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Sample records for arbuscular mycorrhizal ecology

  1. Community assembly and coexistence in communities of arbuscular mycorrhizal fungi

    PubMed Central

    Vályi, Kriszta; Mardhiah, Ulfah; Rillig, Matthias C; Hempel, Stefan

    2016-01-01

    Arbuscular mycorrhizal fungi are asexual, obligately symbiotic fungi with unique morphology and genomic structure, which occupy a dual niche, that is, the soil and the host root. Consequently, the direct adoption of models for community assembly developed for other organism groups is not evident. In this paper we adapted modern coexistence and assembly theory to arbuscular mycorrhizal fungi. We review research on the elements of community assembly and coexistence of arbuscular mycorrhizal fungi, highlighting recent studies using molecular methods. By addressing several points from the individual to the community level where the application of modern community ecology terms runs into problems when arbuscular mycorrhizal fungi are concerned, we aim to account for these special circumstances from a mycocentric point of view. We suggest that hierarchical spatial structure of arbuscular mycorrhizal fungal communities should be explicitly taken into account in future studies. The conceptual framework we develop here for arbuscular mycorrhizal fungi is also adaptable for other host-associated microbial communities. PMID:27093046

  2. Arbuscular mycorrhizal fungi communities from tropical Africa reveal strong ecological structure.

    PubMed

    Rodríguez-Echeverría, Susana; Teixeira, Helena; Correia, Marta; Timóteo, Sérgio; Heleno, Ruben; Öpik, Maarja; Moora, Mari

    2017-01-01

    Understanding the distribution and diversity of arbuscular mycorrhizal fungi (AMF) and the rules that govern AMF assemblages has been hampered by a lack of data from natural ecosystems. In addition, the current knowledge on AMF diversity is biased towards temperate ecosystems, whereas little is known about other habitats such as dry tropical ecosystems. We explored the diversity and structure of AMF communities in grasslands, savannas, dry forests and miombo in a protected area under dry tropical climate (Gorongosa National Park, Mozambique) using 454 pyrosequencing. In total, 147 AMF virtual taxa (VT) were detected, including 22 VT new to science. We found a high turnover of AMF with ˂ 12% of VT present in all vegetation types. Forested areas supported more diverse AMF communities than savannas and grassland. Miombo woodlands had the highest AMF richness, number of novel VT, and number of exclusive and indicator taxa. Our data reveal a sharp differentiation of AMF communities between forested areas and periodically flooded savannas and grasslands. This marked ecological structure of AMF communities provides the first comprehensive landscape-scale evidence that, at the background of globally low endemism of AMF, local communities are shaped by regional processes including environmental filtering by edaphic properties and natural disturbance.

  3. Amino Acid Uptake in Arbuscular Mycorrhizal Plants

    PubMed Central

    Whiteside, Matthew D.; Garcia, Maria O.; Treseder, Kathleen K.

    2012-01-01

    We examined the extent to which arbuscular mycorrhizal (AM) fungi root improved the acquisition of simple organic nitrogen (ON) compounds by their host plants. In a greenhouse-based study, we used quantum dots (fluorescent nanoparticles) to assess uptake of each of the 20 proteinaceous amino acids by AM-colonized versus uncolonized plants. We found that AM colonization increased uptake of phenylalanine, lysine, asparagine, arginine, histidine, methionine, tryptophan, and cysteine; and reduced uptake of aspartic acid. Arbuscular mycorrhizal colonization had the greatest effect on uptake of amino acids that are relatively rare in proteins. In addition, AM fungi facilitated uptake of neutral and positively-charged amino acids more than negatively-charged amino acids. Overall, the AM fungi used in this study appeared to improve access by plants to a number of amino acids, but not necessarily those that are common or negatively-charged. PMID:23094070

  4. Seasonal dynamics of arbuscular mycorrhizal fungi in differing wetland habitats.

    PubMed

    Bohrer, Kelly E; Friese, Carl F; Amon, James P

    2004-10-01

    The dynamics and role of arbuscular mycorrhizal fungi (AMF) have been well described in terrestrial ecosystems; however, little is known about how the dynamics of AMF are related to the ecology of wetland ecosystems. The seasonal dynamics of arbuscular mycorrhizal (AM) colonization within different wetland habitats were examined in this study to determine the factors that influence AM associations and to further assess the ecological role of AMF in wetlands. Fen and marsh habitats of four wetlands in west central Ohio were sampled monthly from March to September. AMF were found at all four sites for each month sampled and were present in all of the dominant plant species. A significant effect of month (P<0.001) on AM colonization did occur and was attributable to maximum colonization levels in the spring and minimum levels in late summer. This trend existed in all four wetlands in both fen and marsh habitats,regardless of variation in water levels, percent soil moisture, or available phosphorus levels. Because abiotic factors had minimal influence on AM colonization variation and the level of AM colonization paralleled plant growth patterns, we conclude that the AM seasonal dynamic was in response to plant phenology. Our data suggest that AM associations in temperate fen and marsh habitats are prevalent in the spring during new root and vegetative growth, even for plants experiencing flooded conditions. Evidence of an overriding AM seasonal trend indicates that future studies should include a seasonal component to better assess the role and distribution ofAMF in wetland ecosystems.

  5. Growth model for arbuscular mycorrhizal fungi.

    PubMed

    Schnepf, A; Roose, T; Schweiger, P

    2008-07-06

    In order to quantify the contribution of arbuscular mycorrhizal (AM) fungi to plant phosphorus nutrition, the development and extent of the external fungal mycelium and its nutrient uptake capacity are of particular importance. We develop and analyse a model of the growth of AM fungi associated with plant roots, suitable for describing mechanistically the effects of the fungi on solute uptake by plants. The model describes the development and distribution of the fungal mycelium in soil in terms of the creation and death of hyphae, tip-tip and tip-hypha anastomosis, and the nature of the root-fungus interface. It is calibrated and corroborated using published experimental data for hyphal length densities at different distances away from root surfaces. A good agreement between measured and simulated values was found for three fungal species with different morphologies: Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders; Glomus sp.; and Acaulospora laevis Gerdemann & Trappe associated with Trifolium subterraneum L. The model and findings are expected to contribute to the quantification of the role of AM fungi in plant mineral nutrition and the interpretation of different foraging strategies among fungal species.

  6. Arbuscular mycorrhizal fungal communities in sub-Saharan savannas of Benin, West Africa, as affected by agricultural land use intensity and ecological zone.

    PubMed

    Tchabi, Atti; Coyne, Danny; Hountondji, Fabien; Lawouin, Louis; Wiemken, Andres; Oehl, Fritz

    2008-04-01

    The rapid decline of soil fertility of cultivated lands in the sub-Saharan savannas of West Africa is considered to be the main cause of the increasingly severe constraints of food production. The soils in this tropical area are highly fragile, and crop yields are limited by characteristically low levels of available phosphorus. Under such preconditions, the multiple benefits of the arbuscular mycorrhizal (AM) symbiosis are likely to play a pivotal role for maintaining natural soil fertility by enhancing plant nutrient use efficiency, plant health, and stabilization of a favorable soil structure. Thus, it is important to explore the impact of the commonly applied farming practices on the native AM fungal community. In the present study, we determined the AM fungal species composition in three ecological zones differing by an increasingly prolonged dry season from South to North, from the Southern Guinea Savanna (SG), to the Northern Guinea Savanna (NG), to the Sudan Savanna (SU). In each zone, four "natural" and four "cultivated" sites were selected. "Natural" sites were three natural forest savannas (at least 25-30 years old) and a long-term fallow (6-7 years old). "Cultivated" sites comprised a field with yam (Dioscorea spp.) established during the first year after forest clearance, a field under mixed cropping with maize (Zea mays) and peanut (Arachis hypogaea), a field under peanut, and a field under cotton (Gossypium hirsutum) which was the most intensively managed crop. Soil samples were collected towards the end of the wet season in each zone. AM fungal spores were extracted and morphologically identified. Soil subsamples were used to inoculate AM fungal trap cultures using Stylosanthes guianensis and Brachiaria humidicola as host plants to monitor AM root colonization and spore formation over 10 and 24 months, respectively. A total of 60 AM fungal species were detected, with only seven species sporulating in the trap cultures. Spore density and species

  7. Calcium opens the dialogue between plants and arbuscular mycorrhizal fungi.

    PubMed

    Navazio, Lorella; Mariani, Paola

    2008-04-01

    Calcium ion is considered a ubiquitous second messenger in all eukaryotic cells. Analysis of intracellular Ca(2+) concentration dynamics has demonstrated its signalling role in plant cells in response to a wide array of environmental cues. The implication of Ca(2+) in the early steps of the arbuscular mycorrhizal symbiosis has been frequently claimed, mainly by analogy with what firmly demonstrated in the rhizobium-legume symbiosis. We recently documented transient Ca(2+) changes in plant cells challenged with diffusible molecules released by arbuscular mycorrhizal fungi. Ca(2+) measurements by the recombinant aequorin method provided new insights into the molecular communications between plants and these beneficial fungi.

  8. Arbuscular mycorrhizal fungi in alleviation of salt stress: a review

    PubMed Central

    Evelin, Heikham; Kapoor, Rupam; Giri, Bhoopander

    2009-01-01

    Background Salt stress has become a major threat to plant growth and productivity. Arbuscular mycorrhizal fungi colonize plant root systems and modulate plant growth in various ways. Scope This review addresses the significance of arbuscular mycorrhiza in alleviation of salt stress and their beneficial effects on plant growth and productivity. It also focuses on recent progress in unravelling biochemical, physiological and molecular mechanisms in mycorrhizal plants to alleviate salt stress. Conclusions The role of arbuscular mycorrhizal fungi in alleviating salt stress is well documented. This paper reviews the mechanisms arbuscular mycorrhizal fungi employ to enhance the salt tolerance of host plants such as enhanced nutrient acquisition (P, N, Mg and Ca), maintenance of the K+ : Na+ ratio, biochemical changes (accumulation of proline, betaines, polyamines, carbohydrates and antioxidants), physiological changes (photosynthetic efficiency, relative permeability, water status, abscissic acid accumulation, nodulation and nitrogen fixation), molecular changes (the expression of genes: PIP, Na+/H+ antiporters, Lsnced, Lslea and LsP5CS) and ultra-structural changes. Theis review identifies certain lesser explored areas such as molecular and ultra-structural changes where further research is needed for better understanding of symbiosis with reference to salt stress for optimum usage of this technology in the field on a large scale. This review paper gives useful benchmark information for the development and prioritization of future research programmes. PMID:19815570

  9. Cover cropping impacts on arbuscular mycorrhizal fungi and soil aggregation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cover crops are a management tool which can extend the period of time that a living plant is growing and conducting photosynthesis. This is critical for soil health, because most of the soil organisms, particularly the arbuscular mycorrhizal fungi, are limited by carbon. Research, on-farm, and demon...

  10. Phosphorus and Nitrogen Regulate Arbuscular Mycorrhizal Symbiosis in Petunia hybrida

    PubMed Central

    Nouri, Eva; Breuillin-Sessoms, Florence; Feller, Urs; Reinhardt, Didier

    2014-01-01

    Phosphorus and nitrogen are essential nutrient elements that are needed by plants in large amounts. The arbuscular mycorrhizal symbiosis between plants and soil fungi improves phosphorus and nitrogen acquisition under limiting conditions. On the other hand, these nutrients influence root colonization by mycorrhizal fungi and symbiotic functioning. This represents a feedback mechanism that allows plants to control the fungal symbiont depending on nutrient requirements and supply. Elevated phosphorus supply has previously been shown to exert strong inhibition of arbuscular mycorrhizal development. Here, we address to what extent inhibition by phosphorus is influenced by other nutritional pathways in the interaction between Petunia hybrida and R. irregularis. We show that phosphorus and nitrogen are the major nutritional determinants of the interaction. Interestingly, the symbiosis-promoting effect of nitrogen starvation dominantly overruled the suppressive effect of high phosphorus nutrition onto arbuscular mycorrhiza, suggesting that plants promote the symbiosis as long as they are limited by one of the two major nutrients. Our results also show that in a given pair of symbiotic partners (Petunia hybrida and R. irregularis), the entire range from mutually symbiotic to parasitic can be observed depending on the nutritional conditions. Taken together, these results reveal complex nutritional feedback mechanisms in the control of root colonization by arbuscular mycorrhizal fungi. PMID:24608923

  11. Phosphorus and nitrogen regulate arbuscular mycorrhizal symbiosis in Petunia hybrida.

    PubMed

    Nouri, Eva; Breuillin-Sessoms, Florence; Feller, Urs; Reinhardt, Didier

    2014-01-01

    Phosphorus and nitrogen are essential nutrient elements that are needed by plants in large amounts. The arbuscular mycorrhizal symbiosis between plants and soil fungi improves phosphorus and nitrogen acquisition under limiting conditions. On the other hand, these nutrients influence root colonization by mycorrhizal fungi and symbiotic functioning. This represents a feedback mechanism that allows plants to control the fungal symbiont depending on nutrient requirements and supply. Elevated phosphorus supply has previously been shown to exert strong inhibition of arbuscular mycorrhizal development. Here, we address to what extent inhibition by phosphorus is influenced by other nutritional pathways in the interaction between Petunia hybrida and R. irregularis. We show that phosphorus and nitrogen are the major nutritional determinants of the interaction. Interestingly, the symbiosis-promoting effect of nitrogen starvation dominantly overruled the suppressive effect of high phosphorus nutrition onto arbuscular mycorrhiza, suggesting that plants promote the symbiosis as long as they are limited by one of the two major nutrients. Our results also show that in a given pair of symbiotic partners (Petunia hybrida and R. irregularis), the entire range from mutually symbiotic to parasitic can be observed depending on the nutritional conditions. Taken together, these results reveal complex nutritional feedback mechanisms in the control of root colonization by arbuscular mycorrhizal fungi.

  12. Arbuscular mycorrhizal fungi in terms of symbiosis-parasitism continuum.

    PubMed

    Schmidt, B; Gaşpar, S; Camen, D; Ciobanu, I; Sumălan, R

    2011-01-01

    Arbuscular mycorrhizal fungi are forming the most wide-spread mycorrhizal relationships on Earth. Mycorrhiza contributes to phosphorous acquisition, water absorption and resistance to diseases. The fungus promotes the absorption of nutrients and water from soil, meanwhile the host plant offers photosynthetic assimilates in exchange, like carbohydrates, as energy source. The plant benefits from the contribution of symbiotic partner only when nutrients are in low concentrations in soil and the root system would not be able to absorb sufficiently the minerals. When the help of mycorrhizal fungi is not necessarily needed, the host plant is making an economy of energy, suppressing the development of fungi in the internal radicular space. In this moment, the nature of relationship turns from symbiotic to parasitic, triggering a series of defensive reactions from the plant. Also, there were several cases reported when the presence of arbuscular mycorrhizal fungi negatively influenced the host plant. For example, in adverse environmental conditions, like very high temperatures, instead of determining a higher plant biomass and flowering, the mycorrhiza reduces the growth of the host plant. We conducted a pot experiment with hydroponic culture to examine the effect of arbuscular mycorrhiza on development of French marigold as a host plant. As experimental variants, the phosphorous content in nutrient medium and temperature varied. Plants were artificially infected with arbuscular mycorrhizal fungi using a commercial inoculum containing three fungal species, as following: Glomus intraradices, Glomus etunicatum and Glomus claroideum. Colonization intensity and arbuscular richness were checked using root staining with aniline blue and estimation with the Trouvelot method. To observe the differences between plants from the experimental variants, we examined the number of side shoots, flower buds and fully developed flowers, fresh biomass and total leaf area. Results show that

  13. Seasonality of arbuscular mycorrhizal symbiosis and dark septate endophytes in a grassland site in southwest China.

    PubMed

    Lingfei, Li; Anna, Yang; Zhiwei, Zhao

    2005-11-01

    Arbuscular mycorrhizal and dark septate endophytic fungal colonization in a grassland in Kunming, southwest China, was investigated monthly over one year. All plant roots surveyed were co-colonized by arbuscular mycorrhizal and dark septate endophytic fungi in this grassland. Both arbuscular mycorrhizal and dark septate endophytic fungal colonization fluctuated significantly throughout the year, and their seasonal patterns were different in each plant species. The relationships between environmental (climatic and edaphic) factors and fungal colonization were also studied. Correlation analysis demonstrated that arbuscular mycorrhizal colonization was significantly correlative with environmental factors (rainfall, sunlight hours, soil P, etc.), but dark septate endophytic fungal colonization was only correlative with relative humidity and sunlight hours.

  14. Plant hormones as signals in arbuscular mycorrhizal symbiosis.

    PubMed

    Miransari, Mohammad; Abrishamchi, A; Khoshbakht, K; Niknam, V

    2014-06-01

    Arbuscular mycorrhizal (AM) fungi are non-specific symbionts developing mutual and beneficial symbiosis with most terrestrial plants. Because of the obligatory nature of the symbiosis, the presence of the host plant during the onset and proceeding of symbiosis is necessary. However, AM fungal spores are able to germinate in the absence of the host plant. The fungi detect the presence of the host plant through some signal communications. Among the signal molecules, which can affect mycorrhizal symbiosis are plant hormones, which may positively or adversely affect the symbiosis. In this review article, some of the most recent findings regarding the signaling effects of plant hormones, on mycorrhizal fungal symbiosis are reviewed. This may be useful for the production of plants, which are more responsive to mycorrhizal symbiosis under stress.

  15. Arbuscular mycorrhizal fungi: effects on plant terpenoid accumulation.

    PubMed

    Welling, M T; Liu, L; Rose, T J; Waters, D L E; Benkendorff, K

    2016-07-01

    Arbuscular mycorrhizal fungi (AMF) are a diverse group of soil-dwelling fungi that form symbiotic associations with land plants. AMF-plant associations promote the accumulation of plant terpenoids beneficial to human health, although how AMF mediate terpenoid accumulation is not fully understood. A critical assessment and discussion of the literature relating to mechanisms by which AMF influence plant terpenoid accumulation, and whether this symbiosis can be harnessed in horticultural ecosystems was performed. Modification of plant morphology, phosphorus availability and gene transcription involved with terpenoid biosynthetic pathways were identified as key mechanisms associated with terpenoid accumulation in AMF-colonised plants. In order to exploit AMF-plant symbioses in horticultural ecosystems it is important to consider the specificity of the AMF-plant association, the predominant factor affecting terpenoid accumulation, as well as the end use application of the harvested plant material. Future research should focus on resolving the relationship between ecologically matched AMF genotypes and terpenoid accumulation in plants to establish if these associations are effective in promoting mechanisms favourable for plant terpenoid accumulation.

  16. Strigolactones stimulate arbuscular mycorrhizal fungi by activating mitochondria.

    PubMed

    Besserer, Arnaud; Puech-Pagès, Virginie; Kiefer, Patrick; Gomez-Roldan, Victoria; Jauneau, Alain; Roy, Sébastien; Portais, Jean-Charles; Roux, Christophe; Bécard, Guillaume; Séjalon-Delmas, Nathalie

    2006-07-01

    The association of arbuscular mycorrhizal (AM) fungi with plant roots is the oldest and ecologically most important symbiotic relationship between higher plants and microorganisms, yet the mechanism by which these fungi detect the presence of a plant host is poorly understood. Previous studies have shown that roots secrete a branching factor (BF) that strongly stimulates branching of hyphae during germination of the spores of AM fungi. In the BF of Lotus, a strigolactone was found to be the active molecule. Strigolactones are known as germination stimulants of the parasitic plants Striga and Orobanche. In this paper, we show that the BF of a monocotyledonous plant, Sorghum, also contains a strigolactone. Strigolactones strongly and rapidly stimulated cell proliferation of the AM fungus Gigaspora rosea at concentrations as low as 10(-13) M. This effect was not found with other sesquiterperne lactones known as germination stimulants of parasitic weeds. Within 1 h of treatment, the density of mitochondria in the fungal cells increased, and their shape and movement changed dramatically. Strigolactones stimulated spore germination of two other phylogenetically distant AM fungi, Glomus intraradices and Gl. claroideum. This was also associated with a rapid increase of mitochondrial density and respiration as shown with Gl. intraradices. We conclude that strigolactones are important rhizospheric plant signals involved in stimulating both the pre-symbiotic growth of AM fungi and the germination of parasitic plants.

  17. [Effects of the arbuscular mycorrhizal fungi on environmental phytoremediation in coal mine areas].

    PubMed

    Li, Shao-Peng; Bi, Yin-Li; Kong, Wei-Ping; Wang, Jin; Yu, Hai-Yang

    2013-11-01

    To resolve the key environmental problems in coal mine areas of environmental phytoremediation, symbiosis of arbuscular mycorrhizal fungi (AMF) and Amorpha fruticosa was investigated. Effects of AMF on the root growth of Amorpha fruticosa and degenerated soil in coal mining subsidence area were studied. Results showed that after 5 months inoculation, AMF improved the shoot and root growth of Amorpha fruticosa. After inoculation with arbuscular mycorrhiza (AM) for 5 months, the inoculation significantly increased root colonization of Amorpha fruticosa. Total glomalin and easily extractable glomalin were increased significantly in the incubated soil. The content of phosphorus and organic matter were increased in the rhizosphere soil. Population of microorganism increased obviously. All the above results show that their ecological effects are significantly improved. AM would promote rhizosphere soil that will help the sustainability of ecological systems in mining area. It is really of great significance to keep the ecological system stability.

  18. Arbuscular mycorrhizal fungal responses to abiotic stresses: A review.

    PubMed

    Lenoir, Ingrid; Fontaine, Joël; Lounès-Hadj Sahraoui, Anissa

    2016-03-01

    The majority of plants live in close collaboration with a diversity of soil organisms among which arbuscular mycorrhizal fungi (AMF) play an essential role. Mycorrhizal symbioses contribute to plant growth and plant protection against various environmental stresses. Whereas the resistance mechanisms induced in mycorrhizal plants after exposure to abiotic stresses, such as drought, salinity and pollution, are well documented, the knowledge about the stress tolerance mechanisms implemented by the AMF themselves is limited. This review provides an overview of the impacts of various abiotic stresses (pollution, salinity, drought, extreme temperatures, CO2, calcareous, acidity) on biodiversity, abundance and development of AMF and examines the morphological, biochemical and molecular mechanisms implemented by AMF to survive in the presence of these stresses.

  19. Breakdown and delayed cospeciation in the arbuscular mycorrhizal mutualism

    PubMed Central

    Merckx, Vincent; Bidartondo, Martin I

    2008-01-01

    The ancient arbuscular mycorrhizal association between the vast majority of plants and the fungal phylum Glomeromycota is a dominant nutritional mutualism worldwide. In the mycorrhizal mutualism, plants exchange photosynthesized carbohydrates for mineral nutrients acquired by fungi from the soil. This widespread cooperative arrangement is broken by ‘cheater’ plant species that lack the ability to photosynthesize and thus become dependent upon three-partite linkages (cheater–fungus–photosynthetic plant). Using the first fine-level coevolutionary analysis of mycorrhizas, we show that extreme fidelity towards fungi has led cheater plants to lengthy evolutionary codiversification. Remarkably, the plants' evolutionary history closely mirrors that of their considerably older mycorrhizal fungi. This demonstrates that one of the most diffuse mutualistic networks is vulnerable to the emergence, persistence and speciation of highly specific cheaters. PMID:18270159

  20. 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

  1. Studying Genome Heterogeneity within the Arbuscular Mycorrhizal Fungal Cytoplasm

    PubMed Central

    Halary, Sébastien; Bapteste, Eric; Hijri, Mohamed

    2015-01-01

    Although heterokaryons have been reported in nature, multicellular organisms are generally assumed genetically homogeneous. Here, we investigate the case of arbuscular mycorrhizal fungi (AMF) that form symbiosis with plant roots. The growth advantages they confer to their hosts are of great potential benefit to sustainable agricultural practices. However, measuring genetic diversity for these coenocytes is a major challenge: Within the same cytoplasm, AMF contain thousands of nuclei and show extremely high levels of genetic variation for some loci. The extent and physical location of polymorphism within and between AMF genomes is unclear. We used two complementary strategies to estimate genetic diversity in AMF, investigating polymorphism both on a genome scale and in putative single copy loci. First, we used data from whole-genome pyrosequencing of four AMF isolates to describe genetic diversity, based on a conservative network-based clustering approach. AMF isolates showed marked differences in genome-wide diversity patterns in comparison to a panel of control fungal genomes. This clustering approach further allowed us to provide conservative estimates of Rhizophagus spp. genomes sizes. Second, we designed new putative single copy genomic markers, which we investigated by massive parallel amplicon sequencing for two Rhizophagus irregularis and one Rhizophagus sp. isolates. Most loci showed high polymorphism, with up to 103 alleles per marker. This polymorphism could be distributed within or between nuclei. However, we argue that the Rhizophagus isolates under study might be heterokaryotic, at least for the putative single copy markers we studied. Considering that genetic information is the main resource for identification of AMF, we suggest that special attention is warranted for the study of these ecologically important organisms. PMID:25573960

  2. Do fungivores trigger the transfer of protective metabolites from host plants to arbuscular mycorrhizal hyphae?

    PubMed

    Duhamel, Marie; Pel, Roel; Ooms, Astra; Bücking, Heike; Jansa, Jan; Ellers, Jacintha; van Straalen, Nico M; Wouda, Tjalf; Vandenkoornhuyse, Philippe; Kiers, E Toby

    2013-09-01

    A key objective in ecology is to understand how cooperative strategies evolve and are maintained in species networks. Here, we focus on the tri-trophic relationship between arbuscular mycorrhizal (AM) fungi, host plants, and fungivores to ask if host plants are able to protect their mutualistic mycorrhizal partners from being grazed. Specifically, we test whether secondary metabolites are transferred from hosts to fungal partners to increase their defense against fungivores. We grew Plantago lanceolata hosts with and without mycorrhizal inoculum, and in the presence or absence of fungivorous springtails. We then measured fungivore effects on host biomass and mycorrhizal abundance (using quantitative PCR) in roots and soil. We used high-performance liquid chromatography to measure host metabolites in roots, shoots, and hyphae, focusing on catalpol, aucubin, and verbascoside. Our most striking result was that the metabolite catalpol was consistently found in AM fungal hyphae in host plants exposed to fungivores. When fungivores were absent, catalpol was undetectable in hyphae. Our results highlight the potential for plant-mediated protection of the mycorrhizal hyphal network.

  3. Effects of organic farming on communities of arbuscular mycorrhizal fungi.

    PubMed

    Lee, Si-Woo; Lee, Eun-Hwa; Eom, Ahn-Heum

    2008-03-01

    Red pepper (Capsicum annum L.) roots and soils representing different agricultural management practices such as conventional (CON), no-chemical (NOC), and organic farming systems (ORG) were collected from 32 farm field sites in Kyunggi, Korea to investigate the effects of these agricultural practices on arbuscular mycorrhizal (AM) symbiosis. ORG inoculum significantly increased plant growth compared to inoculum from CON and NOC. A community analysis of AM fungi (AMF) using morphological features of spores revealed that AMF spore abundance and species diversity were significantly higher in ORG than in CON. Additionally, a community analysis of AMF colonizing roots using a molecular technique revealed higher AMF diversity in ORG than in CON. These results suggest that agricultural practices significantly influence AM fungal community structure and mycorrhizal inoculum potential.

