fungal inoculation and elevated CO2 treatments than control treatments, with the combined treatments having more influence than either treatment alone. Metal dilution phenomenon occurred because the increase in DGT-measured bioavailable metal pools in plant rhizosphere due to elevated CO2 was unable to match the increase in requirement for plant uptake of metals due to plant biomass increase.

Antioxidant activity and induction of mechanisms of resistance to stresses related to the inoculation with Azospirillum brasilense.

PubMed

Fukami, Josiane; Ollero, Francisco Javier; de la Osa, Clara; Valderrama-Fernández, Rocio; Nogueira, Marco Antonio; Megías, Manuel; Hungria, Mariangela

2018-06-07

We investigated the effects of Azospirillum brasilense strains Ab-V5 and Ab-V6 in the induction of mechanisms of systemic acquired resistance (SAR) and induced system resistance (ISR) on maize (Zea mays L.) plants. Under normal growth conditions, the treatments consisted of the standard inoculation of cells at sowing, and leaf spray of cells or their metabolites at the V2.5 growth stage; under saline stress (170 mM NaCl), the treatment consisted of standard single and co-inoculation of A. brasilense and Rhizobium tropici. The main compounds in the Azospirillum metabolites were identified as indole-3-acetic acid (IAA) and salicylic acid (SA). Under normal conditions, A. brasilense cells applied at sowing or by leaf spray increased the activities of catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) in leaves, and of ascorbate peroxidase (APX) in roots; however, interestingly, in general the highest activities were observed by leaf spray of metabolites. Under normal conditions, the highest levels of salicylic acid (SA) and jasmonic acid (JA) were achieved in leaves by leaf spray of metabolites, of SA in roots by leaf spray of cells, and of JA in roots by standard inoculation and leaf spray of metabolites. Under saline stress, plant protection occurred via SA and abscisic acid (ABA), but not JA. In general, inoculation resulted in further increases in SA in leaves and roots, and ABA in leaves. We hypothesize that A. brasilense confers protection to maize plants by simultaneous induction of JA and SA pathways, and, under saline stressing conditions, by SA and ABA pathways.

Piriformospora indica inoculation alleviates the adverse effect of NaCl stress on growth, gas exchange and chlorophyll fluorescence in tomato (Solanum lycopersicum L.).

PubMed

Ghorbani, A; Razavi, S M; Ghasemi Omran, V O; Pirdashti, H

2018-03-25

Salinity is now an increasingly serious environmental issue that affects the growth and yield of many plants. In the present work, the influence of inoculation with the symbiotic fungus, Piriformospora indica, on gas exchange, water potential, osmolyte content, Na/K ratio and chlorophyll fluorescence of tomato plants under three salinity levels (0, 50, 100 and 150 mm NaCl) and three time periods (5, 10 and 15 days after exposure to salt) was investigated. Results indicate that P. indica inoculation improved growth parameters of tomato under salinity stress. This symbiotic fungus significantly increased photosynthetic pigment content under salinity, and more proline and glycine betaine accumulated in inoculated roots than in non-inoculated roots. P. indica further significantly improved K + content and reduced Na + level under salinity treatment. After inoculation with the endophytic fungus, leaf physiological parameters, such as water potential, net photosynthesis, stomatal conductance and transpiration, were all higher under the salt concentrations and durations compared with controls without P. indica. With increasing salt level and salt treatment duration, values of F 0 and qP increased but F m , F v /F m , F' v /F' m and NPQ declined in the controls, while inoculation with P. indica improved these values. The results indicate that the negative effects of NaCl on tomato plants were alleviated after P. indica inoculation, probably by improving physiological parameters such as water status and photosynthesis. © 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Interactions of Trametes versicolor, Coriolopsis rigida and the arbuscular mycorrhizal fungus Glomus deserticola on the copper tolerance of Eucalyptus globulus.

PubMed

Arriagada, C; Aranda, E; Sampedro, I; Garcia-Romera, I; Ocampo, J A

2009-09-01

The presence of high levels of Cu in soil decreases the shoot and root dry weights of Eucalyptus globulus. However, higher plant tolerance of Cu has been observed in the presence of the arbuscular mycorrhizal (AM) fungus Glomus deserticola. The hyphal length of G. deserticola was sensitive to low Cu concentrations, and the percentage of AM root colonisation and the metabolic activity of the AM fungus were also decreased by Cu. Therefore, a direct effect of Cu on the development of the AM fungus inside and outside the root cannot be ruled out. E. globulus colonised by G. deserticola had higher metal concentrations in the roots and shoots than do non-mycorrhizal plants; however, the absence of a higher root to shoot metal ratio in the mycorrhizal plants (1.70+/-0.11) indicated that G. deserticola did not play a filtering/sequestering role against Cu. The saprobe fungi Coriolopsis rigida and Trametes versicolor were able to remove Cu ions from the asparagine-glucose growth media. However, plants inoculated with C. rigida and T. versicolor did not accumulate more Cu than non-inoculated controls, and the growth of the plant was not increased in the presence of these fungi. However, C. rigida increased the shoot dry weight, AM root length colonisation, and metabolic mycelial activity of plants colonised with G. deserticola in the presence of Cu; only this saprobe-AM fungus combination increased the tolerance of E. globulus to Cu. Inoculation with G. deserticola and C. rigida increased the E. globulus Cu uptake to levels reached by hyperaccumulative plants.

Does mycorrhizal inoculation benefit plant survival, plant development and small-scale soil fixation? Results from a perennial eco-engineering field experiment in the Swiss Alps.

NASA Astrophysics Data System (ADS)

Bast, Alexander; Grimm, Maria; Graf, Frank; Baumhauer, Roland; Gärtner, Holger

2015-04-01

In mountain environments superficial slope failures on coarse grained, vegetation-free slopes are common processes and entail a certain risk for humans and socio-economic structures. Eco-engineering measures can be applied to mitigate slope instabilities. In this regard, limited plant survival and growth can be supported by mycorrhizal inoculation, which was successfully tested in laboratory studies. However, related studies on a field scale are lacking. Furthermore, mycorrhizae are known to enhance soil aggregation, which is linked to soil physics such as shear strength, and hence it is a useful indicator for near-surface soil/slope stability. The overall objective of our contribution was to test whether mycorrhizal inoculation can be used to promote eco-engineering measures in steep alpine environments based on a five-year field experiment. We hypothesized that mycorrhizal inoculation (i) enhances soil aggregation, (ii) stimulate plant survival and fine root development, (iii) effects plant performance, (iv) the stimulated root development in turn influences aggregate stability, and (v) that climatic variations play a major role in fine-root development. We established mycorrhizal and non-mycorrhizal treated eco-engineered research plots (hedge layers mainly consisting of Alnus spp. and Salix spp.) on a field experimental scale. The experimental site is in the eastern Swiss Alps at an erosion-prone slope where many environmental conditions can be seen as homogeneous. Soil aggregation, fine root development and plant survival was quantified at the end of four growing seasons (2010, '11, '12, '14). Additionally, growth properties of Alnus spp. and Salix spp. were measured and their biomass estimated. Meteorological conditions, soil temperature and soil water content were recorded. (i) The introduced eco-engineering measures enhanced aggregate stability significantly. In contrast to published greenhouse and laboratory studies, mycorrhizal inoculation delayed soil aggregate stabilization relative to the non-inoculated site but resulted in a significantly higher aggregate stability compared to the control and the non-inoculated site at the end of the third growing season. (ii) Plant survival was significantly improved by the inoculation. Fine-root development was stimulated but not immediately. At the end of the third growing season, root length density tended to be higher and mean root diameter was significantly increased at the mycorrhizal treated site. (iii) Analyses on plant performance of Alnus and Salix demonstrated that the inoculated saplings achieved significantly higher survival rates. There was no treatment effect on plant growth properties except in 2010, where plant height and main stem diameter of Alnus was increased at the mycorrhizal treated site. The estimated total biomass of Alnus and Salix was higher at the mycorrhizal treated site. (iv) There was a positive correlation between root length density and aggregate stability, whereas roots < 0.5 mm were most influential on aggregate stability. (v) Interannual climatic variations seem to have a crucial influence on root development and, hence, on slope stability. There is a temporal offset of two growing seasons between inoculation effects tested in greenhouse/laboratory and the presented field experiment. However, the application of a commercial mycorrhizal inoculum in eco-engineering measures is a beneficial promoter to mitigate slope instability and surface erosion but needs to be tested at other sites. The contribution is mainly based on Bast (2014) and was funded by the Wolfermann Nägeli Stiftung Zürich and the Swiss Federal Office for Environment (BAFU No.: 09.0027.PJ/I211-3446). Bast, A. (2014): Mycorrhizal inoculation as a promoter for sustainable eco-engineering measures in steep alpine environments? Results of a three-year field experiment in the Arieschbach catchment, Fideris, eastern Swiss Alps. PhD Thesis. University of Berne: 149pp.

Assessing the efficacy of co-inoculation of wheat seedlings with the associative bacteria Paenibacillus polymyxa 1465 and Azospirillum brasilense Sp245.

PubMed

Yegorenkova, Irina V; Tregubova, Kristina V; Burygin, Gennady L; Matora, Larisa Y; Ignatov, Vladimir V

2016-03-01

Co-inoculation of associative bacteria, which have high nitrogen-fixing activity, tolerance for environmental conditions, and the ability to compete with the natural microflora, is used widely to enhance the growth and yields of agricultural plants. We evaluated the ability of 2 co-inoculated plant-growth-promoting rhizobacteria, Paenibacillus polymyxa 1465 and Azospirillum brasilense Sp245, to colonize roots of wheat (Triticum aestivum L. 'Saratovskaya 29') seedlings, and we assessed the morphometric parameters of wheat early in its development. Analysis by ELISA with polyclonal antibodies raised against the exopolysaccharide of P. polymyxa 1465 and the lipopolysaccharide of A. brasilense Sp245 demonstrated that the root-colonizing activity of A. brasilense was higher when the bacterium was co-inoculated with P. polymyxa than when it was inoculated singly. Immunofluorescence microscopy with Alexa Fluor 532-labeled antibodies revealed sites of attachment of co-inoculated P. polymyxa and A. brasilense and showed that the 2 bacteria colonized similar regions of the roots. Co-inoculation exerted a negative effect on wheat seedling development, inhibiting root length by 17.6%, total root weight by 11%, and total shoot weight by 12%. Under certain conditions, dual inoculation of wheat may prove ineffective, apparently owing to the competition between the rhizobacteria for colonization sites on the plant roots. The findings from this study may aid in developing techniques for mixed bacterial inoculation of cultivated plants.

Increased growth and root Cu accumulation of Sorghum sudanense by endophytic Enterobacter sp. K3-2: Implications for Sorghum sudanense biomass production and phytostabilization.

PubMed

Li, Ya; Wang, Qi; Wang, Lu; He, Lin-Yan; Sheng, Xia-Fang

2016-02-01

Endophytic bacterial strain K3-2 was isolated from the roots of Sorghum sudanense (an bioenergy plant) grown in a Cu mine wasteland soils and characterized. Strain K3-2 was identified as Enterobacter sp. based on 16S rRNA gene sequence analysis. Strain K3-2 exhibited Cu resistance and produced 1-aminocyclopropane-1-carboxylate (ACC) deaminase, indole-3-acetic acid (IAA), siderophores, and arginine decarboxylase. Pot experiments showed that strain K3-2 significantly increased the dry weight and root Cu accumulation of Sorghum sudanense grown in the Cu mine wasteland soils. Furthermore, increase in total Cu uptake (ranging from 49% to 95%) of the bacterial inoculated-Sorghum sudanense was observed compared to the control. Notably, most of Cu (83-86%) was accumulated in the roots of Sorghum sudanense. Furthermore, inoculation with strain K3-2 was found to significantly increase Cu bioconcentration factors and the proportions of IAA- and siderophore-producing bacteria in the root interiors and rhizosphere soils of Sorghum sudanense compared with the control. Significant decrease in the available Cu content was also observed in the rhizosphere soils of the bacterial-inoculated Sorghum sudanense. The results suggest that the endophytic bacterial strain K3-2 may be exploited for promoting Sorghum sudanense biomass production and Cu phytostabilization in the Cu mining wasteland soils. Copyright © 2015 Elsevier Inc. All rights reserved.

Systemic and local regulation of phosphate and nitrogen transporter genes by arbuscular mycorrhizal fungi in roots of winter wheat (Triticum aestivum L.).

PubMed

Duan, Jianfeng; Tian, Hui; Drijber, Rhae A; Gao, Yajun

2015-11-01

Previous studies have reported that the expression of phosphate (Pi) or nitrogen (N) transporter genes in roots of plants could be regulated by arbuscular mycorrhizal (AM) fungi, but little is known whether the regulation is systemic or not. The present study investigated the systemic and local regulation of multiple phosphate and nitrogen transporter genes by four AM fungal species belonging to four genera in the roots of winter wheat. A split-root culture system with AM inoculated (MR) and non-inoculated root compartments (NR) was used to investigate the systemic or local responses of phosphate and nitrogen transporter genes to colonization by four AM fungi in the roots of wheat. The expression of four Pi transporter, five nitrate transporter, and three ammonium transporter genes was quantified using real-time PCR. Of the four AM fungi tested, all locally increased expression of the AM-inducible Pi transporter genes, and most locally decreased expression of a Pi-starvation inducible Pi transporter gene. The addition of N in soil increased the expression of either Pi starvation inducible Pi transporters or AM inducible Pi transporters. Inoculation with AM fungi either had no effect, or could locally or systemically down-regulate expression of nitrogen transporter genes depending on gene type and AM fungal species. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Consequences of inoculation with native arbuscular mycorrhizal fungi for root colonization and survival of Artemisia tridentata ssp. wyomingensis seedlings after transplanting.

PubMed

Davidson, Bill E; Novak, Stephen J; Serpe, Marcelo D

2016-08-01

In arid environments, the propagule density of arbuscular mycorrhizal fungi (AMF) may limit the extent of the plant-AMF symbiosis. Inoculation of seedlings with AMF could alleviate this problem, but the success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These phenomena were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings inoculated with native AMF. Seedlings were first grown in a greenhouse in soil without AMF (non-inoculated seedlings) or with AMF (inoculated seedlings). In spring and fall, 3-month-old seedlings were transplanted outdoors to 24-L pots containing soil from a sagebrush habitat (spring and fall mesocosm experiments) or to a recently burned sagebrush habitat (spring and fall field experiments). Five or 8 months after transplanting, colonization was about twofold higher in inoculated than non-inoculated seedlings, except for the spring field experiment. In the mesocosm experiments, inoculation increased survival during the summer by 24 % (p = 0.011). In the field experiments, increased AMF colonization was associated with increases in survival during cold and dry periods; 1 year after transplanting, survival of inoculated seedlings was 27 % higher than that of non-inoculated ones (p < 0.001). To investigate possible mechanisms by which AMF increased survival, we analyzed water use efficiency (WUE) based on foliar (13)C/(12)C isotope ratios (δ (13)C). A positive correlation between AMF colonization and δ (13)C values was observed in the spring mesocosm experiment. In contrast, inoculation did not affect the δ (13)C values of fall transplanted seedlings that were collected the subsequent spring. The effectiveness of AMF inoculation on enhancing colonization and reducing seedling mortality varied among the different experiments, but average effects were estimated by meta-analyses. Several months after transplanting, average AMF colonization was in proportion 84 % higher in inoculated than non-inoculated seedlings (p = 0.0042), while the average risk of seedling mortality was 42 % lower in inoculated than non-inoculated seedlings (p = 0.047). These results indicate that inoculation can increase AMF colonization over the background levels occurring in the soil, leading to higher rates of survival.

Entomopathogenic fungi-based mechanisms for improved Fe nutrition in sorghum plants grown on calcareous substrates.

PubMed

Raya-Díaz, Silvia; Sánchez-Rodríguez, Antonio Rafael; Segura-Fernández, José Manuel; Del Campillo, María Del Carmen; Quesada-Moraga, Enrique

2017-01-01

Although entomopathogenic fungi (EPF) are best known for their ability to protect crops against insect pests, they may have other beneficial effects on their host plants. These effects, which include promoting plant growth and conferring resistance against abiotic stresses, have been examined in recent years to acquire a better understanding of them. The primary purposes of the present study were (i) to ascertain in vitro whether three different strains of EPF (viz., Metarhizium, Beauveria and Isaria) would increase the Fe bioavailability in calcareous or non-calcareous media containing various Fe sources (ferrihydrite, hematite and goethite) and (ii) to assess the influence of the EPF inoculation method (seed dressing, soil treatment or leaf spraying) on the extent of the endophytic colonization of sorghum and the improvement in the Fe nutrition of pot-grown sorghum plants on an artificial calcareous substrate. All the EPFs studied were found to increase the Fe availability during the in vitro assay. The most efficient EPF was M. brunneum EAMa 01/58-Su, which lowered the pH of the calcareous medium, suggesting that it used a different strategy (organic acid release) than the other two fungi that raised the pH of the non-calcareous medium. The three methods used to inoculate sorghum plants with B. bassiana and M. brunneum in the pot experiment led to differences in re-isolation from plant tissues and in the plant height. These three inoculation methods increased the leaf chlorophyll content of young leaves when the Fe deficiency symptoms were most apparent in the control plants (without fungal inoculation) as well as the Fe content of the above-ground biomass in the plants at the end of the experiment. The total root lengths and fine roots were also increased in response to fungal applications with the three inoculation methods. However, the soil treatment was the most efficient method; thus, its effect on the leaf chlorophyll content was the most persistent, and the effects on the total root length and fine roots were the most apparent. In conclusion, EPF improved the Fe nutrition of the sorghum plants, but their effects depended on the inoculation method.

Entomopathogenic fungi-based mechanisms for improved Fe nutrition in sorghum plants grown on calcareous substrates

PubMed Central

Raya-Díaz, Silvia; Segura-Fernández, José Manuel; del Campillo, María del Carmen; Quesada-Moraga, Enrique

2017-01-01

Although entomopathogenic fungi (EPF) are best known for their ability to protect crops against insect pests, they may have other beneficial effects on their host plants. These effects, which include promoting plant growth and conferring resistance against abiotic stresses, have been examined in recent years to acquire a better understanding of them. The primary purposes of the present study were (i) to ascertain in vitro whether three different strains of EPF (viz., Metarhizium, Beauveria and Isaria) would increase the Fe bioavailability in calcareous or non-calcareous media containing various Fe sources (ferrihydrite, hematite and goethite) and (ii) to assess the influence of the EPF inoculation method (seed dressing, soil treatment or leaf spraying) on the extent of the endophytic colonization of sorghum and the improvement in the Fe nutrition of pot-grown sorghum plants on an artificial calcareous substrate. All the EPFs studied were found to increase the Fe availability during the in vitro assay. The most efficient EPF was M. brunneum EAMa 01/58–Su, which lowered the pH of the calcareous medium, suggesting that it used a different strategy (organic acid release) than the other two fungi that raised the pH of the non-calcareous medium. The three methods used to inoculate sorghum plants with B. bassiana and M. brunneum in the pot experiment led to differences in re-isolation from plant tissues and in the plant height. These three inoculation methods increased the leaf chlorophyll content of young leaves when the Fe deficiency symptoms were most apparent in the control plants (without fungal inoculation) as well as the Fe content of the above-ground biomass in the plants at the end of the experiment. The total root lengths and fine roots were also increased in response to fungal applications with the three inoculation methods. However, the soil treatment was the most efficient method; thus, its effect on the leaf chlorophyll content was the most persistent, and the effects on the total root length and fine roots were the most apparent. In conclusion, EPF improved the Fe nutrition of the sorghum plants, but their effects depended on the inoculation method. PMID:28982140

Combined Inoculation with Multiple Arbuscular Mycorrhizal Fungi Improves Growth, Nutrient Uptake and Photosynthesis in Cucumber Seedlings.

PubMed

Chen, Shuangchen; Zhao, Hongjiao; Zou, Chenchen; Li, Yongsheng; Chen, Yifei; Wang, Zhonghong; Jiang, Yan; Liu, Airong; Zhao, Puyan; Wang, Mengmeng; Ahammed, Golam J

2017-01-01

Mycorrhizal inoculation stimulates growth, photosynthesis and nutrient uptake in a wide range of host plants. However, the ultimate effects of arbuscular mycorrhyzal (AM) symbiosis vary with the plants and fungal species involved in the association. Therefore, identification of the appropriate combinations of AM fungi (AMF) that interact synergistically to improve their benefits is of high significance. Here, three AM fungal compositions namely VT ( Claroideoglomus sp., Funneliformis sp., Diversispora sp., Glomus sp., and Rhizophagus sp.) and BF ( Glomus intraradices , G. microageregatum BEG and G. Claroideum BEG 210), and Funneliformis mosseae (Fm) were investigated with respect to the growth, gas exchange parameters, enzymes activities in Calvin cycles and related gene expression in cucumber seedlings. The results showed that VT, BF and Fm could successfully colonize cucumber root to a different degree with the colonization rates 82.38, 74.65, and 70.32% at 46 days post inoculation, respectively. The plant height, stem diameter, dry weight, root to shoot ratio of cucumber seedlings inoculated with AMF increased significantly compared with the non-inoculated control. Moreover, AMF colonization greatly increased the root activity, chlorophyll content, net photosynthetic rate, light saturated rate of the CO 2 assimilation ( A sat), maximum carboxylation rate ( V cmax ) and maximum ribulose-1,5-bis-phosphate (RuBP) regeneration rate ( J max), which were increased by 52.81, 30.75, 58.76, 47.00, 69.15, and 65.53% when inoculated with VT, respectively. The activities of some key enzymes such RuBP carboxylase/oxygenase (RuBisCO), D-fructose-1,6-bisphosphatase (FBPase), D-fructose-6-phosphatase (F6P) and ribulose-5-phosphate kinase (Ru5PK), and related gene expression involved in the Calvin cycle including RCA , FBPase , FBPA , SBPase , rbcS and rbcL were upregulated by AMF colonization. AMF inoculation also improved macro- and micro nutrient contents such as N, P, K, S, Ca, Cu, Fe, Mn, Mg, and Zn in roots. Further analysis revealed that inoculation with VT had relatively better effect on growth of cucumber seedling followed by BF and Fm, indicating that AMF composition consisting of distant AMF species may have a better effect than a single or closely related AMF spp. This study advances the understanding of plant responses to different AM fungi toward development of strategies on AMF-promoted vegetable production.

Effect of applying an arsenic-resistant and plant growth-promoting rhizobacterium to enhance soil arsenic phytoremediation by Populus deltoides LH05-17.

PubMed

Wang, Q; Xiong, D; Zhao, P; Yu, X; Tu, B; Wang, G

2011-11-01

Bioremediation of highly arsenic (As)-contaminated soil is difficult because As is very toxic for plants and micro-organisms. The aim of this study was to investigate soil arsenic removal effects using poplar in combination with the inoculation of a plant growth-promoting rhizobacterium (PGPR). A rhizobacterium D14 was isolated and identified within Agrobacterium radiobacter. This strain was highly resistant to arsenic and produced indole acetic acid and siderophore. Greenhouse pot bioremediation experiments were performed for 5 months using poplar (Populus deltoides LH05-17) grown on As-amended soils, inoculated with strain D14. The results showed that P. deltoides was an efficient arsenic accumulator; however, high As concentrations (150 and 300 mg kg(-1)) inhibited its growth. With the bacterial inoculation, in the 300 mg kg(-1) As-amended soils, 54% As in the soil was removed, which was higher than the uninoculated treatments (43%), and As concentrations in roots, stems and leaves were significantly increased by 229, 113 and 291%, respectively. In addition, the As translocation ratio [(stems + leaves)/roots = 0·8] was significantly higher than the uninoculated treatments (0·5). About 45% As was translocated from roots to the above-ground tissues. The plant height and dry weight of roots, stems and leaves were all enhanced; the contents of chlorophyll and soluble sugar, and the activities of superoxide dismutase and catalase were all increased; and the content of a toxic compound malondialdehyde was decreased. The results indicated that the inoculation of strain D14 could contribute to the increase in the As tolerance of P. deltoides, promotion of the growth, increase in the uptake efficiency and enhancement of As translocation. The use of P. deltoides in combination with the inoculation of strain D14 provides a potential application for efficient soil arsenic bioremediation. © 2011 The Authors. Journal of Applied Microbiology ©2011 The Society for Applied Microbiology.

Endogenous rhythmic growth in oak trees is regulated by internal clocks rather than resource availability.

PubMed

Herrmann, S; Recht, S; Boenn, M; Feldhahn, L; Angay, O; Fleischmann, F; Tarkka, M T; Grams, T E E; Buscot, F

2015-12-01

Common oak trees display endogenous rhythmic growth with alternating shoot and root flushes. To explore the mechanisms involved, microcuttings of the Quercus robur L. clone DF159 were used for (13)C/(15)N labelling in combination with RNA sequencing (RNASeq) transcript profiling of shoots and roots. The effect of plant internal resource availability on the rhythmic growth of the cuttings was tested through inoculation with the ectomycorrhizal fungus Piloderma croceum. Shoot and root flushes were related to parallel shifts in above- and below-ground C and, to a lesser extent, N allocation. Increased plant internal resource availability by P. croceum inoculation with enhanced plant growth affected neither the rhythmic growth nor the associated resource allocation patterns. Two shifts in transcript abundance were identified during root and shoot growth cessation, and most concerned genes were down-regulated. Inoculation with P. croceum suppressed these transcript shifts in roots, but not in shoots. To identify core processes governing the rhythmic growth, functions [Gene Ontology (GO) terms] of the genes differentially expressed during the growth cessation in both leaves and roots of non-inoculated plants and leaves of P. croceum-inoculated plants were examined. Besides genes related to resource acquisition and cell development, which might reflect rather than trigger rhythmic growth, genes involved in signalling and/or regulated by the circadian clock were identified. The results indicate that rhythmic growth involves dramatic oscillations in plant metabolism and gene regulation between below- and above-ground parts. Ectomycorrhizal symbiosis may play a previously unsuspected role in smoothing these oscillations without modifying the rhythmic growth pattern. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Application of bacteria from non-cultivated plants to promote growth, alter root architecture and alleviate salt stress of cotton.

PubMed

Irizarry, I; White, J F

2017-04-01

Cotton seeds are frequently treated with acid to remove fibres and reduce seed-transmitted diseases. This process also eliminates beneficial bacteria on the seed surface. The goal of this research was to seek and apply beneficial bacteria to acid delinted cotton seeds to evaluate their growth-promoting and salt stress alleviating effects in seedlings. Bacteria were isolated from non-cultivated plants in the Malvaceae. Seeds were collected from Portia tree (Thespesia populnea) and wild cotton (Gossypium hirsutum) from coastal and arid areas of Puerto Rico. Bacillus amyloliquefaciens, Curtobacterium oceanosedimentum and Pseudomonas oryzihabitans were inoculated onto acid delinted cotton seeds. Bacteria increased cotton seed germination and length of emerging seedling radicles. Cotton seeds were inoculated with B. amyloliquefaciens to evaluate growth and root architecture of non-stressed and salt stressed seedlings. Inoculating cotton seeds with B. amyloliquefaciens led to a greater percentage of seedlings with expanded cotyledons after 8 days, enhanced primary and lateral root growth, and altered root architecture. Similar results were obtained when okra seeds were inoculated with B. amyloliquefaciens. The data supported the hypothesis that non-cultivated plants in the Malvaceae growing in stressful environments possess bacteria that promote growth, alter root architecture and alleviate salt stress of cotton and okra seedlings. This study demonstrated the effects of applying beneficial bacteria on acid delinted cotton seeds. Inoculating seeds with salt stress alleviating bacteria could improve the growth of crop seedlings that are vulnerable to soil salinization. © 2017 The Society for Applied Microbiology.

Endophytic bacteria improve phytoremediation of Ni and TCE co-contamination.

PubMed

Weyens, Nele; Croes, Sarah; Dupae, Joke; Newman, Lee; van der Lelie, Daniel; Carleer, Robert; Vangronsveld, Jaco

2010-07-01

The aim of this work was to investigate if engineered endophytes can improve phytoremediation of co-contaminations by organic pollutants and toxic metals. As a model system, yellow lupine was inoculated with the endophyte Burkholderia cepacia VM1468 possessing (a) the pTOM-Bu61 plasmid, coding for constitutive trichloroethylene (TCE) degradation, and (b) the ncc-nre Ni resistance/sequestration system. Plants were exposed to Ni and TCE and (a) Ni and TCE phytotoxicity, (b) TCE degradation and evapotranspiration, and (c) Ni concentrations in the roots and shoots were determined. Inoculation with B. cepacia VM1468 resulted in decreased Ni and TCE phytotoxicity, as measured by 30% increased root biomass and up to 50% decreased activities of enzymes involved in anti-oxidative defence in the roots. In addition, TCE evapotranspiration showed a decreasing trend and a 5 times higher Ni uptake was observed after inoculation. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

The Potential of the Ni-Resistant TCE-Degrading Pseudomonas putida W619-TCE to Reduce Phytotoxicity and Improve Phytoremediation Efficiency of Poplar Cuttings on A Ni-TCE Co-Contamination.

PubMed

Weyens, Nele; Beckers, Bram; Schellingen, Kerim; Ceulemans, Reinhart; van der Lelie, Daniel; Newman, Lee; Taghavi, Safiyh; Carleer, Robert; Vangronsveld, Jaco

2015-01-01

To examine the potential of Pseudomonas putida W619-TCE to improve phytoremediation of Ni-TCE co-contamination, the effects of inoculation of a Ni-resistant, TCE-degrading root endophyte on Ni-TCE phytotoxicity, Ni uptake and trichloroethylene (TCE) degradation of Ni-TCE-exposed poplar cuttings are evaluated. After inoculation with P. putida W619-TCE, root weight of non-exposed poplar cuttings significantly increased. Further, inoculation induced a mitigation of the Ni-TCE phytotoxicity, which was illustrated by a diminished exposure-induced increase in activity of antioxidative enzymes. Considering phytoremediation efficiency, inoculation with P. putida W619-TCE resulted in a 45% increased Ni uptake in roots as well as a slightly significant reduction in TCE concentration in leaves and TCE evapotranspiration to the atmosphere. These results indicate that endophytes equipped with the appropriate characteristics can assist their host plant to deal with co-contamination of toxic metals and organic contaminants during phytoremediation. Furthermore, as poplar is an excellent plant for biomass production as well as for phytoremediation, the obtained results can be exploited to produce biomass for energy and industrial feedstock applications in a highly productive manner on contaminated land that is not suited for normal agriculture. Exploiting this land for biomass production could contribute to diminish the conflict between food and bioenergy production.

Phenotypical and molecular responses of Arabidopsis thaliana roots as a result of inoculation with the auxin-producing bacterium Azospirillum brasilense.

PubMed

Spaepen, Stijn; Bossuyt, Stijn; Engelen, Kristof; Marchal, Kathleen; Vanderleyden, Jos

2014-02-01

The auxin-producing bacterium Azospirillum brasilense Sp245 can promote the growth of several plant species. The model plant Arabidopsis thaliana was chosen as host plant to gain an insight into the molecular mechanisms that govern this interaction. The determination of differential gene expression in Arabidopsis roots after inoculation with either A. brasilense wild-type or an auxin biosynthesis mutant was achieved by microarray analysis. Arabidopsis thaliana inoculation with A. brasilense wild-type increases the number of lateral roots and root hairs, and elevates the internal auxin concentration in the plant. The A. thaliana root transcriptome undergoes extensive changes on A. brasilense inoculation, and the effects are more pronounced at later time points. The wild-type bacterial strain induces changes in hormone- and defense-related genes, as well as in plant cell wall-related genes. The A. brasilense mutant, however, does not elicit these transcriptional changes to the same extent. There are qualitative and quantitative differences between A. thaliana responses to the wild-type A. brasilense strain and the auxin biosynthesis mutant strain, based on both phenotypic and transcriptomic data. This illustrates the major role played by auxin in the Azospirillum-Arabidopsis interaction, and possibly also in other bacterium-plant interactions. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Arbuscular mycorrhizal strategy for zinc mycoremediation and diminished translocation to shoots and grains in wheat.

PubMed

Abu-Elsaoud, Abdelghafar M; Nafady, Nivien A; Abdel-Azeem, Ahmed M

2017-01-01

Mycoremediation is an on-site remediation strategy, which employs fungi to degrade or sequester contaminants from the environment. The present work focused on the bioremediation of soils contaminated with zinc by the use of a native mycorrhizal fungi (AM) called Funneliformis geosporum (Nicol. & Gerd.) Walker & Schüßler. Experiments were performed using Triticum aestivum L. cv. Gemmeza-10 at different concentrations of Zn (50, 100, 200 mg kg-1) and inoculated with or without F. geosporum. The results showed that the dry weight of mycorrhizal wheat increased at Zn stressed plants as compared to the non-Zn-stressed control plants. The concentrations of Zn also had an inhibitory effect on the yield of dry root and shoot of non-mycorrhizal wheat. The photosynthetic pigment fractions were significantly affected by Zn treatments and mycorrhizal inoculation, where in all treatments, the content of the photosynthetic pigment fractions decreased as the Zn concentration increased in the soil. However, the level of minerals of shoots, roots, and grains was greatly influenced by Zn-treatment and by inoculation with F. geosporum. Treatment with Zn in the soil increased Cu and Zn concentrations in the root, shoot and grains, however, other minerals (P, S, K, Ca and Fe) concentration was decreased. Inoculation of wheat with AM fungi significantly reduced the accumulation of Zn and depressed its translocation in shoots and grains of wheat. In conclusion, inoculation with a native F. geosporum-improves yields of wheat under higher levels of Zn and is possible to be applied for the improvement of zinc contaminated soil.

Arbuscular mycorrhizal strategy for zinc mycoremediation and diminished translocation to shoots and grains in wheat

PubMed Central

2017-01-01

Mycoremediation is an on-site remediation strategy, which employs fungi to degrade or sequester contaminants from the environment. The present work focused on the bioremediation of soils contaminated with zinc by the use of a native mycorrhizal fungi (AM) called Funneliformis geosporum (Nicol. & Gerd.) Walker & Schüßler. Experiments were performed using Triticum aestivum L. cv. Gemmeza-10 at different concentrations of Zn (50, 100, 200 mg kg-1) and inoculated with or without F. geosporum. The results showed that the dry weight of mycorrhizal wheat increased at Zn stressed plants as compared to the non-Zn-stressed control plants. The concentrations of Zn also had an inhibitory effect on the yield of dry root and shoot of non-mycorrhizal wheat. The photosynthetic pigment fractions were significantly affected by Zn treatments and mycorrhizal inoculation, where in all treatments, the content of the photosynthetic pigment fractions decreased as the Zn concentration increased in the soil. However, the level of minerals of shoots, roots, and grains was greatly influenced by Zn-treatment and by inoculation with F. geosporum. Treatment with Zn in the soil increased Cu and Zn concentrations in the root, shoot and grains, however, other minerals (P, S, K, Ca and Fe) concentration was decreased. Inoculation of wheat with AM fungi significantly reduced the accumulation of Zn and depressed its translocation in shoots and grains of wheat. In conclusion, inoculation with a native F. geosporum-improves yields of wheat under higher levels of Zn and is possible to be applied for the improvement of zinc contaminated soil. PMID:29145471

Symbiotic N nutrition, bradyrhizobial biodiversity and photosynthetic functioning of six inoculated promiscuous-nodulating soybean genotypes.

PubMed

Pule-Meulenberg, Flora; Gyogluu, Cynthia; Naab, Jesse; Dakora, Felix D

2011-04-15

Six promiscuous soybean genotypes were assessed for their ability to nodulate with indigenous root-nodule bacteria in Ghana, with Bradyrhizobium japonicum WB74 serving as positive control. Although the results revealed free nodulation of all six genotypes in both inoculated and uninoculated plots, there was a marked effect of inoculation on photosynthetic rates and whole-plant C. Inoculation also increased stomatal conductance in TGx1485-1D, TGx1448-2E, TGx1740-2F and TGx1445-3E, leading to significantly elevated transpiration rates in the last two genotypes, and a decrease in TGx1485-1D, TGx1440-1E and Salintuya-1, resulting in reduced leaf transpiration and decreased C accumulation. Nodulation, total plant biomass, plant N concentration and content also increased and ∂(15)N of the six genotypes, except for TGx1448-2E decreased. Significantly higher %Ndfa resulted in all the soybean genotypes tested (except for TGx1485-1D), and the symbiotic N yield in TGx1740-2F and TGx1448-2E doubled. PCR-RFLP revealed 18 distinct IGS types present in root nodules of the six promiscuous soybean genotypes, with IGS type II being isolated from all six genotypes, followed by IGS types X and XI from five out of the six genotypes. Marked differences in strain IGS type symbiotic efficiency were revealed. For example, as sole nodule occupant, IGS type XI produced high symbiotic N in TGx1445-3E, but low amounts in TGx1448-2E. Inoculated Salintuya-1, which trapped nine strain IGS types in its root nodules, was the most promiscuous genotype, but produced less symbiotic N compared to genotypes with fewer strains in their root nodules. Copyright © 2010 Elsevier GmbH. All rights reserved.

Oxidative Stress Induced in Sunflower Seedling Roots by Aqueous Dry Olive-Mill Residues

PubMed Central

Garrido, Inmaculada; García-Sánchez, Mercedes; Casimiro, Ilda; Casero, Pedro Joaquin; García-Romera, Inmaculada; Ocampo, Juan Antonio; Espinosa, Francisco

2012-01-01

The contamination of soils with dry olive-mill residue can represent a serious problem as being an environmental stressor in plants. It has been demonstrated that inoculation of aqueous extract of olive oil-mill residue (ADOR) with saprobe fungi removes some phenolic compounds. In this paper we studied the effect of ADOR uninoculated or inoculated with saprobe fungi in sunflower seedling roots. The germination and root growth, O2·- generation, superoxide dismutase (SOD) and extracellular peroxidases (EC-POXs) activities, and the content of some metabolites involved in the tolerance of stress were tested. The roots germinated in ADOR uninoculated show a decrease in meristem size, resulting in a reduction of the root length and fresh weight, and in the number of layers forming the cortex, but did not alter the dry weight, protein and soluble amino acid content. ADOR caused the decreases in O2·- generation and EC-POX′s activities and protein oxidation, but enhanced SOD activity, lipid peroxidation and proline content. Fluorescence imaging showed that ADOR induced O2·- and H2O2 accumulation in the roots. The increase in SOD and the decrease in EC-POX′s activities might be involved in the enhancement of H2O2 content and lipid peroxidation. Control roots treated with ADOR for 10 min show an oxidative burst. Roots germinated in ADOR inoculated with saprobe fungi partially recovered normal levels of ROS, morphological characteristics and antioxidant activities. These results suggested that treatment with ADOR caused a phytotoxic effect during germination inducing an oxidative stress. The inoculation of ADOR with saprobe fungi limited the stress. PMID:23049960

Interaction of Pratylenchus penetrans and Rhizoctonia fragariae in Strawberry Black Root Rot

PubMed Central

LaMondia, J. A.

2003-01-01

A split-root technique was used to examine the interaction between Pratylenchus penetrans and the cortical root-rotting pathogen Rhizoctonia fragariae in strawberry black root rot. Plants inoculated with both pathogens on the same half of a split-root crown had greater levels of root rot than plants inoculated separately or with either pathogen alone. Isolation of R. fragariae from field-grown roots differed with root type and time of sampling. Fungal infection of structural roots was low until fruiting, whereas perennial root colonization was high. Isolation of R. fragariae from feeder roots was variable, but was greater from feeder roots on perennial than from structural roots. Isolation of the fungus was greater from structural roots with nematode lesions than from non-symptomatic roots. Rhizoctonia fragariae was a common resident on the sloughed cortex of healthy perennial roots. From this source, the fungus may infect additional roots. The direct effects of lesion nematode feeding and movement are cortical cell damage and death. Indirect effects include discoloration of the endodermis and early polyderm formation. Perhaps weakened or dying cells caused directly or indirectly by P. penetrans are more susceptible to R. fragariae, leading to increased disease. PMID:19265969

Can arbuscular mycorrhizal fungi reduce Cd uptake and alleviate Cd toxicity of Lonicera japonica grown in Cd-added soils?

NASA Astrophysics Data System (ADS)

Jiang, Qiu-Yun; Zhuo, Feng; Long, Shi-Hui; Zhao, Hai-Di; Yang, Dan-Jing; Ye, Zhi-Hong; Li, Shao-Shan; Jing, Yuan-Xiao

2016-02-01

A greenhouse pot experiment was conducted to study the impact of arbuscular mycorrhizal fungi-Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on the growth, Cd uptake, antioxidant indices [glutathione reductase (GR), ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), ascorbate (ASA), glutathione (GSH) and malonaldehyde (MDA)] and phytochelatins (PCs) production of Lonicera japonica in Cd-amended soils. Gv and Ri significantly increased P acquisition, biomass of shoots and roots at all Cd treatments. Gv significantly decreased Cd concentrations in shoots and roots, and Ri also obviously reduced Cd concentrations in shoots but increased Cd concentrations in roots. Meanwhile, activities of CAT, APX and GR, and contents of ASA and PCs were remarkably higher in Gv/Ri-inoculated plants than those of uninoculated plants, but lower MDA and GSH contents in Gv/Ri-inoculated plants were found. In conclusion, Gv and Ri symbiosis alleviated Cd toxicity of L. japonica through the decline of shoot Cd concentrations and the improvement of P nutrition, PCs content and activities of GR, CAT, APX in inoculated plants, and then improved plant growth. The decrease of shoot Cd concentrations in L. japonica inoculated with Gv/Ri would provide a clue for safe production of this plant from Cd-contaminated soils.

An endophytic bacterium Acinetobacter calcoaceticus Sasm3-enhanced phytoremediation of nitrate-cadmium compound polluted soil by intercropping Sedum alfredii with oilseed rape.

PubMed

Chen, Bao; Ma, Xiaoxiao; Liu, Guiqing; Xu, Xiaomeng; Pan, Fengshan; Zhang, Jie; Tian, Shengke; Feng, Ying; Yang, Xiaoe

2015-11-01

Intensive agricultural system with high input of fertilizer results in high agricultural output. However, excessive fertilization in intensive agricultural system has great potential to cause nitrate and heavy metal accumulation in soil, which is adverse to human health. The main objective of the present study was to observe the effects of intercropping and inoculation of endophytic bacterium Acinetobacter calcoaceticus Sasm3 on phytoremediation of combined contaminated soil in oilseed rape (Brassica napus L.). The results showed that with Sasm3 inoculation, the biomass of rape was increased by 10-20% for shoot, 64% for root, and 23-29% for seeds while the nitrate accumulation in rape was decreased by 14% in root and by 12% in shoot. The cadmium concentration in rape increased significantly with mono-inoculating treatment, whereas it decreased significantly after intercropping treatment. By denaturing gradient gel electrophoresis (DGGE) and real-time quantitative PCR analysis, the diversity of bacterial community and the number of nirS and nirK gene copies increased significantly with inoculation or/and intercropping treatment. In conclusion, the endophytic bacterium Sasm3-inoculated intercropping system not only improved the efficiency of clearing cadmium from soil without obstructing crop production, but also improved the quality of crop.

Inoculant of Arbuscular Mycorrhizal Fungi (Rhizophagus clarus) Increase Yield of Soybean and Cotton under Field Conditions.

PubMed

Cely, Martha V T; de Oliveira, Admilton G; de Freitas, Vanessa F; de Luca, Marcelo B; Barazetti, André R; Dos Santos, Igor M O; Gionco, Barbara; Garcia, Guilherme V; Prete, Cássio E C; Andrade, Galdino

2016-01-01

Nutrient availability is an important factor in crop production, and regular addition of chemical fertilizers is the most common practice to improve yield in agrosystems for intensive crop production. The use of some groups of microorganisms that have specific activity providing nutrients to plants is a good alternative, and arbuscular mycorrhizal fungi (AMF) enhance plant nutrition by providing especially phosphorus, improving plant growth and increasing crop production. Unfortunately, the use of AMF as an inoculant on a large scale is not yet widely used, because of several limitations in obtaining a large amount of inoculum due to several factors, such as low growth, the few species of AMF domesticated under in vitro conditions, and high competition with native AMF. The objective of this work was to test the infectivity of a Rhizophagus clarus inoculum and its effectiveness as an alternative for nutrient supply in soybean (Glycine max L.) and cotton (Gossypium hirsutum L.) when compared with conventional chemical fertilization under field conditions. The experiments were carried out in a completely randomized block design with five treatments: Fertilizer, AMF, AMF with Fertilizer, AMF with 1/2 Fertilizer, and the Control with non-inoculated and non-fertilized plants. The parameters evaluated were AMF root colonization and effect of inoculation on plant growth, nutrient absorption and yield. The results showed that AMF inoculation increased around 20 % of root colonization in both soybean and cotton; nutrients analyses in vegetal tissues showed increase of P and nitrogen content in inoculated plants, these results reflect in a higher yield. Our results showed that, AMF inoculation increase the effectiveness of fertilizer application in soybean and reduce the fertilizer dosage in cotton.

[Effects of root-knot nematodes on cucumber leaf N and P contents, soil pH, and soil enzyme activities].

PubMed

Xu, Hua; Ruan, Wei-Bin; Gao, Yu-Bao; Song, Xiao-Yan; Wei, Yu-Kun

2010-08-01

A pot experiment was conducted to study the effects of inoculation with root-knot nematodes on the cucumber leaf N and P contents, and the rhizospheric and non-rhizospheric soil pH and enzyme activities. The rhizospheric soil pH didn't have a significant decrease until the inoculation rate reached 6000 eggs per plant. With the increase of inoculation rate, the leaf N and P contents, rhizospheric soil peroxidase activity, and rhizospheric and non-rhizospheric soil polyphenol oxidase activity all decreased gradually, rhizospheric soil catalase activity was in adverse, non-rhizospheric soil pH decreased after an initial increase, and non-rhizospheric soil catalase activity had no regular change. After inoculation, rhizospheric soil urease activity decreased significantly, but rhizospheric and non-rhizospheric soil phosphatase activity and non-rhizospheric soil peroxidase activity only had a significant decrease under high inoculation rate. In most cases, there existed significant correlations between rhizospheric soil pH, enzyme activities, and leaf N and P contents; and in some cases, there existed significant correlations between non-rhizospheric soil pH, enzyme activities, and leaf N and P contents.

Interaction of Vesicular-arbuscular Mycorrhizal Fungi and Phosphorus with Meloidogyne incognita on Tomato.

PubMed

Cason, K M; Hussey, R S; Roncadori, R W

1983-07-01

The influence of two vesicular-arbuscular mycorrhizal fungi and phosphorus (P) nutrition on penetration, development, and reproduction by Meloidogyne incognita on Walter tomato was studied in the greenhouse. Inoculation with either Gigaspora margarita or Glomus mosseae 2 wk prior to nematode inoculation did not alter infection by M. incognita compared with nonmycorrhizal plants, regardless of soil P level (either 3 mug [low P] or 30 mug [high P] available P/g soil). At a given soil P level, nematode penetration and reproduction did not differ in mycorrhizal and nonmycorrhizal plants. However, plants grown in high P soil had greater root weights, increased nematode penetration and egg production per plant, and decreased colonization by mycorrhizal fungi, compared with plants grown in low P soil. The number of eggs per female nematode on mycorrhizal and nonmycorrhizal plants was not influenced by P treatment. Tomato plants with split root systems grown in double-compartment containers which had either low P soil in both sides or high P in one side and low P in the other, were inoculated at transplanting with G. margarita and 2 wk later one-half of the split root system of each plant was inoculated with M. incognita larvae. Although the mycoorhizal fungus increased the inorganic P content of the root to a level comparable to that in plants grown in high P soil, nematode penetration and reproduction were not altered. In a third series of experiments, the rate of nematode development was not influenced by either the presence of G. margarita or high soil P, compared with control plants grown in low P soil. These data indicate that supplemental P (30 mu/g soil) alters root-knot nematode infection of tomato more than G. mosseae and G. margarita.

Two poplar-associated bacterial isolates induce additive favorable responses in a constructed plant-microbiome system

DOE PAGES

Jawdy, Sara S.; Gunter, Lee E.; Engle, Nancy L.; ...

2016-04-26

Here, the biological function of the plant-microbiome system is the result of contributions from the host plant and microbiome members. In this work we study the function of a simplified community consisting of Pseudomonas and Burkholderia bacterial strains isolated from Populus hosts and inoculated on axenic Populus cutting in controlled laboratory conditions. Inoculation individually with either bacterial isolate increased root growth relative to uninoculated controls. Root area, photosynthetic efficiency, gene expression and metabolite expression data in individual and dual inoculated treatments indicate that the effects of these bacteria are unique and additive, suggesting that the function of a microbiome communitymore » may be predicted from the additive functions of the individual members.« less

Effects of Macroposthonia xenoplax on the growth of Concord grape.

PubMed

Santo, G S; Bolander, W J

1977-07-01

Concord grape (Vitis labrusca) plants were inoculated with Macroposthonia xenoplax at levels of 100, 1,000, and 10,000 nematodes. After 4 months, plants inoculated with 10,000 M. xenoplax were stunted, and root systems were darker and had fewer feeder roots than those in other treatments. The lower nematode inoculation levels suppressed top growth but did not affect root growth. M. xenoplax reproduced well on Concord grapes.

Arsenic accumulation and speciation in maize as affected by inoculation with arbuscular mycorrhizal fungus Glomus mosseae.

PubMed

Yu, Yang; Zhang, Shuzhen; Huang, Honglin; Luo, Lei; Wen, Bei

2009-05-13

Effects of inoculation with arbuscular mycorrhizal (AM) fungus (Glomus mosseae) on arsenic (As) accumulation and speciation in maize were investigated by using As spiked soil at the application levels of 0, 25, 50, and 100 mg kg(-1). Inorganic As was the major species in plants, and mycorrhizal inoculation generally decreased concentrations of arsenite [As(III)] in maize roots and concentrations of As(III) and arsenate [As(V)] in the shoots. Dimethylarsenic acid (DMA) concentrations (detected in every plant sample) were higher in maize shoots for mycorrhizal than for nonmycorrhizal treatment, but no significant differences were observed for roots. Monomethylarsenic acid (MMA) was only detected in roots with mycorrhizal colonization. The uptake of As(V) was much lower by excised mycorrhizal than nonmycorrhizal roots, and the differences for the uptake of As(III) were negligible. Arsenate reductase (AR) activity was detected in maize roots, and it was reduced with mycorrhizal inoculation. Activities of peroxidase (POD) and superoxide dismutase (SOD) were detected in both maize shoots and roots, and they were suppressed by mycorrhizal inoculation. AM inoculation inhibited the uptake of As(V) and its reduction to As(III), reducing oxidation stress and thereby alleviating As toxicity to the host plant.

Copper-resistant bacteria reduces oxidative stress and uptake of copper in lentil plants: potential for bacterial bioremediation.

PubMed

Islam, Faisal; Yasmeen, Tahira; Ali, Qasim; Mubin, Muhammad; Ali, Shafaqat; Arif, Muhammad Saleem; Hussain, Sabir; Riaz, Muhammad; Abbas, Farhat

2016-01-01

For effective microbe-assisted bioremediation, metal-resistant plant growth-promoting bacteria (PGPB) must facilitate plant growth by restricting excess metal uptake in plants, leading to prevent its bio-amplification in the ecosystem. The aims of our study were to isolate and characterize copper (Cu)-resistant PGPB from waste water receiving contaminated soil. In addition, we investigated the phytotoxic effect of copper on the lentil plants inoculated with copper-resistant bacteria Providencia vermicola, grown in copper-contaminated soil. Copper-resistant P. vermicola showed multiple plant growth promoting characteristics, when used as a seed inoculant. It protected the lentil plants from copper toxicity with a considerable increase in root and shoot length, plant dry weight and leaf area. A notable increase in different gas exchange characteristics such as A, E, C i , g s , and A/E, as well as increase in N and P accumulation were also recorded in inoculated plants as compared to un-inoculated copper stressed plants. In addition, leaf chlorophyll content, root nodulation, number of pods, 1,000 seed weight were also higher in inoculated plants as compared with non-inoculated ones. Anti-oxidative defense mechanism improved significantly via elevated expression of reactive oxygen species -scavenging enzymes including ascorbate peroxidase, superoxide dismutase, catalase, and guaiacol peroxidase with alternate decrease in malondialdehyde and H2O2 contents, reduced electrolyte leakage, proline, and total phenolic contents suggesting that inoculation of P. vermicola triggered heavy metals stress-related defense pathways under copper stress. Overall, the results demonstrated that the P. vermicola seed inoculation confer heavy metal stress tolerance in lentil plant which can be used as a potent biotechnological tool to cope with the problems of copper pollution in crop plants for better yield.

Reactions of Grape Rootstocks to Pratylenchus vulnus and Meloidogyne spp.

PubMed

Chitambar, J J; Raski, D J

1984-04-01

Five grape rootstocks were inoculated with 0, 100, 1,000, and 10,000 Pratylenchus vulnus. Dogridge and Saltcreek supported low average total numbers of P. vulnus, 136-705/pot, at 12 months after inoculation. Growth of both rootstocks was not affected. Harmony, Couderc 1613, and Ganzin 1 supported high average total numbers, 6-856 times the inoculum levels. Numbers in Harmony continued to increase at all levels but reduced root weight only at the 10,000 level after 12 months. Numbers in Couderc 1613 decreased by 15-30% after 12 months, and root weight was reduced at the 10,000 level. In Ganzin 1, total nematode numbers diminished after 12 months but were still at high levels; growth reduction was proportional to numbers of nematodes added. Meloidogyne incognita, M. javanica, and M. arenaria produced galls and egg masses in Harmony and Couderc 1613 only at 36 C. Galling in Ganzin 1 increased with increasing temperature. Galls in Ganzin 1 at 18 C supported mature females after 90 days. Harmony was resistant to M. incognita in single and concomitant inoculations of P. vulnus and M. incognita. At 250 days after inoculation, total numbers of P. vulnus increased above the inoculum level and the 150-day values; increase was greatest in P. vulnus added singly. Neither nematode species affected growth of Harmony.

Effect of immobilized rhizobacteria and organic amendment in bulk and rhizospheric soil of Cistus albidus L.

NASA Astrophysics Data System (ADS)

Mengual, Carmen Maria; del Mar Alguacil, Maria; Roldan, Antonio; Schoebitz, Mauricio

2013-04-01

A field experiment was carried out to assess the effectiveness of the immobilized microbial inoculant and the addition of organic olive residue. The microbial inoculant contained two rhizobacterial species identified as Azospirillum brasilense and Pantoea dispersa immobilized in a natural inert support. Bacterial population densities were 3.5×109 and 4.1×109 CFU g-1 of A. brasilense M3 and P. dispersa C3, respectively. The amendment used was the organic fraction extracted with KOH from composted "alperujo". The raw material was collected from an olive-mill and mixed with fresh cow bedding as bulking agent for composting. The inoculation of rhizobacteria and the addition of organic residue were employed for plant growth promotion of Cistus albidus L. and enhancement of soil physicochemical, biochemical and biological properties in a degraded semiarid Mediterranean area. One year after planting, the available phosphorus and potassium content in the amended soils was about 100 and 70% respectively higher than in the non-amended soil. Microbial inoculant and their interaction with organic residue increased the aggregate stability of the rhizosphere soil of C. albidus (by 12% with respect to control soil) while the organic residue alone not increased the aggregate stability of the rhizosphere of C. albidus. Microbial biomass C content and enzyme activities (dehydrogenase, urease, protease-BAA and alkaline phosphatase) of the rhizosphere of C. albidus were increased by microbial inoculant and organic residue interaction but not by microbial inoculation alone. The microbial inoculant and organic residue interaction were the most effective treatment for stimulating the roots dry weight of C. albidus (by 133% with respect to control plants) and microbial inoculant was the most effective treatment for increase the shoot dry weigh of plants (by 106% with respect to control plants). The combined treatment, involving microbial inoculant and addition of the organic residue directly into the soil, had additive effect on the root growth of C. albidus and chemical and biological quality of soil.

Endophytic bacteria take the challenge to improve Cu phytoextraction by sunflower.

PubMed

Kolbas, Aliaksandr; Kidd, Petra; Guinberteau, Jacques; Jaunatre, Renaud; Herzig, Rolf; Mench, Michel

2015-04-01

Endophytic bacteria from roots and crude seed extracts of a Cu-tolerant population of Agrostis capillaris were inoculated to a sunflower metal-tolerant mutant line, and their influence on Cu tolerance and phytoextraction was assessed using a Cu-contaminated soil series. Ten endophytic bacterial strains isolated from surface-sterilized A. capillaris roots were mixed to prepare the root endophyte inoculant (RE). In parallel, surface-sterilized seeds of A. capillaris were crushed in MgSO4 to prepare a crude seed extract containing seed endophytes (SE). An aliquot of this seed extract was filtered at 0.2 μm to obtain a bacterial cell-free seed extract (SEF). After surface sterilization, germinated sunflower seeds were separately treated with one of five modalities: no treatment (C), immersion in MgSO4 (CMg) or SEF solutions and inoculation with RE or SE. All plants were cultivated on a Cu-contaminated soil series (13-1020 mg Cu kg(-1)). Cultivable RE strains were mostly members of the Pseudomonas genera, and one strain was closely related to Labrys sp. The cultivable SE strains belonged mainly to the Bacillus genera and some members of the Rhodococcus genera. The treatment effects depended on the soil Cu concentration. Both SE and SEF plants had a higher Cu tolerance in the 13-517 mg Cu kg(-1) soil range as reflected by increased shoot and root DW yields compared to control plants. This was accompanied by a slight decrease in shoot Cu concentration and increase in root Cu concentration. Shoot and root DW yields were more promoted by SE than SEF in the 13-114 mg Cu kg(-1) soil range, which could reflect the influence of seed-located bacterial endophytes. At intermediate soil Cu (416-818 mg Cu kg(-1) soil), the RE and CMg plants had lower shoot Cu concentrations than the control, SE and SEF plants. At high total soil Cu (617-1020 mg Cu kg(-1)), root DW yield of RE plants slightly increased and their root Cu concentration rose by up to 1.9-fold. In terms of phytoextraction efficiency, shoot Cu removal was increased for sunflower plants inoculated with crude and bacterial cell-free seed extracts by 1.3- to 2.2-fold in the 13-416 mg Cu kg(-1) soil range. Such increase was mainly driven by an enhanced shoot DW yield. The number and distribution of endophytic bacteria in the harvested sunflower tissues must be further examined.

Root ethylene signalling is involved in Miscanthus sinensis growth promotion by the bacterial endophyte Herbaspirillum frisingense GSF30T

PubMed Central

Ludewig, Uwe

2013-01-01

The bacterial endophyte Herbaspirillum frisingense GSF30T is a colonizer of several grasses grown in temperate climates, including the highly nitrogen-efficient perennial energy grass Miscanthus. Inoculation of Miscanthus sinensis seedlings with H. frisingense promoted root and shoot growth but had only a minor impact on nutrient concentrations. The bacterium affected the root architecture and increased fine-root structures. Although H. frisingense has the genetic requirements to fix nitrogen, only minor changes in nitrogen concentrations were observed. Herbaspirillum agglomerates were identified primarily in the root apoplast but also in the shoots. The short-term (3h) and long-term (3 weeks) transcriptomic responses of the plant to bacterial inoculation revealed that H. frisingense induced rapid changes in plant hormone signalling, most prominent in jasmonate signalling. Ethylene signalling pathways were also affected and persisted after 3 weeks in the root. Growth stimulation of the root by the ethylene precursor 1-aminocyclopropane 1-carboxylic acid was dose dependent and was affected by H. frisingense inoculation. Minor changes in the proteome were identified after 3 weeks. This study suggests that H. frisingense improves plant growth by modulating plant hormone signalling pathways and provides a framework to understand the beneficial effects of diazotrophic plant-growth-promoting bacteria, such as H. frisingense, on the biomass grass Miscanthus. PMID:24043849

Impact of endophytic colonization patterns on Zamioculcas zamiifolia stress response and in regulating ROS, tryptophan and IAA levels under airborne formaldehyde and formaldehyde-contaminated soil conditions.

PubMed

Khaksar, Gholamreza; Treesubsuntorn, Chairat; Thiravetyan, Paitip

2017-05-01

Deeper understanding of plant-endophyte interactions under abiotic stress would provide new insights into phytoprotection and phytoremediation enhancement. Many studies have investigated the positive role of plant-endophyte interactions in providing protection to the plant against pollutant stress through auxin (indole-3-acetic acid (IAA)) production. However, little is known about the impact of endophytic colonization patterns on plant stress response in relation to reactive oxygen species (ROS) and IAA levels. Moreover, the possible effect of pollutant phase on plant stress response is poorly understood. Here, we elucidated the impact of endophytic colonization patterns on plant stress response under airborne formaldehyde compared to formaldehyde-contaminated soil. ROS, tryptophan and IAA levels in the roots and shoots of endophyte-inoculated and non-inoculated plants in the presence and absence of formaldehyde were measured. Strain-specific quantitative polymerase chain reaction (qPCR) was used to investigate dynamics of endophyte colonization. Under the initial exposure to airborne formaldehyde, non-inoculated plants accumulated more tryptophan in the shoots (compared to the roots) to synthesize IAA. However, endophyte-inoculated plants behaved differently as they synthesized and accumulated more tryptophan in the roots and, hence, higher levels of IAA accumulation and exudation within roots which might act as a signaling molecule to selectively recruit B. cereus ERBP. Under continuous airborne formaldehyde stress, higher levels of ROS accumulation in the shoots pushed the plant to synthesize more tryptophan and IAA in the shoots (compared to the roots). Higher levels of IAA in the shoots might act as the potent driving force to relocalize B. cereus ERBP from roots to the shoots. In contrast, under formaldehyde-contaminated soil, B. cereus ERBP colonized root tissues without moving to the shoots since there was a sharp increase in ROS, tryptophan and IAA levels of the roots without any significant increase in the shoots. Pollutant phase affected endophytic colonization patterns and plant stress responses differently. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Cadmium accumulation in sunflower plants influenced by arbuscular mycorrhiza.

PubMed

de Andrade, Sara Adrián López; da Silveira, Adriana Parada Dias; Jorge, Renato Atílio; de Abreu, Mônica Ferreira

2008-01-01

In order to investigate the cadmium (Cd) accumulation patterns and possible alleviation of Cd stress by mycorrhization, sunflower plants (Helianthus annuus L.) were grown in the presence or absence of Cd (20 micromol L(-1)) and inoculated or not inoculated with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices. No visual symptoms of Cd phytotoxicity were observed; nevertheless, in non-mycorrhizal plants the presence of Cd decreased plant growth. The addition of Cd had no significant effect on either mycorrhizal colonization or the amount of extra-radical mycelia that was produced by the AMF. Cd accumulated mainly in roots; only 22% of the total Cd absorbed was translocated to the shoots, where it accumulated to an average of 228 mg Cd kg(-1). Although the shoot-to-root ratio of Cd was similar in both the AMF inoculated and non-inoculated plants, the total absorbed Cd was 23% higher in mycorrhizal plants. Cd concentration in AMF extra-radical mycelium was 728 microg g(-1) dry weight. Despite the greater absorption of Cd, mycorrhizal plants showed higher photosynthetic pigment concentrations and shoot P contents. Cd also influenced mineral nutrition, leading to decreased Ca and Cu shoot concentrations; N, Fe and Cu shoot contents; and increased S and K shoot concentrations. Cd induced guaiacol peroxidase activity in roots in both mycorrhizal and non-mycorrhizal plants, but this increase was much more accentuated in non-mycorrhizal roots. In conclusion, sunflower plants associated with G. intraradices were less sensitive to Cd stress than non-mycorrhizal plants. Mycorrhizal sunflowers showed enhanced Cd accumulation and some tolerance to excessive Cd concentrations in plant tissues.

Periapical inflammation subsequent to coronal inoculation of dog teeth root filled with resilon/epiphany in 1 or 2 treatment sessions with chlorhexidine medication.

PubMed

Santos, João M; Palma, Paulo J; Ramos, João C; Cabrita, António S; Friedman, Shimon

2014-06-01

Therapeutic methods that inhibit microbial ingress into filled root canals are desirable. This in vivo study assessed the inhibition of periapical inflammation subsequent to coronal inoculation in canals medicated with 2% chlorhexidine gel and filled with Resilon/Epiphany (Pentron Clinical Technologies, Wallingford, CT). Six Beagle dogs each had 10 two-rooted premolars treated. In group 1 (n = 36 roots), 1 root/tooth had the canal conditioned with Primer Epiphany, filled with Epiphany sealer and Resilon core in 1 session, and coronally sealed with PhotacFil. In group 2 (n = 36 roots), the second root/tooth had the canal medicated with 2% chlorhexidine gel for 1 week and then filled and coronally sealed as in group 1. After 3 weeks, canals were exposed to the oral environment for 7 days, inoculated with isologous plaque, and coronally sealed. Negative controls treated as groups 1 and 2 remained sealed. Positive controls had canals unfilled and exposed. Seven months after inoculation, dogs were euthanized; jaw blocks processed for histologic examination; and periapical inflammation (PI) recorded as none, mild, or severe. In groups 1 and 2, severe PI occurred in 5 of 65 roots (8%) and mild PI in 18 of 65 roots (28%) with a significantly higher (P = .031) PI incidence in group 2 than in group 1. Negative controls had only mild PI in 9 of 29 roots (31%). Roots medicated with 2% chlorhexidine gel had mild PI significantly more (P = .009) than roots filled in 1 session (more than 2-fold). Intracanal medication with 2% chlorhexidine gel and root filling with Resilon/Epiphany did not effectively inhibit apical periodontitis subsequent to coronal inoculation. Copyright © 2014 American Association of Endodontists. All rights reserved.

Experimental root canal infections in conventional and germ-free mice.

PubMed

Sobrinho, A P; Barros, M H; Nicoli, J R; Carvalho, M A; Farias, L M; Bambirra, E A; Bahia, M G; Vieira, E C

1998-06-01

A small animal model was evaluated to study the interrelationships between microorganisms after their implantation in root canals (inferior central incisors) using germ-free (GF) and conventional (CV) mice. The selected microorganisms were: Porphyromonas endodontalis (ATCC 35406), Eubacterium lentum (ATCC 25559), Peptostreptococcus anaerobius (ATCC 27337), Fusobacterium nucleatum (ATCC 10953), Escherichia coli (ATCC 25922), and Enterococcus faecalis (ATCC 4083). Only P. anaerobius, E. coli, and E. faecalis, respectively, were able to colonize when inoculated alone into the root canal of both CV and GF mice. E. lentum, when inoculated alone colonized only in CV animals. P. endodontalis and F. nucleatum were unable to colonize in CV and GF animals after single inoculation. It is concluded that the experimental animal model presented herein is valuable for ecological studies of root canal infections and that only some strict anaerobic bacteria are able to colonize mice root canals when inoculated by themselves alone in pure culture.

Biofertilization with Azospirillum brasilense improves in vitro culture of Handroanthus ochraceus, a forestry, ornamental and medicinal plant.

PubMed

Llorente, Berta E; Alasia, María A; Larraburu, Ezequiel E

2016-01-25

Biofertilization with plant growth-promoting rhizobacteria is a potential alternative to plant productivity. Here, in vitro propagation of Handroanthus ochraceus (yellow lapacho), a forest crop with high economic and environmental value, was developed using the Azospirillum brasilense strains Cd and Az39 during rhizogenesis. Epicotiles of in vitro plantlets were multiplied in Woody Plant Medium (WPM). For rooting, elongated shoots were transferred to auxin-free Murashige-Skoog medium with Gamborg's vitamins and WPM, both at half salt concentration (½MSG and ½WPM), and inoculated with Cd or Az39 at the base of each shoot. Anatomical studies were performed using leaves cleared and stained with safranin for optical microscopy and leaves and roots metalized with gold-palladium for scanning electron microscopy (SEM). In ½WPM auxin-free medium, A. brasilense Cd inoculation produced 55% of rooting, increased root fresh and dry weight (45% and 77%, respectively), and led to lower stomata size and density with similar proportion of open and closed stomata. Both strains selectively increased the size or density of glandular trichomes in ½MSG. Moreover, bacteria were detected on the root surface by SEM. In conclusion, the difference in H. ochraceus response to A. brasilense inoculation depends on the strain and the plant culture media. Cd strain enhanced rooting in auxin-free ½WPM and produced plantlets with features similar to those expected in ex vitro plants. This work presents an innovative in vitro approach using beneficial plant-microorganism interaction as an ecologically compatible strategy in plant biotechnology. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of controlled inoculation with specific mycorrhizal fungi from the urban environment on growth and physiology of containerized shade tree species growing under different water regimes.

PubMed

Fini, Alessio; Frangi, Piero; Amoroso, Gabriele; Piatti, Riccardo; Faoro, Marco; Bellasio, Chandra; Ferrini, Francesco

2011-11-01

The aim of this work was to evaluate the effects of selected mycorrhiza obtained in the urban environment on growth, leaf gas exchange, and drought tolerance of containerized plants growing in the nursery. Two-year-old uniform Acer campestre L., Tilia cordata Mill., and Quercus robur L. were inoculated with a mixture of infected roots and mycelium of selected arbuscular (maple, linden) and/or ectomycorrhiza (linden, oak) fungi and grown in well-watered or water shortage conditions. Plant biomass and leaf area were measured 1 and 2 years after inoculation. Leaf gas exchange, chlorophyll fluorescence, and water relations were measured during the first and second growing seasons after inoculation. Our data suggest that the mycelium-based inoculum used in this experiment was able to colonize the roots of the tree species growing in the nursery. Plant biomass was affected by water shortage, but not by inoculation. Leaf area was affected by water regime and, in oak and linden, by inoculation. Leaf gas exchange was affected by inoculation and water stress. V(cmax) and J(max) were increased by inoculation and decreased by water shortage in all species. F(v)/F(m) was also generally higher in inoculated plants than in control. Changes in PSII photochemistry and photosynthesis may be related to the capacity of inoculated plants to maintain less negative leaf water potential under drought conditions. The overall data suggest that inoculated plants were better able to maintain physiological activity during water stress in comparison to non-inoculated plants.

Screenhouse and field persistence of nonpathogenic endophytic Fusarium oxysporum in Musa tissue culture plants.

PubMed

Paparu, Pamela; Dubois, Thomas; Gold, Clifford S; Niere, Björn; Adipala, Ekwamu; Coyne, Daniel

2008-04-01

Two major biotic constraints to highland cooking banana (Musa spp., genome group AAA-EA) production in Uganda are the banana weevil Cosmopolites sordidus and the burrowing nematode Radopholus similis. Endophytic Fusarium oxysporum strains inoculated into tissue culture banana plantlets have shown control of the banana weevil and the nematode. We conducted screenhouse and field experiments to investigate persistence in the roots and rhizome of two endophytic Fusarium oxysporum strains, V2w2 and III4w1, inoculated into tissue-culture banana plantlets of highland cooking banana cultivars Kibuzi and Nabusa. Re-isolation of F. oxysporum showed that endophyte colonization decreased faster from the rhizomes than from the roots of inoculated plants, both in the screenhouse and in the field. Whereas rhizome colonization by F. oxysporum decreased in the screenhouse (4-16 weeks after inoculation), root colonization did not. However, in the field (17-33 weeks after inoculation), a decrease was observed in both rhizome and root colonization. The results show a better persistence in the roots than rhizomes of endophytic F. oxysporum strains V2w2 and III4w1.

Short term effects of Glomus claroideum and Azospirillum brasilense on growth and root acid phosphatase activity of Carica papaya L. under phosphorus stress.

PubMed

Alarcón, Alejandro; Davies, Frederick T; Egilla, Johnatan N; Fox, Theodore C; Estrada-Luna, Arturo A; Ferrera-Cerrato, Ronald

2002-01-01

Arbuscular mycorrhizal fungi (AMF) are able to increase root enzymatic activity of acid and alkaline phosphatases. However, the role of AMF on phosphatase activity has not been reported in papaya (Carica papaya L.), which is frequently established at places with soil phosphorus (P) deficiencies. The goals of this research were to determine the effect of Glomus claroideum (Gc), and plant growth promoting rhizobacterium Azospirillum brasilense strain VS7 [Ab]) on root phosphatase activity and seedling growth of Carica papaya L. cv. Red Maradol under low P conditions. There were four treatments-colonization with: 1) Gc, 2) Ab, 3) Gc+Ab, and 4) non-inoculated seedlings. Plants were established in a coarse sand:sandy loam substrate under P-limitation (11 microg P ml(-1)), supplied with a modified Long Ashton Nutrient Solution. Seedling growth was severely reduced by low P. Gc+Ab inoculated plants had greater total dry matter and leaf area than non-colonized plants. Gc-inoculated plants had greater leaf area than non-colonized plants. Treatments did not differ in leaf area ratio, specific leaf area and, total chlorophyll content. There was a non-significant effect on stem relative growth rate with Gc and Gc+Ab plants. Mycorrhizal colonization enhanced the bacterial population 3.4-fold in the Gc+Ab treatment compared with the population quantified in Ab treatment. Soluble and extractable root acid phosphatase activity (RAPA) was higher in Gc inoculated plants. We discussed on the possible relation among both inoculated microorganisms and also with the P-limitation which plants were established.

Mitigation of salt stress in white clover (Trifolium repens) by Azospirillum brasilense and its inoculation effect.

PubMed

Khalid, Muhammad; Bilal, Muhammad; Hassani, Danial; Iqbal, Hafiz M N; Wang, Hang; Huang, Danfeng

2017-12-01

Salinity is one of the increasingly serious environmental problems worldwide for cultivating agricultural crops. The present study was aimed to ascertain the potential of beneficial soil bacterium Azospirillum brasilense to alleviate saline stress in Trifolium repens. Experimental plants (white clover) were grown from seeds and inoculated with or without A. brasilense bacterial strain supplemented with 0, 40, 80, or 120 mM NaCl into soil. The growth attributes including, shoot heights, root lengths, fresh and dry weights, leaf area and chlorophyll content were significantly enhanced in T. repens plants grown in A. brasilense inoculated soil than un-inoculated controls, particularly under elevated salinity conditions (40, 80 and 120 mM NaCl). Malondialdehyde content of leaf was recorded to be declined under saline conditions. Moreover, the K + /Na + ratio was also improved in bacterium-inoculated plants, since A. brasilense significantly reduced the root and shoot Na + level under high salty environment. Results revealed that soil inoculation with A. brasilense could significantly promote T. repens growth under both non-saline and saline environments, and this study might be extended to other vegetables and crops for the germination and growth enhancement.

Plant growth-promoting bacteria as inoculants in agricultural soils

PubMed Central

de Souza, Rocheli; Ambrosini, Adriana; Passaglia, Luciane M.P.

2015-01-01

Abstract Plant-microbe interactions in the rhizosphere are the determinants of plant health, productivity and soil fertility. Plant growth-promoting bacteria (PGPB) are bacteria that can enhance plant growth and protect plants from disease and abiotic stresses through a wide variety of mechanisms; those that establish close associations with plants, such as the endophytes, could be more successful in plant growth promotion. Several important bacterial characteristics, such as biological nitrogen fixation, phosphate solubilization, ACC deaminase activity, and production of siderophores and phytohormones, can be assessed as plant growth promotion (PGP) traits. Bacterial inoculants can contribute to increase agronomic efficiency by reducing production costs and environmental pollution, once the use of chemical fertilizers can be reduced or eliminated if the inoculants are efficient. For bacterial inoculants to obtain success in improving plant growth and productivity, several processes involved can influence the efficiency of inoculation, as for example the exudation by plant roots, the bacterial colonization in the roots, and soil health. This review presents an overview of the importance of soil-plant-microbe interactions to the development of efficient inoculants, once PGPB are extensively studied microorganisms, representing a very diverse group of easily accessible beneficial bacteria. PMID:26537605

Beauveria bassiana and Metarhizium anisopliae endophytically colonize cassava roots following soil drench inoculation

PubMed Central

Greenfield, Melinda; Gómez-Jiménez, María I.; Ortiz, Viviana; Vega, Fernando E.; Kramer, Matthew; Parsa, Soroush

2016-01-01

We investigated the fungal entomopathogens Beauveria bassiana and Metarhizium anisopliae to determine if endophytic colonization could be achieved in cassava. An inoculation method based on drenching the soil around cassava stem cuttings using conidial suspensions resulted in endophytic colonization of cassava roots by both entomopathogens, though neither was found in the leaves or stems of the treated cassava plants. Both fungal entomopathogens were detected more often in the proximal end of the root than in the distal end. Colonization levels of B. bassiana were higher when plants were sampled at 7–9 days post-inoculation (84%) compared to 47–49 days post-inoculation (40%). In contrast, the colonization levels of M. anisopliae remained constant from 7–9 days post-inoculation (80%) to 47–49 days post-inoculation (80%), which suggests M. anisopliae is better able to persist in the soil, or as an endophyte in cassava roots over time. Differences in colonization success and plant growth were found among the fungal entomopathogen treatments. PMID:27103778

Infection and colonization of rice seedlings by the plant growth-promoting bacterium Herbaspirillum seropedicae Z67.

PubMed

James, Euan K; Gyaneshwar, Prasad; Mathan, Natarajan; Barraquio, Wilfredo L; Reddy, Pallavolu M; Iannetta, Pietro P M; Olivares, Fabio L; Ladha, Jagdish K

2002-09-01

A beta-glucoronidase (GUS)-marked strain of Herbaspirillum seropedicae Z67 was inoculated onto rice seedling cvs. IR42 and IR72. Internal populations peaked at over 10(6) log CFU per gram of fresh weight by 5 to 7 days after inoculation (DAI) but declined to 10(3) to 10(4) log CFU per gram of fresh weight by 28 DAI. GUS staining was most intense on coleoptiles, lateral roots, and at the junctions of some of the main and lateral roots. Bacteria entered the roots via cracks at the points of lateral root emergence, with cv. IR72 appearing to be more aggressively infected than cv. IR42. H. seropedicae subsequently colonized the root intercellular spaces, aerenchyma, and cortical cells, with a few penetrating the stele to enter the vascular tissue. Xylem vessels in leaves and stems were extensively colonized at 2 DAI but, in later harvests (7 and 13 DAI), a host defense reaction was often observed. Dense colonies of H. seropedicae with some bacteria expressing nitrogenase Fe-protein were seen within leaf and stem epidermal cells, intercellular spaces, and substomatal cavities up until 28 DAI. Epiphytic bacteria were also seen. Both varieties showed nitrogenase activity but only with added C, and the dry weights of the inoculated plants were significantly increased. Only cv. IR42 showed a significant (approximately 30%) increase in N content above that of the uninoculated controls, and it also incorporated a significant amount of 15N2.

Effects of co-inoculation with arbuscular mycorrhizal fungi and rhizobia on fungal occupancy in chickpea root and nodule determined by real-time PCR.

PubMed

Tavasolee, Alireza; Aliasgharzad, Naser; Salehi, Gholam Reza; Mardi, Mohsen; Asgharzadeh, Ahmad; Akbarivala, Sepide

2011-08-01

Legume roots in nature are usually colonized with rhizobia and different arbuscular mycorrhizal fungi (AMF) species. Light microscopy that visualizes the presence of AMF in roots is not able to differentiate the ratio of each AMF species in the root and nodule tissues in mixed fungal inoculation. The purpose of this study was to characterize the dominant species of mycorrhiza in roots and nodules of plants co-inoculated with mycorrhizal fungi and rhizobial strains. Glomus intraradices (GI), Glomus mosseae (GM), their mix (GI + GM), and six Mesorhizobium ciceri strains were used to inoculate chickpea. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to assess occupancy of these fungal species in roots and nodules. Results showed that GI molecular ratio and relative density were higher than GM in both roots and nodules. These differences in molecular ratio and density between GI and GM in nodules were three folds higher than roots. The results suggested that M. ciceri strains have different effects on nodulation and mycorrhizal colonization pattern. Plants with bacterial S3 and S1 strains produced the highest root nodulation and higher fungal density in both the roots and nodules.

Effects of vesicular-arbuscular mycorrhizal (VAM) fungi on the seedling growth of three Pistacia species.

PubMed

Caglar, S; Akgun, A

2006-07-01

The experiment was undertaken to test the efficiency of inoculation of vesicular-arbuscular mycorrhizal (VAM) fungi on the seedling growth of three Pistacia species used as rootstocks. The stratified Pistacia seeds were inoculated with VAM fungi. The highest rate of inoculated roots was 96.7% in P. khinjuck seedlings with G. clarum and G. etunicatum, 83.3% in P. vera seedlings with G. caledonium and 73.3% in P. terebinthus seedlings with G. caledonium. Mycorrhizal inoculations improved seedling height only in P. terebinthus. Certain mycorrhizal inoculations increased the leaf N, but not P and K contents. Seedlings inoculated with G. caledonium had higher reducing sugar contents. It was concluded that pre-inoculated Pistacia seedlings could have a better growth in the harsh field conditions.

Deciphering composition and function of the root microbiome of a legume plant.

PubMed

Hartman, Kyle; van der Heijden, Marcel Ga; Roussely-Provent, Valexia; Walser, Jean-Claude; Schlaeppi, Klaus

2017-01-17

Diverse assemblages of microbes colonize plant roots and collectively function as a microbiome. Earlier work has characterized the root microbiomes of numerous plant species, but little information is available for legumes despite their key role in numerous ecosystems including agricultural systems. Legumes form a root nodule symbiosis with nitrogen-fixing Rhizobia bacteria and thereby account for large, natural nitrogen inputs into soils. Here, we describe the root bacteria microbiome of the legume Trifolium pratense combining culture-dependent and independent methods. For a functional understanding of individual microbiome members and their impact on plant growth, we began to inoculate root microbiome members alone or in combination to Trifolium roots. At a whole-root scale, Rhizobia bacteria accounted for ~70% of the root microbiome. Other enriched members included bacteria from the genera Pantoea, Sphingomonas, Novosphingobium, and Pelomonas. We built a reference stock of 200 bacteria isolates, and we found that they corresponded to ~20% of the abundant root microbiome members. We developed a microcosm system to conduct simplified microbiota inoculation experiments with plants. We observed that while an abundant root microbiome member reduced plant growth when inoculated alone, this negative effect was alleviated if this Flavobacterium was co-inoculated with other root microbiome members. The Trifolium root microbiome was dominated by nutrient-providing Rhizobia bacteria and enriched for bacteria from genera that may provide disease protection. First microbiota inoculation experiments indicated that individual community members can have plant growth compromising activities without being apparently pathogenic, and a more diverse root community can alleviate plant growth compromising activities of its individual members. A trait-based characterization of the reference stock bacteria will permit future microbiota manipulation experiments to decipher overall microbiome functioning and elucidate the biological mechanisms and interactions driving the observed effects. The presented reductionist experimental approach offers countless opportunities for future systematic and functional examinations of the plant root microbiome.

Expression profiles of defence related cDNAs in oil palm (Elaeis guineensis Jacq.) inoculated with mycorrhizae and Trichoderma harzianum Rifai T32.

PubMed

Tan, Yung-Chie; Wong, Mui-Yun; Ho, Chai-Ling

2015-11-01

Basal stem rot is one of the major diseases of oil palm (Elaies guineensis Jacq.) caused by pathogenic Ganoderma species. Trichoderma and mycorrhizae were proposed to be able to reduce the disease severity. However, their roles in improving oil palm defence system by possibly inducing defence-related genes in the host are not well characterized. To better understand that, transcript profiles of eleven putative defence-related cDNAs in the roots of oil palm inoculated with Trichoderma harzianum T32 and mycorrhizae at different time points were studied. Transcripts encoding putative Bowman-Birk protease inhibitor (EgBBI2) and defensin (EgDFS) increased more than 2 fold in mycorrhizae-treated roots at 6 weeks post inoculation (wpi) compared to those in controls. Transcripts encoding putative dehydrin (EgDHN), glycine-rich RNA binding protein (EgGRRBP), isoflavone reductase (EgIFR), type 2 ribosome inactivating protein (EgT2RIP), and EgDFS increased in the oil palm roots treated with T. harzianum at 6 and/or 12 wpi compared to those in the controls. Some of these genes were also expressed in oil palm roots treated with Ganoderma boninense. This study provides an insight of some defence-related genes induced by Trichoderma and mycorrhizae, and their roles as potential agents to boost the plant defence system. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

The effect of Piriformospora indica on the root development of maize (Zea mays L.) and remediation of petroleum contaminated soil.

PubMed

Zamani, Javad; Hajabbasi, Mohammad Ali; Alaie, Ebrahim; Sepehri, Mozhgan; Leuchtmann, Adrian; Schulin, Rainer

2016-01-01

As the depth of soil petroleum contamination can vary substantially under field conditions, a rhizotron experiment was performed to investigate the influence of endophyte, P. indica, on maize growth and degradation of petroleum components in a shallow and a deep-reaching subsurface layer of a soil. For control, a treatment without soil contamination was also included. The degree in contamination and the depth to which it extended had a strong effect on the growth of the plant roots. Contaminated soil layers severely inhibited root growth thus many roots preferred to bypass the shallow contaminated layer and grow in the uncontaminated soil. While the length and branching pattern of these roots were similar to those of uncontaminated treatment. Inoculation of maize with P. indica could improve root distribution and root and shoot growth in all three contamination treatments. This inoculation also enhanced petroleum degradation in soil, especially in the treatment with deep-reaching contamination, consequently the accumulation of petroleum hydrocarbons (PAHs) in the plant tissues were increased.

A morel improved growth and suppressed Fusarium infection in sweet corn.