  4. Transgenerational effects of plant sex and arbuscular mycorrhizal symbiosis.

    PubMed

    Varga, Sandra; Vega-Frutis, Rocío; Kytöviita, Minna-Maarit

    2013-08-01

    In gynodioecious plants, females are predicted to produce more and/or better offspring than hermaphrodites in order to be maintained in the same population. In the field, the roots of both sexes are usually colonized by arbuscular mycorrhizal (AM) fungi. Transgenerational effects of mycorrhizal symbiosis are largely unknown, although theoretically expected. We examined the maternal and paternal effects of AM fungal symbiosis and host sex on seed production and posterior seedling performance in Geranium sylvaticum, a gynodioecious plant. We hand-pollinated cloned females and hermaphrodites in symbiosis with AM fungi or in nonmycorrhizal conditions and measured seed number and mass, and seedling survival and growth in a glasshouse experiment. Females produced more seeds than hermaphrodites, but the seeds did not germinate, survive or grow better. Mycorrhizal plants were larger, but did not produce more seeds than nonmycorrhizal plants. Transgenerational parental effects of AM fungi were verified in seedling performance. This is the first study to show transgenerational mycorrhiza-mediated parental effects in a gynodioecious species. Mycorrhizal symbiosis affects plant fitness mainly through female functions with enduring effects on the next generation.

  5. A meta-analysis of arbuscular mycorrhizal effects on plants grown under salt stress.

    PubMed

    Chandrasekaran, Murugesan; Boughattas, Sonia; Hu, Shuijin; Oh, Sang-Hyon; Sa, Tongmin

    2014-11-01

    Salt stress limits crop yield and sustainable agriculture in most arid and semiarid regions of the world. Arbuscular mycorrhizal fungi (AMF) are considered bio-ameliorators of soil salinity tolerance in plants. In evaluating AMF as significant predictors of mycorrhizal ecology, precise quantifiable changes in plant biomass and nutrient uptake under salt stress are crucial factors. Therefore, the objective of the present study was to analyze the magnitude of the effects of AMF inoculation on growth and nutrient uptake of plants under salt stress through meta-analyses. For this, data were compared in the context of mycorrhizal host plant species, plant family and functional group, herbaceous vs. woody plants, annual vs. perennial plants, and the level of salinity across 43 studies. Results indicate that, under saline conditions, AMF inoculation significantly increased total, shoot, and root biomass as well as phosphorous (P), nitrogen (N), and potassium (K) uptake. Activities of the antioxidant enzymes superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase also increased significantly in mycorrhizal compared to nonmycorrhizal plants growing under salt stress. In addition, sodium (Na) uptake decreased significantly in mycorrhizal plants, while changes in proline accumulation were not significant. Across most subsets of the data analysis, identities of AMF (Glomus fasciculatum) and host plants (Acacia nilotica, herbs, woody and perennial) were found to be essential in understanding plant responses to salinity stress. For the analyzed dataset, it is concluded that under salt stress, mycorrhizal plants have extensive root traits and mycorrhizal morphological traits which help the uptake of more P and K, together with the enhanced production of antioxidant enzymes resulting in salt stress alleviation and increased plant biomass.

  6. DELLA proteins regulate arbuscule formation in arbuscular mycorrhizal symbiosis.

    PubMed

    Floss, Daniela S; Levy, Julien G; Lévesque-Tremblay, Véronique; Pumplin, Nathan; Harrison, Maria J

    2013-12-17

    Most flowering plants are able to form endosymbioses with arbuscular mycorrhizal fungi. In this mutualistic association, the fungus colonizes the root cortex and establishes elaborately branched hyphae, called arbuscules, within the cortical cells. Arbuscule development requires the cellular reorganization of both symbionts, and the resulting symbiotic interface functions in nutrient exchange. A plant symbiosis signaling pathway controls the development of the symbiosis. Several components of the pathway have been identified, but transcriptional regulators that control downstream pathways for arbuscule formation are still unknown. Here we show that DELLA proteins, which are repressors of gibberellic acid (GA) signaling and function at the nexus of several signaling pathways, are required for arbuscule formation. Arbuscule formation is severely impaired in a Medicago truncatula Mtdella1/Mtdella2 double mutant; GA treatment of wild-type roots phenocopies the della double mutant, and a dominant DELLA protein (della1-Δ18) enables arbuscule formation in the presence of GA. Ectopic expression of della1-Δ18 suggests that DELLA activity in the vascular tissue and endodermis is sufficient to enable arbuscule formation in the inner cortical cells. In addition, expression of della1-Δ18 restores arbuscule formation in the symbiosis signaling pathway mutant cyclops/ipd3, indicating an intersection between DELLA and symbiosis signaling for arbuscule formation. GA signaling also influences arbuscule formation in monocots, and a Green Revolution wheat variety carrying dominant DELLA alleles shows enhanced colonization but a limited growth response to arbuscular mycorrhizal symbiosis.

  7. DELLA proteins regulate arbuscule formation in arbuscular mycorrhizal symbiosis

    PubMed Central

    Floss, Daniela S.; Levy, Julien G.; Lévesque-Tremblay, Véronique; Pumplin, Nathan; Harrison, Maria J.

    2013-01-01

    Most flowering plants are able to form endosymbioses with arbuscular mycorrhizal fungi. In this mutualistic association, the fungus colonizes the root cortex and establishes elaborately branched hyphae, called arbuscules, within the cortical cells. Arbuscule development requires the cellular reorganization of both symbionts, and the resulting symbiotic interface functions in nutrient exchange. A plant symbiosis signaling pathway controls the development of the symbiosis. Several components of the pathway have been identified, but transcriptional regulators that control downstream pathways for arbuscule formation are still unknown. Here we show that DELLA proteins, which are repressors of gibberellic acid (GA) signaling and function at the nexus of several signaling pathways, are required for arbuscule formation. Arbuscule formation is severely impaired in a Medicago truncatula Mtdella1/Mtdella2 double mutant; GA treatment of wild-type roots phenocopies the della double mutant, and a dominant DELLA protein (della1-Δ18) enables arbuscule formation in the presence of GA. Ectopic expression of della1-Δ18 suggests that DELLA activity in the vascular tissue and endodermis is sufficient to enable arbuscule formation in the inner cortical cells. In addition, expression of della1-Δ18 restores arbuscule formation in the symbiosis signaling pathway mutant cyclops/ipd3, indicating an intersection between DELLA and symbiosis signaling for arbuscule formation. GA signaling also influences arbuscule formation in monocots, and a Green Revolution wheat variety carrying dominant DELLA alleles shows enhanced colonization but a limited growth response to arbuscular mycorrhizal symbiosis. PMID:24297892

  8. Diversity of Arbuscular Mycorrhizal Fungi and Their Roles in Ecosystems

    PubMed Central

    Lee, Eun-Hwa; Eo, Ju-Kyeong; Ka, Kang-Hyeon

    2013-01-01

    Arbuscular mycorrhizal fungi (AMF) have mutualistic relationships with more than 80% of terrestrial plant species. This symbiotic relationship is ancient and would have had important roles in establishment of plants on land. Despite their abundance and wide range of relationship with plant species, AMF have shown low species diversity. However, molecular studies have suggested that diversity of these fungi may be much higher, and genetic variation of AMF is very high within a species and even within a single spore. Despite low diversity and lack of host specificity, various functions have been associated with plant growth responses to arbuscular mycorrhizal fungal colonization. In addition, different community composition of AMF affects plants differently, and plays a potential role in ecosystem variability and productivity. AMF have high functional diversity because different combinations of host plants and AMF have different effects on the various aspects of symbiosis. Consequently, recent studies have focused on the different functions of AMF according to their genetic resource and their roles in ecosystem functioning. This review summarizes taxonomic, genetic, and functional diversities of AMF and their roles in natural ecosystems. PMID:24198665

  9. Enrichment of arbuscular mycorrhizal fungi in a contaminated soil after rehabilitation.

    PubMed

    Lopes Leal, Patrícia; Varón-López, Maryeimy; Gonçalves de Oliveira Prado, Isabelle; Valentim Dos Santos, Jessé; Fonsêca Sousa Soares, Cláudio Roberto; Siqueira, José Oswaldo; de Souza Moreira, Fatima Maria

    Spore counts, species composition and richness of arbuscular mycorrhizal fungi, and soil glomalin contents were evaluated in a soil contaminated with Zn, Cu, Cd and Pb after rehabilitation by partial replacement of the contaminated soil with non-contaminated soil, and by Eucalyptus camaldulensis planting with and without Brachiaria decumbens sowing. These rehabilitation procedures were compared with soils from contaminated non-rehabilitated area and non-contaminated adjacent soils. Arbuscular mycorrhizal fungi communities attributes were assessed by direct field sampling, trap culture technique, and by glomalin contents estimate. Arbuscular mycorrhizal fungi was markedly favored by rehabilitation, and a total of 15 arbuscular mycorrhizal fungi morphotypes were detected in the studied area. Species from the Glomus and Acaulospora genera were the most common mycorrhizal fungi. Number of spores was increased by as much as 300-fold, and species richness almost doubled in areas rehabilitated by planting Eucalyptus in rows and sowing B. decumbens in inter-rows. Contents of heavy metals in the soil were negatively correlated with both species richness and glomalin contents. Introduction of B. decumbens together with Eucalyptus causes enrichment of arbuscular mycorrhizal fungi species and a more balanced community of arbuscular mycorrhizal fungi spores in contaminated soil.

  10. Arbuscular mycorrhizal fungal assemblages in biological crusts from a Neotropical savanna are not related to the dominant perennial Trachypogon.

    PubMed

    Hernández-Hernández, R M; Roldán, A; Caravaca, F; Rodriguez-Caballero, G; Torres, M P; Maestre, F T; Alguacil, M M

    2017-01-01

    Knowledge of the arbuscular mycorrhizal fungal assemblages in the Trachypogon savanna ecosystems is very important to a better understanding of the ecological processes mediated by this soil microbial group that affects multiple ecosystem functions. Considering the hypothesis that the biocrusts can be linked to vegetation through the arbuscular fungi mycelial network, the objectives proposed in this study were to determine (i) whether there are arbuscular mycorrhizal fungi (AMF) in the biocrusts (ii) whether arbuscular mycorrhizal fungal assemblages are linked to the Trachypogon patches, and (iii) whether the composition of the assemblages is related to soil properties affected by microbiological activity. The community structure of the AMF was investigated in three habitats: rhizospheric soil and roots of Trachypogon vestitus, biological soil crusts, and bare soil. The canonical correspondence analysis showed that two soil properties related to enzymatic activity (protease and β-glucosidase) significantly affected the community composition of the AMF. The biocrusts in the Venezuelan savanna are colonized by an AM fungal community linked to that of the bare soil and significantly different from that hosted by the roots of the surrounding T. vestitus, suggesting that assemblages of AMF in biocrusts might be related more closely to those of annual plant species appearing in favorable conditions.

  11. 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.

  12. Native arbuscular mycorrhizal fungi in the Yungas forests, Argentina.

    PubMed

    Becerra, Alejandra G; Cabello, Marta N; Bartoloni, Norberto J

    2011-01-01

    The arbuscular mycorrhizal fungal (AMF) communities from the Yungas forests of Argentina were studied. The AMF species present in the rhizosphere of some dominant native plants (one tree: Alnus acuminata; three herbaceous species: Duchesnea indica, Oxalis conorrhiza, Trifolium aff. repens; and one shrub: Sambucus peruviana) from two sites (Quebrada del Portugués and Narváez Range) of the Yungas forests were isolated, identified and quantified during the four seasons of the year. Twenty-two AMF morphotaxa were found. Spore density of some AMF species at each site varied among seasons. The genera that most contributed to the biodiversity index were Acaulospora for Quebrada del Portugués and Glomus for Narváez Range. High diversity values were observed in the Yungas forests, particularly in the spring (rainy season). We concluded AMF differed in species composition and seasonal sporulation dynamics in the Yungas forests.

  13. Presence of arbuscular mycorrhizal fungi in South Florida native plants.

    PubMed

    Fisher, Jack B; Jayachandran, K

    2005-11-01

    The roots of 27 species of South Florida plants in 15 families (including one cycad, six palms, one Smilax, and 19 dicotyledons) native to pine rockland and tropical hardwood hammock communities were examined for arbuscular mycorrhizal fungi (AMF). These plants grow in the biologically diverse but endangered Greater Everglades habitat. Roots from field-grown and potted plants were cleared and stained. All 27 species had AMF and include 14 species having an endangered or threatened status. The Paris-type colonization occurred in two species in the families Annonaceae and Smilacaceae. The Arum-type occurred in 22 species in the families Anacardiaceae, Arecaceae (Palmae), Boraginaceae, Cactaceae (questionable), Euphorbiaceae, Fabaceae, Lauraceae, Melastomataceae, Polygalaceae, Rubiaceae, Simaroubaceae, Ulmaceae, and Zamiaceae. Three species in the families Fabaceae, Lauraceae, and Simaroubaceae had a mix of Paris- and Arum-types. The results have implications for the restoration of these endangered plant communities in the Everglades.

  14. Strigolactones, signals for parasitic plants and arbuscular mycorrhizal fungi.

    PubMed

    García-Garrido, J M; Lendzemo, V; Castellanos-Morales, V; Steinkellner, S; Vierheilig, Horst

    2009-09-01

    Although strigolactones play a critical role as rhizospheric signaling molecules for the establishment of arbuscular mycorrhizal (AM) symbiosis and for seed germination of parasitic weeds, scarce data are available about interactions between AM fungi and strigolactones. In the present work, we present background data on strigolactones from studies on their seed germination activity on the parasitic weeds Orobanche and Striga, the importance of nitrogen and phosphorus for this seed germination activity, and what this could mean for AM fungi. We also present results on the susceptibility of plants to AM fungi and the possible involvement of strigolactones in this AM susceptibility and discuss the role of strigolactones for the formation and the regulation of the AM symbiosis as well as the possible implication of these compounds as plant signals in other soil-borne plant-microbe interactions.

  15. Arbuscular mycorrhizal fungus responses to disturbance are context-dependent.

    PubMed

    van der Heyde, Mieke; Ohsowski, Brian; Abbott, Lynette K; Hart, Miranda

    2017-01-24

    Anthropogenic disturbance is one of the most important forces shaping soil ecosystems. While organisms that live in the soil, such as arbuscular mycorrhizal (AM) fungi, are sensitive to disturbance, their response is not always predictable. Given the range of disturbance types and differences among AM fungi in their growth strategies, the unpredictability of the responses of AM fungi to disturbance is not surprising. We investigated the role of disturbance type (i.e., soil disruption, agriculture, host perturbation, and chemical disturbance) and fungus identity on disturbance response in the AM symbiosis. Using meta-analysis, we found evidence for differential disturbance response among AM fungal species, as well as evidence that particular fungal species are especially susceptible to certain disturbance types, perhaps because of their life history strategies.

  16. Arbuscular mycorrhizal symbiosis decreases strigolactone production in tomato.

    PubMed

    López-Ráez, Juan A; Charnikhova, Tatsiana; Fernández, Ivan; Bouwmeester, Harro; Pozo, Maria J

    2011-02-15

    Strigolactones are a new class of plant hormones emerging as important signals in the control of plant architecture. In addition, they are key elements in plant communication with several rhizosphere organisms. Strigolactones are exuded into the soil, where they act as host detection signals for arbuscular mycorrhizal (AM) fungi, but also as germination stimulants for root parasitic plant seeds. Under phosphate limiting conditions, plants up-regulate the secretion of strigolactones into the rhizosphere to promote the formation of AM symbiosis. Using tomato as a model plant, we have recently shown that AM symbiosis induces changes in transcriptional and hormonal profiles. Using the same model system, here we analytically demonstrate, using liquid chromatography-tandem mass spectrometry, that strigolactone production is also significantly reduced upon AM symbiosis. Considering the dual role of the strigolactones in the rhizosphere as signals for AM fungi and parasitic plants, we discuss the potential implications of these changes in the plant interaction with both organisms.

  17. Contribution of the arbuscular mycorrhizal symbiosis to heavy metal phytoremediation.

    PubMed

    Göhre, Vera; Paszkowski, Uta

    2006-05-01

    High concentrations of heavy metals (HM) in the soil have detrimental effects on ecosystems and are a risk to human health as they can enter the food chain via agricultural products or contaminated drinking water. Phytoremediation, a sustainable and inexpensive technology based on the removal of pollutants from the environment by plants, is becoming an increasingly important objective in plant research. However, as phytoremediation is a slow process, improvement of efficiency and thus increased stabilization or removal of HMs from soils is an important goal. Arbuscular mycorrhizal (AM) fungi provide an attractive system to advance plant-based environmental clean-up. During symbiotic interaction the hyphal network functionally extends the root system of their hosts. Thus, plants in symbiosis with AM fungi have the potential to take up HM from an enlarged soil volume. In this review, we summarize current knowledge about the contribution of the AM symbiosis to phytoremediation of heavy metals.

  18. Arbuscular mycorrhizal dynamics in a chronosequence of Caragana korshinskii plantations.

    PubMed

    Liu, Yongjun; He, Lei; An, Lizhe; Helgason, Thorunn; Feng, Huyuan

    2009-01-01

    Arbuscular mycorrhizal (AM) fungi in a chronosequence of 5-42-year-old Caragana korshinskii plantations in the semi-arid Loess Plateau region of northwestern China were investigated. AM fungi colonization, spore diversity and PCR-denatured gradient gel electrophoresis-based AM fungal SSU rRNA gene sequences were analyzed. AM fungi colonization [measured as the percent of root length (%RLC), vesicular (%VC) and arbuscular (%AC) colonization] and spore density were significantly correlated with sampling month, but not with plant age, except for %RLC. The percent of vesicular colonization was negatively correlated with soil total nitrogen and organic carbon, and spore density was negatively correlated with soil moisture and available phosphorus. Ten distinguishable AM fungal spore morphotypes, nine Glomus and one Scutellospora species, were found. Nine AM fungal Glomus phylotypes were identified by sequencing, but at each sampling time only four to six AM fungal phylotypes were detected. The AM fungal community was significantly seasonal, whereas the AM fungal species richness did not increase with plantation age. A significant change in AM fungal colonization and community composition over an annual cycle was observed in this study, and our results suggest that the changes of AM are the product of the interaction between host phenology, soil characteristics and habitat. Understanding these interactions is essential if habitat restoration is to be effective.

  19. Arbuscular mycorrhizal fungi make a complex contribution to soil aggregation

    NASA Astrophysics Data System (ADS)

    McGee, Peter; Daynes, Cathal; Damien, Field

    2013-04-01

    Soil aggregates contain solid and fluid components. Aggregates develop as a consequence of the organic materials, plants and hyphae of arbuscular mycorrhizal (AM) fungi acting on the solid phase. Various correlative studies indicate hyphae of AM fungi enmesh soil particles, but their impact on the pore space is poorly understood. Hyphae may penetrate between particles, remove water from interstitial spaces, and otherwise re-arrange the solid phase. Thus we might predict that AM fungi also change the pore architecture of aggregates. Direct observations of pore architecture of soil, such as by computer-aided tomography (CT), is difficult. The refractive natures of solid and biological material are similar. The plant-available water in various treatments allows us to infer changes in pore architecture. Our experimental studies indicate AM fungi have a complex role in the formation and development of aggregates. Soils formed from compost and coarse subsoil materials were planted with mycorrhizal or non-mycorrhizal seedlings and the resultant soils compared after 6 or 14 months in separate experiments. As well as enmeshing particles, AM fungi were associated with the development of a complex pore space and greater pore volume. Even though AM fungi add organic matter to soil, the modification of pore space is not correlated with organic carbon. In a separate study, we visualised hyphae of AM fungi in a coarse material using CT. In this study, hyphae appeared to grow close to the surfaces of particles with limited ramification across the pore spaces. Hyphae of AM fungi appear to utilise soil moisture for their growth and development of mycelium. The strong correlation between moisture and hyphae has profound implications for soil aggregation, plant utilisation of soil water, and the distribution of water as water availability declines.

  20. DNA-Based Characterization and Identification of Arbuscular Mycorrhizal Fungi Species.

    PubMed

    Senés-Guerrero, Carolina; Schüßler, Arthur

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of most land plants. They have great ecological and economic importance as they can improve plant nutrition, plant water supply, soil structure, and plant resistance to pathogens. We describe two approaches for the DNA-based characterization and identification of AMF, which both can be used for single fungal spores, soil, or roots samples and resolve closely related AMF species: (a) Sanger sequencing of a 1.5 kb extended rDNA-barcode from clone libraries, e.g., to characterize AMF isolates, and (b) high throughput 454 GS-FLX+ pyrosequencing of a 0.8 kb rDNA fragment, e.g., for in-field monitoring.

  1. Enhancement of clover growth by inoculation of P-solubilizing fungi and arbuscular mycorrhizal fungi.

    PubMed

    Souchie, Edson L; Azcón, Rosario; Barea, Jose M; Silva, Eliane M R; Saggin-Júnior, Orivaldo J

    2010-09-01

    This study evaluated the synergism between several P-solubilizing fungi isolates and arbuscular mycorrhizal fungi to improve clover ( Trifolium pratense) growth in the presence of Araxá apatite. Clover was sown directly in plastic pots with 300g of sterilized washed sand, vermiculite and sepiolite 1:1:1 (v:v:v) as substrate, and grown in a controlled environment chamber. The substrate was fertilized with 3 g L(-1) of Araxá apatite. A completely randomized design, in 8×2 factorial scheme (eight P-solubilizing fungi treatments with or without arbuscular mycorrhizal fungi)and four replicates were used. The P-solubilizing fungi treatments consisted of five Brazilian P-solubilizing fungi isolates (PSF 7, 9, 20, 21 and 22), two Spanish isolates ( Aspergillus niger and the yeast Yarowia lipolytica) and control (non-inoculated treatment). The greatest clover growth rate was recorded when Aspergillus niger and PSF 21 were co-inoculated with arbuscular mycorrhizal fungi. Aspergillus niger, PSF 7 and PSF 21 were the most effective isolates on increasing clover growth in the presence of arbuscular mycorrhizal fungi. Greater mycorrhizal colonization resulted in greater clover growth rate in most PSF treatments. PSF 7 was the best isolate to improve the establishment of mycorrhizal and rhizobia symbiosis.

  2. Shoot- and root-borne cytokinin influences arbuscular mycorrhizal symbiosis.

    PubMed

    Cosme, Marco; Ramireddy, Eswarayya; Franken, Philipp; Schmülling, Thomas; Wurst, Susanne

    2016-10-01

    The arbuscular mycorrhizal (AM) symbiosis is functionally important for the nutrition and growth of most terrestrial plants. Nearly all phytohormones are employed by plants to regulate the symbiosis with AM fungi, but the regulatory role of cytokinin (CK) is not well understood. Here, we used transgenic tobacco (Nicotiana tabacum) with a root-specific or constitutive expression of CK-degrading CKX genes and the corresponding wild-type to investigate whether a lowered content of CK in roots or in both roots and shoots influences the interaction with the AM fungus Rhizophagus irregularis. Our data indicates that shoot CK has a positive impact on AM fungal development in roots and on the root transcript level of an AM-responsive phosphate transporter gene (NtPT4). A reduced CK content in roots caused shoot and root growth depression following AM colonization, while neither the uptake of phosphorus or nitrogen nor the root transcript levels of NtPT4 were significantly affected. This suggests that root CK may restrict the C availability from the roots to the fungus thus averting parasitism by AM fungi. Taken together, our study indicates that shoot- and root-borne CK have distinct roles in AM symbiosis. We propose a model illustrating how plants may employ CK to regulate nutrient exchange with the ubiquitous AM fungi.

  3. Signaling events during initiation of arbuscular mycorrhizal symbiosis.

    PubMed

    Schmitz, Alexa M; Harrison, Maria J

    2014-03-01

    Under nutrient-limiting conditions, plants will enter into symbiosis with arbuscular mycorrhizal (AM) fungi for the enhancement of mineral nutrient acquisition from the surrounding soil. AM fungi live in close, intracellular association with plant roots where they transfer phosphate and nitrogen to the plant in exchange for carbon. They are obligate fungi, relying on their host as their only carbon source. Much has been discovered in the last decade concerning the signaling events during initiation of the AM symbiosis, including the identification of signaling molecules generated by both partners. This signaling occurs through symbiosis-specific gene products in the host plant, which are indispensable for normal AM development. At the same time, plants have adapted complex mechanisms for avoiding infection by pathogenic fungi, including an innate immune response to general microbial molecules, such as chitin present in fungal cell walls. How it is that AM fungal colonization is maintained without eliciting a defensive response from the host is still uncertain. In this review, we present a summary of the molecular signals and their elicited responses during initiation of the AM symbiosis, including plant immune responses and their suppression.

  4. NIN Is Involved in the Regulation of Arbuscular Mycorrhizal Symbiosis.

    PubMed

    Guillotin, Bruno; Couzigou, Jean-Malo; Combier, Jean-Philippe

    2016-01-01

    Arbuscular mycorrhizal (AM) symbiosis is an intimate and ancient symbiosis found between most of terrestrial plants and fungi from the Glomeromycota family. Later during evolution, the establishment of the nodulation between legume plants and soil bacteria known as rhizobia, involved several genes of the signaling pathway previously implicated for AM symbiosis. For the past years, the identification of the genes belonging to this Common Symbiotic Signaling Pathway have been mostly done on nodulation. Among the different genes already well identified as required for nodulation, we focused our attention on the involvement of Nodule Inception (NIN) in AM symbiosis. We show here that NIN expression is induced during AM symbiosis, and that the Medicago truncatula nin mutant is less colonized than the wild-type M. truncatula strain. Moreover, nin mutant displays a defect in the ability to be infected by the fungus Rhizophagus irregularis. This work brings a new evidence of the common genes involved in overlapping signaling pathways of both nodulation and in AM symbiosis.

  5. NIN Is Involved in the Regulation of Arbuscular Mycorrhizal Symbiosis

    PubMed Central

    Guillotin, Bruno; Couzigou, Jean-Malo; Combier, Jean-Philippe

    2016-01-01

    Arbuscular mycorrhizal (AM) symbiosis is an intimate and ancient symbiosis found between most of terrestrial plants and fungi from the Glomeromycota family. Later during evolution, the establishment of the nodulation between legume plants and soil bacteria known as rhizobia, involved several genes of the signaling pathway previously implicated for AM symbiosis. For the past years, the identification of the genes belonging to this Common Symbiotic Signaling Pathway have been mostly done on nodulation. Among the different genes already well identified as required for nodulation, we focused our attention on the involvement of Nodule Inception (NIN) in AM symbiosis. We show here that NIN expression is induced during AM symbiosis, and that the Medicago truncatula nin mutant is less colonized than the wild-type M. truncatula strain. Moreover, nin mutant displays a defect in the ability to be infected by the fungus Rhizophagus irregularis. This work brings a new evidence of the common genes involved in overlapping signaling pathways of both nodulation and in AM symbiosis. PMID:27899928

  6. Arbuscular Mycorrhizal Fungal Associations in Biofuel Cropping Systems

    NASA Astrophysics Data System (ADS)

    Murray, K.

    2012-12-01

    Arbuscular mycorrhizal fungi (AMF) are soil microorganisms that play an important role in delivering nutrients to plant roots via mutualistic symbiotic relationships. AMF root colonization was compared between four different biofuel cropping systems in an effort to learn more about the factors that control colonization. The four biofuel systems sampled were corn, switchgrass, prairie, and fertilized prairie. We hypothesized that prairie systems would have the highest levels of AMF colonization and that fertilization would result in lower AMF colonization rates. Roots were sampled from each system in early June and mid-July. Soil P and pH were also measured. In contrast to our hypothesis, corn systems had 70-80% colonization and the unfertilized prairie system had ~35% (P=0.001) in June. In July, all systems saw an increase in colonization rate, but corn roots still had significantly more AMF colonization than unfertilized prairie (P=0.001). AMF colonization in the unfertilized prairie system increased ~55% from June to July. In contrast to previous work, AMF colonization rates were highest in systems with the greatest availability on P and N (corn systems). These results indicate that seasonal differences in root growth were more influential to AMF root colonization than soil nutrient availability.

  7. Co-existing grass species have distinctive arbuscular mycorrhizal communities.

    PubMed

    Vandenkoornhuyse, P; Ridgway, K P; Watson, I J; Fitter, A H; Young, J P W

    2003-11-01

    Arbuscular mycorrhizal (AM) fungi are biotrophic symbionts colonizing the majority of land plants, and are of major importance in plant nutrient supply. Their diversity is suggested to be an important determinant of plant community structure, but the influence of host-plant and environmental factors on AM fungal community in plant roots is poorly documented. Using the terminal restriction fragment length polymorphism (T-RFLP) strategy, the diversity of AM fungi was assessed in 89 roots of three grass species (Agrostis capillaris, Festuca rubra, Poa pratensis) that co-occurred in the same plots of a field experiment. The impact of different soil amendments (nitrogen, lime, nitrogen and lime) and insecticide application on AM fungal community was also studied. The level of diversity found in AM fungal communities using the T-RFLP strategy was consistent with previous studies based on clone libraries. Our results clearly confirm that an AM fungal host-plant preference exists, even between different grass species. AM communities colonizing A. capillaris were statistically different from the others (P < 0.05). Although grass species evenness changed in amended soils, AM fungal community composition in roots of a given grass species remained stable. Conversely, in plots where insecticide was applied, we found higher AM fungal diversity and, in F. rubra roots, a statistically different AM fungal community.

  8. Dispersal of arbuscular mycorrhizal fungi and plants during succession

    NASA Astrophysics Data System (ADS)

    García de León, David; Moora, Mari; Öpik, Maarja; Jairus, Teele; Neuenkamp, Lena; Vasar, Martti; Bueno, C. Guillermo; Gerz, Maret; Davison, John; Zobel, Martin

    2016-11-01

    Arbuscular mycorrhizal (AM) fungi are important root symbionts that enhance plant nutrient uptake and tolerance to pathogens and drought. While the role of plant dispersal in shaping successional vegetation is well studied, there is very little information about the dispersal abilities of AM fungi. We conducted a trap-box experiment in a recently abandoned quarry at 10 different distances from the quarry edge (i.e. the potential propagule source) over eleven months to assess the short term, within-year, arrival of plant and AM fungal assemblages and hence their dispersal abilities. Using DNA based techniques we identified AM fungal taxa and analyzed their phylogenetic diversity. Plant diversity was determined by transporting trap soil to a greenhouse and identifying emerging seedlings. We recorded 30 AM fungal taxa. These contained a high proportion of ruderal AM fungi (30% of taxa, 79% of sequences) but the richness and abundance of AM fungi were not related to the distance from the presumed propagule source. The number of sequences of AM fungi decreased over time. Twenty seven plant species (30% of them ruderal) were recorded from the soil seed traps. Plant diversity decreased with distance from the propagule source and increased over time. Our data show that AM fungi with ruderal traits can be fast colonizers of early successional habitats.

  9. Arbuscular mycorrhizal fungal propagules in a salt marsh.

    PubMed

    Carvalho, Luís M; Correia, Patrícia M; Martins-Loução, M Amélia

    2004-07-01

    The tolerance of indigenous arbuscular mycorrhizal fungi (AMF) to stressful soil conditions and the relative contribution of spores of these fungi to plant colonization were examined in a Portuguese salt marsh. Glomus geosporum is dominant in this salt marsh. Using tetrazolium as a vital stain, a high proportion of field-collected spores were found to be metabolically active at all sampling dates. Spore germination tests showed that salt marsh spores were not affected by increasing levels of salinity, in contrast to two non-marsh spore isolates, and had a significantly higher ability to germinate under increased levels of salinity (20 per thousand) than in the absence of or at low salinity (10 per thousand). Germination of salt marsh spores was not affected by soil water levels above field capacity, in contrast to one of the two non-marsh spore isolates. For the evaluation of infectivity, a bioassay was established with undisturbed soil cores (containing all types of AM fungal propagules) and soil cores containing only spores as AM fungal propagules. Different types of propagules were able to initiate and to expand the root colonization of a native plant species, but spores were slower than mycelium and/or root fragments in colonizing host roots. The AM fungal adaptation shown by this study may explain the maintenance of AMF in salt marshes.

  10. Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi.

    PubMed

    Akiyama, Kohki; Matsuzaki, Ken-ichi; Hayashi, Hideo

    2005-06-09

    Arbuscular mycorrhizal (AM) fungi form mutualistic, symbiotic associations with the roots of more than 80% of land plants. The fungi are incapable of completing their life cycle in the absence of a host root. Their spores can germinate and grow in the absence of a host, but their hyphal growth is very limited. Little is known about the molecular mechanisms that govern signalling and recognition between AM fungi and their host plants. In one of the first stages of host recognition, the hyphae of AM fungi show extensive branching in the vicinity of host roots before formation of the appressorium, the structure used to penetrate the plant root. Host roots are known to release signalling molecules that trigger hyphal branching, but these branching factors have not been isolated. Here we have isolated a branching factor from the root exudates of Lotus japonicus and used spectroscopic analysis and chemical synthesis to identify it as a strigolactone, 5-deoxy-strigol. Strigolactones are a group of sesquiterpene lactones, previously isolated as seed-germination stimulants for the parasitic weeds Striga and Orobanche. The natural strigolactones 5-deoxy-strigol, sorgolactone and strigol, and a synthetic analogue, GR24, induced extensive hyphal branching in germinating spores of the AM fungus Gigaspora margarita at very low concentrations.

  11. Trichoderma harzianum might impact phosphorus transport by arbuscular mycorrhizal fungi.

    PubMed

    De Jaeger, Nathalie; de la Providencia, Ivan E; de Boulois, Hervé Dupré; Declerck, Stéphane

    2011-09-01

    Trichoderma sp. is a biocontrol agent active against plant pathogens via mechanisms such as mycoparasitism. Recently, it was demonstrated that Trichoderma harzianum was able to parasitize the mycelium of an arbuscular mycorrhizal (AM) fungus, thus affecting its viability. Here, we question whether this mycoparasitism may reduce the capacity of Glomus sp. to transport phosphorus ((33)P) to its host plant in an in vitro culture system. (33)P was measured in the plant and in the fungal mycelium in the presence/absence of T. harzianum. The viability and metabolic activity of the extraradical mycelium was measured via succinate dehydrogenase and alkaline phosphatase staining. Our study demonstrated an increased uptake of (33)P by the AM fungus in the presence of T. harzianum, possibly related to a stress reaction caused by mycoparasitism. In addition, the disruption of AM extraradical hyphae in the presence of T. harzianum affected the (33)P translocation within the AM fungal mycelium and consequently the transfer of (33)P to the host plant. The effects of T. harzianum on Glomus sp. may thus impact the growth and function of AM fungi and also indirectly plant performance by influencing the source-sink relationship between the two partners of the symbiosis.

  12. Toxic effects of chlorate on three plant species inoculated with arbuscular mycorrhizal fungi.

    PubMed

    Li, Huashou; Zhang, Xiuyu; Lin, Chuxia; Wu, Qitang

    2008-11-01

    Pot experiments were conducted to examine the toxic effects of chlorate on bermudagrass, bahiagrass, and longan seedling with a focus on arbuscular mycorrhizal fungi-plant associations. The results show that application of chlorate could cause slight soil acidification, but the resulting pH was still around 5.5, which is unlikely to adversely affect plant growth. Increase in the application rate of chlorate resulted in a decrease in colonization rate of arbuscular mycorrhizal fungi in plant roots, P uptake by the plants and plant biomass. This appears to suggest that the reduction in plant growth may be related to impeded uptake of P by the plants due to the failure of the plants to form sufficient mycorrhizal associations when chlorate is in sufficient amounts to cause toxicity to arbuscular mycorrhizal fungi. Under the experimental conditions set for this study, bermudagrass suffered from stronger chlorate stress than bahiagrass and longan seedling did in terms of plant-arbuscular mycorrhizal fungi (AMF) symbiosis development.

  13. Suppression of fungal and nematode plant pathogens through arbuscular mycorrhizal fungi.

    PubMed

    Veresoglou, Stavros D; Rillig, Matthias C

    2012-04-23

    Arbuscular mycorrhizal (AM) fungi represent ubiquitous mutualists of terrestrial plants. Through the symbiosis, plant hosts, among other benefits, receive protection from pathogens. A meta-analysis was conducted on 106 articles to determine whether, following pathogen infection of AM-colonized plants, the identity of the organisms involved (pathogens, AM fungi and host plants) had implications for the extent of the AM-induced pathogen suppression. Data on fungal and nematode pathogens were analysed separately. Although we found no differences in AM effectiveness with respect to the identity of the plant pathogen, the identity of the AM isolate had a dramatic effect on the level of pathogen protection. AM efficiency differences with respect to nematode pathogens were mainly limited to the number of AM isolates present; by contrast, modification of the ability to suppress fungal pathogens could occur even through changing the identity of the Glomeraceae isolate applied. N-fixing plants received more protection from fungal pathogens than non-N-fixing dicotyledons; this was attributed to the more intense AM colonization in N-fixing plants. Results have implications for understanding mycorrhizal ecology and agronomic applications.

  14. Symbiont dynamics during ecosystem succession: co-occurring plant and arbuscular mycorrhizal fungal communities.

    PubMed

    García de León, David; Moora, Mari; Öpik, Maarja; Neuenkamp, Lena; Gerz, Maret; Jairus, Teele; Vasar, Martti; Bueno, C Guillermo; Davison, John; Zobel, Martin

    2016-07-01

    Although mycorrhizas are expected to play a key role in community assembly during ecological succession, little is known about the dynamics of the symbiotic partners in natural systems. For instance, it is unclear how efficiently plants and arbuscular mycorrhizal (AM) fungi disperse into early successional ecosystems, and which, if either, symbiotic partner drives successional dynamics. This study describes the dynamics of plant and AM fungal communities, assesses correlation in the composition of plant and AM fungal communities and compares dispersal limitation of plants and AM fungi during succession. We studied gravel pits 20 and 50 years post abandonment and undisturbed grasslands in Western Estonia. The composition of plant and AM fungal communities was strongly correlated, and the strength of the correlation remained unchanged as succession progressed, indicating a stable dependence among mycorrhizal plants and AM fungi. A relatively high proportion of the AM fungal taxon pool was present in early successional sites, in comparison with the respective fraction of plants. These results suggest that AM fungi arrived faster than plants and may thus drive vegetation dynamics along secondary vegetation succession.

  15. The potential role of arbuscular mycorrhizal fungi in protecting endangered plants and habitats.

    PubMed

    Bothe, Hermann; Turnau, Katarzyna; Regvar, Marjana

    2010-10-01

    Ecosystems worldwide are threatened with the extinction of plants and, at the same time, invasion by new species. Plant invasiveness and loss of species can be caused by similar but opposing pressures on the community structures. Arbuscular mycorrhizal fungi (AMF) can have multiple positive effects on plant growth, productivity, health, and stress relief. Many endangered species live in symbiosis with AMF. However, the list of the International Union for Conservation of Nature and Natural Resources (IUCN Red List of Threatened Species) indicates that the mycorrhizal status of most of the threatened species has not been assessed. Rare plants often occur in specialized and also endangered habitats and might utilize specialized or unique AMF. The specificity of any endangered plant to its AMF population has not been investigated. Because most of the current AMF isolates that are available colonize a broad range of plant species, selected inocula could be used to promote growth of endangered plants before the proper and more effective indigenous AMF are characterized. Application of AMF in field sites to protect endangered plants is hardly feasible due to the complexity of plant community structures and the large amount of fungal inocula needed. Endangered plants could, however, be grown as greenhouse cultures together with appropriate fungi, and, at the relevant developmental stage, they could be re-planted into native sites to prevent extinction and to preserve plant community ecology.

  16. Analogous effects of arbuscular mycorrhizal fungi in the laboratory and a North Carolina field.

    PubMed

    Pringle, Anne; Bever, James D

    2008-01-01

    Although arbuscular mycorrhizal (AM) fungi are ubiquitous symbionts of plants, the mutualism has rarely been tested in nature. In experiments designed to explore the ecological relevance of associations between different fungal and plant species in a natural environment, plant species were infected with different species of fungi and grown in separate trials in the laboratory and a North Carolina (USA) field. The benefits to plants varied dramatically as plant species were grown with different species of AM fungi. Effects of mycorrhizal fungi in nature were generally correlated to effects in the growth chamber, suggesting that laboratory data do reflect dynamics between plants and AM fungi in the field. Initial size at transplant and experimental block were also significant predictors of plant growth in the field. Correlation statistics between laboratory and field data were weaker when analyses involved plant species less responsive to infection by any AM fungus, suggesting that the response of a species to inoculation is a good predictor of its sensitivity to specific AM fungi in the field. AM fungal identity appears to influence the growth and reproduction of plants in the field.

  17. Diversity Effects on Productivity Are Stronger within than between Trophic Groups in the Arbuscular Mycorrhizal Symbiosis

    PubMed Central

    Koch, Alexander M.; Antunes, Pedro M.; Klironomos, John N.

    2012-01-01

    Background The diversity of plants and arbuscular mycorrhizal fungi (AMF) has been experimentally shown to alter plant and AMF productivity. However, little is known about how plant and AMF diversity interact to shape their respective productivity. Methodology/Principal Findings We co-manipulated the diversity of both AMF and plant communities in two greenhouse studies to determine whether the productivity of each trophic group is mainly influenced by plant or AMF diversity, respectively, and whether there is any interaction between plant and fungal diversity. In both experiments we compared the productivity of three different plant species monocultures, or their respective 3-species mixtures. Similarly, in both studies these plant treatments were crossed with an AMF diversity gradient that ranged from zero (non-mycorrhizal controls) to a maximum of three and five taxonomically distinct AMF taxa, respectively. We found that within both trophic groups productivity was significantly influenced by taxon identity, and increased with taxon richness. These main effects of AMF and plant diversity on their respective productivities did not depend on each other, even though we detected significant individual taxon effects across trophic groups. Conclusions/Significance Our results indicate that similar ecological processes regulate diversity-productivity relationships within trophic groups. However, productivity-diversity relationships are not necessarily correlated across interacting trophic levels, leading to asymmetries and possible biotic feedbacks. Thus, biotic interactions within and across trophic groups should be considered in predictive models of community assembly. PMID:22629347

  18. Arbuscular mycorrhizal fungi from New Caledonian ultramafic soils improve tolerance to nickel of endemic plant species.

    PubMed

    Amir, Hamid; Lagrange, Alexandre; Hassaïne, Nadine; Cavaloc, Yvon

    2013-10-01

    In order to improve knowledge about the role of arbuscular mycorrhizal fungi (AMF) in the tolerance to heavy metals in ultramafic soils, the present study investigated the influence of two Glomus etunicatum isolates from New Caledonian ultramafic maquis (shrubland), on nickel tolerance of a model plant species Sorghum vulgare, and of two ultramafic endemic plant species, Alphitonia neocaledonica and Cloezia artensis. In a first step, plants were grown in a greenhouse, on sand with defined concentrations of Ni, to appreciate the effects of the two isolates on the alleviation of Ni toxicity in controlled conditions. In a second step, the influence of the AMF on A. neocaledonica and C. artensis plants grown in a New Caledonian ultramafic soil rich in extractable nickel was investigated. Ni reduced mycorrhizal colonization and sporulation of the fungal isolates, but the symbionts increased plant growth and adaptation of endemic plant species to ultramafic conditions. One of the two G. etunicatum isolates showed a stronger positive effect on plant biomass and phosphorus uptake, and a greater reduction in toxicity symptoms and Ni concentration in roots and shoots. The symbionts seemed to act as a barrier to the absorption of Ni by the plant and reduced root-to-shoot Ni translocation. Results indicate the potential of selected native AMF isolates from ultramafic areas for ecological restoration of such degraded ecosystems.

  19. Morphotype-based characterization of arbuscular mycorrhizal fungal communities in a restored tropical dry forest, Margarita island-Venezuela.

    PubMed

    Fajardo, Laurie; Loveral, Milagros; Arrindell, Pauline; Aguilar, Victor Hugo; Hasmy, Zamira; Cuenca, Gisela

    2015-09-01

    The mycorrhizal component of revegetated areas after ecological restoration or rehabilitation in arid and semiarid tropical areas has been scarcely assessed, particularly those made after mining disturbance. We evaluated and compared the presence of arbuscular mycorrhizal fungi of a small area of restored tropical dry forest destroyed by sand extraction, with a non-restored area of similar age, at the peninsula of Macanao, Margarita Island (Venezuela). Our study was undertaken in 2009, four years after planting, and the mycorrhizal status was evaluated in four restored plots (8 x 12.5 m) (two were previously treated with hydrogel (R2 and R2'), and two were left untreated (R1 and R1'), and four non-restored plots of similar size (NR1 and NR1' with graminoid physiognomy with some scattered shrubs; and NR2 and NR2', with a more species rich plant community). Apparently the restoration management promoted higher arbuscular mycorrhizal fungi (AMF) species richness and diversity, particularly in restored soils where the hydrogel was added (R2 treatment). Soil of the NRI treatment (with a higher herbaceous component) showed the highest spore density, compared to samples of soils under the other treatments. Considering species composition, Claroideoglomus etunicatum and Rhizophagus intraradices were found in all treatments; besides, Diversispora spurca and Funnefformis geosporum were only found in non-restored plots, while members of the Gigasporaceae (a family associated with little disturbed sites) were commonly observed in the plots with restored soils. Mycorrhizal colonization was similar in the restored and non-restored areas, being a less sensitive indicator of the ecosystem recovery. The trend of higher richness and diversity of AMF in the restored plot with hydrogel suggests that this management strategy contributes to accelerate the natural regeneration in those ecosystems where water plays an essential role.

  20. Casuarina in Africa: distribution, role and importance of arbuscular mycorrhizal, ectomycorrhizal fungi and Frankia on plant development.

    PubMed

    Diagne, Nathalie; Diouf, Diegane; Svistoonoff, Sergio; Kane, Aboubacry; Noba, Kandioura; Franche, Claudine; Bogusz, Didier; Duponnois, Robin

    2013-10-15

    Exotic trees were introduced in Africa to rehabilitate degraded ecosystems. Introduced species included several Australian species belonging to the Casuarinaceae family. Casuarinas trees grow very fast and are resistant to drought and high salinity. They are particularly well adapted to poor and disturbed soils thanks to their capacity to establish symbiotic associations with mycorrhizal fungi -both arbuscular and ectomycorrhizal- and with the nitrogen-fixing bacteria Frankia. These trees are now widely distributed in more than 20 African countries. Casuarina are mainly used in forestation programs to rehabilitate degraded or polluted sites, to stabilise sand dunes and to provide fuelwood and charcoal and thus contribute considerably to improving livelihoods and local economies. In this paper, we describe the geographical distribution of Casuarina in Africa, their economic and ecological value and the role of the symbiotic interactions between Casuarina, mycorrhizal fungi and Frankia.

  1. Plant interspecific differences in arbuscular mycorrhizal colonization as a result of soil carbon addition.

    PubMed

    Eschen, René; Müller-Schärer, Heinz; Schaffner, Urs

    2013-01-01

    Soil nutrient availability and colonization by arbuscular mycorrhizal fungi are important and potentially interacting factors shaping vegetation composition and succession. We investigated the effect of carbon (C) addition, aimed at reducing soil nutrient availability, on arbuscular mycorrhizal colonization. Seedlings of 27 plant species with different sets of life-history traits (functional group affiliation, life history strategy and nitrophilic status) were grown in pots filled with soil from a nutrient-rich set-aside field and amended with different amounts of C. Mycorrhizal colonization was progressively reduced along the gradient of increasing C addition in 17 out of 27 species, but not in the remaining species. Grasses had lower colonization levels than forbs and legumes and the decline in AM fungal colonization was more pronounced in legumes than in other forbs and grasses. Mycorrhizal colonization did not differ between annual and perennial species, but decreased more rapidly along the gradient of increasing C addition in plants with high Ellenberg N values than in plants with low Ellenberg N values. Soil C addition not only limits plant growth through a reduction in available nutrients, but also reduces mycorrhizal colonization of plant roots. The effect of C addition on mycorrhizal colonization varies among plant functional groups, with legumes experiencing an overproportional reduction in AM fungal colonization along the gradient of increasing C addition. We therefore propose that for a better understanding of vegetation succession on set-aside fields one may consider the interrelationship between plant growth, soil nutrient availability and mycorrhizal colonization of plant roots.

  2. Arbuscular mycorrhizal fungi increase organic carbon decomposition under elevated carbon dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A major goal of climate change research is to understand whether and how terrestrial ecosystems can sequester more carbon to mitigate rising atmospheric carbon dioxide (CO2) levels. The stimulation of arbuscular mycorrhizal fungi (AMF) by elevated atmospheric CO2 has been assumed to be a major mecha...

  3. Effect of biochar soil-amendments on Allium porrum growth, arbuscular mycorrhizal fungus colonization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aims: Examine the interaction of biochar addition and arbuscular mycorrhizal [AM] fungus inoculation upon growth and Zn and Cu uptake by Allium porrum L. in heavy metal amended soil mix, and relate these responses to physicochemical properties of the biochars. Methods: The experiment was a complete ...

  4. Cover crop mixtures for promoting arbuscular mycorrhizal fungi in production agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arbuscular mycorrhizal fungi (AMF) associate with an estimated 80-90 percent of flowering plants and virtually every crop species that supplies food to the world. AMF play a vital role in nutrient uptake and are particularly adept at increasing phosphorus availability to plants. With the growing e...

  5. Variability in colonization of arbuscular mycorrhizal fungi and its effect on mycorrhizal dependency of improved and unimproved soybean cultivars.

    PubMed

    Salloum, M S; Guzzo, M C; Velazquez, M S; Sagadin, M B; Luna, C M

    2016-12-01

    Breeding selection of germplasm under fertilized conditions may reduce the frequency of genes that promote mycorrhizal associations. This study was developed to compare variability in mycorrhizal colonization and its effect on mycorrhizal dependency (MD) in improved soybean genotypes (I-1 and I-2) with differential tolerance to drought stress, and in unimproved soybean genotypes (UI-3 and UI-4). As inoculum, a mixed native arbuscular mycorrhizal fungi (AMF) was isolated from soybean roots, showing spores mostly of the species Funneliformis mosseae. At 20 days, unimproved genotypes followed by I-2, showed an increase in arbuscule formation, but not in I-1. At 40 days, mycorrhizal plants showed an increase in nodulation, this effect being more evident in unimproved genotypes. Mycorrhizal dependency, evaluated as growth and biochemical parameters from oxidative stress was increased in unimproved and I-2 since 20 days, whereas in I-1, MD increased at 40 days. We cannot distinguish significant differences in AMF colonization and MD between unimproved and I-2. However, variability among improved genotypes was observed. Our results suggest that selection for improved soybean genotypes with good and rapid AMF colonization, particularly high arbuscule/hyphae ratio could be a useful strategy for the development of genotypes that optimize AMF contribution to cropping systems.

  6. Common mycorrhizal networks and their effect on the bargaining power of the fungal partner in the arbuscular mycorrhizal symbiosis

    PubMed Central

    Bücking, Heike; Mensah, Jerry A.; Fellbaum, Carl R.

    2016-01-01

    ABSTRACT Arbuscular mycorrhizal (AM) fungi form mutualistic interactions with the majority of land plants, including some of the most important crop species. The fungus takes up nutrients from the soil, and transfers these nutrients to the mycorrhizal interface in the root, where these nutrients are exchanged against carbon from the host. AM fungi form extensive hyphal networks in the soil and connect with their network multiple host plants. These common mycorrhizal networks (CMNs) play a critical role in the long-distance transport of nutrients through soil ecosystems and allow the exchange of signals between the interconnected plants. CMNs affect the survival, fitness, and competitiveness of the fungal and plant species that interact via these networks, but how the resource transport within these CMNs is controlled is largely unknown. We discuss the significance of CMNs for plant communities and for the bargaining power of the fungal partner in the AM symbiosis. PMID:27066184

  7. Soil Characteristics Driving Arbuscular Mycorrhizal Fungal Communities in Semiarid Mediterranean Soils

    PubMed Central

    Torres, Maria Pilar; Montesinos-Navarro, Alicia; Roldán, Antonio

    2016-01-01

    ABSTRACT We investigated communities of arbuscular mycorrhizal fungi (AMF) in the roots and the rhizosphere soil of Brachypodium retusum in six different natural soils under field conditions. We explored phylogenetic patterns of AMF composition using indicator species analyses to find AMF associated with a given habitat (root versus rhizosphere) or soil type. We tested whether the AMF characteristics of different habitats or contrasting soils were more closely related than expected by chance. Then we used principal-component analysis and multivariate analysis of variance to test for the relative contribution of each factor in explaining the variation in fungal community composition. Finally, we used redundancy analysis to identify the soil properties that significantly explained the differences in AMF communities across soil types. The results pointed out a tendency of AMF communities in roots to be closely related and different from those in the rhizosphere soil. The indicator species analyses revealed AMF associated with rhizosphere soil and the root habitat. Soil type also determined the distribution of AMF communities in soils, and this effect could not be attributed to a single soil characteristic, as at least three soil properties related to microbial activity, i.e., pH and levels of two micronutrients (Mn and Zn), played significant roles in triggering AMF populations. IMPORTANCE Communities of arbuscular mycorrhizal fungi (AMF) are main components of soil biota that can determine the productivity of ecosystems. These fungal assemblages vary across host plants and ecosystems, but the main ecological processes that shape the structures of these communities are still largely unknown. A field study in six different soil types from semiarid areas revealed that AMF communities are significantly influenced by habitat (soil versus roots) and soil type. In addition, three soil properties related to microbiological activity (i.e., pH and manganese and zinc levels

  8. Determinants of arbuscular mycorrhizal communities - soil properties or land use?

    NASA Astrophysics Data System (ADS)

    Jansa, J.; Erb, A.; Oberholzer, H.-R.; Šmilauer, P.; Egli, S.