PubMed

Yu, Dan; Bu, Fangfang; Hou, Jiaojiao; Kang, Yongxiang; Yu, Zhongdong

2016-12-01

A post-fire morel collected from Populus simonii stands in Mt. Qingling was identified as Morchella crassipes Mes-20 by using nuclear ribosomal DNA internal transcribed spacer phylogeny. It was inoculated into sweet corn to observe colonized roots in purified culture and in greenhouse experiments. The elongation and maturation zones of sweet corn were remarkably colonized at the cortex intercellular and intracellular cells, vessel cells, and around the Casparian strip, forming ectendomycorrhiza-like structures. Colonization was also observed in the zone of cell division proximal to the root cap. Greenhouse assays with sweet corn showed that this morel stimulated the development of the root system and significantly increased the dry root biomass. M. crassipes also significantly reduced the incidence of Fusarium verticillioides in the kernels of mature ears when inoculated into young ears before Fusarium inoculation and prevented Fusarium infection in corn ears compared with that of the control in the greenhouse. When grown under axenic conditions, M. crassipes produced the phytohormones abscisic acid, indole-3-acetic acid, and salicylic acid. The benefits to plants elicited by M. crassipes may result from these phytohormones which may improve the drought resistance, biomass growth and resistance to Fusarium.

A new species of Burkholderia isolated from sugarcane roots promotes plant growth

PubMed Central

Paungfoo-Lonhienne, Chanyarat; Lonhienne, Thierry G A; Yeoh, Yun Kit; Webb, Richard I; Lakshmanan, Prakash; Chan, Cheong Xin; Lim, Phaik-Eem; Ragan, Mark A; Schmidt, Susanne; Hugenholtz, Philip

2014-01-01

Sugarcane is a globally important food, biofuel and biomaterials crop. High nitrogen (N) fertilizer rates aimed at increasing yield often result in environmental damage because of excess and inefficient application. Inoculation with diazotrophic bacteria is an attractive option for reducing N fertilizer needs. However, the efficacy of bacterial inoculants is variable, and their effective formulation remains a knowledge frontier. Here, we take a new approach to investigating diazotrophic bacteria associated with roots using culture-independent microbial community profiling of a commercial sugarcane variety (Q208A) in a field setting. We first identified bacteria that were markedly enriched in the rhizosphere to guide isolation and then tested putative diazotrophs for the ability to colonize axenic sugarcane plantlets (Q208A) and promote growth in suboptimal N supply. One isolate readily colonized roots, fixed N2 and stimulated growth of plantlets, and was classified as a new species, Burkholderia australis sp. nov. Draft genome sequencing of the isolate confirmed the presence of nitrogen fixation. We propose that culture-independent identification and isolation of bacteria that are enriched in rhizosphere and roots, followed by systematic testing and confirming their growth-promoting capacity, is a necessary step towards designing effective microbial inoculants. PMID:24350979

The Rhizobium sp. strain NGR234 systemically suppresses arbuscular mycorrhizal root colonization in a split-root system of barley (Hordeum vulgare).

PubMed

Khaosaad, Thanasan; Staehelin, Christian; Steinkellner, Siegrid; Hage-Ahmed, Karin; Ocampo, Juan Antonio; Garcia-Garrido, Jose Manuel; Vierheilig, Horst

2010-11-01

Nitrogen-fixing bacteria (rhizobia) form a nodule symbiosis with legumes, but also induce certain effects on non-host plants. Here, we used a split-root system of barley to examine whether inoculation with Rhizobium sp. strain NGR234 on one side of a split-root system systemically affects arbuscular mycorrhizal (AM) root colonization on the other side. Mutant strains of NGR234 deficient in Nod factor production (strain NGRΔnodABC), perception of flavonoids (strain NGRΔnodD1) and secretion of type 3 effector proteins (strain NGRΩrhcN) were included in this study. Inoculation resulted in a systemic reduction of AM root colonization with all tested strains. However, the suppressive effect of strain NGRΩrhcN was less pronounced. Moreover, levels of salicylic acid, an endogenous molecule related to plant defense, were increased in roots challenged with rhizobia. These data indicate that barley roots perceived NGR234 and that a systemic regulatory mechanism of AM root colonization was activated. The suppressive effect appears to be Nod factor independent, but enhanced by type 3 effector proteins of NGR234. Copyright © Physiologia Plantarum 2010.

Arbuscular mycorrhizal fungi affect both penetration and further life stage development of root-knot nematodes in tomato.

PubMed

Vos, Christine; Geerinckx, Katleen; Mkandawire, Rachel; Panis, Bart; De Waele, Dirk; Elsen, Annemie

2012-02-01

The root-knot nematode Meloidogyne incognita poses a worldwide threat to agriculture, with an increasing demand for alternative control options since most common nematicides are being withdrawn due to environmental concerns. The biocontrol potential of arbuscular mycorrhizal fungi (AMF) against plant-parasitic nematodes has been demonstrated, but the modes of action remain to be unraveled. In this study, M. incognita penetration of second-stage juveniles at 4, 8 and 12 days after inoculation was compared in tomato roots (Solanum lycopersicum cv. Marmande) pre-colonized or not by the AMF Glomus mosseae. Further life stage development of the juveniles was also observed in both control and mycorrhizal roots at 12 days, 3 weeks and 4 weeks after inoculation by means of acid fuchsin staining. Penetration was significantly lower in mycorrhizal roots, with a reduction up to 32%. Significantly lower numbers of third- and fourth-stage juveniles and females accumulated in mycorrhizal roots, at a slower rate than in control roots. The results show for the first time that G. mosseae continuously suppresses root-knot nematodes throughout their entire early infection phase of root penetration and subsequent life stage development.

The influences of Cr-tolerant rhizobacteria in phytoremediation and attenuation of Cr (VI) stress in agronomic sunflower (Helianthus annuus L.).

PubMed

Bahadur, Ali; Ahmad, Rizwan; Afzal, Aftab; Feng, Huyuan; Suthar, Vishandas; Batool, Asfa; Khan, Aman; Mahmood-Ul-Hassan, Muhammad

2017-07-01

Chromium contamination of agronomic soil has to turn into a serious global problem. This research was pointed to assess the effects of three Cr-tolerant rhizobacteria (SS1, SS3, and SS6) on sunflower growth and heavy metal uptake under Cr smog i.e. 20, 30 and 40 ppm using K 2 Cr 2 O 7 . Root promotion assay and pot experiment were conducted to investigate and evaluate the effects of Cr tolerance rhizobacteria and Cr accumulation capacity of sunflower. From root promotion assay non-significant variation was observed in the root length between SS1 and SS3 compared with un-inoculated whereas SS6 enhanced the root length in the absence and presence of chromium. In addition, inoculation with rhizobacteria alleviated the Cr concentration and endorsed plant growth by enhancing Cr accumulation in sunflower. At different Cr levels, the Cr concentration in shoot was improved by each rhizobacterium though their difference was non-significant with each other, while the percentage increase was half as the Cr level doubled. Different rhizobacterium inoculation significantly (P < 0.05) affected the physiological and morphological characteristics of sunflower and increased the plant height, stem diameter, head diameter, grain yield, oil content of seeds, and total biomass, and among them, SS6 observed best followed by SS1 and SS3 comparing with un-inoculated. Our study illustrates an assessment about Cr-tolerant bacteria and their influences and recommends that these bacteria can effectively be used for crop improvement which provides a potential approach for Cr phytoremediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of Meloidogyne incognita on Growth and Storage-Root Formation of Cassava (Manihot esculenta)

PubMed Central

Makumbi-Kidza, N. N.; Speijer, P. R.; Sikora, R. A.

2000-01-01

Two-node cuttings of cassava cultivar SS4 were inoculated with 1,000 infective juveniles of Meloidogyne incognita at 1, 14, 40, 70, 88, and 127 days after planting (DAP). Plant growth and root damage were assessed at 150 DAP. Meloidogyne incognita significantly reduced the number of storageroots formed in plants inoculated at 14, 40, 70, and 88 DAP and the total weight of storage-roots in plants inoculated at 1, 14, 40, 70, and 88 DAP, compared to uninoculated plants. Individual storage-root weight and plant height were not affected by M. incognita. Storage-root formation in cassava is initiated when plants are 1 to 2 months old. The results of this experiment indicate that, at this time, young cassava plants are most prone to root-knot nematode damage in terms of storage-root formation. The production loss caused by M. incognita to young SS4 plants was due to a reduction of storage-root number rather than a reduction in individual storage-root weight. PMID:19270997

Pathogenicity of Leptographium Species Associated with Loblolly Pine Decline

Treesearch

L. G. Eckhardt; J. P. Jones; Kier D. Klepzig

2004-01-01

Freshly lifted seedlings and 21-year-old trees of loblolly pine were wound-inoculated with Leptographium species recovered from the soil and/or roots of trees with loblolly decline symptoms in central Alabama. Seedlings inoculated with L. procerum in the greenhouse produced significantly fewer root initials and a smaller root mass than control...

Bacterial Compatibility in Combined Inoculations Enhances the Growth of Potato Seedlings.

PubMed

Santiago, Christine D; Yagi, Shogo; Ijima, Motoaki; Nashimoto, Tomoya; Sawada, Maki; Ikeda, Seishi; Asano, Kenji; Orikasa, Yoshitake; Ohwada, Takuji

2017-03-31

The compatibility of strains is crucial for formulating bioinoculants that promote plant growth. We herein assessed the compatibility of four potential bioinoculants isolated from potato roots and tubers (Sphingomonas sp. T168, Streptomyces sp. R170, Streptomyces sp. R181, and Methylibium sp. R182) that were co-inoculated in order to improve plant growth. We screened these strains using biochemical tests, and the results obtained showed that R170 had the highest potential as a bioinoculant, as indicated by its significant ability to produce plant growth-promoting substances, its higher tolerance against NaCl (2%) and AlCl 3 (0.01%), and growth in a wider range of pH values (5.0-10.0) than the other three strains. Therefore, the compatibility of R170 with other strains was tested in combined inoculations, and the results showed that the co-inoculation of R170 with T168 or R182 synergistically increased plant weight over un-inoculated controls, indicating the compatibility of strains based on the increased production of plant growth promoters such as indole-3-acetic acid (IAA) and siderophores as well as co-localization on roots. However, a parallel test using strain R181, which is the same Streptomyces genus as R170, showed incompatibility with T168 and R182, as revealed by weaker plant growth promotion and a lack of co-localization. Collectively, our results suggest that compatibility among bacterial inoculants is important for efficient plant growth promotion, and that R170 has potential as a useful bioinoculant, particularly in combined inoculations that contain compatible bacteria.

Effect of plant growth-promoting rhizobacteria inoculation on cadmium (Cd) uptake by Eruca sativa.

PubMed

Kamran, Muhammad Aqeel; Syed, Jabir Hussain; Eqani, Syed Ali Musstjab Akber Shah; Munis, Muhammad Farooq Hussain; Chaudhary, Hassan Javed

2015-06-01

Microbe-assisted phyto-remediation approach is widely applied and appropriate choice to reduce the environmental risk of heavy metals originated from contaminated soils. The present study was designed to screen out the nested belongings of Eruca sativa plants and Pseudomonas putida (ATCC 39213) at varying cadmium (Cd) levels and their potential to deal with Cd uptake from soils. We carried out pot trial experiment by examining the soil containing E. sativa seedlings either treated with P. putida and/or untreated plants subjected to three different levels (ppm) of Cd (i.e., 150, 250, and 500). In all studied cases, we observed an increase in Cd uptake for E. sativa plants inoculated with P. putida than those of un-inoculated plants. Cd toxicity was assessed by recording different parameters including stunted shoot growth, poor rooting, and Cd residual levels in the plants that were not inoculated with P. putida. Significant difference (p < 0.05) of different growth parameters for inoculated vs non-inoculated plants was observed at all given treatments. However, among the different treatments, E. sativa exhibited increased values for different growth parameters (except proline contents) at lower Cd levels than those of their corresponding higher levels, shoot length (up to 27 %), root length (up to 32 %), whole fresh plant (up to 40 %), dry weight (up to 22 %), and chlorophyll contents (up to 26 %). Despite the hyperaccumulation of Cd in whole plant of E. sativa, P. putida improved the plant growth at varying levels of Cd supply than those of associated non-inoculated plants. Present results indicated that inoculation with P. putida enhanced the Cd uptake potential of E. sativa and favors the healthy growth under Cd stress.

Does co-inoculation of Lactuca serriola with endophytic and arbuscular mycorrhizal fungi improve plant growth in a polluted environment?

PubMed

Ważny, Rafał; Rozpądek, Piotr; Jędrzejczyk, Roman J; Śliwa, Marta; Stojakowska, Anna; Anielska, Teresa; Turnau, Katarzyna

2018-04-01

Phytoremediation of polluted sites can be improved by co-inoculation with mycorrhizal and endophytic fungi. In this study, the effects of single- and co-inoculation of Lactuca serriola with an arbuscular mycorrhizal (AM) fungus, Rhizoglomus intraradices, and endophytic fungi, Mucor sp. or Trichoderma asperellum, on plant growth, vitality, toxic metal accumulation, sesquiterpene lactone production and flavonoid concentration in the presence of toxic metals were evaluated. Inoculation with the AM fungus increased biomass yield of the plants grown on non-polluted and polluted substrate. Co-inoculation with the AM fungus and Mucor sp. resulted in increased biomass yield of plants cultivated on the polluted substrate, whereas co-inoculation with T. asperellum and the AM fungus increased plant biomass on the non-polluted substrate. In the presence of Mucor sp., mycorrhizal colonization and arbuscule richness were increased in the non-polluted substrate. Co-inoculation with the AM fungus and Mucor sp. increased Zn concentration in leaves and roots. The concentration of sesquiterpene lactones in plant leaves was decreased by AM fungus inoculation in both substrates. Despite enhanced host plant costs caused by maintaining symbiosis with numerous microorganisms, interaction of wild lettuce with both mycorrhizal and endophytic fungi was more beneficial than that with a single fungus. The study shows the potential of double inoculation in unfavourable environments, including agricultural areas and toxic metal-polluted areas.

Growth, cadmium uptake and accumulation of maize (Zea mays L.) under the effects of arbuscular mycorrhizal fungi.

PubMed

Liu, Lingzhi; Gong, Zongqiang; Zhang, Yulong; Li, Peijun

2014-12-01

The effects of three arbuscular mycorrhizal fungi isolates on Cd uptake and accumulation by maize (Zea mays L.) were investigated in a planted pot experiment. Plants were inoculated with Glomus intraradices, Glomus constrictum and Glomus mosseae at three different Cd concentrations. The results showed that root colonization increased with Cd addition during a 6-week growth period, however, the fungal density on roots decreased after 9-week growth in the treatments with G. constrictum and G. mosseae isolates. The percentage of mycorrhizal colonization by the three arbuscular mycorrhizal fungi isolates ranged from 22.7 to 72.3%. Arbuscular mycorrhizal fungi inoculations decreased maize biomass especially during the first 6-week growth before Cd addition, and this inhibitory effect was less significant with Cd addition and growth time. Cd concentrations and uptake in maize plants increased with arbuscular mycorrhizal fungi colonization at low Cd concentration (0.02 mM): nonetheless, it decreased at high Cd concentration (0.20 mM) after 6-week growth period. Inoculation with G. constrictum isolates enhanced the root Cd concentrations and uptake, but G. mosseae isolates showed the opposite results at high Cd concentration level after 9 week growth period, as compared to non-mycorrhizal plants. In conclusion, maize plants inoculated with arbuscular mycorrhizal fungi were less sensitive to Cd stress than uninoculated plants. G. constrictum isolates enhanced Cd phytostabilization and G. mosseae isolates reduced Cd uptake in maize (Z. mays L.).

Arbuscular mycorrhizal fungi differ in their ability to regulate the expression of phosphate transporters in maize (Zea mays L.).

PubMed

Tian, Hui; Drijber, Rhae A; Li, Xiaolin; Miller, Daniel N; Wienhold, Brian J

2013-08-01

Previous studies have found that some phosphate (Pi) starvation inducible transporter genes are downregulated and arbuscular mycorrhizal (AM) inducible Pi transporter genes are upregulated in maize roots associated with the fungus Glomus intraradices. However, little is known about the functional diversity of different AM fungal species in influencing the expression of Pi transporters in maize roots. Here, we studied the expression of two Pi transporter genes ZEAma:Pht1;3 (Pi starvation inducible) and ZEAma:Pht1;6 (AM inducible) in maize root colonized by different AM fungal inoculants. Non-mycorrhizal maize, maize colonized by Glomus deserticola (CA113), Glomus intraradices (IA506), Glomus mosseae (CA201), Gigaspora gigantea (MN922A) and the co-inoculation of all four species were established. The expression patterns of the two genes were quantified using real-time, reverse transcription polymerase chain reaction. The expression level of ZEAma:Pht1;6 was 26-135 times higher in AM plants than in non-mycorrhizal maize roots, whereas the expression level of ZEAma:Pht1;3 was five to 44 times lower in AM plants than in non-mycorrhizal plants. Expression of the two genes differed with inoculation treatment, and increasing the diversity of AM fungi in maize roots led to greater expression of ZEAma:Pht1;6 as well as Pi uptake in shoots. The expression of ZEAma:Pht1;6 was significantly positively correlated with AM colonization rate, concentration of AM biomarkers in maize roots, Pi uptake and dry weight of shoot, but negatively correlated with the expression of ZEAma:Pht1;3. Addition of Pi fertilizer at a low concentration significantly increased the expression of ZEAma:Pht1;6 but had no effect on the expression of ZEAma:Pht1;3.

Effect of Oryzalin and 1,1-Dimethylpiperidinium Chloride on Cotton and Tomato Roots Infected with the Root-knot Nematode, Meloidogyne incognita

PubMed Central

Orum, T. V.; Bartels, P. G.; McClure, M. A.

1979-01-01

Oryzalin (3,5-dinitro-N4,N4-dipropyl-sulfanilamide) and BAS 083 (l,l-dimethylpiperdinium chloride) reduced root-knot infection in tomato roots when respectively applied as a soil drench at 20 ppm and 10,000 ppm. Oryzalin reduced knot counts with various intervals between treatment and inoculation. BAS 083 reduced knot counts only when applied before inoculation. Oryzalin was shown not to be a contact nematicide, and BAS 083 was only a weak one. Neither compound reduced penetration by infective larvae. Postinfection reduction in knot counts by Oryzalin and BAS 083 resulted, in part, from activation of natural defense mechanisms of the host. Giant-cell development in cotton roots inoculated with nematodes was inhibited by Oryzalin. Lateral root development was inhibited by BAS 083. PMID:19305533

Endophytic fungi occurring in fennel, lettuce, chicory, and celery--commercial crops in southern Italy.

PubMed

D'Amico, Margherita; Frisullo, Salvatore; Cirulli, Matteo

2008-01-01

The occurrence of endophytic fungi in fennel, lettuce, chicory, and celery crops was investigated in southern Italy. A total of 186 symptomless plants was randomly collected and sampled at the stage of commercial ripeness. Fungal species of Acremonium, Alternaria, Fusarium, and Plectosporium were detected in all four crops; Plectosporium tabacinum was the most common in all crop species and surveyed sites. The effect of eight endophytic isolates (five belonging to Plectosporium tabacinum and three to three species of Acremonium) inoculated on lettuce plants grown in gnotobiosis was assessed by recording plant height, root length and dry weight, collar diameter, root necrosis, and leaf yellowing. P. tabacinum and three species of Acremonium, inoculated on gnotobiotically grown lettuce plants, showed pathogenic activity that varied with the fungal isolate. Lettuce plants inoculated with the isolates Ak of Acremonium kiliense, Ac of Acremonium cucurbitacearum, and P35 of P. tabacinum showed an increased root growth, compared to the non-inoculated control. The high frequency of P. tabacinum isolation recorded in lettuce plants collected in Bari and Metaponto, and in fennel plants from Foggia agricultural districts, suggests a relationship not only between a crop species and P. tabacinum, but also between the occurrence of the endophyte and the crop rotation history of the soil.

Drought response of Mucuna pruriens (L.) DC. inoculated with ACC deaminase and IAA producing rhizobacteria.

PubMed

Saleem, Aansa Rukya; Brunetti, Cecilia; Khalid, Azeem; Della Rocca, Gianni; Raio, Aida; Emiliani, Giovanni; De Carlo, Anna; Mahmood, Tariq; Centritto, Mauro

2018-01-01

Drought is one of the major constraints limiting agricultural production worldwide and is expected to increase in the future. Limited water availability causes significant effects to plant growth and physiology. Plants have evolved different traits to mitigate the stress imposed by drought. The presence of plant growth-promoting rhizobacteria (PGPR) could play an important role in improving plant performances and productivity under drought. These beneficial microorganisms colonize the rhizosphere of plants and increase drought tolerance by lowering ethylene formation. In the present study, we demonstrate the potential to improve the growth of velvet bean under water deficit conditions of two different strains of PGPR with ACCd (1-Aminocyclopropane-1-Carboxylate deaminase) activity isolated from rainfed farming system. We compared uninoculated and inoculated plants with PGPR to assess: a) photosynthetic performance and biomass; b) ACC content and ethylene emission from leaves and roots; c) leaf isoprene emission. Our results provided evidence that under drought conditions inoculation with PGPR containing the ACCd enzyme could improve plant growth compared to untreated plants. Ethylene emission from roots and leaves of inoculated velvet bean plants was significantly lower than uninoculated plants. Moreover, isoprene emission increased with drought stress progression and was higher in inoculated plants compared to uninoculated counterparts. These findings clearly illustrate that selected PGPR strains isolated from rainfed areas could be highly effective in promoting plant growth under drought conditions by decreasing ACC and ethylene levels in plants.

Drought response of Mucuna pruriens (L.) DC. inoculated with ACC deaminase and IAA producing rhizobacteria

PubMed Central

Khalid, Azeem; Raio, Aida; Emiliani, Giovanni; De Carlo, Anna; Mahmood, Tariq

2018-01-01

Drought is one of the major constraints limiting agricultural production worldwide and is expected to increase in the future. Limited water availability causes significant effects to plant growth and physiology. Plants have evolved different traits to mitigate the stress imposed by drought. The presence of plant growth-promoting rhizobacteria (PGPR) could play an important role in improving plant performances and productivity under drought. These beneficial microorganisms colonize the rhizosphere of plants and increase drought tolerance by lowering ethylene formation. In the present study, we demonstrate the potential to improve the growth of velvet bean under water deficit conditions of two different strains of PGPR with ACCd (1-Aminocyclopropane-1-Carboxylate deaminase) activity isolated from rainfed farming system. We compared uninoculated and inoculated plants with PGPR to assess: a) photosynthetic performance and biomass; b) ACC content and ethylene emission from leaves and roots; c) leaf isoprene emission. Our results provided evidence that under drought conditions inoculation with PGPR containing the ACCd enzyme could improve plant growth compared to untreated plants. Ethylene emission from roots and leaves of inoculated velvet bean plants was significantly lower than uninoculated plants. Moreover, isoprene emission increased with drought stress progression and was higher in inoculated plants compared to uninoculated counterparts. These findings clearly illustrate that selected PGPR strains isolated from rainfed areas could be highly effective in promoting plant growth under drought conditions by decreasing ACC and ethylene levels in plants. PMID:29447189

Expression of animal anti-apoptotic gene Ced-9 enhances tolerance during Glycine max L.-Bradyrhizobium japonicum interaction under saline stress but reduces nodule formation.

PubMed

Robert, Germán; Muñoz, Nacira; Melchiorre, Mariana; Sánchez, Federico; Lascano, Ramiro

2014-01-01

The mechanisms by which the expression of animal cell death suppressors in economically important plants conferred enhanced stress tolerance are not fully understood. In the present work, the effect of expression of animal antiapoptotic gene Ced-9 in soybean hairy roots was evaluated under root hairs and hairy roots death-inducing stress conditions given by i) Bradyrhizobium japonicum inoculation in presence of 50 mM NaCl, and ii) severe salt stress (150 mM NaCl), for 30 min and 3 h, respectively. We have determined that root hairs death induced by inoculation in presence of 50 mM NaCl showed characteristics of ordered process, with increased ROS generation, MDA and ATP levels, whereas the cell death induced by 150 mM NaCl treatment showed non-ordered or necrotic-like characteristics. The expression of Ced-9 inhibited or at least delayed root hairs death under these treatments. Hairy roots expressing Ced-9 had better homeostasis maintenance, preventing potassium release; increasing the ATP levels and controlling the oxidative damage avoiding the increase of reactive oxygen species production. Even when our results demonstrate a positive effect of animal cell death suppressors in plant cell ionic and redox homeostasis under cell death-inducing conditions, its expression, contrary to expectations, drastically inhibited nodule formation even under control conditions.

Arbuscular mycorrhizal fungal inoculation increases phenolic synthesis in clover roots via hydrogen peroxide, salicylic acid and nitric oxide signaling pathways.

PubMed

Zhang, Rui-Qin; Zhu, Hong-Hui; Zhao, Hai-Quan; Yao, Qing

2013-01-01

Arbuscular mycorrhizal fungi can increase the host resistance to pathogens via promoted phenolic synthesis, however, the signaling pathway responsible for it still remains unclear. In this study, in order to reveal the signaling molecules involved in this process, we inoculated Trifolium repense L. with an arbuscular mycorrhizal fungus (AMF), Glomus mosseae, and monitored the contents of phenolics and signaling molecules (hydrogen peroxide (H(2)O(2)), salicylic acid (SA), and nitric oxide (NO)) in roots, measured the activities of l-phenylalanine ammonia-lyase (PAL) and nitric oxide synthase (NOS), and the expression of pal and chs genes. Results demonstrated that AMF colonization promoted the phenolic synthesis, in parallel with the increase in related enzyme activity and gene expression. Meanwhile, the accumulation of all three signaling molecules was also up-regulated by AMF. This study suggested that AMF increased the phenolic synthesis in roots probably via signaling pathways of H(2)O(2), SA and NO in a signaling cascade. Copyright © 2012 Elsevier GmbH. All rights reserved.

Monitoring the colonization of sugarcane and rice plants by the endophytic diazotrophic bacterium Gluconacetobacter diazotrophicus marked with gfp and gusA reporter genes.

PubMed

Rouws, L F M; Meneses, C H S G; Guedes, H V; Vidal, M S; Baldani, J I; Schwab, S

2010-09-01

To evaluate the colonization process of sugarcane plantlets and hydroponically grown rice seedlings by Gluconacetobacter diazotrophicus strain PAL5 marked with the gusA and gfp reporter genes. Sugarcane plantlets inoculated in vitro with PAL5 carrying the gfp::gusA plasmid pHRGFPGUS did not present green fluorescence, but beta-glucuronidase (GUS)-stained bacteria could be observed inside sugarcane roots. To complement this existing inoculation methodology for micropropagated sugarcane with a more rapid colonization assay, we employed hydroponically grown gnotobiotic rice seedlings to study PAL5-plant interaction. PAL5 could be isolated from the root surface (10(8) CFU g(-1)) and from surface-disinfected root and stem tissues (10(4) CFU g(-1)) of inoculated plants, suggesting that PAL5 colonized the internal plant tissues. Light microscopy confirmed the presence of bacteria inside the root tissue. After inoculation of rice plantlets with PAL5 marked with the gfp plasmid pHRGFPTC, bright green fluorescent bacteria could be seen colonizing the rice root surface, mainly at the sites of lateral root emergence, at root caps and on root hairs. The plasmids pHRGFPGUS and pHRGFPTC are valid tools to mark PAL5 and monitor the colonization of micropropagated sugarcane and hydroponic rice seedlings. These tools are of use to: (i) study PAL5 mutants affected in bacteria-plant interactions, (ii) monitor plant colonization in real time and (iii) distinguish PAL5 from other bacteria during the study of mixed inoculants.

In vitro propagation of fraser photinia using Azospirillum-mediated root development.

PubMed

Llorente, Berta E; Larraburu, Ezequiel E

2013-01-01

Fraser photinia (Photinia × fraseri Dress.) is a woody plant of high ornamental value. The traditional propagation system for photinia is by rooting apical cuttings using highly concentrated auxin treatments. However, photinia micropropagation is an effective alternative to traditional in vivo propagation which is affected by the seasonal supply of cuttings, the long time required to obtain new plants, and the difficulties in rooting some clones.A protocol for in vitro propagation of fraser photinia using the plant growth-promoting ability of some rhizobacteria is described here. Bacterial inoculation is a new tool in micropropagation protocols that improves plant development in in vitro culture. Shoots culture on a medium containing MS macro- and microelements, Gamborg's vitamins (BM), N (6)-benzyladenine (BA, 11.1 μM), and gibberellic acid (1.3 μM) produce well-established explants. Proliferation on BM medium supplemented with 4.4 μM BA results in four times the number of shoots per initial shoot that develops monthly. Consequently, there is a continuous supply of plant material since shoot production is independent of season. Azospirillum brasilense inoculation, after 49.2 μM indole-3-butyric acid pulse treatment, stimulates early rooting of photinia shoots and produces significant increase in root fresh and dry weights, root surface area, and shoot fresh and dry weights in comparison with controls. Furthermore, inoculated in vitro photinia plants show anatomical and morphological changes that might lead to better adaptation in ex vitro conditions after transplanting, compared with the control plants.

[Arbuscular mycorrhizal symbiosis influences the biological effects of nano-ZnO on maize].

PubMed

Wang, Wei-Zhong; Wang, Fa-Yuan; Li, Shuai; Liu, Xue-Qin

2014-08-01

Engineered nanoparticles (ENPs) can be taken up and accumulated in plants, then enter human bodies via food chain, and thus cause potential health risk. Arbuscular mycorrhizal fungi form mutualistic symbioses with the majority of higher plants in terrestrial ecosystems, and potentially influence the biological effects of ENPs. The present greenhouse pot culture experiment studied the effects of inoculation with or without arbuscular mycorrhizal fungus Acaulospora mellea on growth and nutritional status of maize under different nano-ZnO levels (0, 500, 1 000, 2000 and 3 000 mg x kg(-1)) artificially added into soil. Results showed that with the increasing nano-ZnO levels in soil, mycorrhizal colonization rate and biomass of maize plants showed a decreasing trend, total root length, total surface area and total volume reduced, while Zn concentration and uptake in plants gradually increased, and P, N, K, Fe, and Cu uptake in shoots all decreased. Compared with the controls, arbuscular mycorrhizal inoculation improved the growth and P, N and K nutrition of maize, enhanced total root length, total surface area and total volume, and increased Zn allocation to roots when nano-ZnO was added. Our results firstly show that nano-ZnO in soil induces toxicity to arbuscular mycorrhizae, while arbuscular mycorrhizal inoculation can alleviate its toxicity and play a protective role in plants.

Investigating the ability of Pseudomonas fluorescens UW4 to reduce cadmium stress in Lactuca sativa via an intervention in the ethylene biosynthetic pathway.

PubMed

Albano, Lucas J; Macfie, Sheila M

2016-12-01

A typical plant response to any biotic or abiotic stress, including cadmium (Cd), involves increased ethylene synthesis, which causes senescence of the affected plant part. Stressed plants can experience reduced ethylene and improved growth if they are inoculated with bacteria that have the enzyme ACC deaminase, which metabolizes the ethylene precursor ACC (1-aminocyclopropane-1-carboxylate). We investigated whether one such bacterium, Pseudomonas fluorescens UW4, reduces the production of ethylene and improves the growth of lettuce (Lactuca sativa) sown in Cd-contaminated potting material (PRO-MIX® BX). Plants were inoculated with the wild-type P. fluorescens UW4 or a mutant strain that cannot produce ACC deaminase. Cadmium-treated plants contained up to 50 times more Cd than did control plants. In noninoculated plants, Cd induced a 5-fold increase in ethylene concentration. The wild-type bacterium prevented Cd-induced reductions in root biomass but there was no relationship between Cd treatment and ethylene production in inoculated plants. In contrast, when the concentration of ethylene was plotted against the extent of bacterial colonization of the roots, increased colonization with wild-type P. fluorescens UW4 was associated with 20% less ethylene production. Ours is the first study to show that the protective effect of this bacterium is proportional to the quantity of bacteria on the root surface.

Acetylene reduction (nitrogen fixation) associated with corn inoculated with Spirillum.

PubMed

Barber, L E; Tjepkema, J D; Russell, S A; Evans, H J

1976-07-01

Sorghum and corn breeding lines were grown in soil in field and greenhouse experiments with and without an inoculum of N2-fixing in Spirillum strains from Brazil. Estimated rates of N2 fixation associated with field-grown corn and sorghum plants were less than 4 g of N2/ha per day. The mean estimated N2-fixation rates determined on segments of roots from corn inoculated with Spirillum and grown in the greenhouse at 24 to 27 degrees C were 15 g of N2/ha per day (16 inbreds), 25 g of N2/ha per day (six hybrids), and 165 g of N2/ha per day for one hybird which was heavily inoculated. The corresponding mean rates determined from measurements of in situ cultures of the same series of corn plants (i.e., 16 inbreds, six hybrids, and one heavily inoculated hybrid) were 0.4, 2.3, and 1.1 g of N2/ha per day, respectively. Lower rates of C2H2 reduction were associated with control corn cultures which had been treated with autoclaved Spirillum than with cultures inoculated with live Spirillum. No C2H2 reduction was detected in plant cultures treated with ammonium nitrate. Numbers of nitrogen-fixing bacteria on excised roots of corn plants increased an average of about 30-fold during an overnight preincubation period, and as a result acetylene reduction assays of root samples after preincubation failed to serve as a valid basis for estimating N2 fixation by corn in pot cultures. Plants grown without added nitrogen either with or without inoculum exhibited severe symptoms of nitrogen deficiency and in most cases produced significantly less dry weight than those supplied with fixed nitrogen. Although substantial rates of C2H2 reduction by excised corn roots were observed after preincubation under limited oxygen, the yield and nitrogen content of inoculated plants and the C2H2-reduction rates by inoculated pot cultures of corn, in situ, provided no evidence of appreciable N2 fixation.

Effect of Soil Water Potential on Growth of Apple Trees Infected with Pratylenchus penetrans

PubMed Central

Jaffee, B. A.; Mai, W. F.

1979-01-01

Malling-Merton 106 apple rootstocks inoculated with Pratylenchus penetrans, or uninoculated, were grown in a growth chamber in pots of loamy sand maintained at two moisture levels, 0 to -0.4 bar or 0 to -10 bars. Either inoculation or low soil moisture suppressed shoot growth and increased root necrosis. However, the nematode-soil moisture interaction was not significant. PMID:19305552

Effects of arbuscular mycorrhizal fungi on seedling growth and development of two wetland plants, Bidens frondosa L., and Eclipta prostrata (L.) L., grown under three levels of water availability.

PubMed

Stevens, Kevin J; Wall, Christopher B; Janssen, Joel A

2011-05-01

To identify the importance of arbuscular mycorrhizal fungi (AMF) colonizing wetland seedlings following flooding, we assessed the effects of AMF on seedling establishment of two pioneer species, Bidens frondosa and Eclipta prostrata grown under three levels of water availability and ask: (1) Do inoculated seedlings differ in growth and development from non-inoculated plants? (2) Are the effects of inoculation and degree of colonization dependent on water availability? (3) Do plant responses to inoculation differ between two closely related species? Inoculation had no detectable effects on shoot height, or plant biomass but did affect biomass partitioning and root morphology in a species-specific manner. Shoot/root ratios were significantly lower in non-inoculated E. prostrata plants compared with inoculated plants (0.381 ± 0.066 vs. 0.683 ± 0.132). Root length and surface area were greater in non-inoculated E. prostrata (259.55 ± 33.78 cm vs. 194.64 ± 27.45 cm and 54.91 ± 7.628 cm(2) vs. 46.26 ± 6.8 cm(2), respectively). Inoculation had no detectable effect on B. frondosa root length, volume, or surface area. AMF associations formed at all levels of water availability. Hyphal, arbuscular, and vesicular colonization levels were greater in dry compared with intermediate and flooded treatments. Measures of mycorrhizal responsiveness were significantly depressed in E. prostrata compared with B. frondosa for total fresh weight (-0.3 ± 0.18 g vs. 0.06 ± 0.06 g), root length (-0.78 ± 0.28 cm vs.-0.11 ± 0.07 cm), root volume (-0.49 ± 0.22 cm(3) vs. 0.06 ± 0.07 cm(3)), and surface area (-0.59 ± 0.23 cm(2) vs.-0.03 ± 0.08 cm(2)). Given the disparity in species response to AMF inoculation, events that alter AMF prevalence in wetlands could significantly alter plant community structure by directly affecting seedling growth and development.

Spore associated bacteria regulates maize root K+/Na+ ion homeostasis to promote salinity tolerance during arbuscular mycorrhizal symbiosis.

PubMed

Selvakumar, Gopal; Shagol, Charlotte C; Kim, Kiyoon; Han, Seunggab; Sa, Tongmin

2018-06-05

The interaction between arbuscular mycorrhizal fungi (AMF) and AMF spore associated bacteria (SAB) were previously found to improve mycorrhizal symbiotic efficiency under saline stress, however, the information about the molecular basis of this interaction remain unknown. Therefore, the present study aimed to investigate the response of maize plants to co-inoculation of AMF and SAB under salinity stress. The co-inoculation of AMF and SAB significantly improved plant dry weight, nutrient content of shoot and root tissues under 25 or 50 mM NaCl. Importantly, co-inoculation significantly reduced the accumulation of proline in shoots and Na + in roots. Co-inoculated maize plants also exhibited high K + /Na + ratios in roots at 25 mM NaCl concentration. Mycorrhizal colonization significantly positively altered the expression of ZmAKT2, ZmSOS1, and ZmSKOR genes, to maintain K + and Na + ion homeostasis. Confocal laser scanning microscope (CLSM) view showed that SAB were able to move and localize into inter- and intracellular spaces of maize roots and were closely associated with the spore outer hyaline layer. These new findings indicate that co-inoculation of AMF and SAB effectively alleviates the detrimental effects of salinity through regulation of SOS pathway gene expression and K + /Na + homeostasis to improve maize plant growth.

Differential growth responses of Brachypodium distachyon genotypes to inoculation with plant growth promoting rhizobacteria.

PubMed

do Amaral, Fernanda P; Pankievicz, Vânia C S; Arisi, Ana Carolina M; de Souza, Emanuel M; Pedrosa, Fabio; Stacey, Gary

2016-04-01

Plant growth promoting rhizobacteria (PGPR) can associate and enhance the growth of important crop grasses. However, in most cases, the molecular mechanisms responsible for growth promotion are not known. Such research could benefit by the adoption of a grass model species that showed a positive response to bacterial inoculation and was amenable to genetic and molecular research methods. In this work we inoculated different genotypes of the model grass Brachypodium distachyon with two, well-characterized PGPR bacteria, Azospirillum brasilense and Herbaspirillum seropedicae, and evaluated the growth response. Plants were grown in soil under no nitrogen or with low nitrogen (i.e., 0.5 mM KNO3). A variety of growth parameters (e.g., shoot height, root length, number of lateral roots, fresh and dry weight) were measured 35 days after inoculation. The data indicate that plant genotype plays a very important role in determining the plant response to PGPR inoculation. A positive growth response was observed with only four genotypes grown under no nitrogen and three genotypes tested under low nitrogen. However, in contrast, relatively good root colonization was seen with most genotypes, as measured by drop plate counting and direct, microscopic examination of roots. In particular, the endophytic bacteria H. seropedicae showed strong epiphytic and endophytic colonization of roots.

Bacillus pumilus ES4: candidate plant growth-promoting bacterium to enhance establishment of plants in mine tailings

PubMed Central

de-Bashan, Luz E.; Hernandez, Juan-Pablo; Bashan, Yoav; Maier, Raina

2014-01-01

Three plant growth-promoting bacteria (PGPB; Bacillus pumilus ES4, B. pumilus RIZO1, and Azospirillum brasilense Cd) were tested for their ability to enhance plant growth and development of the native Sonoran Desert shrub quailbush (Atriplex lentiformis) and for their effect on the native bacterial community in moderately acidic, high-metal content (AHMT) and in neutral, low metal content natural tailings (NLMT) in controlled greenhouse experiments. Inoculation of quailbush with all three PGPB significantly enhanced plant growth parameters, such as germination, root length, dry weight of shoots and roots, and root/shoot ratio in both types of tailings. The effect of inoculation on the indigenous bacterial community by the most successful PGPB Bacillus pumilus ES4 was evaluated by denaturating gradient gel electrophoresis (PCR-DGGE) fingerprinting and root colonization was followed by specific fluorescent in situ hybridization (FISH). Inoculation with this strain significantly changed the bacterial community over a period of 60 days. FISH analysis showed that the preferred site of colonization was the root tips and root elongation area. This study shows that inoculation of native perennial plants with PGPB can be used for developing technologies for phytostabilizing mine tailings. PMID:25009362

Effect of Azotobacter vinelandii and compatible solutes on germination wheat seeds and root concentrations of sodium and potassium under salt stress.

PubMed

Silini, A; Silini-Chérif, H; Ghoul, M

2012-02-01

The effect of plant growth-promoting Rhizobacteria (PGPR) and exogenous application of compatible solutes on seed germination and root concentrations of sodium and potassium of two wheat varieties (Triticum durum L.) were evaluated under saline stress. In this experiment, Azotobacter vinelandii strain DSM85, glycine betaine and proline were used. Inoculated seeds for each variety were placed on Whatman paper in 9 cm Petri dishes containing 15 mL of distilled water or NaCl solutions at various concentrations (control, 100, 200, 300 mM) supplemented with or without glycine betaine (GB) or proline at 5 mM. The results indicated that addition of proline (5 mM) stimulated the production of indol acetic acid and the growth of A. vinelandii at 200 and 300 mM NaCl, respectively. The germination rate index and the germination final percentage decreased significantly (p < 0.05) with increasing salinity level. The germination was significantly diminished at 300 mM with significant variation among varieties and Waha variety had higher germination percentage than Bousselam variety. Inoculation of seeds by A. vinelandii and exogenous application of proline had significantly positive effect on the germination at this concentration of NaCl. The rate of accumulation of Na+ in roots was important at 100 mM and increased at 200 mM. The concentration of K+ decreased when salinity increased. The effect of inoculation or inoculation with proline decreased the accumulation of Na' and reduced the loss of K+ under salt stress. From the present study we can conclude that the use of A. vinelandii strain DSM85 and external application of low concentrations of proline on seeds might be considered as a strategy for the protection of plants under saline stress.

Genotypic variation in the response of chickpea to arbuscular mycorrhizal fungi and non-mycorrhizal fungal endophytes.

PubMed

Bazghaleh, Navid; Hamel, Chantal; Gan, Yantai; Tar'an, Bunyamin; Knight, Joan Diane

2018-04-01

Plant roots host symbiotic arbuscular mycorrhizal (AM) fungi and other fungal endophytes that can impact plant growth and health. The impact of microbial interactions in roots may depend on the genetic properties of the host plant and its interactions with root-associated fungi. We conducted a controlled condition experiment to investigate the effect of several chickpea (Cicer arietinum L.) genotypes on the efficiency of the symbiosis with AM fungi and non-AM fungal endophytes. Whereas the AM symbiosis increased the biomass of most of the chickpea cultivars, inoculation with non-AM fungal endophytes had a neutral effect. The chickpea cultivars responded differently to co-inoculation with AM fungi and non-AM fungal endophytes. Co-inoculation had additive effects on the biomass of some cultivars (CDC Corrine, CDC Anna, and CDC Cory), but non-AM fungal endophytes reduced the positive effect of AM fungi on Amit and CDC Vanguard. This study demonstrated that the response of plant genotypes to an AM symbiosis can be modified by the simultaneous colonization of the roots by non-AM fungal endophytes. Intraspecific variations in the response of chickpea to AM fungi and non-AM fungal endophytes indicate that the selection of suitable genotypes may improve the ability of crop plants to take advantage of soil ecosystem services.

Effect of ryegrass (Lolium perenne L.) roots inoculation using different arbuscular mycorrhizal fungi (AMF) species on sorption of iron-cyanide (Fe-CN) complexes

NASA Astrophysics Data System (ADS)

Sut, Magdalena; Boldt-Burisch, Katja; Raab, Thomas

2016-04-01

Soils and groundwater on sites of the former Manufactured Gas Plants (MGPs) are contaminated with various complex iron-cyanides (Fe-CN). Phytoremediation is a promising tool in stabilization and remediation of Fe-CN affected soils, however, it can be a challenging task due to extreme adverse and toxic conditions. Phytoremediation may be enhanced via rhizosphere microbial activity, which can cooperate on the degradation, transformation and uptake of the contaminants. Recently, increasing number of scientist reports improved plants performance in the removal of toxic compounds with the support of arbuscular mycorrhizae fungi (AMF). Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations, were used to study the effect of ryegrass roots (Lolium perenne L.) inoculation with Rhizophagus irregularis and a mixture of Rhizophagus irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum on Fe-CN sorption. Results indicated significantly higher colonization of R. irregularis than for the mixture of AMF species on ryegrass roots. Sorption experiments revealed significantly higher reduction of total CN and free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study indicates contribution of AM fungi in phytoremediation of Fe-CN contaminated soil.

Fusarium oxysporum mediates systems metabolic reprogramming of chickpea roots as revealed by a combination of proteomics and metabolomics.

PubMed

Kumar, Yashwant; Zhang, Limin; Panigrahi, Priyabrata; Dholakia, Bhushan B; Dewangan, Veena; Chavan, Sachin G; Kunjir, Shrikant M; Wu, Xiangyu; Li, Ning; Rajmohanan, Pattuparambil R; Kadoo, Narendra Y; Giri, Ashok P; Tang, Huiru; Gupta, Vidya S

2016-07-01

Molecular changes elicited by plants in response to fungal attack and how this affects plant-pathogen interaction, including susceptibility or resistance, remain elusive. We studied the dynamics in root metabolism during compatible and incompatible interactions between chickpea and Fusarium oxysporum f. sp. ciceri (Foc), using quantitative label-free proteomics and NMR-based metabolomics. Results demonstrated differential expression of proteins and metabolites upon Foc inoculations in the resistant plants compared with the susceptible ones. Additionally, expression analysis of candidate genes supported the proteomic and metabolic variations in the chickpea roots upon Foc inoculation. In particular, we found that the resistant plants revealed significant increase in the carbon and nitrogen metabolism; generation of reactive oxygen species (ROS), lignification and phytoalexins. The levels of some of the pathogenesis-related proteins were significantly higher upon Foc inoculation in the resistant plant. Interestingly, results also exhibited the crucial role of altered Yang cycle, which contributed in different methylation reactions and unfolded protein response in the chickpea roots against Foc. Overall, the observed modulations in the metabolic flux as outcome of several orchestrated molecular events are determinant of plant's role in chickpea-Foc interactions. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Bioaccumulation of nickel by E. sativa and role of plant growth promoting rhizobacteria (PGPRs) under nickel stress.

PubMed

Kamran, Muhammad Aqeel; Eqani, Syed Ali Musstjab Akber Shah; Bibi, Sadia; Xu, Ren-Kou; Amna; Monis, Muhammad Farooq Hussain; Katsoyiannis, Athanasios; Bokhari, Habib; Chaudhary, Hassan Javed

2016-04-01

Phytoremediation potential of plants can be enhanced in association with microbes. Further, many plant growth-promoting rhizobacteria can improve growth under stress. The present study was conducted to investigate the effect of Pseudomonas putida (P. putida) on nickel (Ni) uptake and on growth of Eruca sativa (E. sativa). Three different levels of Ni (low; 150 ug/g, medium; 250 ug/g and high; 500 ug/g) were applied to the soil containing E. sativa seedlings, with or without P. putida. Ni-toxicity was measured by metamorphic parameters including shoot length, root length, biomass, chlorophyll and proline and Ni contents. Inoculation with P. putida increased 34% and 41% in root and shoot length and 38% and 24% in fresh, dry weight respectively, as compared to non-inoculated plants. Similarly, Ni uptake increased by up to 46% following P. putida inoculation as compared to non-inoculated plants. Indole acetic acid, siderophore and 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity in the growing media enhanced growth and Ni uptake in E. sativa. The present results offer insight on Plant Growth Promoting Rhizobacteria (PGPR), such as P. putida, for the potential to enhance the plant growth by inhibiting the adverse effects of Ni in E. sativa. Copyright © 2016 Elsevier Inc. All rights reserved.

Bioaugmentation with cadmium-resistant plant growth-promoting rhizobacteria to assist cadmium phytoextraction by Helianthus annuus.

PubMed

Prapagdee, Benjaphorn; Chanprasert, Maesinee; Mongkolsuk, Skorn

2013-07-01

Micrococcus sp. MU1 and Klebsiella sp. BAM1, the cadmium-resistant plant growth-promoting rhizobacteria (PGPR), produce high levels of indole-3-acetic acid (IAA) during the late stationary phase of their growth. The ability of PGPR to promote root elongation, plant growth and cadmium uptake in sunflowers (Helianthus annuus) was evaluated. Both species of bacteria were able to remove cadmium ions from an aqueous solution and enhanced cadmium mobilization in contaminated soil. Micrococcus sp. and Klebsiella sp. use aminocyclopropane carboxylic acid as a nitrogen source to support their growth, and the minimum inhibitory concentrations of cadmium for Micrococcus sp. and Klebsiella sp. were 1000 and 800mM, respectively. These bacteria promoted root elongation in H. annuus seedlings in both the absence and presence of cadmium compared to uninoculated seedlings. Inoculation with these bacteria was found to increase the root lengths of H. annuus that had been planted in cadmium-contaminated soil. An increase in dry weight was observed for H. annuus inoculated with Micrococcus sp. Moreover, Micrococcus sp. enhanced the accumulation of cadmium in the root and leaf of H. annuus compared to untreated plants. The highest cadmium accumulation in the whole plant was observed when the plants were treated with EDTA following the treatment with Micrococcus sp. In addition, the highest translocation of cadmium from root to the above-ground tissues of H. annuus was found after treatment with Klebsiella sp. in the fourth week after planting. Our results show that plant growth and cadmium accumulation in H. annuus was significantly enhanced by cadmium-resistant PGPRs, and these bacterial inoculants are excellent promoters of phytoextraction for the rehabilitation of heavy metal-polluted environments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Belowground Inoculation With Arbuscular Mycorrhizal Fungi Increases Local and Systemic Susceptibility of Rice Plants to Different Pest Organisms

PubMed Central

Bernaola, Lina; Cosme, Marco; Schneider, Raymond W.; Stout, Michael

2018-01-01

Plants face numerous challenges from both aboveground and belowground stressors, and defend themselves against harmful insects and microorganisms in many ways. Because plant responses to biotic stresses are not only local but also systemic, belowground interactions can influence aboveground interactions in both natural and agricultural ecosystems. Arbuscular mycorrhizal fungi (AMF) are soilborne organisms that form symbiotic associations with many plant roots and are thought to play a central role in plant nutrition, growth, and fitness. In the present study, we focused on the influence of AMF on rice defense against pests. We inoculated rice plants with AMF in several field and greenhouse experiments to test whether the interaction of AMF with rice roots changes the resistance of rice against two chewing insects, the rice water weevil (Lissorhoptrus oryzophilus Kuschel, RWW) and the fall armyworm (Spodoptera frugiperda, FAW), and against infection by sheath blight (Rhizoctonia solani, ShB). Both in field and greenhouse experiments, the performance of insects and the pathogen on rice was enhanced when plants were inoculated with AMF. In the field, inoculating rice plants with AMF resulted in higher numbers of RWW larvae on rice roots. In the greenhouse, more RWW first instars emerged from AMF-colonized rice plants than from non-colonized control plants. Weight gains of FAW larvae were higher on rice plants treated with AMF inoculum. Lesion lengths and susceptibility to ShB infection were higher in rice plants colonized by AMF. Although AMF inoculation enhanced the growth of rice plants, the nutritional analyses of root and shoot tissues indicated no major increases in the concentrations of nutrients in rice plants colonized by AMF. The large effects on rice susceptibility to pests in the absence of large effects on plant nutrition suggest that AMF colonization influences other mechanisms of susceptibility (e.g., defense signaling processes). This study represents the first study conducted in the U.S. in rice showing AMF-induced plant susceptibility to several antagonists that specialize on different plant tissues. Given the widespread occurrence of AMF, our findings will help to provide a different perspective into the causal basis of rice systemic resistance/susceptibility to insects and pathogens. PMID:29922319

Belowground Inoculation With Arbuscular Mycorrhizal Fungi Increases Local and Systemic Susceptibility of Rice Plants to Different Pest Organisms.

PubMed

Bernaola, Lina; Cosme, Marco; Schneider, Raymond W; Stout, Michael

2018-01-01

Plants face numerous challenges from both aboveground and belowground stressors, and defend themselves against harmful insects and microorganisms in many ways. Because plant responses to biotic stresses are not only local but also systemic, belowground interactions can influence aboveground interactions in both natural and agricultural ecosystems. Arbuscular mycorrhizal fungi (AMF) are soilborne organisms that form symbiotic associations with many plant roots and are thought to play a central role in plant nutrition, growth, and fitness. In the present study, we focused on the influence of AMF on rice defense against pests. We inoculated rice plants with AMF in several field and greenhouse experiments to test whether the interaction of AMF with rice roots changes the resistance of rice against two chewing insects, the rice water weevil ( Lissorhoptrus oryzophilus Kuschel, RWW) and the fall armyworm ( Spodoptera frugiperda , FAW), and against infection by sheath blight ( Rhizoctonia solani , ShB). Both in field and greenhouse experiments, the performance of insects and the pathogen on rice was enhanced when plants were inoculated with AMF. In the field, inoculating rice plants with AMF resulted in higher numbers of RWW larvae on rice roots. In the greenhouse, more RWW first instars emerged from AMF-colonized rice plants than from non-colonized control plants. Weight gains of FAW larvae were higher on rice plants treated with AMF inoculum. Lesion lengths and susceptibility to ShB infection were higher in rice plants colonized by AMF. Although AMF inoculation enhanced the growth of rice plants, the nutritional analyses of root and shoot tissues indicated no major increases in the concentrations of nutrients in rice plants colonized by AMF. The large effects on rice susceptibility to pests in the absence of large effects on plant nutrition suggest that AMF colonization influences other mechanisms of susceptibility (e.g., defense signaling processes). This study represents the first study conducted in the U.S. in rice showing AMF-induced plant susceptibility to several antagonists that specialize on different plant tissues. Given the widespread occurrence of AMF, our findings will help to provide a different perspective into the causal basis of rice systemic resistance/susceptibility to insects and pathogens.

Mitigation of soil N2O emission by inoculation with a mixed culture of indigenous Bradyrhizobium diazoefficiens

NASA Astrophysics Data System (ADS)

Akiyama, Hiroko; Hoshino, Yuko Takada; Itakura, Manabu; Shimomura, Yumi; Wang, Yong; Yamamoto, Akinori; Tago, Kanako; Nakajima, Yasuhiro; Minamisawa, Kiwamu; Hayatsu, Masahito

2016-09-01

Agricultural soil is the largest source of nitrous oxide (N2O), a greenhouse gas. Soybean is an important leguminous crop worldwide. Soybean hosts symbiotic nitrogen-fixing soil bacteria (rhizobia) in root nodules. In soybean ecosystems, N2O emissions often increase during decomposition of the root nodules. Our previous study showed that N2O reductase can be used to mitigate N2O emission from soybean fields during nodule decomposition by inoculation with nosZ++ strains [mutants with increased N2O reductase (N2OR) activity] of Bradyrhizobium diazoefficiens. Here, we show that N2O emission can be reduced at the field scale by inoculation with a mixed culture of indigenous nosZ+ strains of B. diazoefficiens USDA110 group isolated from Japanese agricultural fields. Our results also suggested that nodule nitrogen is the main source of N2O production during nodule decomposition. Isolating nosZ+ strains from local soybean fields would be more applicable and feasible for many soybean-producing countries than generating mutants.

Mitigation of soil N2O emission by inoculation with a mixed culture of indigenous Bradyrhizobium diazoefficiens

PubMed Central

Akiyama, Hiroko; Hoshino, Yuko Takada; Itakura, Manabu; Shimomura, Yumi; Wang, Yong; Yamamoto, Akinori; Tago, Kanako; Nakajima, Yasuhiro; Minamisawa, Kiwamu; Hayatsu, Masahito

2016-01-01

Agricultural soil is the largest source of nitrous oxide (N2O), a greenhouse gas. Soybean is an important leguminous crop worldwide. Soybean hosts symbiotic nitrogen-fixing soil bacteria (rhizobia) in root nodules. In soybean ecosystems, N2O emissions often increase during decomposition of the root nodules. Our previous study showed that N2O reductase can be used to mitigate N2O emission from soybean fields during nodule decomposition by inoculation with nosZ++ strains [mutants with increased N2O reductase (N2OR) activity] of Bradyrhizobium diazoefficiens. Here, we show that N2O emission can be reduced at the field scale by inoculation with a mixed culture of indigenous nosZ+ strains of B. diazoefficiens USDA110 group isolated from Japanese agricultural fields. Our results also suggested that nodule nitrogen is the main source of N2O production during nodule decomposition. Isolating nosZ+ strains from local soybean fields would be more applicable and feasible for many soybean-producing countries than generating mutants. PMID:27633524

Endophytes and their Potential to Deal with Co-contamination of Organic Contaminants (Toluene) and Toxic Metals (Nickel) during Phytoremediation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weyens, N.; van der Lelie, D.; Truyens, S.

The aim was to investigate if engineered endophytes that are capable of degrading organic contaminants, and deal with or ideally improve uptake and translocation of toxic metals, can improve phytoremediation of mixed organic-metal pollution. As a model system, yellow lupine was inoculated with the endophyte Burkholderia cepacia VM1468 possessing (a) the pTOM-Bu61 plasmid, coding for constitutive toluene/TCE degradation, and (b) the chromosomally inserted ncc-nre Ni resistance/sequestration system. As controls, plants were inoculated with B. vietnamiensis BU61 (pTOM-Bu61) and B. cepacia BU72 (containing the ncc-nre Ni resistance/sequestration system). Plants were exposed to mixes of toluene and Ni. Only inoculation with B.more » cepacia VM1468 resulted in decreased Ni and toluene phytotoxicity, as measured by a protective effect on plant growth and decreased activities of enzymes involved in antioxidative defence (catalase, guaiacol peroxidase, superoxide dismutase) in the roots. Besides, plants inoculated with B. cepacia VM1468 and B. vietnamiensis BU61 released less toluene through the leaves than non-inoculated plants and those inoculated with B. cepacia BU72. Ni-uptake in roots was slightly increased for B. cepacia BU72 inoculated plants. These results indicate that engineered endophytes have the potential to assist their host plant to deal with co-contamination of toxic metals and organic contaminants during phytoremediation.« less

Can Cd translocation in Oryza sativa L. be attenuated by arbuscular mycorrhizal fungi in the presence of EDTA?

PubMed

Huang, Xiaochen; An, Guangnan; Zhu, Shishu; Wang, Li; Ma, Fang

2018-04-01

Arbuscular mycorrhizal (AM) fungi play an important role in plant tolerance of heavy metal contamination. In this study, a pot experiment was conducted to illustrate the effects of the two AM fungi species Funneliformis mosseae (Fm) and Rhizophagus irregularis (Ri) on plant growth of Oryza sativa L. either with or without ethylenediamine tetraacetate (EDTA) addition and during exposure to five Cd concentrations (in the range of 0-5 mg kg -1 ). The results showed that Fm inoculation achieved greater mycorrhizal colonization and mycorrhizal dependency indexes than Ri inoculation. In addition, the effects of AM fungi on Cd biosorption and translocation in rice were also investigated in the presence of EDTA. Despite cooperative adsorption, the Freundlich isotherm could describe the biosorption effects of Cd on rice roots regardless of AM fungi inoculation or EDTA addition. Cd concentrations in mycorrhizal roots increased but decreased in mycorrhizal shoots in contrast to the control treatment. Although EDTA addition negatively inhibited the uptake of Cd to mycorrhizal shoots, lower translocation factor (TF) and bioconcentration factor (BCF) were still observed in treatments with EDTA compared to control treatment. Our findings suggest that Ri and Fm inoculation enhanced Cd immobilization in the roots, thus preventing Cd entry into the food chain during exposure to low and high Cd stress, respectively.

Variable effects of arbuscular mycorrhizal fungal inoculation on physiological and molecular measures of root and stomatal conductance of diverse Medicago truncatula accessions.

PubMed

Watts-Williams, Stephanie J; Cavagnaro, Timothy R; Tyerman, Stephen D

2018-06-22

Association with arbuscular mycorrhizal fungi (AMF) can impact on plant water relations; mycorrhizal plants can exhibit increased stomatal conductance (g s ) and root hydraulic conductance (normalised to root dry weight, L o ), and altered expression of aquaporins (AQP). Many factors regulate such responses, however, plant intraspecific diversity effects have yet to be explored. Twenty geographically diverse accessions of Medicago truncatula were inoculated with the AMF Funneliformis mosseae or mock-inoculated, and grown under well-watered conditions. Biomass, g s , shoot nutrient concentrations and mycorrhizal colonisation were measured in all accessions, and L o and gene expression in five accessions. The diverse accessions varied in physiology and gene expression; some accessions were also larger or had higher g s when colonised by F. mosseae. In the five accessions, L o was higher in two accessions when colonised by AMF, and also maintained within a much smaller range than the mock-inoculated plants. Expression of MtPIP1 correlated with both g s and L o , and when plants were more than 3% colonised, mycorrhizal colonisation correlated with L o . Accession and AMF treatments had profound effects on M. truncatula, including several measures of plant water relations. Correlations between response variables, especially between molecular and physiological variables, across genotypes, highlight the findings of this study. This article is protected by copyright. All rights reserved.

Response of Pinus ponderosa Seedlings to Stylet-Bearing Nematodes

PubMed Central

Viglierchio, D. R.

1979-01-01

Of 12 stylet-bearing nematodes used for inoculations, Pratylenchus penetrans, P. brachyurus, P. vulnus, Ditylenchus destructor, Meloidogyne incognita, M. javanica, and M. hapla reproduced on Pinus ponderosa, while Xiphinema index, Aphelenchus avenae, Paratylenehus neoamblycephalus, Tylenchulus semipenetrans, and Macroposthonia xenoplax did not. P. vulnus, P. brachyurus, P. penetrans, A. avenae, D. destructor, T. semipenetrans, and P. neoamblycephalus significantly suppressed both the shoot and root wet weights of ponderosa pine seedlings obtained from stands in five different locations. X. index significantly suppressed root wet weights, M. xenoplax siguificantly suppressed shoot wet weight, and M. incognita, M. javanica, and M. hapla suppressed neither at the inoculation levels used. Injurious nematodes tended to suppress root growth more than shoot growth. Seedlings from two locations produced greater shoot growth wet weight than did seedlings from the other three locations. The more injurious nematodes tended to cause an increase in the water content of shoots. Frequency analyses of seedling population shoot-root ratios indicated that ponderosa pine seedlings could be selected for better shoot-root ratios as well as for resistance to several pathogenic nematodes. PMID:19300659

Bacteria–zinc co-localization implicates enhanced synthesis of cysteine-rich peptides in zinc detoxification when Brassica juncea is inoculated with Rhizobium leguminosarum

PubMed Central

Adediran, Gbotemi A; Ngwenya, Bryne T; Mosselmans, J Frederick W; Heal, Kate V

2016-01-01

Some plant growth promoting bacteria (PGPB) are enigmatic in enhancing plant growth in the face of increased metal accumulation in plants. Since most PGPB colonize the plant root epidermis, we hypothesized that PGPB confer tolerance to metals through changes in speciation at the root epidermis. We employed a novel combination of fluorophore-based confocal laser scanning microscopic imaging and synchrotron based microscopic X-ray fluorescence mapping with X-ray absorption spectroscopy to characterize bacterial localization, zinc (Zn) distribution and speciation in the roots of Brassica juncea grown in Zn contaminated media (400 mg kg−1 Zn) with the endophytic Pseudomonas brassicacearum and rhizospheric Rhizobium leguminosarum. PGPB enhanced epidermal Zn sequestration relative to PGBP-free controls while the extent of endophytic accumulation depended on the colonization mode of each PGBP. Increased root accumulation of Zn and increased tolerance to Zn was associated predominantly with R. leguminosarum and was likely due to the coordination of Zn with cysteine-rich peptides in the root endodermis, suggesting enhanced synthesis of phytochelatins or glutathione. Our mechanistic model of enhanced Zn accumulation and detoxification in plants inoculated with R. leguminosarum has particular relevance to PGPB enhanced phytoremediation of soils contaminated through mining and oxidation of sulphur-bearing Zn minerals or engineered nanomaterials such as ZnS. PMID:26263508

Azospirillum spp. from native forage grasses in Brazilian Pantanal floodplain: biodiversity and plant growth promotion potential.

PubMed

Souza, Mayara S T; de Baura, Valter A; Santos, Sandra A; Fernandes-Júnior, Paulo Ivan; Reis Junior, Fábio B; Marques, Maria Rita; Paggi, Gecele Matos; da Silva Brasil, Marivaine

2017-04-01

A sustainable alternative to improve yield and the nutritive value of forage is the use of plant growth-promoting bacteria (PGPB) that release nutrients, synthesize plant hormones and protect against phytopathogens (among other mechanisms). Azospirillum genus is considered an important PGPB, due to the beneficial effects observed when inoculated in several plants. The aim of this study was to evaluate the diversity of new Azospirillum isolates and select bacteria according to the plant growth promotion ability in three forage species from the Brazilian Pantanal floodplain: Axonopus purpusii, Hymenachne amplexicaulis and Mesosetum chaseae. The identification of bacterial isolates was performed using specific primers for Azospirillum in PCR reactions and partial sequencing of the 16S rRNA and nifH genes. The isolates were evaluated in vitro considering biological nitrogen fixation (BNF) and indole-3-acetic acid (IAA) production. Based on the results of BNF and IAA, selected isolates and two reference strains were tested by inoculation. At 31 days after planting the plant height, shoot dry matter, shoot protein content and root volume were evaluated. All isolates were able to fix nitrogen and produce IAA, with values ranging from 25.86 to 51.26 mg N mL -1 and 107-1038 µmol L -1 , respectively. The inoculation of H. amplexicaulis and A. purpusii increased root volume and shoot dry matter. There were positive effects of Azospirillum inoculation on Mesosetum chaseae regarding plant height, shoot dry matter and root volume. Isolates MAY1, MAY3 and MAY12 were considered promising for subsequent inoculation studies in field conditions.

Root endophytic fungus Piriformospora indica affected growth, cadmium partitioning and chlorophyll fluorescence of sunflower under cadmium toxicity.

PubMed

Shahabivand, Saleh; Parvaneh, Azar; Aliloo, Ali Asghar

2017-11-01

Cadmium (Cd) pollution in the soil threatens the quality of environmental health, and deleteriously affects physiological activities of crops. Symbiosis of endophytic fungi with various plants is a promising manner to improving numerous plant characteristics and remediating heavy metal-polluted soils. In this pot experiment, the influence of root endophyte fungus Piriformospora indica on growth, physiological parameters and organs Cd accumulation in sunflower cv. Zaria plants under the toxic levels of Cd (0, 40, 80 and 120mg/kg soil) were studied. Increasing Cd concentration in the soil reduced growth parameters, chlorophyll (Chl) a and Chl b contents, and Fv/Fm and ETR (electron transport rate) values, but increased root, stem and leaf Cd accumulation, and proline content. The presence of P. indica significantly enhanced growth, Chl a, Chl b and proline contents, and Fv/Fm and ETR values. Compared to non-inoculated ones, P. indica-inoculated plants had higher Cd accumulation in root, whereas lower Cd accumulation in stem and leaf. The present study strongly supports the established ability of P. indica to alleviate Cd toxicity by improving the physiological status in sunflower. Furthermore, this endophyte fungus can be useful for Cd phyto-stabilization in sunflower roots in contaminated soils. Copyright © 2017 Elsevier Inc. All rights reserved.

Accessing inoculation methods of maize and wheat with Azospirillum brasilense.

PubMed

Fukami, Josiane; Nogueira, Marco Antonio; Araujo, Ricardo Silva; Hungria, Mariangela

2016-03-01

The utilization of inoculants containing Azospirillum is becoming more popular due to increasing reports of expressive gains in grain yields. However, incompatibility with pesticides used in seed treatments represents a main limitation for a successful inoculation. Therefore, in this study we searched for alternatives methods for seed inoculation of maize and wheat, aiming to avoid the direct contact of bacteria with pesticides. Different doses of inoculants containing Azospirillum brasilense were employed to perform inoculation in-furrow, via soil spray at sowing and via leaf spray after seedlings had emerged, in comparison to seed inoculation. Experiments were conducted first under greenhouse controlled conditions and then confirmed in the field at different locations in Brazil. In the greenhouse, most parameters measured responded positively to the largest inoculant dose used in foliar sprays, but benefits could also be observed from both in-furrow and soil spray inoculation. However, our results present evidence that field inoculation with plant-growth promoting bacteria must consider inoculant doses, and point to the need of fine adjustments to avoid crossing the threshold of growth stimulation and inhibition. All inoculation techniques increased the abundance of diazotrophic bacteria in plant tissues, and foliar spray improved colonization of leaves, while soil inoculations favored root and rhizosphere colonization. In field experiments, inoculation with A. brasilense allowed for a 25 % reduction in the need for N fertilizers. Our results have identified alternative methods of inoculation that were as effective as the standard seed inoculation that may represent an important strategy to avoid the incompatibility between inoculant bacteria and pesticides employed for seed treatment.

Influence of plant root exudates, germ tube orientation and passive conidia transport on biological control of fusarium wilt by strains of nonpathogenic Fusarium oxysporum.

PubMed

Mandeel, Qaher A

2006-03-01

In earlier studies, biological control of Fusarium wilt of cucumber induced by Fusarium oxysporum f. sp. cucumerinum was demonstrated using nonpathogenic strains C5 and C14 of Fusarium oxysporum. Strain C14 induced resistance and competed for infection sites whether roots were wounded or intact, whereas strain C5 required wounds to achieve biocontrol. In the current work, additional attributes involved in enhanced resistance by nonpathogenic biocontrol agents strains to Fusarium wilt of cucumber and pea were further investigated. In pre-penetration assays, pathogenic formae specials exhibited a significantly higher percentage of spore germination in 4-day-old root exudates of cucumber and pea than nonpathogens. Also, strain C5 exhibited the lowest significant reduction in spore germination in contrast to strain C14 or control. One-day-old cucumber roots injected with strain C14 resulted in significant reduction in germ tube orientation towards the root surface, 48-96 h after inoculation with F. o. cucumerinum spores, whereas strain C5 induced significantly lower spore orientation of the pathogen and only at 72 and 96 h after inoculation. In post-penetration tests, passive transport of microconidia of pathogenic and nonpathogens in stems from base to apex were examined when severed plant roots were immersed in spore suspension. In repeated trials, strain C5, F. o. cucumerinum and F. o. pisi were consistently isolated from stem tissues of both cucumber and pea at increasing heights over a 17 days incubation period. Strain C14 however, was recovered at a maximum translocation distance of 4.6 cm at day 6 and later height of isolation significantly declined thereafter to 1.2 cm at day 17. In pea stem, the decline was even less. Significant induction of resistance to challenge inoculation by the pathogen in cucumber occurred 72 and 96 h after pre-inoculation with biocontrol agents. Nonetheless, strain C14 induced protection as early as 48 h and the maximum resistance was reached at 96 h. The presented data confirm the previous findings that attributes important for nonpathogenic fusaria to induce resistant are: rapid spore germination and orientation in response to root exudate; active root penetration and passive conidia transport in stem to initiate defence reaction without pathogenicity and enough lag period between induction and challenge inoculation. Strain C14 possesses all these qualifications and hence its ability to enhance host resistance is superior than strain C5.

Allocation of Nitrogen and Carbon Is Regulated by Nodulation and Mycorrhizal Networks in Soybean/Maize Intercropping System

PubMed Central

Wang, Guihua; Sheng, Lichao; Zhao, Dan; Sheng, Jiandong; Wang, Xiurong; Liao, Hong

2016-01-01

Soybean/maize intercropping has remarkable advantages in increasing crop yield and nitrogen (N) efficiency. However, little is known about the contributions of rhizobia or arbuscular mycorrhizal fungi (AMF) to yield increases and N acquisition in the intercropping system. Plus, the mechanisms controlling carbon (C) and N allocation in intercropping systems remain unsettled. In the present study, a greenhouse experiment combined with 15N and 13C labeling was conducted using various inoculation and nutrient treatments. The results showed that co-inoculation with AMF and rhizobia dramatically increased biomass and N content of soybean and maize, and moderate application of N and phosphorus largely amplified the effect of co-inoculation. Maize had a competitive advantage over soybean only under co-inoculation and moderate nutrient availability conditions, indicating that the effects of AMF and rhizobia in intercropping systems are closely related to nutrient status. Results from 15N labeling showed that the amount of N transferred from soybean to maize in co-inoculations was 54% higher than that with AMF inoculation alone, with this increased N transfer partly resulting from symbiotic N fixation. The results from 13C labeling showed that 13C content increased in maize shoots and decreased in soybean roots with AMF inoculation compared to uninoculated controls. Yet, with co-inoculation, 13C content increased in soybean. These results indicate that photosynthate assimilation is stimulated by AM symbiosis in maize and rhizobial symbiosis in soybean, but AMF inoculation leads to soybean investing more carbon than maize into common mycorrhizal networks (CMNs). Overall, the results herein demonstrate that the growth advantage of maize when intercropped with soybean is due to acquisition of N by maize via CMNs while this crop contributes less C into CMNs than soybean under co-inoculation conditions. PMID:28018420

Allocation of Nitrogen and Carbon Is Regulated by Nodulation and Mycorrhizal Networks in Soybean/Maize Intercropping System.

PubMed

Wang, Guihua; Sheng, Lichao; Zhao, Dan; Sheng, Jiandong; Wang, Xiurong; Liao, Hong

2016-01-01

Soybean/maize intercropping has remarkable advantages in increasing crop yield and nitrogen (N) efficiency. However, little is known about the contributions of rhizobia or arbuscular mycorrhizal fungi (AMF) to yield increases and N acquisition in the intercropping system. Plus, the mechanisms controlling carbon (C) and N allocation in intercropping systems remain unsettled. In the present study, a greenhouse experiment combined with 15 N and 13 C labeling was conducted using various inoculation and nutrient treatments. The results showed that co-inoculation with AMF and rhizobia dramatically increased biomass and N content of soybean and maize, and moderate application of N and phosphorus largely amplified the effect of co-inoculation. Maize had a competitive advantage over soybean only under co-inoculation and moderate nutrient availability conditions, indicating that the effects of AMF and rhizobia in intercropping systems are closely related to nutrient status. Results from 15 N labeling showed that the amount of N transferred from soybean to maize in co-inoculations was 54% higher than that with AMF inoculation alone, with this increased N transfer partly resulting from symbiotic N fixation. The results from 13 C labeling showed that 13 C content increased in maize shoots and decreased in soybean roots with AMF inoculation compared to uninoculated controls. Yet, with co-inoculation, 13 C content increased in soybean. These results indicate that photosynthate assimilation is stimulated by AM symbiosis in maize and rhizobial symbiosis in soybean, but AMF inoculation leads to soybean investing more carbon than maize into common mycorrhizal networks (CMNs). Overall, the results herein demonstrate that the growth advantage of maize when intercropped with soybean is due to acquisition of N by maize via CMNs while this crop contributes less C into CMNs than soybean under co-inoculation conditions.

Improvement of cadmium phytoremediation after soil inoculation with a cadmium-resistant Micrococcus sp.

PubMed

Sangthong, Chirawee; Setkit, Kunchaya; Prapagdee, Benjaphorn

2016-01-01

Cadmium-resistant Micrococcus sp. TISTR2221, a plant growth-promoting bacterium, has stimulatory effects on the root lengths of Zea mays L. seedlings under toxic cadmium conditions compared to uninoculated seedlings. The performance of Micrococcus sp. TISTR2221 on promoting growth and cadmium accumulation in Z. mays L. was investigated in a pot experiment. The results indicated that Micrococcus sp. TISTR2221significantly promoted the root length, shoot length, and dry biomass of Z. mays L. transplanted in both uncontaminated and cadmium-contaminated soils. Micrococcus sp. TISTR2221 significantly increased cadmium accumulation in the roots and shoots of Z. mays L. compared to uninoculated plants. At the beginning of the planting period, cadmium accumulated mainly in the shoots. With a prolonged duration of cultivation, cadmium content increased in the roots. As expected, little cadmium was found in maize grains. Soil cadmium was significantly reduced with time, and the highest percentage of cadmium removal was found in the bacterial-inoculated Z. mays L. after transplantation for 6 weeks. We conclude that Micrococcus sp. TISTR2221 is a potent bioaugmenting agent, facilitating cadmium phytoextraction in Z. mays L.

Effects of Pratylenchus penetrans on the Infection of Strawberry Roots by Gnomonia comari

PubMed Central

Kurppa, S.; Vrain, T. C.

1989-01-01

The fungus Gnomonia comari, causal agent of strawberry leaf blotch, was inoculated at the crown of young axenized strawberry plants growing in sterilized sand. Only the roots were colonized, and the infection was symptomless. When the fungus colonized the roots in the presence of the root lesion nematode Pratylenchus penetrans, the plants were extremely stunted and their root system was necrotic. Fungal conidiospores were found attached to the cuticle of nematodes extracted from soil inoculated with the two pathogens. These findings indicate that P. penetrans could transport conidiospores through soil. PMID:19287646

Compatible bacterial mixture, tolerant to desiccation, improves maize plant growth.

PubMed

Molina-Romero, Dalia; Baez, Antonino; Quintero-Hernández, Verónica; Castañeda-Lucio, Miguel; Fuentes-Ramírez, Luis Ernesto; Bustillos-Cristales, María Del Rocío; Rodríguez-Andrade, Osvaldo; Morales-García, Yolanda Elizabeth; Munive, Antonio; Muñoz-Rojas, Jesús

2017-01-01

Plant growth-promoting rhizobacteria (PGPR) increase plant growth and crop productivity. The inoculation of plants with a bacterial mixture (consortium) apparently provides greater benefits to plant growth than inoculation with a single bacterial strain. In the present work, a bacterial consortium was formulated containing four compatible and desiccation-tolerant strains with potential as PGPR. The formulation had one moderately (Pseudomonas putida KT2440) and three highly desiccation-tolerant (Sphingomonas sp. OF178, Azospirillum brasilense Sp7 and Acinetobacter sp. EMM02) strains. The four bacterial strains were able to adhere to seeds and colonize the rhizosphere of plants when applied in both mono-inoculation and multi-inoculation treatments, showing that they can also coexist without antagonistic effects in association with plants. The effects of the bacterial consortium on the growth of blue maize were evaluated. Seeds inoculated with either individual bacterial strains or the bacterial consortium were subjected to two experimental conditions before sowing: normal hydration or desiccation. In general, inoculation with the bacterial consortium increased the shoot and root dry weight, plant height and plant diameter compared to the non-inoculated control or mono-inoculation treatments. The bacterial consortium formulated in this work had greater benefits for blue maize plants even when the inoculated seeds underwent desiccation stress before germination, making this formulation attractive for future field applications.

Compatible bacterial mixture, tolerant to desiccation, improves maize plant growth

PubMed Central

Molina-Romero, Dalia; Baez, Antonino; Quintero-Hernández, Verónica; Castañeda-Lucio, Miguel; Fuentes-Ramírez, Luis Ernesto; Bustillos-Cristales, María del Rocío; Rodríguez-Andrade, Osvaldo; Morales-García, Yolanda Elizabeth; Munive, Antonio

2017-01-01

Plant growth-promoting rhizobacteria (PGPR) increase plant growth and crop productivity. The inoculation of plants with a bacterial mixture (consortium) apparently provides greater benefits to plant growth than inoculation with a single bacterial strain. In the present work, a bacterial consortium was formulated containing four compatible and desiccation-tolerant strains with potential as PGPR. The formulation had one moderately (Pseudomonas putida KT2440) and three highly desiccation-tolerant (Sphingomonas sp. OF178, Azospirillum brasilense Sp7 and Acinetobacter sp. EMM02) strains. The four bacterial strains were able to adhere to seeds and colonize the rhizosphere of plants when applied in both mono-inoculation and multi-inoculation treatments, showing that they can also coexist without antagonistic effects in association with plants. The effects of the bacterial consortium on the growth of blue maize were evaluated. Seeds inoculated with either individual bacterial strains or the bacterial consortium were subjected to two experimental conditions before sowing: normal hydration or desiccation. In general, inoculation with the bacterial consortium increased the shoot and root dry weight, plant height and plant diameter compared to the non-inoculated control or mono-inoculation treatments. The bacterial consortium formulated in this work had greater benefits for blue maize plants even when the inoculated seeds underwent desiccation stress before germination, making this formulation attractive for future field applications. PMID:29117218

A rapid inoculation technique for assessing pathogenicity of Fusarium oxysporum f. sp. niveum and F. o. melonis on Cucurbits

USGS Publications Warehouse

Freeman, S.; Rodriguez, R.J.

1993-01-01

A continuous-dip inoculation technique for rapid assessment of pathogenicity of Fusarium oxysporum f. sp. niveum and F. o. melonis was developed. The method, adapted from a similar procedure for determining pathogenicity of Colletotrichum magna (causal agent of anthracnose of cucurbits), involves constant exposure of seedlings and cuttings (seedlings with root systems excised) of watermelon and muskmelon to conidial suspensions contained in small scintillation vials. Disease development in intact seedlings corresponded well to disease responses observed with the standard root-dip inoculation/pot assay. The continuous-dip inoculation technique resulted in rapid disease development, with 50% of watermelon cuttings dying after 4–6 days of exposure to F. o. niveum. A mortality of 30% also was observed in watermelon cuttings exposed to conidia of F. o. melonis, as opposed to only a 0–2.5% mortality in seedlings with intact roots. Disease response was similar with muskmelon seedlings and cuttings continuously dip-inoculated with F. o. melonis isolates. However, no disease symptoms were observed in muskmelon seedlings or cuttings inoculated with F. o. niveum. Four nonpathogenic isolates of F. oxysporum did not cause disease symptoms in either watermelon or muskmelon cuttings and seedlings when assayed by this technique. The proposed method enables a rapid screening of pathogenicity and requires less time, labor, and greenhouse space than the standard root-dip inoculation/pot assay. The reliability of the continuous-dip inoculation technique is limited, however, to exposure of intact seedlings at a concentration of 1 × 106conidia per milliliter; the method is not accurate at this range for excised seedlings.

ANTIMICROBIAL ACTIVITY OF SODIUM HYPOCHLORITE ASSOCIATED WITH INTRACANAL MEDICATION FOR Candida albicans AND Enterococcus faecalis INOCULATED IN ROOT CANALS

PubMed Central

Valera, Marcia Carneiro; da Silva, Katy Costa Godinho; Maekawa, Lilian Eiko; Carvalho, Cláudio Antonio Talge; Koga-Ito, Cristiane Yumi; Camargo, Carlos Henrique Ribeiro; Silva e Lima, Raphael

2009-01-01

Objective: The purpose of this study was to evaluate the action of sodium hypochlorite (NaOCl) associated with an intracanal medication against Candida albicans and Enterococcus faecalis inoculated in root canals. Material and Methods: Thirty-six human single-rooted teeth with single root canals were used. The canals were contaminated with C. albicans and E. faecalis for 21 days and were then instrumented with 1% NaOCl. The roots were divided into 3 groups (n=12) according to the intracanal medication applied: calcium hydroxide paste, 2% chlorhexidine (CHX) gel, and 2% CHX gel associated with calcium hydroxide. The following collections were made from the root canals: a) initial sample (IS): 21 days after contamination (control), b) S1: after instrumentation, c) S2: 14 days after intracanal medication placement; S3: 7 days after intracanal medication removal. The results were analyzed statistically by the Kruskal-Wallis test at 5% significance level. Results and Conclusions: Both 1% NaOCl irrigation and the intracanal medications were effective in eliminating E. faecalis and C. albicans inoculated in root canals. PMID:20027425

Antimicrobial activity of sodium hypochlorite associated with intracanal medication for Candida albicans and Enterococcus faecalis inoculated in root canals.

PubMed

Valera, Marcia Carneiro; Silva, Katy Costa Godinho da; Maekawa, Lilian Eiko; Carvalho, Cláudio Antonio Talge; Koga-Ito, Cristiane Yumi; Camargo, Carlos Henrique Ribeiro; Lima, Raphael Silva e

2009-01-01

The purpose of this study was to evaluate the action of sodium hypochlorite (NaOCl) associated with an intracanal medication against Candida albicans and Enterococcus faecalis inoculated in root canals. Thirty-six human single-rooted teeth with single root canals were used. The canals were contaminated with C. albicans and E. faecalis for 21 days and were then instrumented with 1% NaOCl. The roots were divided into 3 groups (n=12) according to the intracanal medication applied: calcium hydroxide paste, 2% chlorhexidine (CHX) gel, and 2% CHX gel associated with calcium hydroxide. The following collections were made from the root canals: a) initial sample (IS): 21 days after contamination (control), b) S1: after instrumentation, c) S2: 14 days after intracanal medication placement; S3: 7 days after intracanal medication removal. The results were analyzed statistically by the Kruskal-Wallis test at 5% significance level. Both 1% NaOCl irrigation and the intracanal medications were effective in eliminating E. faecalis and C. albicans inoculated in root canals.