    2012-04-01

    Arbuscular mycorrhizal (AM) fungi accompanied terrestrial plants since some 500 million years of their evolution and are now widespread in all continents and virtually all soils of the world. They establish symbiotic interactions with a majority of extant higher plant species including most economically important plants. They are heavily implicated in plant nutrition, plant-soil carbon cycling, and tolerance to environmental stresses. Under field conditions, AM fungi usually form multispecies communities both in the soils and in plant roots, and it is becoming well established that various human interventions like cropping, crop rotation, tillage, and fertilization may all drive changes in the community composition of these fungi and, consequently, in the symbiotic benefits to the plants. Most of current evidence is stemming from individual short and long-term field trials, and the different studies usually employed diverse approaches, limiting the comparability of results across sites. Large scale sampling designs using unified research methods across different soil types and land use systems have hardly been employed so far. However, this would be imperative to allow direct comparisons of the effects of various environmental conditions (soil type, climate) and human land use practices on the indigenous soil-borne symbiotic microbes in general and the AM fungi in particular. To contribute to filling this gap, we conducted molecular profiling of AM communities in more than 150 Swiss agricultural soils, developed on a range of parent materials, covering a wide range of soil properties such as pH value, texture, carbon content and altitude, and including highly productive fields through alpine pastures. This study indicated strong correlations between AM fungal community patterns and features like soil pH and texture, as well as some consistent shifts in fungal communities due to specific aspects of land use like tillage or fertilization. These results thus appear to

  9. 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.).

  10. Activation of Symbiosis Signaling by Arbuscular Mycorrhizal Fungi in Legumes and Rice[OPEN

    PubMed Central

    Sun, Jongho; Miller, J. Benjamin; Granqvist, Emma; Wiley-Kalil, Audrey; Gobbato, Enrico; Maillet, Fabienne; Cottaz, Sylvain; Samain, Eric; Venkateshwaran, Muthusubramanian; Fort, Sébastien; Morris, Richard J.; Ané, Jean-Michel; Dénarié, Jean; Oldroyd, Giles E.D.

    2015-01-01

    Establishment of arbuscular mycorrhizal interactions involves plant recognition of diffusible signals from the fungus, including lipochitooligosaccharides (LCOs) and chitooligosaccharides (COs). Nitrogen-fixing rhizobial bacteria that associate with leguminous plants also signal to their hosts via LCOs, the so-called Nod factors. Here, we have assessed the induction of symbiotic signaling by the arbuscular mycorrhizal (Myc) fungal-produced LCOs and COs in legumes and rice (Oryza sativa). We show that Myc-LCOs and tetra-acetyl chitotetraose (CO4) activate the common symbiosis signaling pathway, with resultant calcium oscillations in root epidermal cells of Medicago truncatula and Lotus japonicus. The nature of the calcium oscillations is similar for LCOs produced by rhizobial bacteria and by mycorrhizal fungi; however, Myc-LCOs activate distinct gene expression. Calcium oscillations were activated in rice atrichoblasts by CO4, but not the Myc-LCOs, whereas a mix of CO4 and Myc-LCOs activated calcium oscillations in rice trichoblasts. In contrast, stimulation of lateral root emergence occurred following treatment with Myc-LCOs, but not CO4, in M. truncatula, whereas both Myc-LCOs and CO4 were active in rice. Our work indicates that legumes and non-legumes differ in their perception of Myc-LCO and CO signals, suggesting that different plant species respond to different components in the mix of signals produced by arbuscular mycorrhizal fungi. PMID:25724637

  11. Benzo[a]pyrene induced lipid changes in the monoxenic arbuscular mycorrhizal chicory roots.

    PubMed

    Debiane, Djouher; Calonne, Maryline; Fontaine, Joël; Laruelle, Frédéric; Grandmougin-Ferjani, Anne; Lounès-Hadj Sahraoui, Anissa

    2012-03-30

    Arbuscular mycorrhizal (AM) colonization may be one of the means that protects plants and allows them to thrive on polycyclic aromatic hydrocarbon-polluted soils including the carcinogenic benzo(a)pyrene (B[a]P). To understand the mechanisms involved in the AM symbiosis tolerance to B[a]P toxicity, the purpose of this study was to compare the lipid compositions as well as the contents between mycorrhizal and non-mycorrhizal chicory root cultures grown in vitro under B[a]P pollution. Firstly, B[a]P induced significant decreases of the Glomalean lipid markers: C16:1ω5 and 24-methyl/methylene sterol amounts in AM roots indicating a reduced AM fungal development inside the roots. Secondly, whereas increases in fatty acid amounts after B[a]P application were measured in non-mycorrhizal roots, no changes were shown in mycorrhizal roots. On the other hand, while, after treatment with B[a]P, the total phospholipid contents were unmodified in non-mycorrhizal roots in comparison with the control, drastic reductions were observed in mycorrhizal roots, mainly owing to decreases in phosphatidylethanolamine and phosphatidylcholine. Moreover, B[a]P affected AM root sterols by reducing stigmasterol. In conclusion, the findings presented in this paper have highlighted, for the first time, significant changes in the AM root lipid metabolism under B[a]P pollution and have culminated on their role in the defense/protection mechanisms.

  12. Phylogenetic structure of arbuscular mycorrhizal fungal communities along an elevation gradient.

    PubMed

    Egan, Cameron P; Callaway, Ragan M; Hart, Miranda M; Pither, Jason; Klironomos, John

    2017-04-01

    Despite the importance of arbuscular mycorrhizal (AM) fungi within terrestrial ecosystems, we know little about how natural AM fungal communities are structured. To date, the majority of studies examining AM fungal community diversity have focused on single habitats with similar environmental conditions, with relatively few studies having assessed the diversity of AM fungi over large-scale environmental gradients. In this study, we characterized AM fungal communities in the soil along a high-elevation gradient in the North American Rocky Mountains. We focused on phylogenetic patterns of AM fungal communities to gain insight into how AM fungal communities are naturally assembled. We found that alpine AM fungal communities had lower phylogenetic diversity relative to lower elevation communities, as well as being more heterogeneous in composition than either treeline or subalpine communities. AM fungal communities were phylogenetically clustered at all elevations sampled, suggesting that environmental filtering, either selection by host plants or fungal niches, is the primary ecological process structuring communities along the gradient.

  13. Arbuscular mycorrhizal fungal communities in plant roots are not random assemblages.

    PubMed

    Davison, John; Öpik, Maarja; Daniell, Tim J; Moora, Mari; Zobel, Martin

    2011-10-01

    We investigated whether arbuscular mycorrhizal fungal (AMF) communities in plant roots are random subsets of the local taxon pool or whether they reflect the action of certain community assembly rules. We studied AMF small subunit rRNA gene sequence groups in the roots of plant individuals belonging to 11 temperate forest understorey species. Empirical data were compared with null models assuming random association. Distinct fungal species pools were present in young and old successional forest. In both forest types, the richness of plant-AMF associations was lower than expected by chance, indicating a degree of partner selectivity. AMF communities were generally not characteristic of individual plant species, but those associated with ecological groups of plant species - habitat generalists and forest specialists - were nonrandom subsets of the available pool of fungal taxa and differed significantly from each other. Moreover, these AMF communities were the least distinctive in spring, but developed later in the season. Comparison with a global database showed that generalist plants tend to associate with generalist AMF. Thus, the habitat range of the host and a possible interaction with season played a role in the assembly of AMF communities in individual plant root systems.

  14. Synergism and context dependency of interactions between arbuscular mycorrhizal fungi and rhizobia with a prairie legume.

    PubMed

    Larimer, Anna L; Clay, Keith; Bever, James D

    2014-04-01

    Biotic interactions play primary roles in major theories of the distribution and abundance of species, yet the nature of these biotic interactions can depend upon the larger ecological community. Leguminous plants, for example, commonly associate with both arbuscular mycorrhizal fungi (AMF) and rhizobia bacteria, and the pairwise interactions may depend upon the presence or identity of the third partner. To determine if the dynamics of plant-AMF and plant-rhizobia interactions are affected by the alternate symbiont, we manipulated the presence and identity of each symbiont, as well as levels of the nutrients supplied by each symbiont (nitrogen and phosphorus), on the growth of prairie legume Amorpha canescens. We found strong synergistic effects of AMF and rhizobia inoculation on plant biomass production that were independent of nutrient levels. AMF and rhizobia responses were each influenced by the other, but not in the same direction. AMF infection increased root nodule number and mass, but rhizobia inoculation decreased AMF hyphal colonization of roots. The relative benefits of each combination of symbionts depended upon phosphorus level. The effect of nitrogen was also contingent on the biotic environment where nitrogen addition decreased nodulation, but this decrease was reduced with coinfection by AMF. Our results demonstrate a strong contingency on the co-occurrence of AMF and rhizobia for the long-term fitness of A. canescens, and suggest that the belowground community is critical for the success of this species in tallgrass prairies.

  15. Isolation and identification of soil bacteria growing at the expense of arbuscular mycorrhizal fungi.

    PubMed

    Lecomte, Julie; St-Arnaud, Marc; Hijri, Mohamed

    2011-04-01

    Soil-microorganism symbioses are of fundamental importance for plant adaptation to the environment. Research in microbial ecology has revealed that some soil bacteria are associated with arbuscular mycorrhizal fungi (AMF). However, these interactions may be much more complex than originally thought. To assess the type of bacteria associated with AMF, we initially isolated spores of Glomus irregulare from an Agrostis stolonifera rhizosphere. The spores were washed with sterile water and plated onto G. irregulare mycelium growing in vitro in a root-free compartment of bicompartmented Petri dishes. We hypothesized that this system should select for bacteria closely associated with the fungus because the only nutrients available to the bacteria were those derived from the hyphae. Twenty-nine bacterial colonies growing on the AMF hyphae were subcultured and identified using 16S rRNA gene sequences. All bacterial isolates showed high sequence identity to Bacillus cereus, Bacillus megaterium, Bacillus simplex, Kocuria rhizophila, Microbacterium ginsengisoli, Sphingomonas sp. and Variovorax paradoxus. We also assessed bacterial diversity on the surface of spores by PCR-denaturating gradient gel electrophoresis. Finally, we used live cellular imaging to show that the bacteria isolated can grow on the surface of hyphae with different growing patterns in contrast to Escherichia coli as a control.

  16. Effects of inoculum additions in the presence of a preestablished arbuscular mycorrhizal fungal community.

    PubMed

    Janousková, Martina; Krak, Karol; Wagg, Cameron; Štorchová, Helena; Caklová, Petra; Vosátka, Miroslav

    2013-10-01

    Communities of arbuscular mycorrhizal fungi (AMF) are crucial for promoting plant productivity in most terrestrial systems, including anthropogenically managed ecosystems. Application of AMF inocula has therefore become a widespread practice. It is, however, pertinent to understand the mechanisms that govern AMF community composition and their performance in order to design successful manipulations. Here we assess whether the composition and plant growth-promotional effects of a synthetic AMF community can be altered by inoculum additions of the isolates forming the community. This was determined by following the effects of three AMF isolates, each inoculated in two propagule densities into a preestablished AMF community. Fungal abundance in roots and plant growth were evaluated in three sequential harvests. We found a transient positive response in AMF abundance to the intraspecific inoculation only in the competitively weakest isolate. The other two isolates responded negatively to intra- and interspecific inoculations, and in some cases plant growth was also reduced. Our results suggest that increasing the AMF density may lead to increased competition among fungi and a trade-off with their ability to promote plant productivity. This is a key ecological aspect to consider when introducing AMF into soils.

  17. Land use influences arbuscular mycorrhizal fungal communities in the farming-pastoral ecotone of northern China.

    PubMed

    Xiang, Dan; Verbruggen, Erik; Hu, Yajun; Veresoglou, Stavros D; Rillig, Matthias C; Zhou, Wenping; Xu, Tianle; Li, Huan; Hao, Zhipeng; Chen, Yongliang; Chen, Baodong

    2014-12-01

    We performed a landscape-scale investigation to compare the arbuscular mycorrhizal fungal (AMF) communities between grasslands and farmlands in the farming-pastoral ecotone of northern China. AMF richness and community composition were examined with 454 pyrosequencing. Structural equation modelling (SEM) and multivariate analyses were applied to disentangle the direct and indirect effects (mediated by multiple environmental factors) of land use on AMF. Land use conversion from grassland to farmland significantly reduced AMF richness and extraradical hyphal length density, and these land use types also differed significantly in AMF community composition. SEM showed that the effects of land use on AMF richness and hyphal length density in soil were primarily mediated by available phosphorus and soil structural quality. Soil texture was the strongest predictor of AMF community composition. Soil carbon, nitrogen and soil pH were also significantly correlated with AMF community composition, indicating that these abiotic variables could be responsible for some of the community composition differences among sites. Our study shows that land use has a partly predictable effect on AMF communities across this ecologically relevant area of China, and indicates that high soil phosphorus concentrations and poor soil structure are particularly detrimental to AMF in this fragile ecosystem.

  18. Mollicutes-related endobacteria thrive inside liverwort-associated arbuscular mycorrhizal fungi.

    PubMed

    Desirò, Alessandro; Naumann, Maria; Epis, Sara; Novero, Mara; Bandi, Claudio; Genre, Andrea; Bonfante, Paola

    2013-03-01

    Arbuscular mycorrhizal fungi (AMF) can host Gram-positive endobacteria (BLOs) in their cytoplasm. These have been identified as Mollicutes-related microbes based on an inventory of AMF spores from fungal collections. Bacteria-like organisms (BLOs) of unknown identity have also been reported in the cytoplasm of AMF associated with liverworts, the earliest-diverged extant lineage of land plants. A combination of morphological, molecular and phylogenetic analyses revealed that three samples of two liverwort species (Conocephalum conicum and Lunularia cruciata) growing spontaneously in a botanical garden harboured AMF belonging to Glomerales, and these, in turn, hosted coccoid BLOs. 16S rDNA sequences from these BLOs clustered with the Mollicutes sequences identified from the spore collections but revealed the presence of novel phylotypes. Electron microscopy and fluorescence in situ hybridization (FISH) confirmed the presence of BLOs inside the cytoplasm of AMF hyphae colonizing the liverwort thalli. The high genetic variability of BLOs in liverwort-AMF associations thriving in the same ecological niche raises questions about the mechanisms underlying such diversity.

  19. Arbuscular mycorrhizal associations and occurrence of dark septate endophytes in the roots of Brazilian weed plants.

    PubMed

    Massenssini, André Marcos; Bonduki, Víctor Hugo Araújo; Tótola, Marcos Rogério; Ferreira, Francisco Affonso; Costa, Maurício Dutra

    2014-02-01

    The ecology of weed plants includes their interactions with soil microorganisms, such as mutualistic partners that may contribute to their adaptation and competitive success in the agricultural fields. Despite the importance of microorganisms to plant growth, knowledge on weed-symbiont associations is still incipient compared to crops. Thus, a survey for the presence of arbuscular mycorrhiza (AM) and dark septate endophyte (DSE) associations in the roots of 50 weed species was done in three distinct areas during the dry and rainy seasons. We found that 41 and 29 out of the 50 species were associated with AM fungi and DSE, respectively, and 27 species presented both associations. All the plant species not forming AM belong to families thought to be nonmycorrhizal, such as Amaranthaceae, Commelinaceae, Brassicaceae, and Cyperaceae. The most common morphotype of AM observed was the Arum-type. No significant differences were found in root length colonization between the areas or seasons. For 19 species surveyed, this is the first report on their mycorrhizal status.

  20. Arbuscular mycorrhizal assemblages in native plant roots change in the presence of invasive exotic grasses

    USGS Publications Warehouse

    Hawkes, C.V.; Belnap, J.; D'Antonio, C.; Firestone, M.K.

    2006-01-01

    Plant invasions have the potential to significantly alter soil microbial communities, given their often considerable aboveground effects. We examined how plant invasions altered the arbuscular mycorrhizal fungi of native plant roots in a grassland site in California and one in Utah. In the California site, we used experimentally created plant communities composed of exotic (Avena barbata, Bromus hordeaceus) and native (Nassella pulchra, Lupinus bicolor) monocultures and mixtures. In the Utah semi-arid grassland, we took advantage of invasion by Bromus tectorum into long-term plots dominated by either of two native grasses, Hilaria jamesii or Stipa hymenoides. Arbuscular mycorrhizal fungi colonizing roots were characterized with PCR amplification of the ITS region, cloning, and sequencing. We saw a significant effect of the presence of exotic grasses on the diversity of mycorrhizal fungi colonizing native plant roots. In the three native grasses, richness of mycorrhizal fungi decreased; in the native forb at the California site, the number of fungal RFLP patterns increased in the presence of exotics. The exotic grasses also caused the composition of the mycorrhizal community in native roots to shift dramatically both in California, with turnover of Glomus spp., and Utah, with replacement of Glomus spp. by apparently non-mycorrhizal fungi. Invading plants may be able to influence the network of mycorrhizal fungi in soil that is available to natives through either earlier root activity or differential carbon provision compared to natives. Alteration of the soil microbial community by plant invasion can provide a mechanism for both successful invasion and the resulting effects of invaders on the ecosystem. ?? Springer 2006.

  1. Chemical identification and functional analysis of apocarotenoids involved in the development of arbuscular mycorrhizal symbiosis.

    PubMed

    Akiyama, Kohki

    2007-06-01

    Arbuscular mycorrhizae formed between more than 80% of land plants and arbuscular mycorrhizal (AM) fungi represent the most widespread symbiosis on the earth. AM fungi facilitate the uptake of soil nutrients, especially phosphate, by plants, and in return obtain carbohydrates from hosts. Apocarotenoids, oxidative cleavage products of carotenoids, have been found to play a critical role in the establishment of AM symbiosis. Strigolactones previously isolated as seed-germination stimulants for root parasitic weeds act as a chemical signal for AM fungi during presymbiotic stages. Stimulation of carotenoid metabolism, leading to massive accumulation of mycorradicin and cyclohexenone derivatives, occurs during root colonization by AM fungi. This review highlights research into the chemical identification of arbuscular mycorrhiza-related apocarotenoids and their role in the regulation and establishment of AM symbiosis conducted in the past 10 years.

  2. Effectiveness of arbuscular mycorrhizal fungi in phytoremediation of lead- contaminated soil by vetiver grass.

    PubMed

    Bahraminia, Mahboobeh; Zarei, Mehdi; Ronaghi, Abdolmajid; Ghasemi-Fasaei, Reza

    2016-01-01

    A greenhouse experiment was conducted to evaluate the effectiveness of arbuscular mycorrhizal (AM) fungi in phytoremediation of lead (Pb)-contaminated soil by vetiver grass. Experiment was a factorial arranged in a completely randomized design. Factors included four Pb levels (50, 200, 400, and 800 mg kg(-1)) as Pb (NO3)2, AM fungi at three levels (non mycorrhizal (NM) control, Rhizophagus intraradices, Glomus versiforme). Shoot and root dry weights (SDW and RDW) decreased as Pb levels increased. Mycorrhizal inoculation increased SDW and RDW compared to NM control. With mycorrhizal inoculation and increasing Pb levels, Pb uptake of shoot and root increased compared to those of NM control. Root colonization increased with mycorrhizal inoculation but decreased as Pb levels increased. Phosphorus concentration and uptake in shoot of plants inoculated with AM fungi was significantly higher than NM control at 200 and 800 mg Pb kg(-1). The Fe concentration, Fe and Mn uptake of shoot in plants inoculated with Rhizophagus intraradices in all levels of Pb were significantly higher than NM control. Mycorrhizal inoculation increased Pb extraction, uptake and translocation efficiencies. Lead translocation factor decreased as Pb levels increased; however inoculation with AM fungi increased Pb translocation.

  3. Linking root traits to nutrient foraging in arbuscular mycorrhizal trees in a temperate forest.

    PubMed

    Eissenstat, David M; Kucharski, Joshua M; Zadworny, Marcin; Adams, Thomas S; Koide, Roger T

    2015-10-01

    The identification of plant functional traits that can be linked to ecosystem processes is of wide interest, especially for predicting vegetational responses to climate change. Root diameter of the finest absorptive roots may be one plant trait that has wide significance. Do species with relatively thick absorptive roots forage in nutrient-rich patches differently from species with relatively fine absorptive roots? We measured traits related to nutrient foraging (root morphology and architecture, root proliferation, and mycorrhizal colonization) across six coexisting arbuscular mycorrhizal (AM) temperate tree species with and without nutrient addition. Root traits such as root diameter and specific root length were highly correlated with root branching intensity, with thin-root species having higher branching intensity than thick-root species. In both fertilized and unfertilized soil, species with thin absorptive roots and high branching intensity showed much greater root length and mass proliferation but lower mycorrhizal colonization than species with thick absorptive roots. Across all species, fertilization led to increased root proliferation and reduced mycorrhizal colonization. These results suggest that thin-root species forage more by root proliferation, whereas thick-root species forage more by mycorrhizal fungi. In mineral nutrient-rich patches, AM trees seem to forage more by proliferating roots than by mycorrhizal fungi.

  4. Role of arbuscular mycorrhizal symbiosis in root mineral uptake under CaCO3 stress.

    PubMed

    Labidi, Sonia; Ben Jeddi, Fayçal; Tisserant, Benoit; Debiane, Djouher; Rezgui, Salah; Grandmougin-Ferjani, Anne; Lounès-Hadj Sahraoui, Anissa

    2012-07-01

    This study investigated the effects of increasing CaCO(3) concentrations (0, 5, 10, 20 mM) on arbuscular mycorrhizal (AM) symbiosis establishment as well as on chicory root growth and mineral nutrient uptake in a monoxenic system. Although CaCO(3) treatments significantly decreased root growth and altered the symbiosis-related development steps of the AM fungus Rhizophagus irregularis (germination, germination hypha elongation, root colonization rate, extraradical hyphal development, sporulation), the fungus was able to completely fulfill its life cycle. Even when root growth decreased more drastically in mycorrhizal roots than in non-mycorrhizal ones in the presence of high CaCO(3) levels, the AM symbiosis was found to be beneficial for root mineral uptake. Significant increases in P, N, Fe, Zn and Cu concentrations were recorded in the mycorrhizal roots. Whereas acid and alkaline phosphatase enzymatic activities remained constant in mycorrhizal roots, they were affected in non-mycorrhizal roots grown in the presence of CaCO(3) when compared with the control.

  5. Plant hormones in arbuscular mycorrhizal symbioses: an emerging role for gibberellins

    PubMed Central

    Foo, Eloise; Ross, John J.; Jones, William T.; Reid, James B.

    2013-01-01

    Background and Aims Arbuscular mycorrhizal symbioses are important for nutrient acquisition in >80 % of terrestrial plants. Recently there have been major breakthroughs in understanding the signals that regulate colonization by the fungus, but the roles of the known plant hormones are still emerging. Here our understanding of the roles of abscisic acid, ethylene, auxin, strigolactones, salicylic acid and jasmonic acid is discussed, and the roles of gibberellins and brassinosteroids examined. Methods Pea mutants deficient in gibberellins, DELLA proteins and brassinosteroids are used to determine whether fungal colonization is altered by the level of these hormones or signalling compounds. Expression of genes activated during mycorrhizal colonization is also monitored. Key Results Arbuscular mycorrhizal colonization of pea roots is substantially increased in gibberellin-deficient na-1 mutants compared with wild-type plants. This is reversed by application of GA3. Mutant la cry-s, which lacks gibberellin signalling DELLA proteins, shows reduced colonization. These changes were parallelled by changes in the expression of genes associated with mycorrhizal colonization. The brassinosteroid-deficient lkb mutant showed no change in colonization. Conclusions Biologically active gibberellins suppress arbuscule formation in pea roots, and DELLA proteins are essential for this response, indicating that this role occurs within the root cells. PMID:23508650

  6. The arbuscular mycorrhizal fungus Rhizophagus irregularis differentially regulates the copper response of two maize cultivars differing in copper tolerance.

    PubMed

    Merlos, Miguel A; Zitka, Ondrej; Vojtech, Adam; Azcón-Aguilar, Concepción; Ferrol, Nuria

    2016-12-01

    Arbuscular mycorrhiza can increase plant tolerance to heavy metals. The effects of arbuscular mycorrhiza on plant metal tolerance vary depending on the fungal and plant species involved. Here, we report the effect of the arbuscular mycorrhizal fungus Rhizophagus irregularis on the physiological and biochemical responses to Cu of two maize genotypes differing in Cu tolerance, the Cu-sensitive cv. Orense and the Cu-tolerant cv. Oropesa. Development of the symbiosis confers an increased Cu tolerance to cv. Orense. Root and shoot Cu concentrations were lower in mycorrhizal than in non-mycorrhizal plants of both cultivars. Shoot lipid peroxidation increased with soil Cu content only in non-mycorrhizal plants of the Cu-sensitive cultivar. Root lipid peroxidation increased with soil Cu content, except in mycorrhizal plants grown at 250mg Cu kg(-1)soil. In shoots of mycorrhizal plants of both cultivars, superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase activities were not affected by soil Cu content. In Cu-supplemented soils, total phytochelatin content increased in shoots of mycorrhizal cv. Orense but decreased in cv. Oropesa. Overall, these data suggest that the increased Cu tolerance of mycorrhizal plants of cv. Orense could be due to an increased induction of shoot phytochelatin biosynthesis by the symbiosis in this cultivar.

  7. 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.

  8. Effect of arbuscular mycorrhizal (G. etunicatum) fungus on antioxidant enzymes activity under zinc toxicity in lettuce plants.

    PubMed

    Farshian, Shadi; Khara, Jalil; Parviz, Malekzadeh

    2007-06-01

    Zinc is one of the eight trace elements which are essential for the normal healthy growth and reproduction of crop plants. Plants possess cellular mechanisms that may be involved in the detoxification of heavy metals and thus confer plants a better tolerance against them. Arbuscular mycorrhizal fungi colonization is one of these mechanisms. Here, the effect of mycorrhizal fungus G. etunicatum on Zn toxicity tolerance through enhanced activity of some of antioxidant enzymes has been studied. Treatments were applied in triplicates of two factorial analyses: (a) mycorrhizal and non-mycorrhizal; (b) 5 levels of Zinc (0, 1.5, 3.5, 5.5, 7.5 mM). Zinc was added to modified Hoagland's nutrient solution (with half P concentration). Plants were grown in growth chamber for 10 weeks. Toxicity symptoms such as necrosis and chlorosis appeared on the leaves. Activity of detoxifying enzymes Guaiacol peroxidase (GUPX) and Ascorbate peroxidase (APX) were measured. GPX activity in roots and shoots of mycorrhizal and non-mycorrhizal plants was increased. Also, APX activity increased in roots and shoots ofmycorrhizal and non-mycorrhizal plants. Root length colonization (RLC) was measured by gridline intersect method. Mycorrhizal colonization decreased due to Zinc exposure. The results indicate the probable role of arbuscular mycorrhizal colonization in stress tolerance.