Arbuscular mycorrhizal fungal inoculation protects Miscanthus × giganteus against trace element toxicity in a highly metal-contaminated site.

PubMed

Firmin, Stéphane; Labidi, Sonia; Fontaine, Joël; Laruelle, Frédéric; Tisserant, Benoit; Nsanganwimana, Florian; Pourrut, Bertrand; Dalpé, Yolande; Grandmougin, Anne; Douay, Francis; Shirali, Pirouz; Verdin, Anthony; Lounès-Hadj Sahraoui, Anissa

2015-09-15

Arbuscular mycorrhizal fungus (AMF)-assisted phytoremediation could constitute an ecological and economic method in polluted soil rehabilitation programs. The aim of this work was to characterize the trace element (TE) phytoremediation potential of mycorrhizal Miscanthus × giganteus. To understand the mechanisms involved in arbuscular mycorrhizal symbiosis tolerance to TE toxicity, the fatty acid compositions and several stress oxidative biomarkers were compared in the roots and leaves of Miscanthus × giganteus cultivated under field conditions in either TE-contaminated or control soils. TEs were accumulated in greater amounts in roots, but the leaves were the organ most affected by TE contamination and were characterized by a strong decrease in fatty acid contents. TE-induced oxidative stress in leaves was confirmed by an increase in the lipid peroxidation biomarker malondialdehyde (MDA). TE contamination decreased the GSSG/GSH ratio in the leaves of exposed plants, while peroxidase (PO) and superoxide dismutase (SOD) activities were increased in leaves and in whole plants, respectively. AMF inoculation also increased root colonization in the presence of TE contamination. The mycorrhizal colonization determined a decrease in SOD activity in the whole plant and PO activities in leaves and induced a significant increase in the fatty acid content in leaves and a decrease in MDA formation in whole plants. These results suggested that mycorrhization is able to confer protection against oxidative stress induced by soil pollution. Our findings suggest that mycorrhizal inoculation could be used as a bioaugmentation technique, facilitating Miscanthus cultivation on highly TE-contaminated soil. Copyright © 2015. Published by Elsevier B.V.

Arbuscular mycorrhizal fungi increase salt tolerance of apple seedlings.

PubMed

Yang, Shou-Jun; Zhang, Zhong-Lan; Xue, Yuan-Xia; Zhang, Zhi-Fen; Shi, Shu-Yi

2014-12-01

Apple trees are often subject to severe salt stress in China as well as in the world that results in significant loss of apple production. Therefore this study was carried out to evaluate the response of apple seedlings inoculated with abuscular mycorrhizal fungi under 0, 2‰, 4‰ and 6‰ salinity stress levels and further to conclude the upper threshold of mycorrhizal salinity tolerance. The results shows that abuscular mycorrhizal fungi significantly increased the root length colonization of mycorrhizal apple plants with exposure time period to 0, 2‰ and 4‰ salinity levels as compared to non-mycorrhizal plants, however, percent root colonization reduced as saline stress increased. Salinity levels were found to negatively correlate with leaf relative turgidity, osmotic potential irrespective of non-mycorrhizal and mycorrhizal apple plants, but the decreased mycorrhizal leaf turgidity maintained relative normal values at 2‰ and 4‰ salt concentrations. Under salt stress condition, Cl - and Na + concentrations clearly increased and K + contents obviously decreased in non-mycorrhizal roots in comparison to mycorrhizal plants, this caused mycorrhizal plants had a relatively higher K + /Na + ratio in root. In contrast to zero salinity level, although ascorbate peroxidase and catalase activities in non-inoculated and inoculated leaf improved under all saline levels, the extent of which these enzymes increased was greater in mycorrhizal than in non-mycorrhizal plants. The numbers of survived tree with non-mycorrhization were 40, 20 and 0 (i.e., 66.7%, 33.3% and 0) on the days of 30, 60 and 90 under 4‰ salinity, similarly in mycorrhization under 6‰ salinity 40, 30 and 0 (i.e., 66.7%, 50% and 0) respectively. These results suggest that 2‰ and 4‰ salt concentrations may be the upper thresholds of salinity tolerance in non-mycorrhizal and mycorrhizal apple plants, respectively.

Effect of the fungus Piriformospora indica on physiological characteristics and root morphology of wheat under combined drought and mechanical stresses.

PubMed

Hosseini, Fatemeh; Mosaddeghi, Mohammad Reza; Dexter, Anthony Roger

2017-09-01

This study was done to evaluate the effects of the root-colonizing endophytic fungus Piriformospora indica on wheat growth under combined drought and mechanical stresses. Inoculated (colonized) and non-inoculated (uncolonized) wheat (Triticum aestivum L. cv. Chamran) seedlings were planted in growth chambers filled with moist sand (at a matric suction of 20 hPa). Slight, moderate and severe mechanical stresses (i.e., penetration resistance, Q p , of 1.17, 4.17 and 5.96 MPa, respectively) were produced by a dead-load technique (i.e., placing a weight on the sand surface) in the root medium. Slight, moderate and severe drought stresses were induced using PEG 6000 solutions with osmotic potentials of 0, -0.3 and -0.5 MPa, respectively. After 30 days, plant physiological characteristics and root morphology were measured. An increase in Q p from 1.17 to 5.96 MPa led to greater leaf proline concentration and root diameter, and lower relative water content (RWC), leaf water potential (LWP), chlorophyll contents and root volume. Moreover, severe drought stress decreased root and shoot fresh weights, root volume, leaf area, RWC, LWP and chlorophyll content compared to control. Catalase (CAT) and ascorbate peroxidase (APX) activities under severe drought stress were about 1.5 and 2.9 times greater than control. Interaction of the stresses showed that mechanical stress primarily controls plant water status and physiological responses. However, endophyte presence mitigated the adverse effects of individual and combined stresses on plant growth. Colonized plants were better adapted and had greater root length and volume, RWC, LWP and chlorophyll contents under stressful conditions due to higher absorption sites for water and nutrients. Compared with uncolonized plants, colonized plants showed lower CAT activity implying that wheat inoculated with P. indica was more tolerant and experienced less oxidative damage induced by drought and/or mechanical stress. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Elevated Atmospheric CO2 and Strain of Rhizobium Alter Freezing Tolerance and Cold-induced Molecular Changes in Alfalfa (Medicago sativa)

PubMed Central

Bertrand, Annick; Prévost, Danielle; Bigras, Francine J.; Castonguay, Yves

2007-01-01

Background and Aims The objective of the study was to assess the impact of elevated CO2 in interaction with rhizobial strains on freezing tolerance and cold-induced molecular changes in alfalfa. Methods Alfalfa inoculated with two different strains of rhizobium (A2 and NRG34) was grown and cold acclimated (2 weeks at 2 °C) under either 400 (ambient) or 800 µmol mol−1 (elevated) CO2. Key Results Plants acclimated under 400 µmol mol−1 CO2 were more freezing tolerant than those maintained under 800 µmol mol−1. Cryoprotective sugars typically linked with the acquisition of freezing tolerance such as sucrose, stachyose and raffinose increased in roots in response to low temperature but did not differ between CO2 treatments. Similarly high CO2 did not alter the expression of many cold-regulated (COR) genes although it significantly increased the level of transcripts encoding a COR gene homologous to glyceraldehyde-3-phosphate-dehydrogenase (GAPDH). A significant effect of rhizobial strain was observed on both freezing tolerance and gene expression. Plants of alfalfa inoculated with strain A2 were more freezing tolerant than those inoculated with strain NRG34. Transcripts of COR genes homologous to a pathogenesis-related protein (PR-10) and to a nuclear-targeted protein were markedly enhanced in roots of alfalfa inoculated with strain A2 as compared with strain NRG34. Transcripts encoding the vegetative storage proteins (VSPs) β-amylase and chitinase were more abundant in roots of non-acclimated plants inoculated with strain NRG34 than with strain A2. Conclusions Taken together, the results suggest that elevated CO2 stimulates plant growth and reduces freezing tolerance. The acquisition of cold tolerance is also influenced by the rhizobial strain, as indicated by lower levels of expression of COR genes and sustained accumulation of VSP-encoding transcripts in alfalfa inoculated with strain NRG34 as compared with strain A2. PMID:17218341

Nitrogen fertilizer enhances growth and nutrient uptake of Medicago sativa inoculated with Glomus tortuosum grown in Cd-contaminated acidic soil.

PubMed

Liu, Mohan; Sun, Jian; Li, Yang; Xiao, Yan

2017-01-01

This study aimed to explore whether nitrogen availability could influence mycorrhizal function and their associations with host plants in Cd-contaminated acidic soils or not. A greenhouse pot experiment was conducted to assess the effects of mycorrhizal inoculation (non-mycorrhizal inoculation (NM), Glomus aggregatum (Ga), G. tortuosum (Gt) and G. versiforme (Gv)) and inorganic N amendment on the growth, nutrient and Cd uptake of Medicago sativa grown in Cd-contaminated acidic soils (10 mg Cd kg -1 soil). AMF inoculations significantly increased the shoot and total biomass and decreased the shoot Cd concentration in comparison to plants uninoculated. N addition increased markedly concentration and content of N and decreased those of P in plants at all inoculation treatments. Shoot K, Na and Mg concentration in plants inoculated with Ga and Gv were decreased by N addition, whereas shoot K, Na, Ca and Mg concentration in plants inoculated with Gt were not negatively affected. It was observed that N addition only increased mycorrhizal colonization, shoot biomass, shoot K, Ca and Mg content of plants inoculated with Gt. Irrespective of N addition, plants with Gt inoculation got the maximum shoot and root P concentration and content, as well as P/Cd concentration molar ratio among all inoculation treatment. Neither AMF nor N fertilizer contributed to the decrease of soil exchangeable Cd and increase of soil pH. These results suggested that N fertilizer only elevated plant performance of alfalfa with Gt inoculation grown in acidic soil, by diluting Cd concentration and alleviating of nutrient deficiency, especially P. Copyright © 2016 Elsevier Ltd. All rights reserved.

Medicago truncatula Gaertn. as a model for understanding the mechanism of growth promotion by bacteria from rhizosphere and nodules of alfalfa.

PubMed

Kisiel, Anna; Kępczyńska, Ewa

2016-05-01

The present study showed all the 16 strains isolated and identified from the alfalfa rhizosphere and nodules, and registered in GenBank, to be good candidates for targeted use in studies addressing the rather weak known mechanism of plant growth promotion, including that of Medicago truncatula, a molecular crop model. Based on physiological, biochemical and molecular analysis, the 16 isolates obtained were ascribed to the following five families: Bacillaceae, Rhizobiaceae, Xantomonadaceae, Enterobacteriaceae and Pseudomonadaceae, within which 9 genera and 16 species were identified. All these bacteria were found to significantly enhance fresh and dry weight of root, shoots and whole 5-week-old seedlings. The bacteria were capable of the in vitro use of tryptophan to produce indolic compounds at various concentrations. The ability of almost all the strains to enhance growth of seedlings and individual roots was positively correlated with the production of the indolic compounds (r = 0.69; P = 0.0001), but not with the 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity (no correlation). For some strains, it was difficult to conclude whether the growth promotion was related to the production of indolic compounds or to the ACCD activity. It is likely that promotion of M. truncatula root development involves also root interaction with pseudomonads, known to produce 2,4-diacetylphloroglucinol (DAPG), a secondary metabolite reported to alter the root architecture by interacting with an auxin-dependent signaling pathway. Inoculation of seedlings with Pseudomonas brassicacearum KK 5, a bacterium known for its lowest ability to produce indolic compounds, the highest ACCD activity and the presence of the phlD gene responsible for DAPG precursor synthesis, resulted in a substantial promotion of root development. Inoculation with the strain increased the endogenous IAA level in M. truncatula leaves after inoculation of 5-week-old seedlings. Three other strains examined in this study also increased the IAA level in the leaves upon inoculation. Moreover, several other factors such as mobilization of phosphorus and zinc to make them available to plants, iron sequestration by siderophore production and the ability to ammonia production also contributed substantially to the phytostimulatory biofertilizing potential of isolated strains. There is, thus, evidence that Medicago truncatula growth promotion by rhizobacteria involves more than one mechanism.

Host Suitability of Eight Prunus spp. and One Pyrus communis Rootstocks to Pratylenchus vulnus, P. neglectus, and P. thornei

PubMed Central

Pinochet, J.; Verdejo-Lucas, S.; Marull, J.

1991-01-01

The effects of Pratylenchus vulnus on rootstocks of eight commonly used Prunus spp. and one Pyrus communis were evaluated under greenhouse conditions during a 15-month period. In a first experiment, two almonds (Moncayo and Garrigues), one peach (GF-305), and two peach-almond hybrids (GF-677 and Adafuel) inoculated with 2,000 nematodes per plant proved to be good hosts of P. vulnus. Highest (P < 0.05) numbers of nematodes per gram of fresh root weight were recovered from Adafuel and GF-677. Root weights were higher in uninoculated compared to inoculated plants of all rootstocks, whereas top weights of uninoculated Garrigues, GF-305, and GF-677 differed (P < 0.05) from those of inoculated plants. In a second experiment, three plum (Marianna 2624, Myrobalan 605, and San Julian 655-2) and one pear (OHF-333) rootstocks were also found to be good hosts of P. vulnus, although significantly fewer nematodes were recovered from Myrohalan 605 roots than from the other three materials. Inoculated OHF-333 and San Julian 655-2 differed (P < 0.05) in root weights over uninoculated plants. Only inoculated San Julian 655-2 showed differences in top weights over uninoculated treatments. Rootstocks were poor or non-hosts for P. neglectus and P. thornei. PMID:19283165

[Response of alfalfa seed to stress storage conditions].

PubMed

Li, Chunjie; Wang, Yanrong; Zhu, Tingheng; Yu, Ling

2002-08-01

The seed germination rate, seed mortality, seedling length, and infection rate of alfalfa (Medicago sativa L. cv. 'Longdong') were measured at constant temperature 20 degrees C every 60 days during one year storage period after inoculated or no inoculated by Fusarium avenaceum under room temperature (RT), 35 degrees C, and 35 degrees C and +10% seed moisture content (SMC) conditions. Field emergence rates of seeds under above treatments were also observed, and seed-borne fungi were detected under the conditions mentioned above and controlled deterioration (CD) as well. The results showed that the percentage of isolated alfalfa seed-borne fungi was increased from 10% under room temperature and 35 degrees C to 29% under 35 degrees C + 10% SMC. Disease resistance was declined, and seed mortality and seedling infection rate under 35 degrees C + 10% SMC were significantly higher than those under room temperature and 35 degrees C respectively (P < 0.05). The seed germination rate and field emergence rate were also decreased significantly (P < 0.05). Seedling shoot and root length under 35 degrees C + 10% SMC were significantly less than those under RT and 35 degrees C respectively (P < 0.05). The percentages of both seed-borne fungi isolated and field emergence were decreased, and that of seedling infection was increased with storage period extending from 60 to 360 days. Compared to no inoculated control, the percentage of seed germination, seedling shoot and root length were decreased, and seed mortality and seedling infection rate were increased after inoculated by F. avenaceum.

Nodulation by Sinorhizobium meliloti originated from a mining soil alleviates Cd toxicity and increases Cd-phytoextraction in Medicago sativa L.

PubMed

Ghnaya, Tahar; Mnassri, Majda; Ghabriche, Rim; Wali, Mariem; Poschenrieder, Charlotte; Lutts, Stanley; Abdelly, Chedly

2015-01-01

Besides their role in nitrogen supply to the host plants as a result of symbiotic N fixation, the association between legumes and Rhizobium could be useful for the rehabilitation of metal-contaminated soils by phytoextraction. A major limitation presents the metal-sensitivity of the bacterial strains. The aim of this work was to explore the usefulness of Sinorhizobium meliloti originated from a mining site for Cd phytoextraction by Medicago sativa. Inoculated and non-inoculated plants were cultivated for 60 d on soils containing 50 and/or 100 mg Cd kg(-1) soil. The inoculation hindered the occurrence of Cd- induced toxicity symptoms that appeared in the shoots of non-inoculated plants. This positive effect of S. meliloti colonization was accompanied by an increase in biomass production and improved nutrient acquisition comparatively to non-inoculated plants. Nodulation enhanced Cd absorption by the roots and Cd translocation to the shoots. The increase of plant biomass concomitantly with the increase of Cd shoot concentration in inoculated plants led to higher potential of Cd-phytoextraction in these plants. In the presence of 50 mg Cd kg(-1) in the soil, the amounts of Cd extracted in the shoots were 58 and 178 μg plant(-1) in non-inoculated and inoculated plants, respectively. This study demonstrates that this association M. sativa-S. meliloti may be an efficient biological system to extract Cd from contaminated soils.

Nodulation by Sinorhizobium meliloti originated from a mining soil alleviates Cd toxicity and increases Cd-phytoextraction in Medicago sativa L.

PubMed Central

Ghnaya, Tahar; Mnassri, Majda; Ghabriche, Rim; Wali, Mariem; Poschenrieder, Charlotte; Lutts, Stanley; Abdelly, Chedly

2015-01-01

Besides their role in nitrogen supply to the host plants as a result of symbiotic N fixation, the association between legumes and Rhizobium could be useful for the rehabilitation of metal-contaminated soils by phytoextraction. A major limitation presents the metal-sensitivity of the bacterial strains. The aim of this work was to explore the usefulness of Sinorhizobium meliloti originated from a mining site for Cd phytoextraction by Medicago sativa. Inoculated and non-inoculated plants were cultivated for 60 d on soils containing 50 and/or 100 mg Cd kg−1 soil. The inoculation hindered the occurrence of Cd- induced toxicity symptoms that appeared in the shoots of non-inoculated plants. This positive effect of S. meliloti colonization was accompanied by an increase in biomass production and improved nutrient acquisition comparatively to non-inoculated plants. Nodulation enhanced Cd absorption by the roots and Cd translocation to the shoots. The increase of plant biomass concomitantly with the increase of Cd shoot concentration in inoculated plants led to higher potential of Cd-phytoextraction in these plants. In the presence of 50 mg Cd kg−1 in the soil, the amounts of Cd extracted in the shoots were 58 and 178 μg plant−1 in non-inoculated and inoculated plants, respectively. This study demonstrates that this association M. sativa-S. meliloti may be an efficient biological system to extract Cd from contaminated soils. PMID:26528320

Contribution of Zinc Solubilizing Bacteria in Growth Promotion and Zinc Content of Wheat.

PubMed

Kamran, Sana; Shahid, Izzah; Baig, Deeba N; Rizwan, Muhammad; Malik, Kauser A; Mehnaz, Samina

2017-01-01

Zinc is an imperative micronutrient required for optimum plant growth. Zinc solubilizing bacteria are potential alternatives for zinc supplementation and convert applied inorganic zinc to available forms. This study was conducted to screen zinc solubilizing rhizobacteria isolated from wheat and sugarcane, and to analyze their effect on wheat growth and development. Fourteen exo-polysaccharides producing bacterial isolates of wheat were identified and characterized biochemically as well as on the basis of 16S rRNA gene sequences. Along these, 10 identified sugarcane isolates were also screened for zinc solubilizing ability on five different insoluble zinc sources. Out of 24, five strains, i.e., EPS 1 ( Pseudomonas fragi) , EPS 6 ( Pantoea dispersa) , EPS 13 ( Pantoea agglomerans) , PBS 2 ( E. cloacae) and LHRW1 ( Rhizobium sp.) were selected (based on their zinc solubilizing and PGP activities) for pot scale plant experiments. ZnCO 3 was used as zinc source and wheat seedlings were inoculated with these five strains, individually, to assess their effect on plant growth and development. The effect on plants was analyzed based on growth parameters and quantifying zinc content of shoot, root and grains using atomic absorption spectroscopy. Plant experiment was performed in two sets. For first set of plant experiments (harvested after 1 month), maximum shoot and root dry weights and shoot lengths were noted for the plants inoculated with Rhizobium sp. (LHRW1) while E. cloacae (PBS 2) increased both shoot and root lengths. Highest zinc content was found in shoots of E. cloacae (PBS 2) and in roots of P. agglomerans (EPS 13) followed by zinc supplemented control. For second set of plant experiment, when plants were harvested after three months, Pantoea dispersa (EPS 6), P. agglomerans (EPS 13) and E. cloacae (PBS 2) significantly increased shoot dry weights. However, significant increase in root dry weights and maximum zinc content was recorded for Pseudomonas fragi (EPS 1) inoculated plants, isolated from wheat rhizosphere. While maximum zinc content for roots was quantified in the control plants indicating the plant's inability to transport zinc to grains, supporting accelerated bioavailability of zinc to plant grains with zinc solubilizing rhizobacteria.

Host plant growth promotion and cadmium detoxification in Solanum nigrum, mediated by endophytic fungi.

PubMed

Khan, Abdur Rahim; Ullah, Ihsan; Waqas, Muhammad; Park, Gun-Seok; Khan, Abdul Latif; Hong, Sung-Jun; Ullah, Rehman; Jung, Byung Kwon; Park, Chang Eon; Ur-Rehman, Shafiq; Lee, In-Jung; Shin, Jae-Ho

2017-02-01

Current investigation conducted to evaluate the associated fungal endophyte interactions of a Cd hyper-accumulator Solanum nigrum Korean ecotype under varying concentrations of Cd. Two indole-3-acetic acid (IAA) producing fungal strains, RSF-4L and RSF-6L, isolated from the leaves of S. nigrum, were initially screened for Cd tolerance and accumulation potential. In terms of dry biomass production, the strain RSF-6L showed higher tolerance and accumulation capacity for Cd toxicity in comparison to RSF-4L. Therefore, RSF-6L was applied in vivo to S. nigrum and grown for six weeks under Cd concentrations of 0, 10, and 30mgKg -1 of dry sand. The effect of fungal inoculation assessed by plant physiological responses, endogenous biochemical regulations, and Cd profile in different tissues. Significant increase were observed in plant growth attributes such as shoot length, root length, dry biomass, leaf area, and chlorophyll contents in inoculated RSF-6L plants in comparison to non-inoculated plants with or without Cd contamination. RSF-6L inoculation decreased uptake of Cd in roots and above ground parts, as evidenced by a low bio-concentration factor (BCF) and improved tolerance index (TI). However, Cd concentration in the leaves remained the same for inoculated and non-inoculated plants under Cd spiking. Fungal inoculation protected the host plants, as evidenced by low peroxidase (POD) and polyphenol peroxidase (PPO) activities and high catalase (CAT) activity. Application of appropriate fungal inoculation that can improve tolerance mechanisms of hyper-accumulators and reduce Cd uptake can be recommended for phyto-stabilisation/immobilisation of heavy metals in crop fields. Copyright © 2016 Elsevier Inc. All rights reserved.

Rhizobial Nodulation Factors Stimulate Mycorrhizal Colonization of Nodulating and Nonnodulating Soybeans.

PubMed

Xie, Z. P.; Staehelin, C.; Vierheilig, H.; Wiemken, A.; Jabbouri, S.; Broughton, W. J.; Vogeli-Lange, R.; Boller, T.

1995-08-01

Legumes form tripartite symbiotic associations with noduleinducing rhizobia and vesicular-arbuscular mycorrhizal fungi. Co-inoculation of soybean (Glycine max [L.] Merr.) roots with Bradyrhizobium japonicum 61-A-101 considerably enhanced colonization by the mycorrhizal fungus Glomus mosseae. A similar stimulatory effect on mycorrhizal colonization was also observed in nonnodulating soybean mutants when inoculated with Bradyrhizobium japonicum and in wild-type soybean plants when inoculated with ineffective rhizobial strains, indicating that a functional rhizobial symbiosis is not necessary for enhanced mycorrhiza formation. Inoculation with the mutant Rhizobium sp. NGR[delta]nodABC, unable to produce nodulation (Nod) factors, did not show any effect on mycorrhiza. Highly purified Nod factors also increased the degree of mycorrhizal colonization. Nod factors from Rhizobium sp. NGR234 differed in their potential to promote fungal colonization. The acetylated factor NodNGR-V (MeFuc, Ac), added at concentrations as low as 10-9 M, was active, whereas the sulfated factor, NodNGR-V (MeFuc, S), was inactive. Several soybean flavonoids known to accumulate in response to the acetylated Nod factor showed a similar promoting effect on mycorrhiza. These results suggest that plant flavonoids mediate the Nod factor-induced stimulation of mycorrhizal colonization in soybean roots.

Rhizobial Nodulation Factors Stimulate Mycorrhizal Colonization of Nodulating and Nonnodulating Soybeans.

PubMed Central

Xie, Z. P.; Staehelin, C.; Vierheilig, H.; Wiemken, A.; Jabbouri, S.; Broughton, W. J.; Vogeli-Lange, R.; Boller, T.

1995-01-01

Legumes form tripartite symbiotic associations with noduleinducing rhizobia and vesicular-arbuscular mycorrhizal fungi. Co-inoculation of soybean (Glycine max [L.] Merr.) roots with Bradyrhizobium japonicum 61-A-101 considerably enhanced colonization by the mycorrhizal fungus Glomus mosseae. A similar stimulatory effect on mycorrhizal colonization was also observed in nonnodulating soybean mutants when inoculated with Bradyrhizobium japonicum and in wild-type soybean plants when inoculated with ineffective rhizobial strains, indicating that a functional rhizobial symbiosis is not necessary for enhanced mycorrhiza formation. Inoculation with the mutant Rhizobium sp. NGR[delta]nodABC, unable to produce nodulation (Nod) factors, did not show any effect on mycorrhiza. Highly purified Nod factors also increased the degree of mycorrhizal colonization. Nod factors from Rhizobium sp. NGR234 differed in their potential to promote fungal colonization. The acetylated factor NodNGR-V (MeFuc, Ac), added at concentrations as low as 10-9 M, was active, whereas the sulfated factor, NodNGR-V (MeFuc, S), was inactive. Several soybean flavonoids known to accumulate in response to the acetylated Nod factor showed a similar promoting effect on mycorrhiza. These results suggest that plant flavonoids mediate the Nod factor-induced stimulation of mycorrhizal colonization in soybean roots. PMID:12228558

Native arbuscular mycorrhizal symbiosis alters foliar bacterial community composition.

PubMed

Poosakkannu, Anbu; Nissinen, Riitta; Kytöviita, Minna-Maarit

2017-11-01

The effects of arbuscular mycorrhizal (AM) fungi on plant-associated microbes are poorly known. We tested the hypothesis that colonization by an AM fungus affects microbial species richness and microbial community composition of host plant tissues. We grew the grass, Deschampsia flexuosa in a greenhouse with or without the native AM fungus, Claroideoglomus etunicatum. We divided clonally produced tillers into two parts: one inoculated with AM fungus spores and one without AM fungus inoculation (non-mycorrhizal, NM). We characterized bacterial (16S rRNA gene) and fungal communities (internal transcribed spacer region) in surface-sterilized leaf and root plant compartments. AM fungus inoculation did not affect microbial species richness or diversity indices in leaves or roots, but the AM fungus inoculation significantly affected bacterial community composition in leaves. A total of three OTUs in leaves belonging to the phylum Firmicutes positively responded to the presence of the AM fungus in roots. Another six OTUs belonging to the Proteobacteria (Alpha, Beta, and Gamma) and Bacteroidetes were significantly more abundant in NM plants when compared to AM fungus-inoculated plants. Further, there was a significant correlation between plant dry weight and leaf microbial community compositional shift. Also, there was a significant correlation between leaf bacterial community compositional shift and foliar nitrogen content changes due to AM fungus inoculation. The results suggest that AM fungus colonization in roots has a profound effect on plant physiology that is reflected in leaf bacterial community composition.

Elevated CO2 spurs reciprocal positive effects between a plant virus and an arbuscular mycorrhizal fungus.

PubMed

Rúa, Megan A; Umbanhowar, James; Hu, Shuijin; Burkey, Kent O; Mitchell, Charles E

2013-07-01

Plants form ubiquitous associations with diverse microbes. These interactions range from parasitism to mutualism, depending partly on resource supplies that are being altered by global change. While many studies have considered the separate effects of pathogens and mutualists on their hosts, few studies have investigated interactions among microbial mutualists and pathogens in the context of global change. Using two wild grass species as model hosts, we grew individual plants under ambient or elevated CO(2), and ambient or increased soil phosphorus (P) supply. Additionally, individuals were grown with or without arbuscular mycorrhizal inoculum, and after 2 wk, plants were inoculated or mock-inoculated with a phloem-restricted virus. Under elevated CO(2), mycorrhizal association increased the titer of virus infections, and virus infection reciprocally increased the colonization of roots by mycorrhizal fungi. Additionally, virus infection decreased plant allocation to root biomass, increased leaf P, and modulated effects of CO(2) and P addition on mycorrhizal root colonization. These results indicate that plant mutualists and pathogens can alter each other's success, and predict that these interactions will respond to increased resource availability and elevated CO(2). Together, our findings highlight the importance of interactions among multiple microorganisms for plant performance under global change. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Rhizosphere Bacteria Enhance Selenium Accumulation and Volatilization by Indian Mustard1

PubMed Central

de Souza, Mark P.; Chu, Dara; Zhao, May; Zayed, Adel M.; Ruzin, Steven E.; Schichnes, Denise; Terry, Norman

1999-01-01

Indian mustard (Brassica juncea L.) accumulates high tissue Se concentrations and volatilizes Se in relatively nontoxic forms, such as dimethylselenide. This study showed that the presence of bacteria in the rhizosphere of Indian mustard was necessary to achieve the best rates of plant Se accumulation and volatilization of selenate. Experiments with the antibiotic ampicillin showed that bacteria facilitated 35% of plant Se volatilization and 70% of plant tissue accumulation. These results were confirmed by inoculating axenic plants with rhizosphere bacteria. Compared with axenic controls, plants inoculated with rhizosphere bacteria had 5-fold higher Se concentrations in roots (the site of volatilization) and 4-fold higher rates of Se volatilization. Plants with bacteria contained a heat-labile compound in their root exudate; when this compound was added to the rhizosphere of axenic plants, Se accumulation in plant tissues increased. Plants with bacteria had an increased root surface area compared with axenic plants; the increased area was unlikely to have caused their increased tissue Se accumulation because they did not accumulate more Se when supplied with selenite or selenomethionine. Rhizosphere bacteria also possibly increased plant Se volatilization because they enabled plants to overcome a rate-limiting step in the Se volatilization pathway, i.e. Se accumulation in plant tissues. PMID:9952452

Arbuscular mycorrhizal fungi alter above- and below-ground chemical defense expression differentially among Asclepias species.

PubMed

Vannette, Rachel L; Hunter, Mark D; Rasmann, Sergio

2013-01-01

Below-ground (BG) symbionts of plants can have substantial influence on plant growth and nutrition. Recent work demonstrates that mycorrhizal fungi can affect plant resistance to herbivory and the performance of above- (AG) and BG herbivores. Although these examples emerge from diverse systems, it is unclear if plant species that express similar defensive traits respond similarly to fungal colonization, but comparative work may inform this question. To examine the effects of arbuscular mycorrhizal fungi (AMF) on the expression of chemical resistance, we inoculated 8 species of Asclepias (milkweed)-which all produce toxic cardenolides-with a community of AMF. We quantified plant biomass, foliar and root cardenolide concentration and composition, and assessed evidence for a growth-defense tradeoff in the presence and absence of AMF. As expected, total foliar and root cardenolide concentration varied among milkweed species. Importantly, the effect of mycorrhizal fungi on total foliar cardenolide concentration also varied among milkweed species, with foliar cardenolides increasing or decreasing, depending on the plant species. We detected a phylogenetic signal to this variation; AMF fungi reduced foliar cardenolide concentrations to a greater extent in the clade including A. curassavica than in the clade including A. syriaca. Moreover, AMF inoculation shifted the composition of cardenolides in AG and BG plant tissues in a species-specific fashion. Mycorrhizal inoculation changed the relative distribution of cardenolides between root and shoot tissue in a species-specific fashion, but did not affect cardenolide diversity or polarity. Finally, a tradeoff between plant growth and defense in non-mycorrhizal plants was mitigated completely by AMF inoculation. Overall, we conclude that the effects of AMF inoculation on the expression of chemical resistance can vary among congeneric plant species, and ameliorate tradeoffs between growth and defense.

Arbuscular mycorrhizal fungi alter above- and below-ground chemical defense expression differentially among Asclepias species

PubMed Central

Vannette, Rachel L.; Hunter, Mark D.; Rasmann, Sergio

2013-01-01

Below-ground (BG) symbionts of plants can have substantial influence on plant growth and nutrition. Recent work demonstrates that mycorrhizal fungi can affect plant resistance to herbivory and the performance of above- (AG) and BG herbivores. Although these examples emerge from diverse systems, it is unclear if plant species that express similar defensive traits respond similarly to fungal colonization, but comparative work may inform this question. To examine the effects of arbuscular mycorrhizal fungi (AMF) on the expression of chemical resistance, we inoculated 8 species of Asclepias (milkweed)—which all produce toxic cardenolides—with a community of AMF. We quantified plant biomass, foliar and root cardenolide concentration and composition, and assessed evidence for a growth-defense tradeoff in the presence and absence of AMF. As expected, total foliar and root cardenolide concentration varied among milkweed species. Importantly, the effect of mycorrhizal fungi on total foliar cardenolide concentration also varied among milkweed species, with foliar cardenolides increasing or decreasing, depending on the plant species. We detected a phylogenetic signal to this variation; AMF fungi reduced foliar cardenolide concentrations to a greater extent in the clade including A. curassavica than in the clade including A. syriaca. Moreover, AMF inoculation shifted the composition of cardenolides in AG and BG plant tissues in a species-specific fashion. Mycorrhizal inoculation changed the relative distribution of cardenolides between root and shoot tissue in a species-specific fashion, but did not affect cardenolide diversity or polarity. Finally, a tradeoff between plant growth and defense in non-mycorrhizal plants was mitigated completely by AMF inoculation. Overall, we conclude that the effects of AMF inoculation on the expression of chemical resistance can vary among congeneric plant species, and ameliorate tradeoffs between growth and defense. PMID:24065971

Soil Nitrogen Status Modifies Rice Root Response to Nematode-Bacteria Interactions in the Rhizosphere

PubMed Central

Wu, Yue; Valentine, Tracy A.; Li, Huixin

2016-01-01

It has been hypothesized that faunal activity in the rhizosphere influences root growth via an auxin-dependent pathway. In this study, two methods were used to adjust nematode and bacterial populations within experimental soils. One is “exclusion”, where soil mixed with pig manure was placed in two bags with different mesh sizes (1mm and 5μm diameter), and then surrounded by an outer layer of unamended soil resulting in soil with a greater populations of bacterial-feeding nematodes (1mm) and a control treatment (5μm). The second method is “inoculation”, whereby autoclaved soil was inoculated with bacteria (E. coli and Pseudomonas) and Nematodes (Cephalobus and C. elegans). In order to detect the changes in the rice’s perception of auxin under different nutrient and auxin conditions in the presence of soil bacterial-feeding nematodes, responses of soil chemistry (NH4+, NO3- and indole acetic acid (IAA)), rice root growth and the expression of an auxin responsive gene GH3-2 were measured. Results showed that, under low soil nutrient conditions (exclusion), low NO3- correlated with increased root branching and IAA correlated with increased root elongation and GH3-2 expression. However, under high soil nutrient conditions (inoculation), a high NH4+ to NO3- ratio promoted an increase in root surface area and there was an additional influence of NH4+ and NO3- on GH3-2 expression. Thus it was concluded that soil bacterial-feeding nematodes influenced soil nutritional status and soil IAA content, promoting root growth via an auxin dependent pathway that was offset by soil nitrogen status. PMID:26841062

Effects of fungal elicitors on seed germination and tissue culture of Cymbidium goeringii

NASA Astrophysics Data System (ADS)

Gong, Mingfu; Guan, Qinlan; Lin, Tianxing; Lan, Juming; Liu, Si

2018-04-01

The endophytic fungi were isolated from the roots of Cymbidium goeringii and Cymbidium faberi and were made into liquid fungal elicitors used to co-fungus germination of seeds of C. goeringii and C. faberi. The results showed that the germination rate of the seeds of C. goeringii was increased 15% to 30% by inoculating the mixed fungal elicitors of C. goeringii and was no significant change by inoculating the mixed fungal elicitors of C. faberi. Mixed fungal elicitor promoted the acclimation of tissue culture seedlings. Mixed fungal elicitor prepared mycorrhizal inoculant made new seedlings easier to survive when transplanted.

Alleviation of Drought Stress and Metabolic Changes in Timothy (Phleum pratense L.) Colonized with Bacillus subtilis B26

PubMed Central

Gagné-Bourque, François; Bertrand, Annick; Claessens, Annie; Aliferis, Konstantinos A.; Jabaji, Suha

2016-01-01

Drought is a major limiting factor of crop productivity worldwide and its incidence is predicted to increase under climate change. Drought adaptation of cool-season grasses is thus a major challenge to secure the agricultural productivity under current and future climate conditions. Endophytes are non-pathogenic plant-associated bacteria that can play an important role in conferring resistance and improving plant tolerance to drought. In this study, the effect of inoculation of the bacterial endophyte Bacillus subtilis strain B26 on growth, water status, photosynthetic activity and metabolism of timothy (Phleum pratense L.) subjected to drought stress was investigated under controlled conditions. Under both drought-stress and non-stressed conditions, strain B26 successfully colonized the internal tissues of timothy and had a positive impact on plant growth. Exposure of inoculated plant to a 8-week drought-stress led to significant increase in shoot and root biomass by 26.6 and 63.8%, and in photosynthesis and stomatal conductance by 55.2 and 214.9% respectively, compared to non-inoculated plants grown under similar conditions. There was a significant effect of the endophyte on plant metabolism; higher levels of several sugars, notably sucrose and fructans and an increase of key amino acids such as, asparagine, glutamic acid and glutamine were recorded in shoots and roots of colonized plants compared to non-colonized ones. The accumulation of the non-protein amino acid GABA in shoots of stressed plants and in roots of stressed and unstressed plants was increased in the presence of the endophyte. Taken together, our results indicate that B. subtilis B26 improves timothy growth under drought stress through the modification of osmolyte accumulation in roots and shoots. These results will contribute to the development of a microbial agent to improve the yield of grass species including forage crops and cereals exposed to environmental stresses. PMID:27200057

Effect of Arbuscular Mycorrhizal Fungi On Yield and Phytoremediation Performance of Pot Marigold (Calendula officinalis L.) Under Heavy Metals Stress.

PubMed

Tabrizi, Leila; Mohammadi, Siavash; Delshad, Mojtaba; Moteshare Zadeh, Babak

2015-01-01

In order to study the effect of mycorrhizal fungi (inoculated and non-inoculated) and heavy metals stress [0, Pb (150 and 300 mg/kg) and Cd (40 and 80 mg/kg)] on pot marigold (Calendula officinalis L.), a factorial experiment was conducted based on a randomized complete block design with 4 replications in Research Greenhouse of Department of Horticultural Sciences, University of Tehran, Iran, during 2012-2013. Plant height, herbal and flower fresh and dry weight, root fresh and dry weight and root volume, colonization percentage, total petal extract, total petal flavonoids, root and shoot P and K uptakes, and Pb and Cd accumulations in root and shoot were measured. Results indicated that with increasing soil Pb and Cd concentration, growth and yield of pot marigold was reduced significantly; Cd had greater negative impacts than Pb. However, mycorrhizal fungi alleviated these impacts by improving plant growth and yield. Pot marigold concentrated high amounts of Pb and especially Cd in its roots and shoots; mycorrhizal plants had a greater accumulation of these metals, so that those under 80 mg/kg Cd soil(-1) accumulated 833.3 and 1585.8 mg Cd in their shoots and roots, respectively. In conclusion, mycorrhizal fungi can improve not only growth and yield of pot marigold in heavy metal stressed condition, but also phytoremediation performance by increasing heavy metals accumulation in the plant organs.

Inoculation of a phenanthrene-degrading endophytic bacterium reduces the phenanthrene level and alters the bacterial community structure in wheat.

PubMed

Liu, Juan; Xiang, Yanbing; Zhang, Zhiming; Ling, Wanting; Gao, Yanzheng

2017-06-01

Colonization by polycyclic aromatic hydrocarbon (PAH)-degrading endophytic bacteria (PAHDEB) can reduce the PAH contamination risk in plant. However, little information is available on the impact of PAHDEB colonization on the endophytic bacterial community of inner plant tissues. A phenanthrene-degrading endophytic bacterium (PDEB), Massilia sp. Pn2, was inoculated onto the roots of wheat and subjected to greenhouse container experiments. The endophytic bacterial community structure in wheat was investigated using high-throughput sequencing technology. The majority of endophytic bacteria in wheat were Proteobacteria, and the dominant genus was Pseudomonas. Phenanthrene contamination clearly increased the diversity of endophytic bacteria in wheat. The cultivable endophytic bacteria counts in wheat decreased with increasing the level of phenanthrene contamination; the endophytic bacterial community structure changed correspondingly, and the bacterial richness first increased and then decreased. Inoculation of strain Pn2 reduced the phenanthrene contamination in wheat, enlarged the biomass of wheat roots, changed the bacterial community structure and enhanced the cell counts, diversity and richness of endophytic bacteria in phenanthrene-contaminated wheat in a contamination level-dependent manner. The findings of this investigation provide insight into the responses of endophytic bacterial community in plant to external PAH contamination and PAHDEB colonization.

The effects of arbuscular mycorrhizal fungal inoculation at a roadside prairie restoration site.

PubMed

White, Jennifer A; Tallaksen, J; Charvat, I

2008-01-01

Arbuscular mycorrhizal fungi (AMF) may play an important role in ecological succession, but few studies have documented the effectiveness of mycorrhizal inoculation at restoration/reclamation sites. At a roadside prairie restoration in Shakopee, Minnesota, we compared AMF root colonization and resulting vegetative cover among four inoculation treatments. After 15 mo of growth, we found that AMF colonization was high in all treatments but was significantly higher in treatments that received AMF inoculum propagated from a local prairie site or commercially available inoculum than the uninoculated control. For the prairie inoculum, this increase in colonization occurred whether the inoculum was applied with seeds in furrows or broadcast with seeds on the soil surface. However, increased colonization did not discernibly affect the restored vegetation; neither total vegetative cover nor the proportion "desired" prairie vegetation differed among inoculation treatments. By the end of the third growing season (27 mo after planting) there were no longer differences in AMF colonization among the inoculation treatments nor were there differences in vegetative cover. It is likely that natural recolonization of the plots by remnant AMF populations at the site limited the duration of the inoculation effect. This natural recolonization, in combination with relatively high soil phosphorus levels, likely rendered inoculation unnecessary. In contrast to previous published studies of AMF inoculation in landscape restorations, this study shows that AMF inoculation may not be warranted under some circumstances.

Inoculating Helianthus annuus (sunflower) grown in zinc and cadmium contaminated soils with plant growth promoting bacteria--effects on phytoremediation strategies.

PubMed

Marques, Ana P G C; Moreira, Helena; Franco, Albina R; Rangel, António O S S; Castro, Paula M L

2013-06-01

Plant growth promoting bacteria (PGPR) may help reducing the toxicity of heavy metals to plants in polluted environments. In this work the effects of inoculating metal resistant and plant growth promoting bacterial strains on the growth of Helianthus annuus grown in Zn and Cd spiked soils were assessed. The PGPR strains Ralstonia eutropha (B1) and Chrysiobacterium humi (B2) reduced losses of weight in metal exposed plants and induced changes in metal bioaccumulation and bioconcentration - with strain B2 decreasing up to 67% Zn accumulation and by 20% Zn bioconcentration factor (BCF) in the shoots, up to 64% Zn uptake and 38% Zn BCF in the roots, and up to 27% Cd uptake and 27% Cd BCF in plant roots. The impact of inoculation on the bacterial communities in the rhizosphere of the plant was also assessed. Bacterial community diversity decreased with increasing levels of metal contamination in the soil, but in rhizosphere soil of plants inoculated with the PGPR strains, a higher bacterial diversity was kept throughout the experimental period. Inoculation of sunflower, particularly with C. humi (B2), appears to be an effective way of enhancing the short term stabilization potential of the plant in metal contaminated land, lowering losses in plant biomass and decreasing aboveground tissue contamination. Copyright © 2013 Elsevier Ltd. All rights reserved.

Differential Response of Potato Toward Inoculation with Taxonomically Diverse Plant Growth Promoting Rhizobacteria.

PubMed

Naqqash, Tahir; Hameed, Sohail; Imran, Asma; Hanif, Muhammad Kashif; Majeed, Afshan; van Elsas, Jan Dirk

2016-01-01

Rhizosphere engineering with beneficial plant growth promoting bacteria offers great promise for sustainable crop yield. Potato is an important food commodity that needs large inputs of nitrogen and phosphorus fertilizers. To overcome high fertilizer demand (especially nitrogen), five bacteria, i.e., Azospirillum sp. TN10, Agrobacterium sp. TN14, Pseudomonas sp. TN36, Enterobacter sp. TN38 and Rhizobium sp. TN42 were isolated from the potato rhizosphere on nitrogen-free malate medium and identified based on their 16S rRNA gene sequences. Three strains, i.e., TN10, TN38, and TN42 showed nitrogen fixation (92.67-134.54 nmol h(-1)mg(-1) protein), while all showed the production of indole-3-acetic acid (IAA), which was significantly increased by the addition of L-tryptophan. Azospirillum sp. TN10 produced the highest amount of IAA, as measured by spectrophotometry (312.14 μg mL(-1)) and HPLC (18.3 μg mL(-1)). Inoculation with these bacteria under axenic conditions resulted in differential growth responses of potato. Azospirillum sp. TN10 incited the highest increase in potato fresh and dry weight over control plants, along with increased N contents of shoot and roots. All strains were able to colonize and maintain their population densities in the potato rhizosphere for up to 60 days, with Azospirillum sp. and Rhizobium sp. showing the highest survival. Plant root colonization potential was analyzed by transmission electron microscopy of root sections inoculated with Azospirillum sp. TN10. Of the five test strains, Azospirillum sp. TN10 has the greatest potential to increase the growth and nitrogen uptake of potato. Hence, it is suggested as a good candidate for the production of potato biofertilizer for integrated nutrient management.

Inoculation of hybrid poplar with the endophytic bacterium Enterobacter sp. 638 increases biomass but does not impact leaf level physiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, A.; McDonald, K.; Muehlbauer, M. F.

Endophytic bacteria have been shown to provide several advantages to their host, including enhanced growth. Inoculating biofuel species with endophytic bacteria is therefore an attractive option to increase the productivity of biofuel feedstocks. Here, we investigated the effect of inoculating hard wood cuttings of Populus deltoides Bartr. x Populus. nigra L. clone OP367 with Enterobacter sp. 638. After 17 weeks, plants inoculated with Enterobacter sp. 638 had 55% greater total biomass than un-inoculated control plants. Study of gas exchange and fluorescence in developing and mature leaves over a diurnal cycle and over a 5 week measurement campaign revealed no effectsmore » of inoculation on photosynthesis, stomatal conductance, photosynthetic water use efficiency or the maximum and operating efficiency of photosystem II. However, plants inoculated with Enterobacter sp. 638 had a canopy that was 39% larger than control plants indicating that the enhanced growth was fueled by increased leaf area, not by improved physiology. Leaf nitrogen content was determined at two stages over the 5 week measurement period. No effect of Enterobacter sp. 638 on leaf nitrogen content was found indicating that the larger plants were acquiring sufficient nitrogen. Enterobacter sp. 638 lacks the genes for N{sub 2} fixation, therefore the increased availability of nitrogen likely resulted from enhanced nitrogen acquisition by the 84% larger root system. These data show that Enterobacter sp. 638 has the potential to dramatically increase productivity in poplar. If fully realized in the production environment, these results indicate that an increase in the environmental and economic viability of poplar as a biofuel feedstock is possible when inoculated with endophytic bacteria like Enterobacter sp. 638.« less

[Screening and identification of endophytic fungi with growth promoting effect on Dendrobium officinale].

PubMed

Hou, Xiao-qiang; Guo, Shun-xing

2014-09-01

The endophytic fungi with plant growth promoting effects were screened by co-culture of each endophytic fungus and seedlings of Dendrobium officinale. Anatomical features of the inoculated roots were studied by paraffin sectioning. Morphological characteristics and rDNA ITS1-5. 8S-ITS2 sequences were applied for the taxonomy of endophytic fungi. The results showed that 8 strains inoculated to D. officinale seedlings greatly enhanced plant height, stem diameter, new roots number and biomass. According to the anatomical features of the inoculated roots, each fungus could infect the velamina of seedlings. The hyphae or pelotons were existed in the exodermis passage cells and cortex cells. The effective fungi could not infect the endodermis and vascular bundle sheath, but which was exception for other fungi with harmful to seedlings. Combined with classic morphologic classification, 2 effective strains were identified which were subjected to Pestalotiopsis and Eurotium. Six species of fungi without conidiophore belonged to Pyrenochaeta, Coprinellus, Pholiota, Alternaria, Helotiales, which were identified by sequencing the PCR-amplified rDNA ITS1-5. 8S-ITS2 regions. The co-culture technology of effective endophytic fungi and plant can apply to cultivate the seedlings of D. officinale. It is feasible to shorten growth cycle of D. officinale and increase the resource of Chinese herbs.

Association of plant growth-promoting Serratia spp. with the root nodules of chickpea.

PubMed

Zaheer, Ahmad; Mirza, Babur S; Mclean, Joan E; Yasmin, Sumera; Shah, Tariq Mahmud; Malik, Kauser A; Mirza, M Sajjad

2016-01-01

Serratia species-affiliated DNA sequences have recently been discovered in the root nodules of two chickpea cultivars; however, little is known about their potential influence on chickpea plant growth. All Serratia-affiliated sequences (1136) could be grouped into two clusters at 98% DNA similarity. The major cluster, represented by 96% of sequences, was closely associated with Serratia marcescens sequences from GenBank. In the current study, we isolated two Serratia strains, 5D and RTL100, from root nodules of a field-grown Desi cultivar from Faisalabad and Thal areas, respectively. In vitro, strain 5D showed significantly higher phosphate (P) solubilization and lactic acid production than RTL100, whereas a comparable concentration of phytohormone was produced by both isolates. The application of Serratia strain 5D as an inoculum resulted in 25.55% and 30.85% increases in the grain yield of crops grown on fertile soil in irrigated areas and nutrient-deficient soil in rainfed areas, respectively, compared to the non-inoculated control. Results of plant inoculations indicated that Serratia sp. 5D and RTL100 can serve as effective microbial inoculants, particularly in nutrient-deficient soils in rainfed areas, where chickpea is the only major crop grown during the entire year. Copyright © 2016 Institut Pasteur. All rights reserved.

Transcriptome changes induced by arbuscular mycorrhizal fungi in sunflower (Helianthus annuus L.) roots.

PubMed

Vangelisti, Alberto; Natali, Lucia; Bernardi, Rodolfo; Sbrana, Cristiana; Turrini, Alessandra; Hassani-Pak, Keywan; Hughes, David; Cavallini, Andrea; Giovannetti, Manuela; Giordani, Tommaso

2018-01-08

Arbuscular mycorrhizal (AM) fungi are essential elements of soil fertility, plant nutrition and productivity, facilitating soil mineral nutrient uptake. Helianthus annuus is a non-model, widely cultivated species. Here we used an RNA-seq approach for evaluating gene expression variation at early and late stages of mycorrhizal establishment in sunflower roots colonized by the arbuscular fungus Rhizoglomus irregulare. mRNA was isolated from roots of plantlets at 4 and 16 days after inoculation with the fungus. cDNA libraries were built and sequenced with Illumina technology. Differential expression analysis was performed between control and inoculated plants. Overall 726 differentially expressed genes (DEGs) between inoculated and control plants were retrieved. The number of up-regulated DEGs greatly exceeded the number of down-regulated DEGs and this difference increased in later stages of colonization. Several DEGs were specifically involved in known mycorrhizal processes, such as membrane transport, cell wall shaping, and other. We also found previously unidentified mycorrhizal-induced transcripts. The most important DEGs were carefully described in order to hypothesize their roles in AM symbiosis. Our data add a valuable contribution for deciphering biological processes related to beneficial fungi and plant symbiosis, adding an Asteraceae, non-model species for future comparative functional genomics studies.

Grain yield and arsenic uptake of upland rice inoculated with arbuscular mycorrhizal fungi in As-spiked soils.

PubMed

Wu, Fuyong; Hu, Junli; Wu, Shengchun; Wong, Ming Hung

2015-06-01

A pot trial was conducted to investigate the effects of three arbuscular mycorrhizal (AM) fungi species, including Glomus geosporum BGC HUN02C, G. versiforme BGC GD01B, and G. mosseae BGC GD01A, on grain yield and arsenic (As) uptake of upland rice (Zhonghan 221) in As-spiked soils. Moderate levels of AM colonization (24.1-63.1 %) were recorded in the roots of upland rice, and up to 70 mg kg(-1) As in soils did not seem to inhibit mycorrhizal colonization. Positive mycorrhizal growth effects in grain, husk, straw, and root of the upland rice, especially under high level (70 mg kg(-1)) of As in soils, were apparent. Although the effects varied among species of AM fungi, inoculation of AM fungi apparently enhanced grain yield of upland rice without increasing grain As concentrations in As-spiked soils, indicating that AM fungi could alleviate adverse effects on the upland rice caused by As in soils. The present results also show that mycorrhizal inoculation significantly (p < 0.05) decreased As concentrations in husk, straw, and root in soils added with 70 mg kg(-1) As. The present results suggest that AM fungi are able to mitigate the adverse effects with enhancing rice production when growing in As-contaminated soils.

Pongamia pinnata inoculated with Bradyrhizobium liaoningense PZHK1 shows potential for phytoremediation of mine tailings.

PubMed

Yu, Xiumei; Li, Yangxin; Li, Yanmei; Xu, Chaohua; Cui, Yongliang; Xiang, Quanju; Gu, Yunfu; Zhao, Ke; Zhang, Xiaoping; Penttinen, Petri; Chen, Qiang

2017-02-01

Mine tailings contain high concentrations of metal contaminants and only little nutrients, making the tailings barren for decades after the mining has been terminated. Effective phytoremediation of mine tailings calls for deep-rooted, metal accumulating, and soil fertility increasing plants with tolerance against harsh environmental conditions. We assessed the potential of the biofuel leguminous tree Pongamia pinnata inoculated with plant growth promoting rhizobia to remediate iron-vanadium-titanium oxide (V-Ti magnetite) mine tailing soil by pot experiment and in situ remediation test. A metal tolerant rhizobia strain PZHK1 was isolated from the tailing soil and identified as Bradyrhizobium liaoningense by phylogenetic analysis. Inoculation with PZHK1 increased the growth of P. pinnata both in V-Ti magnetite mine tailings and in Ni-contaminated soil. Furthermore, inoculation increased the metal accumulation capacity and superoxide dismutase activity of P. pinnata. The concentrations of Ni accumulated by inoculated plants were higher than the hyperaccumulator threshold. Inoculated P. pinnata accumulated high concentration of Fe, far exceeding the upper limit (1000 mg kg -1 ) of Fe in plant tissue. In summary, P. pinnata-B. liaoningense PZHK1 symbiosis showed potential to be applied as an effective phytoremediation technology for mine tailings and to produce biofuel feedstock on the marginal land.

Effects of inoculating Lachnum and Cadophora isolates on the growth of Vaccinium corymbosum.

PubMed

Bizabani, Christine; Dames, Joanna

2015-12-01

The roots of ericaceous plants harbour a diversity of fungal taxa, which confer eco-physiological benefits to the host. Some of the fungi have been established to form ericoid mycorrhizal (ERM) associations and enhance plant growth in certain ericaceous genera. Although, Lachnum and Cadophora isolates have frequently been identified from the roots of this family, the status of their association and functional roles is still vague. The aims of this study were to identify Lachnum and Cadophora isolates; determine the root-fungal interactive structures formed in associations with Vaccinium corymbosum L. (blueberry) hosts and to examine inoculation effects of the fungal associates using several varieties of the blueberry. Lachnum and Cadophora were isolated and identified from Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth using morphological and molecular techniques. Micropropagated blueberry varieties (Bluecrop, Elliott, Spartan, Chandler and Brightwell) were inoculated with respective fungi and plant growth evaluated. Both fungi colonised the roots and did not have any pathogenic effect. Lachnum isolate did not form any particular mycorrhizal structures whereas; Cadophora inoculated plants showed typical ericoid mycorrhizal coils. Inoculation with both fungi enhanced the shoot growth of Brightwell and Elliott varieties. However neutral effects were observed in the remaining varieties. In conclusion, Cadophora and Lachnum isolates have potential to promote growth of selected blueberry varieties. Copyright © 2015 Elsevier GmbH. All rights reserved.

Comparative Transcriptome Analysis of Resistant and Susceptible Common Bean Genotypes in Response to Soybean Cyst Nematode Infection.

PubMed

Jain, Shalu; Chittem, Kishore; Brueggeman, Robert; Osorno, Juan M; Richards, Jonathan; Nelson, Berlin D

2016-01-01

Soybean cyst nematode (SCN; Heterodera glycines Ichinohe) reproduces on the roots of common bean (Phaseolus vulgaris L.) and can cause reductions in plant growth and seed yield. The molecular changes in common bean roots caused by SCN infection are unknown. Identification of genetic factors associated with SCN resistance could help in development of improved bean varieties with high SCN resistance. Gene expression profiling was conducted on common bean roots infected by SCN HG type 0 using next generation RNA sequencing technology. Two pinto bean genotypes, PI533561 and GTS-900, resistant and susceptible to SCN infection, respectively, were used as RNA sources eight days post inoculation. Total reads generated ranged between ~ 3.2 and 5.7 million per library and were mapped to the common bean reference genome. Approximately 70-90% of filtered RNA-seq reads uniquely mapped to the reference genome. In the inoculated roots of resistant genotype PI533561, a total of 353 genes were differentially expressed with 154 up-regulated genes and 199 down-regulated genes when compared to the transcriptome of non- inoculated roots. On the other hand, 990 genes were differentially expressed in SCN-inoculated roots of susceptible genotype GTS-900 with 406 up-regulated and 584 down-regulated genes when compared to non-inoculated roots. Genes encoding nucleotide-binding site leucine-rich repeat resistance (NLR) proteins, WRKY transcription factors, pathogenesis-related (PR) proteins and heat shock proteins involved in diverse biological processes were differentially expressed in both resistant and susceptible genotypes. Overall, suppression of the photosystem was observed in both the responses. Furthermore, RNA-seq results were validated through quantitative real time PCR. This is the first report describing genes/transcripts involved in SCN-common bean interaction and the results will have important implications for further characterization of SCN resistance genes in common bean.

Comparative Transcriptome Analysis of Resistant and Susceptible Common Bean Genotypes in Response to Soybean Cyst Nematode Infection

PubMed Central

Jain, Shalu; Chittem, Kishore; Brueggeman, Robert; Osorno, Juan M.; Richards, Jonathan; Nelson, Berlin D.

2016-01-01

Soybean cyst nematode (SCN; Heterodera glycines Ichinohe) reproduces on the roots of common bean (Phaseolus vulgaris L.) and can cause reductions in plant growth and seed yield. The molecular changes in common bean roots caused by SCN infection are unknown. Identification of genetic factors associated with SCN resistance could help in development of improved bean varieties with high SCN resistance. Gene expression profiling was conducted on common bean roots infected by SCN HG type 0 using next generation RNA sequencing technology. Two pinto bean genotypes, PI533561 and GTS-900, resistant and susceptible to SCN infection, respectively, were used as RNA sources eight days post inoculation. Total reads generated ranged between ~ 3.2 and 5.7 million per library and were mapped to the common bean reference genome. Approximately 70–90% of filtered RNA-seq reads uniquely mapped to the reference genome. In the inoculated roots of resistant genotype PI533561, a total of 353 genes were differentially expressed with 154 up-regulated genes and 199 down-regulated genes when compared to the transcriptome of non- inoculated roots. On the other hand, 990 genes were differentially expressed in SCN-inoculated roots of susceptible genotype GTS-900 with 406 up-regulated and 584 down-regulated genes when compared to non-inoculated roots. Genes encoding nucleotide-binding site leucine-rich repeat resistance (NLR) proteins, WRKY transcription factors, pathogenesis-related (PR) proteins and heat shock proteins involved in diverse biological processes were differentially expressed in both resistant and susceptible genotypes. Overall, suppression of the photosystem was observed in both the responses. Furthermore, RNA-seq results were validated through quantitative real time PCR. This is the first report describing genes/transcripts involved in SCN-common bean interaction and the results will have important implications for further characterization of SCN resistance genes in common bean. PMID:27441552

Pseudomonas fluorescens CHA0 maintains carbon delivery to Fusarium graminearum-infected roots and prevents reduction in biomass of barley shoots through systemic interactions

PubMed Central

Henkes, Gunnar J.; Jousset, Alexandre; Bonkowski, Michael; Thorpe, Michael R.; Scheu, Stefan; Lanoue, Arnaud; Schurr, Ulrich; Röse, Ursula S. R.

2011-01-01

Soil bacteria such as pseudomonads may reduce pathogen pressure for plants, both by activating plant defence mechanisms and by inhibiting pathogens directly due to the production of antibiotics. These effects are hard to distinguish under field conditions, impairing estimations of their relative contributions to plant health. A split-root system was set up with barley to quantify systemic and local effects of pre-inoculation with Pseudomonas fluorescens on the subsequent infection process by the fungal pathogen Fusarium graminearum. One root half was inoculated with F. graminearum in combination with P. fluorescens strain CHA0 or its isogenic antibiotic-deficient mutant CHA19. Bacteria were inoculated either together with the fungal pathogen or in separate halves of the root system to separate local and systemic effects. The short-term plant response to fungal infection was followed by using the short-lived isotopic tracer 11CO2 to track the delivery of recent photoassimilates to each root half. In the absence of bacteria, fungal infection diverted carbon from the shoot to healthy roots, rather than to infected roots, although the overall partitioning from the shoot to the entire root system was not modified. Both local and systemic pre-inoculation with P. fluorescens CHA0 prevented the diversion of carbon as well as preventing a reduction in plant biomass in response to F. graminearum infection, whereas the non-antibiotic-producing mutant CHA19 lacked this ability. The results suggest that the activation of plant defences is a central feature of biocontrol bacteria which may even surpass the effects of direct pathogen inhibition. PMID:21561952

Arbuscular Mycorrhizal Fungus Enhances Lateral Root Formation in Poncirus trifoliata (L.) as Revealed by RNA-Seq Analysis

PubMed Central

Chen, Weili; Li, Juan; Zhu, Honghui; Xu, Pengyang; Chen, Jiezhong; Yao, Qing

2017-01-01

Arbuscular mycorrhizal fungi (AMF) establish symbiosis with most terrestrial plants, and greatly regulate lateral root (LR) formation. Phosphorus (P), sugar, and plant hormones are proposed being involved in this regulation, however, no global evidence regarding these factors is available so far, especially in woody plants. In this study, we inoculated trifoliate orange seedlings (Poncirus trifoliata L. Raf) with an AMF isolate, Rhizophagus irregularis BGC JX04B. After 4 months of growth, LR formation was characterized, and sugar contents in roots were determined. RNA-Seq analysis was performed to obtain the transcriptomes of LR root tips from non-mycorrhizal and mycorrhizal seedlings. Quantitative real time PCR (qRT-PCR) of selected genes was also conducted for validation. The results showed that AMF significantly increased LR number, as well as plant biomass and shoot P concentration. The contents of glucose and fructose in primary root, and sucrose content in LR were also increased. A total of 909 differentially expressed genes (DEGs) were identified in response to AMF inoculation, and qRT-PCR validated the transcriptomic data. The numbers of DEGs related to P, sugar, and plant hormones were 31, 32, and 25, respectively. For P metabolism, the most up-regulated DEGs mainly encoded phosphate transporter, and the most down-regulated DEGs encoded acid phosphatase. For sugar metabolism, the most up-regulated DEGs encoded polygalacturonase and chitinase. For plant hormones, the most up-regulated DEGs were related to auxin signaling, and the most down-regulated DEGs were related to ethylene signaling. PLS-SEM analysis indicates that P metabolism was the most important pathway by which AMF regulates LR formation in this study. These data reveal the changes of genome-wide gene expression in responses to AMF inoculation in trifoliate orange and provide a solid basis for the future identification and characterization of key genes involved in LR formation induced by AMF. PMID:29238356

Arbuscular Mycorrhizal Fungus Enhances Lateral Root Formation in Poncirus trifoliata (L.) as Revealed by RNA-Seq Analysis.

PubMed

Chen, Weili; Li, Juan; Zhu, Honghui; Xu, Pengyang; Chen, Jiezhong; Yao, Qing

2017-01-01

Arbuscular mycorrhizal fungi (AMF) establish symbiosis with most terrestrial plants, and greatly regulate lateral root (LR) formation. Phosphorus (P), sugar, and plant hormones are proposed being involved in this regulation, however, no global evidence regarding these factors is available so far, especially in woody plants. In this study, we inoculated trifoliate orange seedlings ( Poncirus trifoliata L. Raf) with an AMF isolate, Rhizophagus irregularis BGC JX04B. After 4 months of growth, LR formation was characterized, and sugar contents in roots were determined. RNA-Seq analysis was performed to obtain the transcriptomes of LR root tips from non-mycorrhizal and mycorrhizal seedlings. Quantitative real time PCR (qRT-PCR) of selected genes was also conducted for validation. The results showed that AMF significantly increased LR number, as well as plant biomass and shoot P concentration. The contents of glucose and fructose in primary root, and sucrose content in LR were also increased. A total of 909 differentially expressed genes (DEGs) were identified in response to AMF inoculation, and qRT-PCR validated the transcriptomic data. The numbers of DEGs related to P, sugar, and plant hormones were 31, 32, and 25, respectively. For P metabolism, the most up-regulated DEGs mainly encoded phosphate transporter, and the most down-regulated DEGs encoded acid phosphatase. For sugar metabolism, the most up-regulated DEGs encoded polygalacturonase and chitinase. For plant hormones, the most up-regulated DEGs were related to auxin signaling, and the most down-regulated DEGs were related to ethylene signaling. PLS-SEM analysis indicates that P metabolism was the most important pathway by which AMF regulates LR formation in this study. These data reveal the changes of genome-wide gene expression in responses to AMF inoculation in trifoliate orange and provide a solid basis for the future identification and characterization of key genes involved in LR formation induced by AMF.

PGPR strain Paenibacillus polymyxa SQR-21 potentially benefits watermelon growth by re-shaping root protein expression.

PubMed

E, Yaoyao; Yuan, Jun; Yang, Fang; Wang, Lei; Ma, Jinghua; Li, Jing; Pu, Xiaowei; Raza, Waseem; Huang, Qiwei; Shen, Qirong

2017-12-01

Paenibacillus polymyxa (SQR-21) is not only a plant growth-promoting rhizobacteria, but also an effective biocontrol agent against Fusarium wilt disease of watermelon. For the better understanding and clarifying the potential mechanisms of SQR-21 to improve watermelon growth and disease resistance, a split-root methodology in hydroponic and LC-MS technology with the label free method was used to analyze the key root proteins involved in watermelon metabolism and disease resistance after the inoculation of SQR-21. Out of 623 identified proteins, 119 proteins were differentially expressed when treatment (SQR-21 inoculation) and control (no bacterial inoculation) were compared. Among those, 57 and 62 proteins were up-regulated and down-regulated, respectively. These differentially expressed proteins were identified to be involved in signal transduction (ADP-ribosylation factor, phospholipase D), transport (aspartate amino-transferase), carbohydratemetabolic (glucose-6-phosphate dehydrogenase, UDP-glucose pyrophosphorylase), defense and response to stress (glutathione S-transferase, Ubiquitin-activating enzyme E1), and oxidation-reduction process (thioredoxin peroxidase, ascorbate peroxidase). The results of this study indicated that SQR-21 inoculation on the watermelon roots benefits plant by inducing the expression of several proteins involved in growth, photosynthesis, and other metabolic and physiological activities.

Structural Interaction Between GFP-Labeled Diazotrophic Endophytic Bacterium Herbaspirillum seropedicae RAM10 and Pineapple Plantlets ‘VitóRia’

PubMed Central

Estrela Borges Baldotto, Lílian; Lopes Olivares, Fábio; Bressan-Smith, Ricardo

2011-01-01

The events involved in the structural interaction between the diazotrophic endophytic bacterium Herbaspirillum seropedicae, strain RAM10, labeled with green fluorescent protein, and pineapple plantlets ‘Vitória’ were evaluated by means of bright-field and fluorescence microscopy, combined with scanning electron microscopy for 28 days after inoculation. After 6 hours of inoculation, H. seropedicae was already adhered to the roots, colonizing mainly root hair surface and bases, followed by epidermal cell wall junctions. Bacteria adherence in the initial periods occurred mainly in the form of solitary cells and small aggregates with pleomorphic cells. Bacteria infection of root tissue occurred through the cavities caused by the disruption of epidermal cells during the emergence of lateral roots and the endophytic establishment by the colonization of intercellular spaces of the cortical parenchyma. Moreover, within 1 day after inoculation the bacteria were colonizing the shoots. In this region, the preferred sites of epiphytic colonization were epidermal cell wall junctions, peltate scutiform trichomes and non-glandular trichomes. Subsequently, the bacteria occupied the outer periclinal walls of epidermal cells and stomata. The penetration into the shoot occurred passively through stoma aperture followed by the endophytic establishment on the substomatal chambers and spread to the intercellular spaces of spongy chlorenchyma. After 21 days of inoculation, bacterial biofilm were seen at the root hair base and on epidermal cell wall surface of root and leaf, also confirming the epiphytic nature of H. seropedicae. PMID:24031612

Structural Interaction Between GFP-Labeled Diazotrophic Endophytic Bacterium Herbaspirillum seropedicae RAM10 and Pineapple Plantlets 'VitóRia'.

PubMed

Estrela Borges Baldotto, Lílian; Lopes Olivares, Fábio; Bressan-Smith, Ricardo

2011-01-01

The events involved in the structural interaction between the diazotrophic endophytic bacterium Herbaspirillum seropedicae, strain RAM10, labeled with green fluorescent protein, and pineapple plantlets 'Vitória' were evaluated by means of bright-field and fluorescence microscopy, combined with scanning electron microscopy for 28 days after inoculation. After 6 hours of inoculation, H. seropedicae was already adhered to the roots, colonizing mainly root hair surface and bases, followed by epidermal cell wall junctions. Bacteria adherence in the initial periods occurred mainly in the form of solitary cells and small aggregates with pleomorphic cells. Bacteria infection of root tissue occurred through the cavities caused by the disruption of epidermal cells during the emergence of lateral roots and the endophytic establishment by the colonization of intercellular spaces of the cortical parenchyma. Moreover, within 1 day after inoculation the bacteria were colonizing the shoots. In this region, the preferred sites of epiphytic colonization were epidermal cell wall junctions, peltate scutiform trichomes and non-glandular trichomes. Subsequently, the bacteria occupied the outer periclinal walls of epidermal cells and stomata. The penetration into the shoot occurred passively through stoma aperture followed by the endophytic establishment on the substomatal chambers and spread to the intercellular spaces of spongy chlorenchyma. After 21 days of inoculation, bacterial biofilm were seen at the root hair base and on epidermal cell wall surface of root and leaf, also confirming the epiphytic nature of H. seropedicae.

Inoculating wheat (Triticum aestivum L.) with the endophytic bacterium Serratia sp. PW7 to reduce pyrene contamination.

PubMed

Zhu, Xuezhu; Wang, Wanqing; Sun, Kai; Lin, Xianghao; Li, Shuang; Waigi, Michael Gatheru; Ling, Wanting

2017-08-03

This research was conducted to find an optimal inoculation way for a pyrene-degrading endophytic Serratia sp. PW7 to colonize wheat for reducing pyrene contamination. Three inoculation ways, which are soaking seeds in inocula (TS), dipping roots of seedlings in inocula (TR), and spraying inocula on leaves of seedlings (TL), were used in this study. Inoculated seedlings and noninoculated seedlings (CK) were, respectively, cultivated in Hoagland solutions supplemented with pyrene in a growth chamber. The results showed that strain PW7 successfully colonized the inoculated seedlings in high numbers, and significantly promoted the growth of seedlings (TS and TR). More importantly, strain PW7 reduced pyrene levels in the seedlings and the Hoagland solutions. Compared to the noninoculated seedlings, the pyrene contents of the inoculated seedlings were decreased by 35.7-86.3% in the shoots and by 26.8-60.1% in the roots after 8-day cultivation. By comparing the efficiencies of decreasing pyrene residues, it can be concluded that TR was an optimal inoculation way for endophytic strains to colonize the inoculated plants and to reduce the pyrene contamination. Our findings provide an optimized inoculation way to reduce organic contamination in crops by inoculating plants with functional endophytic bacteria.

[Rhizosphere microbial impacts of alleviating faba bean Fusarium wilt with inoculating AM fungi].

PubMed

Dong, Yan; Dong, Kun; Yang, Zhi Xian; Tang, Li; Zheng, Yi

2016-12-01

Greenhouse pot trials were conducted to investigate the effects of arbuscular mycorrhizal fungus (Glomus mosseae, Glomus tortuosum, Glomus intraradices and Glomus etunicatum) inoculation on the seedling growth, occurance of Fusarium wilt, population of Fusarium oxysporum and rhizosphere microbial community functional diversity in faba bean rhizosphere soil. Results showed that after inoculation of G. mosseae, G. tortuosum, G. intraradices and G. etunicatum, the shoot and root fresh mass of faba bean seedlings increased significantly, the disease index of faba bean fusarium wilt decreased significantly by 94.0%, 60.0%, 64.0% and 94.0%, respectively, the amount of F. oxysporum of faba bean rhizosphere decreased significantly by 98.6%, 74.3%, 77.8% and 90.4%, respectively. The best inhibitory effects to Fusarium wilt were with G. mosseae and G. etunicatum treatments. Inoculation of G. mosseae, G. tortuosum and G. etunicatum significantly increased carbon sources utilization ability of carbohydrates, amino acids, carboxylic acids and phenolic acids, with the average well color development (AWCD) value being increased by 34.4%, 31.5% and 50.8% respectively, but such significant differences were not observed with inoculation of G. intraradice. Principal component analyses showed that inoculation of G. mosseae, G. tortuosum and G. etunicatum fungi changed the rhizospheric microbial community composition. Correlation analyses showed that the utilization of carbohydrates carbon sources (β-Methyl-D-glucoside, D-Galacturonic acid, D-Mannitol, N-Acetyl-D-Glucosamine, D-Cellobiose,) and carboxylic acids carbon sources (D-Galactonic acid-γ-Lactone) were significantly increased after inoculation of G. tortuosum, and the utilization of L-Arginine and 4-Hydroxy benzoic acid significantly increased after inoculation of G. mosseae and G. etunicatum. Carbohydrates, carboxylic acids were main carbon sources utilized by rhizosphere microbes after G. tortuosum and G. intraradices inoculation, and amino acids and phenolic acids were main carbon sources utilized by rhizosphere microbes after G. mosseae and G. etunicatum inoculation. Inoculation of AM fungi significantly increased the activities of rhizosphere microbes, changed soil microbe community functional diversity, and thus inhibited the growth of F. oxysporum. The inhibitory impacts of AM fungi inoculations depended on the changes of microbes utilizing carbon sources.

Light Requirement for Shoot Regeneration in Horseradish Hairy Roots 1

PubMed Central

Saitou, Tsutomu; Kamada, Hiroshi; Harada, Hiroshi

1992-01-01

Hairy roots of horseradish (Armoracia rusticana) were induced by inoculation with Agrobacterium rhizogenes harboring Ri plasmid and cultured on phytohormone-free Murashige and Skoog medium after eliminating the bacteria. Hairy roots grew vigorously and sometimes formed yellowish calli under dark conditions. On the other hand, growth of hairy roots stopped after several weeks of culture with light, then shoots were regenerated. Frequency of shoot formation from hairy roots increased as the culture period in light lengthened and the light intensity increased. The shoot regeneration was induced by treatment with white or red light, but not with far-red light. Shoot regeneration by red light was inhibited by following treatment with far-red light. Red and far-red light reversibly affected shoot regeneration. Excised roots of nontransformed plants grew quite slowly on phytohormone-free Murashige and Skoog medium and occasionally formed shoots under white light conditions. PMID:16669041

Light requirement for shoot regeneration in horseradish hairy roots.

PubMed

Saitou, T; Kamada, H; Harada, H

1992-08-01

Hairy roots of horseradish (Armoracia rusticana) were induced by inoculation with Agrobacterium rhizogenes harboring Ri plasmid and cultured on phytohormone-free Murashige and Skoog medium after eliminating the bacteria. Hairy roots grew vigorously and sometimes formed yellowish calli under dark conditions. On the other hand, growth of hairy roots stopped after several weeks of culture with light, then shoots were regenerated. Frequency of shoot formation from hairy roots increased as the culture period in light lengthened and the light intensity increased. The shoot regeneration was induced by treatment with white or red light, but not with far-red light. Shoot regeneration by red light was inhibited by following treatment with far-red light. Red and far-red light reversibly affected shoot regeneration. Excised roots of nontransformed plants grew quite slowly on phytohormone-free Murashige and Skoog medium and occasionally formed shoots under white light conditions.

Potential of Pseudomonas putida PCI2 for the Protection of Tomato Plants Against Fungal Pathogens.

PubMed

Pastor, Nicolás; Masciarelli, Oscar; Fischer, Sonia; Luna, Virginia; Rovera, Marisa

2016-09-01

Tomato is one of the most economically attractive vegetable crops due to its high yields. Diseases cause significant losses in tomato production worldwide. We carried out Polymerase Chain Reaction studies to detect the presence of genes encoding antifungal compounds in the DNA of Pseudomonas putida strain PCI2. We also used liquid chromatography-electrospray tandem mass spectrometry to detect and quantify the production of compounds that increase the resistance of plants to diseases from culture supernatants of PCI2. In addition, we investigated the presence of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase in PCI2. Finally, PCI2 was used for inoculation of tomato seeds to study its potential biocontrol activity against Fusarium oxysporum MR193. The obtained results showed that no fragments for the encoding genes of hydrogen cyanide, pyoluteorin, 2,4-diacetylphloroglucinol, pyrrolnitrin, or phenazine-1-carboxylic acid were amplified from the DNA of PCI2. On the other hand, PCI2 produced salicylic acid and jasmonic acid in Luria-Bertani medium and grew in a culture medium containing ACC as the sole nitrogen source. We observed a reduction in disease incidence from 53.33 % in the pathogen control to 30 % in tomato plants pre-inoculated with PCI2 as well as increases in shoot and root dry weights in inoculated plants, as compared to the pathogenicity control. This study suggests that inoculation of tomato seeds with P. putida PCI2 increases the resistance of plants to root rot caused by F. oxysporum and that PCI2 produces compounds that may be involved at different levels in increasing such resistance. Thus, PCI2 could represent a non-contaminating management strategy potentially applicable in vegetable crops such as tomato.

Potential of Leguminous Cover Crops in Management of a Mixed Population of Root-knot Nematodes (Meloidogyne spp.)

PubMed Central

Osei, Kingsley; Gowen, Simon R.; Pembroke, Barbara; Brandenburg, Rick L.; Jordan, David L.

2010-01-01

Root-knot nematode is an important pest in agricultural production worldwide. Crop rotation is the only management strategy in some production systems, especially for resource poor farmers in developing countries. A series of experiments was conducted in the laboratory with several leguminous cover crops to investigate their potential for managing a mixture of root-knot nematodes (Meloidogyne arenaria, M. incognita, M. javanica). The root-knot nematode mixture failed to multiply on Mucuna pruriens and Crotalaria spectabilis but on Dolichos lablab the population increased more than 2- fold when inoculated with 500 and 1,000 nematodes per plant. There was no root-galling on M. pruriens and C. spectabilis but the gall rating was noted on D. lablab. Greater mortality of juvenile root-knot nematodes occurred when exposed to eluants of roots and leaves of leguminous crops than those of tomato; 48.7% of juveniles died after 72 h exposure to root eluant of C. spectabilis. The leaf eluant of D. lablab was toxic to nematodes but the root eluant was not. Thus, different parts of a botanical contain different active ingredients or different concentrations of the same active ingredient. The numbers of root-knot nematode eggs that hatched in root exudates of M. pruriens and C. spectabilis were significantly lower (20% and 26%) than in distilled water, tomato and P. vulgaris root exudates (83%, 72% and 89%) respectively. Tomato lacks nematotoxic compounds found in M. pruriens and C. spectabilis. Three months after inoculating plants with 1,000 root-knot nematode juveniles the populations in pots with M. pruriens, C. spectabilis and C. retusa had been reduced by approximately 79%, 85% and 86% respectively; compared with an increase of 262% nematodes in pots with Phaseolus vulgaris. There was significant reduction of 90% nematodes in fallow pots with no growing plant. The results from this study demonstrate that some leguminous species contain compounds that either kill root-knot nematodes or interfere with hatching and affect their capacity to invade and develop within their roots. M. pruriens, C. spectabilis and C. retusa could be used with effect to decrease a mixed field populations of root-knot nematodes. PMID:22736854

Expressed proteins of Herbaspirillum seropedicae in maize (DKB240) roots-bacteria interaction revealed using proteomics.

PubMed

Ferrari, Cibele Santos; Amaral, Fernanda Plucani; Bueno, Jessica Cavalheiro Ferreira; Scariot, Mirella Christine; Valentim-Neto, Pedro Alexandre; Arisi, Ana Carolina Maisonnave

2014-11-01

Several molecular tools have been used to clarify the basis of plant-bacteria interaction; however, the mechanism behind the association is still unclear. In this study, we used a proteomic approach to investigate the root proteome of Zea mays (cv. DKB240) inoculated with Herbaspirillum seropedicae strain SmR1 grown in vitro and harvested 7 days after inoculation. Eighteen differentially accumulated proteins were observed in root samples, ten of which were identified by MALDI-TOF mass spectrometry peptide mass fingerprint. Among the identified proteins, we observed three proteins present exclusively in inoculated root samples and six upregulated proteins and one downregulated protein relative to control. Differentially expressed maize proteins were identified as hypothetical protein ZEAMMB73_483204, hypothetical protein ZEAMMB73_269466, and tubulin beta-7 chain. The following were identified as H. seropedicae proteins: peroxiredoxin protein, EF-Tu elongation factor protein, cation transport ATPase, NADPH:quinone oxidoreductase, dinitrogenase reductase, and type III secretion ATP synthase. Our results presented the first evidence of type III secretion ATP synthase expression during H. seropedicae-maize root interaction.

Reactive oxygen species triggering systemic programmed cell death process via elevation of nuclear calcium ion level in tomatoes resisting tobacco mosaic virus.

PubMed

Li, Yang; Li, Qi; Hong, Qiang; Lin, Yichun; Mao, Wang; Zhou, Shumin

2018-05-01

Programmed cell death (PCD) plays a positive role in the systemic response of plants to pathogen resistance. It has been confirmed that local tobacco mosaic virus (TMV) infecting tomato leaves can induce systemic PCD process in root-tip tissues. But up to now the underlying physiological mechanisms are poorly understood. This study focused on the detailed investigation of the physiological responses of root-tip cells during the initiation of systemic PCD. Physiological, biochemical examination and cytological observation showed that 1 day post-inoculation (dpi) of TMV inoculation there was an increase in calcium fluorescence intensity in root tip tissue cells. Then at 2 dpi, 4 dpi, 8 dpi and 15 dpi, the fluorescence intensity of calcium ion continued to increase. However, at 5 dpi, the reactive oxygen species (ROS) began to accumulate in the root-tip cells. And finally at 20 dpi, the obvious PCD reaction was detected. In addition, the experimental results also showed that the above process involved the elevation of two types of intracellular Ca 2+ , including cytoplasmic calcium ([Ca 2+ ] cyt ) and nuclear calcium ([Ca 2+ ] nuc ). The [Ca 2+ ] cyt , as a pilot signal could lead to the subsequent elevation of intracellular ROS concentration. Then, the high levels of ROS stimulated an increase of [Ca 2+ ] nuc and eventually caused PCD reactions in the root-tip tissues. In particular, the high level of nuclear calcium is an essential mediator in systemic PCD of plants. Copyright © 2018 Elsevier B.V. All rights reserved.

Endophytic Bacteria Improve Plant Growth, Symbiotic Performance of Chickpea (Cicer arietinum L.) and Induce Suppression of Root Rot Caused by Fusarium solani under Salt Stress.

PubMed

Egamberdieva, Dilfuza; Wirth, Stephan J; Shurigin, Vyacheslav V; Hashem, Abeer; Abd Allah, Elsayed F

2017-01-01

Salinity causes disturbance in symbiotic performance of plants, and increases susceptibility of plants to soil-borne pathogens. Endophytic bacteria are an essential determinant of cross-tolerance to biotic and abiotic stresses in plants. The aim of this study was to isolate non-rhizobial endophytic bacteria from the root nodules of chickpea ( Cicer arietinum L.), and to assess their ability to improve plant growth and symbiotic performance, and to control root rot in chickpea under saline soil conditions. A total of 40 bacterial isolates from internal root tissues of chickpea grown in salinated soil were isolated. Four bacterial isolates, namely Bacillus cereus NUU1 , Achromobacter xylosoxidans NUU2, Bacillus thuringiensis NUU3, and Bacillus subtilis NUU4 colonizing root tissue demonstrated plant beneficial traits and/or antagonistic activity against F. solani and thus were characterized in more detail. The strain B. subtilis NUU4 proved significant plant growth promotion capabilities, improved symbiotic performance of host plant with rhizobia, and promoted yield under saline soil as compared to untreated control plants under field conditions. A combined inoculation of chickpea with M. ciceri IC53 and B. subtilis NUU4 decreased H 2 O 2 concentrations and increased proline contents compared to the un-inoculated plants indicating an alleviation of adverse effects of salt stress. Furthermore, the bacterial isolate was capable to reduce the infection rate of root rot in chickpea caused by F. solani . This is the first report of F. solani causing root rot of chickpea in a salinated soil of Uzbekistan. Our findings demonstrated that the endophytic B. subtilis strain NUU4 provides high potentials as a stimulator for plant growth and as biological control agent of chickpea root rot under saline soil conditions. These multiple relationships could provide promising practical approaches to increase the productivity of legumes under salt stress.