  9. An integrated functional approach to dissect systemic responses in maize to arbuscular mycorrhizal symbiosis.

    PubMed

    Gerlach, Nina; Schmitz, Jessica; Polatajko, Aleksandra; Schlüter, Urte; Fahnenstich, Holger; Witt, Sandra; Fernie, Alisdair R; Uroic, Kalle; Scholz, Uwe; Sonnewald, Uwe; Bucher, Marcel

    2015-08-01

    Most terrestrial plants benefit from the symbiosis with arbuscular mycorrhizal fungi (AMF) mainly under nutrient-limited conditions. Here the crop plant Zea mays was grown with and without AMF in a bi-compartmented system separating plant and phosphate (Pi) source by a hyphae-permeable membrane. Thus, Pi was preferentially taken up via the mycorrhizal Pi uptake pathway while other nutrients were ubiquitously available. To study systemic effects of mycorrhizal Pi uptake on leaf status, leaves of these plants that display an increased biomass in the presence of AMF were subjected to simultaneous ionomic, transcriptomic and metabolomic analyses. We observed robust changes of the leaf elemental composition, that is, increase of P, S and Zn and decrease of Mn, Co and Li concentration in mycorrhizal plants. Although changes in anthocyanin and lipid metabolism point to an improved P status, a global increase in C versus N metabolism highlights the redistribution of metabolic pools including carbohydrates and amino acids. Strikingly, an induction of systemic defence gene expression and concomitant accumulation of secondary metabolites such as the terpenoids alpha- and beta-amyrin suggest priming of mycorrhizal maize leaves as a mycorrhiza-specific response. This work emphasizes the importance of AM symbiosis for the physiological status of plant leaves and could lead to strategies for optimized breeding of crop species with high growth potential.

  10. 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

  11. Characterization of arbuscular mycorrhizal fungal communities with respect to zonal vegetation in a coastal dune ecosystem.

    PubMed

    Kawahara, Ai; Ezawa, Tatsuhiro

    2013-10-01

    Coastal dune vegetation distributes zonally along the environmental gradients of, e.g., soil disturbance. In the preset study, arbuscular mycorrhizal fungal communities in a coastal dune ecosystem were characterized with respect to tolerance to soil disturbance. Two grass species, Elymus mollis and Miscanthus sinensis, are distributed zonally in the seaward and landward slopes, respectively, in the primary dunes in Ishikari, Japan. The seaward slope is severely disturbed by wind, while the landward slope is stabilized by the thick root system of M. sinensis. The roots and rhizosphere soils of the two grasses were collected from the slopes. The soils were sieved to destruct the fungal hyphal networks, and soil trap culture was conducted to assess tolerance of the communities to disturbance, with parallel analysis of the field communities using a molecular ecological tool. In the landward communities, large shifts in the composition and increases in diversity were observed in the trap culture compared with the field, but in the seaward communities, the impact of trap culture was minimal. The landward field community was significantly nested within the landward trap culture community, implying that most members in the field community did not disappear in the trap culture. No nestedness was observed in the seaward communities. These observations suggest that disturbance-tolerant fungi have been preferentially selected in the seaward slope due to severe disturbance in the habitat. Whereas a limited number of fungi, which are not necessarily disturbance-sensitive, dominate in the stable landward slope, but high-potential diversity has been maintained in the habitat.

  12. Belowground interactions with aboveground consequences: Invasive earthworms and arbuscular mycorrhizal fungi.

    PubMed

    Paudel, Shishir; Longcore, Travis; MacDonald, Beau; McCormick, Melissa K; Szlavecz, Katalin; Wilson, Gail W T; Loss, Scot R

    2016-03-01

    A mounting body of research suggests that invasive nonnative earthworms substantially alter microbial communities, including arbuscular mycorrhizal fungi (AMF). These changes to AMF can cascade to affect plant communities and vertebrate populations. Despite these research advances, relatively little is known about (1) the mechanisms behind earthworms' effects on AMF and (2) the factors that determine the outcomes of earthworm-AMF interactions (i.e., whether AMF abundance is increased or decreased and subsequent effects on plants). We predict that AMF-mediated effects of nonnative earthworms on ecosystems are nearly universal because (1) AMF are important components of most terrestrial ecosystems, (2) nonnative earthworms have become established in nearly every type of terrestrial ecosystem, and (3) nonnative earthworms, due to their burrowing and feeding behavior, greatly affect AMF with potentially profound concomitant effects on plant communities. We highlight the multiple direct and indirect effects of nonnative earthworms on plants and review what is currently known about the interaction between earthworms and AMF. We also illustrate how the effects of nonnative earthworms on plant-AMF mutualisms can alter the structure and stability of aboveground plant communities, as well as the vertebrate communities relying on these habitats. Integrative studies that assess the interactive effects of earthworms and AMF can provide new insights into the role that belowground ecosystem engineers play in altering aboveground ecological processes. Understanding these processes may improve our ability to predict the structure of plant and animal communities in earthworm-invaded regions and to develop management strategies that limit the numerous undesired impacts of earthworms.

  13. Changes in communities of Fusarium and arbuscular mycorrhizal fungi as related to different asparagus cultural factors.

    PubMed

    Yergeau, Etienne; Vujanovic, Vladimir; St-Arnaud, Marc

    2006-07-01

    Asparagus (Asparagus officinalis) is a high-value perennial vegetable crop that has shown a marked decline in productivity after many years of continuous harvesting. This decline is caused by an increase in both abiotic (autotoxicity, harvesting pressure) and biotic stresses [fungal infections, mainly Fusarium crown and root rot (FCRR)]. To gain insight into disease development and possible mitigation strategies, we studied the effects of harvesting, time in the growing season, and field age on FCRR development, Fusarium species composition, and arbuscular mycorrhizal fungi (AMF) communities in both a controlled field experiment and an ecological survey of commercial fields. In one experiment, a 3-year-old asparagus field was subdivided into plots that were harvested or not and sampled throughout the growing season to assess short-term dominant Fusarium species shifts. In addition, diseased and healthy asparagus plants sampled from six commercial fields in the same geographical region were used to assess Fusarium and AMF communities in relation to different parameters. Fusarium and AMF communities were described by using a polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) approach, and results were analyzed by mainly correspondence analysis and canonical correspondence analysis. Results showed that dominant Fusarium taxa assemblages changed throughout the growing season. Harvested plots had significantly more FCRR symptomatic plants at the end of the growing season, but this effect was not related with any trend in Fusarium community structure. Sampling site and plant age significantly influenced AMF community structure, whereas only sampling site consistently influenced the Fusarium community. Diseased and healthy plants harbored similar Fusarium and AMF communities. Shifts in Fusarium community might not be responsible for different disease incidence because they are ubiquitous regardless of plant health status or harvesting regime

  14. Elemental stoichiometry indicates predominant influence of potassium and phosphorus limitation on arbuscular mycorrhizal symbiosis in acidic soil at high altitude.

    PubMed

    Khan, Mohammad Haneef; Meghvansi, Mukesh K; Gupta, Rajeev; Veer, Vijay

    2015-09-15

    The functioning of high-altitude agro-ecosystems is constrained by the harsh environmental conditions, such as low temperatures, acidic soil, and low nutrient supply. It is therefore imperative to investigate the site-specific ecological stoichiometry with respect to AM symbiosis in order to maximize the arbuscular mycorrhizal (AM) benefits for the plants in such ecosystems. Here, we assess the elemental stoichiometry of four Capsicum genotypes grown on acidic soil at high altitude in Arunachal Pradesh, India. Further, we try to identify the predominant resource limitations influencing the symbioses of different Capsicum genotypes with the AM fungi. Foliar and soil elemental stoichiometric relations of Capsicum genotypes were evaluated with arbuscular mycorrhizal (AM) colonization and occurrence under field conditions. AM fungal diversity in rhizosphere, was estimated through PCR-DGGE profiling. Results demonstrated that the symbiotic interaction of various Capsicum genotypes with the AM fungi in acidic soil was not prominent in the study site as evident from the low range of root colonization (21-43.67%). In addition, despite the rich availability of carbon in plant leaves as well as in soil, the carbon-for-phosphorus trade between AMF and plants appeared to be limited. Our results provide strong evidences of predominant influence of the potassium-limitation, in addition to phosphorus-limitation, on AM symbiosis with Capsicum in acidic soil at high altitude. We also conclude that the potassium should be considered in addition to carbon, nitrogen, and phosphorus in further studies investigating the stoichiometric relationships with the AMF symbioses in high altitude agro-ecosystems.

  15. Relative importance of deterministic and stochastic processes in driving arbuscular mycorrhizal fungal assemblage during the spreading of a toxic plant.

    PubMed

    Shi, Guoxi; Liu, Yongjun; Mao, Lin; Jiang, Shengjing; Zhang, Qi; Cheng, Gang; An, Lizhe; Du, Guozhen; Feng, Huyuan

    2014-01-01

    Both deterministic and stochastic processes are expected to drive the assemblages of arbuscular mycorrhizal (AM) fungi, but little is known about the relative importance of these processes during the spreading of toxic plants. Here, the species composition and phylogenetic structure of AM fungal communities colonizing the roots of a toxic plant, Ligularia virgaurea, and its neighborhood plants, were analyzed in patches with different individual densities of L. virgaurea (represents the spreading degree). Community compositions of AM fungi in both root systems were changed significantly by the L. virgaurea spreading, and also these communities fitted the neutral model very well. AM fungal communities in patches with absence and presence of L. virgaurea were phylogenetically random and clustered, respectively, suggesting that the principal ecological process determining AM fungal assemblage shifted from stochastic process to environmental filtering when this toxic plant was present. Our results indicate that deterministic and stochastic processes together determine the assemblage of AM fungi, but the dominant process would be changed by the spreading of toxic plants, and suggest that the spreading of toxic plants in alpine meadow ecosystems might be involving the mycorrhizal symbionts.

  16. Contribution of arbuscular mycorrhizal fungi of sedges to soil aggregation along an altitudinal alpine grassland gradient on the Tibetan Plateau.

    PubMed

    Li, Xiaoliang; Zhang, Junling; Gai, Jingping; Cai, Xiaobu; Christie, Peter; Li, Xiaolin

    2015-08-01

    The diversity of arbuscular mycorrhizal fungi (AMF) in sedges on the Tibetan Plateau remains largely unexplored, and their contribution to soil aggregation can be important in understanding the ecological function of AMF in alpine ecosystems. Roots of Kobresia pygmaea C.B. Clarke and Carex pseudofoetida Kük. in alpine Kobresia pastures along an elevational transect (4149-5033 m) on Mount Mila were analysed for AMF diversity. A structural equation model was built to explore the contribution of biotic factors to soil aggregation. Sedges harboured abundant AMF communities covering seven families and some operational taxonomic units are habitat specific. The two plant species hosted similar AMF communities at most altitudes. The relative abundance of the two sedges contributed largely to soil macroaggregates, followed by extraradical mycorrhizal hyphae (EMH) and total glomalin-related soil protein (T-GRSP). The influence of plant richness was mainly due to its indirect influence on T-GRSP and EMH. There was a strong positive correlation between GRSP and soil total carbon and nitrogen. Our results indicate that mycorrhization might not be a major trait leading to niche differentiation of the two co-occurring sedge species. However, AMF contribute to soil aggregation and thus may have the potential to greatly influence C and N cycling in alpine grasslands.

  17. Relative Importance of Deterministic and Stochastic Processes in Driving Arbuscular Mycorrhizal Fungal Assemblage during the Spreading of a Toxic Plant

    PubMed Central

    Mao, Lin; Jiang, Shengjing; Zhang, Qi; Cheng, Gang; An, Lizhe; Du, Guozhen; Feng, Huyuan

    2014-01-01

    Both deterministic and stochastic processes are expected to drive the assemblages of arbuscular mycorrhizal (AM) fungi, but little is known about the relative importance of these processes during the spreading of toxic plants. Here, the species composition and phylogenetic structure of AM fungal communities colonizing the roots of a toxic plant, Ligularia virgaurea, and its neighborhood plants, were analyzed in patches with different individual densities of L. virgaurea (represents the spreading degree). Community compositions of AM fungi in both root systems were changed significantly by the L. virgaurea spreading, and also these communities fitted the neutral model very well. AM fungal communities in patches with absence and presence of L. virgaurea were phylogenetically random and clustered, respectively, suggesting that the principal ecological process determining AM fungal assemblage shifted from stochastic process to environmental filtering when this toxic plant was present. Our results indicate that deterministic and stochastic processes together determine the assemblage of AM fungi, but the dominant process would be changed by the spreading of toxic plants, and suggest that the spreading of toxic plants in alpine meadow ecosystems might be involving the mycorrhizal symbionts. PMID:24748393

  18. Arbuscular mycorrhizal fungal hyphae contribute to the uptake of polycyclic aromatic hydrocarbons by plant roots.

    PubMed

    Gao, Yanzheng; Cheng, Zhaoxia; Ling, Wanting; Huang, Jing

    2010-09-01

    The arbuscular mycorrhizal (AM) hyphae-mediated uptake of polycyclic aromatic hydrocarbons (PAHs) by the roots of ryegrass (Lolium multiflorum Lam.) was investigated using three-compartment systems. Glomus mosseae and Glomus etunicatum were chosen, and fluorene and phenanthrene were used as representative PAHs. When roots were grown in un-spiked soils, AM hyphae extended into PAH-spiked soil and clearly absorbed and transported PAHs to roots, resulting in high concentrations of fluorene and phenanthrene in roots. This was further confirmed by the batch equilibration experiment, which revealed that the partition coefficients (K(d)) of tested PAHs by mycorrhizal hyphae were 270-356% greater than those by roots, suggesting the great potential of hyphae to absorb PAHs. Because of fluorene's lower molecular weight and higher water solubility, its translocation by hyphae was greater than that of phenanthrene. These results provide new perspectives on the AM hyphae-mediated uptake by plants of organic contaminants from soil.

  19. Phosphate in the arbuscular mycorrhizal symbiosis: transport properties and regulatory roles.

    PubMed

    Javot, Hélène; Pumplin, Nathan; Harrison, Maria J

    2007-03-01

    In response to the colonization by arbuscular mycorrhizal (AM) fungi, plants reprioritize their phosphate (Pi)-uptake strategies to take advantage of nutrient transfer via the fungus. The mechanisms underlying Pi transport are beginning to be understood, and recently, details of the regulation of plant and fungal Pi transporters in the AM symbiosis have been revealed. This review summarizes recent advances in this area and explores current data and hypotheses of how the plant Pi status affects the symbiosis. Finally, suggestions of an interrelationship of Pi and nitrogen (N) in the AM symbiosis are discussed.

  20. Production of native arbuscular mycorrhizal fungi inoculum under different environmental conditions.

    PubMed

    Torres-Arias, Yamir; Fors, Rosalba Ortega; Nobre, Camila; Gómez, Eduardo Furrazola; Berbara, Ricardo Luis Louro

    In order to obtain an arbuscular mycorrhizal fungi (AMF) native inoculum from Sierra de Moa and determine the most appropriate conditions for its big scale production, four light and temperature combinations were tested in three plant species (Calophyllum antillanum, Talipariti elatum and Paspalum notatum). Growth and development parameters, as well as the mycorrhizal functioning of the seedlings were evaluated. The natural light treatment under high temperatures (L-H) was the most suitable for the growth and development of the three plant species, showing the highest total biomass values, mainly of root, and a positive root-shoot ratio balance. This treatment also promoted higher values of root mycorrhizal colonization, external mycelium and AMF spore density. A total of 38 AMF species were identified among the plants and environmental conditions tested. Archaeospora sp.1, Glomus sp.5, Glomus brohultii and G. glomerulatum were observed in all the treatments. The L-H condition can be recommended for native inoculum production, as it promotes a better expression of the AM symbiosis and an elevated production of mycorrhizal propagules.

  1. Hyperaccumulators, arbuscular mycorrhizal fungi and stress of heavy metals.

    PubMed

    Miransari, Mohammad

    2011-01-01

    Use of plants, with hyperaccumulating ability or in association with soil microbes including the symbiotic fungi, arbuscular mycorrhiza (AM), are among the most common biological methods of treating heavy metals in soil. Both hyperaccumulating plants and AM fungi have some unique abilities, which make them suitable to treat heavy metals. Hyperaccumulator plants have some genes, being expressed at the time of heavy metal pollution, and can accordingly localize high concentration of heavy metals to their tissues, without showing the toxicity symptoms. A key solution to the issue of heavy metal pollution may be the proper integration of hyperaccumulator plants and AM fungi. The interactions between the soil microbes and the host plant can also be important for the treatment of soils polluted with heavy metals.

  2. 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.

  3. Effects of arbuscular-mycorrhizal glomus species on drought tolerance: physiological and nutritional plant responses.

    PubMed

    Ruiz-Lozano, J M; Azcon, R; Gomez, M

    1995-02-01

    The tolerance of lettuce plants (Lactuca sativa L. cv. Romana) to drought stress differed with the arbuscular-mycorrhizal fungal isolate with which the plants were associated. Seven fungal species belonging to the genus Glomus were studied for their ability to enhance the drought tolerance of lettuce plants. These fungi had different traits that affected the drought resistance of host plants. The ranking of arbuscular-mycorrhizal fungal effects on drought tolerance, based on the relative decreases in shoot dry weight, was as follows: Glomus deserticola > Glomus fasciculatum > Glomus mosseae > Glomus etunicatum > Glomus intraradices > Glomus caledonium > Glomus occultum. In this comparative study specific mycorrhizal fungi had consistent effects on plant growth, mineral uptake, the CO(inf2) exchange rate, water use efficiency, transpiration, stomatal conductance, photosynthetic phosphorus use efficiency, and proline accumulation under either well-watered or drought-stressed conditions. The ability of the isolates to maintain plant growth effectively under water stress conditions was related to higher transpiration rates, levels of leaf conductance, and proline, N, and P contents. Differences in proline accumulation in leaves among the fungal symbioses suggested that the fungi were able to induce different degrees of osmotic adjustment. The detrimental effects of drought were not related to decreases in photosynthesis or water use efficiency. Neither of these parameters was related to P nutrition. The differences in P and K acquisition, transpiration, and stomatal conductance were related to the mycorrhizal efficiencies of the different fungi. Our observations revealed the propensities of different Glomus species to assert their protective effects during plant water stress. The greater effectiveness of G. deserticola in improving water deficit tolerance was associated with the lowest level of growth reduction (9%) under stress conditions. The growth of plants

  4. Effects of Arbuscular-Mycorrhizal Glomus Species on Drought Tolerance: Physiological and Nutritional Plant Responses

    PubMed Central

    Ruiz-Lozano, J. M.; Azcon, R.; Gomez, M.

    1995-01-01

    The tolerance of lettuce plants (Lactuca sativa L. cv. Romana) to drought stress differed with the arbuscular-mycorrhizal fungal isolate with which the plants were associated. Seven fungal species belonging to the genus Glomus were studied for their ability to enhance the drought tolerance of lettuce plants. These fungi had different traits that affected the drought resistance of host plants. The ranking of arbuscular-mycorrhizal fungal effects on drought tolerance, based on the relative decreases in shoot dry weight, was as follows: Glomus deserticola > Glomus fasciculatum > Glomus mosseae > Glomus etunicatum > Glomus intraradices > Glomus caledonium > Glomus occultum. In this comparative study specific mycorrhizal fungi had consistent effects on plant growth, mineral uptake, the CO(inf2) exchange rate, water use efficiency, transpiration, stomatal conductance, photosynthetic phosphorus use efficiency, and proline accumulation under either well-watered or drought-stressed conditions. The ability of the isolates to maintain plant growth effectively under water stress conditions was related to higher transpiration rates, levels of leaf conductance, and proline, N, and P contents. Differences in proline accumulation in leaves among the fungal symbioses suggested that the fungi were able to induce different degrees of osmotic adjustment. The detrimental effects of drought were not related to decreases in photosynthesis or water use efficiency. Neither of these parameters was related to P nutrition. The differences in P and K acquisition, transpiration, and stomatal conductance were related to the mycorrhizal efficiencies of the different fungi. Our observations revealed the propensities of different Glomus species to assert their protective effects during plant water stress. The greater effectiveness of G. deserticola in improving water deficit tolerance was associated with the lowest level of growth reduction (9%) under stress conditions. The growth of plants

  5. Monitoring CO2 emissions to gain a dynamic view of carbon allocation to arbuscular mycorrhizal fungi.

    PubMed

    Slavíková, Renata; Püschel, David; Janoušková, Martina; Hujslová, Martina; Konvalinková, Tereza; Gryndlerová, Hana; Gryndler, Milan; Weiser, Martin; Jansa, Jan

    2017-01-01

    Quantification of carbon (C) fluxes in mycorrhizal plants is one of the important yet little explored tasks of mycorrhizal physiology and ecology. (13)CO2 pulse-chase labelling experiments are increasingly being used to track the fate of C in these plant-microbial symbioses. Nevertheless, continuous monitoring of both the below- and aboveground CO2 emissions remains a challenge, although it is necessary to establish the full C budget of mycorrhizal plants. Here, a novel CO2 collection system is presented which allows assessment of gaseous CO2 emissions (including isotopic composition of their C) from both belowground and shoot compartments. This system then is used to quantify the allocation of recently fixed C in mycorrhizal versus nonmycorrhizal Medicago truncatula plants with comparable biomass and mineral nutrition. Using this system, we confirmed substantially greater belowground C drain in mycorrhizal versus nonmycorrhizal plants, with the belowground CO2 emissions showing large variation because of fluctuating environmental conditions in the glasshouse. Based on the assembled (13)C budget, the C allocation to the mycorrhizal fungus was between 2.3% (increased (13)C allocation to mycorrhizal substrate) and 2.9% (reduction of (13)C allocation to mycorrhizal shoots) of the plant gross photosynthetic production. Although the C allocation to shoot respiration (measured during one night only) did not differ between the mycorrhizal and nonmycorrhizal plants under our experimental conditions, it presented a substantial part (∼10%) of the plant C budget, comparable to the amount of CO2 released belowground. These results advocate quantification of both above- and belowground CO2 emissions in future studies.

  6. Interaction of Rhizosphere Bacteria, Fertilizer, and Vesicular-Arbuscular Mycorrhizal Fungi with Sea Oats †

    PubMed Central

    Will, M. E.; Sylvia, D. M.

    1990-01-01

    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 N2 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 (CaHPO4) 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. PMID:16348236

  7. Auxin Perception Is Required for Arbuscule Development in Arbuscular Mycorrhizal Symbiosis1[W

    PubMed Central

    Etemadi, Mohammad; Gutjahr, Caroline; Couzigou, Jean-Malo; Zouine, Mohamed; Lauressergues, Dominique; Timmers, Antonius; Audran, Corinne; Bouzayen, Mondher; Bécard, Guillaume; Combier, Jean-Philippe

    2014-01-01

    Most land plant species live in symbiosis with arbuscular mycorrhizal fungi. These fungi differentiate essential functional structures called arbuscules in root cortical cells from which mineral nutrients are released to the plant. We investigated the role of microRNA393 (miR393), an miRNA that targets several auxin receptors, in arbuscular mycorrhizal root colonization. Expression of the precursors of the miR393 was down-regulated during mycorrhization in three different plant species: Solanum lycopersicum, Medicago truncatula, and Oryza sativa. Treatment of S. lycopersicum, M. truncatula, and O. sativa roots with concentrations of synthetic auxin analogs that did not affect root development stimulated mycorrhization, particularly arbuscule formation. DR5-GUS, a reporter for auxin response, was preferentially expressed in root cells containing arbuscules. Finally, overexpression of miR393 in root tissues resulted in down-regulation of auxin receptor genes (transport inhibitor response1 and auxin-related F box) and underdeveloped arbuscules in all three plant species. These results support the conclusion that miR393 is a negative regulator of arbuscule formation by hampering auxin perception in arbuscule-containing cells. PMID:25096975

  8. Establishment and effectiveness of inoculated arbuscular mycorrhizal fungi in agricultural soils.

    PubMed

    Köhl, Luise; Lukasiewicz, Catherine E; van der Heijden, Marcel G A

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) are promoted as biofertilizers for sustainable agriculture. So far, most researchers have investigated the effects of AMF on plant growth under highly controlled conditions with sterilized soil, soil substrates or soils with low available P or low inoculum potential. However, it is still poorly documented whether inoculated AMF can successfully establish in field soils with native AMF communities and enhance plant growth. We inoculated grassland microcosms planted with a grass-clover mixture (Lolium multiflorum and Trifolium pratense) with the arbuscular mycorrhizal fungus Rhizoglomus irregulare. The microcosms were filled with eight different unsterilized field soils that varied greatly in soil type and chemical characteristics and indigenous AMF communities. We tested whether inoculation with AMF enhanced plant biomass and R. irregulare abundance using a species specific qPCR. Inoculation increased the abundance of R. irregulare in all soils, irrespective of soil P availability, the initial abundance of R. irregulare or the abundance of native AM fungal communities. AMF inoculation had no effect on the grass but significantly enhanced clover yield in five out of eight field soils. The results demonstrate that AMF inoculation can be successful, even when soil P availability is high and native AMF communities are abundant.

  9. Intraradical colonization by arbuscular mycorrhizal fungi triggers induction of a lipochitooligosaccharide receptor

    NASA Astrophysics Data System (ADS)

    Rasmussen, S. R.; Füchtbauer, W.; Novero, M.; Volpe, V.; Malkov, N.; Genre, A.; Bonfante, P.; Stougaard, J.; Radutoiu, S.

    2016-07-01

    Functional divergence of paralogs following gene duplication is one of the mechanisms leading to evolution of novel pathways and traits. Here we show that divergence of Lys11 and Nfr5 LysM receptor kinase paralogs of Lotus japonicus has affected their specificity for lipochitooligosaccharides (LCOs) decorations, while the innate capacity to recognize and induce a downstream signalling after perception of rhizobial LCOs (Nod factors) was maintained. Regardless of this conserved ability, Lys11 was found neither expressed, nor essential during nitrogen-fixing symbiosis, providing an explanation for the determinant role of Nfr5 gene during Lotus-rhizobia interaction. Lys11 was expressed in root cortex cells associated with intraradical colonizing arbuscular mycorrhizal fungi. Detailed analyses of lys11 single and nfr1nfr5lys11 triple mutants revealed a functional arbuscular mycorrhizal symbiosis, indicating that Lys11 alone, or its possible shared function with the Nod factor receptors is not essential for the presymbiotic phases of AM symbiosis. Hence, both subfunctionalization and specialization appear to have shaped the function of these paralogs where Lys11 acts as an AM-inducible gene, possibly to fine-tune later stages of this interaction.

  10. Intraradical colonization by arbuscular mycorrhizal fungi triggers induction of a lipochitooligosaccharide receptor

    PubMed Central

    Rasmussen, S. R.; Füchtbauer, W.; Novero, M.; Volpe, V.; Malkov, N.; Genre, A.; Bonfante, P.; Stougaard, J.; Radutoiu, S.

    2016-01-01

    Functional divergence of paralogs following gene duplication is one of the mechanisms leading to evolution of novel pathways and traits. Here we show that divergence of Lys11 and Nfr5 LysM receptor kinase paralogs of Lotus japonicus has affected their specificity for lipochitooligosaccharides (LCOs) decorations, while the innate capacity to recognize and induce a downstream signalling after perception of rhizobial LCOs (Nod factors) was maintained. Regardless of this conserved ability, Lys11 was found neither expressed, nor essential during nitrogen-fixing symbiosis, providing an explanation for the determinant role of Nfr5 gene during Lotus-rhizobia interaction. Lys11 was expressed in root cortex cells associated with intraradical colonizing arbuscular mycorrhizal fungi. Detailed analyses of lys11 single and nfr1nfr5lys11 triple mutants revealed a functional arbuscular mycorrhizal symbiosis, indicating that Lys11 alone, or its possible shared function with the Nod factor receptors is not essential for the presymbiotic phases of AM symbiosis. Hence, both subfunctionalization and specialization appear to have shaped the function of these paralogs where Lys11 acts as an AM-inducible gene, possibly to fine-tune later stages of this interaction. PMID:27435342

  11. Arbuscular mycorrhizal association enhances drought tolerance potential of promising bioenergy grass (Saccharum arundinaceum retz.).