Endophytic Bacteria Improve Plant Growth, Symbiotic Performance of Chickpea (Cicer arietinum L.) and Induce Suppression of Root Rot Caused by Fusarium solani under Salt Stress

PubMed Central

Egamberdieva, Dilfuza; Wirth, Stephan J.; Shurigin, Vyacheslav V.; Hashem, Abeer; Abd_Allah, Elsayed F.

2017-01-01

Salinity causes disturbance in symbiotic performance of plants, and increases susceptibility of plants to soil-borne pathogens. Endophytic bacteria are an essential determinant of cross-tolerance to biotic and abiotic stresses in plants. The aim of this study was to isolate non–rhizobial endophytic bacteria from the root nodules of chickpea (Cicer arietinum L.), and to assess their ability to improve plant growth and symbiotic performance, and to control root rot in chickpea under saline soil conditions. A total of 40 bacterial isolates from internal root tissues of chickpea grown in salinated soil were isolated. Four bacterial isolates, namely Bacillus cereus NUU1, Achromobacter xylosoxidans NUU2, Bacillus thuringiensis NUU3, and Bacillus subtilis NUU4 colonizing root tissue demonstrated plant beneficial traits and/or antagonistic activity against F. solani and thus were characterized in more detail. The strain B. subtilis NUU4 proved significant plant growth promotion capabilities, improved symbiotic performance of host plant with rhizobia, and promoted yield under saline soil as compared to untreated control plants under field conditions. A combined inoculation of chickpea with M. ciceri IC53 and B. subtilis NUU4 decreased H2O2 concentrations and increased proline contents compared to the un-inoculated plants indicating an alleviation of adverse effects of salt stress. Furthermore, the bacterial isolate was capable to reduce the infection rate of root rot in chickpea caused by F. solani. This is the first report of F. solani causing root rot of chickpea in a salinated soil of Uzbekistan. Our findings demonstrated that the endophytic B. subtilis strain NUU4 provides high potentials as a stimulator for plant growth and as biological control agent of chickpea root rot under saline soil conditions. These multiple relationships could provide promising practical approaches to increase the productivity of legumes under salt stress. PMID:29033922

Comparative response of six grapevine rootstocks to inoculation with arbuscular mycorrhizal fungi based on root traits

NASA Astrophysics Data System (ADS)

Pogiatzis, Antreas; Bowen, Pat; Hart, Miranda; Holland, Taylor; Klironomos, John

2017-04-01

Arbuscular mycorrhizal (AM) symbiosis has been proven to be essential in grapevines, sustaining plant growth especially under abiotic and biotic stressors. The mycorrhizal growth response of young grapevines varies among rootstock cultivars and the underlying mechanisms involved in this variation are unknown. We predicted that this variation in mycorrhizal response may be explained by differences in root traits among rootstocks. We analyzed the entire root system of six greenhouse-grown rootstocks (Salt Creek, 3309 Couderc, Riparia Gloire, 101-14 Millardet et de Grasset, Swarzmann, Teleki 5C), with and without AM fungal inoculation (Rhizophagus irregularis) and characterized their morphological and architectural responses. Twenty weeks after the inoculation, aboveground growth was enhanced by AM colonization. The rootstock varieties were distinctly different in their response to AM fungi, with Salt Creek receiving the highest growth benefit, while Schwarzmann and 5C Teleki receiving the lowest. Plant responsiveness to AM fungi was negatively correlated with branching intensity (fine roots per root length). Furthermore, there was evidence that mycorrhizas can influence the expression of root traits, inducing a higher branching intensity and a lower root to shoot ratio. The results of this study will help to elucidate how interactions between grapevine rootstocks and AM fungi may benefit the establishment of new vineyards.

Endophytic Herbaspirillum seropedicae expresses nif genes in gramineous plants.

PubMed

Roncato-Maccari, Lauren D B; Ramos, Humberto J O; Pedrosa, Fabio O; Alquini, Yedo; Chubatsu, Leda S; Yates, Marshall G; Rigo, Liu U; Steffens, Maria Berenice R; Souza, Emanuel M

2003-07-01

Abstract The interactions between maize, sorghum, wheat and rice plants and Herbaspirillum seropedicae were examined microscopically following inoculation with the H. seropedicae LR15 strain, a Nif(+) (Pnif::gusA) mutant obtained by the insertion of a gusA-kanamycin cassette into the nifH gene of the H. seropedicae wild-type strain. The expression of the Pnif::gusA fusion was followed during the association of the diazotroph with the gramineous species. Histochemical analysis of seedlings of maize, sorghum, wheat and rice grown in vermiculite showed that strain LR15 colonized root surfaces and inner tissues. In early steps of the endophytic association, H. seropedicae colonized root exudation sites, such as axils of secondary roots and intercellular spaces of the root cortex; it then occupied the vascular tissue and there expressed nif genes. The expression of nif genes occurred in roots, stems and leaves as detected by the GUS reporter system. The expression of nif genes was also observed in bacterial colonies located in the external mucilaginous root material, 8 days after inoculation. Moreover, the colonization of plant tissue by H. seropedicae did not depend on the nitrogen-fixing ability, since similar numbers of cells were isolated from roots or shoots of the plants inoculated with Nif(+) or Nif(-) strains.

Inoculation with Bacillus subtilis and Azospirillum brasilense produces abscisic acid that reduces IRT1-mediated cadmium uptake of roots.

PubMed

Xu, Qianru; Pan, Wei; Zhang, Ranran; Lu, Qi; Xue, Wanlei; Wu, Cainan; Song, Bixiu; Du, Shaoting

2018-05-08

Cadmium (Cd) contamination of agricultural soils represents a serious risk to crop safety. A new strategy using abscisic acid (ABA)-generating bacteria, Bacillus subtilis or Azospirillum brasilense, was developed to reduce the Cd accumulation in plants grown in Cd-contaminated soil. Inoculation with either bacterium resulted in a pronounced increase in the ABA level in wild-type Arabidopsis Col-0 plants, accompanied by a decrease in Cd levels in plant tissues, which mitigated the Cd toxicity. As a consequence, the growth of plants exposed to Cd was improved. Nevertheless, B. subtilis and A. brasilense inoculation had little effect on Cd levels and toxicity in the ABA-insensitive mutant snrk 2.2/2.3, indicating that the action of ABA is required for these bacteria to reduce Cd accumulation in plants. Furthermore, inoculation with either B. subtilis or A. brasilense down-regulated the expression of IRT1 (IRON-REGULATED TRANSPORTER 1) in the roots of wild-type plants and had little effect on Cd levels in the IRT1-knockout mutants irt1-1 and irt1-2. In summary, we conclude that B. subtilis and A. brasilense can reduce Cd levels in plants via an IRT1-dependent ABA-mediated mechanism.

Effects of different soil remediation methods on inhibition of lead absorption and growth and quality of Dianthus superbus L.

PubMed

Yang, Xiaoyu; Ma, Siyue; Li, Jianheng

2017-12-01

Heavy metal pollution in soil poses a serious threat to the growth of plants used in traditional Chinese medicine. Therefore, a pot experiment was conducted to study the effects of various soil remediation methods on the performance of Herba Dianthi (Dianthus superbus L.) grown on Pb-contaminated soil. The results show that inoculation of Herba Dianthi with arbuscular mycorrhizal fungi (AMF) led to a significant reduction in Pb uptake (P< 0.05), and increased root development and root-to-shoot ratio compared to untreated control plants, along with the highest content of active components. When planting with Trifolium repens, the reduction effect of Pb absorption was insignificant. Herba Dianthi showed improved growth and active ingredients, and the lowest Pb content, with AMF inoculation. The addition of EDTA decreased the growth of Herba Dianthi, but promoted the absorption of Pb. The inhibition of tumor cells was highest in E2. In conclusion, inoculation with AMF can ensure that plant lead content meets testing standards, helping to improve the quality of medicinal herbs.

Accumulation of New Polypeptides in Ri T-DNA-Transformed Roots of Tomato (Lycopersicon esculentum) during the Development of Vesicular-Arbuscular Mycorrhizae.

PubMed

Simoneau, P; Louisy-Louis, N; Plenchette, C; Strullu, D G

1994-06-01

Root-inducing transferred-DNA (Ri T-DNA)-transformed roots of tomato (Lycopersicon esculentum) were in vitro inoculated with surface-sterilized vesicular-arbuscular mycorrhizal leek root pieces. About 1 week after inoculation, the infection of the transformed root culture by the fungal endophyte was confirmed by photonic microscopy. Total proteins were extracted from the mycorrhizal roots and analyzed by two-dimensional polyacrylamide gel electrophoresis. Control gels were run with proteins extracted from noninoculated roots mixed with purified intraradical vesicles and extraradical hyphae. Comparison of the resulting patterns revealed the presence of two polypeptides with estimated apparent masses of 24 and 39 kDa that were detected only in infected roots. Polypeptides with similar migration parameters were not detected in roots challenged with spore extracts, suggesting that the accumulation of the polypeptides was directly linked to root colonization by the fungus rather than to induction by fungus-derived elicitors.

Accumulation of New Polypeptides in Ri T-DNA-Transformed Roots of Tomato (Lycopersicon esculentum) during the Development of Vesicular-Arbuscular Mycorrhizae

PubMed Central

Simoneau, Philippe; Louisy-Louis, Nathalie; Plenchette, Christian; Strullu, Désiré Georges

1994-01-01

Root-inducing transferred-DNA (Ri T-DNA)-transformed roots of tomato (Lycopersicon esculentum) were in vitro inoculated with surface-sterilized vesicular-arbuscular mycorrhizal leek root pieces. About 1 week after inoculation, the infection of the transformed root culture by the fungal endophyte was confirmed by photonic microscopy. Total proteins were extracted from the mycorrhizal roots and analyzed by two-dimensional polyacrylamide gel electrophoresis. Control gels were run with proteins extracted from noninoculated roots mixed with purified intraradical vesicles and extraradical hyphae. Comparison of the resulting patterns revealed the presence of two polypeptides with estimated apparent masses of 24 and 39 kDa that were detected only in infected roots. Polypeptides with similar migration parameters were not detected in roots challenged with spore extracts, suggesting that the accumulation of the polypeptides was directly linked to root colonization by the fungus rather than to induction by fungus-derived elicitors. Images PMID:16349273

Effect of metal-tolerant plant growth-promoting Rhizobium on the performance of pea grown in metal-amended soil.

PubMed

Wani, Parvaze Ahmad; Khan, Md Saghir; Zaidi, Almas

2008-07-01

The nickel- and zinc-tolerant plant growth-promoting (PGP) Rhizobium sp. RP5 was isolated from nodules of pea, grown in metal-contaminated Indian soils. The PGP potentials of strain RP5 was assessed under in vitro conditions. Strain RP5 displayed a high level of tolerance to nickel (350 microg ml(-1)) and zinc (1500 microg ml(-1)) and showed PGP activity under in vitro conditions. The PGP activity of this strain was further assessed with increasing concentrations of nickel and zinc, using pea as a test crop. The bio-inoculant enhanced the dry matter, nodule numbers, root N, shoot N, leghemoglobin, seed yield, and grain protein (GP) by 19%, 23%, 26%, 47%, 112%, 26%, and 8%, respectively, at 290 mg Ni kg(-1) while at 4890 mg Zn kg(-1) soil, it increased the dry matter, nodule numbers, leghemoglobin, seed yield, GP, and root and shoot N by 18%, 23%, 78%, 26%, 7%, 25%, and 42%, respectively, compared to plants grown in soil amended with metal only. The bio-inoculant increased the glutathione reductase activity of roots and nodules by 46% and 65% at 580 mg Ni kg(-1) and 47% and 54% at 9780 mg Zn kg(-1) soil, respectively, compared to uninoculated plants. The inoculated strain decreased the concentration of nickel and zinc in plant organs. The intrinsic abilities of nitrogen fixation, growth promotion, and the ability to reduce the toxicity of nickel and zinc of the tested strain could be of practical importance in augmenting the growth and yield of pea, in nickel- and zinc-polluted soils.

Ectomycorrhizal fungi enhance nitrogen and phosphorus nutrition of Nothofagus dombeyi under drought conditions by regulating assimilative enzyme activities.

PubMed

Alvarez, Maricel; Huygens, Dries; Olivares, Erick; Saavedra, Isabel; Alberdi, Miren; Valenzuela, Eduardo

2009-08-01

Drought stress conditions (DC) reduce plant growth and nutrition, restraining the sustainable reestablishment of Nothofagus dombeyi in temperate south Chilean forest ecosystems. Ectomycorrhizal symbioses have been documented to enhance plant nitrogen (N) and phosphorus (P) uptake under drought, but the regulation of involved assimilative enzymes remains unclear. We studied 1-year-old N. dombeyi (Mirb.) Oerst. plants in association with the ectomycorrhizal fungi Pisolithus tinctorius (Pers.) Coker & Couch. and Descolea antartica Sing. In greenhouse experiments, shoot and root dry weights, mycorrhizal colonization, foliar N and P concentrations, and root enzyme activities [glutamate synthase (glutamine oxoglutarate aminotransferase (GOGAT), EC 1.4.1.13-14), glutamine synthetase (GS, EC 6.3.1.2), glutamate dehydrogenase (GDH, EC 1.4.1.2-4), nitrate reductase (NR, EC 1.6.6.1), and acid phosphomonoesterase (PME, EC 3.1.3.1-2)] were determined as a function of soil-water content. Inoculation of N. dombeyi with P. tinctorius and D. antartica significantly stimulated plant growth and increased plant foliar N and P concentrations, especially under DC. Ectomycorrhizal inoculation increased the activity of all studied enzymes relative to non-mycorrhizal plants under drought. We speculate that GDH is a key enzyme involved in the enhancement of ectomycorrhizal carbon (C) availability by fuelling the tricarboxylic acid (TCA) cycle under conditions of drought-induced carbon deficit. All studied assimilative enzymes of the ectomycorrhizal associations, involved in C, N, and P transfers, are closely interlinked and interdependent. The up-regulation of assimilative enzyme activities by ectomycorrhizal fungal root colonizers acts as a functional mechanism to increase seedling endurance to drought. We insist upon incorporating ectomycorrhizal inoculation in existing Chilean afforestation programs.

Development and activity of Glomus intraradices as affected by co-existence with Glomus claroideum in one root system.

PubMed

Janoušková, Martina; Seddas, Pascale; Mrnka, Libor; van Tuinen, Diederik; Dvořáčková, Anna; Tollot, Marie; Gianinazzi-Pearson, Vivienne; Vosátka, Miroslav; Gollotte, Armelle

2009-08-01

The co-existence of two arbuscular mycorrhizal fungal (AMF) species, Glomus intraradices and Glomus claroideum, in the root systems of plants was investigated in a greenhouse experiment aimed at reconstructing interactions during an early stage of primary succession on a coal-mine spoil bank in Central Europe. Two plant species, Tripleurospermum inodorum and Calamagrostis epigejos, were inoculated either with one or both AMF species. Fungal development, determined by trypan blue and alkaline phosphatase staining as well as by PCR amplification of rRNA genes with species-specific primers, and the expression of five genes with different metabolic functions in the intraradical structures of G. intraradices were followed after 6 and 9 weeks of cultivation. The two AMF closely co-existed in the root systems of both plants possibly through similar colonisation rates and competitivity. Inoculation with the two fungi, however, did not bring any additional benefit to the host plants in comparison with single inoculation; moreover, plant growth depression observed after inoculation with G. claroideum persisted also in mixed inoculation. The expression of all the assayed G. intraradices genes was affected either by host plant or by co-inoculation with G. claroideum. The effects of both factors depended on the time of sampling, which underlines the importance of addressing this topic in time-course studies.

[Influence of the root canal instrumentation size on the disinfection of intracanal microbe by Er:YAG laser].

PubMed

Xu, Xue-song; Zhu, Ya-qin

2015-12-01

To evaluate the influence of different root canal instrumentation size on disinfection of intracanal microbe of dental root canal. 368 extracted human anterior teeth with single straight root were randomly divided into 8 groups of 46 roots in each. They were instrumented with K3 Ni-Ti files as follows: group A1 and group B1(#25/0.06), group A2 and group B2(#30/0.06), group A3 and group B3(#35/0.06), group A4 and group B4(#40/0.06). After being prepared and sterilized by autoclaving, group A was inoculated with Enterococcus faecalis, and group B was inoculated with Candida albicans. All groups were irrigated with Er:YAG laser combination of 3% NaOCl, 17% EDTA and 0.9% saline, and then the numbers of microbe on the surface of root canal walls were counted after the treatment, the absolute reduction of counting colony forming units(CFUs) and the relative residual rate of CFUs in the individual group was determined. The Date was analyzed with GraphPad Prism 5.02 software package by one-way analysis of variance. Levels of disinfection on E.faecalis and C.albicans increased when root canals were enlarged; #40/0.06 showed the best disinfection, #35/0.06 showed a significantly better disinfection than #30/0.06 and #25/0.06. Substantial reduction of microbe was obtained in #35/0.06 and #40/0.06 compared with #25/0.06 and #30/0.06(P<0.05). Within the root canal size of #25/0.06-#40/0.06, under the conditions of Er:YAG laser combination of 3% NaOCl, 17% EDTA and 0.9% saline, it was concluded that the reduction of E.faecalis and C.albicans of the anterior straight root canals could be predicted by increasing the root canal instrumentation size large than #30/0.06.

Cultivar and Metal-Specific Effects of Endophytic Bacteria in Helianthus tuberosus Exposed to Cd and Zn

PubMed Central

Thijs, Sofie; Lobo, Mª Carmen; Weyens, Nele; Pérez-Sanz, Araceli

2017-01-01

Plant growth promoting endophytic bacteria (PGPB) isolated from Brassica napus were inoculated in two cultivars of Helianthus tuberosus (VR and D19) growing on sand supplemented with 0.1 mM Cd or 1 mM Zn. Plant growth, concentrations of metals and thiobarbituric acid (TBA) reactive compounds were determined. Colonization of roots of H. tuberosus D19 by Pseudomonas sp. 262 was evaluated using confocal laser scanning microscopy. Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 significantly enhanced growth of H. tuberosus D19 exposed to Cd or Zn. Pseudomonas sp. 228 significantly increased Cd concentrations in roots. Serratia sp. 246, and Pseudomonas sp. 256 and 228 resulted in significantly decreased contents of TBA reactive compounds in roots of Zn exposed D19 plants. Growth improvement and decrease of metal-induced stress were more pronounced in D19 than in VR. Pseudomonas sp. 262-green fluorescent protein (GFP) colonized the root epidermis/exodermis and also inside root hairs, indicating that an endophytic interaction was established. H. tuberosus D19 inoculated with Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 holds promise for sustainable biomass production in combination with phytoremediation on Cd and Zn contaminated soils. PMID:28934107

Cultivar and Metal-Specific Effects of Endophytic Bacteria in Helianthus tuberosus Exposed to Cd and Zn.

PubMed

Montalbán, Blanca; Thijs, Sofie; Lobo, Mª Carmen; Weyens, Nele; Ameloot, Marcel; Vangronsveld, Jaco; Pérez-Sanz, Araceli

2017-09-21

Plant growth promoting endophytic bacteria (PGPB) isolated from Brassica napus were inoculated in two cultivars of Helianthus tuberosus (VR and D19) growing on sand supplemented with 0.1 mM Cd or 1 mM Zn. Plant growth, concentrations of metals and thiobarbituric acid (TBA) reactive compounds were determined. Colonization of roots of H. tuberosus D19 by Pseudomonas sp. 262 was evaluated using confocal laser scanning microscopy. Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 significantly enhanced growth of H. tuberosus D19 exposed to Cd or Zn. Pseudomonas sp. 228 significantly increased Cd concentrations in roots. Serratia sp. 246, and Pseudomonas sp. 256 and 228 resulted in significantly decreased contents of TBA reactive compounds in roots of Zn exposed D19 plants. Growth improvement and decrease of metal-induced stress were more pronounced in D19 than in VR. Pseudomonas sp. 262 - green fluorescent protein (GFP) colonized the root epidermis/exodermis and also inside root hairs, indicating that an endophytic interaction was established. H. tuberosus D19 inoculated with Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 holds promise for sustainable biomass production in combination with phytoremediation on Cd and Zn contaminated soils.

Effect of short-term aluminum stress and mycorrhizal inoculation on nitric oxide metabolism in Medicago truncatula roots.

PubMed

Sujkowska-Rybkowska, Marzena; Czarnocka, Weronika; Sańko-Sawczenko, Izabela; Witoń, Damian

2018-01-01

Aluminum (Al) toxicity can induce oxidative and nitrosative stress, which limits growth and yield of crop plants. Nevertheless, plant tolerance to stress may be improved by symbiotic associations including arbuscular mycorrhiza (AM). Nitric oxide (NO) is a signaling molecule involved in physiological processes and plant responses to abiotic and biotic stresses. However, almost no information about the NO metabolism has been gathered about AM. In the present work, Medicago truncatula seedlings were inoculated with Rhizophagus irregularis, and 7-week-old plants were treated with 50μM AlCl 3 for 3h. Cytochemical and molecular techniques were used to measure the components of the NO metabolism, including NO content and localization, expression of genes encoding NO-synthesis (MtNR1, MtNR2 and MtNIR1) and NO-scavenging (MtGSNOR1, MtGSNOR2, MtHB1 and MtHB2) enzymes and the profile of protein tyrosine nitration (NO 2 -Tyr) in Medicago roots. For the first time, NO and NO 2 -Tyr accumulation was connected with fungal structures (arbuscules, vesicles and intercellular hyphae). Expression analysis of genes encoding NO-synthesis enzymes indicated that AM symbiosis results in lower production of NO in Al-treated roots in comparison to non-mycorrhizal roots. Elevated levels of transcription of genes encoding NO-scavenging enzymes indicated more active NO scavenging in AMF-inoculated Al-treated roots compared to non-inoculated roots. These results were confirmed by less NO accumulation and lower protein nitration in Al-stressed mycorrhizal roots in comparison to non-mycorrhizal roots. This study provides a new insight in NO metabolism in response to arbuscular mycorrhiza under normal and metal stress conditions. Our results suggest that mycorrhizal fungi decrease NO and tyrosine nitrated proteins content in Al-treated Medicago roots, probably via active NO scavenging system. Copyright © 2017 Elsevier GmbH. All rights reserved.

Quantification and role of organic acids in cucumber root exudates in Trichoderma harzianum T-E5 colonization.

PubMed

Zhang, Fengge; Meng, Xiaohui; Yang, Xingming; Ran, Wei; Shen, Qirong

2014-10-01

The ability to colonize on plant roots is recognized as one of the most important characteristics of the beneficial fungi Trichoderma spp. The aim of this study is to prove that the utilization of organic acids is a major trait of Trichoderma harzianum T-E5 for colonization of cucumber roots. A series experiments in split-root hydroponic system and in vitro were designed to demonstrate the association between the utilization of organic acids and T-E5 colonization on cucumber roots. In the split-root hydroponic system, inoculation with T-E5 (T) significantly increased the biomass of cucumber plants compared with CK (non-inoculation with T-E5). The T-E5 hyphae densely covering the cucumber root surface were observed by scanning electron microscopy (SEM). Three organic acids (oxalic acid, malic acid and citric acid) were identified from both the CK and T treatments by HPLC and LC/ESI-MS procedures. The amounts of oxalic acid and malic acid in T were significantly higher than those in CK. All the organic acids exhibited different and significant stimulation effects on the mycelial growth and conidial germination of T-E5 in vitro. An additional hydroponic experiment demonstrated the positive effects of organic acids on the T-E5 colonization of cucumber roots. In conclusion, the present study revealed that certain organic acids could be used as nutritional sources for Trichoderma harzianum T-E5 to reinforce its population on cucumber roots. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Induction of DIMBOA accumulation and systemic defense responses as a mechanism of enhanced resistance of mycorrhizal corn (Zea mays L.) to sheath blight.

PubMed

Song, Yuan Yuan; Cao, Man; Xie, Li Jun; Liang, Xiao Ting; Zeng, Ren Sen; Su, Yi Juan; Huang, Jing Hua; Wang, Rui Long; Luo, Shi Ming

2011-11-01

Arbuscular mycorrhizas are the most important symbioses in terrestrial ecosystems and they enhance the plant defense against numerous soil-borne pathogenic fungi and nematodes. Two corn (Zea mays) varieties, Gaoyou-115 that is susceptible to sheath blight disease caused by Rhizoctonia solani and Yuenong-9 that is resistant, were used for mycorrhizal inoculation in this study. Pre-inoculation of susceptible Gaoyou-115 with arbuscular mycorrhizal fungus (AMF) Glomus mosseae significantly reduced the disease incidence and disease severity of sheath blight of corn. HPLC analysis showed that AMF inoculation led to significant increase in 2,4-dihydroxy-7-methoxy-2 H-1,4-benzoxazin-3(4 H)-one (DIMBOA) accumulation in the roots of both corn varieties and in leaves of resistant Yuenong-9. R. solani inoculation alone did not result in accumulation of DIMBOA in both roots and leaves of the two corn varieties. Our previous study showed that DIMBOA strongly inhibited mycelial growth of R. solani in vitro. Real-time PCR analysis showed that mycorrhizal inoculation itself did not affect the transcripts of most genes tested. However, pre-inoculation with G. mosseae induced strong responses of three defense-related genes PR2a, PAL, and AOS, as well as BX9, one of the key genes in DIMBOA biosynthesis pathway, in the leaves of corn plants of both Yuenong-9 and Gaoyou-115 after the pathogen attack. Induction of defense responses in pre-inoculated plants was much higher and quicker than that in non-inoculated plants upon R. solani infection. These results indicate that induction of accumulation of DIMBOA, an important phytoalexin in corn, and systemic defense responses by AMF, plays a vital role in enhanced disease resistance of mycorrhizal plants of corn against sheath blight. This study also suggests that priming is an important mechanism in mycorrhiza-induced resistance.

Consequences of pre-inoculation with native arbuscular mycorrhizae on root colonization and survival of Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings after transplanting

Treesearch

Bill Eugene Davidson

2015-01-01

Inoculation of seedlings with arbuscular mycorrhizal fungi (AMF) is a common practice aimed at improving seedling establishment. The success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These events were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush...

Identification of genes differentially expressed in ectomycorrhizal roots during the Pinus pinaster-Laccaria bicolor interaction.

PubMed

Flores-Monterroso, Aranzazu; Canales, Javier; de la Torre, Fernando; Ávila, Concepción; Cánovas, Francisco M

2013-06-01

Ectomycorrhizal associations are of major ecological importance in temperate and boreal forests. The development of a functional ectomycorrhiza requires many genetic and biochemical changes. In this study, suppressive subtraction hybridization was used to identify differentially expressed genes in the roots of maritime pine (Pinus pinaster Aiton) inoculated with Laccaria bicolor, a mycorrhizal fungus. A total number of 200 unigenes were identified as being differentially regulated in maritime pine roots during the development of mycorrhiza. These unigenes were classified into 10 categories according to the function of their homologues in the GenBank database. Approximately, 40 % of the differentially expressed transcripts were genes that coded for unknown proteins in the databases or that had no homology to known genes. A group of these differentially expressed genes was selected to validate the results using quantitative real-time PCR. The transcript levels of the representative genes were compared between the non-inoculated and inoculated plants at 1, 5, 15 and 30 days after inoculation. The observed expression patterns indicate (1) changes in the composition of the wall cell, (2) tight regulation of defence genes during the development of mycorrhiza and (3) changes in carbon and nitrogen metabolism. Ammonium excess or deficiency dramatically affected the stability of ectomycorrhiza and altered gene expression in maritime pine roots.

Azospirillum brasilense ameliorates the response of Arabidopsis thaliana to drought mainly via enhancement of ABA levels.

PubMed

Cohen, Ana C; Bottini, Rubén; Pontin, Mariela; Berli, Federico J; Moreno, Daniela; Boccanlandro, Hernán; Travaglia, Claudia N; Piccoli, Patricia N

2015-01-01

Production of phytohormones is one of the main mechanisms to explain the beneficial effects of plant growth-promoting rhizobacteria (PGPR) such as Azospirillum sp. The PGPRs induce plant growth and development, and reduce stress susceptibility. However, little is known regarding the stress-related phytohormone abscisic acid (ABA) produced by bacteria. We investigated the effects of Azospirillum brasilense Sp 245 strain on Arabidopsis thaliana Col-0 and aba2-1 mutant plants, evaluating the morphophysiological and biochemical responses when watered and in drought. We used an in vitro-grown system to study changes in the root volume and architecture after inoculation with Azospirillum in Arabidopsis wild-type Col-0 and on the mutant aba2-1, during early growth. To examine Arabidopsis development and reproductive success as affected by the bacteria, ABA and drought, a pot experiment using Arabidopsis Col-0 plants was also carried out. Azospirillum brasilense augmented plant biomass, altered root architecture by increasing lateral roots number, stimulated photosynthetic and photoprotective pigments and retarded water loss in correlation with incremented ABA levels. As well, inoculation improved plants seed yield, plants survival, proline levels and relative leaf water content; it also decreased stomatal conductance, malondialdehyde and relative soil water content in plants submitted to drought. Arabidopsis inoculation with A. brasilense improved plants performance, especially in drought. © 2014 Scandinavian Plant Physiology Society.

Friend or Foe-Light Availability Determines the Relationship between Mycorrhizal Fungi, Rhizobia and Lima Bean (Phaseolus lunatus L.).

PubMed

Ballhorn, Daniel J; Schädler, Martin; Elias, Jacob D; Millar, Jess A; Kautz, Stefanie

2016-01-01

Plant associations with root microbes represent some of the most important symbioses on earth. While often critically promoting plant fitness, nitrogen-fixing rhizobia and arbuscular mycorrhizal fungi (AMF) also demand significant carbohydrate allocation in exchange for key nutrients. Though plants may often compensate for carbon loss, constraints may arise under light limitation when plants cannot extensively increase photosynthesis. Under such conditions, costs for maintaining symbioses may outweigh benefits, turning mutualist microbes into parasites, resulting in reduced plant growth and reproduction. In natural systems plants commonly grow with different symbionts simultaneously which again may interact with each other. This might add complexity to the responses of such multipartite relationships. We experimented with lima bean (Phaseolus lunatus), which efficiently forms associations with both types of root symbionts. We applied full light and low-light to each of four treatments of microbial inoculation. After an incubation period of 14 weeks, we quantified vegetative aboveground and belowground biomass and number and viability of seeds to determine effects of combined inoculant and light treatment on plant fitness. Under light-limited conditions, vegetative and reproductive traits were inhibited in AMF and rhizobia inoculated lima bean plants relative to controls (un-colonized plants). Strikingly, reductions in seed production were most critical in combined treatments with rhizobia x AMF. Our findings suggest microbial root symbionts create additive costs resulting in decreased plant fitness under light-limited conditions.

Symbiotic performance and induction of systemic resistance against Cercospora sojina in soybean plants co-inoculated with Bacillus sp. CHEP5 and Bradyrhizobium japonicum E109.

PubMed

Tonelli, María Laura; Magallanes-Noguera, C; Fabra, A

2017-11-01

Soybean is an economically very important crop throughout the word and particularly in Argentina. Soybean yield may be affected by many factors such as the lack of some essential nutrients or pathogens attack. In this work we demonstrated that the co-inoculation of the native biocontrol bacterium Bacillus sp. CHEP5 which induces resistance against Cercospora sojina in soybean and the nitrogen fixing strain Bradyrhizobium japonicum E109, was more effective in reducing frog leaf spot severity than the inoculation of the biocontrol agent alone. Probably, this is related with the increase in the ability to form biofilm when both bacteria are growing together. Furthermore, Bacillus sp. CHEP5 inoculation did not affect Bradyrhizobium japonicum E109 symbiotic behavior and flavonoids composition of root exudates in pathogen challenged plants. These results suggest that co-inoculation of plants with rhizobia and biocontrol agents could be a strategy to improve soybean production in a sustainable system.

Physiological, structural and molecular traits activated in strawberry plants after inoculation with the plant growth-promoting bacterium Azospirillum brasilense REC3.

PubMed

Guerrero-Molina, M F; Lovaisa, N C; Salazar, S M; Martínez-Zamora, M G; Díaz-Ricci, J C; Pedraza, R O

2015-05-01

The plant growth-promoting strain REC3 of Azospirillum brasilense, isolated from strawberry roots, prompts growth promotion and systemic protection against anthracnose disease in this crop. Hence, we hypothesised that A. brasilense REC3 can induce different physiological, structural and molecular responses in strawberry plants. Therefore, the aim of this work was to study these traits activated in Azospirillum-colonised strawberry plants, which have not been assessed until now. Healthy, in vitro micropropagated plants were root-inoculated with REC3 under hydroponic conditions; root and leaf tissues were sampled at different times, and oxidative burst, phenolic compound content, malondialdehyde (MDA) concentration, callose deposition, cell wall fortification and gene expression were evaluated. Azospirillum inoculation enhanced levels of soluble phenolic compounds after 12 h post-inoculation (hpi), while amounts of cell wall bound phenolics were similar in inoculated and control plants. Other early responses activated by REC3 (at 24 hpi) were a decline of lipid peroxidation and up-regulation of strawberry genes involved in defence (FaPR1), bacterial recognition (FaFLS2) and H₂O₂ depuration (FaCAT and FaAPXc). The last may explain the apparent absence of oxidative burst in leaves after bacterial inoculation. Also, REC3 inoculation induced delayed structural responses such as callose deposition and cell wall fortification (at 72 hpi). Results showed that A. brasilense REC3 is capable of exerting beneficial effects on strawberry plants, reinforcing their physiological and cellular characteristics, which in turns contribute to improve plant performance. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Rooting and acclimatization of micropropagated marubakaido apple rootstock using Adesmia latifolia rhizobia.

PubMed

Muniz, Aleksander Westphal; de Sá, Enilson Luiz; Dalagnol, Gilberto Luíz; Filho, João Américo

2013-01-01

In vitro rooting and the acclimatization of micropropagated rootstocks of apple trees is essential for plant development in the field. The aim of this work was to assess the use of rhizobia of Adesmia latifolia to promote rooting and acclimatization in micropropagated Marubakaido apple rootstock. An experiment involving in vitro rooting and acclimatization was performed with four strains of rhizobium and two controls, one with and the other without the addition of synthetic indoleacetic acid. The inoculated treatments involved the use of sterile inoculum and inoculum containing live rhizobia. The most significant effects on the rooting rate, primary-root length, number of roots, root length, fresh-shoot biomass, and fresh-root biomass were obtained by inoculation with strain EEL16010B and with synthetic indole acetic acid. However, there was no difference in the growth of apple explants in the acclimatization experiments. Strain EEL16010B can be used to induce in vitro rooting of the Marubakaido rootstock and can replace the use of synthetic indoleacetic acid in the rooting of this cultivar.

Effect of microbial-based inoculants on nutrient concentrations and early root morphology of corn (Zea mays)

USDA-ARS?s Scientific Manuscript database

Microbial-based inoculants have been reported to stimulate plant growth and nutrient uptake. However, their effect may vary depending on the growth stage when evaluated and on the chemical fertilizer applied. Thus, the objective of this study was to test the hypothesis that microbial-based inoculant...

Root inoculation with Pseudomonas putida KT2440 induces transcriptional and metabolic changes and systemic resistance in maize plants.

PubMed

Planchamp, Chantal; Glauser, Gaetan; Mauch-Mani, Brigitte

2014-01-01

Pseudomonas putida KT2440 (KT2440) rhizobacteria colonize a wide range of plants. They have been extensively studied for their capacity to adhere to maize seeds, to tolerate toxic secondary metabolites produced by maize roots and to be attracted by maize roots. However, the response of maize plants to KT2440 colonization has not been investigated yet. Maize roots were inoculated with KT2440 and the local (roots) and systemic (leaves) early plant responses were investigated. The colonization behavior of KT2440 following application to maize seedlings was investigated and transcriptional analysis of stress- and defense-related genes as well as metabolite profiling of local and systemic maize tissues of KT2440-inoculated were performed. The local and systemic responses differed and more pronounced changes were observed in roots compared to leaves. Early in the interaction roots responded via jasmonic acid- and abscisic acid-dependent signaling. Interestingly, during later steps, the salicylic acid pathway was suppressed. Metabolite profiling revealed the importance of plant phospholipids in KT2440-maize interactions. An additional important maize secondary metabolite, a form of benzoxazinone, was also found to be differently abundant in roots 3 days after KT2440 inoculation. However, the transcriptional and metabolic changes observed in bacterized plants early during the interaction were minor and became even less pronounced with time, indicating an accommodation state of the plant to the presence of KT2440. Since the maize plants reacted to the presence of KT2440 in the rhizosphere, we also investigated the ability of these bacteria to trigger induced systemic resistance (ISR) against the maize anthracnose fungus Colletotrichum graminicola. The observed resistance was expressed as strongly reduced leaf necrosis and fungal growth in infected bacterized plants compared to non-bacterized controls, showing the potential of KT2440 to act as resistance inducers.

Root inoculation with Pseudomonas putida KT2440 induces transcriptional and metabolic changes and systemic resistance in maize plants

PubMed Central

Planchamp, Chantal; Glauser, Gaetan; Mauch-Mani, Brigitte

2014-01-01

Pseudomonas putida KT2440 (KT2440) rhizobacteria colonize a wide range of plants. They have been extensively studied for their capacity to adhere to maize seeds, to tolerate toxic secondary metabolites produced by maize roots and to be attracted by maize roots. However, the response of maize plants to KT2440 colonization has not been investigated yet. Maize roots were inoculated with KT2440 and the local (roots) and systemic (leaves) early plant responses were investigated. The colonization behavior of KT2440 following application to maize seedlings was investigated and transcriptional analysis of stress- and defense-related genes as well as metabolite profiling of local and systemic maize tissues of KT2440-inoculated were performed. The local and systemic responses differed and more pronounced changes were observed in roots compared to leaves. Early in the interaction roots responded via jasmonic acid- and abscisic acid-dependent signaling. Interestingly, during later steps, the salicylic acid pathway was suppressed. Metabolite profiling revealed the importance of plant phospholipids in KT2440-maize interactions. An additional important maize secondary metabolite, a form of benzoxazinone, was also found to be differently abundant in roots 3 days after KT2440 inoculation. However, the transcriptional and metabolic changes observed in bacterized plants early during the interaction were minor and became even less pronounced with time, indicating an accommodation state of the plant to the presence of KT2440. Since the maize plants reacted to the presence of KT2440 in the rhizosphere, we also investigated the ability of these bacteria to trigger induced systemic resistance (ISR) against the maize anthracnose fungus Colletotrichum graminicola. The observed resistance was expressed as strongly reduced leaf necrosis and fungal growth in infected bacterized plants compared to non-bacterized controls, showing the potential of KT2440 to act as resistance inducers. PMID:25628626

Drought delays development of the sorghum root microbiome and enriches for monoderm bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Ling; Naylor, Dan; Dong, Zhaobin

Here, drought stress is a major obstacle to crop productivity, and the severity and frequency of drought are expected to increase in the coming century. Certain root-associated bacteria have been shown to mitigate the negative effects of drought stress on plant growth, and manipulation of the crop microbiome is an emerging strategy for overcoming drought stress in agricultural systems, yet the effect of drought on the development of the root microbiome is poorly understood. Through 16S rRNA amplicon and metatranscriptome sequencing, as well as root metabolomics, we demonstrate that drought delays the development of the early sorghum root microbiome andmore » causes increased abundance and activity of monoderm bacteria, which lack an outer cell membrane and contain thick cell walls. Our data suggest that altered plant metabolism and increased activity of bacterial ATP-binding cassette (ABC) transporter genes are correlated with these shifts in community composition. Finally, inoculation experiments with monoderm isolates indicate that increased colonization of the root during drought can positively impact plant growth. Collectively, these results demonstrate the role that drought plays in restructuring the root microbiome and highlight the importance of temporal sampling when studying plant-associated microbiomes.« less

Drought delays development of the sorghum root microbiome and enriches for monoderm bacteria.

PubMed

Xu, Ling; Naylor, Dan; Dong, Zhaobin; Simmons, Tuesday; Pierroz, Grady; Hixson, Kim K; Kim, Young-Mo; Zink, Erika M; Engbrecht, Kristin M; Wang, Yi; Gao, Cheng; DeGraaf, Stephanie; Madera, Mary A; Sievert, Julie A; Hollingsworth, Joy; Birdseye, Devon; Scheller, Henrik V; Hutmacher, Robert; Dahlberg, Jeffery; Jansson, Christer; Taylor, John W; Lemaux, Peggy G; Coleman-Derr, Devin

2018-05-01

Drought stress is a major obstacle to crop productivity, and the severity and frequency of drought are expected to increase in the coming century. Certain root-associated bacteria have been shown to mitigate the negative effects of drought stress on plant growth, and manipulation of the crop microbiome is an emerging strategy for overcoming drought stress in agricultural systems, yet the effect of drought on the development of the root microbiome is poorly understood. Through 16S rRNA amplicon and metatranscriptome sequencing, as well as root metabolomics, we demonstrate that drought delays the development of the early sorghum root microbiome and causes increased abundance and activity of monoderm bacteria, which lack an outer cell membrane and contain thick cell walls. Our data suggest that altered plant metabolism and increased activity of bacterial ATP-binding cassette (ABC) transporter genes are correlated with these shifts in community composition. Finally, inoculation experiments with monoderm isolates indicate that increased colonization of the root during drought can positively impact plant growth. Collectively, these results demonstrate the role that drought plays in restructuring the root microbiome and highlight the importance of temporal sampling when studying plant-associated microbiomes. Copyright © 2018 the Author(s). Published by PNAS.

Drought delays development of the sorghum root microbiome and enriches for monoderm bacteria

DOE PAGES

Xu, Ling; Naylor, Dan; Dong, Zhaobin; ...

2018-04-16

Here, drought stress is a major obstacle to crop productivity, and the severity and frequency of drought are expected to increase in the coming century. Certain root-associated bacteria have been shown to mitigate the negative effects of drought stress on plant growth, and manipulation of the crop microbiome is an emerging strategy for overcoming drought stress in agricultural systems, yet the effect of drought on the development of the root microbiome is poorly understood. Through 16S rRNA amplicon and metatranscriptome sequencing, as well as root metabolomics, we demonstrate that drought delays the development of the early sorghum root microbiome andmore » causes increased abundance and activity of monoderm bacteria, which lack an outer cell membrane and contain thick cell walls. Our data suggest that altered plant metabolism and increased activity of bacterial ATP-binding cassette (ABC) transporter genes are correlated with these shifts in community composition. Finally, inoculation experiments with monoderm isolates indicate that increased colonization of the root during drought can positively impact plant growth. Collectively, these results demonstrate the role that drought plays in restructuring the root microbiome and highlight the importance of temporal sampling when studying plant-associated microbiomes.« less

Ecological distribution of Spirillum lipoferum Beijerinck.

PubMed

Dobereiner, J; Marriel, I E; Nery, M

1976-10-01

A survey in various countries revealed that the N2-fixing Spirillum lipoferum Beijerinck is a very common root and soil inhabitant in the tropics. More than half of the grass root and soil samples collected in tropical countries (four African countries and Brazil) contained abundant S. lipoferum populations, while less than 10% of the samples collected in temperate South Brazil, Kenya, and the U.S.A. contained the organism. There is a pronounced vegetation effect. Panicum maximum seems the most favorable among the forage grasses, while few positive samples were found under virgin tropical forest. Legume roots contained less S. lipoferum than adjacent soils. More than 80% of the samples from cereal roots (maize, sorghum, wheat, and rye) grown in fields fertilized with PK and Mo, in Rio de Janeiro State, were positive. Maize and sorghum grown under similar conditions in Wisconsin contained less than 10% of positive samples, but when maize fields were inoculated 90% of the root samples contained S. lipoferum. Alluvial soils were more favorable than eroded hill soils. Occurrence in soil was strongly pH-dependent with a pH around 7, being optimal (correlation coefficient r = 0.90). Sporadic occurrence was observed even in soils with pH 4.8. Surface-sterilized P. maximum roots collected from soils with pH ranging from 4.8 to 7.2 contained high S. lipoferum numbers which did not correlate with soil pH (r = 0.41). Amendment with malate of acid soils was not very effective in increasing nitrogenase (N2-ase) activity, but in two soils with pH above 6.4, high N2-ase activity was obtained after 16 to 48 h of incubation. In two soils from a temperate climate region, inoculation with S. lipoferum increased N2-ase activity produced through malate amendment.

A Community-Based Culture Collection for Targeting Novel Plant Growth-Promoting Bacteria from the Sugarcane Microbiome

PubMed Central

Armanhi, Jaderson Silveira Leite; de Souza, Rafael Soares Correa; Damasceno, Natália de Brito; de Araújo, Laura M.; Imperial, Juan; Arruda, Paulo

2018-01-01

The soil-plant ecosystem harbors an immense microbial diversity that challenges investigative approaches to study traits underlying plant-microbe association. Studies solely based on culture-dependent techniques have overlooked most microbial diversity. Here we describe the concomitant use of culture-dependent and -independent techniques to target plant-beneficial microbial groups from the sugarcane microbiome. The community-based culture collection (CBC) approach was used to access microbes from roots and stalks. The CBC recovered 399 unique bacteria representing 15.9% of the rhizosphere core microbiome and 61.6–65.3% of the endophytic core microbiomes of stalks. By cross-referencing the CBC (culture-dependent) with the sugarcane microbiome profile (culture-independent), we designed a synthetic community comprised of naturally occurring highly abundant bacterial groups from roots and stalks, most of which has been poorly explored so far. We then used maize as a model to probe the abundance-based synthetic inoculant. We show that when inoculated in maize plants, members of the synthetic community efficiently colonize plant organs, displace the natural microbiota and dominate at 53.9% of the rhizosphere microbial abundance. As a result, inoculated plants increased biomass by 3.4-fold as compared to uninoculated plants. The results demonstrate that abundance-based synthetic inoculants can be successfully applied to recover beneficial plant microbes from plant microbiota. PMID:29354144

Effect of arbuscular mycorrhizal and bacterial inocula on nitrate concentration in mesocosms simulating a wastewater treatment system relying on phytodepuration.

PubMed

Lingua, Guido; Copetta, Andrea; Musso, Davide; Aimo, Stefania; Ranzenigo, Angelo; Buico, Alessandra; Gianotti, Valentina; Osella, Domenico; Berta, Graziella

2015-12-01

High nitrogen concentration in wastewaters requires treatments to prevent the risks of eutrophication in rivers, lakes and coastal waters. The use of constructed wetlands is one of the possible approaches to lower nitrate concentration in wastewaters. Beyond supporting the growth of the bacteria operating denitrification, plants can directly take up nitrogen. Since plant roots interact with a number of soil microorganisms, in the present work we report the monitoring of nitrate concentration in macrocosms with four different levels of added nitrate (0, 30, 60 and 90 mg l(-1)), using Phragmites australis, inoculated with bacteria or arbuscular mycorrhizal fungi, to assess whether the use of such inocula could improve wastewater denitrification. Higher potassium nitrate concentration increased plant growth and inoculation with arbuscular mycorrhizal fungi or bacteria resulted in larger plants with more developed root systems. In the case of plants inoculated with arbuscular mycorrhizal fungi, a faster decrease of nitrate concentration was observed, while the N%/C% ratio of the plants of the different treatments remained similar. At 90 mg l(-1) of added nitrate, only mycorrhizal plants were able to decrease nitrate concentration to the limits prescribed by the Italian law. These data suggest that mycorrhizal and microbial inoculation can be an additional tool to improve the efficiency of denitrification in the treatment of wastewaters via constructed wetlands.

The Pattern of Secreted Molecules During the Co-Inoculation of Alfalfa Plants With Sinorhizobium meliloti and Delftia sp. strain JD2: An Interaction That Improves Plant Yield.

PubMed

Morel, M A; Cagide, C; Minteguiaga, M A; Dardanelli, M S; Castro-Sowinski, S

2015-02-01

Delftia sp. strain JD2 is a plant-growth-promoting bacterium that enhances legume nodulation and growth, acting as nodule-assisting bacterium during the co-inoculation of plants with rhizobial strains. In this work, we evaluate how the co-inoculation of alfalfa with Sinorhizobium meliloti U143 and JD2 increases plant yield under greenhouse conditions and we analyze the pattern of secreted bioactive compounds which may be involved in the microbe-plant communication. The chemical composition of extracellular cultures (EC) produced in hydroponic conditions (collected 4, 7, and 14 days after bacterial treatment) were characterized using different chromatographic and elucidation techniques. In addition, we assessed the effect that plant irrigation with cell-free EC, produced during co-inoculation experiments, would have on plant yield. Results showed increased alfalfa shoot and root matter, suggesting that U143-JD2 co-inoculation might be a beneficial agricultural practice. The pattern of secreted secondary metabolites among treatments showed important differences. Qualitative and quantitative changes in phenolic compounds (including flavonoids), organic acids, and volatile compounds were detected during the early microbe-plant interaction, suggesting that the production of some molecules positively affects the microbe-plant association. Finally, the irrigation of co-inoculated plants with cell-free EC under greenhouse conditions increased plant yield over agronomic expectations. This effect might be attributed to the bioactive secondary metabolites incorporated during the irrigation.

The role of plant-associated bacteria in the mobilization and phytoextraction of trace elements in contaminated soils

PubMed Central

Sessitsch, Angela; Kuffner, Melanie; Kidd, Petra; Vangronsveld, Jaco; Wenzel, Walter W.; Fallmann, Katharina; Puschenreiter, Markus

2013-01-01

Phytoextraction makes use of trace element-accumulating plants that concentrate the pollutants in their tissues. Pollutants can be then removed by harvesting plants. The success of phytoextraction depends on trace element availability to the roots and the ability of the plant to intercept, take up, and accumulate trace elements in shoots. Current phytoextraction practises either employ hyperaccumulators or fast-growing high biomass plants; the phytoextraction process may be enhanced by soil amendments that increase trace element availability in the soil. This review will focus on the role of plant-associated bacteria to enhance trace element availability in the rhizosphere. We report on the kind of bacteria typically found in association with trace element – tolerating or – accumulating plants and discuss how they can contribute to improve trace element uptake by plants and thus the efficiency and rate of phytoextraction. This enhanced trace element uptake can be attributed to a microbial modification of the absorptive properties of the roots such as increasing the root length and surface area and numbers of root hairs, or by increasing the plant availability of trace elements in the rhizosphere and the subsequent translocation to shoots via beneficial effects on plant growth, trace element complexation and alleviation of phytotoxicity. An analysis of data from literature shows that effects of bacterial inoculation on phytoextraction efficiency are currently inconsistent. Some key processes in plant–bacteria interactions and colonization by inoculated strains still need to be unravelled more in detail to allow full-scale application of bacteria assisted phytoremediation of trace element contaminated soils. PMID:23645938

The role of plant-associated bacteria in the mobilization and phytoextraction of trace elements in contaminated soils.

PubMed

Sessitsch, Angela; Kuffner, Melanie; Kidd, Petra; Vangronsveld, Jaco; Wenzel, Walter W; Fallmann, Katharina; Puschenreiter, Markus

2013-05-01

Phytoextraction makes use of trace element-accumulating plants that concentrate the pollutants in their tissues. Pollutants can be then removed by harvesting plants. The success of phytoextraction depends on trace element availability to the roots and the ability of the plant to intercept, take up, and accumulate trace elements in shoots. Current phytoextraction practises either employ hyperaccumulators or fast-growing high biomass plants; the phytoextraction process may be enhanced by soil amendments that increase trace element availability in the soil. This review will focus on the role of plant-associated bacteria to enhance trace element availability in the rhizosphere. We report on the kind of bacteria typically found in association with trace element - tolerating or - accumulating plants and discuss how they can contribute to improve trace element uptake by plants and thus the efficiency and rate of phytoextraction. This enhanced trace element uptake can be attributed to a microbial modification of the absorptive properties of the roots such as increasing the root length and surface area and numbers of root hairs, or by increasing the plant availability of trace elements in the rhizosphere and the subsequent translocation to shoots via beneficial effects on plant growth, trace element complexation and alleviation of phytotoxicity. An analysis of data from literature shows that effects of bacterial inoculation on phytoextraction efficiency are currently inconsistent. Some key processes in plant-bacteria interactions and colonization by inoculated strains still need to be unravelled more in detail to allow full-scale application of bacteria assisted phytoremediation of trace element contaminated soils.

Trichoderma virens PDR-28: a heavy metal-tolerant and plant growth-promoting fungus for remediation and bioenergy crop production on mine tailing soil.

PubMed

Babu, A Giridhar; Shim, Jaehong; Bang, Keuk-Soo; Shea, Patrick J; Oh, Byung-Taek

2014-01-01

A heavy metal-tolerant fungus, Trichoderma virens PDR-28, was isolated from rhizosphere soil and evaluated for use in remediating mine tailing soil and for plant biomass production. PDR-28 exhibited plant growth-promoting traits, including 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, acid phosphatase and phytase activity, siderophore production, and P solubilization. HMs were more available in mine tailing soil inoculated soil with PDR-28 than in uninoculated soil; the order of HM bioleaching was Cd > As > Zn > Pb > Cu. PDR-28 effectively removed HMs in the order of Pb > Cd > As > Zn > Cu from liquid media containing 100 mg HM L(-1). Inoculating HM-contaminated mine tailing soil with the fungus significantly increased the dry biomass of maize roots (64%) and shoots (56%). Chlorophyll, total soluble sugars (reducible and nonreducible), starch, and protein contents increased by 46%, 28%, 30%, and 29%, respectively, compared to plants grown in uninoculated soil. Inoculation increased heavy metal concentrations in maize roots by 25% (Cu) to 62% (Cd) and in shoots by 35% (Cu) to 64% (Pb) compared to uninoculated plants. Results suggest that PDR-28 would be beneficial for phytostabilization and plant biomass production as a potential source of biofuel in the quest for renewable energy. Copyright © 2013. Published by Elsevier Ltd.

Arbuscular Mycorrhizal Colonization Alters Subcellular Distribution and Chemical Forms of Cadmium in Medicago sativa L. and Resists Cadmium Toxicity

PubMed Central

Gao, Yanzheng

2012-01-01

Some plants can tolerate and even detoxify soils contaminated with heavy metals. This detoxification ability may depend on what chemical forms of metals are taken up by plants and how the plants distribute the toxins in their tissues. This, in turn, may have an important impact on phytoremediation. We investigated the impact of arbuscular mycorrhizal (AM) fungus, Glomus intraradices, on the subcellular distribution and chemical forms of cadmium (Cd) in alfalfa (Medicago sativa L.) that were grown in Cd-added soils. The fungus significantly colonized alfalfa roots by day 25 after planting. Colonization of alfalfa by G. intraradices in soils contaminated with Cd ranged from 17% to 69% after 25–60 days and then decreased to 43%. The biomass of plant shoots with AM fungi showed significant 1.7-fold increases compared to no AM fungi addition under the treatment of 20 mg·kg−1 Cd. Concentrations of Cd in the shoots of alfalfa under 0.5, 5, and 20 mg·kg−1 Cd without AM fungal inoculation are 1.87, 2.92, and 2.38 times higher, respectively, than those of fungi-inoculated plants. Fungal inoculation increased Cd (37.2–80.5%) in the cell walls of roots and shoots and decreased in membranes after 80 days of incubation compared to untreated plants. The proportion of the inactive forms of Cd in roots was higher in fungi-treated plants than in controls. Furthermore, although fungi-treated plants had less overall Cd in subcellular fragments in shoots, they had more inactive Cd in shoots than did control plants. These results provide a basis for further research on plant-microbe symbioses in soils contaminated with heavy metals, which may potentially help us develop management regimes for phytoremediation. PMID:23139811

Effect of Inoculation with Glomus versiforme on Cadmium Accumulation, Antioxidant Activities and Phytochelatins of Solanum photeinocarpum

PubMed Central

Tan, Shi-Yun; Jiang, Qiu-Yun; Zhuo, Feng; Liu, Hui; Wang, Yu-Tao; Li, Shao-Shan; Ye, Zhi-Hong; Jing, Yuan-Xiao

2015-01-01

The plant growth, phosphate acquisition, Cd translocation, phytochelatins (PCs) production and antioxidant parameters [superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione (GSH), ascorbate (ASA) and malonaldehyde (MDA)] were investigated in Cd-hyperaccumulator Solanum photeinocarpum inoculated with Glomus versiforme BGC GD01C (Gv) in Cd-added soils (0, 5, 10, 20, 40 mg Cd kg-1 soil). Mycorrhizal colonization rates were generally high (from 77% to 94%), and hardly affected by Cd. Gv colonization significantly enhanced P acquisition, growth and total Cd uptakes in both shoots and roots of S. photeinocarpum at all Cd levels. Meanwhile, Gv symbiosis significantly increased Cd concentration in the roots, and decreased Cd concentration in the shoots at all Cd levels, which indicates that Gv could promote phytostabilization by enhancing Cd accumulation in the roots to inhibit its translocation to shoots and the “dilution effects” linked to an increase in plant dry matter yield and a reduced Cd partitioning to shoots. Moreover, the improvement of CAT, POD and APX activities in the leaves of mycorrhizal plants infers that Gv symbiosis helped S. photeinocarpum to relieve oxidative damage to biomolecules in Cd-contaminated soil. The evident decline of MDA content in the leaves of mycorrhizal plants indicates that Gv symbiosis evidently improved antioxidant activities, and the enhancement of PCs production in the leaves of mycorrhizal plants suggests that Gv-inoculated plant may be more efficient to relieve Cd phytotoxicity. Therefore, the possible mechanisms of Cd phytotoxicity alleviation by Gv can be concluded as the decline of Cd concentration in the shoots and the improvement of P acquisition, PCs production and activities of CAT, POD, APX in mycorrhizal plants. PMID:26176959

Effect of various gases (methane, CO/sub 2/) on root development and/or mycorrhizae production on Virginia pine. [Pinus virginiana; Amanita rubescens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russo, V.M.; Klarman, W.L.

1975-01-01

Various flow rates of air, air containing methane, and air containing carbon dioxide were passed through sterile, nutrient-saturated sand in one-liter flasks. Sixteen-day-old axenic seedlings of Pinus virginiana were planted either prior to or immediately following treatment of medium. Some flasks were also inoculated with Amanita rubescens, a fungus commonly mycorrhizal with P. virginiana. Seedlings were maintained under continuous illumination for 30 days at 24 C and roots were then examined to determine development and/or mycorrhizal association. Dry weights of roots and whole seedlings were measured. Root development of seedlings planted in medium prior to treatment with air increased withmore » increase of flow-rate to 1.25 liters per hour. When treated with methane or carbon-dioxide fewer seedlings with developed root systems were produced. Seedlings planted in medium colonized by A. rubescens and treated with air or air containing carbon-dioxide produced increasing numbers of developed roots as flow rate increased, but other seedlings treated with methane produced fewer developed roots with increase in flow-rate. Mycorrhizal production was maximum at flow-rates between 0.25 and 0.6 liters. Generally fewer developed roots and/or mycorrhizae were produced by seedlings planted in treated medium than on similar seedlings planted before gas treatment. Dry weights generally paralleled root development.« less

[Phosphorus transfer between mixed poplar and black locust seedlings].

PubMed

He, Wei; Jia, Liming; Hao, Baogang; Wen, Xuejun; Zhai, Mingpu

2003-04-01

In this paper, the 32P radio-tracer technique was applied to study the ways of phosphorus transfer between poplar (Populus euramericana cv. 'I-214') and black locust (Robinia pseudoacacia). A five compartment root box (18 cm x 18 cm x 26 cm) was used for testing the existence of the hyphal links between the roots of two tree species when inoculated with vesicular-arbuscular (VA) mycorrhizal fungus (Glomus mosseae). Populus I-214 (donor) and Robinia pseudoacacia (receiver) were grown in two terminal compartments, separated by a 2 cm root-free soil layer. The root compartments were lined with bags of nylon mesh (38 microns) that allowed the passage of hyphae but not roots. The top soil of a mixed stand of poplar and black locust, autoclaved at 121 degrees C for one hour, was used for growing seedlings for testing. In 5 compartment root box, mycorrhizal root colonization of poplar was 34%, in which VA mycorrhizal fungus was inoculated, whereas 26% mycorrhizal root colonization was observed in black locust, the other terminal compartment, 20 weeks after planting. No root colonization was observed in non-inoculated plant pairs. This indicated that the mycorrhizal root colonization of black locust was caused by hyphal spreading from the poplar. Test of tracer isotope of 32P showed that the radioactivity of the treatment significantly higher than that of the control (P < 0.05), 14 days from the tracer applied, to 27 days after, when VA mycorrhizal fungus was inoculated in poplar root. Furthermore, mycorrhizal interconnections between the roots of poplar and black locust seedlings was observed in situ by binocular in root box. All these experiments showed that the hyphal links was formed between the roots of two species of trees inoculated by VA mycorrhizal fungus. Four treatments were designed according to if there were two nets (mesh 38 microns), 2 cm apart, between the poplar and black locust, and if the soil in root box was pasteurized. Most significant differences of radioactivity among four treatments appeared 44 days after feeding 32P, the radioactivity of the day was applied to estimating the contribution of the various possible transfer ways to the total amount of nutrient transfer. Level of 32P radioactivity was found to be significantly (P < 0.05) higher in leaves of the treatment of "no separated and soil non-pasteurized" (17.1 pulse.g-1.s-1) than in leaves of "net separated and soil non-pasteurized" (5.3 pulse.g-1.s-1), and also significantly higher in leaves of "no net separated and soil pasteurized" (11.5 pulse.g.s-1) than in leaves of "net separated and soil pasteurized" (2.3 pulse.g-1.s-1), and very significantly (P < 0.01) higher in leaves of "no net separated and soil non-pasteurized" than in leaves of "net separated and soil pasteurized", whereas the levels of 32P radioactivity were not significantly different between the other treatments. The results showed that root contact and root exudations were the main ways of phosphorus transfer between the two species and the amount of phosphorus transfer through these two ways accounted for 62% of the total. The activity of the microorganisms including VA mycorrhizal fungi and the interaction between the microorganisms and root contact and root exudations made up 38% of total amount of phosphorus. The effect of mycorrhizal hyphal links in the direct nutrient transfer between poplar and black locust through separate mesh (38 microns) was little.

The application of Arabidopsis thaliana in studying tripartite interactions among plants, beneficial fungal endophytes and biotrophic plant-parasitic nematodes.

PubMed

Martinuz, Alfonso; Zewdu, Getaneh; Ludwig, Nicole; Grundler, Florian; Sikora, Richard A; Schouten, Alexander

2015-04-01

The research demonstrated that Arabidopsis can be used as a model system for studying plant-nematode-endophyte tripartite interactions; thus, opening new possibilities for further characterizing the molecular mechanisms behind these interactions. Arabidopsis has been established as an important model system for studying plant biology and plant-microbe interactions. We show that this plant can also be used for studying the tripartite interactions among plants, the root-knot nematode Meloidogyne incognita and a beneficial endophytic isolate of Fusarium oxysporum, strain Fo162. In various plant species, Fo162 can systemically reduce M. incognita infection development and fecundity. Here it is shown that Fo162 can also colonize A. thaliana roots without causing disease symptoms, thus behaving as a typical endophyte. As observed for other plants, this endophyte could not migrate from the roots into the shoots and leaves. Direct inoculation of the leaves also did not result in colonization of the plant. A significant increase in plant fresh weight, root length and average root diameter was observed, suggesting the promotion of plant growth by the endophyte. The inoculation of A. thaliana with F. oxysporum strain Fo162 also resulted in a significant reduction in the number of M. incognita juveniles infecting the roots and ultimately the number of galls produced. This was also observed in a split-root experiment, in which the endophyte and nematode were spatially separated. The usefulness of Arabidopsis opens new possibilities for further dissecting complex tripartite interactions at the molecular and biochemical level.

Impact of 2,4-Diacetylphloroglucinol-Producing Biocontrol Strain Pseudomonas fluorescens F113 on Intraspecific Diversity of Resident Culturable Fluorescent Pseudomonads Associated with the Roots of Field-Grown Sugar Beet Seedlings

PubMed Central

Moënne-Loccoz, Yvan; Tichy, Hans-Volker; O'Donnell, Anne; Simon, Reinhard; O'Gara, Fergal

2001-01-01

The impact of the 2,4-diacetylphloroglucinol-producing biocontrol agent Pseudomonas fluorescens F113Rif on the diversity of the resident community of culturable fluorescent pseudomonads associated with the roots of field-grown sugar beet seedlings was evaluated. At 19 days after sowing, the seed inoculant F113Rif had replaced some of the resident culturable fluorescent pseudomonads at the rhizoplane but had no effect on the number of these bacteria in the rhizosphere. A total of 498 isolates of resident fluorescent pseudomonads were obtained and characterized by molecular means at the level of broad phylogenetic groups (by amplified ribosomal DNA restriction analysis) and at the strain level (with random amplified polymorphic DNA markers) as well as phenotypically (55 physiological tests). The introduced pseudomonad induced a major shift in the composition of the resident culturable fluorescent Pseudomonas community, as the percentage of rhizoplane isolates capable of growing on three carbon substrates (erythritol, adonitol, and l-tryptophan) not assimilated by the inoculant was increased from less than 10% to more than 40%. However, the pseudomonads selected did not display enhanced resistance to 2,4-diacetylphloroglucinol. The shift in the resident populations, which was spatially limited to the surface of the root (i.e., the rhizoplane), took place without affecting the relative proportions of phylogenetic groups or the high level of strain diversity of the resident culturable fluorescent Pseudomonas community. These results suggest that the root-associated Pseudomonas community of sugar beet seedlings is resilient to the perturbation that may be caused by a taxonomically related inoculant. PMID:11472913

Dark septate endophyte decreases stress on rice plants.

PubMed

Santos, Silvana Gomes Dos; Silva, Paula Renata Alves da; Garcia, Andres Calderin; Zilli, Jerri Édson; Berbara, Ricardo Luis Louro

Abiotic stress is one of the major limiting factors for plant development and productivity, which makes it important to identify microorganisms capable of increasing plant tolerance to stress. Dark septate endophytes can be symbionts of plants. In the present study, we evaluated the ability of dark septate endophytes isolates to reduce the effects of water stress in the rice varieties Nipponbare and Piauí. The experiments were performed under gnotobiotic conditions, and the water stress was induced with PEG. Four dark septate endophytes were isolated from the roots of wild rice (Oryza glumaepatula) collected from the Brazilian Amazon. Plant height as well as shoot and root fresh and dry matter were measured. Leaf protein concentrations and antioxidant enzyme activity were also estimated. The dark septate endophytes were grown in vitro in Petri dishes containing culture medium; they exhibited different levels of tolerance to salinity and water stress. The two rice varieties tested responded differently to inoculation with dark septate endophytes. Endophytes promoted rice plant growth both in the presence and in the absence of a water deficit. Decreased oxidative stress in plants in response to inoculation was observed in nearly all inoculated treatments, as indicated by the decrease in antioxidant enzyme activity. Dark septate endophytes fungi were shown to increase the tolerance of rice plants to stress caused by water deficiency. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Role of extrinsic arbuscular mycorrhizal fungi in heavy metal-contaminated wetlands with various soil moisture levels.

PubMed

Zheng, S; Wang, C; Shen, Z; Quan, Y; Liu, X

2015-01-01

This study presents an efficient heavy metal (HM) control method in HM-contaminated wetlands with varied soil moisture levels through the introduction of extrinsic arbuscular mycorrhizal fungi (AMF) into natural wetland soil containing indigenous AMF species. A pot culture experiment was designed to determine the effect of two soil water contents (5-8% and 25-30%), five extrinsic AMF inoculants (Glomus mosseae, G. clarum, G. claroideum, G. etunicatum, and G. intraradices), and HM contamination on root colonization, plant growth, and element uptake of common reed (Phragmites australis (Cav.) Trin. ex Steudel) plantlets in wetland soils. This study showed the prevalence of mycorrhizae in the roots of all P. australis plantlets, regardless of extrinsic AMF inoculations, varied soil moisture or HM levels. It seems that different extrinsic AMF inoculations effectively lowered HM concentrations in the aboveground tissues of P. australis at two soil moisture levels. However, metal species, metal concentrations, and soil moisture should also be very important factors influencing the elemental uptake performance of plants in wetland ecosystems. Besides, the soil moisture level significantly influenced plant growth (including height, and shoot and root dry weight (DW)), and extrinsic AMF inoculations differently affected shoot DW.

Role of Ni-tolerant Bacillus spp. and Althea rosea L. in the phytoremediation of Ni-contaminated soils.

PubMed

Khan, Waheed Ullah; Yasin, Nasim Ahmad; Ahmad, Sajid Rashid; Ali, Aamir; Ahmed, Shakil; Ahmad, Aqeel

2017-05-04

In our current study, four nickel-tolerant (Ni-tolerant) bacterial species viz, Bacillus thuringiensis 002, Bacillus fortis 162, Bacillus subtilis 174, and Bacillus farraginis 354, were screened using Ni-contaminated media. The screened microbes exhibited positive results for synthesis of indole acetic acid (IAA), siderophore production, and phosphate solubilization. The effects of these screened microbes on Ni mobility in the soil, root elongation, plant biomass, and Ni uptake in Althea rosea plants grown in Ni-contaminated soil (200 mg Ni kg -1 ) were evaluated. Significantly higher value for water-extractable Ni (38 mg kg -1 ) was observed in case of Ni-amended soils inoculated with B. subtilis 174. Similarly, B. thuringiensis 002, B. fortis 162, and B. subtilis 174 significantly enhanced growth and Ni uptake in A. rosea. The Ni uptake in the shoots and roots of B. subtilis 174-inoculated plants enhanced up to 1.7 and 1.6-fold, respectively, as compared to that in the un-inoculated control. Bacterial inoculation also significantly improved the root and shoot biomass of treated plants. The current study presents a novel approach for bacteria-assisted phytoremediation of Ni-contaminated areas.

Is there an association between root architecture and mycorrhizal growth response?

PubMed

Maherali, Hafiz

2014-10-01

The symbiosis between arbuscular mycorrhizal (AM) fungi and plants is evolutionarily widespread. The response of plant growth to inoculation by these fungi (mycorrhizal growth response; MGR) is highly variable, ranging from positive to negative. Some of this variation is hypothesized to be associated with root structure and function. Specifically, species with a coarse root architecture, and thus a limited intrinsic capacity to absorb soil nutrients, are expected to derive the greatest growth benefit from inoculation with AM fungi. To test this hypothesis, previously published literature and phylogenetic information were combined in a meta-analysis to examine the magnitude and direction of relationships among several root architectural traits and MGR. Published studies differed in the magnitude and direction of relationships between root architecture and MGR. However, when combined, the overall relationship between MGR and allocation to roots, root diameter, root hair length and root hair density did not differ significantly from zero. These findings indicate that possessing coarse roots is not necessarily a predictor of plant growth response to AM fungal colonization. Root architecture is therefore unlikely to limit the evolution of variation in MGR. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Effects of Meloidogyne spp. and Rhizoctonia solani on the Growth of Grapevine Rootings.

PubMed

Walker, G E

1997-06-01

A disease complex involving Meloidogyne incognita and Rhizoctonia solani was associated with stunting of grapevines in a field nursery. Nematode reproduction was occurring on both susceptible and resistant cultivars, and pot experiments were conducted to determine the virulence of this M. incognita population, and of M. javanica and M. hapla populations, to V. vinifera cv. Colombard (susceptible) and to V. champinii cv. Ramsey (regarded locally as highly resistant). The virulence of R. solani isolates obtained from roots of diseased grapevines also was determined both alone and in combination with M. incognita. Ramsey was susceptible to M. incognita (reproduction ratio 9.8 to 18.4 in a shadehouse and heated glasshouse, respectively) but was resistant to M. javanica and M. hapla. Colombard was susceptible to M. incognita (reproduction ratio 24.3 and 41.3, respectively) and M. javanica. Shoot growth was suppressed (by 35%) by M. incognita and, to a lesser extent, by M. hapla. Colombard roots were more severely galled than Ramsey roots by all three species, and nematode reproduction was higher on Colombard. Isolates of R. solani assigned to putative anastomosis groups 2-1 and 4, and an unidentified isolate, colonized and induced rotting of grapevine roots. Ramsey was more susceptible to root rotting than Colombard. Shoot growth was inhibited by up to 15% by several AG 4 isolates and by 20% by the AG 2-1 isolate. AG 4 isolates varied in their virulence. Root rotting was higher when grapevines were inoculated with both M. incognita and R. solani and was highest when nematode inoculation preceded the fungus. Shoot weights were lower when vines were inoculated with the nematode 13 days before the fungus compared with inoculation with both the nematode and the fungus on the same day. It was concluded that both the M. incognita population and some R. solani isolates were virulent against both Colombard and Ramsey, and that measures to prevent spread in nursery stock were therefore important.

Enhanced cadmium phytoremediation of Glycine max L. through bioaugmentation of cadmium-resistant bacteria assisted by biostimulation.

PubMed

Rojjanateeranaj, Pongsarun; Sangthong, Chirawee; Prapagdee, Benjaphorn

2017-10-01

This study examined the potential of three strains of cadmium-resistant bacteria, including Micrococcus sp., Pseudomonas sp. and Arthrobacter sp., to promote root elongation of Glycine max L. seedlings, soil cadmium solubility and cadmium phytoremediation in G. max L. planted in soil highly polluted with cadmium with and without nutrient biostimulation. Micrococcus sp. promoted root length in G. max L. seedlings under toxic cadmium conditions. Soil inoculation with Arthrobacter sp. increased the bioavailable fraction of soil cadmium, particularly in soil amended with a C:N ratio of 20:1. Pot culture experiments observed that the highest plant growth was in Micrococcus sp.-inoculated plants with nutrient biostimulation. Cadmium accumulation in the roots, stems and leaves of G. max L. was significantly enhanced by Arthrobacter sp. with nutrient biostimulation. A combined use of G. max L. and Arthrobacter sp. with nutrient biostimulation accelerated cadmium phytoremediation. In addition, cadmium was retained in roots more than in stems and leaves and G. max L. had the lowest translocation factor at all growth stages, suggesting that G. max L. is a phytostabilizing plant. We concluded that biostimulation-assisted bioaugmentation is an important strategy for improving cadmium phytoremediation efficiency. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Queries related to the technology of soybean seed inoculation with Bradyrhizobium spp].

PubMed

Lodeiro, Aníbal R

2015-01-01

With the aim of exploiting symbiotic nitrogen fixation, soybean crops are inoculated with selected strains of Bradyrhizobium japonicum, Bradyrhizobium diazoefficiens or Bradyrhizobium elkanii (collectively referred to as Bradyrhizobium spp.). The most common method of inoculation used is seed inoculation, whether performed immediately before sowing or using preinoculated seeds or pretreated seeds by the professional seed treatment. The methodology of inoculation should not only cover the seeds with living rhizobia, but must also optimize the chances of these rhizobia to infect the roots and nodulate. To this end, inoculated rhizobia must be in such an amount and condition that would allow them to overcome the competition exerted by the rhizobia of the allochthonous population of the soil, which are usually less effective for nitrogen fixation and thus dilute the effect of inoculation on yield. This optimization requires solving some queries related to the current knowledge of seed inoculation, which are addressed in this article. I conclude that the aspects that require further research are the adhesion and survival of rhizobia on seeds, the release of rhizobia once the seeds are deposited in the soil, and the movement of rhizobia from the vicinity of the seeds to the infection sites in the roots. Copyright © 2015 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Comparative evaluation of rotary ProTaper, Profile, and conventional stepback technique on reduction in Enterococcus faecalis colony-forming units and vertical root fracture resistance of root canals.

PubMed

Singla, Mamta; Aggarwal, Vivek; Logani, Ajay; Shah, Naseem

2010-03-01

The purpose of this in vitro study was to evaluate the effect of various root canal instrumentation techniques with different instrument tapers on cleaning efficacy and resultant vertical root fracture (VRF) strength of the roots. Fifty human mandibular first premolar roots were enlarged to ISO size 20, inoculated with Enterococcus faecalis [ATCC2912] for 72 hours and divided into 5 groups: group I: prepared with .02 taper hand instruments ISO size 40; group II: Profile .04 taper size 40; group III: Profile .06 taper size 40; group IV: ProTaper size F4; and group V (control group) further divided into: Va: with bacterial inoculation and no mechanical instrumentation; and Group Vb: neither bacterial inoculation nor mechanical instrumentation. Cleaning efficacy was evaluated in terms of reduction of colony forming units (CFUs). The VRF strength was evaluated using D11 spreader as wedge in an Instron testing machine. Root canals instrumented with ProTaper and 6% Profile instruments showed maximum reduction in CFUs, with statistically insignificant difference between them. The VRF resistance decreased in all instrumented groups. The difference of VRF between 2% and 4% taper Profile groups was statistically insignificant (P = .195). One-way analysis of variance showed that canals instrumented with ProTaper F4 showed maximum reduction in VRF resistance compared with control uninstrumented group. Profile 6% taper instruments offer the advantage of maximum debridement without significant reduction in root fracture resistance. Copyright 2010 Mosby, Inc. All rights reserved.

Growth response of Casuarina equisetifolia Forst. rooted stem cuttings to Frankia in nursery and field conditions.

PubMed

Karthikeyan, A; Chandrasekaran, K; Geetha, M; Kalaiselvi, R

2013-11-01

Casuarina equisetifolia Forst. is a tree crop that provides fuel wood, land reclamation, dune stabilization, and scaffolding for construction, shelter belts, and pulp and paper production. C. equisetifolia fixes atmospheric nitrogen through a symbiotic relationship with Frankia, a soil bacterium of the actinobacteria group. The roots of C. equisetifolia produce root nodules where the bacteria fix atmospheric nitrogen, which is an essential nutrient for all plant metabolic activities. However, rooted stem cuttings of elite clones of C. equisetifolia by vegetative propagation is being planted by the farmers of Pondicherry as costeffective method. As the vegetative propagation method uses inert material (vermiculite) for rooting there is no chance for Frankia association. Therefore after planting of these stocks the farmers are applying 150 kg of di-ammonium phosphate (DAP)/acre/year. To overcome this fertilizer usage, the Frankia-inoculated rooted stem cuttings were propagated under nursery conditions and transplanted in the nutrient-deficient soils of Karaikal, Pondicherry (India), in this study. Under nursery experiments the growth and biomass of C. equisetifolia rooted stem cuttings inoculated with Frankia showed 3 times higher growth and biomass than uninoculated control. These stocks were transplanted and monitored for their growth and survival for 1 year in the nutrient-deficient farm land. The results showed that the rooted stem cuttings of C. equisetifolia significantly improved growth in height (8.8 m), stem girth (9.6 cm) and tissue nitrogen content (3.3 mg g-1) than uninoculated controls. The soil nutrient status was also improved due to inoculation of Frankia.

Assessment of bacterial inoculant formulated with Paraburkholderia tropica to enhance wheat productivity.

PubMed

Bernabeu, Pamela Romina; García, Sabrina Soledad; López, Ana Clara; Vio, Santiago Adolfo; Carrasco, Natalia; Boiardi, José Luis; Luna, María Flavia

2018-05-25

Paraburkholderia tropica is an endophytic nitrogen-fixing bacterium isolated from the rhizosphere, rhizoplane, and internal tissues of sugarcane and corn plants in different geographical regions. Other plant-growth-promoting abilities, such as phosphate solubilization and antifungal activity, have also been reported for this bacterium. With an aim at investigating the potential use of P. tropica as an inoculant for improving the performance of wheat crop, in this work we evaluated an experimental inoculant formulated with P. tropica MTo-293 with respect to root colonization, the practical aspects of its application, and the effects under field conditions when applied to wheat seeds. Bacterial colonization was monitored by culture dependent techniques and the wheat yield determined by quantifying the total grain production in two different seasons. Rhizoplane and endophytic colonization in wheat roots was achieved efficiently (on average, 8 and 4 log colony-forming units/g fresh weight, respectively) even at relatively low concentrations of viable bacteria in the inoculum under controlled conditions. P. tropica was compatible with a widely used fungicide, maintained viability for 48 h once applied to seeds, and was also able to colonize wheat roots efficiently. Furthermore, we were able to formulate an inoculant that maintained bacterial viability for relatively long time periods. Preliminary field assays were realized, and even though the average yields values for the inoculated treatments remained above the uninoculated ones, no significant effects of inoculation were detected with or without fertilization. The correct physiologic behavior of P. tropica suggests the necessity to continue with field experiments under different conditions.

Accelerated Growth Rate and Increased Drought Stress Resilience of the Model Grass Brachypodium distachyon Colonized by Bacillus subtilis B26

PubMed Central

Charron, Jean-Benoit; Vali, Hojatollah; Bertrand, Annick; Jabaji, Suha

2015-01-01

Plant growth-promoting bacteria (PGB) induce positive effects in plants, for instance, increased growth and reduced abiotic stresses susceptibility. The mechanisms by which these bacteria impact the host plant are numerous, diverse and often specific. Here, we studied the agronomical, molecular and biochemical effects of the endophytic PGB Bacillus subtilis B26 on the full life cycle of Brachypodium distachyon Bd21, an established model species for functional genomics in cereal crops and temperate grasses. Inoculation of Brachypodium with B. subtilis strain B26 increased root and shoot weights, accelerated growth rate and seed yield as compared to control plants. B. subtilis strain B26 efficiently colonized the plant and was recovered from roots, stems and blades as well as seeds of Brachypodium, indicating that the bacterium is able to migrate, spread systemically inside the plant, establish itself in the aerial plant tissues and organs, and is vertically transmitted to seeds. The presence of B. subtilis strain B26 in the seed led to systemic colonization of the next generation of Brachypodium plants. Inoculated Brachypodium seedlings and mature plants exposed to acute and chronic drought stress minimized the phenotypic effect of drought compared to plants not harbouring the bacterium. Protection from the inhibitory effects of drought by the bacterium was linked to upregulation of the drought-response genes, DREB2B-like, DHN3-like and LEA-14-A-like and modulation of the DNA methylation genes, MET1B-like, CMT3-like and DRM2-like, that regulate the process. Additionally, total soluble sugars and starch contents increased in stressed inoculated plants, a biochemical indication of drought tolerance. In conclusion, we show a single inoculation of Brachypodium with a PGB affected the whole growth cycle of the plant, accelerating its growth rates, shortening its vegetative period, and alleviating drought stress effects. These effects are relevant to grasses and cereal crops. PMID:26103151

Accelerated Growth Rate and Increased Drought Stress Resilience of the Model Grass Brachypodium distachyon Colonized by Bacillus subtilis B26.

PubMed

Gagné-Bourque, François; Mayer, Boris F; Charron, Jean-Benoit; Vali, Hojatollah; Bertrand, Annick; Jabaji, Suha

2015-01-01

Plant growth-promoting bacteria (PGB) induce positive effects in plants, for instance, increased growth and reduced abiotic stresses susceptibility. The mechanisms by which these bacteria impact the host plant are numerous, diverse and often specific. Here, we studied the agronomical, molecular and biochemical effects of the endophytic PGB Bacillus subtilis B26 on the full life cycle of Brachypodium distachyon Bd21, an established model species for functional genomics in cereal crops and temperate grasses. Inoculation of Brachypodium with B. subtilis strain B26 increased root and shoot weights, accelerated growth rate and seed yield as compared to control plants. B. subtilis strain B26 efficiently colonized the plant and was recovered from roots, stems and blades as well as seeds of Brachypodium, indicating that the bacterium is able to migrate, spread systemically inside the plant, establish itself in the aerial plant tissues and organs, and is vertically transmitted to seeds. The presence of B. subtilis strain B26 in the seed led to systemic colonization of the next generation of Brachypodium plants. Inoculated Brachypodium seedlings and mature plants exposed to acute and chronic drought stress minimized the phenotypic effect of drought compared to plants not harbouring the bacterium. Protection from the inhibitory effects of drought by the bacterium was linked to upregulation of the drought-response genes, DREB2B-like, DHN3-like and LEA-14-A-like and modulation of the DNA methylation genes, MET1B-like, CMT3-like and DRM2-like, that regulate the process. Additionally, total soluble sugars and starch contents increased in stressed inoculated plants, a biochemical indication of drought tolerance. In conclusion, we show a single inoculation of Brachypodium with a PGB affected the whole growth cycle of the plant, accelerating its growth rates, shortening its vegetative period, and alleviating drought stress effects. These effects are relevant to grasses and cereal crops.

Phytohormones and induction of plant-stress tolerance and defense genes by seed and foliar inoculation with Azospirillum brasilense cells and metabolites promote maize growth.

PubMed

Fukami, Josiane; Ollero, Francisco Javier; Megías, Manuel; Hungria, Mariangela

2017-12-01

Azospirillum spp. are plant-growth-promoting bacteria used worldwide as inoculants for a variety of crops. Among the beneficial mechanisms associated with Azospirillum inoculation, emphasis has been given to the biological nitrogen fixation process and to the synthesis of phytohormones. In Brazil, the application of inoculants containing A. brasilense strains Ab-V5 and Ab-V6 to cereals is exponentially growing and in this study we investigated the effects of maize inoculation with these two strains applied on seeds or by leaf spray at the V2.5 stage growth-a strategy to relieve incompatibility with pesticides used for seed treatment. We also investigate the effects of spraying the metabolites of these two strains at V2.5. Maize growth was promoted by the inoculation of bacteria and their metabolites. When applied via foliar spray, although A. brasilense survival on leaves was confirmed by confocal microscopy and cell recovery, few cells were detected after 24 h, indicating that the effects of bacterial leaf spray might also be related to their metabolites. The major molecules detected in the supernatants of both strains were indole-3-acetic acid, indole-3-ethanol, indole-3-lactic acid and salicylic acid. RT-PCR of genes related to oxidative stress (APX1, APX2, CAT1, SOD2, SOD4) and plant defense (pathogenesis-related PR1, prp2 and prp4) was evaluated on maize leaves and roots. Differences were observed according to the gene, plant tissue, strain and method of application, but, in general, inoculation with Azospirillum resulted in up-regulation of oxidative stress genes in leaves and down-regulation in roots; contrarily, in general, PR genes were down-regulated in leaves and up-regulated in roots. Emphasis should be given to the application of metabolites, especially of Ab-V5 + Ab-V6 that in general resulted in the highest up-regulation of oxidative-stress and PR genes both in leaves and in roots. We hypothesize that the benefits of inoculation of Azospirillum on seeds or by leaf spray, as well as of leaf spraying of Azospirillum metabolites, are strongly correlated with the synthesis of phytohormones and by eliciting genes related to plant-stress tolerance and defense against pathogens.

Physiological aspects underlying the improved outplanting performance of Pinus pinaster Ait. seedlings associated with ectomycorrhizal inoculation.

PubMed

Sanchez-Zabala, Joseba; Majada, Juan; Martín-Rodrigues, Noemí; Gonzalez-Murua, Carmen; Ortega, Unai; Alonso-Graña, Manuel; Arana, Orats; Duñabeitia, Miren K

2013-11-01

Mycorrhizal inoculation of conifer roots is a key strategy to optimize establishment and performance of forest tree species under both natural and cultivated conditions and also to mitigate transplantation shock. However, despite being a common practice, inoculation in outdoor nursery conditions has been poorly studied. Here, we have evaluated effectiveness of four fungal species (Lactarius deliciosus, Lactarius quieticolor, Pisolithus arhizus, and Suillus luteus) in the production of mycorrhizal Pinus pinaster seedlings in an outdoor commercial nursery and their ability to improve seedling physiology and field performance. All inoculated seedlings showed a significant increase in growth at the end of the nursery stage and these differences remained after 3 years of growth in the field. Differences observed in the content of malondialdehyde, total chlorophyll, carotenoids, anthocyanins, and phenolic compounds from needles of mycorrhizal and control seedlings may reflect a different sensitivity to photo-oxidative damage. We conclude that ectomycorrhizal inoculation improves adaptability to changeable growing conditions of an outdoor nursery and produces a higher quality nursery stock, thereby enhancing seedling performance after planting.

The Effect of Low Oxygen Stress on Phytophthora cinnamomi Infection and Disease of Cork Oak Roots

Treesearch

Karel A. Jacobs; James D. MacDonald; Alison M. Berry; Laurence R. Costello

1997-01-01

The incidence and severity of Phytophthora cinnamomi Rands root disease was quantified in cork oak (Quercus suber L.) roots subjected to low oxygen (hypoxia) stress. Seedling root tips were inoculated with mycelial plugs of the fungus and incubated in ≤1, 3-4, or 21 percent oxygen for 5 days. Ninety-four percent of roots...

Penetration and development of Meloidogyne arenaria on two new grape rootstocks.

PubMed

Anwar, Safdar A; McKenry, M V

2002-06-01

Penetration, development, and reproduction of a virulent 'Harmony' population of Meloidogyne arenaria was studied on two nematode-resistant grape rootstocks 10-17A and 6-19B. 'Cabernet Sauvignon' was used as a susceptible control for comparison. Plants were inoculated with 100 freshly hatched second-stage juveniles (J2) of M. arenaria. Greater numbers of J2 penetrated roots of 'Cabernet' than 10-17A, and none penetrated roots of 6-19B 4 days after inoculation (DAI). At 7 DAI, vermiform J2 advanced to sausage-shaped J2 in roots of 'Cabernet,' penetrated roots of 6-19B, and had egressed from roots of 10-17A. Resistant rootstocks expressed hypersensitive responses to penetrating J2 along the root epidermis, among the cortical cells, and along the differentiating vascular bundles. At 13 DAI, 68% of the J2 had attained globose stage in roots of 'Cabernet,' whereas there was no development of vermiform J2 in roots of the other two rootstocks. The nematodes reproduced only in roots of 'Cabernet.' Lack of development of J2 in roots of the two resistant grape rootstocks might be the result of a hypersensitive response to J2 feeding.

Biochemical and Molecular Phylogenetic Study of Agriculturally Useful Association of a Nitrogen-Fixing Cyanobacterium and Nodule Sinorhizobium with Medicago sativa L.

PubMed Central

Karaushu, E. V.; Kravzova, T. R.; Vorobey, N. A.; Kiriziy, D. A.; Olkhovich, O. P.; Taran, N. Yu.; Kots, S. Ya.; Omarova, E.

2015-01-01

Seed inoculation with bacterial consortium was found to increase legume yield, providing a higher growth than the standard nitrogen treatment methods. Alfalfa plants were inoculated by mono- and binary compositions of nitrogen-fixing microorganisms. Their physiological and biochemical properties were estimated. Inoculation by microbial consortium of Sinorhizobium meliloti T17 together with a new cyanobacterial isolate Nostoc PTV was more efficient than the single-rhizobium strain inoculation. This treatment provides an intensification of the processes of biological nitrogen fixation by rhizobia bacteria in the root nodules and an intensification of plant photosynthesis. Inoculation by bacterial consortium stimulates growth of plant mass and rhizogenesis and leads to increased productivity of alfalfa and to improving the amino acid composition of plant leaves. The full nucleotide sequence of the rRNA gene cluster and partial sequence of the dinitrogenase reductase (nifH) gene of Nostoc PTV were deposited to GenBank (JQ259185.1, JQ259186.1). Comparison of these gene sequences of Nostoc PTV with all sequences present at the GenBank shows that this cyanobacterial strain does not have 100% identity with any organisms investigated previously. Phylogenetic analysis showed that this cyanobacterium clustered with high credibility values with Nostoc muscorum. PMID:26114100

Biochemical and Molecular Phylogenetic Study of Agriculturally Useful Association of a Nitrogen-Fixing Cyanobacterium and Nodule Sinorhizobium with Medicago sativa L.

PubMed

Karaushu, E V; Lazebnaya, I V; Kravzova, T R; Vorobey, N A; Lazebny, O E; Kiriziy, D A; Olkhovich, O P; Taran, N Yu; Kots, S Ya; Popova, A A; Omarova, E; Koksharova, O A

2015-01-01

Seed inoculation with bacterial consortium was found to increase legume yield, providing a higher growth than the standard nitrogen treatment methods. Alfalfa plants were inoculated by mono- and binary compositions of nitrogen-fixing microorganisms. Their physiological and biochemical properties were estimated. Inoculation by microbial consortium of Sinorhizobium meliloti T17 together with a new cyanobacterial isolate Nostoc PTV was more efficient than the single-rhizobium strain inoculation. This treatment provides an intensification of the processes of biological nitrogen fixation by rhizobia bacteria in the root nodules and an intensification of plant photosynthesis. Inoculation by bacterial consortium stimulates growth of plant mass and rhizogenesis and leads to increased productivity of alfalfa and to improving the amino acid composition of plant leaves. The full nucleotide sequence of the rRNA gene cluster and partial sequence of the dinitrogenase reductase (nifH) gene of Nostoc PTV were deposited to GenBank (JQ259185.1, JQ259186.1). Comparison of these gene sequences of Nostoc PTV with all sequences present at the GenBank shows that this cyanobacterial strain does not have 100% identity with any organisms investigated previously. Phylogenetic analysis showed that this cyanobacterium clustered with high credibility values with Nostoc muscorum.

Mycorrhizal-Mediated Lower Proline Accumulation in Poncirus trifoliata under Water Deficit Derives from the Integration of Inhibition of Proline Synthesis with Increase of Proline Degradation

PubMed Central

Zou, Ying-Ning; Wu, Qiang-Sheng; Huang, Yong-Ming; Ni, Qiu-Dan; He, Xin-Hua

2013-01-01

Proline accumulation was often correlated with drought tolerance of plants infected by arbuscular mycorrhizal fungi (AMF), whereas lower proline in some AM plants including citrus was also found under drought stress and the relevant mechanisms have not been fully elaborated. In this study proline accumulation and activity of key enzymes relative to proline biosynthesis (▵1-pyrroline-5-carboxylate synthetase, P5CS; ornithine-δ-aminotransferase, OAT) and degradation (proline dehydrogenase, ProDH) were determined in trifoliate orange (Poncirus trifoliata, a widely used citrus rootstock) inoculated with or without Funneliformis mosseae and under well-watered (WW) or water deficit (WD). AMF colonization significantly increased plant height, stem diameter, leaf number, root volume, biomass production of both leaves and roots and leaf relative water content, irrespectively of water status. Water deficit induced more tissue proline accumulation, in company with an increase of P5CS activity, but a decrease of OAT and ProDH activity, no matter whether under AM or no-AM. Compared with no-AM treatment, AM treatment resulted in lower proline concentration and content in leaf, root, and total plant under both WW and WD. The AMF colonization significantly decreased the activity of both P5CS and OAT in leaf, root, and total plant under WW and WD, except for an insignificant difference of root OAT under WD. The AMF inoculation also generally increased tissue ProDH activity under WW and WD. Plant proline content significantly positively correlated with plant P5CS activity, negatively with plant ProDH activity, but not with plant OAT activity. These results suggest that AM plants may suffer less from WD, thereby inducing lower proline accumulation, which derives from the integration of an inhibition of proline synthesis with an enhancement of proline degradation. PMID:24260421

Improvement in phytoremediation potential of Solanum nigrum under cadmium contamination through endophytic-assisted Serratia sp. RSC-14 inoculation.

PubMed

Khan, Abdur Rahim; Ullah, Ihsan; Khan, Abdul Latif; Park, Gun-Seok; Waqas, Muhammad; Hong, Sung-Jun; Jung, Byung Kwon; Kwak, Yunyoung; Lee, In-Jung; Shin, Jae-Ho

2015-09-01

The growth of hyperaccumulator plants is often compromised by increased toxicity of metals like cadmium (Cd). However, extraction of such metals from the soil can be enhanced by endophytic microbial association. Present study was aimed to elucidate the potential of microbe-assisted Cd phytoextraction in hyperaccumulator Solanum nigrum plants and their interactions under varied Cd concentrations. An endophytic bacteria Serratia sp. RSC-14 was isolated from the roots of S. nigrum. In addition to Cd tolerance up to 4 mM, the RSC-14 exhibited phosphate solubilization and secreted plant growth-promoting phytohormones such as indole-3-acetic acid (54 μg/mL). S. nigrum plants were inoculated with RSC-14 and were grown in different concentrations of Cd (0, 10, and 30 mg Cd kg(-1) sand). Results revealed that Cd treatment caused significant cessation in plant growth, biomass, and chlorophyll content, whereas significantly higher malondialdehyde (MDA) and electrolyte production in leaves were observed in a dose-dependent manner. Conversely, RSC-14 inoculation relived the toxic effects of Cd-induced stress by significantly increasing root/shoot growth, biomass production, and chlorophyll content and decreasing MDA and electrolytes contents. Ameliorative effects on host growth were also observed by the regulation of metal-induced oxidative stress enzymes such as catalase, peroxidase, and polyphenol peroxidase. Activities of these enzymes were significantly reduced in RSC-14 inoculated plants as compared to control plants under Cd treatments. The lower activities of stress responsive enzymes suggest modulation of Cd stress by RSC-14. The current findings support the beneficial uses of Serratia sp. RSC-14 in improving the phytoextraction abilities of S. nigrum plants in Cd contamination.

Endophytic bacteria improve phytoremediation of Ni and TCE co-contamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weyens, N.; van der Lelie, D.; Croes, S.

The aim of this work was to investigate if engineered endophytes can improve phytoremediation of co-contaminations by organic pollutants and toxic metals. As a model system, yellow lupine was inoculated with the endophyte Burkholderia cepacia VM1468 possessing (a) the pTOM-Bu61 plasmid, coding for constitutive trichloroethylene (TCE) degradation, and (b) the ncc-nre Ni resistance/sequestration system. Plants were exposed to Ni and TCE and (a) Ni and TCE phytotoxicity, (b) TCE degradation and evapotranspiration, and (c) Ni concentrations in the roots and shoots were determined. Inoculation with B. cepacia VM1468 resulted in decreased Ni and TCE phytotoxicity, as measured by 30% increasedmore » root biomass and up to 50% decreased activities of enzymes involved in anti-oxidative defence in the roots. In addition, TCE evapotranspiration showed a decreasing trend and a 5 times higher Ni uptake was observed after inoculation. Engineered endophytes can improve phytoremediation of mixed contaminations via enhanced degradation of organic contaminants and improved metal uptake and translocation.« less

Cultivation-Based and Molecular Assessment of Bacterial Diversity in the Rhizosheath of Wheat under Different Crop Rotations

PubMed Central

Tahir, Muhammad; Mirza, M. Sajjad; Hameed, Sohail; Dimitrov, Mauricio R.; Smidt, Hauke

2015-01-01

A field study was conducted to compare the formationand bacterial communities of rhizosheaths of wheat grown under wheat-cotton and wheat-rice rotation and to study the effects of bacterial inoculation on plant growth. Inoculation of Azospirillum sp. WS-1 and Bacillus sp. T-34 to wheat plants increased root length, root and shoot dry weight and dry weight of rhizosheathsoil when compared to non-inoculated control plants, and under both crop rotations. Comparing both crop rotations, root length, root and shoot dry weight and dry weight of soil attached with roots were higher under wheat-cotton rotation. Organic acids (citric acid, malic acid, acetic acid and oxalic acid) were detected in rhizosheaths from both rotations, with malic acid being most abundant with 24.8±2 and 21.3±1.5 μg g-1 dry soil in wheat-cotton and wheat-rice rotation, respectively. Two sugars (sucrose, glucose) were detected in wheat rhizosheath under both rotations, with highest concentrations of sucrose (4.08±0.5 μg g-1and 7.36±1.0 μg g-1) and glucose (3.12±0.5 μg g-1 and 3.01± μg g-1) being detected in rhizosheaths of non-inoculated control plants under both rotations. Diversity of rhizosheath-associated bacteria was evaluated by cultivation, as well as by 454-pyrosequencing of PCR-tagged 16S rRNA gene amplicons. A total of 14 and 12 bacterial isolates predominantly belonging to the genera Arthrobacter, Azospirillum, Bacillus, Enterobacter and Pseudomonaswere obtained from the rhizosheath of wheat grown under wheat-cotton and wheat-rice rotation, respectively. Analysis of pyrosequencing data revealed Proteobacteria, Bacteriodetes and Verrucomicrobia as the most abundant phyla in wheat-rice rotation, whereas Actinobacteria, Firmicutes, Chloroflexi, Acidobacteria, Planctomycetes and Cyanobacteria were predominant in wheat-cotton rotation. From a total of 46,971 sequences, 10.9% showed ≥97% similarity with 16S rRNA genes of 32 genera previously shown to include isolates with plant growth promoting activity (nitrogen fixation, phosphate-solubilization, IAA production). Among these, the most predominant genera were Arthrobacter, Azoarcus, Azospirillum, Bacillus, Cyanobacterium, Paenibacillus, Pseudomonas and Rhizobium. PMID:26121588

Arbuscular mycorrhiza improve growth, nitrogen uptake, and nitrogen use efficiency in wheat grown under elevated CO2.

PubMed

Zhu, Xiancan; Song, Fengbin; Liu, Shengqun; Liu, Fulai

2016-02-01

Effects of the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis on plant growth, carbon (C) and nitrogen (N) accumulation, and partitioning was investigated in Triticum aestivum L. plants grown under elevated CO2 in a pot experiment. Wheat plants inoculated or not inoculated with the AM fungus were grown in two glasshouse cells with different CO2 concentrations (400 and 700 ppm) for 10 weeks. A (15)N isotope labeling technique was used to trace plant N uptake. Results showed that elevated CO2 increased AM fungal colonization. Under CO2 elevation, AM plants had higher C concentration and higher plant biomass than the non-AM plants. CO2 elevation did not affect C and N partitioning in plant organs, while AM symbiosis increased C and N allocation into the roots. In addition, plant C and N accumulation, (15)N recovery rate, and N use efficiency (NUE) were significantly higher in AM plants than in non-AM controls under CO2 enrichment. It is concluded that AM symbiosis favors C and N partitioning in roots, increases C accumulation and N uptake, and leads to greater NUE in wheat plants grown at elevated CO2.

Effects of Azospirillum brasilense with genetically modified auxin biosynthesis gene ipdC upon the diversity of the indigenous microbiota of the wheat rhizosphere.

PubMed

Baudoin, Ezékiel; Lerner, Anat; Mirza, M Sajjad; El Zemrany, Hamdy; Prigent-Combaret, Claire; Jurkevich, Edouard; Spaepen, Stijn; Vanderleyden, Jos; Nazaret, Sylvie; Okon, Yaacov; Moënne-Loccoz, Yvan

2010-04-01

The phytostimulatory properties of Azospirillum inoculants, which entail production of the phytohormone indole-3-acetic acid (IAA), can be enhanced by genetic means. However, it is not known whether this could affect their interactions with indigenous soil microbes. Here, wheat seeds were inoculated with the wild-type strain Azospirillum brasilense Sp245 or one of three genetically modified (GM) derivatives and grown for one month. The GM derivatives contained a plasmid vector harboring the indole-3-pyruvate/phenylpyruvate decarboxylase gene ipdC (IAA production) controlled either by the constitutive promoter PnptII or the root exudate-responsive promoter PsbpA, or by an empty vector (GM control). All inoculants displayed equal rhizosphere population densities. Only inoculation with either ipdC construct increased shoot biomass compared with the non-inoculated control. At one month after inoculation, automated ribosomal intergenic spacer analysis (ARISA) revealed that the effect of the PsbpA construct on bacterial community structure differed from that of the GM control, which was confirmed by 16S rDNA-based denaturing gradient gel electrophoresis (DGGE). The fungal community was sensitive to inoculation with the PsbpA construct and especially the GM control, based on ARISA data. Overall, fungal and bacterial communities displayed distinct responses to inoculation of GM A. brasilense phytostimulators, whose effects could differ from those of the wild-type.

Symbiosis of Arbuscular Mycorrhizal Fungi and Robinia pseudoacacia L. Improves Root Tensile Strength and Soil Aggregate Stability

PubMed Central

Zhang, Haoqiang; Liu, Zhenkun; Chen, Hui; Tang, Ming

2016-01-01

Robinia pseudoacacia L. (black locust) is a widely planted tree species on Loess Plateau for revegetation. Due to its symbiosis forming capability with arbuscular mycorrhizal (AM) fungi, we explored the influence of arbuscular mycorrhizal fungi on plant biomass, root morphology, root tensile strength and soil aggregate stability in a pot experiment. We inoculated R. pseudoacacia with/without AM fungus (Rhizophagus irregularis or Glomus versiforme), and measured root colonization, plant growth, root morphological characters, root tensile force and tensile strength, and parameters for soil aggregate stability at twelve weeks after inoculation. AM fungi colonized more than 70% plant root, significantly improved plant growth. Meanwhile, AM fungi elevated root morphological parameters, root tensile force, root tensile strength, Glomalin-related soil protein (GRSP) content in soil, and parameters for soil aggregate stability such as water stable aggregate (WSA), mean weight diameter (MWD) and geometric mean diameter (GMD). Root length was highly correlated with WSA, MWD and GMD, while hyphae length was highly correlated with GRSP content. The improved R. pseudoacacia growth, root tensile strength and soil aggregate stability indicated that AM fungi could accelerate soil fixation and stabilization with R. pseudoacacia, and its function in revegetation on Loess Plateau deserves more attention. PMID:27064570

Symbiosis of Arbuscular Mycorrhizal Fungi and Robinia pseudoacacia L. Improves Root Tensile Strength and Soil Aggregate Stability.

PubMed

Zhang, Haoqiang; Liu, Zhenkun; Chen, Hui; Tang, Ming

2016-01-01

Robinia pseudoacacia L. (black locust) is a widely planted tree species on Loess Plateau for revegetation. Due to its symbiosis forming capability with arbuscular mycorrhizal (AM) fungi, we explored the influence of arbuscular mycorrhizal fungi on plant biomass, root morphology, root tensile strength and soil aggregate stability in a pot experiment. We inoculated R. pseudoacacia with/without AM fungus (Rhizophagus irregularis or Glomus versiforme), and measured root colonization, plant growth, root morphological characters, root tensile force and tensile strength, and parameters for soil aggregate stability at twelve weeks after inoculation. AM fungi colonized more than 70% plant root, significantly improved plant growth. Meanwhile, AM fungi elevated root morphological parameters, root tensile force, root tensile strength, Glomalin-related soil protein (GRSP) content in soil, and parameters for soil aggregate stability such as water stable aggregate (WSA), mean weight diameter (MWD) and geometric mean diameter (GMD). Root length was highly correlated with WSA, MWD and GMD, while hyphae length was highly correlated with GRSP content. The improved R. pseudoacacia growth, root tensile strength and soil aggregate stability indicated that AM fungi could accelerate soil fixation and stabilization with R. pseudoacacia, and its function in revegetation on Loess Plateau deserves more attention.

Performance of Choctawhatchee Sand Pine Seedlings Inoculated with Ectomycorrhizal Fungi and Outplanted in the Sandhills of North Florida

Treesearch

John L. Ruehle; Raymond H. Brendemuehl

1981-01-01

Studies were conducted on the effect of the ectomycorrhizal symbiont Pisolifhus tincrorius (Pt) on nursery production and field performance of both container-grown and bare-root Choctawhatchee sand pine (CSP). In two separate experiments, seedlings inoculated with Pt were planted on prepared sites on the sandhills of north Florida. Inoculation with Pt improved the...

The effect of phosphate bio-fertilizer (Barvar-2) on the growth of marigold.

PubMed

Zaredost, Fatemeh; Hashemabadi, Davood; Ziyabari, Maryam Barari; Torkashvand, Ali Mohammadi; Kaviani, Behzad; Solimandarabi, Maryam Jadid; Zarchini, Mohammad

2014-03-01

The present study was conducted to study the individual and combined effect of bio-fertilizer (Barvar-2) and chemical phosphate fertilizer on the floral quality of marigold (Tagetes erecta L.). A factorial experiment was carried out which consisted of two factors: i) inoculation of seed, root and seed + root with bio-fertilizer (Barvar-2) and control; application of chemical phosphorus at 100 mg I(-1), 200 mg l(-1), 300 mg l(-1) and 400 mg l(-1) levels. In this study, flowering time, display life, fresh and dry weight of flower, available soil phosphorus, shoot phosphorus and carotenoid content were evaluated. Results showed that the combined effect of bio- and chemical fertilizer was insignificant (p < 1 and 5%) for most of the characteristics studied except for shoot phosphorus and carotenoid content in petals. The lowest time to flowering (64.67 days) was obtained in seeds and transplant roots inoculation to bio-fertilizer x 400 mg I(-1) P. Maximum display life (25.35), fresh weight (16.20 g), carotenoid content (3.903 mg g(-1) d. wt.) and concentration of P in shoots (0.352%) were observed in transplant roots inoculation to bio-fertilizer x 400 mg I(-1) P.

[Effect of ectomycorrhizae on the growth of Picea koraiensis seedlings].

PubMed

Song, Rui-Qing; Wu, Ke

2005-12-01

Basidioscarps of Agaricales in different Picea koraiensis forest plantations were collected during August-October, 2000. 36 isolaters of species of Agaricales were obtained by isolating and culturing to the basidioscarps. Through indoor inoculation test on seedlings of Picea koraiensis, 6 ectomycorrhizae fungi cultures were obtained from 36 isolaters. The inoculation results show that the period for ectomycorrhizae inoculation to 1-year seedlings of Picea koraiensis should be about 30 days after seedlings emerging, the suitable temperature for ectomycorrhizae forming is about 20 degrees C. 6 ectomycorrhizae strains all have growth-promoting effect to the seedlings of Picea koraiensis. The contents of chlorophyll a of the seedlings inoculated strains of Agaricus silvaticus, 031 and L15 were significantly higher than other strains and control. The contents of chlorophyll b in the seedlings inoculated strains 009, 004, Agaricus silvaticus and L15 were significantly higher than other strains and control. The weights of seedlings which inoculated strains 009, 025, 031, Agaricus silvaticus and L15 were significantly different to control, the weight of seedlings inoculated strains of Agaricus silvaticus and L15 are 19.23% and 23.08% more than control; The heights of the seedlings inoculated 6 strains all have significant difference to control, the weight of seedlings inoculated strains of Agaricus silvaticus and L15 are 17.83% and 16.37% more than control. The results of outdoor inoculation show that the seedlings inoculated Agaricus silvaticus grow best on height, 9.25% more than control after inoculated 70 days; the seedlings inoculated strain L15 grow best on collar diameter, 9.92% more than control after inoculated 70 days; the lateral root numbers of seedlings inoculated strain 009 is largest, 51.91% more than control after inoculated 70 days; the main roots of seedlings inoculated strain 009 are longest, 3.36% more than control after inoculated 70 days; the ectomycorrhizae fungi infestation percentage of seedlings inoculated strain 031 is highest, 13.90% more than control after inoculated 70 days; the photosynthesis of seedlings inoculated strain 031 is more powerful, 20.02% more than control after inoculated 70 days. To sum up, strain 009, strain 031 and strain L15 should be fine strains to seedlings of Picea koraiensis.

Small RNA profiling reveals important roles for miRNAs in Arabidopsis response to Bacillus velezensis FZB42.

PubMed

Xie, Shanshan; Jiang, Haiyang; Xu, Zhilan; Xu, Qianqian; Cheng, Beijiu

2017-09-20

Bacillus velezensis FZB42 (previously classified as Bacillus amyloliquefaciens FZB42) has been confirmed to successfully colonize plant roots and enhance defense response against pathogen infection. This study indicated that FZB42 inoculation enhanced Arabidopsis defense response against Pseudomonas syringae DC3000 through inducing the expression of PR1, PDF1.2 and stomata closure. To further clarify the induced defense response at miRNA level, sRNA libraries from Arabidopsis roots inoculated with FZB42 and control were constructed and sequenced. The reads of 21nt and 24nt in length were the most abundant groups in FZB42-treated library and control library, respectively. 234 known miRNAs and 16 novel miRNAs were identified. Among them, 11 known miRNAs and 4 novel miRNAs were differentially expressed after FZB42 inoculation. Moreover cis-elements (TC-rich repeats, TCA-element and CGTCA-motif) associated with plant defense were also found in the promoters of these miRNAs. Additionally, 141 mRNAs were predicted as potential targets of these differentially expressed miRNAs. GO annotations of the target genes indicated their potential roles in polyamine biosynthetic process and intracellular protein transport biological process, which may contribute to increased defense response. Our findings indicated that Bacillus velezensis FZB42 inoculation altered the expression of Arabidopsis miRNAs and their target genes, which were associated with defense response. Copyright © 2017 Elsevier B.V. All rights reserved.

Melanised endophytic fungi may increase stores of organic carbon in soil

NASA Astrophysics Data System (ADS)

McGee, Peter; Mukasa Mugerwa, Tendo

2013-04-01

The processes underlying the carbon cycle in soil, especially sequestration of organic carbon (OC), are poorly understood. Hydrolysis and oxidation reduce organic matter. Hydrolysis degrades linear organic molecules in aerobic and anaerobic conditions, though it is slower in anaerobic conditions. Aromatic compounds are only degraded by oxidation. Oxygen is by far the most common electron acceptor in soil. Anaerobic conditions preclude oxidation in soil and will result in the preservation of aromatic compounds so long as the conditions remain anaerobic. We experimentally tested this model using melanised endophytic fungi. Melanin is a polyaromatic compound that can be readily visualised, though is difficult to quantify. An endophytic association provides the fungus with an ongoing source of energy. Fungal hyphae elongate considerable distances in soil where they may colonise aggregates, the core of which may be anaerobic. The hypothesis we tested is that melanised endophytic fungi increase OC in soil. Seedlings of subterranean clover inoculated with single isolates were grown in split pots where the impact of the fungus could be quantified in the hyphal chamber, separated from the roots by a steel mesh. We found that melanised endophytic fungi significantly increased OC and aromatic carbon in a well-aggregated carbon-rich soil. OC increased by up to 17% within 14 weeks. Twenty out of 24 isolates statistically significantly increased and none decreased OC. Increases differed between fungal isolates. Increases in the hyphal chamber were independent of any change in OC associated with the roots of the host plant. The storage of OC in field soils is being explored. Inoculation of plant roots with melanised endophytic fungi offers one means whereby OC may be increased in field soils.

Differential expression of oil palm pathology genes during interactions with Ganoderma boninense and Trichoderma harzianum.

PubMed

Alizadeh, Fahimeh; Abdullah, Siti Nor Akmar; Khodavandi, Alireza; Abdullah, Faridah; Yusuf, Umi Kalsom; Chong, Pei Pei

2011-07-01

The expression profiles of Δ9 stearoyl-acyl carrier protein desaturase (SAD1 and SAD2) and type 3 metallothionein (MT3-A and MT3-B) were investigated in seedlings of oil palm (Elaeis guineensis) artificially inoculated with the pathogenic fungus Ganoderma boninense and the symbiotic fungus Trichoderma harzianum. Expression of SAD1 and MT3-A in roots and SAD2 in leaves were significantly up-regulated in G. boninense inoculated seedlings at 21 d after treatment when physical symptoms had not yet appeared and thereafter decreased to basal levels when symptoms became visible. Our finding demonstrated that the SAD1 expression in leaves was significantly down-regulated to negligible levels at 42 and 63 d after treatment. The transcripts of MT3 genes were synthesized in G. boninense inoculated leaves at 42 d after treatment, and the analyses did not show detectable expression of these genes before 42 d after treatment. In T. harzianum inoculated seedlings, the expression levels of SAD1 and SAD2 increased gradually and were stronger in roots than leaves, while for MT3-A and MT3-B, the expression levels were induced in leaves at 3d after treatment and subsequently maintained at same levels until 63d after treatment. The MT3-A expression was significantly up-regulated in roots at 3d after treatment and thereafter were maintained at this level. Both SAD and MT3 expression were maintained at maximum levels or at levels higher than basal. This study demonstrates that oil palm was able to distinguish between pathogenic and symbiotic fungal interactions, thus resulting in different transcriptional activation profiles of SAD and MT3 genes. Increases in expression levels of SAD and MT3 would lead to enhanced resistance against G. boninense and down-regulation of genes confer potential for invasive growth of the pathogen. Differences in expression profiles of SAD and MT3 relate to plant resistance mechanisms while supporting growth enhancing effects of symbiotic T. harzianum. Copyright © 2011 Elsevier GmbH. All rights reserved.

Arbuscular Mycorrhiza Alleviates Restrictions to Substrate Water Flow and Delays Transpiration Limitation to Stronger Drought in Tomato.

PubMed

Bitterlich, Michael; Sandmann, Martin; Graefe, Jan

2018-01-01

Arbuscular mycorrhizal fungi (AMF) proliferate in soil pores, on the surface of soil particles and affect soil structure. Although modifications in substrate moisture retention depend on structure and could influence plant water extraction, mycorrhizal impacts on water retention and hydraulic conductivity were rarely quantified. Hence, we asked whether inoculation with AMF affects substrate water retention, water transport properties and at which drought intensity those factors become limiting for plant transpiration. Solanum lycopersicum plants were set up in the glasshouse, inoculated or not with Funneliformis mosseae , and grown for 35 days under ample water supply. After mycorrhizal establishment, we harvested three sets of plants, one before (36 days after inoculation) and the second (day 42) and third (day 47) within a sequential drying episode. Sampling cores were introduced into pots before planting. After harvest, moisture retention and substrate conductivity properties were assessed and water retention and hydraulic conductivity models were fitted. A root water uptake model was adopted in order to identify the critical substrate moisture that induces soil derived transpiration limitation. Neither substrate porosity nor saturated water contents were affected by inoculation, but both declined after substrates dried. Drying also caused a decline in pot water capacity and hydraulic conductivity. Plant available water contents under wet (pF 1.8-4.2) and dry (pF 2.5-4.2) conditions increased in mycorrhizal substrates and were conserved after drying. Substrate hydraulic conductivity was higher in mycorrhizal pots before and during drought exposure. After withholding water from pots, higher substrate drying rates and lower substrate water potentials were found in mycorrhizal substrates. Mycorrhiza neither affected leaf area nor root weight or length. Consistently with higher substrate drying rates, AMF restored the plant hydraulic status, and increased plant transpiration when soil moisture declined. The water potential at the root surface and the resistance to water flow in the rhizosphere were restored in mycorrhizal pots although the bulk substrate dried more. Finally, substrates colonized by AMF can be more desiccated before substrate water flux quantitatively limits transpiration. This is most pronounced under high transpiration demands and complies with a difference of over 1,000 hPa in substrate water potential.

Beneficial cyanobacteria and eubacteria synergistically enhance bioavailability of soil nutrients and yield of okra.

PubMed

Manjunath, Mallappa; Kanchan, Amrita; Ranjan, Kunal; Venkatachalam, Siddarthan; Prasanna, Radha; Ramakrishnan, Balasubramanian; Hossain, Firoz; Nain, Lata; Shivay, Yashbir Singh; Rai, Awadhesh Bahadur; Singh, Bijendra

2016-02-01

Microorganisms in the rhizosphere mediate the cycling of nutrients, their enhanced mobilisation and facilitate their uptake, leading to increased root growth, biomass and yield of plants. We examined the promise of beneficial cyanobacteria and eubacteria as microbial inoculants, applied singly or in combination as consortia or biofilms, to improve growth and yields of okra. Interrelationships among the microbial activities and the micro/macro nutrient dynamics in soils and okra yield characteristics were assessed along with the changes in the soil microbiome. A significant effect of microbial inoculation on alkaline phosphatase activity was recorded both at the mid-crop and harvest stages. Microbial biomass carbon values were highest due to the Anabaena sp. - Providencia sp. (CR1 + PR3) application. The yield of okra ranged from 444.6-478.4 g(-1) plant and a positive correlation (0.69) recorded between yield and root weight. The application of Azotobacter led to the highest root weight and yield. The concentration of Zn at mid-crop stage was 60-70% higher in the Azotobacter sp. and Calothrix sp. inoculated soils, as compared to uninoculated control. Iron concentration in soil was more than 2-3 folds higher than control at the mid-crop stage, especially due to the application of Anabaena-Azotobacter biofilm and Azotobacter sp. Both at the mid-crop and harvest stages, the PCR-DGGE profiles of eubacterial communities were similar among the uninoculated control, the Anabaena sp. - Providencia sp. (CW1 + PW5) and the Anabaena-Azotobacter biofilm treatments. Although the profiles of the Azotobacter, Calothrix and CR1 + PR3 treatments were identical at these stages of growth, the profile of CR1 + PR3 was clearly distinguishable. The performance of the inoculants, particularly Calothrix (T6) and consortium of Anabaena and Providencia (CR1 + PR3; T5), in terms of microbiological and nutrient data, along with generation of distinct PCR-DGGE profiles suggested their superiority and emphasized the utility of combining microbiological and molecular tools in the selection of effective microbial inoculants.

Carbon partitioning patterns of mycorrhizal versus non-mycorrhizal plants: real-time dynamic measurements using 11 CO2.

PubMed

Wang, G M; Coleman, D C; Freckman, D W; Dyer, M I; McNAUGHTON, S J; Agra, M A; Goeschl, J D

1989-08-01

Gas exchange and carbon allocation patterns were studied in two populations of Panicum coloratum, an Africa C-4 grass. The plants were grown in split-root pots, containing partially sterilized soil, with one side either inoculated (I) or not inoculated (NI) with a vesicular arbuscular (VA) mycorrhizal Fungus, Gigaspora margarita. Net carbon exchange rates (CER) and stomatal conductances were measured with conventional gas exchange apparatus, and carbon assimilation, translocation, and allocation were measured using photosynthetically-fixed 11 CO 2 . Mycorrhizal infection on one half of the split-root system caused a 20%, increase in CER. The effect on CER was less in tillers on the opposite side of the plants from the infected half of the roots. The rate at which photosynthates were stored in the leaves was 45% higher. Sink activity (concentration of labelled photosynthates in stem phloem tissue) more than doubled in 1 versus NI plants. CER and stomatal conductances, along with most of the carbon allocation patterns, were nearly identical between the NI (control) high grazing and low grazing ecotypes. However, VA mycorrhizal fungi caused a greater storage of photosynthates in the low grazing ecotype.

Internalization of Sapovirus, a Surrogate for Norovirus, in Romaine Lettuce and the Effect of Lettuce Latex on Virus Infectivity

PubMed Central

Esseili, Malak A.; Zhang, Zhenwen

2012-01-01

Noroviruses are the leading cause of food-borne outbreaks, including those that involve lettuce. The culturable porcine sapovirus (SaV) was used as a norovirus surrogate to study the persistence and the potential transfer of the virus from roots to leaves and from outer to inner leaves of lettuce plants. Treatment of lettuce with SaV was done through the roots of young plants, the soil, or the outer leaves of mature plants. Sampling of roots, xylem sap, and inner and outer leaves followed by RNA extraction and SaV-specific real-time reverse transcription (RT)-PCR was performed at 2 h and on postinoculation days (PID) 2, 5, 7, 14, and/or 28. When SaV was inoculated through the roots, viral RNA persisted on the roots and in the leaves until PID 28. When the virus was inoculated through the soil, viral RNA was detected on the roots and in the xylem sap until PID 14; viral RNA was detected in the leaves only until PID 2. No infectious virus was detected inside the leaves for either treatment. When SaV was inoculated through the outer leaves, viral RNA persisted on the leaves until PID 14; however, the virus did not transfer to inner leaves. Infectious viral particles on leaves were detected only at 2 h postinoculation. The milky sap (latex) of leaves, but not the roots' xylem sap, significantly decreased virus infectivity when tested in vitro. Collectively, our results showed the transfer of SaV from roots to leaves through the xylem system and the capacity of the sap of lettuce leaves to decrease virus infectivity in leaves. PMID:22752176

Combined inoculation of Pseudomonas fluorescens and Trichoderma harzianum for enhancing plant growth of vanilla (Vanilla planifolia).

PubMed

Sandheep, A R; Asok, A K; Jisha, M S

2013-06-15

This study was conducted to evaluate the plant growth promoting efficiency of combined inoculation of rhizobacteria on Vanilla plants. Based on the in vitro performance of indigenous Trichoderma spp. and Pseudomonas spp., four effective antagonists were selected and screened under greenhouse experiment for their growth enhancement potential. The maximum percentage of growth enhancement were observed in the combination of Trichoderma harzianum with Pseudomonas fluorescens treatment followed by Pseudomonas fluorescens, Trichoderma harzianum, Pseudomonas putida and Trichoderma virens, respectively in decreasing order. Combined inoculation of Trichoderma harzianum and Pseudomonas fluorescens registered the maximum length of vine (82.88 cm), highest number of leaves (26.67/plant), recorded the highest fresh weight of shoots (61.54 g plant(-1)), fresh weight of roots (4.46 g plant(-1)) and dry weight of shoot (4.56 g plant(-1)) where as the highest dry weight of roots (2.0806 g plant(-1)) were achieved with treatments of Pseudomonas fluorescens. Among the inoculated strains, combined inoculation of Trichoderma harzianum and Pseudomonas fluorescens recorded the maximum nitrogen uptake (61.28 mg plant(-1)) followed by the combined inoculation of Trichoderma harzianum (std) and Pseudomonas fluorescens (std) (55.03 mg plant(-1)) and the highest phosphorus uptake (38.80 mg plant(-1)) was recorded in dual inoculation of Trichoderma harzianum and Pseudomonas fluorescens.

The influence of arbuscular mycorrhizal fungi inoculation on yam (Dioscorea spp.) tuber weights and secondary metabolite content.

PubMed

Lu, Fun-Chi; Lee, Chen-Yu; Wang, Chun-Li

2015-01-01

Arbuscular mycorrhizal fungi (AMF) are widely distributed in nature. They live in the roots of higher plants, in a symbiotic relationship. In this study, five commercial species of yams (Dioscorea spp.) were inoculated with six species of AMF, Glomus clarum, G. etunicatum, G. fasciculatum, Gigaspora sp., G. mosseae, and Acaulospora sp., in field cultivation conditions to investigate the influence of AMF inoculation on tuber weights and secondary metabolite content in yam tubers. The results showed that mycorrhizae formation rates ranged from 63.33% to 90%. G. etunicatum inoculation treatment increased the tube weights of the five species of yam tubers by 39%, 35%, 20%, 56%, and 40% for Tainung 1, Tainung 2, Ercih, Zihyuxieshu, and Tainung 5, respectively. The content of secondary metabolites, such as polyphenols, flavonoids, and anthocyanin, was significantly increased by the AMF treatment in tuber flesh and peel of all the tested yam species. Specifically, the maximums exchange of secondary metabolite contents increased to 40%, 42%, and 106% for polyphenols, flavonoids, and anthocyanin, respectively, in the tuber fresh. This study revealed that different species of yam had varying degrees of affinity with various AMF species; selecting effective AMF species is necessary to facilitate yam growth and improve the quality and quantity of yam tubers.

The effect of plant growth-promoting rhizobacteria on the phytoextraction of Cd and Zn by Brassica napus L.

PubMed

Dąbrowska, G; Hrynkiewicz, K; Trejgell, A; Baum, C

2017-07-03

The test strains Bacteroidetes bacterium (Ba), Pseudomonas fluorescens (Pf) and Variovorax sp. (Va) were selected in advance for their in vitro capability for growth promotion of rapeseed in the presence of increased concentrations of Cd, Cu, Pb and Zn in the medium. In the pot experiment, the strains were used for single Ba, Pf, Va or combined Ba + Pf, Ba + Va, Pf + Va, and Ba + Pf + Va inoculation of B. napus growing in contaminated soil from alluvial deposits. The positive effect of bacterial strains on plant growth was observed in vitro, but was not confirmed in situ in the contaminated soil, where the tested strains inhibited biomass production, rather than stimulating it. However, single inoculation with Ba significantly increased the chlorophyll content and K + concentration in the leaves. The inoculation of rapeseed with Ba and Va strains was indicated to be the most promising combination for phytoextraction of Cd and Zn from contaminated soil. Combined inoculation with Pf+Va and Pf + Ba+Va significantly decreased the concentration of heavy metals in the roots of rapeseed. We conclude that suitable combinations of PGPR can control the metal uptake of B. napus, selectively increasing either metal extraction or metal stabilization in the rhizosphere and offering promising applications in soil remediation.

Colonization of Clonostachys rosea on soybean root inoculated with Fusarium graminearum

USDA-ARS?s Scientific Manuscript database

Soybean root rot, caused by Fusarium graminearum, is a devastating disease. Clonostachys rosea has been reported to have protection against plant pathogens in different crops. The objectives of this study were to determine if a strain of C. rosea (ACM941) can colonize soybean root that were inocula...

Symbiotic regulation of plant growth, development and reproduction

Treesearch

Russell J. Rodriguez; D. Carl Freeman; E. Durant McArthur; Yong Ok Kim; Regina S. Redman

2009-01-01

The growth and development of rice (Oryzae sativa) seedlings was shown to be regulated epigenetically by a fungal endophyte. In contrast to un-inoculated (nonsymbiotic) plants, endophyte colonized (symbiotic) plants preferentially allocated resources into root growth until root hairs were well established. During that time symbiotic roots expanded at...

A test system to quantify inoculum in runoff from Phytophthora ramorum-infected plant roots

USDA-ARS?s Scientific Manuscript database

Foliar hosts of Phytophthora ramorum are often susceptible to root infection, but the epidemiological significance of such infections is unknown. We used a standardized test system to study inoculum in runoff from root-infected Viburnum tinus cuttings. Viburnum were inoculated by pouring a sporang...

Boron fertilization and the root morphology of shortleaf pine seedlings inoculated with Pisolithus tinctorius

Treesearch

M.A. Sword; H.E. Garrett

1991-01-01

Benefits associated with ectomycorrhizal infection are well established. However, exploitation of this symbiosis has been hindered, in part, by the inability to obtain consistently high infection rates. Past research in our laboratory has identified a twofold increase in Pisolithus tinctorius [(Pers.) Coker and Couch] ectomycorrhizal infection of shortleaf pine (Pinus...

Effect of diflubenzuron on the development of Pinus pinaster seedlings inoculated with the ectomycorrhizal fungus Pisolithus tinctorius.

PubMed

Ramos, Miguel A; Sousa, Nadine R; Franco, Albina R; Costa, Vítor; Oliveira, Rui S; Castro, Paula M L

2013-01-01

Diflubenzuron (DFB) is an insecticide commonly used to control forest pests. The objectives of this study were to assess the effect of diflubenzuron on the development of Pinus pinaster seedlings and Pisolithus tinctorius under laboratory conditions and to study the possible protective role of this ectomycorrhizal fungus against the effects of diflubenzuron. In vitro experiments revealed that diflubenzuron inhibited fungal growth at all tested concentrations (0.01, 0.1, 1, 10 and 100 mg L(-1)). Root growth was inhibited at the two highest diflubenzuron concentrations. The activity of the antioxidant defence system of non-inoculated P. pinaster increased at 1 and 10 mg DFB kg(-1) substrate, and inoculation increased the threshold to the highest concentration. The protective role of the ectomycorrhizal fungus was seen in the increase of CAT activity. This study revealed that despite causing no mortality, diflubenzuron has the ability to cause sub-lethal damage to P. pinaster. The disproportionate use of this insecticide may lead to higher amounts of its residues in soil and the biosphere, endangering trees, fungi and their symbiosis.

Effects of nursery preconditioning through mycorrhizal inoculation and drought in Arbutus unedo L. plants.

PubMed

Navarro García, Alejandra; Del Pilar Bañón Árias, Sebastián; Morte, Asunción; Sánchez-Blanco, María Jesús

2011-01-01

The influence of a water deficit treatment and mycorrhizal inoculation with Pisolithus tinctorius (Pers.) Coker and Couch on the water relations, gas exchange, and plant growth in Arbutus unedo L. plants was studied in order to evaluate the hardening process during the nursery period. The ability to withstand the adverse conditions after transplantation was also studied. Mycorrhizal and non-mycorrhizal seedlings of A. unedo were pot-grown for 4 months in a greenhouse (nursery period), during which time two irrigation treatments, well watered (100% water holding capacity, leaching 20% of the applied water) and deficit irrigation (50% of the well watered), were applied. Subsequently, the plants were transplanted to the field and well irrigated (transplanting period), after which and until the end of the experiment they received no water (establishment period). At the end of the nursery period, both water deficit and mycorrhizae were seen to have altered the plant morphology. Mycorrhizal plants had lower leaf area and improved leaf color parameters, while the water deficit increased root dry weight and the root/shoot ratio. Mycorrhizal plants had higher leaf water potential values than non-inoculated plants. Mycorrhizae increased stomatal conductance and photosynthesis values, especially in stressed plants. Drought led to an osmotic adjustment and a decrease in the leaf water potential values at turgor loss point in the mycorrhizal plants. Cell wall rigidity, measured as increased bulk modulus of elasticity, was decreased by the mycorrhizae effect. After transplanting, no differences were found in the water relations or gas exchange values between treatments. During the establishment period, the plants that had been exposed to both drought and mycorrhizae showed a better water status (higher leaf water and turgor potential values) and higher gas exchange values. In conclusion, water deficit and mycorrhizal inoculation of A. unedo plants in nursery produced changes in tissue water relations, gas exchange, and growth, related with the acclimation process in the seedlings, which could provide better resistance to drought and stress conditions following planting.

Beauveria bassiana and Metarhizium anisopliae endophytically colonize cassava roots following soil drench inoculation

USDA-ARS?s Scientific Manuscript database

The fungal entomopathogens Beauveria bassiana and Metarhizium anisopliae were investigated to determine if endophytic colonization could be achieved in cassava. An inoculation method based on drenching the soil around cassava stems using conidial suspensions resulted in endophytic colonization of ca...

Cell viability of mycorrhiza helper bacteria solid inoculant in different carrier material

NASA Astrophysics Data System (ADS)

Asyiah, Iis Nur; Hindersah, Reginawanti; Harni, Rita

2018-02-01

Roots of food crops are colonized by nonpathogenic mycorrhizal fungi which show natural ability to control plant pathogen. Mycorrhizal establishment in plant roots is affected by rhizobacteria, known as mycorrhiza helper bacteria (MHB), which has synergetic effects on mycorrhizal associations. Laboratory experiment has been conducted to assess the best carrier material to develop well-qualified MHB of Pseudomonas diminuta and Bacillus subtilis solid inoculant. Carrier materials were 100 mesh organic matter of agricultural waste. Different spore concentration of both bacterial liquid inoculants were grown on three kinds of 100-mesh organic matter and stored at room temperature up to 90 days. Cell viability of both MHB were counted by serial dilution plate method by using specific medium. The results showed that sugar cane baggase ash was the best carrier material to maintain cell viability for both MHB. However, the population of Pseudomonas diminuta and Bacillus subtilis in sugar cane baggase ash were slightly decreased after 90 days. The use of sugarcane baggase ash for solid MHB inoculant development could be suggested.

Differential antimicrobial activity of silver nanoparticles to bacteria Bacillus subtilis and Escherichia coli, and toxicity to crop plant Zea mays and beneficial B. subtilis-inoculated Z. mays

NASA Astrophysics Data System (ADS)

Doody, Michael A.; Wang, Dengjun; Bais, Harsh P.; Jin, Yan

2016-10-01

As silver nanoparticles (AgNPs) have become increasingly used in commercial antimicrobial agents and industrial and military products, concerns are increasing over their broad environmental and health impacts and risks because they are finding their way to the environment. This study was designed to quantify the antimicrobial activity of citrate-coated AgNPs (c-AgNPs; transmission electron microscope size of 44.9 ± 7.2 nm) to two species of bacteria, i.e., Gram-positive Bacillus subtilis and Gram-negative Escherichia coli, and toxicity to a major crop plant Zea mays and beneficial bacteria-inoculated plant (i.e., B. subtilis-inoculated Z. mays symbiont). Our results reveal that the exposure of c-AgNPs significantly inhibited bacteria growth and altered their growth kinetics. Z. mays experienced significant sublethal effects including reduced root length and biomass, and hyper-accumulation of Ag in roots. The beneficial interactions between B. subtilis and Z. mays were weakened as well because both species suffered sublethal effects. Potential mechanisms leading to the antimicrobial activity and toxicity of c-AgNPs to the bacteria, plant, and plant-bacteria symbiont examined in this study were discussed. Taken together, our findings advance the current knowledge of AgNPs antimicrobial property or toxicity to bacteria, crop plant, and beneficial plant-bacteria symbiotic interaction, which is a critical component for NPs environmental impact and risk assessment.

Proteomic Analysis Reveals the Positive Roles of the Plant-Growth-Promoting Rhizobacterium NSY50 in the Response of Cucumber Roots to Fusarium oxysporum f. sp. cucumerinum Inoculation

PubMed Central

Du, Nanshan; Shi, Lu; Yuan, Yinghui; Li, Bin; Shu, Sheng; Sun, Jin; Guo, Shirong

2016-01-01

Plant-growth-promoting rhizobacteria (PGPR) can both improve plant growth and enhance plant resistance against a variety of environmental stresses. To investigate the mechanisms that PGPR use to protect plants under pathogenic attack, transmission electron microscopy analysis and a proteomic approach were designed to test the effects of the new potential PGPR strain Paenibacillus polymyxa NSY50 on cucumber seedling roots after they were inoculated with the destructive phytopathogen Fusarium oxysporum f. sp. cucumerinum (FOC). NSY50 could apparently mitigate the injury caused by the FOC infection and maintain the stability of cell structures. The two-dimensional electrophoresis (2-DE) approach in conjunction with MALDI-TOF/TOF analysis revealed a total of 56 proteins that were differentially expressed in response to NSY50 and/or FOC. The application of NSY50 up-regulated most of the identified proteins that were involved in carbohydrate metabolism and amino acid metabolism under normal conditions, which implied that both energy generation and the production of amino acids were enhanced, thereby ensuring an adequate supply of amino acids for the synthesis of new proteins in cucumber seedlings to promote plant growth. Inoculation with FOC inhibited most of the proteins related to carbohydrate and energy metabolism and to protein metabolism. The combined inoculation treatment (NSY50+FOC) accumulated abundant proteins involved in defense mechanisms against oxidation and detoxification as well as carbohydrate metabolism, which might play important roles in preventing pathogens from attacking. Meanwhile, western blotting was used to analyze the accumulation of enolase (ENO) and S-adenosylmethionine synthase (SAMs). NSY50 further increased the expression of ENO and SAMs under FOC stress. In addition, NSY50 adjusted the transcription levels of genes related to those proteins. Taken together, these results suggest that P. polymyxa NSY50 may promote plant growth and alleviate FOC-induced damage by improving the metabolism and activation of defense-related proteins in cucumber roots. PMID:28018395

Effect of Piriformospora indica inoculation on root development and distribution of maize (Zea mays L.) in the presence of petroleum contaminated soil

NASA Astrophysics Data System (ADS)

Zamani, Javad; Hajabbasi, Mohammad Ali; Alaie, Ebrahim

2014-05-01

The root systems of most terrestrial plants are confronted to various abiotic and biotic stresses. One of these abiotic stresses is contamination of soil with petroleum hydrocarbon, which the efficiency of phytoremediation of petroleum hydrocarbons in soils is dependent on the ability of plant roots to development into the contaminated soils. Piriformospora indica represents a recently discovered fungus that transfers considerable beneficial impact to its host plants. A rhizotron experiment was conducted to study the effects of P. Indica inoculation on root distribution and root and shoot development of maize (Zea mays L.) in the presence of three patterns of petroleum contamination in the soil (subsurface contamination, continuous contamination and without contamination (control)). Root distribution and root and shoot development were monitored over time. The final root and shoot biomass and the final TPH concentration in the rhizosphere were determined. Analysis of digitized images which were prepared of the tracing of the appeared roots along the front rhizotrons showed the depth and total length of root network in the contamination treatments were significantly decreased. Although the degradation of TPH in the rhizosphere of maize was significant, but there were no significant differences between degradation of TPH in the rhizosphere of +P. indica plants in comparison to -P. indica plants.

Antifungal genes expressed in transgenic pea (Pisum sativum L.) do not affect root colonization of arbuscular mycorrhizae fungi.

PubMed

Kahlon, Jagroop Gill; Jacobsen, Hans-Jörg; Cahill, James F; Hall, Linda M

2017-10-01

Genetically modified crops have raised concerns about unintended consequences on non-target organisms including beneficial soil associates. Pea transformed with four antifungal genes 1-3 β glucanase, endochitinase, polygalacturonase-inhibiting proteins, and stilbene synthase is currently under field-testing for efficacy against fungal diseases in Canada. Transgenes had lower expression in the roots than leaves in greenhouse experiment. To determine the impact of disease-tolerant pea or gene products on colonization by non-target arbuscular mycorrhizae and nodulation by rhizobium, a field trial was established. Transgene insertion, as single gene or stacked genes, did not alter root colonization by arbuscular mycorrhiza fungus (AMF) or root nodulation by rhizobium inoculation in the field. We found no effect of transgenes on the plant growth and performance although, having a dual inoculant with both AMF and rhizobium yielded higher fresh weight shoot-to-root ratio in all the lines tested. This initial risk assessment of transgenic peas expressing antifungal genes showed no deleterious effect on non-target organisms.

Localization of the Bacillus subtilis beta-propeller phytase transcripts in nodulated roots of Phaseolus vulgaris supplied with phytate.

PubMed

Maougal, Rim Tinhinen; Bargaz, Adnane; Sahel, Charaf; Amenc, Laurie; Djekoun, Abdelhamid; Plassard, Claude; Drevon, Jean-Jacques

2014-04-01

Soil organic phosphorus (Po) such as phytate, which comprises up to 80 % of total Po, must be hydrolyzed by specific enzymes called phytases to be used by plants. In contrast to plants, bacteria, such as Bacillus subtilis, have the ability to use phytate as the sole source of P due to the excretion of a beta-propeller phytase (BPP). In order to assess whether the B. subtilis BPP could make P available from phytate for the benefit of a nodulated legume, the P-sensitive recombinant inbred line RIL147 of Phaseolus vulgaris was grown under hydroaeroponic conditions with either 12.5 μM phytate (C₆H₁₈O₂₄P₆) or 75 μmol Pi (K₂HPO₄), and inoculated with Rhizobium tropici CIAT899 alone, or co-inoculated with both B. subtilis DSM 10 and CIAT899. The in situ RT-PCR of BPP genes displayed the most intense fluorescent BPP signal on root tips. Some BPP signal was found inside the root cortex and the endorhizosphere of the root tip, suggesting endophytic bacteria expressing BPP. However, the co-inoculation with B. subtilis was associated with a decrease in plant P content, nodulation and the subsequent plant growth. Such a competitive effect of B. subtilis on P acquisition from phytate in symbiotic nitrogen fixation might be circumvented if the rate of inoculation were reasoned in order to avoid the inhibition of nodulation by excess B. subtilis proliferation. It is concluded that B. subtilis BPP gene is expressed in P. vulgaris rhizosphere.

Carbohydrate and ethane release with Erwinia carotovora subspecies betavasculorum--induced necrosis.

PubMed

Kuykendall, L David; Hunter, William J

2008-02-01

Erwinia carotovora subspecies betavasculorum, also known as E. betavasculorum and Pectobacterium betavasculorum, is a soil bacterium that has the capacity to cause root rot necrosis of sugarbeets. The qualitatively different pathogenicity exhibited by the virulent E. carotovora strain and two avirulent strains, a Citrobacter sp. and an Enterobacter cloacae, was examined using digital analysis of photographic evidence of necrosis as well as for carbohydrate, ethane, and ethylene release compared with uninoculated potato tuber slices. Visual scoring of necrosis was superior to digital analysis of photographs. The release of carbohydrates and ethane from potato tuber slices inoculated with the soft rot necrosis-causing Erwinia was significantly greater than that of potato tuber slices that had not been inoculated or that had been inoculated with the nonpathogenic E. cloacae and Citrobacter sp. strains. Interestingly, ethylene production from potato slices left uninoculated or inoculated with the nonpathogenic Citrobacter strain was 5- to 10-fold higher than with potato slices inoculated with the pathogenic Erwinia strain. These findings suggest that (1) carbohydrate release might be a useful measure of the degree of pathogenesis, or relative virulence; and that (2) bacterial suppression of ethylene formation may be a critical step in root rot disease formation.

Co-ordinated Changes in the Accumulation of Metal Ions in Maize (Zea mays ssp. mays L.) in Response to Inoculation with the Arbuscular Mycorrhizal Fungus Funneliformis mosseae.

PubMed

Ramírez-Flores, M Rosario; Rellán-Álvarez, Rubén; Wozniak, Barbara; Gebreselassie, Mesfin-Nigussie; Jakobsen, Iver; Olalde-Portugal, Víctor; Baxter, Ivan; Paszkowski, Uta; Sawers, Ruairidh J H

2017-10-01

Arbuscular mycorrhizal symbiosis is an ancient interaction between plants and fungi of the phylum Glomeromycota. In exchange for photosynthetically fixed carbon, the fungus provides the plant host with greater access to soil nutrients via an extensive network of root-external hyphae. Here, to determine the impact of the symbiosis on the host ionome, the concentration of 19 elements was determined in the roots and leaves of a panel of 30 maize varieties, grown under phosphorus-limiting conditions, with or without inoculation with the fungus Funneliformis mosseae. Although the most recognized benefit of the symbiosis to the host plant is greater access to soil phosphorus, the concentration of a number of other elements responded significantly to inoculation across the panel as a whole. In addition, variety-specific effects indicated the importance of plant genotype to the response. Clusters of elements were identified that varied in a co-ordinated manner across genotypes, and that were maintained between non-inoculated and inoculated plants. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Survival of Phytophthora ramorum in Rhododendron root balls and in rootless substrates

Treesearch

A. Vercauteren; M. Riedel; M. Maes; S. Werres; K. Heungens

2013-01-01

This study assesses the survival of Phytophthora ramorum in the root ball of Rhododendron container plants as well as in different rootless forest substrates and a horticultural potting medium. Following inoculation of the root balls, the aboveground plant parts stayed symptomless, whilst the pathogen could be recovered with a...

Improvement of plant growth and seed yield in Jatropha curcas by a novel nitrogen-fixing root associated Enterobacter species

PubMed Central

2013-01-01

Background Jatropha curcas L. is an oil seed producing non-leguminous tropical shrub that has good potential to be a fuel plant that can be cultivated on marginal land. Due to the low nutrient content of the targeted plantation area, the requirement for fertilizer is expected to be higher than other plants. This factor severely affects the commercial viability of J. curcas. Results We explored the feasibility to use endophytic nitrogen-fixing bacteria that are native to J. curcas to improve plant growth, biomass and seed productivity. We demonstrated that a novel N-fixing endophyte, Enterobacter sp. R4-368, was able to colonize in root and stem tissues and significantly promoted early plant growth and seed productivity of J. curcas in sterilized and non-sterilized soil. Inoculation of young seedling led to an approximately 57.2% increase in seedling vigour over a six week period. At 90 days after planting, inoculated plants showed an average increase of 25.3%, 77.7%, 27.5%, 45.8% in plant height, leaf number, chlorophyll content and stem volume, respectively. Notably, inoculation of the strain led to a 49.0% increase in the average seed number per plant and 20% increase in the average single seed weight when plants were maintained for 1.5 years in non-sterilized soil in pots in the open air. Enterobacter sp. R4-368 cells were able to colonize root tissues and moved systemically to stem tissues. However, no bacteria were found in leaves. Promotion of plant growth and leaf nitrogen content by the strain was partially lost in nifH, nifD, nifK knockout mutants, suggesting the presence of other growth promoting factors that are associated with this bacterium strain. Conclusion Our results showed that Enterobacter sp. R4-368 significantly promoted growth and seed yield of J. curcas. The application of the strains is likely to significantly improve the commercial viability of J. curcas due to the reduced fertilizer cost and improved oil yield. PMID:24083555

Mycorrhizo-remediation of lead/zinc mine tailings using vetiver: a field study.

PubMed

Wu, Sheng Chun; Wong, Ching Chi; Shu, Wen Sheng; Khan, Adual G; Wong, Ming Hung

2011-01-01

A field study of Pb/Zn mine tailings was conducted to assess the influence of AM fungi and refuse compost on phytoremediation using vetiver grass slips. Our investigation revealed that vetiver could thrive on Pb/Zn mine tailings. The addition of refuse compost resulted in biomass that was more than 3-times higher when compared with the control, and were mainly attributed to an improvement of soil properties, as well as better nutrient supply than untreated control. AMF inoculation also significantly increased the dry matter of vetiver by a rate of 8.1-13.8%. It was observed that concentrations of N and P in the shoots were significantly higher in mycorrhizal treatments than those without AMF inoculation. However, AMF inoculation significantly decreased the metal concentrations in root, but not in shoot. Based on the results, it seems clear that AMF can play an essential role in the phytostabilization of metal contaminated soils.

Inoculation testing of Apollo 12 materials

NASA Technical Reports Server (NTRS)

1969-01-01

E. Landrum Young, Brown and Root Northrop, injects a young Japanese quail with a suspension of pulvarized Apollo 12 lunar material within a quarantine cabinet in the Invertebrate, Aves and Fish Laboratory of the Lunar Receiving Laboratory, bldg 37, Manned Spacecraft Center. The bird is being inoculated in the abdominal cavity.

Dieback of Acacia koa in Hawaii: Ecological and pathological characteristics of affected stands

USGS Publications Warehouse

Anderson, R.C.; Gardner, D.E.; Daehler, C.C.; Meinzer, F.C.

2002-01-01

Koa (Acacia koa) is an endemic Hawaiian tree that serves as a keystone species in the upper elevation forests of all the main islands. In the Mauna Loa Strip area of Hawaii Volcanoes National Park, mature koa stands are suffering from an unexplained dieback that has increased in severity since it was first noticed approximately 25 years ago. The dieback is often evident in patches, and generally spreads within stands in a radial fashion from a localized infection center. Entire crowns of affected trees become wilted, with foliage gradually progressing from an apparent healthy to a completely chlorotic condition. Although most trees die soon after the onset of symptoms, some trees are able to survive crown death by producing epicormic shoots on the lower portions of the trunk. Previously published studies reported that a vascular wilt fungus (Fusarium oxysporum f. sp. koae) was associated with koa seeds and the rhizosphere of healthy and dieback-affected koa stands. The purpose of this study was to characterize the stand structure, soil conditions, and physiological condition of dieback-affected trees, and to assess the possible role of F. oxysporum f. sp. koae in the current dieback stands. This fungus was isolated from branches of symptomatic koa in dieback-affected stands and roots from healthy and dieback-affected stands. Possible differences in the pathogenicity and virulence of F. oxysporum f. sp. koae isolates obtained from the roots of healthy koa in unaffected stands and those from branches of dieback-affected koa were determined by greenhouse inoculations of koa seedlings. Healthy koa saplings in stands unaffected by dieback were also inoculated to determine if disease symptoms could be induced by inoculation of injured roots in the field. Both branch and root isolates were pathogenic; with the percent mortality of inoculated seedlings ranging from 30 to 60% for all isolates. Disease severity between branch and root isolates was not significantly different. Wilt symptoms were not observed in field inoculations of koa saplings after 8 months. Investigation of the dieback stand structure determined that the larger size classes (i.e., DBH > 3 cm) were all affected equally, with the smallest size class (i.e., 0-3 cm DBH) having the lowest percentage of dieback at each site. Soil from dieback stands had higher water content and was more acidic than that from neighboring unaffected stands. Phyllodes on epicormic shoots of dieback trees had a reduced area, mass, and mass to area ratio. Phyllodes on dieback trees also had reduced stomatal conductance and higher (less negative) leaf water potential. Results from the greenhouse inoculations demonstrated that F. oxysporum f. sp. koae is pathogenic to koa, but the pathogen's activity in the field may be influenced by predisposing factors such as temperature fluctuations, water availability, soil type, and interactions with other soil organisms. F. oxysporum f. sp. koae appears to play an important role in regulating koa stand dynamics, growth, and physiology under environmental and edaphic conditions favorable for disease development. ?? 2002 Elsevier Science B.V. All rights reserved.

Annual changes in bioactive contents and production in field-grown blackberry after inoculation with Pseudomonas fluorescens.

PubMed

Ramos-Solano, B; Garcia-Villaraco, A; Gutierrez-Mañero, F J; Lucas, J A; Bonilla, A; Garcia-Seco, D

2014-01-01

The aim of this study was two-fold: first, to characterize blackberry fruits from Rubus sp. var. Lochness along the year, and secondly, to evaluate the ability of a Pseudomonas strain (N21.4) to improve fruit yield and quality under field conditions in production greenhouses throughout the year. The strain was root or leaf inoculated to blackberry plants and fruits were harvested in each season. Nutritional parameters, antioxidant potential and bioactive contents were determined; total fruit yield was recorded. Blackberries grown under short day conditions (autumn and winter) showed significantly lower °Brix values than fruits grown under long day conditions. Interestingly, an increase in fruit °Brix, relevant for quality, was detected after bacterial challenge, together with significant and sustained increases in total phenolics and flavonoids. Improvements in inoculated fruits were more evident from October through early March, when environmental conditions are worse. In summary, N21.4 is an effective agent to increase fruit quality and production along the year in blackberry; this is an environmentally friendly approach to increase fruit quality. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Interactions between accumulation of trace elements and major nutrients in Salix caprea after inoculation with rhizosphere microorganisms

PubMed Central

De Maria, Susanna; Rivelli, Anna Rita; Kuffner, Melanie; Sessitsch, Angela; Wenzel, Walter W.; Gorfer, Markus; Strauss, Joseph; Puschenreiter, Markus

2015-01-01

Although the beneficial effects on growth and trace element accumulation in Salix inoculated with microbes are well known, little information is available on the interactions among trace elements and major nutrients. The main purpose of this study was to assess the effect of inoculation with rhizobacteria Agromyces sp. AR33, Streptomyces sp. AR17, and the combination of each of them with the fungus Cadophora finlandica PRF15 on biomass production and the accumulation of selected trace elements and major nutrients (Cd, Zn, Fe, Ca, K and Mg) in Salix caprea grown on a moderately polluted soil. Dry matter production was significantly enhanced only upon inoculation with Agromyces AR33. Microbial treatments differently affected the accumulation of Zn and Cd in plants. Both the inoculation with Streptomyces AR17 and the co-inoculation of C. finlandica with Agromyces AR33 were most efficient in enhancing the accumulation of Zn and Cd in leaves. These two treatments showed also a higher translocation factor from roots to the leaves for both Cd and Zn. Concentrations of major nutrients in shoots were generally increased in the treatments with the fungus compared to those without, except for K in plants inoculated with bacterial strain Streptomyces AR17. Co-inoculation of C. finlandica plus Agromyces AR33 resulted in a better accumulation of both Zn and Cd and Ca, K and Mg in shoots. This study suggests that the phytoextraction of Zn and Cd can be improved by inoculation with selected microbial strains. PMID:21612812

Growth of Quailbush in Acidic, Metalliferous Desert Mine Tailings: Effect of Azospirillum brasilense Sp6 on Biomass Production and Rhizosphere Community Structure

PubMed Central

de-Bashan, Luz E.; Hernandez, Juan-Pablo; Nelson, Karis N.; Bashan, Yoav

2010-01-01

Mine tailing deposits in semiarid and arid environments frequently remain devoid of vegetation due to the toxicity of the substrate and the absence of a diverse soil microbial community capable of supporting seed germination and plant growth. The contribution of the plant growth promoting bacterium (PGPB) Azospirillum brasilense Sp6 to the growth of quailbush in compost-amended, moderately acidic, high-metal content mine tailings using an irrigation-based reclamation strategy was examined along with its influence on the rhizosphere bacterial community. Sp6 inoculation resulted in a significant (2.2-fold) increase in plant biomass production. The data suggest that the inoculum successfully colonized the root surface and persisted throughout the 60-day experiment in both the rhizosphere, as demonstrated by excision and sequencing of the appropriate denaturing gradient gel electrophoresis (DGGE) band, and the rhizoplane, as indicated by fluorescent in situ hybridization of root surfaces. Changes in rhizosphere community structure in response to Sp6 inoculation were evaluated after 15, 30, and 60 days using DGGE analysis of 16S rRNA polymerase chain reaction amplicons. A comparison of DGGE profiles using canonical correspondence analysis revealed a significant treatment effect (Sp6-inoculated vs. uninoculated plants vs. unplanted) on bacterial community structure at 15, 30, and 60 days (p<0.05). These data indicate that in an extremely stressed environment such as acid mine tailings, an inoculated plant growth promoting bacterium not only can persist and stimulate plant growth but also can directly or indirectly influence rhizobacterial community development. PMID:20632001

Inoculating plants with the endophytic bacterium Pseudomonas sp. Ph6-gfp to reduce phenanthrene contamination.

PubMed

Sun, Kai; Liu, Juan; Gao, Yanzheng; Sheng, Yuehui; Kang, Fuxing; Waigi, Michael Gatheru

2015-12-01

Plant organic contamination poses a serious threat to the safety of agricultural products and human health worldwide, and the association of endophytic bacteria with host plants may decrease organic pollutants in planta. In this study, we firstly determined the growth response and biofilm formation of endophytic Pseudomonas sp. Ph6-gfp, and then systematically evaluated the performance of different plant colonization methods (seed soaking (SS), root soaking (RS), leaf painting (LP)) for circumventing the risk of plant phenanthrene (PHE) contamination. After inoculation for 48 h, strain Ph6-gfp grew efficiently with PHE, oxalic acid, or malic acid as the sole sources of carbon and energy. Moreover, strain Ph6-gfp could form robust biofilms in LB medium. In greenhouse hydroponic experiments, strain Ph6-gfp could actively colonize inoculated plants internally, and plants colonized with Ph6-gfp showed a higher capacity for PHE removal. Compared with the Ph6-gfp-free treatment, the accumulations of PHE in Ph6-gfp-colonized plants via SS, RS, and LP were 20.1, 33.1, and 7.1 %, respectively, lower. Our results indicate that inoculating plants with Ph6-gfp could lower the risk of plant PHE contamination. RS was most efficient for improving PHE removal in whole plant bodies by increasing the cell numbers of Ph6-gfp in plant roots. The findings in this study provide an optimized method to strain Ph6-gfp reduce plant PAH residues, which may be applied to agricultural production in PAH-contaminated soil.

Evaluation of Clonostachys rosea for Control of Plant-Parasitic Nematodes in Soil and in Roots of Carrot and Wheat.

PubMed

Iqbal, Mudassir; Dubey, Mukesh; McEwan, Kerstin; Menzel, Uwe; Franko, Mikael Andersson; Viketoft, Maria; Jensen, Dan Funck; Karlsson, Magnus

2018-01-01

Biological control is a promising approach to reduce plant diseases caused by nematodes. We tested the effect of the fungus Clonostachys rosea strain IK726 inoculation on nematode community composition in a naturally nematode infested soil in a pot experiment, and the effect of C. rosea on plant health. The numbers of plant-parasitic nematode genera extracted from soil and plant roots decreased by 40 to 73% when C. rosea was applied, while genera of nonparasitic nematodes were not affected. Soil inoculation of C. rosea increased fresh shoot weight and shoot length of wheat plants by 20 and 24%, respectively, while only shoot dry weight increased by 48% in carrots. Light microscopy of in vitro C. rosea-nematode interactions did not reveal evidence of direct parasitism. However, culture filtrates of C. rosea growing in potato dextrose broth, malt extract broth and synthetic nutrient broth exhibited toxicity toward nematodes and immobilized 57, 62, and 100% of the nematodes, respectively, within 48 h. This study demonstrates that C. rosea can control plant-parasitic nematodes and thereby improve plant growth. The most likely mechanism responsible for the antagonism is antibiosis through production of nematicidal compounds, rather than direct parasitism.

Arbuscular mycorrhizal fungi and rhizobium facilitate nitrogen uptake and transfer in soybean/maize intercropping system

PubMed Central

Meng, Lingbo; Zhang, Aiyuan; Wang, Fei; Han, Xiaoguang; Wang, Dejiang; Li, Shumin

2015-01-01

The tripartite symbiosis between legumes, rhizobia and mycorrhizal fungi are generally considered to be beneficial for the nitrogen (N) uptake of legumes, but the facilitation of symbiosis in legume/non-legume intercropping systems is not clear. Therefore, the aims of the research are as follows: (1) to verify if the dual inoculation can facilitate the N uptake and N transfer in maize/soybean intercropping systems and (2) to calculate how much N will be transferred from soybean to maize. A pot experiment with different root separations [solid barrier, mesh (30 μm) barrier and no barrier] was conducted, and the 15N isotopic tracing method was used to calculate how much N transferred from soybean to maize inoculated with arbuscular mycorrhizal fungi (AMF) and rhizobium in a soybean (Glycine max L.cv. Dongnong No. 42)/maize (Zea mays L.cv. Dongnong No. 48) intercropping system. Compared with the Glomus mosseae inoculation (G.m.), Rhizobium SH212 inoculation (SH212), no inoculation (NI), the dual inoculation (SH212+G.m.) increased the N uptake of soybean by 28.69, 39.58, and 93.07% in a solid barrier system. N uptake of maize inoculated with both G. mosseae and rhizobium was 1.20, 1.28, and 1.68 times more than that of G.m., SH212 and NI, respectively, in solid barrier treatments. In addition, the amount of N transferred from soybean to maize in a dual inoculation system with a mesh barrier was 7.25, 7.01, and 11.45 mg more than that of G.m., SH212 and NI and similarly, 6.40, 7.58, and 12.46 mg increased in no barrier treatments. Inoculating with both AMF and rhizobium in the soybean/maize intercropping system improved the N fixation efficiency of soybean and promoted N transfer from soybean to maize, resulting in the improvement of yield advantages of legume/non-legume intercropping. PMID:26029236

Arbuscular mycorrhizal fungi and rhizobium facilitate nitrogen uptake and transfer in soybean/maize intercropping system.

PubMed

Meng, Lingbo; Zhang, Aiyuan; Wang, Fei; Han, Xiaoguang; Wang, Dejiang; Li, Shumin

2015-01-01

The tripartite symbiosis between legumes, rhizobia and mycorrhizal fungi are generally considered to be beneficial for the nitrogen (N) uptake of legumes, but the facilitation of symbiosis in legume/non-legume intercropping systems is not clear. Therefore, the aims of the research are as follows: (1) to verify if the dual inoculation can facilitate the N uptake and N transfer in maize/soybean intercropping systems and (2) to calculate how much N will be transferred from soybean to maize. A pot experiment with different root separations [solid barrier, mesh (30 μm) barrier and no barrier] was conducted, and the (15)N isotopic tracing method was used to calculate how much N transferred from soybean to maize inoculated with arbuscular mycorrhizal fungi (AMF) and rhizobium in a soybean (Glycine max L.cv. Dongnong No. 42)/maize (Zea mays L.cv. Dongnong No. 48) intercropping system. Compared with the Glomus mosseae inoculation (G.m.), Rhizobium SH212 inoculation (SH212), no inoculation (NI), the dual inoculation (SH212+G.m.) increased the N uptake of soybean by 28.69, 39.58, and 93.07% in a solid barrier system. N uptake of maize inoculated with both G. mosseae and rhizobium was 1.20, 1.28, and 1.68 times more than that of G.m., SH212 and NI, respectively, in solid barrier treatments. In addition, the amount of N transferred from soybean to maize in a dual inoculation system with a mesh barrier was 7.25, 7.01, and 11.45 mg more than that of G.m., SH212 and NI and similarly, 6.40, 7.58, and 12.46 mg increased in no barrier treatments. Inoculating with both AMF and rhizobium in the soybean/maize intercropping system improved the N fixation efficiency of soybean and promoted N transfer from soybean to maize, resulting in the improvement of yield advantages of legume/non-legume intercropping.

Inoculation with arbuscular mycorrhizae does not improve 137Cs uptake in crops grown in the Chernobyl region.

PubMed

Vinichuk, M; Mårtensson, A; Rosén, K

2013-12-01

Methods for cleaning up radioactive contaminated soils are urgently needed. In this study we investigated whether the use of arbuscular mycorrhizal (AM) fungi can improve (137)Cs uptake by crops. Barley, cucumber, perennial ryegrass, and sunflower were inoculated with AM fungi and grown in low-level radionuclide contaminated soils in a field experiment 70 km southwest of Chernobyl, Ukraine, during two successive years (2009-2010). Roots of barley, cucumber and sunflower plants were slightly or moderately infected with AM fungus and root infection frequency was negatively or non-correlated with (137)Cs uptake by plants. Roots of ryegrass were moderately infected with AM fungus and infection frequency was moderately correlated with (137)Cs uptake by ryegrass. The application of AM fungi to soil in situ did not enhance radionuclide plant uptake or biomass. The responsiveness of host plants and AM fungus combination to (137)Cs uptake varied depending on the soil, although mycorrhization of soil in the field was conditional and did not facilitate the uptake of radiocesium. The total amount of (137)Cs uptake by plants growing on inoculated soil was equal to amounts in plant cultivated on non-inoculated soil. Thus, the use of AM fungi in situ for bioremediation of soil contaminated with a low concentration of (137)Cs could not be recommended. Copyright © 2013 Elsevier Ltd. All rights reserved.

Intraspecific ploidy variation: A hidden, minor player in plant-soil-mycorrhizal fungi interactions.

PubMed

Sudová, Radka; Pánková, Hana; Rydlová, Jana; Münzbergová, Zuzana; Suda, Jan

2014-01-01

Genome duplication and arbuscular mycorrhizal (AM) symbiosis are ubiquitous in angiosperms. While the significance of each of these phenomena separately has been intensively studied, their interaction remains to be understood. Three diploid and three hexaploid populations of Aster amellus (Asteraceae) were characterized in terms of the soil conditions in situ and mycorrhizal root colonization. In a greenhouse experiment, the effects of ploidy level, substrate conditions, and AM fungi on plant performance were then separated by growing noninoculated plants or plants inoculated with AM fungi in substrates native to either the diploids or hexaploids. The diploids inhabited nutritionally richer sites but did not differ from hexaploid plants in the level of mycorrhizal root colonization in situ. In the experiment, hexaploids generally performed better than the diploids. This intercytotype growth difference was enhanced by soil fertility, with hexaploids benefiting more from nutritionally richer substrate than the diploids. AM inoculation was crucial for plant growth and phosphorus uptake. The interaction between ploidy level and AM inoculation significantly influenced only dry mass of roots, phosphorus concentrations in shoot biomass, and the length of the extraradical mycelium in the nonsterile substrates. Our results support the idea that polyploidy can affect the mycorrhizal growth response of host plants. Nevertheless, the effects of the interaction between ploidy and inoculation were weaker than the main effects of these factors.

Quantification of Azospirillum brasilense FP2 Bacteria in Wheat Roots by Strain-Specific Quantitative PCR.

PubMed

Stets, Maria Isabel; Alqueres, Sylvia Maria Campbell; Souza, Emanuel Maltempi; Pedrosa, Fábio de Oliveira; Schmid, Michael; Hartmann, Anton; Cruz, Leonardo Magalhães

2015-10-01

Azospirillum is a rhizobacterial genus containing plant growth-promoting species associated with different crops worldwide. Azospirillum brasilense strains exhibit a growth-promoting effect by means of phytohormone production and possibly by N2 fixation. However, one of the most important factors for achieving an increase in crop yield by plant growth-promoting rhizobacteria is the survival of the inoculant in the rhizosphere, which is not always achieved. The objective of this study was to develop quantitative PCR protocols for the strain-specific quantification of A. brasilense FP2. A novel approach was applied to identify strain-specific DNA sequences based on a comparison of the genomic sequences within the same species. The draft genome sequences of A. brasilense FP2 and Sp245 were aligned, and FP2-specific regions were filtered and checked for other possible matches in public databases. Strain-specific regions were then selected to design and evaluate strain-specific primer pairs. The primer pairs AzoR2.1, AzoR2.2, AzoR5.1, AzoR5.2, and AzoR5.3 were specific for the A. brasilense FP2 strain. These primer pairs were used to monitor quantitatively the population of A. brasilense in wheat roots under sterile and nonsterile growth conditions. In addition, coinoculations with other plant growth-promoting bacteria in wheat were performed under nonsterile conditions. The results showed that A. brasilense FP2 inoculated into wheat roots is highly competitive and achieves high cell numbers (∼10(7) CFU/g [fresh weight] of root) in the rhizosphere even under nonsterile conditions and when coinoculated with other rhizobacteria, maintaining the population at rather stable levels for at least up to 13 days after inoculation. The strategy used here can be applied to other organisms whose genome sequences are available. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Quantification of Azospirillum brasilense FP2 Bacteria in Wheat Roots by Strain-Specific Quantitative PCR

PubMed Central

Stets, Maria Isabel; Alqueres, Sylvia Maria Campbell; Souza, Emanuel Maltempi; Pedrosa, Fábio de Oliveira; Schmid, Michael

2015-01-01

Azospirillum is a rhizobacterial genus containing plant growth-promoting species associated with different crops worldwide. Azospirillum brasilense strains exhibit a growth-promoting effect by means of phytohormone production and possibly by N2 fixation. However, one of the most important factors for achieving an increase in crop yield by plant growth-promoting rhizobacteria is the survival of the inoculant in the rhizosphere, which is not always achieved. The objective of this study was to develop quantitative PCR protocols for the strain-specific quantification of A. brasilense FP2. A novel approach was applied to identify strain-specific DNA sequences based on a comparison of the genomic sequences within the same species. The draft genome sequences of A. brasilense FP2 and Sp245 were aligned, and FP2-specific regions were filtered and checked for other possible matches in public databases. Strain-specific regions were then selected to design and evaluate strain-specific primer pairs. The primer pairs AzoR2.1, AzoR2.2, AzoR5.1, AzoR5.2, and AzoR5.3 were specific for the A. brasilense FP2 strain. These primer pairs were used to monitor quantitatively the population of A. brasilense in wheat roots under sterile and nonsterile growth conditions. In addition, coinoculations with other plant growth-promoting bacteria in wheat were performed under nonsterile conditions. The results showed that A. brasilense FP2 inoculated into wheat roots is highly competitive and achieves high cell numbers (∼107 CFU/g [fresh weight] of root) in the rhizosphere even under nonsterile conditions and when coinoculated with other rhizobacteria, maintaining the population at rather stable levels for at least up to 13 days after inoculation. The strategy used here can be applied to other organisms whose genome sequences are available. PMID:26187960

The Phenylpropanoid Pathway and Lignin in Defense against Ganoderma boninense Colonized Root Tissues in Oil Palm (Elaeis guineensis Jacq.)