    PubMed

    Mirshad, P P; Puthur, Jos T

    2016-07-01

    The influence of arbuscular mycorrhizal fungi (AMF) (Glomus spp.) on some physiological and biochemical characteristics of bioenergy grass Saccharum arundinaceum subjected to drought stress was studied. The symbiotic association of Glomus spp. was established with S. arundinaceum, a potential bioenergy grass as evident from the increase in percentage of root infection and distribution frequency of vesicles when compared with non-arbuscular mycorrhizal plants. AMF-treated plants exhibited an enhanced accumulation of osmolytes such as sugars and proline and also increased protein content under drought. AMF association significantly increased the accumulation of non-enzymatic antioxidants like phenols, ascorbate and glutathione as well as enhanced the activities of antioxidant enzymes such as SOD (superoxide dismutase), APX (ascorbate peroxidase) and GPX (guaiacol peroxidase) resulting in reduced lipid peroxidation in S. arundinaceum. AMF symbiosis also ameliorated the drought-induced reduction of total chlorophyll content and activities of photosystem I and II. The maximum quantum efficiency of PS II (F v/F m) and potential photochemical efficiency (F v/F o) were higher in AMF plants as compared to non-AMF plants under drought stress. These results indicate that AMF association alleviate drought stress in S. arundinaceum by the accumulation of osmolytes and non-enzymatic antioxidants and enhanced activities of antioxidant enzymes, and hence, the photosynthetic efficiency is improved resulting in increased biomass production. AMF association with energy grasses also improves the acclimatization of S. arundinaceum for growing in marginal lands of drought-affected soils.

  12. [Colonization of arbuscular mycorrhizal fungi and dark septate endophytes in Panax notoginseng].

    PubMed

    Zhang, Zhihui; Chen, Di; Zhao, Dandan; Jin, Hang; Li, Lingfei

    2011-09-01

    Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) colonizing Panax notoginseng in three main producing areas in Wenshan Prefecture of Yunan province were investigated. The fungal colonization of 144 roots samples including healthy and rot roots of P. notoginseng with different age were observed by means of acid fuchsin stain. The results showed that P. notoginseng was the typical arbuscular mycorrhizal plant. Although there was no significant difference in AMF and DSE colonization among three sites, the total colonization of AMF was significantly higher than that of DSE. Statistical analysis demonstrated that the fresh weight of P. notoginseng root was positively significantly correlated with the colonization of AMF, but not with the colonization of DSE. These results suggest that AMF may play more important role than DSE in improving the yield and quality of P. notoginseng. Furthermore, AMF colonization of healthy P. notoginseng was higher than that of plant with root rot, which suggested that AMF could defend P. notoginseng against root rot pathogens. AMF have great potentiality and broad prospect to control root rot of P. notoginseng.

  13. 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.

  14. 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.

  15. Arbuscular mycorrhizal symbiosis influences strigolactone production under salinity and alleviates salt stress in lettuce plants.

    PubMed

    Aroca, Ricardo; Ruiz-Lozano, Juan Manuel; Zamarreño, Angel María; Paz, José Antonio; García-Mina, José María; Pozo, María José; López-Ráez, Juan Antonio

    2013-01-01

    Arbuscular mycorrhizal (AM) symbiosis can alleviate salt stress in plants. However the intimate mechanisms involved, as well as the effect of salinity on the production of signalling molecules associated to the host plant-AM fungus interaction remains largely unknown. In the present work, we have investigated the effects of salinity on lettuce plant performance and production of strigolactones, and assessed its influence on mycorrhizal root colonization. Three different salt concentrations were applied to mycorrhizal and non-mycorrhizal plants, and their effects, over time, analyzed. Plant biomass, stomatal conductance, efficiency of photosystem II, as well as ABA content and strigolactone production were assessed. The expression of ABA biosynthesis genes was also analyzed. AM plants showed improved growth rates and a better performance of physiological parameters such as stomatal conductance and efficiency of photosystem II than non-mycorrhizal plants under salt stress since very early stages - 3 weeks - of plant colonization. Moreover, ABA levels were lower in those plants, suggesting that they were less stressed than non-colonized plants. On the other hand, we show that both AM symbiosis and salinity influence strigolactone production, although in a different way in AM and non-AM plants. The results suggest that AM symbiosis alleviates salt stress by altering the hormonal profiles and affecting plant physiology in the host plant. Moreover, a correlation between strigolactone production, ABA content, AM root colonization and salinity level is shown. We propose here that under these unfavourable conditions, plants increase strigolactone production in order to promote symbiosis establishment to cope with salt stress.

  16. Interactions between arbuscular mycorrhizal fungi and soil bacteria.

    PubMed

    Miransari, Mohammad

    2011-02-01

    The soil environment is interesting and complicated. There are so many interactions taking place in the soil, which determine the properties of soil as a medium for the growth and activities of plants and soil microorganisms. The soil fungi, arbuscular mycorrhiza (AM), are in mutual and beneficial symbiosis with most of the terrestrial plants. AM fungi are continuously interactive with a wide range of soil microorganisms including nonbacterial soil microorganisms, plant growth promoting rhizobacteria, mycorrhiza helper bacteria and deleterious bacteria. Their interactions can have important implications in agriculture. There are some interesting interactions between the AM fungi and soil bacteria including the binding of soil bacteria to the fungal spore, the injection of molecules by bacteria into the fungal spore, the production of volatiles by bacteria and the degradation of fungal cellular wall. Such mechanisms can affect the expression of genes in AM fungi and hence their performance and ecosystem productivity. Hence, consideration of such interactive behavior is of significance. In this review, some of the most important findings regarding the interactions between AM fungi and soil bacteria with some new insights for future research are presented.

  17. Arbuscular-mycorrhizal networks inhibit Eucalyptus tetrodonta seedlings in rain forest soil microcosms.

    PubMed

    Janos, David P; Scott, John; Aristizábal, Catalina; Bowman, David M J S

    2013-01-01

    Eucalyptus tetrodonta, a co-dominant tree species of tropical, northern Australian savannas, does not invade adjacent monsoon rain forest unless the forest is burnt intensely. Such facilitation by fire of seedling establishment is known as the "ashbed effect." Because the ashbed effect might involve disruption of common mycorrhizal networks, we hypothesized that in the absence of fire, intact rain forest arbuscular mycorrhizal (AM) networks inhibit E. tetrodonta seedlings. Although arbuscular mycorrhizas predominate in the rain forest, common tree species of the northern Australian savannas (including adult E. tetrodonta) host ectomycorrhizas. To test our hypothesis, we grew E. tetrodonta and Ceiba pentandra (an AM-responsive species used to confirm treatments) separately in microcosms of ambient or methyl-bromide fumigated rain forest soil with or without severing potential mycorrhizal fungus connections to an AM nurse plant, Litsea glutinosa. As expected, C. pentandra formed mycorrhizas in all treatments but had the most root colonization and grew fastest in ambient soil. E. tetrodonta seedlings also formed AM in all treatments, but severing hyphae in fumigated soil produced the least colonization and the best growth. Three of ten E. tetrodonta seedlings in ambient soil with intact network hyphae died. Because foliar chlorosis was symptomatic of iron deficiency, after 130 days we began to fertilize half the E. tetrodonta seedlings in ambient soil with an iron solution. Iron fertilization completely remedied chlorosis and stimulated leaf growth. Our microcosm results suggest that in intact rain forest, common AM networks mediate belowground competition and AM fungi may exacerbate iron deficiency, thereby enhancing resistance to E. tetrodonta invasion. Common AM networks-previously unrecognized as contributors to the ashbed effect-probably help to maintain the rain forest-savanna boundary.

  18. Interactions of Vesicular-Arbuscular Mycorrhizal Fungi, Phosphorus, and Heterodera glycines on Soybean

    PubMed Central

    Tylka, G. L.; Hussey, R. S.; Roncadori, R. W.

    1991-01-01

    Effects of vesicular-arbuscular mycorrhizal (VAM) fungi and soil phosphorus (P) fertility on parasitism of soybean cultivars Bragg and Wright by soybean cyst nematode (SCN) were investigated in field micropiot and greenhouse experiments. VAM fungi increased height of both cultivars and yield of Wright in microplot studies in 1986 and 1987. Conversely, yield of mycorrhizal and nonmycorrhizal plants of both cultivars was suppressed by SCN. Soil population densities of SCN were unaffected by VAM fungi in 1986 but were greater in microplots infested with VAM fungi than in control microplots in 1987. Growth of Wright soybean was stimulated by VAM fungi and suppressed by SCN in greenhouse experiments. The effect of VAM fungi on SCN varied with time. Numbers of SCN in roots and soil were decreased by VAM fungi by as much as 73% at the highest SCN inoculum level through 49 days after planting. Later, however, SCN numbers were usually comparable on mycorrhizal and nonmycorrhizal plants. Soil P fertility generally had no effect on SCN. Results of a split-root experiment indicated that VAM fungal suppression of SCN was not systemic. PMID:19283102

  19. Arbuscular mycorrhizal fungi promote the growth of Ceratocarpus arenarius (Chenopodiaceae) with no enhancement of phosphorus nutrition.

    PubMed

    Zhang, Tao; Shi, Ning; 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.

  20. Reduced germination of Orobanche cumana seeds in the presence of Arbuscular Mycorrhizal fungi or their exudates.

    PubMed

    Louarn, Johann; Carbonne, Francis; Delavault, Philippe; Bécard, Guillaume; Rochange, Soizic

    2012-01-01

    Broomrapes (Orobanche and Phelipanche spp) are parasitic plants responsible for important crop losses, and efficient procedures to control these pests are scarce. Biological control is one of the possible strategies to tackle these pests. Arbuscular Mycorrhizal (AM) fungi are widespread soil microorganisms that live symbiotically with the roots of most plant species, and they have already been tested on sorghum for their ability to reduce infestation by witchweeds, another kind of parasitic plants. In this work AM fungi were evaluated as potential biocontrol agents against Orobanche cumana, a broomrape species that specifically attacks sunflower. When inoculated simultaneously with O. cumana seeds, AM fungi could offer a moderate level of protection against the broomrape. Interestingly, this protection did not only rely on a reduced production of parasitic seed germination stimulants, as was proposed in previous studies. Rather, mycorrhizal root exudates had a negative impact on the germination of O. cumana induced by germination stimulants. A similar effect could be obtained with AM spore exudates, establishing the fungal origin of at least part of the active compounds. Together, our results demonstrate that AM fungi themselves can lead to a reduced rate of parasitic seed germination, in addition to possible effects mediated by the mycorrhizal plant. Combined with the other benefits of AM symbiosis, these effects make AM fungi an attractive option for biological control of O. cumana.

  1. Influence of cadmium stress and arbuscular mycorrhizal fungi on nodule senescence in Cajanus cajan (L.) Millsp.

    PubMed

    Garg, Neera; Bhandari, Purnima

    2012-01-01

    Cadmium (Cd) causes oxidative damage and affects nodulation and nitrogen fixation process of legumes. Arbuscular mycorrhizal (AM) fungi have been demonstrated to alleviate heavy metal stress of plants. The present study was conducted to assess role of AM in alleviating negative effects of Cd on nodule senescence in Cajanus cajan genotypes differing in their metal tolerance. Fifteen day-old plants were subjected to Cd treatments--25 mg and 50 mg Cd per kg dry soil and were grown with and without Glomus mosseae. Cd treatments led to a decline in mycorrhizal infection (MI), nodule number and dry weights which was accompanied by reductions in leghemoglobin content, nitrogenase activity, organic acid contents. Cd supply caused a marked decrease in nitrogen (N), phosphorus (P), and iron (Fe) contents. Conversely, Cd increased membrane permeability, thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2), and Cd contents in nodules. AM inoculations were beneficial in reducing the above mentioned harmful effects of Cd and significantly improved nodule functioning. Activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) increased markedly in nodules of mycorrhizal-stressed plants. The negative effects of Cd were genotype and concentration dependent.

  2. Carbon availability triggers fungal nitrogen uptake and transport in arbuscular mycorrhizal symbiosis.

    PubMed

    Fellbaum, Carl R; Gachomo, Emma W; Beesetty, Yugandhar; Choudhari, Sulbha; Strahan, Gary D; Pfeffer, Philip E; Kiers, E Toby; Bücking, Heike

    2012-02-14

    The arbuscular mycorrhizal (AM) symbiosis, formed between the majority of land plants and ubiquitous soil fungi of the phylum Glomeromycota, is responsible for massive nutrient transfer and global carbon sequestration. AM fungi take up nutrients from the soil and exchange them against photosynthetically fixed carbon (C) from the host. Recent studies have demonstrated that reciprocal reward strategies by plant and fungal partners guarantee a "fair trade" of phosphorus against C between partners [Kiers ET, et al. (2011) Science 333:880-882], but whether a similar reward mechanism also controls nitrogen (N) flux in the AM symbiosis is not known. Using mycorrhizal root organ cultures, we manipulated the C supply to the host and fungus and followed the uptake and transport of N sources in the AM symbiosis, the enzymatic activities of arginase and urease, and fungal gene expression in the extraradical and intraradical mycelium. We found that the C supply of the host plant triggers the uptake and transport of N in the symbiosis, and that the increase in N transport is orchestrated by changes in fungal gene expression. N transport in the symbiosis is stimulated only when the C is delivered by the host across the mycorrhizal interface, not when C is supplied directly to the fungal extraradical mycelium in the form of acetate. These findings support the importance of C flux from the root to the fungus as a key trigger for N uptake and transport and provide insight into the N transport regulation in the AM symbiosis.

  3. Arbuscular mycorrhizal interactions of mycoheterotrophic Thismia are more specialized than in autotrophic plants.

    PubMed

    Gomes, Sofia I F; Aguirre-Gutiérrez, Jesús; Bidartondo, Martin I; Merckx, Vincent S F T

    2017-02-01

    In general, plants and arbuscular mycorrhizal (AM) fungi exchange photosynthetically fixed carbon for soil nutrients, but occasionally nonphotosynthetic plants obtain carbon from AM fungi. The interactions of these mycoheterotrophic plants with AM fungi are suggested to be more specialized than those of green plants, although direct comparisons are lacking. We investigated the mycorrhizal interactions of both green and mycoheterotrophic plants. We used next-generation DNA sequencing to compare the AM communities from roots of five closely related mycoheterotrophic species of Thismia (Thismiaceae), roots of surrounding green plants, and soil, sampled over the entire temperate distribution of Thismia in Australia and New Zealand. We observed that the fungal communities of mycoheterotrophic and green plants are phylogenetically more similar within than between these groups of plants, suggesting a specific association pattern according to plant trophic mode. Moreover, mycoheterotrophic plants follow a more restricted association with their fungal partners in terms of phylogenetic diversity when compared with green plants, targeting more clustered lineages of fungi, independent of geographic origin. Our findings demonstrate that these mycoheterotrophic plants target more narrow lineages of fungi than green plants, despite the larger fungal pool available in the soil, and thus they are more specialized towards mycorrhizal fungi than autotrophic plants.

  4. 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

  5. [Effects of different arbuscular mycorrhizal fungi on Tagetes erecta growth and diesel degradation].

    PubMed

    Geng, Chunnü; Li, Peijun; Chen, Suhua; Zhang, Hairong; Han, Guiyun

    2003-10-01

    The effects of G. mosseae, G. geospora, G. constrictum and bacteria on diesel tolerance of Tagetes erecta were investigated under greenhouse conditions. The results showed that AM fungi could still develop mycorrhizal assosiations with mum when the diesel concentration was 5,000 mg.kg-1. White mum was better than yellow mum in diesel tolerance, with 63.1% total biomass increased. The colonization rate of inoculating AM fungi treatment was 3.5%-29.9% higher than the control. G. mosseae and G. geospora were better strains, their biomass increasing 9.0% and 42.7% than the control, respectively, while the effect of inoculating mixed AM fungi was not obvious. Bacteria inhibited the colonization of arbuscular mycorrhizal fungi on white mum, but promoted the vegetative and reproductive growth of mycorrhizal mum. Among 5 inoculation treatments, treatments of inoculating G. geospora and inoculating mixed AM fungi and bacteria were better, with 16.51% and 14.05% more diesel degradation rate than that of the control, respectively.

  6. Laser microdissection and its application to analyze gene expression in arbuscular mycorrhizal symbiosis.

    PubMed

    Gomez, S Karen; Harrison, Maria J

    2009-05-01

    Phosphorus is essential for plant growth, and in many soils phosphorus availability limits crop production. Most plants in natural ecosystems obtain phosphorus via a symbiotic partnership with arbuscular mycorrhizal (AM) fungi. While the significance of these associations is apparent, their molecular basis is poorly understood. Consequently, the potential to harness the mycorrhizal symbiosis to improve phosphorus nutrition in agriculture is not realized. Transcript profiling has recently been used to investigate gene expression changes that accompany development of the AM symbiosis. While these approaches have enabled the identification of AM-symbiosis-associated genes, they have generally involved the use of RNA from whole mycorrhizal roots. Laser microdissection techniques allow the dissection and capture of individual cells from a tissue. RNA can then be isolated from these samples and cell-type specific gene expression information can be obtained. This technology has been applied to obtain cells from plants and more recently to study plant-microbe interactions. The latter techniques, particularly those developed for root-microbe interactions, are of relevance to plant-parasitic weed research. Here, laser microdissection, its use in plant biology and in particular plant-microbe interactions are discussed. An overview of the AM symbiosis is then provided, with a focus on recent advances in understanding development of the arbuscule-cortical cell interface. Finally, the recent applications of laser microdissection for analyses of AM symbiosis are discussed.

  7. Influence of arbuscular mycorrhizal colonisation on cadmium induced Medicago truncatula root isoflavonoid accumulation.

    PubMed

    Aloui, Achref; Dumas-Gaudot, Eliane; Daher, Zeina; van Tuinen, Diederik; Aschi-Smit, Samira; Morandi, Dominique

    2012-11-01

    Cadmium is a serious environmental pollution threats to the planet. Its accumulation in plants affects many cellular functions, resulting in growth and development inhibition, whose mechanisms are not fully understood. However, some fungi forming arbuscular mycorrhizal symbiosis with the majority of plant species have the capacity to buffer the deleterious effect of this heavy metal. In the present work we investigated the capacity of Rhizophagus irregularis (syn. Glomus irregularis) to alleviate cadmium stress in Medicago truncatula. In spite of a reduction in all mycorrhizal parameters, plants colonized for 21 days by R. irregularis and treated by 2 mg kg⁻¹ cadmium displayed less growth inhibition in comparison to plants grown without cadmium. Cadmium strongly increased the accumulation of some isoflavonoids and their derivates: formononetin, malonylononin, medicarpin 3-O-β-(6'-malonylglucoside), medicarpin and coumestrol. Interestingly, in plants colonized by R. irregularis we noticed a strong reduction of the cadmium-induced accumulation of root isoflavonoids, a part for medicarpin and coumestrol. Moreover, transcripts of chalcone reductase, a protein that we reported previously as being down-regulated in R. irregularis-colonized M. truncatula roots, revealed a similar expression pattern with a strong increase in response to cadmium and a reduced expression in cadmium-treated mycorrhizal roots.

  8. Transcriptional response of Medicago truncatula sulphate transporters to arbuscular mycorrhizal symbiosis with and without sulphur stress.

    PubMed

    Casieri, Leonardo; Gallardo, Karine; Wipf, Daniel

    2012-06-01

    Sulphur is an essential macronutrient for plant growth, development and response to various abiotic and biotic stresses due to its key role in the biosynthesis of many S-containing compounds. Sulphate represents a very small portion of soil S pull and it is the only form that plant roots can uptake and mobilize through H(+)-dependent co-transport processes implying sulphate transporters. Unlike the other organically bound forms of S, sulphate is normally leached from soils due to its solubility in water, thus reducing its availability to plants. Although our knowledge of plant sulphate transporters has been growing significantly in the past decades, little is still known about the effect of the arbuscular mycorrhiza interaction on sulphur uptake. Carbon, nitrogen and sulphur measurements in plant parts and expression analysis of genes encoding putative Medicago sulphate transporters (MtSULTRs) were performed to better understand the beneficial effects of mycorrhizal interaction on Medicago truncatula plants colonized by Glomus intraradices at different sulphate concentrations. Mycorrhization significantly promoted plant growth and sulphur content, suggesting increased sulphate absorption. In silico analyses allowed identifying eight putative MtSULTRs phylogenetically distributed over the four sulphate transporter groups. Some putative MtSULTRs were transcribed differentially in roots and leaves and affected by sulphate concentration, while others were more constitutively transcribed. Mycorrhizal-inducible and -repressed MtSULTRs transcripts were identified allowing to shed light on the role of mycorrhizal interaction in sulphate uptake.

  9. Modularity Reveals the Tendency of Arbuscular Mycorrhizal Fungi To Interact Differently with Generalist and Specialist Plant Species in Gypsum Soils

    PubMed Central

    Torrecillas, Emma; del Mar Alguacil, Maria; Roldán, Antonio; Díaz, Gisela; Montesinos-Navarro, Alicia

    2014-01-01

    Patterns in plant–soil biota interactions could be influenced by the spatial distribution of species due to soil conditions or by the functional traits of species. Gypsum environments usually constitute a mosaic of heterogeneous soils where gypsum and nongypsum soils are imbricated at a local scale. A case study of the interactions of plants with arbuscular mycorrhizal fungi (AMF) in gypsum environments can be illustrative of patterns in biotic interactions. We hypothesized that (i) soil characteristics might affect the AMF community and (ii) there are differences between the AMF communities (modules) associated with plants exclusive to gypsum soils (gypsophytes) and those associated with plants that show facultative behavior on gypsum and/or marly-limestone soils (gypsovags). We used indicator species and network analyses to test for differences between the AMF communities harbored in gypsophyte and gypsovag plants. We recorded 46 operational taxonomic units (OTUs) belonging to nine genera of Glomeromycota. The indicator species analysis showed two OTUs preferentially associating with gypsum soils and three OTUs preferentially associating with marly-limestone soils. Modularity analysis revealed that soil type can be a major factor shaping AMF communities, and some AMF groups showed a tendency to interact differently with plants that had distinct ecological strategies (gypsophytes and gypsovags). Characterization of ecological networks can be a valuable tool for ascertaining the potential influence of above- and below-ground biotic interactions (plant-AMF) on plant community composition. PMID:24973074

  10. Impact of arbuscular mycorrhizal fungal inoculants on subsequent arbuscular mycorrhizal fungi colonization in pot-cultured field pea (Pisum sativum L.).

    PubMed

    Jin, Hongyan; Germida, James J; Walley, Fran L

    2013-01-01

    The use of commercial inoculants containing non-resident arbuscular mycorrhizal fungi (AMF) is an emerging technology in field crop production in Canada. The objective of this study was to assess the impact of AMF inoculants containing either a single species (Glomus irregulare) or mixed species (G. irregulare, Glomus mosseae, and Glomus clarum) on AMF root colonization and consequent plant growth parameters of field pea grown using pot cultures. Field pea was grown in both sterilized and non-sterile (i.e., natural) field-collected soil containing resident AMF and received three inoculation treatments: uninoculated control, G. irregulare only, and a mixture of AMF species of G. irregulare, G. mosseae, and G. clarum. After 42 days, the AMF community assembled in field pea roots was assessed by cloning and sequencing analysis on the LSU-ITS-SSU rDNA gene, together with a microscopic assessment of colonization, biomass production, nutrient uptake, and N(2) fixation. The identity of AMF inoculants had a significant effect on field pea performance. The mixed species AMF inoculant performed better than the single species G. irregulare alone by promoting mycorrhizal colonization, field pea biomass, N and P uptake, and N(2) fixation and did not result in a significant compositional change of the AMF community that subsequently assembled in field pea roots. In contrast, the single species G. irregulare inoculant did not significantly enhance field pea biomass, N and P uptake, and N(2) fixation, although a significant compositional change of the subsequent AMF community was observed. No significant interactions affecting these measurements were detected between the resident AMF and the introduced AMF inoculants. The observation that the mixed species AMF inoculant promoted plant growth parameters without necessarily affecting the subsequent AMF community may have important implications regarding the use of non-resident AMF inoculants in agricultural production.

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

    PubMed Central

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

    1983-01-01

    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 μg [low P] or 30 μg [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 μ/g soil) alters root-knot nematode infection of tomato more than G. mosseae and G. margarita. PMID:19295826

  12. Enhanced production of steviol glycosides in mycorrhizal plants: a concerted effect of arbuscular mycorrhizal symbiosis on transcription of biosynthetic genes.

    PubMed

    Mandal, Shantanu; Upadhyay, Shivangi; Singh, Ved Pal; Kapoor, Rupam

    2015-04-01

    Stevia rebaudiana (Bertoni) produces steviol glycosides (SGs)--stevioside (stev) and rebaudioside-A (reb-A) that are valued as low calorie sweeteners. Inoculation with arbuscular mycorrhizal fungi (AMF) augments SGs production, though the effect of this interaction on SGs biosynthesis has not been studied at molecular level. In this study transcription profiles of eleven key genes grouped under three stages of the SGs biosynthesis pathway were compared. The transcript analysis showed upregulation of genes encoding 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway enzymes viz.,1-deoxy-D-xylulose 5-phospate synthase (DXS), 1-deoxy-D-xylulose 5-phospate reductoisomerase (DXR) and 2-C-methyl-D-erytrithol 2,4-cyclodiphosphate synthase (MDS) in mycorrhizal (M) plants. Zn and Mn are imperative for the expression of MDS and their enhanced uptake in M plants could be responsible for the increased transcription of MDS. Furthermore, in the second stage of SGs biosynthesis pathway, mycorrhization enhanced the transcription of copalyl diphosphate synthase (CPPS) and kaurenoic acid hydroxylase (KAH). Their expression is decisive for SGs biosynthesis as CPPS regulates flow of metabolites towards synthesis of kaurenoid precursors and KAH directs these towards steviol synthesis instead of gibberellins. In the third stage glucosylation of steviol to reb-A by four specific uridine diphosphate (UDP)-dependent glycosyltransferases (UGTs) occurs. While higher transcription of all the three characterized UGTs in M plants explains augmented production of SGs; higher transcript levels of UGT76G1, specifically improved reb-A to stev ratio implying increased sweetness. The work signifies that AM symbiosis upregulates the transcription of all eleven SGs biosynthesis genes as a result of improved nutrition and enhanced sugar concentration due to increased photosynthesis in M plants.

  13. New insights into the signaling pathways controlling defense gene expression in rice roots during the arbuscular mycorrhizal symbiosis.