PubMed Central

Govender, Nisha T.; Mahmood, Maziah; Seman, Idris A.; Wong, Mui-Yun

2017-01-01

Basal stem rot, caused by the basidiomycete fungus, Ganoderma boninense, is an economically devastating disease in Malaysia. Our study investigated the changes in lignin content and composition along with activity and expression of the phenylpropanoid pathway enzymes and genes in oil palm root tissues during G. boninense infection. We sampled control (non-inoculated) and infected (inoculated) seedlings at seven time points [1, 2, 3, 4, 8, and 12 weeks post-inoculation (wpi)] in a randomized design. The expression profiles of phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) genes were monitored at 1, 2, and 3 wpi using real-time quantitative polymerase chain reaction. Seedlings at 4, 8, and 12 wpi were screened for lignin content, lignin composition, enzyme activities (PAL, CAD, and POD), growth (weight and height), and disease severity (DS). Gene expression analysis demonstrated up-regulation of PAL, CAD, and POD genes in the infected seedlings, relative to the control seedlings at 1, 2, and 3 wpi. At 2 and 3 wpi, CAD showed highest transcript levels compared to PAL and POD. DS increased progressively throughout sampling, with 5, 34, and 69% at 4, 8, and 12 wpi, respectively. Fresh weight and height of the infected seedlings were significantly lower compared to the control seedlings at 8 and 12 wpi. Lignin content of the infected seedlings at 4 wpi was significantly higher than the control seedlings, remained elicited with no change at 8 wpi, and then collapsed with a significant reduction at 12 wpi. The nitrobenzene oxidation products of oil palm root lignin yielded both syringyl and guaiacyl monomers. Accumulation of lignin in the infected seedlings was in parallel to increased syringyl monomers, at 4 and 8 wpi. The activities of PAL and CAD enzymes in the infected seedlings at DS = 5–34% were significantly higher than the control seedlings and thereafter collapsed at DS = 69%. PMID:28861093

The Phenylpropanoid Pathway and Lignin in Defense against Ganoderma boninense Colonized Root Tissues in Oil Palm (Elaeis guineensis Jacq.).

PubMed

Govender, Nisha T; Mahmood, Maziah; Seman, Idris A; Wong, Mui-Yun

2017-01-01

Basal stem rot, caused by the basidiomycete fungus, Ganoderma boninense , is an economically devastating disease in Malaysia. Our study investigated the changes in lignin content and composition along with activity and expression of the phenylpropanoid pathway enzymes and genes in oil palm root tissues during G. boninense infection. We sampled control (non-inoculated) and infected (inoculated) seedlings at seven time points [1, 2, 3, 4, 8, and 12 weeks post-inoculation (wpi)] in a randomized design. The expression profiles of phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) genes were monitored at 1, 2, and 3 wpi using real-time quantitative polymerase chain reaction. Seedlings at 4, 8, and 12 wpi were screened for lignin content, lignin composition, enzyme activities (PAL, CAD, and POD), growth (weight and height), and disease severity (DS). Gene expression analysis demonstrated up-regulation of PAL, CAD, and POD genes in the infected seedlings, relative to the control seedlings at 1, 2, and 3 wpi. At 2 and 3 wpi, CAD showed highest transcript levels compared to PAL and POD. DS increased progressively throughout sampling, with 5, 34, and 69% at 4, 8, and 12 wpi, respectively. Fresh weight and height of the infected seedlings were significantly lower compared to the control seedlings at 8 and 12 wpi. Lignin content of the infected seedlings at 4 wpi was significantly higher than the control seedlings, remained elicited with no change at 8 wpi, and then collapsed with a significant reduction at 12 wpi. The nitrobenzene oxidation products of oil palm root lignin yielded both syringyl and guaiacyl monomers. Accumulation of lignin in the infected seedlings was in parallel to increased syringyl monomers, at 4 and 8 wpi. The activities of PAL and CAD enzymes in the infected seedlings at DS = 5-34% were significantly higher than the control seedlings and thereafter collapsed at DS = 69%.

Local and systemic mycorrhiza-induced protection against the ectoparasitic nematode Xiphinema index involves priming of defence gene responses in grapevine.

PubMed

Hao, Zhipeng; Fayolle, Léon; van Tuinen, Diederik; Chatagnier, Odile; Li, Xiaolin; Gianinazzi, Silvio; Gianinazzi-Pearson, Vivienne

2012-06-01

The ectoparasitic dagger nematode (Xiphinema index), vector of Grapevine fanleaf virus (GFLV), provokes gall formation and can cause severe damage to the root system of grapevines. Mycorrhiza formation by Glomus (syn. Rhizophagus) intraradices BEG141 reduced both gall formation on roots of the grapevine rootstock SO4 (Vitis berlandieri×V. riparia) and nematode number in the surrounding soil. Suppressive effects increased with time and were greater when the nematode was post-inoculated rather than co-inoculated with the arbuscular mycorrhizal (AM) fungus. Using a split-root system, decreased X. index development was shown in mycorrhizal and non-mycorrhizal parts of mycorrhizal root systems, indicating that both local and systemic induced bioprotection mechanisms were active against the ectoparasitic nematode. Expression analyses of ESTs (expressed sequence tags) generated in an SSH (subtractive suppressive hybridization) library, representing plant genes up-regulated during mycorrhiza-induced control of X. index, and of described grapevine defence genes showed activation of chitinase 1b, pathogenesis-related 10, glutathione S-transferase, stilbene synthase 1, 5-enolpyruvyl shikimate-3-phosphate synthase, and a heat shock proein 70-interacting protein in association with the observed local and/or systemic induced bioprotection against the nematode. Overall, the data suggest priming of grapevine defence responses by the AM fungus and transmission of a plant-mediated signal to non-mycorrhizal tissues. Grapevine gene responses during AM-induced local and systemic bioprotection against X. index point to biological processes that are related either to direct effects on the nematode or to protection against nematode-imposed stress to maintain root tissue integrity.

Use of sucrose-agar globule with root exudates for mass production of vesicular arbuscular mycorrhizal fungi.

PubMed

Selvaraj, Thangaswamy; Kim, Hoon

2004-03-01

A sucrose-agar globule (SAG) was newly introduced to increase production of the vesicular arbuscular mycorrhizal (VAM) fungal spores, Gigaspora gigantea and Glomus fasciculatum. An SAG inoculum and a sucrose-agar globule with root exudates (SAGE) inoculum were prepared, and their spore productions were compared with a soil inoculum. When the SAGE was used as the inoculum on sucrose-agar medium plates the number of spores was increased (35% more than the soil inoculum). After the soil inoculum and SAGE were inoculated on an experimental plant, Zingiber officinale, the percentage root colonization, number of VAM spores, and dry matter content were analyzed. It was observed that the SAGE showed a higher percentage of root colonization (about 10% more), and increases in the number of spores (about 26%) and dry matter (more than 13%) for the two VAM fungal spores than the soil inoculum. The results of this study suggested that the SAGE inoculum may be useful for the mass production of VAM fungi and also for the large scale production of VAM fungal fertilizer.

[Identification of two Fusarium isolates and their crude toxin allelopathic effect on Cucumis melo seedlings].

PubMed

Zhao, Juan; Xue, Quan-Hong; Du, Jun-Zhi; Chen, Jiao-Jiao

2013-01-01

Eight fungi isolates were obtained from Fusarium-infected Cucumis melo (melon) plants and their rhizosphere soils. Taking melon cultivar 'Xitian 1' as test material, the re-inoculation and seed germination experiments were conducted to investigate the pathogenicity and growth inhibition effect of these fungi isolates on melon. Through the determination of the induced enzyme activities, resistant substance contents, and cell membrane permeability of potted melon roots, the allelopathic effect of the crude toxins of two harmful fungi was studied, and according to the morphological characteristics and Internal Transcribed Spacer (ITS) sequencing, the two harmful fungi were identified. The crude toxins of the two harmful fungi TF and HF had strong inhibition effects on the germination and growth of the melon seeds. The MDA and soluble protein contents and the cell membrane permeability of the 'Xitian 1' seedlings roots all increased, among which, the MDA content and cell membrane permeability increased by 108.6% and 40.6%, respectively when treated with the stock solution of TF toxin, compared with the control. The crude toxins of the two harmful fungi improved the induced enzyme activities of the melon roots, with the increment of the PAL and POD activities under the treatment of 10-fold dilution of TF crude toxin increased by 25.6% and 23.2%, respectively. When treated with the stock solution of HF toxin, the PAL activity significantly increased by 30.0%. The two harmful fungi TF and HF were primarily identified as Fusarium equisti and F. proliferatum, respectively. This study showed that the two Fusarium isolates could not infect melon via re-inoculation, but could negatively affect the melon's normal growth and normal physiological and biochemical metabolism via toxins excretion, and in the meantime, improve the root protective enzyme activities, with the effects of both benefit and harmfulness on melon plants. The allelopathic hazard of the crude toxins of the isolates could be one of the main causes of continuous cropping obstacle of melon.

Gentiana dinarica Beck hairy root cultures and evaluation of factors affecting growth and xanthone production

USDA-ARS?s Scientific Manuscript database

The induction and establishment of hairy root cultures of Gentiana dinarica using two strains of Agrobacterium rhizogenes (A4M70GUS and 15834/PI) is reported for the first time. Hairy roots were formed from the shoots 25 days after inoculation, and strain 15834/PI had higher induction rate of hairy ...

INFLUENCE OF ROOT COLONIZING BACTERIA ON THE DEFENSE RESPONSES OF BEAN

EPA Science Inventory

Colonization of plant roots by fluorescent pseudomonads has been correlated with disease suppression. ne mechanism may involve altered defense responses in the plant upon colonization. ltered defense responses were observed in bean (Phaseolus vulgaris) inoculated with fluorescent...

The effect of ectomycorrhizal fungi forming symbiosis with Pinus pinaster seedlings exposed to cadmium.

PubMed

Sousa, Nadine R; Ramos, Miguel A; Marques, Ana P G C; Castro, Paula M L

2012-01-01

Cadmium is one of the most toxic heavy metals and its accumulation in the upper layers of forest soils affects plants, microorganisms and their interactions. Adequate strategies for the reforestation of metal contaminated sites are of vital importance. The aim of this work was to evaluate the response of Pinus pinaster seedlings to Cd exposure and to assess the effect of inoculation with two selected ectomycorrhizal fungi, Suillus bovinus and Rhizopogon roseolus on that response. Seedlings were exposed to soil contaminated at 15 and 30 mg Cd kg(-1). Shoot biomass of P. pinaster decreased ca. 36% when exposed to 15 mg Cd kg(-1). Overall, colonization by S. bovinus significantly enhanced shoot development up to 30% in contaminated soil while colonization by R. roseolus produced no significant effect at both Cd concentrations tested and significantly increased the level of Cd in the shoots at both Cd concentrations. Metal accumulation in the shoots and roots of non-inoculated and S. bovinus-inoculated seedlings increased at the higher Cd levels whereas R. roseolus-inoculated seedlings were not sensitive to Cd variation in the soil. The results from our research show that inoculation with ECM fungi has a significant impact on metal uptake and development of P. pinaster seedlings; the differential response induced by the two tested species highlights the importance of selecting the appropriate strains for nursery inoculation, and, as such, this biological tool ought to be considered in reforestation processes of heavy metal contaminated areas by woody species. Copyright © 2011 Elsevier B.V. All rights reserved.

Oxidative and antioxidative responses in the wheat-Azospirillum brasilense interaction.

PubMed

Méndez-Gómez, Manuel; Castro-Mercado, Elda; Alexandre, Gladys; García-Pineda, Ernesto

2016-03-01

Azospirillum is a plant growth-promoting rhizobacteria (PGPR) able to enhance the growth of wheat. The aim of this study was to test the effect of Azospirillum brasilense cell wall components on superoxide (O2·(-)) production in wheat roots and the effect of oxidative stress on A. brasilense viability. We found that inoculation with A. brasilense reduced O2·(-) levels by approx. 30 % in wheat roots. Inoculation of wheat with papain-treated A. brasilense, a Cys protease, notably increased O2·(-) production in all root tissues, as was observed by the nitro blue tetrazolium (NBT) reduction. However, a 24-h treatment with rhizobacteria lipopolysaccharides (50 and 100 μg/mL) alone did not affect the pattern of O2·(-) production. Analysis of the effect of plant cell wall components on A. brasilense oxidative enzyme activity showed no changes in catalase activity but a decrease in superoxide dismutase activity in response to polygalacturonic acid treatment. Furthermore, A. brasilense growth was only affected by high concentrations of H2O2 or paraquat, but not by sodium nitroprusside. Our results suggest that rhizobacterial cell wall components play an important role in controlling plant cell responses and developing tolerance of A. brasilense to oxidative stress produced by the plant.

Effector-Triggered Immunity Determines Host Genotype-Specific Incompatibility in Legume-Rhizobium Symbiosis.

PubMed

Yasuda, Michiko; Miwa, Hiroki; Masuda, Sachiko; Takebayashi, Yumiko; Sakakibara, Hitoshi; Okazaki, Shin

2016-08-01

Symbiosis between legumes and rhizobia leads to the formation of N2-fixing root nodules. In soybean, several host genes, referred to as Rj genes, control nodulation. Soybean cultivars carrying the Rj4 gene restrict nodulation by specific rhizobia such as Bradyrhizobium elkanii We previously reported that the restriction of nodulation was caused by B. elkanii possessing a functional type III secretion system (T3SS), which is known for its delivery of virulence factors by pathogenic bacteria. In the present study, we investigated the molecular basis for the T3SS-dependent nodulation restriction in Rj4 soybean. Inoculation tests revealed that soybean cultivar BARC-2 (Rj4/Rj4) restricted nodulation by B. elkanii USDA61, whereas its nearly isogenic line BARC-3 (rj4/rj4) formed nitrogen-fixing nodules with the same strain. Root-hair curling and infection threads were not observed in the roots of BARC-2 inoculated with USDA61, indicating that Rj4 blocked B. elkanii infection in the early stages. Accumulation of H2O2 and salicylic acid (SA) was observed in the roots of BARC-2 inoculated with USDA61. Transcriptome analyses revealed that inoculation of USDA61, but not its T3SS mutant in BARC-2, induced defense-related genes, including those coding for hypersensitive-induced responsive protein, which act in effector-triggered immunity (ETI) in Arabidopsis. These findings suggest that B. elkanii T3SS triggers the SA-mediated ETI-type response in Rj4 soybean, which consequently blocks symbiotic interactions. This study revealed a common molecular mechanism underlying both plant-pathogen and plant-symbiont interactions, and suggests that establishment of a root nodule symbiosis requires the evasion or suppression of plant immune responses triggered by rhizobial effectors. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Interactions of Heterodera daverti, H. goldeni and H. zeae with Meloidogyne incognita on rice

USDA-ARS?s Scientific Manuscript database

The interactions of the cyst nematodes Heterodera daverti, H. goldeni and H. zeae with the root-knot nematode Meloidogyne incognita on rice (Oryza sativa) cultivars Giza 178 and Sakha 101 were studied in the greenhouse. Inoculation with H. goldeni alone or one week before inoculation with M. incogni...

Toxin distribution and sphingoid base imbalances in Fusarium verticillioides-infected and fumonisin B1-watered maize seedlings.

PubMed

Arias, Silvina L; Mary, Verónica S; Otaiza, Santiago N; Wunderlin, Daniel A; Rubinstein, Héctor R; Theumer, Martín G

2016-05-01

Fusarium verticillioides is a major maize pathogen and there are susceptible and resistant cultivars to this fungal infection. Recent studies suggest that its main mycotoxin fumonisin B1 (FB1) may be involved in phytopathogenicity, but the underlying mechanisms are mostly still unknown. This work was aimed at assessing whether FB1 disseminates inside the plants, as well as identifying possible correlations between the maize resistant/susceptible phenotype and the unbalances of the FB1-structurally-related sphingoid base sphinganine (Sa) and phytosphingosine (Pso) due to toxin accumulation. Resistant (RH) and susceptible hybrid (SH) maize seedlings grown from seeds inoculated with a FB1-producer F. verticillioides and from uninoculated ones irrigated with FB1 (20 ppm), were harvested at 7, 14 and 21 days after planting (dap), and the FB1, Sa and Pso levels were quantified in roots and aerial parts. The toxin was detected in roots and aerial parts for inoculated and FB1-irrigated plants of both hybrids. However, FB1 levels were overall higher in SH seedlings regardless of the treatment (infection or watering). Sa levels increased substantially in RH lines, peaking at 54-fold in infected roots at 14 dap. In contrast, the main change observed in SH seedlings was an increase of Pso in infected roots at 7 dap. Here, it was found that FB1 disseminates inside seedlings in the absence of FB1-producer fungal infections, perhaps indicating this might condition the fungus-plant interaction before the first contact. Furthermore, the results strongly suggest the existence of at least two ceramide synthase isoforms in maize with different substrate specificities, whose differential expression after FB1 exposure could be closely related to the susceptibility/resistance to F. verticillioides. Copyright © 2016 Elsevier Ltd. All rights reserved.

Improvement of phytoremediation of an aged petroleum hydrocarbon-contaminated soil by Rhodococcus erythropolis CD 106 strain.

PubMed

Płociniczak, Tomasz; Fic, Ewa; Pacwa-Płociniczak, Magdalena; Pawlik, Małgorzata; Piotrowska-Seget, Zofia

2017-07-03

The aim of this study was to assess the impact of soil inoculation with the Rhodococcus erythropolis CD 106 strain on the effectiveness of the phytoremediation of an aged hydrocarbon-contaminated [approx. 1% total petroleum hydrocarbon (TPH)] soil using ryegrass (Lolium perenne). The introduction of CD 106 into the soil significantly increased the biomass of ryegrass and the removal of hydrocarbons in planted soil. The fresh weight of the shoots and roots of plants inoculated with CD 106 increased by 49% and 30%, respectively. After 210 days of the experiment, the concentration of TPH was reduced by 31.2%, whereas in the planted, non-inoculated soil, it was reduced by 16.8%. By contrast, the concentration of petroleum hydrocarbon decreased by 18.7% in non-planted soil bioaugmented with the CD 106 strain. The rifampicin-resistant CD 106 strain survived after inoculation into soil and was detected in the soil during the entire experimental period, but the number of CD 106 cells decreased constantly during the enhanced phytoremediation and bioaugmentation experiments. The plant growth-promoting and hydrocarbon-degrading properties of CD 106, which are connected with its long-term survival and limited impact on autochthonous microflora, make this strain a good candidate for improving the phytoremediation efficiency of soil contaminated with hydrocarbons.

Impact of lead tolerant plant growth promoting rhizobacteria on growth, physiology, antioxidant activities, yield and lead content in sunflower in lead contaminated soil.

PubMed

Saleem, Muhammad; Asghar, Hafiz Naeem; Zahir, Zahir Ahmad; Shahid, Muhammad

2018-03-01

Present study was conducted to evaluate the effect of lead tolerant plant growth promoting rhizobacteria (LTPGPR) on growth, physiology, yield, antioxidant activities and lead uptake in sunflower in soil contaminated with lead under pot conditions. Three pre-characterized LTPGP strains (S2 (Pseudomonas gessardii strain BLP141), S5 (Pseudomonas fluorescens A506) and S10 (Pseudomonas fluorescens strain LMG 2189)) were used to inoculate sunflower growing in soil contaminated with different levels (300, 600 and 900 mg kg -1 ) of lead by using lead nitrate salt as source of lead. Treatments were arranged according to completely randomized design with factorial arrangements. At harvesting, data regarding growth attributes (root shoot length, root shoot fresh and dry weights), yield per plant, physiological attributes (Chlorophyll 'a', 'b' and carotenoids content), antioxidant activities (Ascorbate peroxidase, catalase, superoxide dismutase and glutathione reductase), proline and malanodialdehyde content, and lead content in root, shoot and achenes of sunflower were recorded. Data were analysed by standard statistical procedures. Results showed that lead contamination reduced the plants growth, physiology and yield at all levels of lead stress. But application of LTPGPR in soil contaminated with lead improved plant growth, physiology, yield, and antioxidant activities, proline, and reduced the malanodialdehyde content (that is reduced by the application of different strains in lead contamination) of sunflower as compared to plants grown in soil without inoculation. Inoculation also promoted the uptake of lead in root, shoots and reduced the uptake of lead in achenes of plants as compared to plants in lead contamination without inoculation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Inoculation of Soil with Plant Growth Promoting Bacteria Producing 1-Aminocyclopropane-1-Carboxylate Deaminase or Expression of the Corresponding acdS Gene in Transgenic Plants Increases Salinity Tolerance in Camelina sativa

PubMed Central

Heydarian, Zohreh; Yu, Min; Gruber, Margaret; Glick, Bernard R.; Zhou, Rong; Hegedus, Dwayne D.

2016-01-01

Camelina sativa (camelina) is an oilseed crop touted for use on marginal lands; however, it is no more tolerant of soil salinity than traditional crops, such as canola. Plant growth-promoting bacteria (PGPB) that produce 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) facilitate plant growth in the presence of abiotic stresses by reducing stress ethylene. Rhizospheric and endophytic PGPB and the corresponding acdS- mutants of the latter were examined for their ability to enhance tolerance to salt in camelina. Stimulation of growth and tolerance to salt was correlated with ACC deaminase production. Inoculation of soil with wild-type PGPB led to increased shoot length in the absence of salt, and increased seed production by approximately 30–50% under moderately saline conditions. The effect of ACC deaminase was further examined in transgenic camelina expressing a bacterial gene encoding ACC deaminase (acdS) under the regulation of the CaMV 35S promoter or the root-specific rolD promoter. Lines expressing acdS, in particular those using the rolD promoter, showed less decline in root length and weight, increased seed production, better seed quality and higher levels of seed oil production under salt stress. This study clearly demonstrates the potential benefit of using either PGPB that produce ACC deaminase or transgenic plants expressing the acdS gene under the control of a root-specific promoter to facilitate plant growth, seed production and seed quality on land that is not normally suitable for the majority of crops due to high salt content. PMID:28018305

Recovery of soil properties after seedlings Inoculation with AM fungi and addition of composted olive mill waste in the regeneration of a heavy metal polluted environment

NASA Astrophysics Data System (ADS)

curaqueo, Gustavo; Schoebitz, Mauricio; Borie, Fernando; del Mar Alguacil, Maria; Caravaca, Fuensanta; Roldan, Antonio

2014-05-01

A greenhouse experiment was carried out in order to investigate the effects of arbuscular mycorrhizal (AM) fungi inoculation and the use of composted olive waste (COW) on the establishment of Tetraclinis articulata and soil properties in a heavy metal polluted soil. The higher doses of COW in combination with AM fungi increased shoot and root biomass production of T. articulata by 96% and 60% respectively. These treatments trended to improve the soils properties evaluated, highlighting the C compounds and N as well as the microbiological activities. In relation to the metal translocation in T. articulata, doses of COW applied decreased the Cr, Ni and Pb contents in shoot, as well as Cr and As in root, although the most of them reached low levels and far from phytotoxic. The COW amendment aided G-mosseae-inoculated T. articulata plants to thrive in contaminated soil, mainly through an improvement in both nutrients uptake, mainly P and soil microbial function. In addition, the combined use of AM fungi plus COW could be a feasible strategy to be incorporated in phytoremediation programs; because it promotes soil properties, a better performance of plants for supporting the stress in heavy-metal contaminated soils derived from mining process, and also can be a good way for olive mill wastes disposal.

Synergistic use of biochar, compost and plant growth-promoting rhizobacteria for enhancing cucumber growth under water deficit conditions.

PubMed

Nadeem, Sajid M; Imran, Muhammad; Naveed, Muhammad; Khan, Muhammad Y; Ahmad, Maqshoof; Zahir, Zahir A; Crowley, David E

2017-12-01

Limited information is available about the effectiveness of biochar with plant growth-promoting rhizobacteria (PGPR) and compost. A greenhouse study was conducted to evaluate the effect of biochar in combination with compost and PGPR (Pseudomonas fluorescens) for alleviating water deficit stress. Both inoculated and un-inoculated cucumber seeds were sown in soil treated with biochar, compost and biochar + compost. Three water levels - field capacity (D0), 75% field capacity (D1) and 50% field capacity (D2) - were maintained. The results showed that water deficit stress significantly suppressed the growth of cucumber; however, synergistic use of biochar, compost and PGPR mitigated the negative impact of stress. At D2, the synergistic use of biochar, compost and PGPR caused significant increases in shoot length, shoot biomass, root length and root biomass, which were respectively 88, 77, 89 and 74% more than in the un-inoculated control. Significant improvements in chlorophyll and relative water contents as well as reduction in leaf electrolyte leakage demonstrated the effectiveness of this approach. Moreover, the highest population of P. fluorescens was observed where biochar and compost were applied together. These results suggest that application of biochar with PGPR and/or compost could be an effective strategy for enhancing plant growth under stress. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Microbial cooperation in the rhizosphere improves liquorice growth under salt stress

PubMed Central

Egamberdieva, Dilfuza; Wirth, Stephan; Li, Li; Abd-Allah, Elsayed Fathi

2017-01-01

ABSTRACT Liquorice (Glycyrrhiza uralensis Fisch.) is one of the most widely used plants in food production, and it can also be used as an herbal medicine or for reclamation of salt-affected soils. Under salt stress, inhibition of plant growth, nutrient acquisition and symbiotic interactions between the medicinal legume liquorice and rhizobia have been observed. We recently evaluated the interactions between rhizobia and root-colonizing Pseudomonas in liquorice grown in potting soil and observed increased plant biomass, nodule numbers and nitrogen content after combined inoculation compared to plants inoculated with Mesorhizobium alone. Several beneficial effects of microbes on plants have been reported; studies examining the interactions between symbiotic bacteria and root-colonizing Pseudomonas strains under natural saline soil conditions are important, especially in areas where a hindrance of nutrients and niches in the rhizosphere are high. Here, we summarize our recent observations regarding the combined application of rhizobia and Pseudomonas on the growth and nutrient uptake of liquorice as well as the salt stress tolerance mechanisms of liquorice by a mutualistic interaction with microbes. Our observations indicate that microbes living in the rhizosphere of liquorice can form a mutualistic association and coordinate their involvement in plant adaptations to stress tolerance. These results support the development of combined inoculants for improving plant growth and the symbiotic performance of legumes under hostile conditions. PMID:27780398

Influence of arbuscular mycorrhizae on the root system of maize plants under salt stress.

PubMed

Sheng, Min; Tang, Ming; Chen, Hui; Yang, Baowei; Zhang, Fengfeng; Huang, Yanhui

2009-07-01

Salt stress has become a severe global problem, and salinity is one of the most important abiotic factors limiting plant growth and yield. It is known that arbuscular mycorrhizal (AM) fungi decrease plant yield losses under salinity. With the aim of determining whether AM inoculation would give an advantage to root development under salt stress, a greenhouse experiment was carried out with AM or without AM fungi. Maize plants were grown in a sand and soil mixture with 5 NaCl levels (0, 0.5, 1.0, 1.5, and 2.0 g/kg dry substrate) for 55 days, following 15 days of nonsaline pretreatment. At all salt levels, mycorrhizal plants had higher dry shoot and root mass, higher root activity, and lower root to shoot ratios than non-mycorrhizal plants. In salt-free soil, root length, root surface area, root volume, and number of root tips and forks were significantly larger in mycorrhizal plants than in non-mycorrhizal plants, whereas, under salt stress, average root diameter and root volume of mycorrhizal plants were larger than those of non-mycorrhizal plants. Regardless of the NaCl level, mycorrhizal plants had lower specific root length, lower percentage of root length in the 0-0.2 mm diameter class, and higher percentage of root length in both the 0.2-0.4 mm and 0.4-0.6 mm diameter classes, which suggests that the root system shows a significant shift towards a thicker root system when maize plants were inoculated with Glomus mosseae (Nicolson & Gerdemann). The results presented here indicate that the improvements in root activity and the coarse root system of mycorrhizal maize may help in alleviating salt stress on the plant.

Arbuscular Mycorrhiza Alleviates Restrictions to Substrate Water Flow and Delays Transpiration Limitation to Stronger Drought in Tomato

PubMed Central

Bitterlich, Michael; Sandmann, Martin; Graefe, Jan

2018-01-01

Arbuscular mycorrhizal fungi (AMF) proliferate in soil pores, on the surface of soil particles and affect soil structure. Although modifications in substrate moisture retention depend on structure and could influence plant water extraction, mycorrhizal impacts on water retention and hydraulic conductivity were rarely quantified. Hence, we asked whether inoculation with AMF affects substrate water retention, water transport properties and at which drought intensity those factors become limiting for plant transpiration. Solanum lycopersicum plants were set up in the glasshouse, inoculated or not with Funneliformis mosseae, and grown for 35 days under ample water supply. After mycorrhizal establishment, we harvested three sets of plants, one before (36 days after inoculation) and the second (day 42) and third (day 47) within a sequential drying episode. Sampling cores were introduced into pots before planting. After harvest, moisture retention and substrate conductivity properties were assessed and water retention and hydraulic conductivity models were fitted. A root water uptake model was adopted in order to identify the critical substrate moisture that induces soil derived transpiration limitation. Neither substrate porosity nor saturated water contents were affected by inoculation, but both declined after substrates dried. Drying also caused a decline in pot water capacity and hydraulic conductivity. Plant available water contents under wet (pF 1.8–4.2) and dry (pF 2.5–4.2) conditions increased in mycorrhizal substrates and were conserved after drying. Substrate hydraulic conductivity was higher in mycorrhizal pots before and during drought exposure. After withholding water from pots, higher substrate drying rates and lower substrate water potentials were found in mycorrhizal substrates. Mycorrhiza neither affected leaf area nor root weight or length. Consistently with higher substrate drying rates, AMF restored the plant hydraulic status, and increased plant transpiration when soil moisture declined. The water potential at the root surface and the resistance to water flow in the rhizosphere were restored in mycorrhizal pots although the bulk substrate dried more. Finally, substrates colonized by AMF can be more desiccated before substrate water flux quantitatively limits transpiration. This is most pronounced under high transpiration demands and complies with a difference of over 1,000 hPa in substrate water potential. PMID:29503655

Application of Endophytic Pseudomonas fluorescens and a Bacterial Consortium to Brassica napus Can Increase Plant Height and Biomass under Greenhouse and Field Conditions

PubMed Central

Lally, Richard D.; Galbally, Paul; Moreira, António S.; Spink, John; Ryan, David; Germaine, Kieran J.; Dowling, David N.

2017-01-01

Plant associated bacteria with plant growth promotion (PGP) properties have been proposed for use as environmentally friendly biofertilizers for sustainable agriculture; however, analysis of their efficacy in the field is often limited. In this study, greenhouse and field trials were carried out using individual endophytic Pseudomonas fluorescens strains, the well characterized rhizospheric P. fluorescens F113 and an endophytic microbial consortium of 10 different strains. These bacteria had been previously characterized with respect to their PGP properties in vitro and had been shown to harbor a range of traits associated with PGP including siderophore production, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, and inorganic phosphate solubilization. In greenhouse experiments individual strains tagged with gfp and Kmr were applied to Brassica napus as a seed coat and were shown to effectively colonize the rhizosphere and root of B. napus and in addition they demonstrated a significant increase in plant biomass compared with the non-inoculated control. In the field experiment, the bacteria (individual and consortium) were spray inoculated to winter oilseed rape B. napus var. Compass which was grown under standard North Western European agronomic conditions. Analysis of the data provides evidence that the application of the live bacterial biofertilizers can enhance aspects of crop development in B. napus at field scale. The field data demonstrated statistically significant increases in crop height, stem/leaf, and pod biomass, particularly, in the case of the consortium inoculated treatment. However, although seed and oil yield were increased in the field in response to inoculation, these data were not statistically significant under the experimental conditions tested. Future field trials will investigate the effectiveness of the inoculants under different agronomic conditions. PMID:29312422

Inoculation with arbuscular mycorrhizal fungi suppresses initiation of haustoria in the root hemiparasite Pedicularis tricolor.

PubMed

Li, Ai-Rong; Smith, Sally E; Smith, F Andrew; Guan, Kai-Yun

2012-05-01

Plant parasitism and arbuscular mycorrhizal (AM) associations have many parallels and share a number of regulatory pathways. Despite a rapid increase in investigations addressing the roles of AM fungi in regulating interactions between parasitic plants and their hosts, few studies have tested the effect of AM fungi on the initiation and differentiation of haustoria, the parasite-specific structures exclusively responsible for host attachment and nutrient transfer. In this study, we tested the influence of AM fungi on haustorium formation in a root hemiparasitic plant. Using a facultative root hemiparasitic species (Pedicularis tricolor) with the potential to form AM associations, the effects of inoculation were tested with two AM fungal species, Glomus mosseae and Glomus intraradices, on haustorium initiation in P. tricolor grown alone or with Hordeum vulgare 'Fleet' (barley) as the host plant. This study consisted of two greenhouse pot experiments. Both AM fungal species dramatically suppressed intraspecific haustorium initiation in P. tricolor at a very low colonization level. The suppression over-rode inductive effects of the parasite's host plant on haustoria production and caused significant growth depression of P. tricolor. AM fungi had strong and direct suppressive effects on haustorium formation in the root hemiparasite. The significant role of AM fungi in haustorium initiation of parasitic plants was demonstrated for the first time. This study provides new clues for the regulation of haustorium formation and a route to development of new biocontrol strategies in management of parasitic weeds.

Plant growth promotion and root colonization by EPS producing Enterobacter sp. RZS5 under heavy metal contaminated soil.

PubMed

Sayyed, R Z; Patel, P R; Shaikh, S S

2015-02-01

The heavy metal resistant bacterium isolated from field soil and identified as Enterobacter sp. RZS5 tolerates a high concentration (100-2000 μM) of various heavy metal ions such as Mn2+, Ni2+, Zn2+, Cu2+, CO2+ and Fe2+ when grown in such environment and produces exopolysaccharides (EPS). Here, we have demonstrated EPS production by Enterobacter sp. RZS5 during 60 h of growth in yeast extract mannitol broth (YEMB). The yield increased by two fold after the addition of 60 μM of Ca2+; 50 μM of Fe2+ and 60 μM of Mg2+ ions in YEMB, and the optimization of physico-chemical parameters. EPS was extracted with 30% (v/v) of isopropanol as against the commonly used 50% (v/v) isopropanol method. EPS-rich broth promoted seed germination, shoot height, root length, number of leaves and chlorophyll content of wheat (Triticum aestivum) seed and peanut (Arachis hypogaea) seed. The higher colony-forming unit of Enterobacter sp. in soil inoculated with EPS rich broth of Enterobacter sp. indicated the root colonizing potential and rhizosphere competence of the isolate. The FTIR spectra of the EPS extract confirmed the presence of the functional group characteristics of EPS known to exhibit a high binding affinity towards certain metal ions. This overall growth and vigour in plants along with the effective root colonization, reflected the potential of the isolate as an efficient bio-inoculant in bioremediation.

Efficacy Evaluation of Fungus Syncephalastrum racemosum and Nematicide Avermectin against the Root-Knot Nematode Meloidogyne incognita on Cucumber

PubMed Central

Huang, Wen-Kun; Sun, Jian-Hua; Cui, Jiang-Kuan; Wang, Gang-Feng; Kong, Ling-An; Peng, Huan; Chen, Shu-Long; Peng, De-Liang

2014-01-01

The root-knot nematode (RKN) is one of the most damaging agricultural pests.Effective biological control is need for controlling this destructive pathogen in organic farming system. During October 2010 to 2011, the nematicidal effects of the Syncephalastrum racemosum fungus and the nematicide, avermectin, alone or combined were tested against the RKN (Meloidogyne incognita) on cucumber under pot and field condition in China. Under pot conditions, the application of S. racemosum alone or combined with avermectin significantly increased the plant vigor index by 31.4% and 10.9%, respectively compared to the M. incognita-inoculated control. However, treatment with avermectin alone did not significantly affect the plant vigor index. All treatments reduced the number of root galls and juvenile nematodes compared to the untreated control. Under greenhouse conditions, all treatments reduced the disease severity and enhanced fruit yield compared to the untreated control. Fewer nematodes infecting plant roots were observed after treatment with avermectin alone, S. racemosum alone or their combination compared to the M. incognita-inoculated control. Among all the treatments, application of avermectin or S. racemosum combined with avermectin was more effective than the S. racemosum treatment. Our results showed that application of S. racemosum combined with avermectin not only reduced the nematode number and plant disease severity but also enhanced plant vigor and yield. The results indicated that the combination of S. racemosum with avermectin could be an effective biological component in integrated management of RKN on cucumber. PMID:24586982

Photosynthetic Bradyrhizobia Are Natural Endophytes of the African Wild Rice Oryza breviligulata

PubMed Central

Chaintreuil, Clémence; Giraud, Eric; Prin, Yves; Lorquin, Jean; Bâ, Amadou; Gillis, Monique; de Lajudie, Philippe; Dreyfus, Bernard

2000-01-01

We investigated the presence of endophytic rhizobia within the roots of the wetland wild rice Oryza breviligulata, which is the ancestor of the African cultivated rice Oryza glaberrima. This primitive rice species grows in the same wetland sites as Aeschynomene sensitiva, an aquatic stem-nodulated legume associated with photosynthetic strains of Bradyrhizobium. Twenty endophytic and aquatic isolates were obtained at three different sites in West Africa (Senegal and Guinea) from nodal roots of O. breviligulata and surrounding water by using A. sensitiva as a trap legume. Most endophytic and aquatic isolates were photosynthetic and belonged to the same phylogenetic Bradyrhizobium/Blastobacter subgroup as the typical photosynthetic Bradyrhizobium strains previously isolated from Aeschynomene stem nodules. Nitrogen-fixing activity, measured by acetylene reduction, was detected in rice plants inoculated with endophytic isolates. A 20% increase in the shoot growth and grain yield of O. breviligulata grown in a greenhouse was also observed upon inoculation with one endophytic strain and one Aeschynomene photosynthetic strain. The photosynthetic Bradyrhizobium sp. strain ORS278 extensively colonized the root surface, followed by intercellular, and rarely intracellular, bacterial invasion of the rice roots, which was determined with a lacZ-tagged mutant of ORS278. The discovery that photosynthetic Bradyrhizobium strains, which are usually known to induce nitrogen-fixing nodules on stems of the legume Aeschynomene, are also natural true endophytes of the primitive rice O. breviligulata could significantly enhance cultivated rice production. PMID:11097925

Infection of apical dentin and root-end cavity disinfection.

PubMed

Aziz, Abdul; Chandler, Nicholas P; Hauman, Catharina H J; Leichter, Jonathan W; McNaughton, Andrew; Tompkins, Geoffrey R

2012-10-01

The purpose of this study was to assess Enterococcus faecalis penetration into the dentin of the apical 3 mm and bacterial death after the application of either chlorhexidine or laser to root-end cavities. Root canals of 60 single-rooted teeth were prepared. In part 1, cementum was removed semicircumferentially from 21 roots, and the smear layer was removed from 15 roots using 17% EDTA/cetrimide. Teeth were inoculated and incubated with E. faecalis for 10 days, rinsed, and live/dead stained. The effect of cementum and smear on bacterial penetration was assessed by confocal laser scanning microscopy (CLSM). In part 2, 39 teeth had root ends resected and cavities ultrasonically prepared. Inoculated roots were assigned to 1 of the following 3 groups: (1) root-end cavities irrigated with 0.2 % chlorhexidine, (2) root-end cavities irradiated with a laser for 20 seconds at 1.5 W, or (3) root-end cavities that received no treatment. Roots were live/dead stained, sectioned, and examined by CLSM. The depth of the bacterial penetration and bacterial survival were compared using the Mann-Whitney U test. The presence of a smear layer and/or cementum did not significantly affect bacterial penetration. In root-end cavities, chlorhexidine was more effective than laser (P < .001), reducing bacterial viability by 93% versus 70% with a laser. E. faecalis invaded the entire width of dentin in the apical 3 mm irrespective of the smear layer and/or cementum. Chlorhexidine was more effective than laser in disinfecting root-end cavities. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Isolation of plant-growth-promoting rhizobacteria from rhizospheric soil of halophytes and their impact on maize (Zea mays L.) under induced soil salinity.

PubMed

Ullah, Sami; Bano, Asghari

2015-04-01

The present investigation was aimed to scrutinize the salt tolerance potential of plant-growth-promoting rhizobacteria (PGPR) isolated from rhizospheric soil of selected halophytes (Atriplex leucoclada, Haloxylon salicornicum, Lespedeza bicolor, Suaeda fruticosa, and Salicornica virginica) collected from high-saline fields (electrical conductivity 4.3-5.5) of District Mardan, Pakistan. Five PGPR strains were identified using 16S rRNA amplification and sequence analysis. Bacillus sp., isolated from rhizospheric soil of Atriplex leucoclada, and Arthrobacter pascens, isolated from rhizospheric soil of Suaeda fruticosa, are active phosphate solubilizers and bacteriocin and siderophore producers; hence, their inoculation and co-inoculation on maize ('Rakaposhi') under induced salinity stress enhanced shoot and root length and shoot and root fresh and dry mass. The accumulation of osmolytes, including sugar and proline, and the elevation of antioxidant enzymes activity, including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase, were enhanced in the maize variety when inoculated and co-inoculated with Bacillus sp. and Arthrobacter pascens. The PGPR (Bacillus sp. and A. pascens) isolated from the rhizosphere of the mentioned halophytes species showed reliability in growth promotion of maize crop in all the physiological parameters; hence, they can be used as bio-inoculants for the plants growing under salt stress.

Effects of inoculation with organic-phosphorus-mineralizing bacteria on soybean (Glycine max) growth and indigenous bacterial community diversity.

PubMed

Sun, Wei; Qian, Xun; Gu, Jie; Wang, Xiao-Juan; Li, Yang; Duan, Man-Li

2017-05-01

Three different organic-phosphorus-mineralizing bacteria (OPMB) strains were inoculated to soil planted with soybean (Glycine max), and their effects on soybean growth and indigenous bacterial community diversity were investigated. Inoculation with Pseudomonas fluorescens Z4-1 and Brevibacillus agri L7-1 increased organic phosphorus degradation by 22% and 30%, respectively, compared with the control at the mature stage. Strains P. fluorescens Z4-1 and B. agri L7-1 significantly improved the soil alkaline phosphatase activity, average well color development, and the soybean root activity. Terminal restriction fragment length polymorphism analysis demonstrated that P. fluorescens Z4-1 and B. agri L7-1 could persist in the soil at relative abundances of 2.0%-6.4% throughout soybean growth. Thus, P. fluorescens Z4-1 and B. agri L7-1 could potentially be used in organic-phosphorus-mineralizing biofertilizers. OPMB inoculation altered the genetic structure of the soil bacterial communities but had no apparent influence on the carbon source utilization profiles of the soil bacterial communities. Principal components analysis showed that the changes in the carbon source utilization profiles of bacterial community depended mainly on the plant growth stages rather than inoculation with OPMB. The results help to understand the evolution of the soil bacterial community after OPMB inoculation.

Developmental Response of a Resistance-Breaking Population of Meloidogyne arenaria on Vitis spp.

PubMed

Anwar, Safdar A; McKenry, M V

2002-03-01

Pre- and post-infection resistance mechanisms expressed by Vitis rootstocks RS-9 and Teleki 5C against second-stage juveniles (J2) of resistance-breaking populations of Meloidogyne arenaria were observed and correlated with juvenile development and nematode reproduction. Cabernet Sauvignon grape was used as a susceptible control for comparison. Similar numbers of J2 penetrated Teleki 5C and Cabernet Sauvignon roots. Root-tip necrosis, a hypersensitive reaction, occurred in both rootstocks but was effective in reducing J2 penetration only in RS-9 roots. Juvenile development occurred in roots of all three rootstocks by 13 days after inoculation, with the highest number of swollen juveniles present in Cabernet Sauvignon roots. Cortical necroses restricted the ability of J2 to reach vascular bundles, thereby restricting access to successful feeding sites and leading to dead or underdeveloped juveniles in RS-9 roots. At 35 days after inoculation, only 5% and 25% of the initial inoculum in RS-9 and Teleki 5C roots, respectively, reached the adult stage compared to 32% in Cabernet roots. Giant cells were of sufficient size to support nematode development to maturity in Cabernet. Cell necrosis and underdeveloped giant cells were apparent in the resistant rootstocks, which delayed development of adults and limited egg production. Inadequate development of giant cells may provide long-term population reductions in woody-rooted perennial crops.

Enhancement of growth and salt tolerance of red pepper seedlings (Capsicum annuum L.) by regulating stress ethylene synthesis with halotolerant bacteria containing 1-aminocyclopropane-1-carboxylic acid deaminase activity.

PubMed

Siddikee, Md Ashaduzzaman; Glick, Bernard R; Chauhan, Puneet S; Yim, Woo jong; Sa, Tongmin

2011-04-01

Three 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing halotolerant bacteria were isolated from West Coast soil of Yellow Sea, Incheon, South Korea and evaluated for their efficiency in improving red pepper plant growth under salt stress. The strains RS16, RS656 and RS111 were identified by 16S rRNA gene sequencing as Brevibacterium iodinum, Bacillus licheniformis and Zhihengliuela alba, respectively. Two hour exposure of 100, 150 and 200 mM NaCl stress on 8 day old red pepper seedlings caused 44, 64 and 74% increase ethylene production, while at 150 mM NaCl stress, inoculation of B. licheniformis RS656, Z. alba RS111, and Br. iodinum RS16 reduces ethylene production by 44, 53 and 57%, respectively. Similarly, 3 week old red pepper plants were subjected to salt stress for two weeks and approximately ∼50% reduction in growth recorded at 150 mM NaCl stress compared to negative control whereas bacteria inoculation significantly increase the growth compared to positive control. Salt stress also caused 1.3-fold reduction in the root/shoot dry weight ratio compared to the absence of salt while bacteria inoculation retained the biomass allocation similar to control plants. The salt tolerance index (ratio of biomass of salt stressed to non-stressed plant) was also significantly increased in inoculated plants compared to non-inoculated. Increase nutrient uptakes under salt stress by red pepper further evident that bacteria inoculation ameliorates salt stress effect. In summary, this study indicates that the use of ACC deaminase-producing halotolerant bacteria mitigates the salt stress by reducing salt stress-induced ethylene production on growth of red pepper plants. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Effects of arbuscular mycorrhizal inoculation and biochar amendment on maize growth, cadmium uptake and soil cadmium speciation in Cd-contaminated soil.

PubMed

Liu, Ling; Li, Jiwei; Yue, Feixue; Yan, Xinwei; Wang, Fayuan; Bloszies, Sean; Wang, Yanfang

2018-03-01

Experiments conducted to understand how arbuscular mycorrhizal (AM) inoculation or biochar application affect plant growth and heavy metal uptake have thus far looked at single applications of either soil amendment. There is little evidence of their synergistic effects, in particular for plants grown in cadmium (Cd) contaminated soil. We conducted a mesocosm experiment to investigate the effect of AM inoculation (Glomus intraradices BEG 141) and/or wheat-straw biochar amendment on maize (Zea mays L. cv. Hongdan No. 897) growth, antioxidant enzymatic activities, and Cd uptake, as well as soil Cd speciation under applications of 0, 3, 6 mg Cd per kg soil. Applying either AM inoculant or biochar alone significantly increased maize growth and reduced Cd uptake. Furthermore, solo AM inoculation alleviating Cd stress more fully than biochar, in turn facilitating maize growth and decreasing soil Cd translocation into plant tissue. Still, solo biochar amendment was more effective at inducing soil alkalinization and contributing to Cd immobilization. Adding biochar together with AM inoculant significantly promoted fungal populations compared to a control. Amending soil with AM inoculant and biochar together produced the largest increase in maize growth and decrease in tissue Cd concentrations. This effect was additive, with 79.1% greater biomass, 51.42%, 82.91%, 43.96% higher activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and 50.06%, 67.19%, 58.04% and 76.19% lower Cd concentrations in roots, stems, leaves, and ears, respectively, at a 6 mg kg -1 Cd contamination rate. The combined treatment also had a synergistic effect on inducing soil alkalinization and causing Cd immobilization, and decreasing Cd phytoavailability and post-harvest transfer risks. These results suggest that AM inoculation in combination with biochar application may be applicable not only for maize production but also for phytostabilization of Cd-contaminated soil. Copyright © 2017 Elsevier Ltd. All rights reserved.

Burkholderia ambifaria and B. caribensis Promote Growth and Increase Yield in Grain Amaranth (Amaranthus cruentus and A. hypochondriacus) by Improving Plant Nitrogen Uptake

PubMed Central

Parra-Cota, Fannie I.; Peña-Cabriales, Juan J.; de los Santos-Villalobos, Sergio; Martínez-Gallardo, Norma A.; Délano-Frier, John P.

2014-01-01

Grain amaranth is an emerging crop that produces seeds having high quality protein with balanced amino-acid content. However, production is restricted by agronomic limitations that result in yields that are lower than those normally produced by cereals. In this work, the use of five different rhizobacteria were explored as a strategy to promote growth and yields in Amaranthus hypochondriacus cv. Nutrisol and A. cruentus cv. Candil, two commercially important grain amaranth cultivars. The plants were grown in a rich substrate, high in organic matter, nitrogen (N), and phosphorus (P) and under greenhouse conditions. Burkholderia ambifaria Mex-5 and B. caribensis XV proved to be the most efficient strains and significantly promoted growth in both grain amaranth species tested. Increased grain yield and harvest index occurred in combination with chemical fertilization when tested in A. cruentus. Growth-promotion and improved yields correlated with increased N content in all tissues examined. Positive effects on growth also occurred in A. cruentus plants grown in a poor soil, even after N and P fertilization. No correlation between non-structural carbohydrate levels in roots of inoculated plants and growth promotion was observed. Conversely, gene expression assays performed at 3-, 5- and 7-weeks after seed inoculation in plants inoculated with B. caribensis XV identified a tissue-specific induction of several genes involved in photosynthesis, sugar- and N- metabolism and transport. It is concluded that strains of Burkholderia effectively promote growth and increase seed yields in grain amaranth. Growth promotion was particularly noticeable in plants grown in an infertile soil but also occurred in a well fertilized rich substrate. The positive effects observed may be attributed to a bio-fertilization effect that led to increased N levels in roots and shoots. The latter effect correlated with the differential induction of several genes involved in carbon and N metabolism and transport. PMID:24533068

Host-Specialist Dominated Ectomycorrhizal Communities of Pinus cembra are not Affected by Temperature Manipulation

PubMed Central

Rainer, Georg; Kuhnert, Regina; Unterholzer, Mara; Dresch, Philipp; Gruber, Andreas; Peintner, Ursula

2015-01-01

Ectomycorrhizae (EM) are important for the survival of seedlings and trees, but how they will react to global warming or changes in soil fertility is still in question. We tested the effect of soil temperature manipulation and nitrogen fertilization on EM communities in a high-altitude Pinus cembra afforestation. The trees had been inoculated in the 1960s in a nursery with a mixture of Suillus placidus, S. plorans and S. sibircus. Sampling was performed during the third year of temperature manipulation in June and October 2013. Root tips were counted, sorted into morphotypes, and sequenced. Fungal biomass was measured as ergosterol and hyphal length. The EM potential of the soil was assessed with internal transcribed spacers (ITS) clone libraries from in-growth mesh bags (MB). Temperature manipulation of ± 1 °C had no effect on the EM community. A total of 33 operational taxonomic units (OTUs) were identified, 20 from the roots, 13 from MB. The inoculated Suillus spp. colonized 82% of the root tips, thus demonstrating that the inoculation was sustainable. Nitrogen fertilization had no impact on the EM community, but promoted depletion in soil organic matter, and caused a reduction in soil fungal biomass. PMID:29376899

Growth and (137)Cs uptake of four Brassica species influenced by inoculation with a plant growth-promoting rhizobacterium Bacillus pumilus in three contaminated farmlands in Fukushima prefecture, Japan.

PubMed

Aung, Han Phyo; Djedidi, Salem; Oo, Aung Zaw; Aye, Yi Swe; Yokoyama, Tadashi; Suzuki, Sohzoh; Sekimoto, Hitoshi; Bellingrath-Kimura, Sonoko Dorothea

2015-07-15

The effectiveness of the plant growth-promoting rhizobacterium Bacillus pumilus regarding growth promotion and radiocesium ((137)Cs) uptake was evaluated in four Brassica species grown on different (137)Cs contaminated farmlands at Fukushima prefecture in Japan from June to August 2012. B. pumilus inoculation did not enhance growth in any of the plants, although it resulted in a significant increase of (137)Cs concentration and higher (137)Cs transfer from the soil to plants. The Brassica species exhibited different (137)Cs uptake abilities in the order Komatsuna>turnip>mustard>radish. TF values of (137)Cs ranged from 0.018 to 0.069 for all vegetables. Komatsuna possessed the largest root surface area and root volume, and showed a higher (137)Cs concentration in plant tissue and higher (137)Cs TF values (0.060) than the other vegetables. Higher (137)Cs transfer to plants was prominent in soil with a high amount of organic matter and an Al-vermiculite clay mineral type. Copyright © 2015 Elsevier B.V. All rights reserved.

Carbon cost of the fungal symbiont relative to net leaf P accumulation in a split-root VA mycorrhizal symbiosis. [Poncirus trifoliata L. Raf. x Citrus sinensis L. Osbeck; Glomus intraradices Schenk and Smith

DOE Office of Scientific and Technical Information (OSTI.GOV)

Douds, D.D. Jr.; Johnson, C.R.; Koch, K.E.

Translocation of {sup 14}C-photosynthates to mycorrhizal (++), half mycorrhizal (0+), and nonmycorrhizal (00) split-root systems was compared to P accumulation in leaves of the host plant. Carrizo citrange seedlings (Poncirus trifoliata (L.) Raf. {times} Citrus sinensis (L.) Osbeck) were inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck and Smith. Plants were exposed to {sup 14}CO{sub 2} for 10 minutes and ambient air for 2 hours. Three to 4% of recently labeled photosynthate was allocated to metabolism of the mycorrhiza in each inoculated root half independent of shoot P concentration, growth response, and whether one or both root halves weremore » colonized. Nonmycorrhizal roots respired more of the label translocated to them than did mycorrhizal roots. Label recovered in the potting medium due to exudation or transport into extraradical hyphae was 5 to 6 times greater for (++) versus (00) plants. In low nutrient media, roots of (0+) and (++) plants transported more P to leaves per root weight than roots of (00) plants. However, when C translocated to roots utilized for respiration, exudation, etc., as well as growth is considered, (00) plant roots were at least as efficient at P uptake (benefit) per C utilized (cost) as (0+) and (++) plants. Root systems of (++) plants did not supply more P to leaves than (0+) plants in higher nutrient media, yet they still allocated twice the {sup 14}C-photosynthate to the mycorrhiza as did (0+) root systems.« less

Comparison of virulence between vascular competent and incompetent Fusarium oxysporum f. sp. vasinfectum pathotypes

USDA-ARS?s Scientific Manuscript database

The Australian biotype and California race 4 isolates of Fusarium oxysporum f. sp. Vasinfectum (Fov) are pathologically distinct from the Fov U.S. race 1 isolates in that they do not cause disease when stem-puncture inoculated while race 1 isolates do. When root-dip inoculation method was used, bot...

In Vitro Morphogenesis of Arabidopsis to Search for Novel Endophytic Fungi Modulating Plant Growth.

PubMed

Dovana, Francesco; Mucciarelli, Marco; Mascarello, Maurizio; Fusconi, Anna

2015-01-01

Fungal endophytes have shown to affect plant growth and to confer stress tolerance to the host; however, effects of endophytes isolated from water plants have been poorly investigated. In this study, fungi isolated from stems (stem-E) and roots (root-E) of Mentha aquatica L. (water mint) were identified, and their morphogenetic properties analysed on in vitro cultured Arabidopsis (L.) Heynh., 14 and 21 days after inoculation (DAI). Nineteen fungi were analysed and, based on ITS analysis, 17 isolates showed to be genetically distinct. The overall effect of water mint endophytes on Arabidopsis fresh (FW) and dry weight (DW) was neutral and positive, respectively, and the increased DW, mainly occurring 14 DAI, was possibly related to plant defence mechanism. Only three fungi increased both FW and DW of Arabidopsis at 14 and 21 DAI, thus behaving as plant growth promoting (PGP) fungi. E-treatment caused a reduction of root depth and primary root length in most cases and inhibition-to-promotion of root area and lateral root length, from 14 DAI. Only Phoma macrostoma, among the water mint PGP fungi, increased both root area and depth, 21 DAI. Root depth and area 14 DAI were shown to influence DWs, indicating that the extension of the root system, and thus nutrient uptake, was an important determinant of plant dry biomass. Reduction of Arabidopsis root depth occurred to a great extent when plants where treated with stem-E while root area decreased or increased under the effects of stem-E and root-E, respectively, pointing to an influence of the endophyte origin on root extension. M. aquatica and many other perennial hydrophytes have growing worldwide application in water pollution remediation. The present study provided a model for directed screening of endophytes able to modulate plant growth in the perspective of future field applications of these fungi.

Soil-based systemic delivery and phyllosphere in vivo propagation of bacteriophages: Two possible strategies for improving bacteriophage persistence for plant disease control.

PubMed

Iriarte, Fanny B; Obradović, Aleksa; Wernsing, Mine H; Jackson, Lee E; Balogh, Botond; Hong, Jason A; Momol, M Timur; Jones, Jeffrey B; Vallad, Gary E

2012-10-01

Soil-based root applications and attenuated bacterial strains were evaluated as means to enhance bacteriophage persistence on plants for bacterial disease control. In addition, the systemic nature of phage applied to tomato roots was also evaluated. Several experiments were conducted applying either single phages or phage mixtures specific for Ralstonia solanacearum , Xanthomonas perforans or X. euvesicatoria to soil surrounding tomato plants and measuring the persistence and translocation of the phages over time. In general, all phages persisted in the roots of treated plants and were detected in stems and leaves; although phage level varied and persistence in stems and leaves was at a much lower level compared with persistence in roots. Bacterial wilt control was typically best if the phage or phage mixtures were applied to the soil surrounding tomatoes at the time of inoculation, less effective if applied 3 days before inoculation, and ineffective if applied 3 days after inoculation. The use of an attenuated X. perforans strain was also evaluated to improve the persistence of phage populations on tomato leaf surfaces. In greenhouse and field experiments, foliar applications of an attenuated mutant X. perforans 91-118:∆ OPGH strain prior to phage applications significantly improved phage persistence on tomato foliage compared with untreated tomato foliage. Both the soil-based bacteriophage delivery and the use of attenuated bacterial strains improved bacteriophage persistence on respective root and foliar tissues, with evidence of translocation with soil-based bacteriophage applications. Both strategies could lead to improved control of bacterial pathogens on plants.

Growth in microgravity increases susceptibility of soybean to a fungal pathogen

NASA Technical Reports Server (NTRS)

Ryba-White, M.; Nedukha, O.; Hilaire, E.; Guikema, J. A.; Kordyum, E.; Leach, J. E.; Spooner, B. S. (Principal Investigator)

2001-01-01

The influence of microgravity on the susceptibility of soybean roots to Phytophthora sojae was studied during the Space Shuttle Mission STS-87. Seedlings of soybean cultivar Williams 82 grown in spaceflight or at unit gravity were untreated or inoculated with the soybean root rot pathogen P. sojae. At 3, 6 and 7 d after launch while still in microgravity, seedlings were photographed and then fixed for subsequent microscopic analysis. Post-landing analysis of the seedlings revealed that at harvest day 7 the length of untreated roots did not differ between flight and ground samples. However, the flight-grown roots infected with P. sojae showed more disease symptoms (percentage of brown and macerated areas) and the root tissues were more extensively colonized relative to the ground controls exposed to the fungus. Ethylene levels were higher in spaceflight when compared to ground samples. These data suggest that soybean seedlings grown in microgravity are more susceptible to colonization by a fungal pathogen relative to ground controls.

[Induction and in vitro culture of hairy roots of Dianthus caryophyllus and its plant regeneration].

PubMed

Shi, Heping; Zhu, Yuanfeng; Wang, Bei; Sun, Jiangbing; Huang, Shengqin

2014-11-01

To use Agrobacterium rhizogenes-induced hairy roots to create new germplasm of Dianthus caryophyllus, we transformed D. caryophyllus with A. rhizogenes by leaf disc for plant regeneration from hairy roots. The white hairy roots could be induced from the basal surface of leaf explants of D. caryophyllus 12 days after inoculation with A. rhizogenes ATCC15834. The percentage of the rooting leaf explants was about 90% 21 days after inoculation. The hairy roots could grow rapidly and autonomously in liquid or solid phytohormone-free MS medium. The transformation was confirmed by PCR amplification of rol gene of Ri plasmid and silica gel thin-layer chromatography of opines from D. caryophyllus hairy roots. Hairy roots could form light green callus after cultured on MS+6-BA 1.0-3.0 mg/L + NAA 0.1-0.2 mg/L for 15 days. The optimum medium for adventitious shoots formation was MS + 6-BA 2.0 mg/L + NAA 0.02 mg/L, where the rate of adventitious shoot induction was 100% after cultured for 6 weeks. The mean number of adventitious shoot per callus was 30-40. The adventitious shoots can form roots when cultured on phytohormone-free 1/2 MS or 1/2 MS +0.5 mg/L NAA for 10 days. When the rooted plantlets transplanted in the substrate mixed with perlite sand and peat (volume ratio of 1:2), the survival rate was above 95%.

Metabolic profiling of two maize (Zea mays L.) inbred lines inoculated with the nitrogen fixing plant-interacting bacteria Herbaspirillum seropedicae and Azospirillum brasilense

PubMed Central

Brusamarello-Santos, Liziane Cristina; Gilard, Françoise; Brulé, Lenaïg; Quilleré, Isabelle; Gourion, Benjamin; Ratet, Pascal; Maltempi de Souza, Emanuel; Lea, Peter J.; Hirel, Bertrand

2017-01-01

Maize roots can be colonized by free-living atmospheric nitrogen (N2)-fixing bacteria (diazotrophs). However, the agronomic potential of non-symbiotic N2-fixation in such an economically important species as maize, has still not been fully exploited. A preliminary approach to improve our understanding of the mechanisms controlling the establishment of such N2-fixing associations has been developed, using two maize inbred lines exhibiting different physiological characteristics. The bacterial-plant interaction has been characterized by means of a metabolomic approach. Two established model strains of Nif+ diazotrophic bacteria, Herbaspirillum seropedicae and Azospirillum brasilense and their Nif- couterparts defficient in nitrogenase activity, were used to evaluate the impact of the bacterial inoculation and of N2 fixation on the root and leaf metabolic profiles. The two N2-fixing bacteria have been used to inoculate two genetically distant maize lines (FV252 and FV2), already characterized for their contrasting physiological properties. Using a well-controlled gnotobiotic experimental system that allows inoculation of maize plants with the two diazotrophs in a N-free medium, we demonstrated that both maize lines were efficiently colonized by the two bacterial species. We also showed that in the early stages of plant development, both bacterial strains were able to reduce acetylene, suggesting that they contain functional nitrogenase activity and are able to efficiently fix atmospheric N2 (Fix+). The metabolomic approach allowed the identification of metabolites in the two maize lines that were representative of the N2 fixing plant-bacterial interaction, these included mannitol and to a lesser extend trehalose and isocitrate. Whilst other metabolites such as asparagine, although only exhibiting a small increase in maize roots following bacterial infection, were specific for the two Fix+ bacterial strains, in comparison to their Fix- counterparts. Moreover, a number of metabolites exhibited a maize-genotype specific pattern of accumulation, suggesting that the highly diverse maize genetic resources could be further exploited in terms of beneficial plant-bacterial interactions for optimizing maize growth, with reduced N fertilization inputs. PMID:28362815

Metabolic profiling of two maize (Zea mays L.) inbred lines inoculated with the nitrogen fixing plant-interacting bacteria Herbaspirillum seropedicae and Azospirillum brasilense.

PubMed

Brusamarello-Santos, Liziane Cristina; Gilard, Françoise; Brulé, Lenaïg; Quilleré, Isabelle; Gourion, Benjamin; Ratet, Pascal; Maltempi de Souza, Emanuel; Lea, Peter J; Hirel, Bertrand

2017-01-01

Maize roots can be colonized by free-living atmospheric nitrogen (N2)-fixing bacteria (diazotrophs). However, the agronomic potential of non-symbiotic N2-fixation in such an economically important species as maize, has still not been fully exploited. A preliminary approach to improve our understanding of the mechanisms controlling the establishment of such N2-fixing associations has been developed, using two maize inbred lines exhibiting different physiological characteristics. The bacterial-plant interaction has been characterized by means of a metabolomic approach. Two established model strains of Nif+ diazotrophic bacteria, Herbaspirillum seropedicae and Azospirillum brasilense and their Nif- couterparts defficient in nitrogenase activity, were used to evaluate the impact of the bacterial inoculation and of N2 fixation on the root and leaf metabolic profiles. The two N2-fixing bacteria have been used to inoculate two genetically distant maize lines (FV252 and FV2), already characterized for their contrasting physiological properties. Using a well-controlled gnotobiotic experimental system that allows inoculation of maize plants with the two diazotrophs in a N-free medium, we demonstrated that both maize lines were efficiently colonized by the two bacterial species. We also showed that in the early stages of plant development, both bacterial strains were able to reduce acetylene, suggesting that they contain functional nitrogenase activity and are able to efficiently fix atmospheric N2 (Fix+). The metabolomic approach allowed the identification of metabolites in the two maize lines that were representative of the N2 fixing plant-bacterial interaction, these included mannitol and to a lesser extend trehalose and isocitrate. Whilst other metabolites such as asparagine, although only exhibiting a small increase in maize roots following bacterial infection, were specific for the two Fix+ bacterial strains, in comparison to their Fix- counterparts. Moreover, a number of metabolites exhibited a maize-genotype specific pattern of accumulation, suggesting that the highly diverse maize genetic resources could be further exploited in terms of beneficial plant-bacterial interactions for optimizing maize growth, with reduced N fertilization inputs.

Local and systemic mycorrhiza-induced protection against the ectoparasitic nematode Xiphinema index involves priming of defence gene responses in grapevine

PubMed Central

Hao, Zhipeng; Fayolle, Léon; van Tuinen, Diederik; Chatagnier, Odile; Gianinazzi, Silvio; Gianinazzi-Pearson, Vivienne

2012-01-01

The ectoparasitic dagger nematode (Xiphinema index), vector of Grapevine fanleaf virus (GFLV), provokes gall formation and can cause severe damage to the root system of grapevines. Mycorrhiza formation by Glomus (syn. Rhizophagus) intraradices BEG141 reduced both gall formation on roots of the grapevine rootstock SO4 (Vitis berlandieri×V. riparia) and nematode number in the surrounding soil. Suppressive effects increased with time and were greater when the nematode was post-inoculated rather than co-inoculated with the arbuscular mycorrhizal (AM) fungus. Using a split-root system, decreased X. index development was shown in mycorrhizal and non-mycorrhizal parts of mycorrhizal root systems, indicating that both local and systemic induced bioprotection mechanisms were active against the ectoparasitic nematode. Expression analyses of ESTs (expressed sequence tags) generated in an SSH (subtractive suppressive hybridization) library, representing plant genes up-regulated during mycorrhiza-induced control of X. index, and of described grapevine defence genes showed activation of chitinase 1b, pathogenesis-related 10, glutathione S-transferase, stilbene synthase 1, 5-enolpyruvyl shikimate-3-phosphate synthase, and a heat shock proein 70-interacting protein in association with the observed local and/or systemic induced bioprotection against the nematode. Overall, the data suggest priming of grapevine defence responses by the AM fungus and transmission of a plant-mediated signal to non-mycorrhizal tissues. Grapevine gene responses during AM-induced local and systemic bioprotection against X. index point to biological processes that are related either to direct effects on the nematode or to protection against nematode-imposed stress to maintain root tissue integrity. PMID:22407649

Temporal impact of the vascular wilt pathogen Verticillium dahliae on tomato root proteome.

PubMed

Witzel, Katja; Buhtz, Anja; Grosch, Rita

2017-10-03

The soil-borne fungus Verticillium dahliae is the causal agent of wilting disease and affects a wide range of plant species worldwide. Here, we report on the time-resolved analysis of the tomato root proteome in response to fungal colonization. Tomato (Solanum lycopersicum cv. Hildares) was inoculated with V. dahliae at the two-leaf stage and roots were harvested at 7, 14 and 21 days post inoculation (dpi). In order to identify proteins related to the fungal spread at the different time points, a subsequent proteome analysis by two-dimensional differential gel electrophoresis (2D-DIGE) was conducted on samples from three independent experiments. Hierarchical clustering and k-means clustering of identified proteins distinguished early and late responses to fungal colonization. The results underline that plant defense and adaptation responses are timely coordinated. Proteins involved in oxidative stress were down-regulated at 7 dpi but induced 21 dpi indicating versatile reactive oxygen species signaling interacting with salicylic acid defence signaling at that stage of infection. Drought-stress proteins were induced at 21 dpi, reflecting the beginning of wilting symptoms. Notably, two proteins involved in energy-generating pathways were induced throughout all sampling dates and may reflect the increase in metabolic activity to maintain root growth and, concurrently, activate defense responses. Mounting of defense responses requires a substantial flux of carbon and nitrogen from primary to secondary metabolites. In-depth understanding of these key metabolic pathways required for growth and defense responses, especially at proteome level, will allow the development of breeding strategies for crops where Verticillium tolerance is absent. Our data show early and late responses of tomato root proteins towards pathogen infection and identify primary metabolism enzymes affected by V. dahliae. Those proteins represent candidates for plant improvement. Copyright © 2017 Elsevier B.V. All rights reserved.

Interaction of Escherichia coli with growing salad spinach plants.

PubMed

Warriner, Keith; Ibrahim, Faozia; Dickinson, Matthew; Wright, Charles; Waites, William M

2003-10-01

In this study, the interaction of a bioluminescence-labeled Escherichia coli strain with growing spinach plants was assessed. Through bioluminescence profiles, the direct visualization of E. coli growing around the roots of developing seedlings was accomplished. Subsequent in situ glucuronidase (GUS) staining of seedlings confirmed that E. coli had become internalized within root tissue and, to a limited extent, within hypocotyls. When inoculated seeds were sown in soil microcosms and cultivated for 42 days, E. coli was recovered from the external surfaces of spinach roots and leaves as well as from surface-sterilized roots. When 20-day-old spinach seedlings (from uninoculated seeds) were transferred to soil inoculated with E. coli, the bacterium became established on the plant surface, but internalization into the inner root tissue was restricted. However, for seedlings transferred to a hydroponic system containing 10(2) or 10(3) CFU of E. coli per ml of the circulating nutrient solution, the bacterium was recovered from surface-sterilized roots, indicating that it had been internalized. Differences between E. coli interactions in the soil and those in the hydroponic system may be attributed to greater accessibility of the roots in the latter model. Alternatively, the presence of a competitive microflora in soil may have restricted root colonization by E. coli. The implications of this study's findings with regard to the microbiological safety of minimally processed vegetables are discussed.

Establishment of Withania somnifera hairy root cultures for the production of withanolide A.

PubMed

Murthy, Hosakatte N; Dijkstra, Camelia; Anthony, Paul; White, Daniel A; Davey, Mike R; Power, J Brian; Hahn, Eun J; Paek, Kee Y

2008-08-01

Withania sominifera (Indian ginseng) was transformed by Agrobacterium rhizogenes. Explants from seedling roots, stems, hypocotyls, cotyledonary nodal segments, cotyledons and young leaves were inoculated with A. rhizogenes strain R1601. Hairy (transformed) roots were induced from cotyledons and leaf explants. The transgenic status of hairy roots was confirmed by polymerase chain reaction using nptII and rolB specific primers and, subsequently, by Southern analysis for the presence of nptII and rolB genes in the genomes of transformed roots. Four clones of hairy roots were established; these differed in their morphology. The doubling time of faster growing cultures was 8-14 d with a fivefold increase in biomass after 28 d compared with cultured, non-transformed seedling roots. MS-based liquid medium was superior for the growth of transformed roots compared with other culture media evaluated (SH, LS and N6), with MS-based medium supplemented with 40 g/L sucrose being optimal for biomass production. Cultured hairy roots synthesized withanolide A, a steroidal lactone of medicinal and therapeutic value. The concentration of withanolide A in transformed roots (157.4 microg/g dry weight) was 2.7-fold more than in non-transformed cultured roots (57.9 microg/g dry weight).

Endophytic bacterium Sphingomonas SaMR12 promotes cadmium accumulation by increasing glutathione biosynthesis in Sedum alfredii Hance.

PubMed

Pan, Fengshan; Meng, Qian; Wang, Qiong; Luo, Sha; Chen, Bao; Khan, Kiran Yasmin; Yang, Xiaoe; Feng, Ying

2016-07-01

A hydroponic experiment was conducted to verify the effects of inoculation with endophytic bacteria Sphingomonas SaMR12 on root growth, cadmium (Cd) uptake, reactive oxygen species (ROS), antioxidases, glutathione (GSH) and the related gene expression of Sedum alfredii Hance under different levels of Cd such as 0, 10, 25, 100 and 400 μM. The results showed that inoculation of SaMR12 improved Cd accumulation and upregulated glutathione synthase (GS) expression, but slightly reduced malondialdehyde (MDA) concentration and alleviated Cd-induced damage in roots. However it didn't alter the activities of antioxidant enzymes. When Cd concentration exceeded 25 μM, SaMR12 increased the concentration of GSH and the expression level of GSH1. At high Cd treatment levels (100 and 400 μM), SaMR12 significantly reduced H2O2 concentration and enhanced expression level of 1-Cys peroxiredoxin PER1 and ATPS genes. These results indicate that although SaMR12 has no significant effects on antioxidases activities, it reduces H2O2 concentration by enhancing GSH concentration and relevant genes expression, and subsequently improves Cd tolerance and accumulation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of arbuscular mycorrhizal fungi on young vines in copper-contaminated soil

PubMed Central

Ambrosini, Vítor Gabriel; Voges, Joana Gerent; Canton, Ludiana; Couto, Rafael da Rosa; Ferreira, Paulo Ademar Avelar; Comin, Jucinei José; de Melo, George Wellington Bastos; Brunetto, Gustavo; Soares, Cláudio Roberto Fonsêca Sousa

2015-01-01

Abstract High copper (Cu) levels in uprooted old vineyard soils may cause toxicity in transplanted young vines, although such toxicity may be reduced by inoculating plants with arbuscular mycorrhizal fungi (AMF). The objective of this study was to evaluate the effects of AMF on the plant growth, chlorophyll contents, mycorrhizal colonization, and Cu and phosphorus (P) absorption in young vines cultivated in a vineyard soil contaminated by Cu. Commercial vineyard soil with high Cu levels was placed in plastic tubes and transplanted with young vines, which were inoculated with six AMF species (Dentiscutata heterogama, Gigaspora gigantea, Acaulospora morrowiae, A. colombiana, Rhizophagus clarus, R. irregularis) and a control treatment on randomized blocks with 12 replicates. After 130 days, the mycorrhizal colonization, root and shoot dry matter (DM), height increment, P and Cu absorption, and chlorophyll contents were evaluated. The height increment, shoot DM and chlorophyll contents were not promoted by AMF, although the root DM was increased by R. clarus and R. irregularis, which had the greatest mycorrhizal colonization and P uptake. AMF increased Cu absorption but decreased its transport to shoots. Thus, AMF species, particularly R. clarus and R. irregularis, contribute to the establishment of young vines exposed to high Cu levels. PMID:26691462

[Effects of arbuscular mycorrhizal fungi on the growth and rare earth elements uptake of soybean grown in rare earth mine tailings].

PubMed

Guo, Wei; Zhao, Ren-xin; Zhao, Wen-jing; Fu, Rui-ying; Guo, Jiang-yuan; Zhang, Jun

2013-05-01

A greenhouse pot experiment was conducted to investigate the influence of arbuscular mycorrhizal (AM) fungi Glomus versiforme on the plant growth, nutrient uptake, C: N: P stoichiometric, uptake of heavy metals and rare earth elements by soybean (Glycine max) grown in rare earth mine tailings. The aim was to provide a basis for the revegetation of rare earth mine tailings. The results indicated that soybean had a high mycorrhizal colonization and symbiotic associations were successfully established with G. versiforme, with an average rate of approximately 67%. The colonization of G. versiforme significantly promoted the growth of soybean, increased P, K contents, and decreased C: N: P ratios, supporting the growth rate hypothesis. Inoculation with G. versiforme significantly decreased shoots and roots La, Ce, Pr and Nd concentrations of soybean compared to the control treatment. However, inoculation with G. versiforme had no significant effect on the heavy metal concentrations, except for significantly decreased shoot Fe and Cr concentrations and increased root Cd concentrations. The experiment demonstrates that AM fungi have a potential role for soybean to adapt the composite adversity of rare earth tailings and play a positive role in revegetation of rare earth mine tailings. Further studies on the role of AM fungi under natural conditions should be conducted.

Interaction of Concurrent Populations of Meloidogyne partityla and Mesocriconema xenoplax on Pecan

PubMed Central

Wood, B. W.

2008-01-01

The effect of the interaction between Meloidogyne partityla and Mesocriconema xenoplax on nematode reproduction and vegetative growth of Carya illinoinensis ‘Desirable’ pecan was studied in field microplots. Meloidogyne partityla suppressed reproduction of M. xenoplax, whereas the presence of M. xenoplax did not affect the population density of M. partityla second-stage juveniles in soil. Above-ground tree growth, as measured by trunk diameter 32 months following inoculation, was reduced in the presence of M. partityla alone or in combination with M. xenoplax as compared with the uninoculated control trees. The interaction between M. partityla and M. xenoplax was significant for dry root weight 37 months after inoculation. Results indicate that the presence of the two nematode species together caused a greater reduction in root growth than M. xenoplax alone, but not when compared to M. partityla alone. Mouse-ear symptom severity in pecan leaves was increased in the presence of M. partityla compared with M. xenoplax and the uninoculated control. Infection with M. partityla increased severity of mouse-ear symptoms expressed by foliage. The greater negative impact of M. partityla on vegetative growth of pecan seedlings in field microplots indicates that it is likely a more detrimental pathogen to pecan than is M. xenoplax and is likely an economic pest of pecan. PMID:19440263

Growth stimulation ofTamarindus indica by selected VA mycorrhizal fungi.

PubMed

Reena, J; Bagyaraj, D J

1990-03-01

Efficient vesicular arbuscular mycorrhizal (VAM) fungi were screened and selected for a slow-growing forest tree species,Tamarindus indica L., important in tropical forestry. Seedlings were inoculated with 13 different VAM fungi, obtained from various sources around the world. Inoculated plants had greater plant height, leaf number, stem girth, biomass, phosphate and Zn(2+) content. They also had higher amounts of mycorrhizal spores, per cent root colonization and external hyphae, as measured by per cent soil aggregation.Tamarindus indica seedlings responded best to inoculation withGigaspora margarita (ICRISAT) followed byGlomus fasciculatum.

Involvement of endothelin and ET(A) endothelin receptor in mechanical allodynia in mice given orthotopic melanoma inoculation.

PubMed

Fujita, Masahide; Andoh, Tsugunobu; Saiki, Ikuo; Kuraishi, Yasushi

2008-02-01

We investigated whether endothelin (ET) would be involved in skin cancer pain in mice. Orthotopic inoculation of B16-BL6 melanoma cells into the plantar region of the hind paw produced marked mechanical allodynia in C57BL/6 mice. Intraplantar injections of the ET(A)-receptor antagonist BQ-123 (0.3 - 3 nmol/site), but not the ET(B)-receptor antagonist BQ-788 (1 and 3 nmol/site), inhibited mechanical allodynia in mice with grown melanoma. In naive mice, an intraplantar injection of tumor extract (1 and 3 mg/site), which was prepared from the grown melanoma in the paw, produced mechanical allodynia, which was inhibited by BQ-123 and BQ-788 at doses of 3 and 10 nmol/site. An intraplantar injection of ET-1 (1 and 10 pmol/site) elicited licking behavior, which was increased in the melanoma-bearing hind paw. BQ-123 (3 and 10 nmol/site) inhibited licking induced by ET-1 (10 pmol/site). The level of mRNA of ET(A), but not ET(B), receptor, was significantly increased in the dorsal root ganglia on the inoculated side. Cultured B16-BL6 cells contained ET, and the melanoma mass increased the concentration of ET as it grew bigger. These results suggest that ET-1 and ET(A) receptor are at least partly involved in the induction of pain induced by melanoma cell inoculation.

Selection of ectomycorrhizal willow genotype in phytoextraction of heavy metals.

PubMed

Hrynkiewicz, Katarzyna; Baum, Christel

2013-01-01

Willow clones are used for the phytoextraction of heavy metals from contaminated soils and are usually mycorrhizal. The receptiveness of willow clones for mycorrhizal inoculum varies specific to genotype; however, it is unknown if this might have a significant impact on their efficiency in phytoextraction of heavy metals. Therefore, a model system with mycorrhizal and non-mycorrhizal willows of two different genotypes--one with usually stronger natural mycorrhizal colonization (Salix dasyclados), and one with lower natural mycorrhizal colonization (S. viminalis)--was investigated for its efficiency of phytoextraction of heavy metals (Cd, Pb, Cu, Zn) from contaminated soil. Inoculation with the ectomycorrhizal fungus Amanita muscaria significantly decreased the biomass of leaves of both inoculated willow clones, and increased or had no effect on the biomass of trunks and roots of S. dasyclados and S. viminalis, respectively. The concentrations of heavy metals in the biomass of S. dasyclados were in general higher than in S. viminalis irrespective of inoculation with the ectomycorrhizal fungus. Inoculation with A. muscaria significantly decreased the concentration of Cu in the trunks of both Salix taxa, but did not affected the concentrations of other heavy metals in the biomass. In conclusion, stronger receptiveness of willow clones for mycorrhizal inoculum was correlated with an increased total extraction of heavy metals from contaminated soils. Therefore, this seems to be a suitable criterion for effective willow clone selection for phytoremediation. Increased biomass production with relatively constant metal concentrations seems to be a major advantage of mycorrhizal formation of willows in phytoremediation of contaminated soils.

Effect of endophytic Bacillus cereus ERBP inoculation into non-native host: Potentials and challenges for airborne formaldehyde removal.

PubMed

Khaksar, Gholamreza; Treesubsuntorn, Chairat; Thiravetyan, Paitip

2016-10-01

Phytoremediation could be a cost-effective, environmentally friendly approach for the treatment of indoor air. However, some drawbacks still dispute the expediency of phytotechnology. Our objectives were to investigate the competency of plant growth-promoting (PGP) endophytic Bacillus cereus ERBP (endophyte root blue pea), isolated from the root of Clitoria ternatea, to colonize and stabilize within Zamioculcas zamiifolia and Euphorbia milii as non-native hosts without causing any disease or stress symptoms. Moreover, the impact of B. cereus ERBP on the natural shoot endophytic community and for the airborne formaldehyde removal capability of non-native hosts was assessed. Non-native Z. zamiifolia was effectively inoculated with B. cereus ERBP through soil as the most efficient method of endophyte inoculation. Denaturing gradient gel electrophoresis profiling of the shoot endophytic community verified the colonization and stability of B. cereus ERBP within its non-native host during a 20-d fumigation period without interfering with the natural shoot endophytic diversity of Z. zamiifolia. B. cereus ERBP conferred full protection to its non-native host against formaldehyde phytotoxicity and enhanced airborne formaldehyde removal of Z. zamiifolia whereas non-inoculated plants suffered from formaldehyde phytotoxicity because their natural shoot endophytic community was detrimentally affected by formaldehyde. In contrast, B. cereus ERBP inoculation into non-native E. milii deteriorated airborne formaldehyde removal of the non-native host (compared to a non-inoculated one) as B. cereus ERBP interfered with natural shoot endophytic community of E. milii, which caused stress symptoms and stimulated ethylene biosynthesis. Non-native host inoculation with PGP B. cereus ERBP could bear potentials and challenges for airborne formaldehyde removal. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Huanglongbing impairs the rhizosphere-to-rhizoplane enrichment process of the citrus root-associated microbiome.

PubMed

Zhang, Yunzeng; Xu, Jin; Riera, Nadia; Jin, Tao; Li, Jinyun; Wang, Nian

2017-08-10

Roots are the primary site for plant-microbe interactions. Among the three root-associated layers (i.e., rhizosphere, rhizoplane, and endorhiza), the rhizoplane is a key component serving a critical gating role that controls microbial entry into plant roots. The microbial communities colonizing the three layers are believed to be gradually enriched from the bulk soil inoculum. However, it is unknown how this enrichment process, particularly the rhizosphere to rhizoplane step, is affected by biotic stresses, such as disease. In this study, we address this question using the citrus root-associated microbiome as a model. We identified the rhizosphere-to-rhizoplane-enriched taxonomic and functional properties of the citrus root-associated microbiome and determined how they were affected by Huanglongbing (HLB), a severe systemic disease caused by Candidatus Liberibacter asiaticus, using metagenomic and metatranscriptomic approaches. Multiple rhizoplane-enriched genera were identified, with Bradyrhizobium and Burkholderia being the most dominant. Plant-derived carbon sources are an important driving force for the enrichment process. The enrichment of functional attributes, such as motility, chemotaxis, secretion systems, and lipopolysaccharide (LPS) synthesis, demonstrated more active microbe-plant interactions on the rhizoplane than the rhizosphere. We observed that HLB impaired the rhizosphere-to-rhizoplane enrichment process of the citrus root-associated microbiome in three ways: (1) by decreasing the relative abundance of most rhizoplane-enriched genera; (2) by reducing the relative abundance and/or expression activity of the functional attributes involved in microbe-plant interactions; and (3) by recruiting more functional features involved in autotrophic life cycle adaptation, such as carbon fixation and nitrogen nitrification in the HLB rhizoplane microbiome. Finally, our data showed that inoculation of Burkholderia strains isolated from the healthy citrus root-associated microbiome could trigger the expression of genes involved in induced systemic resistance in inoculated plants. HLB causes decreased relative abundance and/or expression activity of rhizoplane-enriched taxonomic and functional properties, collectively resulting in impaired plant host-microbiome interactions. Manipulation of the citrus root-associated microbiome, for instance, by inoculating citrus roots with beneficial Burkholderia strains, has potential to promote plant health. Our results provide novel insights for understanding the contributions of the community enrichment process of the root-associated microbiome to the plant hosts.