    PubMed

    Campos-Soriano, Lidia; Segundo, Blanca San

    2011-04-01

    Mycorrhizal fungi form a mutualistic relationship with the roots of most plant species. This association provides the arbuscular mycorrhizal (AM) fungus with sugars while the fungus improves the uptake of water and mineral nutrients in the host plant. Moreover, the induction of defence gene expression in mycorrhizal roots has been described. While salicylic acid (SA)-regulated Pathogenesis-Related (PR) proteins accumulate in rice roots colonized by the AM fungus G. intraradices, the SA content is not significantly altered in the mycorrhizal roots. Sugars, in addition to being a source of carbon for the fungus, might act as signals for the control of defence gene expression. We hypothesize that increased demands for sugars by the fungus might be responsible for the activation of the host defence responses which will then contribute to the stabilization of root colonization by the AM fungus. An excessive root colonization might change a mutualistic association into a parasitic association.

  14. Using molecular biology to study mycorrhizal fungal community ecology: Limits and perspectives.

    PubMed

    Chagnon, Pierre-Luc; Bainard, Luke D

    2015-01-01

    Molecular tools have progressively replaced morphological approaches to characterize microbial communities in nature. Arbuscular mycorrhizal (AM) fungi are no exception to this rule. Yet, one challenge posed by these symbionts is that they colonize simultaneously both plant roots and soil, which complicates their detection and quantification. In most studies conducted to date, AM fungal communities have been characterized from roots only, soil only or spores only. Here, we discuss the pitfalls associated to drawing ecological inferences using such datasets. We also conclude by arguing that molecular biology will contribute most to advance knowledge in AM fungal ecology if it is integrated into broader perspectives taking into account the natural history of these organisms. This calls for a better merging of molecular and morphological approaches, and the establishment of intensive, long-term research programs.

  15. Disclosing arbuscular mycorrhizal fungal biodiversity in soil through a land-use gradient using a pyrosequencing approach.

    PubMed

    Lumini, Erica; Orgiazzi, Alberto; Borriello, Roberto; Bonfante, Paola; Bianciotto, Valeria

    2010-08-01

    The biodiversity of arbuscular mycorrhizal fungi (AMF) communities present in five Sardinian soils (Italy) subjected to different land-use (tilled vineyard, covered vineyard, pasture, managed meadow and cork-oak formation) was analysed using a pyrosequencing-based approach for the first time. Two regions of the 18S ribosomal RNA gene were considered as molecular target. The pyrosequencing produced a total of 10924 sequences: 6799 from the first and 4125 from the second target region. Among these sequences, 3189 and 1003 were selected to generate operational taxonomic units (OTUs) and to evaluate the AMF community richness and similarity: 117 (37 of which were singletons) and 28 (nine of which were singletons) unique AMF OTUs were detected respectively. Within the Glomeromycota OTUs, those belonging to the Glomerales order were dominant in all the soils. Diversisporales OTUs were always detected, even though less frequently, while Archaeosporales and Paraglomerales OTUs were exclusive of the pasture soil. Eleven OTUs were shared by all the soils, but each of the five AMF communities showed particular features, suggesting a meaningful dissimilarity among the Glomeromycota populations. The environments with low inputs (pasture and covered vineyard) showed a higher AMF biodiversity than those subjected to human input (managed meadow and tilled vineyard). A reduction in AMF was found in the cork-oak formation because other mycorrhizal fungal species, more likely associated to trees and shrubs, were detected. These findings reinforce the view that AMF biodiversity is influenced by both human input and ecological traits, illustrating a gradient of AMF communities which mirror the land-use gradient. The high number of sequences obtained by the pyrosequencing strategy has provided detailed information on the soil AMF assemblages, thus offering a source of light to shine on this crucial soil microbial group.

  16. [Systematic classification and community research techniques of arbuscular mycorrhizal fungi: a review].

    PubMed

    Liu, Yong-Jun; Feng, Hu-Yuan

    2010-06-01

    Arbuscular mycorrhizal fungi (AMF) are an important component of natural ecosystem, being able to form symbiont with plant roots. The traditional AMF classification is mainly based on the morphological identification of soil asexual spores, which has some limitations in the taxonomy of AMF. Advanced molecular techniques make the classification of AMF more accurate and scientific, and can improve the taxonomy of AMF established on the basis of morphological identification. The community research of AMF is mainly based on species classification, and has two kinds of investigation methods, i. e., spores morphological identification and molecular analysis. This paper reviewed the research progress in the systematic classification and community research techniques of AMF, with the focus on the molecular techniques in community analysis of AMF. It was considered that using morphological and molecular methods together would redound to the accurate investigation of AMF community, and also, facilitate the improvement of AMF taxonomy.

  17. Positive Gene Regulation by a Natural Protective miRNA Enables Arbuscular Mycorrhizal Symbiosis.

    PubMed

    Couzigou, Jean-Malo; Lauressergues, Dominique; André, Olivier; Gutjahr, Caroline; Guillotin, Bruno; Bécard, Guillaume; Combier, Jean-Philippe

    2017-01-11

    Arbuscular mycorrhizal (AM) symbiosis associates most plants with fungi of the phylum Glomeromycota. The fungus penetrates into roots and forms within cortical cell branched structures called arbuscules for nutrient exchange. We discovered that miR171b has a mismatched cleavage site and is unable to downregulate the miR171 family target gene, LOM1 (LOST MERISTEMS 1). This mismatched cleavage site is conserved among plants that establish AM symbiosis, but not in non-mycotrophic plants. Unlike other members of the miR171 family, miR171b stimulates AM symbiosis and is expressed specifically in root cells that contain arbuscules. MiR171b protects LOM1 from negative regulation by other miR171 family members. These findings uncover a unique mechanism of positive post-transcriptional regulation of gene expression by miRNAs and demonstrate its relevance for the establishment of AM symbiosis.

  18. Community Structures of Arbuscular Mycorrhizal Fungi in Soils and Plant Roots Inhabiting Abandoned Mines of Korea

    PubMed Central

    Park, Hyeok; Lee, Eun-Hwa; Ka, Kang-Hyeon

    2016-01-01

    In this study, we collected rhizosphere soils and root samples from a post-mining area and a natural forest area in Jecheon, Korea. We extracted spores of arbuscular mycorrhizal fungi (AMF) from rhizospheres, and then examined the sequences of 18S rDNA genes of the AMF from the collected roots of plants. We compared the AMF communities in the post-mining area and the natural forest area by sequence analysis of the AMF spores from soils and of the AMF clones from roots. Consequently, we confirmed that the structure of AMF communities varied between the post-mining area and the natural forest area and showed significant relationship with heavy metal contents in soils. These results suggest that heavy metal contamination by mining activity significantly affects the AMF community structure. PMID:28154485

  19. Arbuscular mycorrhizal fungal community composition associated with Juniperus brevifolia in native Azorean forest

    NASA Astrophysics Data System (ADS)

    Melo, Catarina Drumonde; Luna, Sara; Krüger, Claudia; Walker, Christopher; Mendonça, Duarte; Fonseca, Henrique M. A. C.; Jaizme-Vega, Maria; da Câmara Machado, Artur

    2017-02-01

    The communities of glomeromycotan fungi (arbuscular mycorrhizal fungi, AMF) under native Juniperus brevifolia forest from two Azorean islands, Terceira and São Miguel, were compared, mainly by spore morphology, and when possible, by molecular analysis. Thirty-nine morphotypes were detected from 12 genera. Glomeromycotan fungal richness was similar in Terceira and São Miguel, but significantly different among the four fragments of native forest. Spore diversity and community composition differed significantly between the two islands. The less degraded island, Terceira, showed 10 exclusive morphotypes including more rare types, whereas the more disturbed forest on São Miguel showed 13 morphs, mostly of common types. Forests from Terceira were dominated by Acaulosporaceae and Glomeraceae. Whereas members of Acaulosporaceae, Glomeraceae and Ambisporaceae were most frequent and abundant in those from São Miguel. Spore abundance was greatest on Terceira, and correlated with soil chemical properties (pH), average monthly temperature and relative humidity.

  20. Improvement by soil yeasts of arbuscular mycorrhizal symbiosis of soybean (Glycine max) colonized by Glomus mosseae.

    PubMed

    Sampedro, I; Aranda, E; Scervino, J M; Fracchia, S; García-Romera, I; Ocampo, J A; Godeas, A

    2004-08-01

    The effects of the soil yeasts Rhodotorula mucilaginosa, Cryptococcus laurentii and Saccharomyces kunashirensis on the arbuscular mycorrhizal (AM) fungus Glomus mosseae (BEG 12) was studied in vitro and in greenhouse trials. The presence of yeasts or their soluble and volatile exudates stimulated the percentage spore germination and hyphal growth of G. mosseae. Percentage root length colonized by G. mosseae and plant dry matter of soybean (Glycine maxL. Merill) were increased only when the soil yeasts were inoculated prior to the AM fungus. Higher beneficial effects on AM colonization and plant dry matter were found when the soil yeasts were inoculated as an aqueous solution rather than as a thin agar slice. Although soluble and volatile exudates of yeasts benefited the AM symbiosis, their modes of action were different.

  1. Evolutionary conservation of a phosphate transporter in the arbuscular mycorrhizal symbiosis

    PubMed Central

    Karandashov, Vladimir; Nagy, Réka; Wegmüller, Sarah; Amrhein, Nikolaus; Bucher, Marcel

    2004-01-01

    Arbuscular mycorrhizae are ancient symbioses that are thought to have originated >400 million years ago in the roots of plants, pioneering the colonization of terrestrial habitats. In these associations, a key process is the transfer of phosphorus as inorganic phosphate to the host plant across the fungus–plant interface. Mycorrhiza-specific phosphate transporter genes and their regulation are conserved in phylogenetically distant plant species, and they are activated selectively by fungal species from the phylum Glomeromycota. The potato phosphate transporter gene StPT3 is expressed in a temporally defined manner in root cells harboring various mycorrhizal structures, including thick-coiled hyphae. The results highlight the role of different symbiotic structures in phosphorus transfer, and they indicate that cell–cell contact between the symbiotic partners is required to induce phosphate transport. PMID:15075387

  2. Community Structures of Arbuscular Mycorrhizal Fungi in Soils and Plant Roots Inhabiting Abandoned Mines of Korea.

    PubMed

    Park, Hyeok; Lee, Eun-Hwa; Ka, Kang-Hyeon; Eom, Ahn-Heum

    2016-12-01

    In this study, we collected rhizosphere soils and root samples from a post-mining area and a natural forest area in Jecheon, Korea. We extracted spores of arbuscular mycorrhizal fungi (AMF) from rhizospheres, and then examined the sequences of 18S rDNA genes of the AMF from the collected roots of plants. We compared the AMF communities in the post-mining area and the natural forest area by sequence analysis of the AMF spores from soils and of the AMF clones from roots. Consequently, we confirmed that the structure of AMF communities varied between the post-mining area and the natural forest area and showed significant relationship with heavy metal contents in soils. These results suggest that heavy metal contamination by mining activity significantly affects the AMF community structure.

  3. Dynamics of arbuscular mycorrhizal symbiosis in heavy metal phytoremediation: meta-analytical and conceptual perspectives.

    PubMed

    Audet, Patrick; Charest, Christiane

    2007-06-01

    To estimate dynamics of arbuscular mycorrhizal (AM) symbiosis in heavy metal (HM) phytoremediation, we conducted a literature survey and correlated HM uptake and relative plant growth parameters from published data. After estimating AM feedback responses for these parameters at low and high soil-HM concentration intervals, we determined that the roles of AM symbiosis are characterized by (1) an increased HM phytoextraction via mycorrhizospheric 'Enhanced Uptake' at low soil-HM concentrations, and (2) a reduced HM bioavailability via AM fungal 'Metal-Binding' processes at high soil-HM levels, hence resulting in increased plant biomass and enhanced plant tolerance through HM stress-avoidance. We present two conceptual models which illustrate the important compromise between plant growth, plant HM uptake and HM tolerance, and further emphasize the importance of AM symbiosis in buffering the soil environment for plants under such stress conditions.

  4. Solanum nigrum grown in contaminated soil: effect of arbuscular mycorrhizal fungi on zinc accumulation and histolocalisation.

    PubMed

    Marques, Ana P G C; Oliveira, Rui S; Samardjieva, Kalina A; Pissarra, José; Rangel, António O S S; Castro, Paula M L

    2007-02-01

    Zn tissue accumulation in Solanum nigrum grown in a non-contaminated and a naturally contaminated Zn matrix and the effect of inoculation with different arbuscular mycorrhizal fungi (AMF) on metal uptake were assessed. S. nigrum grown in the contaminated soil always presented higher Zn accumulation in the tissues, accumulating up to 1622 mg Zn kg(-1). The presence of both Glomus claroideum and Glomus intraradices enhanced the uptake and accumulation of Zn by S. nigrum (up to 83 and 49% higher Zn accumulation, respectively). The main deposits of the metal were found in the intercellular spaces and in the cell walls of the root tissues, as revealed by autometallography, with the inoculation with different AMF species causing no differences in the location of Zn accumulation. These findings indicate that S. nigrum inoculated with selected heavy metal tolerant AMF presents extracting and accumulating capacities, constituting a potentially suitable remediation method for Zn polluted soils.

  5. Molecular diversity of arbuscular mycorrhizal fungi in relation to soil chemical properties and heavy metal contamination.

    PubMed

    Zarei, Mehdi; Hempel, Stefan; Wubet, Tesfaye; Schäfer, Tina; Savaghebi, Gholamreza; Jouzani, Gholamreza Salehi; Nekouei, Mojtaba Khayam; Buscot, François

    2010-08-01

    Abundance and diversity of arbuscular mycorrhizal fungi (AMF) associated with dominant plant species were studied along a transect from highly lead (Pb) and zinc (Zn) polluted to non-polluted soil at the Anguran open pit mine in Iran. Using an established primer set for AMF in the internal transcribed spacer (ITS) region of rDNA, nine different AMF sequence types were distinguished after phylogenetic analyses, showing remarkable differences in their distribution patterns along the transect. With decreasing Pb and Zn concentration, the number of AMF sequence types increased, however one sequence type was only found in the highly contaminated area. Multivariate statistical analysis revealed that further factors than HM soil concentration affect the AMF community at contaminated sites. Specifically, the soils' calcium carbonate equivalent and available P proved to be of importance, which illustrates that field studies on AMF distribution should also consider important environmental factors and their possible interactions.

  6. Arbuscular mycorrhizal wheat inoculation promotes alkane and polycyclic aromatic hydrocarbon biodegradation: Microcosm experiment on aged-contaminated soil.

    PubMed

    Ingrid, Lenoir; Lounès-Hadj Sahraoui, Anissa; Frédéric, Laruelle; Yolande, Dalpé; Joël, Fontaine

    2016-06-01

    Very few studies reported the potential of arbuscular mycorrhizal symbiosis to dissipate hydrocarbons in aged polluted soils. The present work aims to study the efficiency of arbuscular mycorrhizal colonized wheat plants in the dissipation of alkanes and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that the inoculation of wheat with Rhizophagus irregularis allowed a better dissipation of PAHs and alkanes after 16 weeks of culture by comparison to non-inoculated condition. These dissipations observed in the inoculated soil resulted from several processes: (i) a light adsorption on roots (0.5% for PAHs), (ii) a bioaccumulation in roots (5.7% for PAHs and 6.6% for alkanes), (iii) a transfer in shoots (0.4 for PAHs and 0.5% for alkanes) and mainly a biodegradation. Whereas PAHs and alkanes degradation rates were respectively estimated to 12 and 47% with non-inoculated wheat, their degradation rates reached 18 and 48% with inoculated wheat. The mycorrhizal inoculation induced an increase of Gram-positive and Gram-negative bacteria by 56 and 37% compared to the non-inoculated wheat. Moreover, an increase of peroxidase activity was assessed in mycorrhizal roots. Taken together, our findings suggested that mycorrhization led to a better hydrocarbon biodegradation in the aged-contaminated soil thanks to a stimulation of telluric bacteria and hydrocarbon metabolization in mycorrhizal roots.

  7. Role of Arbuscular Mycorrhizal Fungi in Phytoremediation of Soil Rhizosphere Spiked with Poly Aromatic Hydrocarbons

    PubMed Central

    2005-01-01

    Results from an innovative approach to improve remediation in the rhizosphere by encouraging healthy plant growth and thus enhancing microbial activity are reported. The effect of arbuscular mycorrhizal fungi (Am) on remediation efficacy of wheat, mungbean and eggplant grown in soil spiked with polyaromatic hydrocarbons (PAH) was assessed in a pot experiment. The results of this study showed that Am inoculation enhanced dissipation amount of PAHs in planted soil, plant uptake PAHs, dissipation amount of PAHs in planted versus unplanted spiked soil and loss of PAHs by the plant-promoted biodegradation. A number of parameters were monitored including plant shoot and root dry weight, plant tissue water content, plant chlorophyll, root lipid content, oxido-reductase enzyme activities in plant and soil rhizosphere and total microbial count in the rhizospheric soil. The observed physiological data indicate that plant growth and tolerance increased with Am, but reduced by PAH. This was reflected by levels of mycorrhizal root colonization which were higher for mungbean, moderate for wheat and low for eggplant. Levels of Am colonization increased on mungbean > wheat > eggplant. This is consistent with the efficacy of plant in dissipation of PAHs in spiked soil. Highly significant positive correlations were shown between of arbuscular formation in root segments (A)) and plant water content, root lipids, peroxidase, catalase polyphenol oxidase and total microbial count in soil rhizosphere as well as PAH dissipation in spiked soil. As consequence of the treatment with Am, the plants provide a greater sink for the contaminants since they are better able to survive and grow. PMID:24049473

  8. Fresh perspectives on the roles of arbuscular mycorrhizal fungi in plant nutrition and growth.

    PubMed

    Smith, Sally E; Smith, F Andrew

    2012-01-01

    Recent research on arbuscular mycorrhizas has demonstrated that AM fungi play a significant role in plant phosphorus (P) uptake, regardless of whether the plant responds positively to colonization in terms of growth or P content. Here we focus particularly on implications of this finding for consideration of the balance between organic carbon (C) use by the fungi and P delivery (i.e. the C-P trade between the symbionts). Positive growth responses to arbuscular mycorrhizal (AM) colonization are attributed frequently to increased P uptake via the fungus, which results in relief of P deficiency and increased growth. Zero AM responses, compared with non-mycorrhizal (NM) plants, have conventionally been attributed to failure of the fungi to deliver P to the plants. Negative responses, combined with excessive C use, have been attributed to this failure. The fungi were viewed as parasites. Demonstration that the AM pathway of P uptake operates in such plants indicates that direct P uptake by the roots is reduced and that the fungi are not parasites but mutualists because they deliver P as well as using C. We suggest that poor plant growth is the result of P deficiency because AM fungi lower the amount of P taken up directly by roots but the AM uptake of P does compensate for the reduction. The implications of interplay between direct root uptake and AM fungal uptake of P also include increased tolerance of AM plants to toxins such as arsenate and increased success when competing with NM plants. Finally we discuss the new information on C-P trade in the context of control of the symbiosis by the fungus or the plant, including new information (from NM plants) on sugar transport and on the role of sucrose in the signaling network involved in responses of plants to P deprivation.

  9. The arbuscular mycorrhizal fungus Glomus mosseae induces growth and metal accumulation changes in Cannabis sativa L.

    PubMed

    Citterio, Sandra; Prato, Nadia; Fumagalli, Pietro; Aina, Roberta; Massa, Nadia; Santagostino, Angela; Sgorbati, Sergio; Berta, Graziella

    2005-03-01

    The effect of arbuscular mycorrhiza on heavy metal uptake and translocation was investigated in Cannabis sativa. Hemp was grown in the presence and absence of 100 microg g-1 Cd and Ni and 300 microg g-1 Cr(VI), and inoculated or not with the arbuscular mycorrhizal fungus Glomus mosseae. In our experimental condition, hemp growth was reduced in inoculated plants and the reduction was related to the degree of mycorrhization. The percentage of mycorrhizal colonisation was 42% and 9% in plants grown in non-contaminated and contaminated soil, suggesting a significant negative effect of high metal concentrations on plant infection by G. mosseae. Soil pH, metal bioavailability and plant metal uptake were not influenced by mycorrhization. The organ metal concentrations were not statistically different between inoculated and non-inoculated plants, apart from Ni which concentration was significantly higher in stem and leaf of inoculated plants grown in contaminated soil. The distribution of absorbed metals inside plant was related to the soil heavy metal concentrations: in plant grown in non-contaminated soil the greater part of absorbed Cr and Ni was found in shoots and no significant difference was determined between inoculated and non-inoculated plants. On the contrary, plants grown in artificially contaminated soil accumulated most metal in root organ. In this soil, mycorrhization significantly enhanced the translocation of all the three metals from root to shoot. The possibility to increase metal accumulation in shoot is very interesting for phytoextraction purpose, since most high producing biomass plants, such as non-mycorrhized hemp, retain most heavy metals in roots, limiting their application.

  10. Complementarity in nutrient foraging strategies of absorptive fine roots and arbuscular mycorrhizal fungi across 14 coexisting subtropical tree species.

    PubMed

    Liu, Bitao; Li, Hongbo; Zhu, Biao; Koide, Roger T; Eissenstat, David M; Guo, Dali

    2015-10-01

    In most cases, both roots and mycorrhizal fungi are needed for plant nutrient foraging. Frequently, the colonization of roots by arbuscular mycorrhizal (AM) fungi seems to be greater in species with thick and sparsely branched roots than in species with thin and densely branched roots. Yet, whether a complementarity exists between roots and mycorrhizal fungi across these two types of root system remains unclear. We measured traits related to nutrient foraging (root morphology, architecture and proliferation, AM colonization and extramatrical hyphal length) across 14 coexisting AM subtropical tree species following root pruning and nutrient addition treatments. After root pruning, species with thinner roots showed more root growth, but lower mycorrhizal colonization, than species with thicker roots. Under multi-nutrient (NPK) addition, root growth increased, but mycorrhizal colonization decreased significantly, whereas no significant changes were found under nitrogen or phosphate additions. Moreover, root length proliferation was mainly achieved by altering root architecture, but not root morphology. Thin-root species seem to forage nutrients mainly via roots, whereas thick-root species rely more on mycorrhizal fungi. In addition, the reliance on mycorrhizal fungi was reduced by nutrient additions across all species. These findings highlight complementary strategies for nutrient foraging across coexisting species with contrasting root traits.

  11. Diversity and spatial structure of belowground plant-fungal symbiosis in a mixed subtropical forest of ectomycorrhizal and arbuscular mycorrhizal plants.

    PubMed

    Toju, Hirokazu; Sato, Hirotoshi; Tanabe, Akifumi S

    2014-01-01

    Plant-mycorrhizal fungal interactions are ubiquitous in forest ecosystems. While ectomycorrhizal plants and their fungi generally dominate temperate forests, arbuscular mycorrhizal symbiosis is common in the tropics. In subtropical regions, however, ectomycorrhizal and arbuscular mycorrhizal plants co-occur at comparable abundances in single forests, presumably generating complex community structures of root-associated fungi. To reveal root-associated fungal community structure in a mixed forest of ectomycorrhizal and arbuscular mycorrhizal plants, we conducted a massively-parallel pyrosequencing analysis, targeting fungi in the roots of 36 plant species that co-occur in a subtropical forest. In total, 580 fungal operational taxonomic units were detected, of which 132 and 58 were probably ectomycorrhizal and arbuscular mycorrhizal, respectively. As expected, the composition of fungal symbionts differed between fagaceous (ectomycorrhizal) and non-fagaceous (possibly arbuscular mycorrhizal) plants. However, non-fagaceous plants were associated with not only arbuscular mycorrhizal fungi but also several clades of ectomycorrhizal (e.g., Russula) and root-endophytic ascomycete fungi. Many of the ectomycorrhizal and root-endophytic fungi were detected from both fagaceous and non-fagaceous plants in the community. Interestingly, ectomycorrhizal and arbuscular mycorrhizal fungi were concurrently detected from tiny root fragments of non-fagaceous plants. The plant-fungal associations in the forest were spatially structured, and non-fagaceous plant roots hosted ectomycorrhizal fungi more often in the proximity of ectomycorrhizal plant roots. Overall, this study suggests that belowground plant-fungal symbiosis in subtropical forests is complex in that it includes "non-typical" plant-fungal combinations (e.g., ectomycorrhizal fungi on possibly arbuscular mycorrhizal plants) that do not fall within the conventional classification of mycorrhizal symbioses, and in that

  12. Diversity of arbuscular mycorrhizal fungi in soil from the Pampa Ondulada, Argentina, assessed by pyrosequencing and morphological techniques.

    PubMed

    Colombo, R P; Fernández Bidondo, L; Silvani, V A; Carbonetto, M B; Rascovan, N; Bompadre, M J; Pérgola, M; Cuenca, G; Godeas, A M

    2014-12-01

    The aim of this study was to assess the effects of agronomic practices on the arbuscular mycorrhizal (AM) fungal community in soils from the Pampa Ondulada region (Argentina), and to compare conclusions reached when using pyrosequencing or a morphological approach. The AM fungal diversity of 3 agricultural exploitations located in the Pampa Ondulada region (Argentina) was assessed by using 454 amplicon pyrosequencing and morphological (based on spore traits) approaches. Two kinds of soil managements are found in these sites: agronomic and non-agronomic. A total of 188 molecular operational taxonomic units and 29 morphological species of AM fungi were identified. No effect of soil management on AM richness was detected. AM fungal communities were more diverse and equitable in the absence of agronomic management. In contrast, the results on β-diversity varied according to the methodology used. We concluded that agronomic management of soil has a negative effect on AM fungal community biodiversity in the Pampa Ondulada region. We also conclude that both methodologies complement each other in the study of AM fungal ecology. This study greatly improved the knowledge about AM fungi in South America where the molecular diversity of AM fungi was practically unknown.

  13. Cooperation through Competition-Dynamics and Microeconomics of a Minimal Nutrient Trade System in Arbuscular Mycorrhizal Symbiosis.

    PubMed

    Schott, Stephan; Valdebenito, Braulio; Bustos, Daniel; Gomez-Porras, Judith L; Sharma, Tripti; Dreyer, Ingo

    2016-01-01

    In arbuscular mycorrhizal (AM) symbiosis, fungi and plants exchange nutrients (sugars and phosphate, for instance) for reciprocal benefit. Until now it is not clear how this nutrient exchange system works. Here, we used computational cell biology to simulate the dynamics of a network of proton pumps and proton-coupled transporters that are upregulated during AM formation. We show that this minimal network is sufficient to describe accurately and realistically the nutrient trade system. By applying basic principles of microeconomics, we link the biophysics of transmembrane nutrient transport with the ecology of organismic interactions and straightforwardly explain macroscopic scenarios of the relations between plant and AM fungus. This computational cell biology study allows drawing far reaching hypotheses about the mechanism and the regulation of nutrient exchange and proposes that the "cooperation" between plant and fungus can be in fact the result of a competition between both for the same resources in the tiny periarbuscular space. The minimal model presented here may serve as benchmark to evaluate in future the performance of more complex models of AM nutrient exchange. As a first step toward this goal, we included SWEET sugar transporters in the model and show that their co-occurrence with proton-coupled sugar transporters results in a futile carbon cycle at the plant plasma membrane proposing that two different pathways for the same substrate should not be active at the same time.