Effect of nitrate supply and mycorrhizal inoculation on characteristics of tobacco root plasma membrane vesicles.

PubMed

Moche, Martin; Stremlau, Stefanie; Hecht, Lars; Göbel, Cornelia; Feussner, Ivo; Stöhr, Christine

2010-01-01

Plant plasma membrane (pm) vesicles from mycorrhizal tobacco (Nicotiana tabacum cv. Samsun) roots were isolated with negligible fungal contamination by the aqueous two-phase partitioning technique as proven by fatty acid analysis. Palmitvaccenic acid became apparent as an appropriate indicator for fungal membranes in root pm preparations. The pm vesicles had a low specific activity of the vanadate-sensitive ATPase and probably originated from non-infected root cells. In a phosphate-limited tobacco culture system, root colonisation by the vesicular arbuscular mycorrhizal fungus, Glomus mosseae, is inhibited by external nitrate in a dose-dependent way. However, detrimental high concentrations of 25 mM nitrate lead to the highest colonisation rate observed, indicating that the defence system of the plant is impaired. Nitric oxide formation by the pm-bound nitrite:NO reductase increased in parallel with external nitrate supply in mycorrhizal roots in comparison to the control plants, but decreased under excess nitrate. Mycorrhizal pm vesicles had roughly a twofold higher specific activity as the non-infected control plants when supplied with 10-15 mM nitrate.

Bacterial Cr(VI) reduction concurrently improves sunflower (Helianthus Annuus L.) growth.

PubMed

Faisal, Muhammad; Hasnain, Shahida

2005-07-01

Four Cr(VI)-reducing bacterial strains (Ochrobactrum intermedium, CrT-2, CrT-3 and CrT-4) previously isolated from chromium-contaminated sites were inoculated on to seeds of sunflower (Helianthus annuus var SF-187), which were germinated and grown along with non-inoculated controls with chromate salts (300 microg CrCl3 or K2CrO4 ml(-1)). Severe reduction (20%) in seed germination was observed in Cr(VI) stress. Plant height decreased (36%) with Cr(VI) when compared with chromium-free control, while O. intermedium inoculation resulted a 20% increment in this parameter as compared to non-inoculated chromium-free control. CrT-3 inoculation resulted a 69% increment in auxin content as compared to non-inoculated control. O. intermedium caused 30% decrease in chromium uptake in sunflower plant roots under Cr(VI) stress as compared to chromium-free control plants.

Systemic Infection of Maize, Sorghum, Rice, and Beet Seedlings with Fumonisin-Producing and Nonproducing Fusarium verticillioides Strains

PubMed Central

Dastjerdi, Raana; Karlovsky, Petr

2015-01-01

Two fumonisin-nonproducing strains of Fusarium verticillioides and their fumonisin producing progenitors were tested for aggressiveness toward maize, sorghum, rice, and beetroot seedlings grown under greenhouse conditions. None of the plants showed obvious disease symptoms after root dip inoculation. Fungal biomass was determined by species-specific real-time PCR. No significant (P = 0.05) differences in systemic colonization were detected between the wild type strains and mutants not producing fumonisins. F. verticillioides was not detected in any of the non-inoculated control plants. The fungus grew from roots to the first two internodes/leaves of maize, rice and beet regardless of fumonisin production. The systemic growth of F. verticillioides in sorghum was limited. The results showed that fumonisin production was not required for the infection of roots of maize, rice and beet by F. verticillioides. PMID:26672472

Effect of wheat roots infected with the pathogenic fungus Gaeumannomyces graminis var. tritici on gene expression of the biocontrol bacterium Pseudomonas fluorescens Pf29Arp.

PubMed

Barret, Matthieu; Frey-Klett, Pascale; Guillerm-Erckelboudt, Anne-Yvonne; Boutin, Morgane; Guernec, Gregory; Sarniguet, Alain

2009-12-01

Traits contributing to the competence of biocontrol bacteria to colonize plant roots are often induced in the rhizosphere in response to plant components. These interactions have been studied using the two partners in gnotobiotic systems. However, in nature, beneficial or pathogenic fungi often colonize roots. Influence of these plant-fungus interactions on bacterial behavior remains to be investigated. Here, we have examined the influence of colonization of wheat roots by the take-all fungus Gaeumannomyces graminis var. tritici on gene expression of the biocontrol bacterium Pseudomonas fluorescens Pf29Arp. Bacteria were inoculated onto healthy, early G. graminis var. tritici-colonized and necrotic roots and transcriptomes were compared by shotgun DNA microarray. Pf29Arp decreased disease severity when inoculated before the onset of necrosis. Necrotic roots exerted a broader effect on gene expression compared with early G. graminis var. tritici-colonized and healthy roots. A gene encoding a putative type VI secretion system effector was only induced in necrotic conditions. A common pool of Pf29Arp genes differentially expressed on G. graminis var. tritici-colonized roots was related to carbon metabolism and oxidative stress, with a highest fold-change with necrosis. Overall, the data showed that the association of the pathogenic fungus with the roots strongly altered Pf29Arp adaptation with differences between early and late G. graminis var. tritici infection steps.

Impact of Meloidogyne incognita on Physiological Efficiency of Vitis vinifera.

PubMed

Melakeberhan, H; Ferris, H

1989-01-01

Four-week-old French Colombard plants rooted from green cuttings were inoculated with 0, 1,000, 2,000, 4,000, or 8,000 Meloidogyne incognita second-stage juveniles and maintained at 25 C night and 30 C day. Leaf area and dry weight and the rates of photosynthesis, stomatal conductance, and internal leaf CO concentration were measured at intervals up to 59 days after inoculation. Nematode stress dosage, measured as the product of cumulative number of juveniles and females and their total energy (calories) demand, was up to 3.4 kcal and accounted for up to 15% of the energy assimilated by the plants. There was a decline in the rate of leaf area expansion and leaf, stem, shoot, root (excluding nematode weight), and total plant dry weight with increasing nematode stress. Root weight including nematodes was not affected. Total respiration, plant photosynthesis, energy assimilated into plant tissue and respiration, and gross production efficiency decreased significantly with nematode stress. Photosynthetic rate, transpiration rate, stomatal conductance, and internal CO concentration were not affected. This study demonstrates that the energy demand for growth and reproduction of M. incognita accounts for a significant portion of the total energy entering the plant system. As a result, less energy is partitioned into leaf area expansion which, in turn, affects the energy entering the system and results in decreased productivity of nematode-infected grape vines.

Growth Effect of Cinnamomum kanehirae Cuttings Associated with its Dark Septate Endophytes.

PubMed

Lin, Lei-Chen

Stout camphor tree (Cinnamomum kanehirae Hay.) is an endemic specie in Taiwan and cutting is the major propagation of C. kanehirae for plantation. Mycorrhiza can accelerate the growth of the host plant, especially in root of the host plant. The objective of this study was to investigate the growth effect of the 2 dark septate endophytes isolated from C. kanehirae. To measure the effects of stains CkDB2 and CkDB5 on growth performance of cuttings, the cuttings were carefully removed from their substrate after 9 months of incubation. Each treatment had three replicates. After 9 month incubation, the mycorrhizal synthesis experiment showed that the roots of synthesized cuttings produced microsclerotia, a characteristic of dark septate endophyte, but nothing was found in the control. All inoculated cuttings had higher values of net height growth, dry weight, leaf area and chlorophyll concentration than the control. This study demonstrated that the 2 endophytes, strains CkDB2 and CkDB5, capable of forming microsclerotia with C. kanehirae cuttings were dark septate endophytes. Based on the results, CkDB5 had a better growth response than CkDB2. Cuttings inoculated with CkDB5 showed a 200% increase in the root dry weight and therefore, CkDB5 could presumably be a prerequisite for the survival of C. kanehirae cutting plantation.

Differential response of kabuli and desi chickpea genotypes toward inoculation with PGPR in different soils

PubMed Central

Imran, Asma; Mirza, Muhammad S.; Shah, Tariq M.; Malik, Kauser A.; Hafeez, Fauzia Y.

2015-01-01

Pakistan is among top three chickpea producing countries but the crop is usually grown on marginal lands without irrigation and fertilizer application which significantly hampers its yield. Soil fertility and inoculation with beneficial rhizobacteria play a key role in nodulation and yield of legumes. Four kabuli and six desi chickpea genotypes were, therefore, evaluated for inoculation response with IAA-producing Ochrobactrum ciceri Ca-34T and nitrogen fixing Mesorhizobium ciceri TAL-1148 in single and co-inoculation in two soils. The soil type 1 was previously unplanted marginal soil having low organic matter, P and N contents compared to soil type 2 which was a fertile routinely legume-cultivated soil. The effect of soil fertility status was pronounced and fertile soil on average, produced 31% more nodules, 62% more biomass and 111% grain yield than marginal soil. Inoculation either with O. ciceri alone or its co-inoculation with M. ciceri produced on average higher nodules (42%), biomass (31%), grains yield (64%) and harvest index (72%) in both chickpea genotypes over non-inoculated controls in both soils. Soil 1 showed maximum relative effectiveness of Ca-34T inoculation for kabuli genotypes while soil 2 showed for desi genotypes except B8/02. Desi genotype B8/02 in soil type 1 and Pb-2008 in soil type 2 showed significant yield increase as compared to respective un-inoculated controls. Across bacterial inoculation treatments, grain yield was positively correlated to growth and yield contributing parameters (r = 0.294* to 0.838*** for desi and r = 0.388* to 0.857** for kabuli). PCA and CAT-PCA analyses clearly showed a site-specific response of genotype x bacterial inoculation. Furthermore, the inoculated bacterial strains were able to persist in the rhizosphere showing colonization on root and within nodules. Present study shows that plant growth promoting rhizobacteria (PGPR) inoculation should be integrated with national chickpea breading program in Pakistan especially for marginal soils. Furthermore, the study shows the potential of phytohormone producing strain Ca-34T as promising candidate for development of biofertilizer alongwith nodulating strains to get sustainable yield of kabuli and desi chickpea with minimum inputs at marginal land. PMID:26379638

Soil-agrochemical aspects of remediation of a gray forest soil polluted with Pb upon the application of growth-promoting rhizobacteria

NASA Astrophysics Data System (ADS)

Shabaev, V. P.

2012-05-01

The effect of inoculation with growth-promoting rhizobacteria of the Pseudomonas genus on the growth and elemental composition of barley was examined in pot experiments with an artificially Pb-contaminated gray forest soil. The application of the bacteria to the contaminated soil enhanced the plant growth, increased the yield (including the grain yield) by 1.5 times, and considerably reduced the concentration of Pb in the plants without altering the soil reaction. The maximum effect was found upon the inoculation with the bacterium P. fluorescens 21, which ensures the same yield as that in the unpolluted soil without the application of bacteria and without changes in the grain quality (the protein content and the elemental composition). The positive effect of the bacteria was manifested to the greatest degree at the beginning and in the first half of the growing period and was associated with considerable binding of Pb in the soil compounds extractable with an ammonium acetate buffer solution. The elimination of the toxic effect and weakening of the Pb translocation in the barley plants after the inoculation with bacteria occurred due to the improvement in the mineral nutrition of the plants, the intensification of their barrier functions at the shoot-root and root-soil interfaces, the biological dilution caused by an increase in the plant biomass, and changes in the bioavailability of the metal (probably, under the influence of exometabolites produced by bacteria). The application of bacteria did not affect the removal of Pb from the soil by the plants (the biological remediation of the soil via phytoextraction of the toxicants).

Lupinus albus plants acquire mercury tolerance when inoculated with an Hg-resistant Bradyrhizobium strain.

PubMed

Quiñones, Miguel A; Ruiz-Díez, Beatriz; Fajardo, Susana; López-Berdonces, Miguel A; Higueras, Pablo L; Fernández-Pascual, Mercedes

2013-12-01

One strain of Bradyrhizobium canariense (L-7AH) was selected for its metal-resistance and ability to nodulate white lupin (Lupinus albus L.) plants, from a collection of rhizobial strains previously created from soils of the Almadén mining district (Spain) with varying levels of Hg contamination. Plants were inoculated with either strain L-7AH (Hg-tolerant) or L-3 (Hg-sensitive, used as control), and watered with nutrient solutions supplemented with various concentrations (0-200 μM) of HgCl2 in a growth chamber. L. albus inoculated with L-7AH were able to nodulate even at the highest concentration of Hg while those inoculated with L-3 had virtually no nodules at Hg concentrations above 25 μM. Plants inoculated with L-7AH, but not those with the control strain, were able to accumulate large amounts of Hg in their roots and nodules. Nodulation with L-7AH allowed plants to maintain constant levels of both chlorophylls and carotenoids in their leaves and a high photosynthetic efficiency, whereas in those inoculated with L-3 both pigment content and photosynthetic efficiency decreased significantly as Hg concentration increased. Nitrogenase activity of plants nodulated with L-7AH remained fairly constant at all concentrations of Hg used. Results suggest that this symbiotic pair may be used for rhizoremediation of Hg-contaminated soils. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Native root-associated bacteria rescue a plant from a sudden-wilt disease that emerged during continuous cropping

PubMed Central

Santhanam, Rakesh; Luu, Van Thi; Weinhold, Arne; Goldberg, Jay; Oh, Youngjoo; Baldwin, Ian T.

2015-01-01

Plants maintain microbial associations whose functions remain largely unknown. For the past 15 y, we have planted the annual postfire tobacco Nicotiana attenuata into an experimental field plot in the plant’s native habitat, and for the last 8 y the number of plants dying from a sudden wilt disease has increased, leading to crop failure. Inadvertently we had recapitulated the common agricultural dilemma of pathogen buildup associated with continuous cropping for this native plant. Plants suffered sudden tissue collapse and black roots, symptoms similar to a Fusarium–Alternaria disease complex, recently characterized in a nearby native population and developed into an in vitro pathosystem for N. attenuata. With this in vitro disease system, different protection strategies (fungicide and inoculations with native root-associated bacterial and fungal isolates), together with a biochar soil amendment, were tested further in the field. A field trial with more than 900 plants in two field plots revealed that inoculation with a mixture of native bacterial isolates significantly reduced disease incidence and mortality in the infected field plot without influencing growth, herbivore resistance, or 32 defense and signaling metabolites known to mediate resistance against native herbivores. Tests in a subsequent year revealed that a core consortium of five bacteria was essential for disease reduction. This consortium, but not individual members of the root-associated bacteria community which this plant normally recruits during germination from native seed banks, provides enduring resistance against fungal diseases, demonstrating that native plants develop opportunistic mutualisms with prokaryotes that solve context-dependent ecological problems. PMID:26305938

Inoculation with arbuscular mycorrhizal fungi and addition of composted olive-mill waste enhance plant establishment and soil properties in the regeneration of a heavy metal-polluted environment.

PubMed

Curaqueo, Gustavo; Schoebitz, Mauricio; Borie, Fernando; Caravaca, Fuensanta; Roldán, Antonio

2014-06-01

A greenhouse experiment was carried out in order to investigate the effects of arbuscular mycorrhizal (AM) fungi inoculation and the use of composted olive waste (COW) in the establishment of Tetraclinis articulata and soil properties in a heavy metal-polluted soil. The treatments assayed were as follows: AM + 0% COW, AM + 1% COW, and AM + 3% COW. The higher doses of COW in combination with AM fungi increased shoot and root biomass production of T. articulata by 96 and 60%, respectively. These treatments trended to improve the soil properties evaluated, highlighting the C compounds and N as well as the microbiological activities. In relation to the metal translocation in T. articulata, doses of COW applied decreased the Cr, Ni, and Pb contents in shoot, as well as Cr and As in root, although the most of them reached low levels and far from phytotoxic. The COW amendment aided Glomus mosseae-inoculated T. articulata plants to thrive in contaminated soil, mainly through an improvement in both nutrients uptake, mainly P and soil microbial function. In addition, the combined use of AM fungi plus COW could be a feasible strategy to be incorporated in phytoremediation programs because it promotes soil properties, a better performance of plants for supporting the stress in heavy metal-contaminated soils derived from the mining process, and also can be a good way for olive-mill waste disposal.

Enhancement of Thiamine Biosynthesis in Oil Palm Seedlings by Colonization of Endophytic Fungus Hendersonia toruloidea

PubMed Central

Kamarudin, Amirah N.; Lai, Kok S.; Lamasudin, Dhilia U.; Idris, Abu S.; Balia Yusof, Zetty N.

2017-01-01

Thiamine, or vitamin B1 plays an indispensable role as a cofactor in crucial metabolic reactions including glycolysis, pentose phosphate pathway and the tricarboxylic acid cycle in all living organisms. Thiamine has been shown to play a role in plant adaptation toward biotic and abiotic stresses. The modulation of thiamine biosynthetic genes in oil palm seedlings was evaluated in response to root colonization by endophytic Hendersonia toruloidea. Seven-month-old oil palm seedlings were inoculated with H. toruloidea and microscopic analyses were performed to visualize the localization of endophytic H. toruloidea in oil palm roots. Transmission electron microscopy confirmed that H. toruloidea colonized cortical cells. The expression of thiamine biosynthetic genes and accumulation of total thiamine in oil palm seedlings were also evaluated. Quantitative real-time PCR was performed to measure transcript abundances of four key thiamine biosynthesis genes (THI4, THIC, TH1, and TPK) on days 1, 7, 15, and 30 in response to H. toruloidea colonization. The results showed an increase of up to 12-fold in the expression of all gene transcripts on day 1 post-inoculation. On days 7, 15, and 30 post-inoculation, the relative expression levels of these genes were shown to be downregulated. Thiamine accumulation was observed on day 7 post-colonization and subsequently decreased until day 30. This work provides the first evidence for the enhancement of thiamine biosynthesis by endophytic colonization in oil palm seedlings. PMID:29089959

Enhancement of Thiamine Biosynthesis in Oil Palm Seedlings by Colonization of Endophytic Fungus Hendersonia toruloidea.

PubMed

Kamarudin, Amirah N; Lai, Kok S; Lamasudin, Dhilia U; Idris, Abu S; Balia Yusof, Zetty N

2017-01-01

Thiamine, or vitamin B1 plays an indispensable role as a cofactor in crucial metabolic reactions including glycolysis, pentose phosphate pathway and the tricarboxylic acid cycle in all living organisms. Thiamine has been shown to play a role in plant adaptation toward biotic and abiotic stresses. The modulation of thiamine biosynthetic genes in oil palm seedlings was evaluated in response to root colonization by endophytic Hendersonia toruloidea . Seven-month-old oil palm seedlings were inoculated with H. toruloidea and microscopic analyses were performed to visualize the localization of endophytic H. toruloidea in oil palm roots. Transmission electron microscopy confirmed that H. toruloidea colonized cortical cells. The expression of thiamine biosynthetic genes and accumulation of total thiamine in oil palm seedlings were also evaluated. Quantitative real-time PCR was performed to measure transcript abundances of four key thiamine biosynthesis genes ( THI4 , THIC , TH1 , and TPK ) on days 1, 7, 15, and 30 in response to H. toruloidea colonization. The results showed an increase of up to 12-fold in the expression of all gene transcripts on day 1 post-inoculation. On days 7, 15, and 30 post-inoculation, the relative expression levels of these genes were shown to be downregulated. Thiamine accumulation was observed on day 7 post-colonization and subsequently decreased until day 30. This work provides the first evidence for the enhancement of thiamine biosynthesis by endophytic colonization in oil palm seedlings.

Inoculation of Schizolobium parahyba with Mycorrhizal Fungi and Plant Growth-Promoting Rhizobacteria Increases Wood Yield under Field Conditions.

PubMed

Cely, Martha V T; Siviero, Marco A; Emiliano, Janaina; Spago, Flávia R; Freitas, Vanessa F; Barazetti, André R; Goya, Erika T; Lamberti, Gustavo de Souza; Dos Santos, Igor M O; De Oliveira, Admilton G; Andrade, Galdino

2016-01-01

Schizolobium parahyba var. amazonicum (Huber ex Ducke) occurs naturally in the Brazilian Amazon. Currently, it is being planted extensively because of its fast growth and excellent use in forestry. Consequently, there is great interest in new strategies to increase wood production. The interaction between soil microorganisms and plants, specifically in the roots, provides essential nutrients for plant growth. These interactions can have growth-promoting effects. In this way, this study assessed the effect of the inoculation with arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) on growth of S. parahyba var. amazonicum under field conditions. We used two native species of arbuscular mycorrhizal fungi, Claroideoglomus etunicatum (Ce), and Acaulospora sp. (Ac); two native strains of Rhizobium sp. (Rh1 and Rh2); and a non-native strain of Burkholderia sp. Different combinations of microorganisms were supplemented with chemical fertilizers (doses D1 and D2) in two planting methods, seed sowing and seedling planting. In seed sowing, the results showed that treatments with Ce/Rh1/Fertilizer D2 and Ac/No PGPR/Fertilizer D2 increased wood yield. In seedling planting, two combinations (Ac/Rh2/Fertilizer D1 and Ac/Rh1/Fertilizer D1) were more effective in increasing seedling growth. In these experiments, inoculation with AMF and PGPR increased wood yield by about 20% compared to the application of fertilizer alone.

Inoculation of Schizolobium parahyba with Mycorrhizal Fungi and Plant Growth-Promoting Rhizobacteria Increases Wood Yield under Field Conditions

PubMed Central

Cely, Martha V. T.; Siviero, Marco A.; Emiliano, Janaina; Spago, Flávia R.; Freitas, Vanessa F.; Barazetti, André R.; Goya, Erika T.; Lamberti, Gustavo de Souza; dos Santos, Igor M. O.; De Oliveira, Admilton G.; Andrade, Galdino

2016-01-01

Schizolobium parahyba var. amazonicum (Huber ex Ducke) occurs naturally in the Brazilian Amazon. Currently, it is being planted extensively because of its fast growth and excellent use in forestry. Consequently, there is great interest in new strategies to increase wood production. The interaction between soil microorganisms and plants, specifically in the roots, provides essential nutrients for plant growth. These interactions can have growth-promoting effects. In this way, this study assessed the effect of the inoculation with arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) on growth of S. parahyba var. amazonicum under field conditions. We used two native species of arbuscular mycorrhizal fungi, Claroideoglomus etunicatum (Ce), and Acaulospora sp. (Ac); two native strains of Rhizobium sp. (Rh1 and Rh2); and a non-native strain of Burkholderia sp. Different combinations of microorganisms were supplemented with chemical fertilizers (doses D1 and D2) in two planting methods, seed sowing and seedling planting. In seed sowing, the results showed that treatments with Ce/Rh1/Fertilizer D2 and Ac/No PGPR/Fertilizer D2 increased wood yield. In seedling planting, two combinations (Ac/Rh2/Fertilizer D1 and Ac/Rh1/Fertilizer D1) were more effective in increasing seedling growth. In these experiments, inoculation with AMF and PGPR increased wood yield by about 20% compared to the application of fertilizer alone. PMID:27920781

Arbuscular mycorrhizal fungi are an alternative to the application of chemical fertilizer in the production of the medicinal and aromatic plant Coriandrum sativum L.

PubMed

Oliveira, Rui S; Ma, Ying; Rocha, Inês; Carvalho, Maria F; Vosátka, Miroslav; Freitas, Helena

2016-01-01

The widespread use of agrochemicals is detrimental to the environment and may exert harmful effects on human health. The consumer demand for organic food plants has been increasing. There is thus a rising need for alternatives to agrochemicals that can foster sustainable plant production. The aim of this study was to evaluate the potential use of an arbuscular mycorrhizal (AM) fungus as an alternative to application of chemical fertilizer for improving growth performance of the medicinal and aromatic plant Coriandrum sativum. Plants were inoculated with the AM fungus Rhizophagus irregularis BEG163 and/or supplemented with a commercial chemical fertilizer (Plant Marvel, Nutriculture Bent Special) in agricultural soil. Plant growth, nutrition, and development of AM fungus were assessed. Plants inoculated with R. irregularis and those supplemented with chemical fertilizer displayed significantly improved growth performances when compared with controls. There were no significant differences in total fresh weight between plants inoculated with R. irregularis or those supplemented with chemical fertilizer. Leaf chlorophyll a + b (82%), shoot nitrogen (44%), phosphorus (254%), and potassium (27%) concentrations increased in plants inoculated with R. irregularis compared to controls. Application of chemical fertilizer inhibited root mycorrhizal colonization and the length of the extraradical mycelium of R. irregularis. Inoculation with R. irregularis was equally or more efficient than application of chemical fertilizer in promoting growth and nutrition of C. sativum. AM fungi may thus contribute to improve biologically based production of food plants and reduce the dependence on agrochemicals in agriculture.

Seed coating with arbuscular mycorrhizal fungi as an ecotechnologicalapproach for sustainable agricultural production of common wheat (Triticum aestivum L.).

PubMed

Oliveira, Rui S; Rocha, Inês; Ma, Ying; Vosátka, Miroslav; Freitas, Helena

2016-01-01

The exploitation of arbuscular mycorrhizal (AM) fungi has become of great interest in agriculture due to their potential roles in reducing the need for agrochemicals, while improving plant growth and nutrition. Nevertheless, the application of AM fungi by dispersing inocula in granular form to open agricultural fields is not feasible because nontargeted spreading of inocula over large surface areas results in high cost per plant. Seed coating has the potential to significantly reduce the amount of inoculum needed, resulting in cost reduction and increased efficiency. The aim of this study was to assess whether seed coating with AM fungal inoculum is a feasible delivery system for production of common wheat (Triticum aestivum L.). Wheat seeds were coated with inoculum of Rhizophagus irregularis BEG140 and grown under different fertilization conditions: (1) none, (2) partial, or (3) complete. Data indicated that mycorrhizal inoculation via seed coating significantly increased the dry weight of shoot and seed spikes of wheat associated with reduced fertilization. Assessment of nutritional status of wheat showed that plants inoculated with R. irregularis via seed coating displayed enhanced stem concentrations of potassium (K), sulfur (S), and zinc (Zn). There were no significant differences in root colonization between plants conventionally inoculated with R. irregularis in soil and those inoculated via seed coating. Seed coating with AM fungi may be as effective as conventional soil inoculation and may contribute to reduce the utilization of chemical fertilizers. The application of AM via seed coating is proposed as an ecotechnological approach for sustainable agricultural wheat production.

Cell Wall Localization of Two DUF642 Proteins, BIIDXI and TEEBE, during Meloidogyne incognita Early Inoculation

PubMed Central

Salazar-Iribe, Alexis; Zúñiga-Sánchez, Esther; Mejía, Emma Zavaleta; Gamboa-deBuen, Alicia

2017-01-01

The root-knot nematode Meloidogyne incognita infects a variety of plants, including Arabidopsis thaliana. During migration, root-knot nematodes secrete different proteins to modify cell walls, which include pectolytic enzymes. However, the contribution of host cell wall proteins has not been described during this process. The function of two DUF642 cell wall proteins, BIIDXI (BDX, At4g32460) and TEEBE (TEB, At2g41800), in plant development could be related to the regulation of pectin methyl esterification status in the cell walls of different tissues. Accordingly, the expression of these two genes is up-regulated by auxin. BDX and TEB were highly induced during early M. incognita inoculation. Moreover, cell wall localization of the proteins was also induced. The cell wall localization of BDX and TEB DUF642 proteins during M. incognita early inoculation suggested that these two proteins could be involved in the regulation of the degree of pectin methylation during cell separation. PMID:29238286

Can ectomycorrhizal symbiosis and belowground plant traits be used as ecological tools to mitigate erosion on degraded slopes in the ultramafic soils of New Caledonia?

NASA Astrophysics Data System (ADS)

Demenois, Julien; Carriconde, Fabian; Rey, Freddy; Stokes, Alexia

2015-04-01

New Caledonia is an archipelago in the South West Pacific located just above the Tropic of Capricorn. The main island is bisected by a continuous mountain chain whose highest peaks reach more than 1 600 m. With mean annual rainfall above 2 000 mm in the South of the main island, frequent downpours and steep slopes, its soils are prone to water erosion. Deforestation, fires and mining activity are the main drivers of water erosion. Stakes are high to mitigate the phenomenon: extraction of nickel from ultramafic substrates (one third of the whole territory) is the main economic activity; New Caledonia is considered as a biodiversity hotspot. Restoration ecology is seen as a key approach for tackling such environmental challenges. Soil microorganisms could play significant roles in biological processes such as plant nutrition and plant resistance to abiotic and biotic stresses. Microorganisms could increase soil aggregate stability and thus mitigate soil erodibility. Plant roots increase soil cohesion through exudation and decomposition processes. To date, few studies have collected data on the soil aggregate stability of steep slopes affected by erosion and, to our knowledge, interactions between ectomycorrhizas (ECM), roots and erodibility of ultramafic soils have never been considered. The objective of our study is to assess the influence of ECM symbiosis and plant root traits on the erodibility of ultramafic soils of New Caledonia and answer the following questions: 1/ What is the influence of plant root traits of vegetal communities and ECM fungal diversity on soil erodibility? 2/ What are the belowground plant traits of some mycorrhized endemic species used in ecological restoration? 3/ What is the influence of plant root traits and ECM fungal inoculation on soil erodibility? At the scale of plant communities, five types of vegetation have been chosen in the South of the main island: degraded ligno-herbaceous shrubland, ligno-herbaceous shrubland, degraded humid forest with dominance of Arillastrum gummiferum, dense humid forest with dominance of Nothofagus aequilateralis, and finally mixed dense humid forest. These types of vegetation are widely represented on ultramafic soils of New Caledonia and are likely to correspond to different successional phases. At the scale of species, dominant species in the above-mentioned types of vegetation are considered for herbaceous, shrubs and trees strata. Root traits of Costularia nervosa, Tristaniopsis glauca, Nothofagus aequilateralis and Arillastrum gummiferum are then characterized in situ. These species are of particular interest for post-mining ecological restoration in New Caledonia as they are light-tolerant, endemic, associated with ECM (except for Costularia nervosa) and of particular interest or already used by mining operators for post-mining ecological restoration. For both scales (community and species), soil characteristics will be collected. Very fine and fine roots, mean root diameter, root diameter diversity, root mass density, root length density, and specific root length will be considered. Degree of ectomycorrhization and fungal biomass through qPCR will be determined. Soil aggregate stability will be measured according to the standardized method NF X 31-515. Besides, greenhouse trials with Costularia nervosa, Tristaniopsis glauca and Arillastrum gummiferum are carried out to assess the influence of plant root traits, fungal inoculation and soil aggregate stability. Controlled plant inoculations are performed using available pure fungal strains isolated from New Caledonian ultramafic soils. Plants have been bred on sterilized soil samples from the field sites. Through this study, we target to identify associations between ECM fungi and plant species that could mitigate the erodibility of degraded ultramafic soils and then water erosion. A better knowledge of interactions between soil aggregate stability, ECM fungi and plant root traits is then expected to answer the following question: can soil aggregate stability be used as a bio-indicator of ecosystem functioning and services?

Phylogenetically diverse AM fungi from Ecuador strongly improve seedling growth of native potential crop trees.

PubMed

Schüßler, Arthur; Krüger, Claudia; Urgiles, Narcisa

2016-04-01

In many deforested regions of the tropics, afforestation with native tree species could valorize a growing reservoir of degraded, previously overused and abandoned land. The inoculation of tropical tree seedlings with arbuscular mycorrhizal fungi (AM fungi) can improve tree growth and viability, but efficiency may depend on plant and AM fungal genotype. To study such effects, seven phylogenetically diverse AM fungi, native to Ecuador, from seven genera and a non-native AM fungus (Rhizophagus irregularis DAOM197198) were used to inoculate the tropical potential crop tree (PCT) species Handroanthus chrysanthus (synonym Tabebuia chrysantha), Cedrela montana, and Heliocarpus americanus. Twenty-four plant-fungus combinations were studied in five different fertilization and AMF inoculation treatments. Numerous plant growth parameters and mycorrhizal root colonization were assessed. The inoculation with any of the tested AM fungi improved seedling growth significantly and in most cases reduced plant mortality. Plants produced up to threefold higher biomass, when compared to the standard nursery practice. AM fungal inoculation alone or in combination with low fertilization both outperformed full fertilization in terms of plant growth promotion. Interestingly, root colonization levels for individual fungi strongly depended on the host tree species, but surprisingly the colonization strength did not correlate with plant growth promotion. The combination of AM fungal inoculation with a low dosage of slow release fertilizer improved PCT seedling performance strongest, but also AM fungal treatments without any fertilization were highly efficient. The AM fungi tested are promising candidates to improve management practices in tropical tree seedling production.

Direct plantlet inoculation with soil or insect-associated fungi may control cabbage root fly maggots.

PubMed

Razinger, Jaka; Lutz, Matthias; Schroers, Hans-Josef; Palmisano, Marilena; Wohler, Christian; Urek, Gregor; Grunder, Jürg

2014-07-01

A potential Delia radicum biological control strategy involving cauliflower plantlet inoculation with various fungi was investigated in a series of laboratory and glasshouse experiments. In addition to entomopathogenic fungi, fungi with a high rhizosphere competence and fungi with the ability to survive as saprotrophs in soil were tested. The following fungal species were evaluated in the experiments: Trichoderma atroviride, T. koningiopsis, T. gamsii, Beauveria bassiana, Metharhizium anisopliae, M. brunneum and Clonostachys solani. A commercial carbosulfan-based insecticide was used as a positive control. Additionally, two commercial products, one based on B. bassiana (Naturalis) and one on Bacillus thuringiensis (Delfin) were used as reference biocontrol agents. The aims were (i) to assess the pathogenicity of the selected fungal isolates to Delia radicum, (ii) to evaluate the fungal isolates' rhizosphere competence, with the emphasis on the persistence of the original inoculum on the growing roots, (iii) to assess possible endophytic plant tissue colonization, and (iv) to evaluate potential plant growth stimulating effects of the added inoculi. Significant pathogenicity of tested fungi against Delia radicum was confirmed in in vitro and glasshouse experiments. All tested fungi persisted on cauliflower rhizoplane. More importantly, the added fungi were found on thoroughly washed roots outside the original point of inoculation. This provided us with evidence that our tested fungi could be transferred via or grow with the elongating roots. In addition to colonizing the rhizoplane, some fungi were found inside the plant root or stem tissue, thus exhibiting endophytic characteristics. The importance of fungal ecology as a criterion in appropriate biological control agent selection is discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

Reference gene selection for quantitative real-time PCR in Solanum lycopersicum L. inoculated with the mycorrhizal fungus Rhizophagus irregularis.

PubMed

Fuentes, Alejandra; Ortiz, Javier; Saavedra, Nicolás; Salazar, Luis A; Meneses, Claudio; Arriagada, Cesar

2016-04-01

The gene expression stability of candidate reference genes in the roots and leaves of Solanum lycopersicum inoculated with arbuscular mycorrhizal fungi was investigated. Eight candidate reference genes including elongation factor 1 α (EF1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase (PGK), protein phosphatase 2A (PP2Acs), ribosomal protein L2 (RPL2), β-tubulin (TUB), ubiquitin (UBI) and actin (ACT) were selected, and their expression stability was assessed to determine the most stable internal reference for quantitative PCR normalization in S. lycopersicum inoculated with the arbuscular mycorrhizal fungus Rhizophagus irregularis. The stability of each gene was analysed in leaves and roots together and separated using the geNorm and NormFinder algorithms. Differences were detected between leaves and roots, varying among the best-ranked genes depending on the algorithm used and the tissue analysed. PGK, TUB and EF1 genes showed higher stability in roots, while EF1 and UBI had higher stability in leaves. Statistical algorithms indicated that the GAPDH gene was the least stable under the experimental conditions assayed. Then, we analysed the expression levels of the LePT4 gene, a phosphate transporter whose expression is induced by fungal colonization in host plant roots. No differences were observed when the most stable genes were used as reference genes. However, when GAPDH was used as the reference gene, we observed an overestimation of LePT4 expression. In summary, our results revealed that candidate reference genes present variable stability in S. lycopersicum arbuscular mycorrhizal symbiosis depending on the algorithm and tissue analysed. Thus, reference gene selection is an important issue for obtaining reliable results in gene expression quantification. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Bacterial antagonists of fungal pathogens also control root-knot nematodes by induced systemic resistance of tomato plants.

PubMed

Adam, Mohamed; Heuer, Holger; Hallmann, Johannes

2014-01-01

The potential of bacterial antagonists of fungal pathogens to control the root-knot nematode Meloidogyne incognita was investigated under greenhouse conditions. Treatment of tomato seeds with several strains significantly reduced the numbers of galls and egg masses compared with the untreated control. Best performed Bacillus subtilis isolates Sb4-23, Mc5-Re2, and Mc2-Re2, which were further studied for their mode of action with regard to direct effects by bacterial metabolites or repellents, and plant mediated effects. Drenching of soil with culture supernatants significantly reduced the number of egg masses produced by M. incognita on tomato by up to 62% compared to the control without culture supernatant. Repellence of juveniles by the antagonists was shown in a linked twin-pot set-up, where a majority of juveniles penetrated roots on the side without inoculated antagonists. All tested biocontrol strains induced systemic resistance against M. incognita in tomato, as revealed in a split-root system where the bacteria and the nematodes were inoculated at spatially separated roots of the same plant. This reduced the production of egg masses by up to 51%, while inoculation of bacteria and nematodes in the same pot had only a minor additive effect on suppression of M. incognita compared to induced systemic resistance alone. Therefore, the plant mediated effect was the major reason for antagonism rather than direct mechanisms. In conclusion, the bacteria known for their antagonistic potential against fungal pathogens also suppressed M. incognita. Such "multi-purpose" bacteria might provide new options for control strategies, especially with respect to nematode-fungus disease complexes that cause synergistic yield losses.

Total growth and root-cluster production by legumes and proteas depends on rhizobacterial strain, host species and nitrogen level

PubMed Central

Lamont, Byron B.; Pérez-Fernández, María

2016-01-01

Background Root clusters are bunches of hairy rootlets produced by >1800 species in nine families. The possible involvement of micro-organisms in root-cluster formation has produced conflicting results over the last 40 years. In addition, any effect of rhizobacteria on overall plant growth of root-cluster-bearing species remains unknown. Aims To evaluate the effect of seven rhizobacteria on total plant size, and relative cluster production, by three species, and relate outcomes to their indole-3-acetic acid (IAA)-producing ability as part explanation of past disparate results. Methods We grew Leucadendron salicifolium (from South Africa), Viminaria juncea (Australia) and Lupinus albus (Europe) in gnotobiotic, hydroponic culture at two nitrogen (N) levels and inoculated them with seven bacterial strains and harvested the plants after 13 weeks. Key Results Following inoculation with all seven bacteria individually, plant growth sometimes greatly exceeded that of the aseptic controls, but, under other conditions, growth was less than the controls. Leucadendron and Lupinus failed to produce root clusters in the –N aseptic controls and Viminaria in the +N controls that was overcome by inoculating them with selected bacteria. Six bacteria were able to induce far more root clusters than those of the aseptic controls, while all bacteria sometimes suppressed cluster production in other treatments. All nine possible combinations of resource (plant size, indirect) and morphogenetic (relative cluster production, direct) effects were represented among the results, especially positive synergism (larger plants with a greater density of clusters). There was no clear relationship with IAA-producing ability of the seven bacteria, but low IAA strains of Pseudomonas putida and Bacillus magetarium were associated with greatest cluster production. Conclusions While root-cluster formation can sometimes be induced by introducing rhizobacteria to aseptic culture, the growth-promoting properties of apparently beneficial bacteria on general growth and root-cluster production are best described as facultative, as their promotory effects depend on host species, growing conditions and index of plant response used. PMID:27288511

Phytoprotective effect of arbuscular mycorrhizal fungi species against arsenic toxicity in tropical leguminous species.

PubMed

de Melo, Rangel Wesley; Schneider, Jerusa; de Souza, Costa Enio Tarso; Sousa, Soares Cláudio Roberto Fonsêca; Guimarães, Guilherme Luiz Roberto; de Souza, Moreira Fatima Maria

2014-01-01

Arbuscular mycorrhizal fungi (AMF) improve the tolerance of hosting plants to arsenic (As) in contaminated soils. This work assessed the phytoprotective effect of Glomus etunicatum, Acaulospora morrowiae, Gigaspora gigantea, and Acaulospora sp. on four leguminous species (Acacia mangium, Crotalaria juncea, Enterolobium contortisiliquum, and Stizolobium aterrimum) in an As-contaminated soil from a gold mining area. AMF root colonization, biomass production, As and P accumulation, as well as arsenic translocation index (TI) from roots to shoots were measured. The AMF phytoprotective effect was assessed by the P/As ratio and the activity of plant antioxidant enzymes. The AMF colonization ranged from 24 to 28%. In general, all leguminous species had low As TI when inoculated with AMF species. Inoculation of C. juncea with Acaulospora sp. improved significantly As accumulation in roots, and decreased the activity of ascorbate peroxidase (APX) and superoxide dismutase (SOD), highlighting its phytoprotective effect and the potential use of this symbiosis for phytoremediation of As-contaminated soils. However, S. aterrimum has also shown a potential for phytoremediation irrespectively of AMF inoculation. APX was a good indicator of the phytoprotective effect against As contamination in C. juncea and A. mangium. In general P/As ratio in shoots was the best indicator of the phytoprotective effect of all AMF species in all plant species.

Molecular Signals Controlling the Inhibition of Nodulation by Nitrate in Medicago truncatula

PubMed Central

van Noorden, Giel E.; Verbeek, Rob; Dinh, Quy Dung; Jin, Jian; Green, Alexandra; Ng, Jason Liang Pin; Mathesius, Ulrike

2016-01-01

The presence of nitrogen inhibits legume nodule formation, but the mechanism of this inhibition is poorly understood. We found that 2.5 mM nitrate and above significantly inhibited nodule initiation but not root hair curling in Medicago trunatula. We analyzed protein abundance in M. truncatula roots after treatment with either 0 or 2.5 mM nitrate in the presence or absence of its symbiont Sinorhizobium meliloti after 1, 2 and 5 days following inoculation. Two-dimensional gel electrophoresis combined with mass spectrometry was used to identify 106 differentially accumulated proteins responding to nitrate addition, inoculation or time point. While flavonoid-related proteins were less abundant in the presence of nitrate, addition of Nod gene-inducing flavonoids to the Sinorhizobium culture did not rescue nodulation. Accumulation of auxin in response to rhizobia, which is also controlled by flavonoids, still occurred in the presence of nitrate, but did not localize to a nodule initiation site. Several of the changes included defense- and redox-related proteins, and visualization of reactive oxygen species indicated that their induction in root hairs following Sinorhizobium inoculation was inhibited by nitrate. In summary, the presence of nitrate appears to inhibit nodulation via multiple pathways, including changes to flavonoid metabolism, defense responses and redox changes. PMID:27384556

Enhanced root and shoot growth of wheat (Triticum aestivum L.) by Trichoderma harzianum from Turkey.

PubMed

Kucuk, Cigdem

2014-01-01

It is well known that Trichoderma species can be used as biocontrol and plant growth promote agent. In this study, Trichoderma harzianum isolates were evaluated for their growth promotion effects on wheat in greenhouse experiments. Two isolates of T. harzianum were used. The experimental design was a randomized complete block with three replications. Seeds were inoculated with conidial suspensions of each isolate. Wheat plants grown in steriled soil in pots. T. harzianum T8 and T15 isolates increased wheat length, root dry weight and shoot dry weight according to untreated control. Turkish isolates T8 and T15 did not produce damage in seeds nor in plants.

Tomato ethylene sensitivity determines interaction with plant growth-promoting bacteria.

PubMed

Ibort, Pablo; Molina, Sonia; Núñez, Rafael; Zamarreño, Ángel María; García-Mina, José María; Ruiz-Lozano, Juan Manuel; Orozco-Mosqueda, Maria Del Carmen; Glick, Bernard R; Aroca, Ricardo

2017-07-01

Plant growth-promoting bacteria (PGPB) are soil micro-organisms able to interact with plants and stimulate their growth, positively affecting plant physiology and development. Although ethylene plays a key role in plant growth, little is known about the involvement of ethylene sensitivity in bacterial inoculation effects on plant physiology. Thus, the present study was pursued to establish whether ethylene perception is critical for plant-bacteria interaction and growth induction by two different PGPB strains, and to assess the physiological effects of these strains in juvenile and mature tomato ( Solanum lycopersicum ) plants. An experiment was performed with the ethylene-insensitive tomato never ripe and its isogenic wild-type line in which these two strains were inoculated with either Bacillus megaterium or Enterobacter sp. C7. Plants were grown until juvenile and mature stages, when biomass, stomatal conductance, photosynthesis as well as nutritional, hormonal and metabolic statuses were analysed. Bacillus megaterium promoted growth only in mature wild type plants. However, Enterobacter C7 PGPB activity affected both wild-type and never ripe plants. Furthermore, PGPB inoculation affected physiological parameters and root metabolite levels in juvenile plants; meanwhile plant nutrition was highly dependent on ethylene sensitivity and was altered at the mature stage. Bacillus megaterium inoculation improved carbon assimilation in wild-type plants. However, insensitivity to ethylene compromised B. megaterium PGPB activity, affecting photosynthetic efficiency, plant nutrition and the root sugar content. Nevertheless, Enterobacter C7 inoculation modified the root amino acid content in addition to stomatal conductance and plant nutrition. Insensitivity to ethylene severely impaired B. megaterium interaction with tomato plants, resulting in physiological modifications and loss of PGPB activity. In contrast, Enterobacter C7 inoculation stimulated growth independently of ethylene perception and improved nitrogen assimilation in ethylene-insensitive plants. Thus, ethylene sensitivity is a determinant for B. megaterium , but is not involved in Enterobacter C7 PGPB activity. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Pathogenicity of Nectriaceous Fungi on Avocado in Australia.

PubMed

Parkinson, Louisamarie E; Shivas, Roger G; Dann, Elizabeth K

2017-12-01

Black root rot is a severe disease of young avocado trees in Australia causing black necrotic roots, tree stunting, and leaf drop prior to tree death. Nectriaceous fungi (Nectriaceae, Hypocreales), are commonly isolated from symptomatic roots. This research tested the pathogenicity of 19 isolates from Calonectria, Cylindrocladiella, Dactylonectria, Gliocladiopsis, and Ilyonectria, spp. collected from young avocado trees and other hosts. Glasshouse pathogenicity tests with 'Reed' avocado (Persea americana) seedlings confirmed that Calonectria ilicicola is a severe pathogen of avocado, causing stunting, wilting, and seedling death within 5 weeks of inoculation. Isolates of C. ilicicola from peanut, papaya, and custard apple were also shown to be aggressive pathogens of avocado, demonstrating a broad host range. An isolate of a Calonectria sp. from blueberry and avocado isolates of Dactylonectria macrodidyma, D. novozelandica, D. pauciseptata, and D. anthuriicola caused significant root rot but not stunting within 5 to 9 weeks of inoculation. An isolate of an Ilyonectria sp. from grapevine closely related to Ilyonectria liriodendri, and avocado isolates of Cylindrocladiella pseudoinfestans, Gliocladiopsis peggii, and an Ilyonectria sp. were not pathogenic to avocado.

Possible evidence for contribution of arbuscular mycorrhizal fungi (AMF) in phytoremediation of iron-cyanide (Fe-CN) complexes.

PubMed

Sut, Magdalena; Boldt-Burisch, Katja; Raab, Thomas

2016-08-01

Arbuscular mycorrhizal fungi (AMF) are integral functioning parts of plant root systems and are widely recognized for enhancing contaminants uptake and metabolism on severely disturbed sites. However, the patterns of their influence on the phytoremediation of iron-cyanide (Fe-CN) complexes are unknown. Fe-CN complexes are of great common interest, as iron is one of the most abundant element in soil and water. Effect of ryegrass (Lolium perenne L.) roots inoculation, using mycorrhizal fungi (Rhizophagus irregularis and a mixture of R. irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum), on iron-cyanide sorption was studied. Results indicated significantly higher colonization of R. irregularis than the mixture of AMF species on ryegrass roots. Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations revealed significantly higher reduction of total CN and free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study is a first indication of the possible positive contribution of AM fungi on the phytoremediation of iron-cyanide complexes.

Nickel-tolerant ectomycorrhizal Pisolithus albus ultramafic ecotype isolated from nickel mines in New Caledonia strongly enhance growth of the host plant Eucalyptus globulus at toxic nickel concentrations.

PubMed

Jourand, Philippe; Ducousso, Marc; Reid, Robert; Majorel, Clarisse; Richert, Clément; Riss, Jennifer; Lebrun, Michel

2010-10-01

Ectomycorrhizal (ECM) Pisolithus albus (Cooke & Massee), belonging to the ultramafic ecotype isolated in nickel-rich serpentine soils from New Caledonia (a tropical hotspot of biodiversity) and showing in vitro adaptive nickel tolerance, were inoculated to Eucalyptus globulus Labill used as a Myrtaceae plant-host model to study ectomycorrhizal symbiosis. Plants were then exposed to a nickel (Ni) dose-response experiment with increased Ni treatments up to 60 mg kg( - )(1) soil as extractable Ni content in serpentine soils. Results showed that plants inoculated with ultramafic ECM P. albus were able to tolerate high and toxic concentrations of Ni (up to 60 μg g( - )(1)) while uninoculated controls were not. At the highest Ni concentration tested, root growth was more than 20-fold higher and shoot growth more than 30-fold higher in ECM plants compared with control plants. The improved growth in ECM plants was associated with a 2.4-fold reduction in root Ni concentration but a massive 60-fold reduction in transfer of Ni from root to shoots. In vitro, P. albus strains could withstand high Ni concentrations but accumulated very little Ni in its tissue. The lower Ni uptake by mycorrhizal plants could not be explained by increased release of metal-complexing chelates since these were 5- to 12-fold lower in mycorrhizal plants at high Ni concentrations. It is proposed that the fungal sheath covering the plant roots acts as an effective barrier to limit transfer of Ni from soil into the root tissue. The degree of tolerance conferred by the ultramafic P. albus isolates to growth of the host tree species is considerably greater than previously reported for other ECM. The primary mechanisms underlying this improved growth were identified as reduced Ni uptake into the roots and markedly reduced transfer from root to shoot in mycorrhizal plants. The fact that these positive responses were observed at Ni concentrations commonly observed in serpentinic soils suggests that ultramafic ecotypes of P. albus could play an important role in the adaptation of tree species to soils containing high concentrations of heavy metals and aid in strategies for ecological restoration.

[Induction of hairy roots of Panax ginseng and studies on suitable culture condition of ginseng hairy roots].

PubMed

Zhao, Shou-Jing; Li, Chang-Yu; Qian, Yan-Chun; Luo, Xiao-Pei; Zhang, Xin; Wang, Xue-Song; Kang, Bo-Yu

2004-03-01

Ginseng is a valuable medicinal plant with ginsenosides as its mian effective components. Because ginseng is a perennial plant and has a very strict demand for soil conditions, the way of cultivating ginseng by cutting woods is still used in China at present and thus forest resources has been extremely destroyed. Increasing attention has been paid to the hairy roots induced by the infection of Agrobacterium rhizogenes in the production of plant secondary metabolic products for the hairy roots are characterized by rapid growth and stable hereditary and biochemical traits. That has opened a new way for the industrial production of ginseosides. However, there is little report for such studies from China. In this paper, hairy roots of ginseng were induced from the root explants of two-year-old ginseng by Agrobacterium rhizogenes A4 with directly inoculating. The transformed hairy roots could grow rapidly on MS medium and 1/2 MS medium without hormones. The cultured clones of the hairy roots were established on a solid 1/2 MS medium. After 4 - 5 subcultures the hairy roots still maintained a vigorous growth. A pair of primers were designed and synthesized according to the analytical results of RiA4TL-DNA sequence by Slightom et al . 0.8kb rolC was obtained by PCR using the genome DNA of hairy root of ginseng. Transformation was confirmed by PCR amplification of rolC genes from the hairy roots of P. ginseng. Growth rate of hairy roots on liquid medium increased by 2 times then that of the solid medium. The growth of the hairy roots can be divided into three stages: high speed in the first two weeks, middle speed in the 3 - 4 weeks and low speed hereafter. Changing the culture solution at 2 weeks regular intervals is conductive to maintaining the rapid growth of the hairy roots. By means of determination for specific growth rate and ginsenosides content, the high-yield hairy root clone R9923 was selected. The content of monomer gisenoside of Rg1, Re, Rf, Rbl, Rc, Rb2 and Rd in hairy root clone R9923 was determined by the HPLC. The total ginsenosides content in the hairy toot clone R9923 came up to 15.2 mg/g. The suitable culture conditions for ginseng hairy roots growing were 1/2 MS liquid medium (30 g/L glucose), in a shaker at 110 r/min, changing the culture solution at 2 weeks and subculture time 4 weeks. In the liquid fermented culture of 2L medium, the yield of the hairy roots could amount to 270.10 g in 4 weeks. The industrial production of ginsenosides has been preliminarily realized. Effect factors on biomass and ginsenosides content such as culture volume, inoculation, in steps cultural technology at the scale-up process of hairy roots culture were also explorated. Our results have laid a foundation for defining optimum culture manner for large-scale cultivation and large-scale production of ginsenosides.

Induced accumulation of Au, Ag and Cu in Brassica napus grown in a mine tailings with the inoculation of Aspergillus niger and the application of two chemical compounds.

PubMed

González-Valdez, Eduardo; Alarcón, Alejandro; Ferrera-Cerrato, Ronald; Vega-Carrillo, Héctor René; Maldonado-Vega, María; Salas-Luévano, Miguel Ángel; Argumedo-Delira, Rosalba

2018-06-15

This study evaluated the ability of Brassica napus for extracting gold (Au), silver (Ag) and copper (Cu) from a mine tailings, with the inoculation of two Aspergillus niger strains, and the application of ammonium thiocyanate (NH 4 SCN) or ammonium thiosulfate [(NH 4 ) 2 S 2 O 3 ]. After seven weeks of growth inoculated or non-inoculated plants were applied with 1 or 2 g kg -1 of either NH 4 SCN or (NH 4 ) 2 S 2 O 3 , respectively. Eight days after the application of the chemical compounds, plants were harvested for determining the total dry biomass, and the content of Au, Ag, and Cu in plant organs. Application of (NH 4 ) 2 S 2 O 3 or NH 4 SCN resulted in enhanced Au-accumulation in stems (447% and 507%, respectively), while either (NH 4 ) 2 S 2 O 3 +Aspergillus, or NH 4 SCN increased the Au-accumulation in roots (198.5% and 404%, respectively) when compared to the control. Treatments with (NH 4 ) 2 S 2 O 3 or (NH 4 ) 2 S 2 O 3 +Aspergillus significantly increased (P ≤ 0.001) the accumulation of Ag in leaves (677% and 1376%, respectively), while NH 4 SCN + Aspergillus, and (NH 4 ) 2 S 2 O 3 enhanced the accumulation in stems (7153% and 6717.5%). The Ag-accumulation in roots was stimulated by NH 4 SCN+ Aspergillus, and (NH 4 ) 2 S 2 O 3 + Aspergillus (132.5% and 178%, respectively), when compared to the control. The combination of NH 4 SCN+Aspergillus significantly enhanced the Cu-accumulation in leaves (228%); whereas NH 4 SCN+ Aspergillus, or (NH 4 ) 2 S 2 O 3 + Aspergillus resulted in greater accumulation of Cu in stems (1233.5% and 1580%, respectively) than the control. Results suggest that either NH 4 SCN or (NH 4 ) 2 S 2 O 3 (with or without Aspergillus) improved the accumulation of Au and Ag by B. napus. Accumulation of Au and Ag in plant organs overpassed the hyperaccumulation criterion (> 1 mg kg -1 of plant biomass); whereas Cu-accumulation in stems and roots also overpassed such criterion (> 1000 mg kg -1 ) by applying either NH 4 SCN or (NH 4 ) 2 S 2 O 3 + A. niger. Copyright © 2018 Elsevier Inc. All rights reserved.

[Content of salicylic and jasmonic acids in pea roots (Pisum sativum L.) at the initial stage of symbiotic or pathogenic interaction with bacteria of the family Rhizobiaceae].

PubMed

Rudikovskaya, E G; Akimova, G P; Rudikovskii, A V; Katysheva, N B; Dudareva, L V

2017-01-01

A change in the contents of endogenous salicylic and jasmonic acids in the roots of the host plant at the preinfectious stage of interaction with symbiotic (Rhizobium leguminosarum) and pathogenic (Agrobacterium rizogenes) bacteria belonging for to the family Rhizobiaceae was studied. It was found that the jasmonic acid content increased 1.5–2 times 5 min after inoculation with these bacterial species. It was shown that dynamics of the change in the JA and SA contents depends on the type of infection. Thus, the JA content decreased in the case of pathogenesis, while the SA content increased. At the same time, an increased JA content was observed during symbiosis. The observed regularities could indicate the presence of different strategies of hormonal regulation for interaction with symbiotic and pathogenic bacteria belonging to the family Rhizobiaceae in peas plants.

Nitrogen-fixing bacteria with multiple plant growth-promoting activities enhance growth of tomato and red pepper.

PubMed

Islam, Md Rashedul; Sultana, Tahera; Joe, M Melvin; Yim, Woojong; Cho, Jang-Cheon; Sa, Tongmin

2013-12-01

As a suitable alternative to chemical fertilizers, the application of plant growth-promoting rhizobacteria has been increasing in recent years due to their potential to be used as biofertilizers. In the present work, 13 nitrogen-fixing bacterial strains belonging to 11 different genera were tested for their PGP attributes. All of the strains were positive for 1-aminocyclopropane-1-carboxylate deaminase (ACCD), indole-3-acetic acid (IAA), salicylic acid, and ammonia production while negative for cellulase, pectinase, and hydrocyanic acid production. The strains Pseudomonas sp. RFNB3 and Serratia sp. RFNB14 were the most effective in solubilizing both tri-calcium phosphate and zinc oxide. In addition, all strains except Pseudomonas sp. RFNB3 were able to oxidize sulfur, and six strains were positive for siderophore synthesis. Each strain tested in this study possesses at least four PGP properties in addition to nitrogen fixation. Nine strains were selected based on their multiple PGP potential, particularly ACCD and IAA production, and evaluated for their effects on early growth of tomato and red pepper under gnotobiotic conditions. Bacterial inoculation considerably influenced root and shoot length, seedling vigor, and dry biomass of the two crop plants. Three strains that demonstrated substantial effects on plant performance were further selected for greenhouse trials with red pepper, and among them Pseudomonas sp. RFNB3 resulted in significantly higher plant height (26%) and dry biomass (28%) compared to control. The highest rate of nitrogen fixation, as determined by acetylene reduction assay, occurred in Novosphingobium sp. RFNB21 inoculated red pepper root (49.6 nM of ethylene/h/g of dry root) and rhizosphere soil (41.3 nM of ethylene/h/g of dry soil). Inoculation with nitrogen-fixing bacteria significantly increased chlorophyll content, and the uptake of different macro- and micro-nutrient contents enhancing also in red pepper shoots, in comparison with uninoculated controls. The population estimation studies showed that nitrogen-fixing as well as total heterotrophic bacteria were also noticeably increased in soil and plant samples. The findings of this study suggest that certain nitrogen-fixing strains possessing multiple PGP traits could be applied in the development of biofertilizers. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced tomato disease resistance primed by arbuscular mycorrhizal fungus

PubMed Central

Song, Yuanyuan; Chen, Dongmei; Lu, Kai; Sun, Zhongxiang; Zeng, Rensen

2015-01-01

Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance. PMID:26442091

Enhanced tomato disease resistance primed by arbuscular mycorrhizal fungus.

PubMed

Song, Yuanyuan; Chen, Dongmei; Lu, Kai; Sun, Zhongxiang; Zeng, Rensen

2015-01-01

Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance.

Biological Control beneath the Feet: A Review of Crop Protection against Insect Root Herbivores.

PubMed

Kergunteuil, Alan; Bakhtiari, Moe; Formenti, Ludovico; Xiao, Zhenggao; Defossez, Emmanuel; Rasmann, Sergio

2016-11-29

Sustainable agriculture is certainly one of the most important challenges at present, considering both human population demography and evidence showing that crop productivity based on chemical control is plateauing. While the environmental and health threats of conventional agriculture are increasing, ecological research is offering promising solutions for crop protection against herbivore pests. While most research has focused on aboveground systems, several major crop pests are uniquely feeding on roots. We here aim at documenting the current and potential use of several biological control agents, including micro-organisms (viruses, bacteria, fungi, and nematodes) and invertebrates included among the macrofauna of soils (arthropods and annelids) that are used against root herbivores. In addition, we discuss the synergistic action of different bio-control agents when co-inoculated in soil and how the induction and priming of plant chemical defense could be synergized with the use of the bio-control agents described above to optimize root pest control. Finally, we highlight the gaps in the research for optimizing a more sustainable management of root pests.

Biological Control beneath the Feet: A Review of Crop Protection against Insect Root Herbivores

PubMed Central

Kergunteuil, Alan; Bakhtiari, Moe; Formenti, Ludovico; Xiao, Zhenggao; Defossez, Emmanuel; Rasmann, Sergio

2016-01-01

Sustainable agriculture is certainly one of the most important challenges at present, considering both human population demography and evidence showing that crop productivity based on chemical control is plateauing. While the environmental and health threats of conventional agriculture are increasing, ecological research is offering promising solutions for crop protection against herbivore pests. While most research has focused on aboveground systems, several major crop pests are uniquely feeding on roots. We here aim at documenting the current and potential use of several biological control agents, including micro-organisms (viruses, bacteria, fungi, and nematodes) and invertebrates included among the macrofauna of soils (arthropods and annelids) that are used against root herbivores. In addition, we discuss the synergistic action of different bio-control agents when co-inoculated in soil and how the induction and priming of plant chemical defense could be synergized with the use of the bio-control agents described above to optimize root pest control. Finally, we highlight the gaps in the research for optimizing a more sustainable management of root pests. PMID:27916820

Influence of Bacillus spp. strains on seedling growth and physiological parameters of sorghum under moisture stress conditions.

PubMed

Grover, Minakshi; Madhubala, R; Ali, Sk Z; Yadav, S K; Venkateswarlu, B

2014-09-01

Microorganisms isolated from stressed ecosystem may prove as ideal candidates for development of bio-inoculants for stressed agricultural production systems. In the present study, moisture stress tolerant rhizobacteria were isolated from the rhizosphere of sorghum, pigeonpea, and cowpea grown under semiarid conditions in India. Four isolates KB122, KB129, KB133, and KB142 from sorghum rhizosphere exhibited plant growth promoting traits and tolerance to salinity, high temperature, and moisture stress. These isolates were identified as Bacillus spp. by 16S rDNA sequence analysis. The strains were evaluated for growth promotion of sorghum seedlings under two different moisture stress conditions (set-I, continuous 50% soil water holding capacity (WHC) throughout the experiment and set-II, 75% soil WHC for 27 days followed by no irrigation for 5 days) under greenhouse conditions. Plate count and scanning electron microscope studies indicated successful root surface colonization by inoculated bacteria. Plants inoculated with Bacillus spp. strains showed better growth in terms of shoot length and root biomass with dark greenish leaves due to high chlorophyll content while un-inoculated plants showed rolling of the leaves, stunted appearance, and wilting under both stress conditions. Inoculation also improved leaf relative water content and soil moisture content. However, variation in proline and sugar content in the different treatments under two stress conditions indicated differential effect of microbial treatments on plant physiological parameters under stress conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solubilisation of Phosphate and Micronutrients by Trichoderma harzianum and Its Relationship with the Promotion of Tomato Plant Growth

PubMed Central

Pang, Guan; Shen, Qi-Rong; Li, Rong; Chen, Wei

2015-01-01

Trichoderma harzianum strain SQR-T037 is a biocontrol agent that has been shown to enhance the uptake of nutrients (macro- and microelements) by plants in fields. The objective of this study was to investigate the contribution of SQR-T037 to P and microelement (Fe, Mn, Cu and Zn) nutrition in tomato plants grown in soil and in hydroponic conditions. Inoculation with SQR-T037 significantly improved the biomass and nutrient uptake of tomato seedlings grown in a nutrient-limiting soil. So we investigated the capability of SQR-T037 to solubilise sparingly soluble minerals in vitro via four known mechanisms: acidification by organic acids, chelation by siderophores, redox by ferric reductase and hydrolysis by phytase. SQR-T037 was able to solubilise phytate, Fe2O3, CuO, and metallic Zn but not Ca3(PO4)2 or MnO2. Organic acids, including lactic acid, citric acid, tartaric acid and succinic acid, were detected by HPLC and LC/MS in two Trichoderma cultures. Additionally, we inoculated tomato seedlings with SQR-T037 using a hydroponic system with specific nutrient deficiencies (i.e., nutrient solutions deficient in P, Fe, Cu or Zn and supplemented with their corresponding solid minerals) to better study the effects of Trichoderma inoculation on plant growth and nutrition. Inoculated seedlings grown in Cu-deficient hydroponic conditions exhibited increases in dry plant biomass (92%) and Cu uptake (42%) relative to control plants. However, we did not observe a significant effect on seedling biomass in plants grown in the Fe- and Zn-deficient hydroponic conditions; by contrast, the biomass decreased by 82% in the P-deficient hydroponic condition. Thus, we demonstrated that Trichoderma SQR-T037 competed for P (phytate) and Zn with tomato seedlings by suppressing root development, releasing phytase and/or chelating minerals. The results of this study suggest that the induction of increased or suppressed plant growth occurs through the direct effect of T. harzianum on root development, in combination with indirect mechanisms, such as mineral solubilisation (including solubilisation via acidification, redox, chelation and hydrolysis). PMID:26110536

Solubilisation of Phosphate and Micronutrients by Trichoderma harzianum and Its Relationship with the Promotion of Tomato Plant Growth.

PubMed

Li, Rui-Xia; Cai, Feng; Pang, Guan; Shen, Qi-Rong; Li, Rong; Chen, Wei

2015-01-01

Trichoderma harzianum strain SQR-T037 is a biocontrol agent that has been shown to enhance the uptake of nutrients (macro- and microelements) by plants in fields. The objective of this study was to investigate the contribution of SQR-T037 to P and microelement (Fe, Mn, Cu and Zn) nutrition in tomato plants grown in soil and in hydroponic conditions. Inoculation with SQR-T037 significantly improved the biomass and nutrient uptake of tomato seedlings grown in a nutrient-limiting soil. So we investigated the capability of SQR-T037 to solubilise sparingly soluble minerals in vitro via four known mechanisms: acidification by organic acids, chelation by siderophores, redox by ferric reductase and hydrolysis by phytase. SQR-T037 was able to solubilise phytate, Fe2O3, CuO, and metallic Zn but not Ca3(PO4)2 or MnO2. Organic acids, including lactic acid, citric acid, tartaric acid and succinic acid, were detected by HPLC and LC/MS in two Trichoderma cultures. Additionally, we inoculated tomato seedlings with SQR-T037 using a hydroponic system with specific nutrient deficiencies (i.e., nutrient solutions deficient in P, Fe, Cu or Zn and supplemented with their corresponding solid minerals) to better study the effects of Trichoderma inoculation on plant growth and nutrition. Inoculated seedlings grown in Cu-deficient hydroponic conditions exhibited increases in dry plant biomass (92%) and Cu uptake (42%) relative to control plants. However, we did not observe a significant effect on seedling biomass in plants grown in the Fe- and Zn-deficient hydroponic conditions; by contrast, the biomass decreased by 82% in the P-deficient hydroponic condition. Thus, we demonstrated that Trichoderma SQR-T037 competed for P (phytate) and Zn with tomato seedlings by suppressing root development, releasing phytase and/or chelating minerals. The results of this study suggest that the induction of increased or suppressed plant growth occurs through the direct effect of T. harzianum on root development, in combination with indirect mechanisms, such as mineral solubilisation (including solubilisation via acidification, redox, chelation and hydrolysis).

Assessment of SCAR markers to design real-time PCR primers for rhizosphere quantification of Azospirillum brasilense phytostimulatory inoculants of maize.

PubMed

Couillerot, O; Poirier, M-A; Prigent-Combaret, C; Mavingui, P; Caballero-Mellado, J; Moënne-Loccoz, Y

2010-08-01

To assess the applicability of sequence characterized amplified region (SCAR) markers obtained from BOX, ERIC and RAPD fragments to design primers for real-time PCR quantification of the phytostimulatory maize inoculants Azospirillum brasilense UAP-154 and CFN-535 in the rhizosphere. Primers were designed based on strain-specific SCAR markers and were screened for successful amplification of target strain and absence of cross-reaction with other Azospirillum strains. The specificity of primers thus selected was verified under real-time PCR conditions using genomic DNA from strain collection and DNA from rhizosphere samples. The detection limit was 60 fg DNA with pure cultures and 4 x 10(3) (for UAP-154) and 4 x 10(4) CFU g(-1) (for CFN-535) in the maize rhizosphere. Inoculant quantification was effective from 10(4) to 10(8) CFU g(-1) soil. BOX-based SCAR markers were useful to find primers for strain-specific real-time PCR quantification of each A. brasilense inoculant in the maize rhizosphere. Effective root colonization is a prerequisite for successful Azospirillum phytostimulation, but cultivation-independent monitoring methods were lacking. The real-time PCR methods developed here will help understand the effect of environmental conditions on root colonization and phytostimulation by A. brasilense UAP-154 and CFN-535.

Contrasting colonization and plant growth promoting capacity between wild type and gfp-derative of the endophyte Pseudomonas putida W619 in hybrid poplar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weyens N.; van der Lelie D.; Boulet, J.

2011-06-09

This study aims to investigate the colonization of poplar by the endophyte Pseudomonas putida W619 and its capacity to promote plant growth. Poplar cuttings were inoculated with P. putida W619 (wild-type or gfp-labelled). The colonization of both strains was investigated and morphological, physiological and biochemical parameters were analyzed to evaluate plant growth promotion. Inoculation with P. putida W619 (wild-type) resulted in remarkable growth promotion, decreased activities of antioxidative defence related enzymes, and reduced stomatal resistance, all indicative of improved plant health and growth in comparison with the non-inoculated cuttings. In contrast, inoculation with gfp-labelled P. putida W619 did not promotemore » growth; it even had a negative effect on plant health and growth. Furthermore, compared to the wildtype strain, colonization by the gfp-labelled P. putida W619::gfp1 was much lower; it only colonized the rhizosphere and root cortex while the wild-type strain also colonized the root xylem vessels. Despite the strong plant growth promoting capacity of P. putida W619 (wild-type), after gfp labelling its growth promoting characteristics disappeared and its colonization capacity was strongly influenced; for these reasons gfp labelling should be applied with sufficient caution.« less

Alginate-perlite encapsulated Pseudomonas putida A (ATCC 12633) cells: Preparation, characterization and potential use as plant inoculants.

PubMed

Liffourrena, Andrés S; Lucchesi, Gloria I

2018-04-30

Microbial immobilization can be used to prepare encapsulated inoculants. Here, we characterize and describe the preparation of Ca-alginate-perlite microbeads loaded with cells of plant growth-promoting Pseudomonas putida A (ATCC 12633), for their future application as agricultural inoculants. The microbeads were prepared by dropwise addition of a CaCl 2 -paraffin emulsion mixture to an emulsion containing alginate 2% (w/v), perlite 0.1-0.4% (w/v) and bacterial suspension in 0.9% NaCl (10 10  CFU/mL). For all perlite concentrations used, microbead size was 90-120 μm, the trapped population was 10 8  CFU/g microbeads and the increase in mechanical stability was proportional to perlite concentration. Microbeads containing 0.4% (w/v) perlite were able to release bacteria into the medium after 30 days of incubation. When we evaluated how P. putida A (ATCC 12633) entrapped in Ca-alginate-perlite (0.4% (w/v)) microbeads colonized the Arabidopsis thaliana rhizosphere, an increase in colonization over time was detected (from an initial 2.1 × 10 4 to 9.2 × 10 5  CFU/g soil after 21 days). With this treatment, growth promotion of A. thaliana occurred with an increase in the amount of proteins, and in root and leaf biomass. It was concluded that the microbeads could be applied as possible inoculants, since they provide protection and a controlled release of microorganisms into the rhizosphere. Copyright © 2018. Published by Elsevier B.V.

Mutation of praR in Rhizobium leguminosarum enhances root biofilms, improving nodulation competitiveness by increased expression of attachment proteins

PubMed Central

Frederix, Marijke; Edwards, Anne; Swiderska, Anna; Stanger, Andrew; Karunakaran, Ramakrishnan; Williams, Alan; Abbruscato, Pamela; Sanchez-Contreras, Maria; Poole, Philip S; Downie, J Allan

2014-01-01

In Rhizobium leguminosarum bv. viciae, quorum-sensing is regulated by CinR, which induces the cinIS operon. CinI synthesizes an AHL, whereas CinS inactivates PraR, a repressor. Mutation of praR enhanced biofilms in vitro. We developed a light (lux)-dependent assay of rhizobial attachment to roots and demonstrated that mutation of praR increased biofilms on pea roots. The praR mutant out-competed wild-type for infection of pea nodules in mixed inoculations. Analysis of gene expression by microarrays and promoter fusions revealed that PraR represses its own transcription and mutation of praR increased expression of several genes including those encoding secreted proteins (the adhesins RapA2, RapB and RapC, two cadherins and the glycanase PlyB), the polysaccharide regulator RosR, and another protein similar to PraR. PraR bound to the promoters of several of these genes indicating direct repression. Mutations in rapA2, rapB, rapC, plyB, the cadherins or rosR did not affect the enhanced root attachment or nodule competitiveness of the praR mutant. However combinations of mutations in rapA, rapB and rapC abolished the enhanced attachment and nodule competitiveness. We conclude that relief of PraR-mediated repression determines a lifestyle switch allowing the expression of genes that are important for biofilm formation on roots and the subsequent initiation of infection of legume roots. PMID:24942546

Arbuscular mycorrhizal symbiosis can mitigate the negative effects of night warming on physiological traits of Medicago truncatula L.

PubMed

Hu, Yajun; Wu, Songlin; Sun, Yuqing; Li, Tao; Zhang, Xin; Chen, Caiyan; Lin, Ge; Chen, Baodong

2015-02-01

Elevated night temperature, one of the main climate warming scenarios, can have profound effects on plant growth and metabolism. However, little attention has been paid to the potential role of mycorrhizal associations in plant responses to night warming, although it is well known that symbiotic fungi can protect host plants against various environmental stresses. In the present study, physiological traits of Medicago truncatula L. in association with the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis were investigated under simulated night warming. A constant increase in night temperature of 1.53 °C significantly reduced plant shoot and root biomass, flower and seed number, leaf sugar concentration, and shoot Zn and root P concentrations. However, the AM association essentially mitigated these negative effects of night warming by improving plant growth, especially through increased root biomass, root to shoot ratio, and shoot Zn and root P concentrations. A significant interaction was observed between R. irregularis inoculation and night warming in influencing both root sucrose concentration and expression of sucrose synthase (SusS) genes, suggesting that AM symbiosis and increased night temperature jointly regulated plant sugar metabolism. Night warming stimulated AM fungal colonization but did not influence arbuscule abundance, symbiosis-related plant or fungal gene expression, or growth of extraradical mycelium, indicating little effect of night warming on the development or functioning of AM symbiosis. These findings highlight the importance of mycorrhizal symbiosis in assisting plant resilience to climate warming.

The symbiosis with the arbuscular mycorrhizal fungus Rhizophagus irregularis drives root water transport in flooded tomato plants.

PubMed

Calvo-Polanco, Monica; Molina, Sonia; Zamarreño, Angel María; García-Mina, Jose María; Aroca, Ricardo

2014-05-01

It is known that the presence of arbuscular mycorrhizal fungi within the plant roots enhances the tolerance of the host plant to different environmental stresses, although the positive effect of the fungi in plants under waterlogged conditions has not been well studied. Tolerance of plants to flooding can be achieved through different molecular, physiological and anatomical adaptations, which will affect their water uptake capacity and therefore their root hydraulic properties. Here, we investigated the root hydraulic properties under non-flooded and flooded conditions in non-mycorrhizal tomato plants and plants inoculated with the arbuscular mycorrhizal fungus Rhizophagus irregularis. Only flooded mycorrhizal plants increased their root hydraulic conductivity, and this effect was correlated with a higher expression of the plant aquaporin SlPIP1;7 and the fungal aquaporin GintAQP1. There was also a higher abundance of the PIP2 protein phoshorylated at Ser280 in mycorrhizal flooded plants. The role of plant hormones (ethylene, ABA and IAA) in root hydraulic properties was also taken into consideration, and it was concluded that, in mycorrhizal flooded plants, ethylene has a secondary role regulating root hydraulic conductivity whereas IAA may be the key hormone that allows the enhancement of root hydraulic conductivity in mycorrhizal plants under low oxygen conditions.

Control of Meloidogyne incognita Using Mixtures of Organic Acids

PubMed Central

Seo, Yunhee; Kim, Young Ho

2014-01-01

This study sought to control the root-knot nematode (RKN) Meloidogyne incognita using benign organo-chemicals. Second-stage juveniles (J2) of RKN were exposed to dilutions (1.0%, 0.5%, 0.2%, and 0.1%) of acetic acid (AA), lactic acid (LA), and their mixtures (MX). The nematode bodies were disrupted severely and moderately by vacuolations in 0.5% of MX and single organic acids, respectively, suggesting toxicity of MX may be higher than AA and LA. The mortality of J2 was 100% at all concentrations of AA and MX and only at 1.0% and 0.5% of LA, which lowered slightly at 0.2% and greatly at 0.1% of LA. This suggests the nematicidal activity of MX may be mostly derived from AA together with supplementary LA toxicity. MX was applied to chili pepper plants inoculated with about 1,000 J2, for which root-knot gall formations and plant growths were examined 4 weeks after inoculation. The root gall formation was completely inhibited by 0.5% MX and standard and double concentrations of fosthiazate; and inhibited 92.9% and 57.1% by 0.2% and 0.1% MX, respectively. Shoot height, shoot weight, and root weight were not significantly (P ≤ 0.05) different among all treatments and the untreated and non-inoculated controls. All of these results suggest that the mixture of the organic acids may have a potential to be developed as an eco-friendly nematode control agent that needs to be supported by the more nematode control experiments in fields. PMID:25506312

[Effects of different endophytic fungi on seedling growth of Dendrobium devonianum].

PubMed

Huang, Hui; Shao, Shi-Cheng; Gao, Jiang-Yun

2016-06-01

To obtain seedling growth-promoting fungi is a key step in restoration-friendly cultivation of medicinal Dendrobium species, since there are a large number of functionally-unknown endophytic fungi in the roots of Dendrobium plants.In this study, six functionally-unknown endophytic fungal strains were isolated from roots of D.devonianum using single peleton isolation technology, and used in inoculation experiments to test their effectiveness for seedling growth in D.devonianum.After 90 days of inoculation, comparing with the control treatment, FDdS-1, FDdS-2 and FDdS-4 showed strong pathogenic or fatal effects on seedlings; while, FDdS-12, FDdS-9 and FDdS-5 had different effects on seedling growth.FDdS-5 had significant promoting effects on height, fresh and dry weight, stem diameter and root numbers, while FDdS-9 only had significant promoting effect on seedling height, and FDdS-12 had a negative effect on seedling growth.According to the anatomical features of the inoculated roots, FDdS-5 fungi could infect the velamina of seedlings and the existence of symbiosis pelotons in the cortex cells, suggesting that FDdS-5 is a mycorrhiza fungi of D.devonianum.FDdS-5 and FDdS-9 were identified as Sebacina vermifera and Sebacina sp.by molecular technologies.By using FDdS-5 in the restoration-friendly cultivation of D.devonianum, it could effectively promote seedling growth and shorten the seedling growth periods.The results will aid in reintroduction and cultivation of D.devonianum. Copyright© by the Chinese Pharmaceutical Association.

Using survival analysis for assessing resistance to Phytophthora lateralis in Port-Orford-Cedar families

Treesearch

Sylvia R. Mori; Richard A. Sniezko; Angelia Kegley; Jim Hamlin

2012-01-01

In a greenhouse trial to examine genetic resistance among seedling families (half-sib, full-sib, and selfed) of Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murr.) Parl.) to the root pathogen Phytophthora lateralis, the root tips of seedlings were inoculated, and the subsequent mortality was followed over a 3 year period....

Sterilization of root canal spaces using an Nd:YAG laser, in vitro

NASA Astrophysics Data System (ADS)

Goodis, Harold E.; White, Joel M.; Yee, Barbara; Marshall, Sally J.; Marshall, Grayson W.

1995-05-01

A smear layer is created during the cleaning and shaping of root canal systems. The Nd:YAG laser has been shown to be effective in removing that smear layer and any tissue remnants from prepared root canal systems suggesting that it may aid in root canal sterilization without detrimental thermal effects to adjacent tissues. The root canal system of 72 single-rooted teeth was conventionally prepared and sterilized using gamma radiation. The teeth were divided into three groups of 24 each, 8 of which were inoculated only with sterile broth and remained as negative controls. Sixteen teeth of each group were inoculated with one of three organisms of 106 to 1010 CFU/(mu) l: B subtilis (BS), E. coli (EC) and S. marcescens (SM) (10 (mu) l). Eight in each group were not treated further and served as positive controls. Sixteen test teeth were treated with the laser three times using each exposure parameter: 1 W, 10 Hz pulses per second (pps); 2 W, 20 Hz; and 3 W, 30 Hz inserted to the radiographic apex. Laser exposures were completed while withdrawing the fiber from the root canal system. At completion of laser exposure, all teeth were cultured, using sterile paper points and plated on brain heat infusion agar. Three cultures were taken for each tooth, the plates incubated for 72 hours, and read for the presence of growth of colony-forming units. The laser was able to reduce the number of organisms placed in root canal systems, and suggests that the laser may be used in root canal therapy for bacterial reduction and cleaning of the root canal space.

Effect of bacterial root symbiosis and urea as source of nitrogen on performance of soybean plants grown hydroponically for Bioregenerative Life Support Systems (BLSSs)

PubMed Central

Paradiso, Roberta; Buonomo, Roberta; Dixon, Mike A.; Barbieri, Giancarlo; De Pascale, Stefania

2015-01-01

Soybean is traditionally grown in soil, where root symbiosis with Bradyrhizobium japonicum can supply nitrogen (N), by means of bacterial fixation of atmospheric N2. Nitrogen fertilizers inhibit N-fixing bacteria. However, urea is profitably used in soybean cultivation in soil, where urease enzymes of telluric microbes catalyze the hydrolysis to ammonium, which has a lighter inhibitory effect compared to nitrate. Previous researches demonstrated that soybean can be grown hydroponically with recirculating complete nitrate-based nutrient solutions. In Space, urea derived from crew urine could be used as N source, with positive effects in resource procurement and waste recycling. However, whether the plants are able to use urea as the sole source of N and its effect on root symbiosis with B. japonicum is still unclear in hydroponics. We compared the effect of two N sources, nitrate and urea, on plant growth and physiology, and seed yield and quality of soybean grown in closed-loop Nutrient Film Technique (NFT) in growth chamber, with or without inoculation with B. japonicum. Urea limited plant growth and seed yield compared to nitrate by determining nutrient deficiency, due to its low utilization efficiency in the early developmental stages, and reduced nutrients uptake (K, Ca, and Mg) throughout the whole growing cycle. Root inoculation with B. japonicum did not improve plant performance, regardless of the N source. Specifically, nodulation increased under fertigation with urea compared to nitrate, but this effect did not result in higher leaf N content and better biomass and seed production. Urea was not suitable as sole N source for soybean in closed-loop NFT. However, the ability to use urea increased from young to adult plants, suggesting the possibility to apply it during reproductive phase or in combination with nitrate in earlier developmental stages. Root symbiosis did not contribute significantly to N nutrition and did not enhance the plant ability to use urea, possibly because of ineffective infection process and nodule functioning in hydroponics. PMID:26579144

Application of Plant-Growth-Promoting Fungi Trichoderma longibrachiatum T6 Enhances Tolerance of Wheat to Salt Stress through Improvement of Antioxidative Defense System and Gene Expression

PubMed Central

Zhang, Shuwu; Gan, Yantai; Xu, Bingliang

2016-01-01

Soil salinity is a serious problem worldwide that reduces agricultural productivity. Trichoderma longibrachiatum T6 (T6) has been shown to promote wheat growth and induce plant resistance to parasitic nematodes, but whether the plant-growth-promoting fungi T6 can enhance plant tolerance to salt stress is unknown. Here, we determined the effect of plant-growth-promoting fungi T6 on wheat seedlings’ growth and development under salt stress, and investigated the role of T6 in inducing the resistance to NaCl stress at physiological, biochemical, and molecular levels. Wheat seedlings were inoculated with the strain of T6 and then compared with non-inoculated controls. Shoot height, root length, and shoot and root weights were measured on 15 days old wheat seedlings grown either under 150 mM NaCl or in a controlled setting without any NaCl. A number of colonies were re-isolated from the roots of wheat seedlings under salt stress. The relative water content in the leaves and roots, chlorophyll content, and root activity were significantly increased, and the accumulation of proline content in leaves was markedly accelerated with the plant growth parameters, but the content of leaf malondialdehyde under saline condition was significantly decreased. The antioxidant enzymes-superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in wheat seedlings were increased by 29, 39, and 19%, respectively, with the application of the strain of T6 under salt stress; the relative expression of SOD, POD, and CAT genes in these wheat seedlings were significantly up-regulated. Our results indicated that the strain of T6 ameliorated the adverse effects significantly, protecting the seedlings from salt stress during their growth period. The possible mechanisms by which T6 suppresses the negative effect of NaCl stress on wheat seedling growth may be due to the improvement of the antioxidative defense system and gene expression in the stressed wheat plants. PMID:27695475

HOW FUNGI INTERACT WITH NEMATODE TO ACTIVATE THE PLANT DEFENCE RESPONSE TO TOMATO PLANTS.

PubMed

Leonetti, P; Costanza, A; Zonno, M C; Molinari, S; Altomare, C

2014-01-01

Management of plant parasitic nematodes with nematode predators, parasites or antagonists is an eco-friendly approach that may avoid the problems arisen by the use of toxic chemicals. Fungi belonging to Trichoderma spp. are well known in literature for their role in control of plant parasitic nematodes. Root-knot nematodes (RKNs), Meloidogyne spp., are obligate parasites that cause the formation of familiar galls on the roots of many cultivated plants. The interaction between the M. incognita motile second stage juveniles (J2s) and the isolate ITEM 908 of Trichoderma harzianum was examined in its effect on the nematode infestation level of susceptible tomato plants. To gain insight into the mechanisms by which ITEM 908 interacts with nematode-infected tomato plants, the expression patterns of the genes PR1 (marker of Salycilic Acid-depending resistance signalling pathway) and JERF3 (marker of the Jasmonic Acid/Ethylene-depending resistance signalling pathway) were detected over time in: i) untreated roots; ii) roots pre-treated with the fungus; iii) roots inoculated with the nematode; iv) pre-treated and inoculated roots. Infestation parameters were checked in untreated plants and plants treated with the fungus to test the effect of the fungus on nematode infestation level and to compare this effect with the expression of the genes PR1 and JERF3, involved in induced resistance.

Optimization of adventitious root culture for production of biomass and secondary metabolites in Prunella vulgaris L.

PubMed

Fazal, Hina; Abbasi, Bilal Haider; Ahmad, Nisar

2014-11-01

Adventitious root cultures of Prunella vulgaris L. were established in shaking flask system for the production of biomass and secondary metabolites. Adventitious root cultures were induced from callus cultures obtained from leaf explants on solid Murashige and Skoog (MS) medium containing combination of 6-benzyladenine (BA; 1.0 mg l(-1)) and naphthalene acetic acid (NAA; 1.5 mg l(-1)). Thereafter, 0.49 g inoculum was transferred to liquid MS medium supplemented with different concentrations of NAA (0.5-2.0 mg l(-1)). Growth kinetics of adventitious roots was recorded with an interval of 7 days for 49 days period. Highest biomass accumulation (2.13 g/l) was observed in liquid medium containing 1.0 mg l(-1) NAA after 21 days of inoculation. However, other concentrations of NAA also showed similar accumulation pattern but the biomass gradually decreases after 49 days of inoculation. Adventitious roots were collected and dried for investigation of total phenolics (TP), total flavonoids (TF), and antioxidant activities. Higher TPC (0.995 GAE mg/g-DRB) and TFC (6.615 RE mg/g-DRB) were observed in 0.5 mg l(-1) NAA treated cultures. In contrast, higher antioxidant activity (83.53 %) was observed 1.5 mg l(-1) NAA treated cultures. These results are helpful in up scaling of root cultures into bioreactor for secondary metabolites production.

Zn uptake, physiological response and stress attenuation in mycorrhizal jack bean growing in soil with increasing Zn concentrations.

PubMed

Andrade, Sara A L; Gratão, Priscila L; Schiavinato, Marlene A; Silveira, Adriana P D; Azevedo, Ricardo A; Mazzafera, Paulo

2009-06-01

The influence of arbuscular mycorrhizal fungi (AMF) inoculation on Canavalia ensiformis growth, nutrient and Zn uptake, and on some physiological parameters in response to increasing soil Zn concentrations was studied. Treatments were applied in seven replicates in a 2 x 4 factorial design, consisting of the inoculation or not with the AMF Glomus etunicatum, and the addition of Zn to soil at the concentrations of 0, 100, 300 and 900 mg kg(-1). AMF inoculation enhanced the accumulation of Zn in tissues and promoted biomass yields and root nodulation. Mycorrhizal plants exhibited relative tolerance to Zn up to 300 mg kg(-1) without exhibiting visual symptoms of toxicity, in contrast to non-mycorrhizal plants which exhibited a significant growth reduction at the same soil Zn concentration. The highest concentration of Zn added to soil was highly toxic to the plants. Leaves of plants grown in high Zn concentration exhibited a Zn-induced proline accumulation and also an increase in soluble amino acid contents; however proline contents were lower in mycorrhizal jack beans. Plants in association or not with the AMF exhibited marked differences in the foliar soluble amino acid profile and composition in response to Zn addition to soil. In general, Zn induced oxidative stress which could be verified by increased lipid peroxidation rates and changes in catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase activities. In summary, G. etunicatum was able to maintain an efficient symbiosis with jack bean plants in moderately contaminated Zn-soils, improving plant performance under those conditions, which is likely to be due to a combination of physiological and nutritional changes caused by the intimate relation between fungus and plant. The enhanced Zn uptake by AMF inoculated jack bean plants might be of interest for phytoremediation purposes.

Postharvest transfer and survival of Salmonella enterica serotype enteritidis on living lettuce.

PubMed

Waitt, J A; Kuhn, D D; Welbaum, G E; Ponder, M A

2014-02-01

The potential for postharvest transfer of Salmonella to 'living lettuce' is not well understood. In this study, the transfer of Salmonella enterica Enteritidis (6 log CFU g(-1) ) from worker hands or contaminated roots to leaves of living lettuce was quantified. Transfer rates of Salmonella from contaminated gloves to sequentially handled lettuce heads ranged from 94% to head 1, 82% to head 2 and 69% to head 3. On average, 2.9 ± 0.1 log CFU g(-1) (64%) Salmonella was transferred from inoculated roots to leaves resulting from typical postharvest handling activities for living lettuce. Salmonella persisted on leaves stored at recommended storage temperatures (4°C) and increased 0.5 log CFU g(-1) when stored at temperature abuse conditions (12°C). Salmonella increased 1.6 log CFU g(-1) on roots after 18-day storage at 12°C, emphasizing the need to maintain temperature control to reduce the risk of human illness. Hydroponically grown lettuce packaged in plastic clamshells with intact roots, marketed as 'living lettuce', is increasing in popularity due to its extended shelf life. This study demonstrates the transfer of Salmonella from contaminated worker hands and contaminated roots to leaves where it persisted at 4°C for 18 day. Temperature abuse (12°C) increased Salmonella on roots and leaves. These findings suggest that failure to maintain temperatures below 12°C can pose a risk for consumers purchasing living lettuce at markets where recommended storage temperatures are not maintained. © 2013 The Society for Applied Microbiology.

Using common mycorrhizal networks for controlled inoculation of Quercus spp. with Tuber melanosporum: the nurse plant method.

PubMed

Pereira, Guillermo; Palfner, Götz; Chávez, Daniel; Suz, Laura M; Machuca, Angela; Honrubia, Mario

2013-07-01

The high cost and restricted availability of black truffle spore inoculum for controlled mycorrhiza formation of host trees produced for truffle orchards worldwide encourage the search for more efficient and sustainable inoculation methods that can be applied globally. In this study, we evaluated the potential of the nurse plant method for the controlled inoculation of Quercus cerris and Quercus robur with Tuber melanosporum by mycorrhizal networks in pot cultures. Pine bark compost, adjusted to pH 7.8 by liming, was used as substrate for all assays. Initially, Q. robur seedlings were inoculated with truffle spores and cultured for 12 months. After this period, the plants presenting 74 % mycorrhizal fine roots were transferred to larger containers. Nurse plants were used for two treatments of two different nursling species: five sterilized acorns or five 45-day-old, axenically grown Q. robur or Q. cerris seedlings, planted in containers around the nurse plant. After 6 months, colonized nursling plant root tips showed that mycorrhiza formation by T. melanosporum was higher than 45 % in the seedlings tested, with the most successful nursling combination being Q. cerris seedlings, reaching 81 % colonization. Bulk identification of T. melanosporum mycorrhizae was based on morphological and anatomical features and confirmed by sequencing of the internal transcribed spacer region of the ribosomal DNA of selected root tips. Our results show that the nurse plant method yields attractive rates of mycorrhiza formation by the Périgord black truffle and suggest that establishing and maintaining common mycorrhizal networks in pot cultures enables sustained use of the initial spore inoculum.

Development of formulations of biological agents for management of root rot of lettuce and cucumber.

PubMed

Amer, G A; Utkhede, R S

2000-09-01

The effect of various carrier formulations of Bacillus subtilis and Pseudomonas putida were tested on germination, growth, and yield of lettuce and cucumber crops in the presence of Pythium aphanidermatum and Fusarium oxysporum f.sp. cucurbitacearum, respectively. Survival of B. subtilis and P. putida in various carriers under refrigeration (about 0 degree C) and at room temperature (about 22 degrees C) was also studied. In all carrier formulations, B. subtilis strain BACT-0 survived up to 45 days. After 45 days of storage at room temperature (about 22 degrees C), populations B. subtilis strain BACT-0 were significantly higher in vermiculite, kaolin, and bacterial broth carriers compared with other carriers. Populations of P. putida were significantly higher in vermiculite, peat moss, wheat bran, and bacterial broth than in other carriers when stored either under refrigeration (about 0 degree C) or at room temperature (about 22 degrees C) for 15 or 45 days. Germination of lettuce seed was not affected in vermiculite, talc, kaolin, and peat moss carriers, but germination was significantly reduced in alginate and bacterial broth carriers of B. subtilis compared to the non-treated control. Germination of cucumber seed was not affected by any of the carriers. Significantly higher fresh lettuce and root weights were observed in vermiculite and kaolin carriers of B. subtilis compared with P. aphanidermatum-inoculated control plants. Lettuce treated with vermiculite, and kaolin carriers of B. subtilis, or non-inoculated control lettuce plants had significantly lower root rot ratings than talc, peat moss, bacterial broth, and P. aphanidermatum-inoculated control plants. Growth and yield of cucumber plants were significantly higher in vermiculite-based carrier of P. putida than the other carriers and Fusarium oxysporum f.sp. cucurbitacearum-inoculated plants.

A plant growth-promoting symbiosis between Mycena galopus and Vaccinium corymbosum seedlings.

PubMed

Grelet, Gwen-Aëlle; Ba, Ren; Goeke, Dagmar F; Houliston, Gary J; Taylor, Andy F S; Durall, Daniel M

2017-11-01

Typically, Mycena species are viewed as saprotrophic fungi. However, numerous detections of Mycena spp. in the roots of green plants suggest that a continuum from saprotrophy to biotrophy could exist. In particular, mycenoid species have repeatedly been found in Ericaceae plant roots. Our study asked whether (1) Mycena species are commonly found in the roots of green Ericaceae plants; (2) Mycena sequences are limited to a single group/lineage within the genus; and (3) a Mycena sp. can behave as a beneficial root associate with a typical ericoid mycorrhizal plant (Vaccinium corymbosum), regardless of how much external labile carbon is available. We detected Mycena sequences in roots of all sampled Ericaceae plants. Our Mycena sequences clustered in four different groups distributed across the Mycena genus. Only one group could be assigned with confidence to a named species (M. galopus). Our Mycena sequences clustered with other Mycena sequences detected in roots of ericoid mycorrhizal plant species collected throughout Europe, America, and Australia. An isolate of M. galopus promoted growth of V. corymbosum seedlings in vitro regardless of external carbon supply in the media. Seedlings inoculated with M. galopus grew as well as those inoculated with the ericoid mycorrhizal fungus Rhizoscyphus ericae. Surprisingly, this M. galopus isolate colonized Vaccinium roots and formed distinctive peg-like structures. Our results suggest that Mycena species might operate along a saprotroph-symbiotic continuum with a range of ericoid mycorrhizal plant species. We discuss our results in terms of fungal partner recruitment by Ericaceae plants.

High-efficiency induction of soybean hairy roots and propagation of the soybean cyst nematode.

PubMed

Cho, H J; Farrand, S K; Noel, G R; Widholm, J M

2000-01-01

Cotyledon explants of 10 soybean [Glycine max (L.) Merr.] cultivars were inoculated with Agrobacterium rhizogenes strain K599 with and without binary vectors pBI121 or pBINm-gfp5-ER possessing both neomycin phosphotransferase II (nptII) and beta-glucuronidase (gus) or nptII and green fluorescent protein (gfp) genes, respectively. Hairy roots were produced from the wounded surface of 54-95% of the cotyledon explants on MXB selective medium containing 200 microg ml(-1) kanamycin and 500 microg ml(-1) carbenicillin. Putative individual transformed hairy roots were identified by cucumopine analysis and were screened for transgene incorporation using polymerase chain reaction. All of the roots tested were found to be co-transformed with T-DNA from the Ri-plasmid and the transgene from the binary vectors. Southern blot analysis confirmed the presence of the 35S-gfp5 gene in the plant genomes. Transgene expression was also confirmed by histochemical GUS assay and Western blot analysis for the GFP. Attempts to induce shoot formation from the hairy roots failed. Infection of hairy roots of the soybean cyst nematode (Heterodera glycines Ichinohe)-susceptible cultivar, Williams 82, with eggs of H. glycines race 1, resulted in the development of mature cysts about 4-5 weeks after inoculation. Thus the soybean cyst nematode could complete its entire life cycle in transformed soybean hairy-root cultures expressing GFP. This system should be ideal for testing genes that might impart resistance to soybean cyst nematode.

Effects of Glucosinolates and Flavonoids on Colonization of the Roots of Brassica napus by Azorhizobium caulinodans ORS571

PubMed Central

O'Callaghan, Kenneth J.; Stone, Philip J.; Hu, Xiaojia; Griffiths, D. Wynne; Davey, Michael R.; Cocking, Edward C.

2000-01-01

Plants of Brassica napus were assessed quantitatively for their susceptibility to lateral root crack colonization by Azorhizobium caulinodans ORS571(pXLGD4) (a rhizobial strain carrying the lacZ reporter gene) and for the concentration of glucosinolates in their roots by high-pressure liquid chromatography (HPLC). High- and low-glucosinolate-seed (HGS and LGS) varieties exhibited a relatively low and high percentage of colonized lateral roots, respectively. HPLC showed that roots of HGS plants contained a higher concentration of glucosinolates than roots of LGS plants. One LGS variety showing fewer colonized lateral roots than other LGS varieties contained a higher concentration of glucosinolates than other LGS plants. Inoculated HGS plants treated with the flavonoid naringenin showed significantly more colonization than untreated HGS plants. This increase was not mediated by a naringenin-induced lowering of the glucosinolate content of HGS plant roots, nor did naringenin induce bacterial resistance to glucosinolates or increase the growth of bacteria. The erucic acid content of seed did not appear to influence colonization by azorhizobia. Frequently, leaf assays are used to study glucosinolates and plant defense; this study provides data on glucosinolates and bacterial colonization in roots and describes a bacterial reporter gene assay tailored easily to the study of ecologically important phytochemicals that influence bacterial colonization. These data also form a basis for future assessments of the benefits to oilseed rape plants of interaction with plant growth-promoting bacteria, especially diazotrophic bacteria potentially able to extend the benefits of nitrogen fixation to nonlegumes. PMID:10788398

Microbial community induces a plant defense system under growing on the lunar regolith analogue

NASA Astrophysics Data System (ADS)

Zaetz, Irina; Mytrokhyn, Olexander; Lukashov, Dmitry; Mashkovska, Svitlana; Kozyrovska, Natalia; Foing, Bernard H.

The lunar rock considered as a potential source of chemical elements essential for plant nutrition, however, this substrate is of a low bioavailability. The use of microorganisms for decomposition of silicate rocks and stimulation of plant growth is a key idea in precursory scenario of growing pioneer plants for a lunar base (Kozyrovska et al., 2004; 2006; Zaetz et al., 2006). In model experiments a consortium of well-defined plant-associated bacteria were used for growing of French marigold (Tagetes patula L.) in anorthosite, analogous to a lunar rock. Inoculated plants appeared better seed germination, more fast development and also increased accumulation of K, Mg, Mn, Co, Cu and lowered level of the toxic Zn, Ni, Cr, comparing to control tagetes'. Bacteria regulate metal homeostasis in plants by changing their bioavailability and by stimulating of plant defense mechanisms. Inoculated plants were being accommodated to growth under stress conditions on anorthosite used as a substrate. In contrast, control plants manifested a heavy metal-induced oxidative stress, as quantified by protein carbonyl accumulation. Depending on the plant organ sampled and developmental stage there were increases or loses in the antioxidant enzyme activities (guaiacol peroxidase and glutathione-S-transferase). These changes were most evident in inoculated plants. Production of phenolic compounds, known as antioxidants and heavy metal chelators, is rised in variants of inoculated marigolds. Guaiacol peroxidase plays the main role, finally, in a reducing toxicity of heavy metals in plant leaves, while glutathione-S-transferase and phenolics overcome stress in roots.

Differential effects of Pseudomonas mendocina and Glomus intraradices on lettuce plants physiological response and aquaporin PIP2 gene expression under elevated atmospheric CO2 and drought.

PubMed

Alguacil, Maria Del Mar; Kohler, Josef; Caravaca, Fuensanta; Roldán, Antonio

2009-11-01

Arbuscular mycorrhizal (AM) symbiosis and plant-growth-promoting rhizobacterium (PGPR) can alleviate the effects of water stress in plants, but it is unknown whether these benefits can be maintained at elevated CO2. Therefore, we carried out a study where seedlings of Lactuca sativa were inoculated with the AM fungus (AMF) Glomus intraradices N.C. Schenk & G.S. Sm. or the PGPR Pseudomonas mendocina Palleroni and subjected to two levels of watering and two levels of atmospheric CO2 to ascertain their effects on plant physiological parameters and gene expression of one PIP aquaporin in roots. The inoculation with PGPR produced the greatest growth in lettuce plants under all assayed treatments as well as the highest foliar potassium concentration and leaf relative water content under elevated [CO2] and drought. However, under such conditions, the PIP2 gene expression remained almost unchanged. G. intraradices increased significantly the AMF colonization, foliar phosphorus concentration and leaf relative water content in plants grown under drought and elevated [CO2]. Under drought and elevated [CO2], the plants inoculated with G. intraradices showed enhanced expression of the PIP2 gene as compared to P. mendocina or control plants. Our results suggest that both microbial inoculation treatments could help to alleviate drought at elevated [CO2]. However, the PIP2 gene expression was increased only by the AMF but not by the PGPR under these conditions.

Improvement of cadmium phytoremediation by Centella asiatica L. after soil inoculation with cadmium-resistant Enterobacter sp. FM-1.

PubMed

Li, Yi; Liu, Kehui; Wang, Yang; Zhou, Zhenming; Chen, Chaoshu; Ye, Panhua; Yu, Fangming

2018-07-01

This study examined the potential of a cadmium-resistant Enterobacter sp. FM-1 to promote plant growth and assist in cadmium accumulation in both mine-type C. asiatica L. and non-mine type C. asiatica L. tissues in highly cadmium-polluted soils. The results indicated that Enterobacter sp. FM-1 significantly promoted growth and alleviated metal toxicity in both types of C. asiatica L. Meanwhile, inoculation with Enterobacter sp. FM-1 in contaminated soil can increased cadmium bioavailability in soil. Furthermore, it will increase plant uptake and the accumulation of cadmium in C. asiatica L. leaves, stems and roots compared to that in an uninoculated plant. However, mine-type C. asiatica L. had better cadmium tolerance than the non mine-type C. asiatica L. Because of its native metal-tolerant ability, which could easily grow and proliferate, and had a better performance under cadmium-contamination conditions. Additionally, inoculation with Enterobacter sp. FM-1 significantly enhanced the bioaccumulation factor (BAF) and the translocation factor (TF) values in both types of C. asiatica L. even under high cadmium concentration soil condition. Hence, based on higher BAF and TF values and strong cadmium accumulation in the leaves and stems, we concluded that inoculation with Enterobacter sp. FM-1 is potentially useful for the phytoremediation of cadmium-contaminated sites by Centella asiatica L. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of Sinorhizobium fredii strain Sneb183 on the biological control of soybean cyst nematode in soybean.

PubMed

Tian, Feng; Wang, Yuanyuan; Zhu, Xiaofeng; Chen, Lijie; Duan, Yuxi

2014-11-01

The soybean cyst nematode (SCN; Heterodera glycines) is a major detriment to soybean production. The endophytic bacterium Sinorhizobium fredii strain Sneb183 is known to inhibit the activity of SCN. In the present study, soybean seedlings were inoculated with Sneb183, to study the penetration juveniles, and their development inside the roots. The number of cysts in the soybean roots was also examined. The induced systemic resistance in soybean was also examined through the split-root system. Our results revealed that the number of juveniles and cysts significantly decreased as a result of Sneb183 inoculation. Sneb183 also prolonged the developmental stage of SCN in the root to 30 days as compared to 27 days in the control. Furthermore, the number of nematodes in each stage was lower in the Sneb183 treated plants than control plants. We also used a split-root system to show that the S. fredii strain Sneb183 induced a systemic resistance to SCN infection in soybean. The repression rate of SCN penetration was 38.75%. Our study showed that Sneb183 can be an effective biocontrol agent for managing SCN infestation in soybean. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of tropospheric ozone on loblolly pine seedlings inoculated with root infecting ophiostomatoid fungi.

PubMed

Chieppa, Jeff; Chappelka, Art; Eckhardt, Lori

2015-12-01

Seedlings from four loblolly pine (Pinus taeda L.) families were exposed in open-top chambers to charcoal-filtered air (CF), non-filtered air (NF) or air amended with ozone to 2 times ambient (2×). Two of the families used were selected for their tolerance to fungi associated with Southern Pine Decline while two were selected for their susceptibility. Seedlings were treated with five inoculation treatments: no wound (NW), wound only (W), wound + media (WM), Grosmannia huntii (GH) and Leptographium terebrantis (LT). After 118 days of exposure (AOT40 = 31 ppm-hr(-1) for 2× ozone) seedling volume, dry matter, chlorophyll content, water potential and lesions were measured and analyzed using ANOVA procedures. Our results indicate that seedlings selected for their susceptibility to root infecting ophiostomatoid fungi were also more sensitive to ozone. Overall lesion length was greater on seedlings exposed to elevated ozone concentrations but was not specific to either root infecting ophiostomatoid fungi. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization of plant growth-promoting traits of free-living diazotrophic bacteria and their inoculation effects on growth and nitrogen uptake of crop plants.

PubMed

Islam, Md Rashedul; Madhaiyan, M; Deka Boruah, Hari P; Yim, Woojong; Lee, Gillseung; Saravanan, V S; Fu, Qingling; Hu, Hongqing; Sa, Tongmin

2009-10-01

The search for diverse plant growth-promoting (PGP) diazotrophic bacteria is gaining momentum as efforts are made to exploit them as biofertilizers for various economically important crops. In the present study, 17 diazotrophic strains belonging to eight different genera isolated from rice paddy fields were screened for multiple PGP traits and evaluated for their inoculation effects on canola and rice plants. All of the strains tested positive for 1- aminocyclopropane-1-carboxylate (ACC) deaminase activity and production of indole 3-acetic acid (IAA) and ammonia (NH3). Additionally, four of the strains were able to solubilize phosphorus (P), five tested positive for zinc (Zn) solubilization and sulfur (S) oxidation, and eight strains produced siderophores. Based on the presence of multiple PGP traits, 10 strains were selected for inoculation studies. Treatment with Herbaspirillum sp. RFNB26 resulted in maximum root length (54.3%), seedling vigor, and dry biomass in canola, whereas Paenibacillus sp. RFNB4 exhibited the lowest activity under gnotobiotic conditions. However, under pot culture conditions, Paenibacillus sp. RFNB4 significantly increased plant height and dry biomass production by 42.3% and 29.5%, respectively. Canola plants and rhizosphere soils inoculated with Bacillus sp. RFNB6 exhibited significantly higher nitrogenase activity. In greenhouse experiments, Serratia sp. RFNB18 increased rice plant height by 35.1%, Xanthomonas sp. RFNB24 enhanced biomass production by 84.6%, and rice rhizosphere soils inoculated with Herbaspirillum sp. RFNB26 exhibited the highest nitrogenase activity. Our findings indicate that most of the selected strains possess multiple PGP properties that significantly improve the growth parameters of the two plants when tested under controlled conditions.

A Complex Molecular Interplay of Auxin and Ethylene Signaling Pathways Is Involved in Arabidopsis Growth Promotion by Burkholderia phytofirmans PsJN

PubMed Central

Poupin, María J.; Greve, Macarena; Carmona, Vicente; Pinedo, Ignacio

2016-01-01

Modulation of phytohormones homeostasis is one of the proposed mechanisms to explain plant growth promotion induced by beneficial rhizobacteria (PGPR). However, there is still limited knowledge about the molecular signals and pathways underlying these beneficial interactions. Even less is known concerning the interplay between phytohormones in plants inoculated with PGPR. Auxin and ethylene are crucial hormones in the control of plant growth and development, and recent studies report an important and complex crosstalk between them in the regulation of different plant developmental processes. The objective of this work was to study the role of both hormones in the growth promotion of Arabidopsis thaliana plants induced by the well-known PGPR Burkholderia phytofirmans PsJN. For this, the spatiotemporal expression patterns of several genes related to auxin biosynthesis, perception and response and ethylene biosynthesis were studied, finding that most of these genes showed specific transcriptional regulations after inoculation in roots and shoots. PsJN-growth promotion was not observed in Arabidopsis mutants with an impaired ethylene (ein2-1) or auxin (axr1–5) signaling. Even, PsJN did not promote growth in an ethylene overproducer (eto2), indicating that a fine regulation of both hormones signaling and homeostasis is necessary to induce growth of the aerial and root tissues. Auxin polar transport is also involved in growth promotion, since PsJN did not promote primary root growth in the pin2 mutant or under chemical inhibition of transport in wild type plants. Finally, a key role for ethylene biosynthesis was found in the PsJN-mediated increase in root hair number. These results not only give new insights of PGPR regulation of plant growth but also are also useful to understand key aspects of Arabidopsis growth control. PMID:27148317

Symbiotic Efficiency of Native Rhizobia Nodulating Common Bean (Phaseolus vulgaris L.) in Soils of Western Kenya

PubMed Central

Kawaka, Fanuel; Dida, Mathews M.; Opala, Peter A.; Ombori, Omwoyo; Maingi, John; Osoro, Newton; Muthini, Morris; Amoding, Alice; Mukaminega, Dative; Muoma, John

2014-01-01

This study was conducted to determine the abundance and symbiotic efficiency of native rhizobia nodulating common bean in Kisumu and Kakamega, Kenya. Soil sampling was carried out in three farms that had been used for growing common bean for at least two seasons and one fallow land with no known history of growing common bean or inoculation. Abundance of soil rhizobia and symbiotic efficiency (SE) were determined in a greenhouse experiment. Native rhizobia populations ranged from 3.2 × 101 to 3.5 × 104 cells per gram of soil. Pure bacterial cultures isolated from fresh and healthy root nodules exhibited typical characteristics of Rhizobium sp. on yeast extract mannitol agar media supplemented with Congo red. Bean inoculation with the isolates significantly (p < 0.05) increased the shoot dry weight and nitrogen (N) concentration and content. The SE of all the native rhizobia were higher when compared to a reference strain, CIAT 899 (67%), and ranged from 74% to 170%. Four isolates had SE above a second reference strain, Strain 446 (110%). Our results demonstrate the presence of native rhizobia that are potentially superior to the commercial inoculants. These can be exploited to enhance bean inoculation programmes in the region. PMID:27355005

Phytoextraction of heavy metal polluted soils using Sedum plumbizincicola inoculated with metal mobilizing Phyllobacterium myrsinacearum RC6b.

PubMed

Ma, Ying; Rajkumar, Mani; Luo, Yongming; Freitas, Helena

2013-10-01

The aim of this study was to investigate the effects of metal mobilizing plant-growth beneficial bacterium Phyllobacterium myrsinacearum RC6b on plant growth and Cd, Zn and Pb uptake by Sedum plumbizincicola under laboratory conditions. Among a collection of metal-resistant bacteria, P. myrsinacearum RC6b was specifically chosen as a most favorable metal mobilizer based on its capability of mobilizing high concentrations of Cd, Zn and Pb in soils. P. myrsinacearum RC6b exhibited a high degree of resistance to Cd (350 mg L(-1)), Zn (1000 mg L(-1)) and Pb (1200 mg L(-1)). Furthermore, P. myrsinacearum RC6b showed multiple plant growth beneficial features including the production of 1-aminocyclopropane-1-carboxylic acid deaminase, indole-3-acetic acid, siderophore and solubilization of insoluble phosphate. Inoculation of P. myrsinacearum RC6b significantly increased S. plumbizincicola growth and organ metal concentrations except Pb, which concentration was lower in root and stem of inoculated plants. The results suggest that the metal mobilizing P. myrsinacearum RC6b could be used as an effective inoculant for the improvement of phytoremediation in multi-metal polluted soils. Copyright © 2013 Elsevier Ltd. All rights reserved.

Purple corn-associated rhizobacteria with potential for plant growth promotion.

PubMed

Castellano-Hinojosa, A; Pérez-Tapia, V; Bedmar, E J; Santillana, N

2018-05-01

Purple corn (Zea mays var. purple amylaceum) is a native variety of the Peruvian Andes, cultivated at 3000 m since the pre-Inca times without N fertilization. We aimed to isolate and identify native plant growth-promoting rhizobacteria (PGPR) for future microbial-based inoculants. Eighteen strains were isolated from the rhizosphere of purple corn plants grown without N fertilization in Ayacucho (Peru). The 16S rRNA gene clustered the 18 strains into nine groups that contained species of Bacillus, Stenotrophomonas, Achromobacter, Paenibacillus, Pseudomonas and Lysinibacillus. A representative strain from each group was selected and assayed for N 2 fixation, phosphate solubilization, indole acetic and siderophore production, 1-aminocyclopropane-1-carboxylic acid deaminase activity and biocontrol abilities. Inoculation of purple corn plants with single and combined strains selected after a principal component analysis caused significant increases in root and shoot dry weight, total C and N contents of the plants. PGPRs can support growth and crop production of purple corn in the Peruvian Andes and constitute the base for microbial-based inoculants. This study enlarges our knowledge on plant-microbial interactions in high altitude mountains and provides new applications for PGPR inoculation in purple amylaceum corn, which is part of the staple diet for the native Quechua communities. © 2018 The Society for Applied Microbiology.

Arbuscular mycorrhizal fungi alleviate arsenic toxicity to Medicago sativa by influencing arsenic speciation and partitioning.

PubMed

Li, Jinglong; Sun, Yuqing; Jiang, Xuelian; Chen, Baodong; Zhang, Xin

2018-08-15

In a pot experiment, Medicago sativa inoculated with/without arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis were grown in four levels (0, 10, 25, and 75 mg/kg) of arsenic (As)-polluted soil to investigate the influences of AM symbiosis on plant As tolerance. The results showed that mycorrhizal inoculation significantly increased plant biomass, while As addition decreased mycorrhizal colonization and hyphal length density. Mycorrhizal inoculation dramatically improved plant phosphorus (P) nutrition, restricted As uptake and retained more As in roots by upregulating the expression of the AM-induced P transporter gene MsPT4 and the metallothionein gene MsMT2. High soil As content downregulated MsPT4 expression. Dimethylarsenic acid (DMA) was detected only in the shoots of mycorrhizal plants, indicating that AM fungi likely play an essential role in As detoxification by biological methylation. The present investigation allowed deeper insights into the As detoxification mechanisms of AM associations and demonstrated the important role of AM fungi in plant resistance under As-contaminated conditions. Copyright © 2018 Elsevier Inc. All rights reserved.

Enhanced arsenic uptake and polycyclic aromatic hydrocarbon (PAH)-dissipation using Pteris vittata L. and a PAH-degrading bacterium.

PubMed

Sun, Lu; Zhu, Ganghui; Liao, Xiaoyong

2018-05-15

This study examined the effects of P. vittata and a polycyclic aromatic hydrocarbon (PAH)-degrading bacterium (Alcaligenes sp.) on arsenic (As) uptake and phenanthrene dissipation. Bacterial inoculation substantially increased As accumulation in plants by 27.8% (frond) and 27.5% (root) at 60d, respectively, compared with the non-inoculated treatment, although temporal change of As translocation and reduction in plants was observed. Bacterial inoculation positively affected plants by improving growth, nutrition and antioxidative activities, and helped to modify soil As availability to the plants, which may benefit in plant tolerance and As accumulation. Plant and bacteria association enhanced phenanthrene dissipation from the soil, with the highest dissipation rate of 96.4% at 60d in the rhizosphere, which might be associated with enhanced bacterial population and activity inspired by the growth of plant. The result reveals that combination of P. vittata and PAH-degrading bacteria can promote As accumulation and phenanthrene dissipation, and can be exploited as a promising strategy for As and PAH co-contamination remediation. Copyright © 2017 Elsevier B.V. All rights reserved.

Understanding the development of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth

PubMed Central

Remans, Tony; Thijs, Sofie; Truyens, Sascha; Weyens, Nele; Schellingen, Kerim; Keunen, Els; Gielen, Heidi; Cuypers, Ann; Vangronsveld, Jaco

2012-01-01

Background and Scope Plant responses to the toxic effects of soil contaminants, such as excess metals or organic substances, have been studied mainly at physiological, biochemical and molecular levels, but the influence on root system architecture has received little attention. Nevertheless, the precise position, morphology and extent of roots can influence contaminant uptake. Here, data are discussed that aim to increase the molecular and ecological understanding of the influence of contaminants on root system architecture. Furthermore, the potential of plant-associated bacteria to influence root growth by their growth-promoting and stress-relieving capacities is explored. Methods Root growth parameters of Arabidopsis thaliana seedlings grown in vertical agar plates are quantified. Mutants are used in a reverse genetics approach to identify molecular components underlying quantitative changes in root architecture after exposure to excess cadmium, copper or zinc. Plant-associated bacteria are isolated from contaminated environments, genotypically and phenotypically characterized, and used to test plant root growth improvement in the presence of contaminants. Key Results The molecular determinants of primary root growth inhibition and effects on lateral root density by cadmium were identified. A vertical split-root system revealed local effects of cadmium and copper on root development. However, systemic effects of zinc exposure on root growth reduced both the avoidance of contaminated areas and colonization of non-contaminated areas. The potential for growth promotion and contaminant degradation of plant-associated bacteria was demonstrated by improved root growth of inoculated plants exposed to 2,4-di-nitro-toluene (DNT) or cadmium. Conclusions Knowledge concerning the specific influence of different contaminants on root system architecture and the molecular mechanisms by which this is achieved can be combined with the exploitation of plant-associated bacteria to influence root development and increase plant stress tolerance, which should lead to more optimal root systems for application in phytoremediation or safer biomass production. PMID:22634257

Understanding the development of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth.

PubMed

Remans, Tony; Thijs, Sofie; Truyens, Sascha; Weyens, Nele; Schellingen, Kerim; Keunen, Els; Gielen, Heidi; Cuypers, Ann; Vangronsveld, Jaco

2012-07-01

Plant responses to the toxic effects of soil contaminants, such as excess metals or organic substances, have been studied mainly at physiological, biochemical and molecular levels, but the influence on root system architecture has received little attention. Nevertheless, the precise position, morphology and extent of roots can influence contaminant uptake. Here, data are discussed that aim to increase the molecular and ecological understanding of the influence of contaminants on root system architecture. Furthermore, the potential of plant-associated bacteria to influence root growth by their growth-promoting and stress-relieving capacities is explored. Root growth parameters of Arabidopsis thaliana seedlings grown in vertical agar plates are quantified. Mutants are used in a reverse genetics approach to identify molecular components underlying quantitative changes in root architecture after exposure to excess cadmium, copper or zinc. Plant-associated bacteria are isolated from contaminated environments, genotypically and phenotypically characterized, and used to test plant root growth improvement in the presence of contaminants. The molecular determinants of primary root growth inhibition and effects on lateral root density by cadmium were identified. A vertical split-root system revealed local effects of cadmium and copper on root development. However, systemic effects of zinc exposure on root growth reduced both the avoidance of contaminated areas and colonization of non-contaminated areas. The potential for growth promotion and contaminant degradation of plant-associated bacteria was demonstrated by improved root growth of inoculated plants exposed to 2,4-di-nitro-toluene (DNT) or cadmium. Knowledge concerning the specific influence of different contaminants on root system architecture and the molecular mechanisms by which this is achieved can be combined with the exploitation of plant-associated bacteria to influence root development and increase plant stress tolerance, which should lead to more optimal root systems for application in phytoremediation or safer biomass production.

Plant growth and arbuscular mycorrhizae development in oil sands processing by-products.

PubMed

Boldt-Burisch, Katja; Naeth, M Anne; Schneider, Uwe; Schneider, Beate; Hüttl, Reinhard F

2018-04-15

Soil pollutants such as hydrocarbons can induce toxic effects in plants and associated arbuscular mycorrhizal fungi (AMF). This study was conducted to evaluate if the legume Lotus corniculatus and the grass Elymus trachycaulus and arbuscular mycorrhizal fungi could grow in two oil sands processing by-products after bitumen extraction from the oil sands in northern Alberta, Canada. Substrate treatments were coarse tailings sand (CTS), a mix of dry mature fine tailings (MFT) with CTS (1:1) and Pleistocene sandy soil (hydrocarbon free); microbial treatments were without AMF, with AMF and AMF plus soil bacteria isolated from oil sands reclamation sites. Plant biomass, root morphology, leaf water content, shoot tissue phosphorus content and mycorrhizal colonization were evaluated. Both plant species had reduced growth in CTS and tailings mix relative to sandy soil. AMF frequency and intensity in roots of E. trachycaulus was not influenced by soil hydrocarbons; however, it decreased significantly over time in roots of L. corniculatus without bacteria in CTS. Mycorrhizal inoculation alone did not significantly improve plant growth in CTS and tailings mix; however, inoculation with mycorrhizae plus bacteria led to a significantly positive response of both plant species in CTS. Thus, combined inoculation with selected mycorrhizae and bacteria led to synergistic effects. Such combinations may be used in future to improve plant growth in reclamation of CTS and tailings mix. Copyright © 2017 Elsevier B.V. All rights reserved.

Assessment of DAPG-producing Pseudomonas fluorescens for Management of Meloidogyne incognita and Fusarium oxysporum on Watermelon

PubMed Central

Meyer, Susan L. F.; Everts, Kathryne L.; Gardener, Brian McSpadden; Masler, Edward P.; Abdelnabby, Hazem M. E.; Skantar, Andrea M.

2016-01-01

Pseudomonas fluorescens isolates Clinto 1R, Wayne 1R, and Wood 1R, which produce the antibiotic 2,4-diacetylphloroglucinol (DAPG), can suppress soilborne diseases and promote plant growth. Consequently, these beneficial bacterial isolates were tested on watermelon plants for suppression of Meloidogyne incognita (root-knot nematode: RKN) and Fusarium oxysporum f. sp. niveum (Fon). In a greenhouse trial, Wayne 1R root dip suppressed numbers of RKN eggs per gram root on ‘Charleston Gray’ watermelon by 28.9%. However, in studies focused on ‘Sugar Baby’ watermelon, which is commercially grown in Maryland, a Wayne 1R root dip did not inhibit RKN reproduction or plant death caused by Fon. When all three isolates were applied as seed coats, plant stand in the greenhouse was reduced up to 60% in treatments that included Fon ± P. fluorescens, and eggs per gram root did not differ among treatments. In a microplot trial with Clinto 1R and Wayne 1R root dips, inoculation with P. fluorescens and/or Fon resulted in shorter vine lengths than treatment with either P. fluorescens isolate plus RKN. Root weights, galling indices, eggs per gram root, and second-stage juvenile (J2) numbers in soil were similar among all RKN-inoculated treatments, and fruit production was not affected by treatment. Plant death was high in all treatments. These studies demonstrated that the tested P. fluorescens isolates resulted in some inhibition of vine growth in the field, and were not effective for enhancing plant vigor or suppressing RKN or Fon on watermelon. PMID:27168652

An evaluation of the wilt-causing bacterium Ralstonia solanacearum as a potential biological control agent for the alien Kahili ginger (Hedychium gardnerianum) in Hawaiian forests

USGS Publications Warehouse

1999-01-01

Kahili ginger (Hedychium gardnerianum) is an invasive weed in tropical forests in Hawaii and elsewhere. Bacterial wilt caused by the ginger strain of Ralstonia(=Pseudomonas) solanacearum systemically infects edible ginger (Zingiber officinale) and ornamental gingers (Hedychium spp.), causing wilt in infected plants. The suitability of R. solanacearum as a biological control agent for kahili ginger was investigated by inoculating seedlings and rooted cuttings of native forest plants, ornamental ginger, and solanaceous species to confirm host specificity. Inoculation via stem injection or root wounding with a bacterial–water suspension was followed by observation for 8 weeks. Inoculations on H. gardnerianum were then carried out in ohia-lehua (Metrosideros polymorpha) wet forests of Hawaii Volcanoes National Park to determine the bacterium's efficacy in the field. No native forest or solanaceous species developed wilt or other symptoms during the study. The bacterium caused limited infection near the inoculation site on H. coronarium, Z. zerumbet, Heliconia latispatha, and Musa sapientum. However, infection did not become systemic in any of these species, and normal growth resumed following appearance of initial symptoms. All inoculated H. gardnerianum plants developed irreversible chlorosis and severe wilting 3–4 weeks following inoculation. Systemic infection also caused death and decay of rhizomes. Most plants were completely dead 16–20 weeks following inoculation. The destructiveness of the ginger strain of R. solanacearum to edible ginger has raised questions regarding its use for biological control. However, because locations of kahili ginger infestations are often remote, the risk of contaminating edible ginger plantings is unlikely. The ability of this bacterium to cause severe disease in H. gardnerianum in the field, together with its lack of virulence in other ginger species, contributes to its potential as a biological control agent.

Effectiveness of rhizobacteria containing ACC deaminase for growth promotion of peas (Pisum sativum) under drought conditions.

PubMed

Zahir, Z A; Munir, A; Asghar, H N; Shaharoona, B; Arshad, M

2008-05-01

A series of experiments were conducted to assess the effectiveness of rhizobacteria containing 1-aminocyclopropane- 1-carboxylate (ACC) deaminase for growth promotion of peas under drought conditions. Ten rhizobacteria isolated from the rhizosphere of different crops (peas, wheat, and maize) were screened for their growth promoting ability in peas under axenic condition. Three rhizobacterial isolates, Pseudomonas fluorescens biotype G (ACC-5), P. fluorescens (ACC-14), and P. putida biotype A (Q-7), were selected for pot trial on the basis of their source, ACC deaminase activity, root colonization, and growth promoting activity under axenic conditions. Inoculated and uninoculated (control) seeds of pea cultivar 2000 were sown in pots (4 seeds/pot) at different soil moisture levels (25, 50, 75, and 100% of field capacity). Results revealed that decreasing the soil moisture levels from 100 to 25% of field capacity significantly decreased the growth of peas. However, inoculation of peas with rhizobacteria containing ACC deaminase significantly decreased the "drought stress imposed effects" on growth of peas, although with variable efficacy at different moisture levels. At the lowest soil moisture level (25% field capacity), rhizobacterial isolate Pseudomonas fluorescens biotype G (ACC-5) was found to be more promising compared with the other isolates, as it caused maximum increases in fresh weight, dry weight, root length, shoot length, number of leaves per plant, and water use efficiency on fresh and dry weight basis (45, 150, 92, 45, 140, 46, and 147%, respectively) compared with respective uninoculated controls. It is highly likely that rhizobacteria containing ACC deaminase might have decreased the drought-stress induced ethylene in inoculated plants, which resulted in better growth of plants even at low moisture levels. Therefore, inoculation with rhizobacteria containing ACC deaminase could be helpful in eliminating the inhibitory effects of drought stress on the growth of peas.

Mutualism in a Reduced Gravity Environment (MuRGE)

NASA Technical Reports Server (NTRS)

Haire, Timothy C.

2010-01-01

Mutualism in a Reduced Gravity Environment (MuRGE) is a ground research study to determine the feasibility of assessing fungi-plant (Piriformospora indica-Arabidopsis thaliana) interactions in microgravity. Seeds from the plant Arabiddospsis thaliana (At) will be grown in the presence of Piriformospora indica (Pi) an endophytic Sebacinacae family fungus. Pi is capable of colonizing the roots of a wide variety of plant species, including non-mycorrhizal hosts like At, and promoting plant growth similarly to AMF (arbusuclar mychorrizal fungi) unlike most AMF, Pi is not an obligate plant symbiont and can be grown in the absence of a host. In the presence of a suitable plant host, Pi can attach to and colonize root tips. Interaction visualization is accomplished with strong autofluorescence in the roots, followed by root colonization via fungal hyphae, and chlamydospore production. Increased root growth can be observed even before root colonization is detectable. In addition, Pi chlamydospores generated from axenic culture in microgravity will be used to inoculate roots of At grown in 1g to determine the effect of microgravity upon the inherent virulence or beneficial effects. Based on recent reports of increased virulence of S. typhimurium, P. aeruginosa, and S. Pneumoniae in reduced gravity, differences in microbial pathogenic responses and host plant systemic acquired resistance are expected. The focus of this project within MuRGE involved the development P. indica culture media evaluation and microscopy protocol development. High, clean spore harvest yields for the detection of fungi-plant interactions microscopically was the immediate goal of this experiment.

Mycorrhizal aspects in slope stabilisation

NASA Astrophysics Data System (ADS)

Graf, Frank

2016-04-01

In order to re-colonise and stabilise slopes affected by superficial soil failure with plants essential requirements have to be met: the plants must grow the plants must survive sustainably plant succession must start and continuously develop These requirements, however, are anything but easy given, particularly under the often hostile environmental conditions dominating on bare and steep slopes. Mycorrhizal fungi, the symbiotic partners of almost all plants used in eco-engineering, are said to improve the plants' ability to overcome periods governed by strongly (growth) limiting factors. Subsequently, results of investigations are presented of mycorrhizal effects on different plant and soil functions related to eco-engineering in general and soil and slope stabilisation in particular. Generally, inoculation yielded higher biomass of the host plants above as well as below ground. Furthermore, the survival rate was higher for mycorrhized compared to non-mycorrhized plants, particularly under extreme environmental conditions. However, the scale of the mycorrhizal impact may be species specific of both the plant host as well as the fungal partner(s) and often becomes evident only after a certain time lag. Depending on the plant-fungus combination the root length per soil volume was found to be between 0 and 2.5 times higher for inoculated compared to non-inoculated specimens. On an alpine graded ski slope the survival of inoculated compared to non-treated Salix herbacea cuttings was significant after one vegetation period only for one of the three added mycorrhizal fungus species. However, after three years all of the inoculated plantlets performed significantly better than the non-inoculated controls. The analysis of the potential for producing and stabilising soil aggregates of five different ectomycorrhizal fungi showed high variation and, for the species Inocybe lacera, no significant difference compared to untreated soil. Furthermore, inoculation of Salix appendiculata with ecto, arbuscular, and the combination of the two mycorrhizal types revealed different effects in respect of aggregate stabilisation as well as above and below ground biomass production of the host plant. Only the ecto-mycorrhized plants significantly increased soil aggregate stability compared to non-inoculated willows. Significantly higher production of host plant biomass was restricted to roots and the inoculation with arbuscular mycorrhiza. Additionally, there are successional processes in mycorrhizal communities in the way that perennial plants do have other fungal partners in their juvenile, prime, and senescent living phase, respectively. It was found that, particularly, in the initial phase of the re-colonisation and development of a protective vegetation cover, the lack of relevant (ecto-) mycorrhizal fungi considerably decelerate or even stop succession processes. Conclusively, with regard to support and accelerate plant growth and the re-colonisation and stabilisation of slopes within the scope of eco-engineering measures it is necessary to select the fungal species based on sound information. This may include ecology and sociology as well as the potential for aggregate formation depending on the plant species used.

ROOT TRAITS AND NODULATION OF RECOMBINANT INBRED BEAN LINES FROM A ‘JAMAPA × CALIMA’ POPULATION INOCULATED WITH TWO STRAINS OF RHIZOBIUM

USDA-ARS?s Scientific Manuscript database

Bean cultivars of Andean and Middle American origin often have contrasting above-ground traits. Less is known, however, of possible differences in root traits of beans from different gene pools. Recombinant inbred lines (RIL) derived from a cross between the Andean cultivar ‘Calima’ and the Middle A...

Pyracantha ‘Mohave’ fruit infection by Phytophthora ramorum and transmission of the pathogen from infected fruit to roots of Viburnum tinus

USDA-ARS?s Scientific Manuscript database

We conducted a study to investigate the potential role of Pyracantha ‘Mohave’fruit as a source of inoculum for subsequent root infection of a susceptible host by Phytophthora ramorum. An examination of the fleshy pulp revealed an abundance of chlamydospores in fruit following inoculation with P. ra...

Wheat bran soil inoculant of sumateran nematode-trapping fungi as biocontrol agents of the root-knot nematode meloidogyne incognita on deli tobacco (nicotiana tabaccum l) cv. deli 4

NASA Astrophysics Data System (ADS)

Dwi Sri Hastuti, Liana; Faull, Jane

2018-03-01

A pot experiment was carried out to test the effectiveness of nematode-trapping fungi (NTF) isolated from Sumatera for controlling infection by the root-knot nematode (RKN) on Deli tobacco plant. Wheat bran soil containing 109 conidia of Arthrobotrys. oligospora, Candellabrella musiformis and Dactylella eudermata was added to the soil as a dry inoculum. Carbofuran was also applied as chemical agent and comparison treatment. Seedling tobacco (Nicotiana tabacum L.) cv. Deli 4 was inoculated with root knot (Meloidogyne incognita Chitwood.) seven days after the plant were transplanted to the pots. A. oligospora, C. musiformis and D. eudermata were found to be reliable as biocontrol agents, reducing the number of vermiform nematodes, swollen root, sausage shaped and galls in tobacco plant after 7, 15 and 30 days of infection with M. incognita. Treatment with NTF produced results that were comparable with Carbofuran® as a control agent in the reduction of the number of infections in tobacco plant caused by M. incognita in Nicotiana tabacum var. Deli 4. They also optimize the growth of the tobacco plants especially up to 15 days after infection.

Comparative photochemistry activity and antioxidant responses in male and female Populus cathayana cuttings inoculated with arbuscular mycorrhizal fungi under salt

PubMed Central

Wu, Na; Li, Zhen; Wu, Fei; Tang, Ming

2016-01-01

We investigated the impact of arbuscular mycorrhizal fungi (AMF) on the morphology and physiology of two genders of the typical dioecious plant Populus cathayana under salt stress. We conducted a pot experiment containing seedlings of the two genders that were subjected to salt or non-salt and filled with soil that was either inoculated with Rhizophagus intraradices or not. The results showed that males had higher mycorrhizal dependency than females. Salt stress decreased growth, the relative water content and chlorophyll fluorescence. Meanwhile, salt increased the superoxide radical (O2−), and hydrogen peroxide (H2O2) contents and antioxidant enzyme activities. Mycorrhizal male seedlings performed better than females in shoot morphological growth under both conditions and in chlorophyll fluorescence parameters, O2− and H2O2 contents, MDA concentration, proline content and antioxidant enzymes activities under salt stress. In females, under saline conditions, a lower MDA concentration and H2O2, O2− and proline contents were observed in the leaves and roots. In addition, inoculated female plants performed better in chlorophyll fluorescence parameters than non-inoculated plants. AMF inoculation had either slight or no effects on the performance of females. These findings suggested that when subjected to stress and AMF, differences in the genders existed, followed by the alleviation of the damage to P. cathayana by AMF via improving growth and photosynthesis and antioxidant systems under salt stress. PMID:27898056

Phytomanagement of Cd-contaminated soils using maize (Zea mays L.) assisted by plant growth-promoting rhizobacteria.

PubMed

Moreira, Helena; Marques, Ana P G C; Franco, Albina R; Rangel, António O S S; Castro, Paula M L

2014-01-01

Zea mays (L.) is a crop widely cultivated throughout the world and can be considered suitable for phytomanagement due to its metal resistance and energetic value. In this study, the effect of two plant growth-promoting rhizobacteria, Ralstonia eutropha and Chryseobacterium humi, on growth and metal uptake of Z. mays plants in soils contaminated with up to 30 mg Cd kg(-1) was evaluated. Bacterial inoculation increased plant biomass up to 63% and led to a decrease of up to 81% in Cd shoot levels (4-88 mg Cd kg(-1)) and to an increase of up to 186% in accumulation in the roots (52-134 mg Cd kg(-1)). The rhizosphere community structure changed throughout the experiment and varied with different levels of Cd soil contamination, as revealed by molecular biology techniques. Z. mays plants inoculated with either of the tested strains may have potential application in a strategy of soil remediation, in particular short-term phytostabilization, coupled with biomass production for energy purposes.

Changes in soil solution Zn and pH and uptake of Zn by arbuscular mycorrhizal red clover in Zn-contaminated soil.

PubMed

Li, X; Christie, P

2001-01-01

Red clover plants inoculated with Glomus mosseae were grown in a sterile pasture soil containing 50 mg Zn kg(-1) in 'Plexiglas' (acrylic) containers with nylon net partitions (30 microm mesh) designed to separate the soil into a central root zone and two outer zones for hyphal growth with no root penetration. Two porous plastic soil moisture samplers were installed in each pot, one in the root compartment and the other in one of the hyphal compartments. The soil in the outer compartments was amended with one of the four application rates of Zn (as ZnSO4) ranging from 0 to 1000 mg kg(-1). Non-mycorrhizal controls were included, and there were five replicates of each treatment in a randomised block in a glasshouse. Uninoculated plants received supplementary P to avoid yield limitation due to low soil P status. Plants grew in the central compartment for nine weeks. Soil moisture samples were collected 4, 24 and 62 days after sowing to monitor changes in the Zn concentration and pH of the soil solution. At harvest, the mean mycorrhizal infection rate of inoculated plants ranged from 29% to 34% of total root length and was little affected by Zn application. Root and shoot yields were not affected by mycorrhizal infection. Plant Zn concentration and uptake were lower in mycorrhizal plants than non-mycorrhizal controls, and this effect was more pronounced with increasing Zn application rate to the soil. Soil solution Zn concentrations were lower and pH values were higher in mycorrhizal treatments than non-mycorrhizal controls and the mycorrhiza effect was more pronounced at higher Zn application rates. The protective effect of mycorrhiza against plant Zn uptake may have been associated with changes in Zn solubility mediated by changes in the soil solution pH, or by immobilisation of Zn in the extraradical mycelium.

Enhancement of growth and yield of tomato by Rhodopseudomonas sp. under greenhouse conditions.

PubMed

Lee, Kang-Hyeong; Koh, Rae-Hyun; Song, Hong-Gyu

2008-12-01

A greenhouse test was carried out to examine the effects on tomato growth of application of purple non-sulfur bacterium Rhodopseudomonas sp. which had enhanced germination and growth of tomato seed under axenic conditions. The shoot length of tomato plant inoculated by Rhodopseudomonas sp. KL9 increased by 34.6% compared to that of control in 8 weeks of cultivation. During the same period, this strain increased 120.6 and 78.6% of dry weight of shoot and root of tomato plants, respectively. The formation ratio of tomato fruit from flower was also raised by inoculation of KL9. In addition, Rhodopseudomonas sp. KL9 treatment enhanced the fresh weight and lycopene content in the harvested tomato fruits by 98.3 and 48.3%, respectively compared to those of the uninoculated control. When the effect on the indigenous bacterial community and fate of the inoculated Rhodopseudomonas sp. KL9 were monitored by denaturing gradient gel electrophoresis analysis, its application did not affect the native bacterial community in tomato rhizosphere soil, but should be repeated to maintain its population size. This bacterial capability may be applied as an environment-friendly biofertilizer to cultivation of high quality tomato and other crops including lycopene-containing vegetables and fruits.

Arbuscular Mycorrhizal Fungi Promote the Growth of Ceratocarpus arenarius (Chenopodiaceae) with No Enhancement of Phosphorus Nutrition

PubMed Central

Bai, Dengsha; Chen, Yinglong; Feng, Gu

2012-01-01

The mycorrhizal status of plants in the Chenopodiaceae is not well studied with a few controversial reports. This study examined arbuscular mycorrhizal (AM) colonization and growth response of Ceratocarpus arenarius in the field and a greenhouse inoculation trial. The colonization rate of AM fungi in C. arenarius in in-growth field cores was low (around 15%). Vesicles and intraradical hyphae were present during all growth stages, but no arbuscules were observed. Sequencing analysis of the large ribosomal rDNA subunit detected four culturable Glomus species, G. intraradices, G. mosseae, G. etunicatum and G. microaggregatum together with eight unculturable species belong to the Glomeromycota in the root system of C. arenarius collected from the field. These results establish the mycotrophic status of C. arenarius. Both in the field and in the greenhouse inoculation trial, the growth of C. arenarius was stimulated by the indigenous AM fungal community and the inoculated AM fungal isolates, respectively, but the P uptake and concentration of the mycorrhizal plants did not increase significantly over the controls in both experiments. Furthermore, the AM fungi significantly increased seed production. Our results suggest that an alternative reciprocal benefit to carbon-phosphorus trade-off between AM fungi and the chenopod plant might exist in the extremely arid environment. PMID:22957011

Responses of Guava Plants to Inoculation with Arbuscular Mycorrhizal Fungi in Soil Infested with Meloidogyne enterolobii.

PubMed

Campos, Maryluce Albuquerque da Silva; da Silva, Fábio Sérgio Barbosa; Yano-Melo, Adriana Mayumi; de Melo, Natoniel Franklin; Pedrosa, Elvira Maria Régis; Maia, Leonor Costa

2013-09-01

In the Northeast of Brazil, expansion of guava crops has been impaired by Meloidogyne enterolobii that causes root galls, leaf fall and plant death. Considering the fact that arbuscular mycorrhizal Fungi (AMF) improve plant growth giving protection against damages by plant pathogens, this work was carried out to select AMF efficient to increase production of guava seedlings and their tolerance to M. enterolobii. Seedlings of guava were inoculated with 200 spores of Gigaspora albida, Glomus etunicatum or Acaulospora longula and 55 days later with 4,000 eggs of M. enterolobii. The interactions between the AMF and M. enterolobii were assessed by measuring leaf number, aerial dry biomass, CO2 evolution and arbuscular and total mycorrhizal colonization. In general, plant growth was improved by the treatments with A. longula or with G. albida. The presence of the nematode decreased arbuscular colonization and increased general enzymatic activity. Higher dehydrogenase activity occurred with the A. longula treatment and CO2 evolution was higher in the control with the nematode. More spores and higher production of glomalin-related soil proteins were observed in the treatment with G. albida. The numbers of galls, egg masses and eggs were reduced in the presence of A. longula. Inoculation with this fungus benefitted plant growth and decreased nematode reproduction.

The combination of compost addition and arbuscular mycorrhizal inoculation produced positive and synergistic effects on the phytomanagement of a semiarid mine tailing.

PubMed

Kohler, J; Caravaca, F; Azcón, R; Díaz, G; Roldán, A

2015-05-01

A field experiment was carried out to assess the effectiveness of combining mycorrhizal inoculation with a native AM fungus (Glomus sp.) and the addition of an urban organic waste compost (OWC) applied at two rates (0.5 and 2.0% (w:w)), with regard to promoting the establishment of Anthyllis cytisoides L. seedlings in a heavy metal polluted mine tailing, as well as stimulating soil microbial functions. The results showed that the combined use of the highest dose of OWC and AM inoculation significantly increased shoot biomass - by 64% - compared to the control value. However, the separate use of each treatment had no effect on the shoot biomass of this shrub species. At the 2% rate, OWC enhanced root colonisation by the introduced fungus as well as soil nutrient content and soil dehydrogenase and ß-glucosidase activities. The combined treatment increased the uptake of Zn and Mn in shoots, although only Zn reached excessive or potentially toxic levels. This study demonstrates that the combination of organic amendment and an AM fungus is a suitable tool for the phytomanagement of degraded mine tailings, although its effectiveness is dependent on the dose of the amendment. Copyright © 2015 Elsevier B.V. All rights reserved.

Responses of Guava Plants to Inoculation with Arbuscular Mycorrhizal Fungi in Soil Infested with Meloidogyne enterolobii

PubMed Central

Campos, Maryluce Albuquerque da Silva; da Silva, Fábio Sérgio Barbosa; Yano-Melo, Adriana Mayumi; de Melo, Natoniel Franklin; Pedrosa, Elvira Maria Régis; Maia, Leonor Costa

2013-01-01

In the Northeast of Brazil, expansion of guava crops has been impaired by Meloidogyne enterolobii that causes root galls, leaf fall and plant death. Considering the fact that arbuscular mycorrhizal Fungi (AMF) improve plant growth giving protection against damages by plant pathogens, this work was carried out to select AMF efficient to increase production of guava seedlings and their tolerance to M. enterolobii. Seedlings of guava were inoculated with 200 spores of Gigaspora albida, Glomus etunicatum or Acaulospora longula and 55 days later with 4,000 eggs of M. enterolobii. The interactions between the AMF and M. enterolobii were assessed by measuring leaf number, aerial dry biomass, CO2 evolution and arbuscular and total mycorrhizal colonization. In general, plant growth was improved by the treatments with A. longula or with G. albida. The presence of the nematode decreased arbuscular colonization and increased general enzymatic activity. Higher dehydrogenase activity occurred with the A. longula treatment and CO2 evolution was higher in the control with the nematode. More spores and higher production of glomalin-related soil proteins were observed in the treatment with G. albida. The numbers of galls, egg masses and eggs were reduced in the presence of A. longula. Inoculation with this fungus benefitted plant growth and decreased nematode reproduction. PMID:25288951

Phenylacetic acid-producing Rhizoctonia solani represses the biosynthesis of nematicidal compounds in vitro and influences biocontrol of Meloidogyne incognita in tomato by Pseudomonas fluorescens strain CHA0 and its GM derivatives.

PubMed

Siddiqui, I A; Shaukat, S S

2005-01-01

The aim of the present investigation was to determine the influence of Rhizoctonia solani and its pathogenicity factor on the production of nematicidal agent(s) by Pseudomonas fluorescens strain CHA0 and its GM derivatives in vitro and nematode biocontrol potential by bacterial inoculants in tomato. One (Rs7) of the nine R. solani isolates from infected tomato roots inhibited seedling emergence and caused root rot in tomato. Thin layer chromatography revealed that culture filtrates of two isolates (Rs3 and Rs7) produced brown spots at Rf-values closely similar to synthetic phenylacetic acid (PAA), a phytotoxic factor. Filtrates from isolate Rs7, amended with the growth medium of P. fluorescens, markedly repressed nematicidal activity and PhlA'-'LacZ reporter gene expression of the bacteria in vitro. On the contrary, isolate Rs4 enhanced nematicidal potential of a 2,4-diacetylphloroglucinol overproducing mutant, CHA0/pME3424, of P. fluorescens strain CHA0 in vitro. Therefore, R. solani isolates Rs4 and Rs7 were tested more rigorously for their potential to influence biocontrol effectiveness of the bacterial agents. Methanol extract of the culture filtrates of PAA-producing isolate Rs7 resulting from medium amended with phenylalanine enhanced fungal repression of the production of nematicidal agents by bacteria, while amendments with zinc or molybdenum eliminated such fungal repression, thereby restoring bacterial potential to cause nematode mortality in vitro. A pot experiment was carried out, 3-week-old tomato seedlings were infested with R. solani isolates Rs4 or Rs7 and/or inoculated with Meloidogyne incognita, the root-knot nematode. The infested soil was treated with aqueous cell suspensions (10(8) CFU) of P. fluorescens strain CHA0 or its GM derivatives or left untreated (as a control). Observations taken 45 days after nematode inoculation revealed that, irrespective of the bacterial treatments, galling intensity per gram of fresh tomato roots was markedly higher in soil amended with isolate Rs4 than in Rs7-amended soils. Soil amendments with R. solani and the bacterial antagonists resulted in substantial reductions of the number of galls per gram of root. These results are contradictory to those obtained under in vitro conditions where culture filtrates of PAA-positive Rs7 repressed the production of nematicidal compounds. Plants grown in Rs7-amended soils, with or without bacterial inoculants, had lesser shoot and root weights than plants grown in nonamended or Rs4-amended soils. Moreover, amendments with Rs7 substantially retarded root growth and produced necrotic lesions that reduced the number of entry sites for invasion and subsequent infection by nematodes. Populations of P. fluorescens in the tomato rhizosphere were markedly higher in Rs7-amended soils. PAA-producing virulent R. solani drastically affects the potential of P. fluorescens to cause death of M. incognita juveniles in vitro and influences bacterial effectiveness to suppress nematodes in tomato roots. As most agricultural soils are infested with root-infecting fungi, including R. solani, it is likely that some PAA-producing isolates of the fungus may also be isolated from such soils. The inhibitory effect of PAA-producing R. solani on the biosynthesis of nematicidal agent(s) critical in biocontrol may reduce or even eliminate the effectiveness of fluorescent pseudomonads against root-knot nematodes, both in nursery beds and in field conditions. Introduction of bacterial inoculants, for the control of any plant pathogen, should be avoided in soils infested with PAA-producing R. solani. Alternatively, the agents could be applied together with an appropriate quantity of fungicide or chemicals such as zinc to create an environment more favourable for bacterial biocontrol action.

[INFLUENCE OF AZOSPIRILLUM BRASILENSE 10/1 ON ASSOCIATIVE NITROGEN FIXATION AND INTRAVARIETAL POLYMORPHISM OF SPRING TRITICALE].

PubMed

Patika, V P; Nadkernichna, O V; Shahovnina, O O

2015-01-01

It is shown, that the perspective Ukrainian sorts of spring triticale characterizes by considerable polymorphism by associative N2-fixing ability in root zone of plants. Application of active strain Azospirillum brasilense 10/1 promotes the decline of variability of this sign within the limits of sort, increase potential nitrogen activity is on the average in 3,2-4,7 times and also distributing normalizations in the selections of the inoculated plants.

Anti-tumor activities of decursinol angelate and decursin from Angelica gigas.

PubMed

Lee, Sanghyun; Lee, Yeon Sil; Jung, Sang Hoon; Shin, Kuk Hyun; Kim, Bak-Kwang; Kang, Sam Sik

2003-09-01

The in vivo anti-tumor activities of decursinol angelate (1) and decursin (2) isolated from the roots of Angelica gigas were investigated. These two compounds, when administered consecutively for 9 days at 50 and 100 mg/kg i.p. in mice, caused a significant increase in the life span and a significant decrease in the tumor weight and volume of mice inoculated with Sarcoma-180 tumor cells. These results suggest that decursinol angelate (1) and decursin (2) from A. gigas have anti-tumor activities.

Assessment of Culturable Tea Rhizobacteria Isolated from Tea Estates of Assam, India for Growth Promotion in Commercial Tea Cultivars

PubMed Central

Dutta, Jintu; Handique, Pratap J.; Thakur, Debajit

2015-01-01

In the present study, 217 rhizobacterial isolates were obtained from six different tea estates of Assam, India and subjected to preliminary in vitro plant growth promotion (PGP) screening for indole acetic acid (IAA) production, phosphate solubilization, siderophore production and ammonia production. Fifty isolates showed all the PGP traits and five isolates did not exhibit any PGP traits. These 50 potential isolates were further analyzed for quantitative estimation of the PGP traits along with the aminocyclopropane-1-carboxylate (ACC) deaminase, protease and cellulose production. After several rounds of screening, four rhizobacteria were selected based on their maximum ability to produce in vitro PGP traits and their partial 16S rRNA gene sequence analysis revealed that they belong to Enterobacter lignolyticus strain TG1, Burkholderia sp. stain TT6, Bacillus pseudomycoides strain SN29 and Pseudomonas aeruginosa strain KH45. To evaluate the efficacy of these four rhizobacteria as plant growth promoters, three different commercially important tea clones TV1, TV19, and TV20 plants were inoculated with these rhizobacteria in greenhouse condition and compared to the uninoculated control plants. Though, all the rhizobacterial treatments showed an increase in plant growth compared to control but the multivariate PCA analysis confirmed more growth promotion by TG1 and SN29 strains than the other treatments in all three clones. To validate this result, the fold change analysis was performed and it revealed that the tea clone TV19 plants inoculated with the E. lignolyticus strain TG1 showed maximum root biomass production with an increase in 4.3-fold, shoot biomass with increase in 3.1-fold, root length by 2.2-fold and shoot length by 1.6-fold. Moreover, two way ANOVA analysis also revealed that rhizobacterial treatment in different tea clones showed the significant increase (P < 0.05) in growth promotion compared to the control. Thus, this study indicates that the potential of these indigenous plant growth promoting rhizobacteria isolates to use as microbial inoculation or biofertilizer for growth promotion of tea crops. PMID:26617590

Plant-fungus competition for nitrogen erases mycorrhizal growth benefits of Andropogon gerardii under limited nitrogen supply.

PubMed

Püschel, David; Janoušková, Martina; Hujslová, Martina; Slavíková, Renata; Gryndlerová, Hana; Jansa, Jan

2016-07-01

Considered to play an important role in plant mineral nutrition, arbuscular mycorrhizal (AM) symbiosis is a common relationship between the roots of a great majority of plant species and glomeromycotan fungi. Its effects on the plant host are highly context dependent, with the greatest benefits often observed in phosphorus (P)-limited environments. Mycorrhizal contribution to plant nitrogen (N) nutrition is probably less important under most conditions. Moreover, inasmuch as both plant and fungi require substantial quantities of N for their growth, competition for N could potentially reduce net mycorrhizal benefits to the plant under conditions of limited N supply. Further compounded by increased belowground carbon (C) drain, the mycorrhizal costs could outweigh the benefits under severe N limitation. Using a field AM fungal community or a laboratory culture of Rhizophagus irregularis as mycorrhizal inoculants, we tested the contribution of mycorrhizal symbiosis to the growth, C allocation, and mineral nutrition of Andropogon gerardii growing in a nutrient-poor substrate under variable N and P supplies. The plants unambiguously competed with the fungi for N when its supply was low, resulting in no or negative mycorrhizal growth and N-uptake responses under such conditions. The field AM fungal communities manifested their potential to improve plant P nutrition only upon N fertilization, whereas the R. irregularis slightly yet significantly increased P uptake of its plant host (but not the host's growth) even without N supply. Coincident with increasing levels of root colonization by the AM fungal structures, both inoculants invariably increased nutritional and growth benefits to the host with increasing N supply. This, in turn, resulted in relieving plant P deficiency, which was persistent in non-mycorrhizal plants across the entire range of nutrient supplies.

Arbuscular mycorrhiza formation and its function under elevated atmospheric O3: A meta-analysis.

PubMed

Wang, Shuguang; Augé, Robert M; Toler, Heather D

2017-07-01

We quantitatively evaluated the effects of elevated O 3 on arbuscular mycorrhiza (AM) formation and on AM role in promoting plant growth in regard to several moderating variables (O 3 levels, O 3 exposure duration, plant types, AM fungi family, and additional stress) by means of meta-analysis of published data. The analysis consisted of 117 trials representing 20 peer-reviewed articles and 16 unpublished trials. Relative to non-mycorrhizal controls, AM inoculation did not significantly alter plant growth (shoot biomass, root biomass, total biomass and plant height) when O 3 concentration was less than 80 ppb, but at concentrations above 80 ppb symbiosis was associated with increases of 68% in shoot biomass and 131% in root biomass. AM effects on plant growth were affected by the duration of O 3 exposure but did not differ much with AM fungi taxa or plant type. AM symbiosis has also led to higher yields under O 3 stress, relative to the non-mycorrhizal plants, and the AM effects have been more pronounced as O 3 concentration increases. As with biomass, AM effects on yield have been affected by the duration of O 3 exposure, with the greatest increase (100%) occurring at 61-90 d. AM-induced promotion of yield differed with fungal species but not with plant type or other abiotic stress. Colonization of roots by AM fungi has been negatively affected by elevated O 3 compared to ambient O 3 ; total mycorrhizal colonization rate (MCR), arbuscular MCR, vesicular MCR and hyphal coil MCR declined as O 3 levels rose. AM colonization rates were affected by duration of O 3 exposure, plant type, AM fungal taxa and other concurrent stresses in most cases. The analysis showed that AM inoculation has the potential to ameliorate detrimental effects of elevated O 3 on plant growth and productivity, despite colonization rates being negatively affected by elevated O 3 . Copyright © 2017. Published by Elsevier Ltd.

Influence of nutrient signals and carbon allocation on the expression of phosphate and nitrogen transporter genes in winter wheat (Triticum aestivum L.) roots colonized by arbuscular mycorrhizal fungi

PubMed Central

Tian, Hui; Yuan, Xiaolei; Duan, Jianfeng; Li, Wenhu; Zhai, Bingnian; Gao, Yajun

2017-01-01

Arbuscular mycorrhizal (AM) colonization of plant roots causes the down-regulation of expression of phosphate (Pi) or nitrogen (N) transporter genes involved in direct nutrient uptake pathways. The mechanism of this effect remains unknown. In the present study, we sought to determine whether the expression of Pi or N transporter genes in roots of winter wheat colonized by AM fungus responded to (1) Pi or N nutrient signals transferred from the AM extra-radical hyphae, or (2) carbon allocation changes in the AM association. A three-compartment culture system, comprising a root compartment (RC), a root and AM hyphae compartment (RHC), and an AM hyphae compartment (HC), was used to test whether the expression of Pi or N transporter genes responded to nutrients (Pi, NH4+ and NO3-) added only to the HC. Different AM inoculation density treatments (roots were inoculated with 0, 20, 50 and 200 g AM inoculum) and light regime treatments (6 hours light and 18 hours light) were established to test the effects of carbon allocation on the expression of Pi or N transporter genes in wheat roots. The expression of two Pi transporter genes (TaPT4 and TaPHT1.2), five nitrate transporter genes (TaNRT1.1, TaNRT1.2, TaNRT2.1, TaNRT2.2, and TaNRT2.3), and an ammonium transporter gene (TaAMT1.2) was quantified using real-time polymerase chain reaction. The expression of TaPT4, TaNRT2.2, and TaAMT1.2 was down-regulated by AM colonization only when roots of host plants received Pi or N nutrient signals. However, the expression of TaPHT1.2, TaNRT2.1, and TaNRT2.3 was down-regulated by AM colonization, regardless of whether there was nutrient transfer from AM hyphae. The expression of TaNRT1.2 was also down-regulated by AM colonization even when there was no nutrient transfer from AM hyphae. The present study showed that an increase in carbon consumption by the AM fungi did not necessarily result in greater down-regulation of expression of Pi or N transporter genes. PMID:28207830

Influence of nutrient signals and carbon allocation on the expression of phosphate and nitrogen transporter genes in winter wheat (Triticum aestivum L.) roots colonized by arbuscular mycorrhizal fungi.

PubMed

Tian, Hui; Yuan, Xiaolei; Duan, Jianfeng; Li, Wenhu; Zhai, Bingnian; Gao, Yajun

2017-01-01

Arbuscular mycorrhizal (AM) colonization of plant roots causes the down-regulation of expression of phosphate (Pi) or nitrogen (N) transporter genes involved in direct nutrient uptake pathways. The mechanism of this effect remains unknown. In the present study, we sought to determine whether the expression of Pi or N transporter genes in roots of winter wheat colonized by AM fungus responded to (1) Pi or N nutrient signals transferred from the AM extra-radical hyphae, or (2) carbon allocation changes in the AM association. A three-compartment culture system, comprising a root compartment (RC), a root and AM hyphae compartment (RHC), and an AM hyphae compartment (HC), was used to test whether the expression of Pi or N transporter genes responded to nutrients (Pi, NH4+ and NO3-) added only to the HC. Different AM inoculation density treatments (roots were inoculated with 0, 20, 50 and 200 g AM inoculum) and light regime treatments (6 hours light and 18 hours light) were established to test the effects of carbon allocation on the expression of Pi or N transporter genes in wheat roots. The expression of two Pi transporter genes (TaPT4 and TaPHT1.2), five nitrate transporter genes (TaNRT1.1, TaNRT1.2, TaNRT2.1, TaNRT2.2, and TaNRT2.3), and an ammonium transporter gene (TaAMT1.2) was quantified using real-time polymerase chain reaction. The expression of TaPT4, TaNRT2.2, and TaAMT1.2 was down-regulated by AM colonization only when roots of host plants received Pi or N nutrient signals. However, the expression of TaPHT1.2, TaNRT2.1, and TaNRT2.3 was down-regulated by AM colonization, regardless of whether there was nutrient transfer from AM hyphae. The expression of TaNRT1.2 was also down-regulated by AM colonization even when there was no nutrient transfer from AM hyphae. The present study showed that an increase in carbon consumption by the AM fungi did not necessarily result in greater down-regulation of expression of Pi or N transporter genes.

Mutation of praR in Rhizobium leguminosarum enhances root biofilms, improving nodulation competitiveness by increased expression of attachment proteins.

PubMed

Frederix, Marijke; Edwards, Anne; Swiderska, Anna; Stanger, Andrew; Karunakaran, Ramakrishnan; Williams, Alan; Abbruscato, Pamela; Sanchez-Contreras, Maria; Poole, Philip S; Downie, J Allan

2014-08-01

In Rhizobium leguminosarum bv. viciae, quorum-sensing is regulated by CinR, which induces the cinIS operon. CinI synthesizes an AHL, whereas CinS inactivates PraR, a repressor. Mutation of praR enhanced biofilms in vitro. We developed a light (lux)-dependent assay of rhizobial attachment to roots and demonstrated that mutation of praR increased biofilms on pea roots. The praR mutant out-competed wild-type for infection of pea nodules in mixed inoculations. Analysis of gene expression by microarrays and promoter fusions revealed that PraR represses its own transcription and mutation of praR increased expression of several genes including those encoding secreted proteins (the adhesins RapA2, RapB and RapC, two cadherins and the glycanase PlyB), the polysaccharide regulator RosR, and another protein similar to PraR. PraR bound to the promoters of several of these genes indicating direct repression. Mutations in rapA2, rapB, rapC, plyB, the cadherins or rosR did not affect the enhanced root attachment or nodule competitiveness of the praR mutant. However combinations of mutations in rapA, rapB and rapC abolished the enhanced attachment and nodule competitiveness. We conclude that relief of PraR-mediated repression determines a lifestyle switch allowing the expression of genes that are important for biofilm formation on roots and the subsequent initiation of infection of legume roots. © 2014 The Authors. Molecular Microbiology published by John Wiley & Sons Ltd.

Axonal degeneration and regeneration in sensory roots in a genital herpes model.

PubMed

Soffer, D; Martin, J R

1989-01-01

In a mouse model of genital herpes simplex virus type 2 (HSV-2) infection, roots of the lower spinal cord were examined 5 days to 6 months after inoculation. Using immunoperoxidase methods on paraffin sections, viral antigen was found in sensory ganglia, their proximal roots and distal nerves on days 5 and 6 after infection. In Epon sections, most mice had focal sensory root abnormalities in lower thoracic, lumbar or sacral levels. At days 7 and 10, lesions showed chiefly nerve fiber degeneration, particularly of large myelinated fibers. At 2 weeks, lesions contained relatively large bundles of small unmyelinated fibers with immature axon-Schwann cell relationships. From 3 to 6 weeks, lesions again contained many more small unmyelinated fibers than normal but, in increasing proportions, axons in bundles were isolated from their neighbors by Schwann cell cytoplasm, and Schwann cells having 1:1 relationships with axons showed mesaxon or thin myelin sheath formation. At later times, the proportion of small unmyelinated axons decreased in parallel with increased numbers of small myelinated axons. By 6 months, affected roots showed a relative reduction in large myelinated fibers, increased proportions of small myelinated fibers and Schwann cell nuclei. Numbers of unmyelinated fibers were reduced relative to 3- to 6-week lesions. Axonal degeneration and regeneration appears to be the chief pathological change in sensory roots in this model. If regenerated fibers arise from latently infected neurons, then establishment of latency is not a relatively silent event, but is associated with major long-lasting, morphologically detectable effects.

Arbuscular mycorrhizal fungi enhance the copper tolerance of Tagetes patula through the sorption and barrier mechanisms of intraradical hyphae.

PubMed

Zhou, Xishi; Fu, Lei; Xia, Yan; Zheng, Luqing; Chen, Chen; Shen, Zhenguo; Chen, Yahua

2017-07-19

Arbuscular mycorrhizal fungi (AMF) are widespread soil fungi that can form endosymbiotic structures with the root systems of most plants and can improve the tolerance of host plants to heavy metals. In the present study, we investigated the effects of AMF (Glomus coronatum) inoculation on the tolerance of Tagetes patula L. to Cu. Almost all of the non-mycorrhizal plants exposed to 100 μM Cu died after 3 d, whereas phytotoxicity was only observed in mycorrhizal plants that were exposed to Cu concentrations greater than 100 μM. Analysing the dynamic accumulation of Cu indicated that, after 7 d of Cu exposure, less Cu was absorbed or accumulated by mycorrhizal plants than by control plants, and significantly less Cu was translocated to the shoots. Meanwhile, analysing the root morphology, the integrity of the root plasma membranes, the photosynthesis rate, and the content of essential elements of plants growing in cultures with 50 μM Cu revealed that AMF inoculation markedly alleviated the toxic effects of Cu stress on root system activity, photosynthesis rate, and mineral nutrient accumulation. In addition, to understand the Cu allocation, an energy spectrum analysis of Cu content at the transverse section of root tips was conducted and subsequently provided direct evidence that intraradical hyphae at the root endodermis could selectively immobilise large amounts of Cu. Indeed, the sorption and barrier mechanisms of AMF hyphae reduce Cu toxicity in the roots of T. patula and eventually enhance the plants' Cu tolerance.

Early physiological responses of Pinus pinea L. seedlings infected by Heterobasidion sp.pl. in an ozone-enriched atmospheric environment.

PubMed

Pollastrini, Martina; Luchi, Nicola; Michelozzi, Marco; Gerosa, Giacomo; Marzuoli, Riccardo; Bussotti, Filippo; Capretti, Paolo

2015-03-01

The presence of the American root-rot disease fungus Heterobasidion irregulare Garbel. & Otrosina was detected in Italian coastal pine forests (Pinus pinea L.) in addition to the common native species Heterobasidion annosum (Fries) Brefeld. High levels of tropospheric ozone (O3) as an atmospheric pollutant are usually experienced in Mediterranean pine forests. To explore the effect of interaction between the two Heterobasidion species and ozone pollution on P. pinea, an open-top chamber (OTC) experiment was carried out. Five-year-old P. pinea seedlings were inoculated with the fungal species considered (H. irregulare, H. annosum and mock-inoculation as control), and then exposed in charcoal-filtered open-top chambers (CF-OTC) and non-filtered ozone-enriched chambers (NF+) from July to the first week of August 2010 at the experimental facilities of Curno (North Italy). Fungal inoculation effects in an ozone-enriched environment were assessed as: (i) the length of the inoculation lesion; (ii) chlorophyll a fluorescence (ChlF) responses; and (iii) analysis of resin terpenes. Results showed no differences on lesion length between fungal and ozone treatments, whereas the short-term effects of the two stress factors on ChlF indicate an increased photosynthetic efficiency, thus suggesting the triggering of compensation/repair processes. The total amount of resin terpenes is enhanced by fungal infection of both species, but depressed by ozone to the levels observed in mock-inoculated plants. Variations in terpene profiles were also induced by stem base inoculations and ozone treatment. Ozone might negatively affect terpene defences making plants more susceptible to pathogens and insects. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Rhizobial infection in Adesmia bicolor (Fabaceae) roots.

PubMed

Bianco, Luciana

2014-09-01

The native legume Adesmia bicolor shows nitrogen fixation efficiency via symbiosis with soil rhizobia. The infection mechanism by means of which rhizobia infect their roots has not been fully elucidated to date. Therefore, the purpose of the present study was to identify the infection mechanism in Adesmia bicolor roots. To this end, inoculated roots were processed following conventional methods as part of our root anatomy study, and the shape and distribution of root nodules were analyzed as well. Neither root hairs nor infection threads were observed in the root system, whereas infection sites-later forming nodules-were observed in the longitudinal sections. Nodules were found to form between the main root and the lateral roots. It can be concluded that in Adesmia bicolor, a bacterial crack entry infection mechanism prevails and that such mechanism could be an adaptive strategy of this species which is typical of arid environments.