  14. Cooperation through Competition—Dynamics and Microeconomics of a Minimal Nutrient Trade System in Arbuscular Mycorrhizal Symbiosis

    PubMed Central

    Schott, Stephan; Valdebenito, Braulio; Bustos, Daniel; Gomez-Porras, Judith L.; Sharma, Tripti; Dreyer, Ingo

    2016-01-01

    In arbuscular mycorrhizal (AM) symbiosis, fungi and plants exchange nutrients (sugars and phosphate, for instance) for reciprocal benefit. Until now it is not clear how this nutrient exchange system works. Here, we used computational cell biology to simulate the dynamics of a network of proton pumps and proton-coupled transporters that are upregulated during AM formation. We show that this minimal network is sufficient to describe accurately and realistically the nutrient trade system. By applying basic principles of microeconomics, we link the biophysics of transmembrane nutrient transport with the ecology of organismic interactions and straightforwardly explain macroscopic scenarios of the relations between plant and AM fungus. This computational cell biology study allows drawing far reaching hypotheses about the mechanism and the regulation of nutrient exchange and proposes that the “cooperation” between plant and fungus can be in fact the result of a competition between both for the same resources in the tiny periarbuscular space. The minimal model presented here may serve as benchmark to evaluate in future the performance of more complex models of AM nutrient exchange. As a first step toward this goal, we included SWEET sugar transporters in the model and show that their co-occurrence with proton-coupled sugar transporters results in a futile carbon cycle at the plant plasma membrane proposing that two different pathways for the same substrate should not be active at the same time. PMID:27446142

  15. Symbiotic interaction of endophytic bacteria with arbuscular mycorrhizal fungi and its antagonistic effect on Ganoderma boninense.

    PubMed

    Sundram, Shamala; Meon, Sariah; Seman, Idris Abu; Othman, Radziah

    2011-08-01

    Endophytic bacteria (Pseudomonas aeruginosa UPMP3 and Burkholderia cepacia UMPB3), isolated from within roots of oil palm (Elaeis guineensis Jacq.) were tested for their presymbiotic effects on two arbuscular mcorrhizal fungi, Glomus intraradices UT126 and Glomus clarum BR152B). These endophytic bacteria were also tested for antagonistic effects on Ganoderma boninense PER 71, a white wood rot fungal pathogen that causes a serious disease in oil palm. Spore germination and hyphal length of each arbuscular mycorrhizal fungal (AMF) pairing with endophytic bacteria was found to be significantly higher than spores plated in the absence of bacteria. Scanning electron microscopy (SEM) showed that the endophytic bacteria were scattered, resting or embedded on the surface hyaline layer or on the degraded walls of AMF spores, possibly feeding on the outer hyaline spore wall. The antagonistic effect of the endophytic bacteria was expressed as severe morphological abnormalities in the hyphal structures of G. boninense PER 71. The effects of the endophytic bacteria on G. boninense PER 71 hyphal structures were observed clearly under SEM. Severe inter-twisting, distortion, lysis and shriveling of the hyphal structures were observed. This study found that the effect of endophytic bacteria on G. intraradices UT126 and G. clarum BR152B resembled that of a mycorrhiza helper bacteria (MHB) association because the association significantly promoted AMF spore germination and hyphal length. However, the endophytic bacteria were extremely damaging to G. boninense PER 71.

  16. [Metabolism and interaction of C and N in the arbuscular mycorrhizal symbiosis].

    PubMed

    Li, Yuan-Jing; Liu, Zhi-Lei; He, Xing-Yuan; Tian, Chun-Jie

    2014-03-01

    The arbuscular mycorrhiza (AM) is the symbiont formed by the host plant and the arbuscular mycorrhizal fungi (AMF). The transfer and metabolism of C and N in the symbiosis plays an important role in keeping nutrient balance and resource reallocation between the host plant and the fungi. The carbohydrates produced by plant photosynthesis are transferred to the fungi, where they are metabolized as materials and energy used for fungal spore germination, mycelium growth and uptake of nitrogen and other nutrients. At the same time, N is transferred and reallocated from the fungi to the host plant, where the final released ammonium is used for plant growth. Accordingly, we reviewed the current progress in C and N transfer and metabolism in the AM symbiosis, and the crosstalk between them as well as some key issues to elucidate the mechanism of the interaction between C and N transport in the symbiosis, so as to provide the theory foundation for the application of AM in sustainable agriculture and ecosystem.

  17. Insights on the Impact of Arbuscular Mycorrhizal Symbiosis on Tomato Tolerance to Water Stress1[OPEN

    PubMed Central

    Siciliano, Ilenia

    2016-01-01

    Arbuscular mycorrhizal (AM) fungi, which form symbioses with the roots of the most important crop species, are usually considered biofertilizers, whose exploitation could represent a promising avenue for the development in the future of a more sustainable next-generation agriculture. The best understood function in symbiosis is an improvement in plant mineral nutrient acquisition, as exchange for carbon compounds derived from the photosynthetic process: this can enhance host growth and tolerance to environmental stresses, such as water stress (WS). However, physiological and molecular mechanisms occurring in arbuscular mycorrhiza-colonized plants and directly involved in the mitigation of WS effects need to be further investigated. The main goal of this work is to verify the potential impact of AM symbiosis on the plant response to WS. To this aim, the effect of two AM fungi (Funneliformis mosseae and Rhizophagus intraradices) on tomato (Solanum lycopersicum) under the WS condition was studied. A combined approach, involving ecophysiological, morphometric, biochemical, and molecular analyses, has been used to highlight the mechanisms involved in plant response to WS during AM symbiosis. Gene expression analyses focused on a set of target genes putatively involved in the plant response to drought, and in parallel, we considered the expression changes induced by the imposed stress on a group of fungal genes playing a key role in the water-transport process. Taken together, the results show that AM symbiosis positively affects the tolerance to WS in tomato, with a different plant response depending on the AM fungi species involved. PMID:27208301

  18. Seasonal Dynamics of Arbuscular Mycorrhizal Fungal Communities in Roots in a Seminatural Grassland▿ †

    PubMed Central

    Santos-González, Juan C.; Finlay, Roger D.; Tehler, Anders

    2007-01-01

    Symbiotic arbuscular mycorrhizal fungi (AMF) have been shown to influence both the diversity and productivity of grassland plant communities. These effects have been postulated to depend on the differential effects of individual mycorrhizal taxa on different plant species; however, so far there are few detailed studies of the dynamics of AMF colonization of different plant species. In this study, we characterized the communities of AMF colonizing the roots of two plant species, Prunella vulgaris and Antennaria dioica, in a Swedish seminatural grassland at different times of the year. The AMF small subunit rRNA genes were subjected to PCR, cloning, sequencing, and phylogenetic analysis. Nineteen discrete sequence types belonging to Glomus groups A and B and to the genus Acaulospora were distinguished. No significant seasonal changes in the species compositions of the AMF communities as a whole were observed. However, the two plant species hosted significantly different AMF communities. P. vulgaris hosted a rich AMF community throughout the entire growing season. The presence of AMF in A. dioica decreased dramatically in autumn, while an increased presence of Ascomycetes species was detected. PMID:17630308

  19. Effect of arbuscular mycorrhizal fungi (Glomus intraradices) on the oviposition of rice water weevil (Lissorhoptrus oryzophilus).

    PubMed

    Cosme, Marco; Stout, Michael J; Wurst, Susanne

    2011-10-01

    Root-feeding insects are important drivers in ecosystems, and links between aboveground oviposition preference and belowground larval performance have been suggested. The root-colonizing arbuscular mycorrhizal fungi (AMF) play a central role in plant nutrition and are known to change host quality for root-feeding insects. However, it is not known if and how AMF affect the aboveground oviposition of insects whose offspring feed on roots. According to the preference-performance hypothesis, insect herbivores oviposit on plants that will maximize offspring performance. In a greenhouse experiment with rice (Oryza sativa), we investigated the effects of AMF (Glomus intraradices) on aboveground oviposition of rice water weevil (Lissorhoptrus oryzophilus), the larvae of which feed belowground on the roots. Oviposition (i.e., the numbers of eggs laid by weevil females in leaf sheaths) was enhanced when the plants were colonized by AMF. However, the leaf area consumed by adult weevils was not affected. Although AMF reduced plant biomass, it increased nitrogen (N) and phosphorus concentrations in leaves and N in roots. The results suggest that rice water weevil females are able to discriminate plants for oviposition depending on their mycorrhizal status. The discrimination is probably related to AMF-mediated changes in plant quality, i.e., the females choose to oviposit more on plants with higher nutrient concentrations to potentially optimize offspring performance. AMF-mediated change in plant host choice for chewing insect oviposition is a novel aspect of below- and aboveground interactions.

  20. Use of arbuscular mycorrhizal fungi to improve the drought tolerance of Cupressus atlantica G.

    PubMed

    Zarik, Lamia; Meddich, Abdelilah; Hijri, Mohamed; Hafidi, Mohamed; Ouhammou, Ahmed; Ouahmane, Lahcen; Duponnois, Robin; Boumezzough, Ali

    2016-01-01

    In this study, we investigated whether indigenous arbuscular mycorrhizal (AM) fungi could improve the tolerance of Cupressus atlantica against water deficit. We tested a gradient of watering regime spanning from 90% to 25% of soil retention capacity of water on mycorhized and non-mycorhized seedlings in pot cultures with sterilized and non-sterilized soils. Our result showed a positive impact of AM fungi on shoot height, stem diameter and biomass as well as on the growth rate. We also observed that inoculation with AM fungi significantly improved uptake of minerals by C. atlantica in both sterilized and non-sterilized soils independently of water regimes. We found that mycorhized plants maintained higher relative water content (RWC) and water potential compared with non-mycorhized plants that were subjected to drought-stress regimes (50% and 25% of soil retention capacity). The contents of proline and of soluble sugars showed that their concentrations decreased in non-mycorhized plants subjected to DS. Superoxide dismutase (SOD) and catalase (CAT) activities also decreased in non-mycorhized plants submitted to DS compared to mycorhized plants. The same pattern was observed by measuring peroxidase (POD) enzyme activity. The results demonstrated that AM fungal inoculation promoted the growth and tolerance of C. atlantica against DS in pot cultures. Therefore, mycorrhizal inoculation could be a potential solution for the conservation and reestablishment of C. atlantica in its natural ecosystem.

  1. [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.

  2. Arbuscular mycorrhizal fungi in saline soils: Vertical distribution at different soil depth

    PubMed Central

    Becerra, Alejandra; Bartoloni, Norberto; Cofré, Noelia; Soteras, Florencia; Cabello, Marta

    2014-01-01

    Arbuscular mycorrhizal fungi (AMF) colonize land plants in every ecosystem, even extreme conditions such as saline soils. In the present work we report for the first time the mycorrhizal status and the vertical fungal distribution of AMF spores present in the rhizospheric soil samples of four species of Chenopodiaceae (Allenrolfea patagonica, Atriplex argentina, Heterostachys ritteriana and Suaeda divaricata) at five different depths in two saline of central Argentina. Roots showed medium, low or no colonization (0–50%). Nineteen morphologically distinctive AMF species were recovered. The number of AMF spores ranged between 3 and 1162 per 100 g dry soil, and AMF spore number decreased as depth increased at both sites. The highest spore number was recorded in the upper soil depth (0–10 cm) and in S. divaricata. Depending of the host plant, some AMF species sporulated mainly in the deep soil layers (Glomus magnicaule in Allenrolfea patagonica, Septoglomus aff. constrictum in Atriplex argentina), others mainly in the top layers (G. brohultti in Atriplex argentina and Septoglomus aff. constrictum in Allenrolfea patagonica). Although the low percentages of colonization or lack of it, our results show a moderate diversity of AMF associated to the species of Chenopodiaceae investigated in this study. The taxonomical diversity reveals that AMF are adapted to extreme environmental conditions from saline soils of central Argentina. PMID:25242945

  3. Transcriptional responses of Medicago truncatula upon sulfur deficiency stress and arbuscular mycorrhizal symbiosis

    PubMed Central

    Wipf, Daniel; Mongelard, Gaëlle; van Tuinen, Diederik; Gutierrez, Laurent; Casieri, Leonardo

    2014-01-01

    Sulfur plays an essential role in plants' growth and development and in their response to various abiotic and biotic stresses despite its leachability and its very low abundance in the only form that plant roots can uptake (sulfate). It is part of amino acids, glutathione (GSH), thiols of proteins and peptides, membrane sulfolipids, cell walls and secondary products, so reduced availability can drastically alter plant growth and development. The nutritional benefits of symbiotic interactions can help the plant in case of S deficiency. In particular the arbuscular mycorrhizal (AM) interaction improves N, P, and S plant nutrition, but the mechanisms behind these exchanges are not fully known yet. Although the transcriptional changes in the leguminous model plant Medicago truncatula have been already assessed in several biotic and/or abiotic conditions, S deficiency has not been considered so far. The aim of this work is to get a first overview on S-deficiency responses in the leaf and root tissues of plants interacting with the AM fungus Rhizophagus irregularis. Several hundred genes displayed significantly different transcript accumulation levels. Annotation and GO ID association were used to identify biological processes and molecular functions affected by sulfur starvation. Beside the beneficial effects of AM interaction, plants were greatly affected by the nutritional status, showing various differences in their transcriptomic footprints. Several pathways in which S plays an important role appeared to be differentially affected according to mycorrhizal status, with a generally reduced responsiveness to S deficiency in mycorrhized plants. PMID:25520732

  4. Phosphorus cycling in deciduous forest soil differs between stands dominated by ecto- and arbuscular mycorrhizal trees.

    PubMed

    Rosling, Anna; Midgley, Meghan G; Cheeke, Tanya; Urbina, Hector; Fransson, Petra; Phillips, Richard P

    2016-02-01

    Although much is known about how trees and their associated microbes influence nitrogen cycling in temperate forest soils, less is known about biotic controls over phosphorus (P) cycling. Given that mycorrhizal fungi are instrumental for P acquisition and that the two dominant associations - arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi - possess different strategies for acquiring P, we hypothesized that P cycling would differ in stands dominated by trees associated with AM vs ECM fungi. We quantified soil solution P, microbial biomass P, and sequentially extracted inorganic and organic P pools from May to November in plots dominated by trees forming either AM or ECM associations in south-central Indiana, USA. Overall, fungal communities in AM and ECM plots were functionally different and soils exhibited fundamental differences in P cycling. Organic forms of P were more available in ECM plots than in AM plots. Yet inorganic P decreased and organic P accumulated over the growing season in both ECM and AM plots, resulting in increasingly P-limited microbial biomass. Collectively, our results suggest that P cycling in hardwood forests is strongly influenced by biotic processes in soil and that these are driven by plant-associated fungal communities.

  5. Changes in plastid proteome and structure in arbuscular mycorrhizal roots display a nutrient starvation signature.

    PubMed

    Daher, Zeina; Recorbet, Ghislaine; Solymosi, Katalin; Wienkoop, Stefanie; Mounier, Arnaud; Morandi, Dominique; Lherminier, Jeannine; Wipf, Daniel; Dumas-Gaudot, Eliane; Schoefs, Benoît

    2017-01-01

    During arbuscular mycorrhizal symbiosis, arbuscule-containing root cortex cells display a proliferation of plastids, a feature usually ascribed to an increased plant anabolism despite the lack of studies focusing on purified root plastids. In this study, we investigated mycorrhiza-induced changes in plastidic pathways by performing a label-free comparative subcellular quantitative proteomic analysis targeted on plastid-enriched fractions isolated from Medicago truncatula roots, coupled to a cytological analysis of plastid structure. We identified 490 root plastid protein candidates, among which 79 changed in abundance upon mycorrhization, as inferred from spectral counting. According to cross-species sequence homology searches, the mycorrhiza-responsive proteome was enriched in proteins experimentally localized in thylakoids, whereas it was depleted of proteins ascribed predominantly to amyloplasts. Consistently, the analysis of plastid morphology using transmission electron microscopy indicated that starch depletion associated with the proliferation of membrane-free and tubular membrane-containing plastids was a feature specific to arbusculated cells. The loss of enzymes involved in carbon/nitrogen assimilation and provision of reducing power, coupled to macromolecule degradation events in the plastid-enriched fraction of mycorrhizal roots that paralleled lack of starch accumulation in arbusculated cells, lead us to propose that arbuscule functioning elicits a nutrient starvation and an oxidative stress signature that may prime arbuscule breakdown.

  6. Different farming and water regimes in Italian rice fields affect arbuscular mycorrhizal fungal soil communities.

    PubMed

    Lumini, Erica; Vallino, Marta; Alguacil, Maria M; Romani, Marco; Bianciotto, Valeria

    2011-07-01

    Arbuscular mycorrhizal fungi (AMF) comprise one of the main components of soil microbiota in most agroecosystems. These obligate mutualistic symbionts colonize the roots of most plants, including crop plants. Many papers have indicated that different crop management practices could affect AMF communities and their root colonization. However, there is little knowledge available on the influence of conventional and low-input agriculture on root colonization and AMF molecular diversity in rice fields. Two different agroecosystems (continuous conventional high-input rice monocropping and organic farming with a five-year crop rotation) and two different water management regimes have been considered in this study. Both morphological and molecular analyses were performed. The soil mycorrhizal potential, estimated using clover trap cultures, was high and similar in the two agroecosystems. The diversity of the AMF community in the soil, calculated by means of PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) and 18S rDNA sequencing on clover trap cultures roots, was higher for the organic cultivation. The rice roots cultivated in the conventional agrosystem or under permanent flooding showed no AMF colonization, while the rice plants grown under the organic agriculture system showed typical mycorrhization patterns. Considered together, our data suggest that a high-input cropping system and conventional flooding depress AMF colonization in rice roots and that organic managements could help maintain a higher diversity of AMF communities in soil.

  7. Gold Nanomaterial Uptake from Soil Is Not Increased by Arbuscular Mycorrhizal Colonization of Solanum Lycopersicum (Tomato)

    PubMed Central

    Judy, Jonathan D.; Kirby, Jason K.; McLaughlin, Mike J.; Cavagnaro, Timothy; Bertsch, Paul M.

    2016-01-01

    Bioaccumulation of engineered nanomaterials (ENMs) by plants has been demonstrated in numerous studies over the past 5–10 years. However, the overwhelming majority of these studies were conducted using hydroponic systems and the degree to which the addition of the biological and chemical components present in the soil might fundamentally alter the potential of plant bioaccumulation of ENMs is unclear. Here, we used two genotypes of Solanum lycopersicum (tomato), reduced mycorrhizal colonization (rmc), a mutant which does not allow arbuscular mycorrhizal fungi (AMF) colonization, and its progenitor, 76R, to examine how colonization by AMF alters trends of gold ENM bioaccumulation from a natural soil. Gold was taken up and bioaccumulated by plants of both genotypes. Gold concentrations were significantly higher in the rmc treatment although this was likely attributable to the large differences in biomass between the 76R and rmc plants. Regardless, there was little evidence that AMF played a significant role in trafficking Au ENMs into the plants. Furthermore, despite very low NH4NO3 extractable Au concentrations, Au accumulated at the root-soil interface. Although this observation would seem to suggest that ENMs may have potential to influence this particularly biologically active and important soil compartment, we observed no evidence of this here, as the 76R plants developed a robust AMF symbiosis despite accumulation of Au ENMs at the rhizoplane. PMID:28335196

  8. No significant contribution of arbuscular mycorrhizal fungi to transfer of radiocesium from soil to plants.

    PubMed

    Joner, E J; Roos, P; Jansa, J; Frossard, E; Leyval, C; Jakobsen, I

    2004-11-01

    The diffuse pollution by fission and activation products following nuclear accidents and weapons testing is of major public concern. Among the nuclides that pose a serious risk if they enter the human food chain are the cesium isotopes 137Cs and 134Cs (with half-lives of 30 and 2 years, respectively). The biogeochemical cycling of these isotopes in forest ecosystems is strongly affected by their preferential absorption in a range of ectomycorrhiza-forming basidiomycetes. An even more widely distributed group of symbiotic fungi are the arbuscular mycorrhizal fungi, which colonize most herbaceous plants, including many agricultural crops. These fungi are known to be more efficient than ectomycorrhizas in transporting mineral elements from soil to plants. Their role in the biogeochemical cycling of Cs is poorly known, in spite of the consequences that fungal Cs transport may have for transfer of Cs into the human food chain. This report presents the first data on transport of Cs by these fungi by use of radiotracers and compartmented growth systems where uptake by roots and mycorrhizal hyphae is distinguished. Independent experiments in three laboratories that used different combinations of fungi and host plants all demonstrated that these fungi do not contribute significantly to plant uptake of Cs. The implications of these findings for the bioavailability of radiocesium in different terrestrial ecosystems are discussed.

  9. Arbuscular mycorrhizal fungi affect glucosinolate and mineral element composition in leaves of Moringa oleifera.

    PubMed

    Cosme, Marco; Franken, Philipp; Mewis, Inga; Baldermann, Susanne; Wurst, Susanne

    2014-10-01

    Moringa is a mycorrhizal crop cultivated in the tropics and subtropics and appreciated for its nutritive and health-promoting value. As well as improving plant mineral nutrition, arbuscular mycorrhizal fungi (AMF) can affect plant synthesis of compounds bioactive against chronic diseases in humans. Rhizophagus intraradices and Funneliformis mosseae were used in a full factorial experiment to investigate the impact of AMF on the accumulation of glucosinolates, flavonoids, phenolic acids, carotenoids, and mineral elements in moringa leaves. Levels of glucosinolates were enhanced, flavonoids and phenolic acids were not affected, levels of carotenoids (including provitamin A) were species-specifically reduced, and mineral elements were affected differently, with only Cu and Zn being increased by the AMF. This study presents novel results on AMF effects on glucosinolates in leaves and supports conclusions that the impacts of these fungi on microelement concentrations in edible plants are species dependent. The nonspecific positive effects on glucosinolates and the species-specific negative effects on carotenoids encourage research on other AMF species to achieve general benefits on bioactive compounds in moringa.

  10. Uptake Kinetics of Arsenic in Upland Rice Cultivar Zhonghan 221 Inoculated with Arbuscular Mycorrhizal Fungi.

    PubMed

    Chan, W F; Li, W C; Wong, M H

    2015-01-01

    Arbuscular mycorrhizal fungi (AMF) appear to be highly associated with arsenic (As) uptake in host plants because arsenate (As(V)) and phosphorus (P) share the same transporter, whereby AMF can enhance P uptake. A short-term experiment was conducted for low- (0 to 0.05 mM As) and high-affinity (0 to 2.5 mM As) uptake systems, to investigate the AMF role on As uptake mechanism in plants, which may explain As uptake kinetics in upland rice cultivar: Zhonghan 221. When concentration of As ranged from 0 to 0.05 mM, Funneliformis geosporum (Fg) significantly decreased arsenite (As(III)) and monomethylarsonicacid (MMA) uptake when (p < 0.05) compared to non-mycorrhizal (NM) treatment, since the major route for (As(III)) in rice roots-rice silicon transporter Lsi1 would be influenced by Fg inoculation at high As concentrations. Fg can also reduce As(V) uptake significantly (p < 0.05) under both uptake systems relative to NM treatment, whereas, Funneliformis mosseae (Fm) increased As(V) and MMA uptake in rice roots, with MMA uptake rate generally lower than As(III) and As(V). Using suitable AMF species inoculation with rice, As uptake and accumulation in rice grains can be reduced and the risk to human health, once consumed, can be minimized.

  11. Microwave-assisted technology for the clearing and staining of arbuscular mycorrhizal fungi in roots.

    PubMed

    Dalpé, Yolande; Séguin, Sylvie Marie

    2013-05-01

    The use of microwave irradiation as a source of energy to clear and stain intra-radical arbuscular mycorrhizal fungi propagules has been tested on a variety of indigenous and cultivated herbaceous plants. The aim of the study was to evaluate the efficiency of microwave irradiation on root softening, fungi tissue staining, and preservation of DNA integrity for subsequent molecular analyses. The proposed methodology has been adapted from the standard procedures used to detect and quantify mycorrhizal root colonization levels. Using a domestic microwave oven, tissue clearing and staining required together between 30 s and 1.5 min of microwave treatment to be completed, depending the diameter size of the roots. The well-performing chemical stains tested were acid fuchsin, trypan blue, and aniline blue. The acid fuchsin clearing and staining processes, as performed, were also demonstrated to preserve DNA integrity for further molecular analyses. Irradiation by microwaves has been used with success in our laboratory within the frame of several studies. It offers considerable time saving over traditional method, reducing processing times from several hours to a few minutes while decreasing considerably the amount of chemicals and energy required to perform analyses.

  12. Diversity of morphology and function in arbuscular mycorrhizal symbioses in Brachypodium distachyon.

    PubMed

    Hong, Jeon J; Park, Yong-Soon; Bravo, Armando; Bhattarai, Kishor K; Daniels, Dierdra A; Harrison, Maria J

    2012-09-01

    Brachypodium distachyon is a grass species that serves as a useful model for wheat and also for many of the grass species proposed as feedstocks for bioenergy production. Here, we monitored B. distachyon symbioses with five different arbuscular mycorrhizal (AM) fungi and identified symbioses that vary functionally with respect to plant performance. Three symbioses promoted significant increases in shoot phosphorus (P) content and shoot growth of Brachypodium, while two associations were neutral. The Brachypodium/Glomus candidum symbiosis showed a classic 'Paris-type' morphology. In the other four AM symbioses, hyphal growth was exclusively intracellular and linear; hyphal coils were not observed and arbuscules were abundant. Expression of the Brachypodium ortholog of the symbiosis-specific phosphate (Pi) transporter MtPT4 did not differ significantly in these five interactions indicating that the lack of apparent functionality did not result from a failure to express this gene or several other AM symbiosis-associated genes. Analysis of the expression patterns of the complete PHT1 Pi transporter gene family and AMT2 gene family in B. distachyon/G. intraradices mycorrhizal roots identified additional family members induced during symbiosis and again, transcript levels were similar in the different Brachypodium AM symbioses. This initial morphological, molecular and functional characterization provides a framework for future studies of functional diversity in AM symbiosis in B. distachyon.

  13. Identification of heavy metal-induced genes encoding glutathione S-transferases in the arbuscular mycorrhizal fungus Glomus intraradices.

    PubMed

    Waschke, A; Sieh, D; Tamasloukht, M; Fischer, K; Mann, P; Franken, P

    2006-12-01

    Arbuscular mycorrhizal fungi are able to alleviate the stress for plants caused by heavy metal contamination of soil. To analyze the molecular response of arbuscular mycorrhizal fungi to these pollutants, a subtractive cDNA library was constructed using RNA from Glomus intraradices extraradical hyphae of a root organ culture treated with a mixture of Cd, Zn, and Cu. Screening by reverse Northern blot analysis indicated that, among 308 clones, 17% correspond to genes up-regulated by heavy metals. Sequence analysis of part of the clones resulted, amongst others, in the identification of six genes putatively coding for glutathione S-transferases belonging to two different classes of these enzymes. Expression analyses indicated that the genes are differentially expressed during fungal development and that their RNA accumulation dramatically increases in extraradical hyphae grown in a heavy metal-containing solution.

  14. Differential gene expressions in arbuscular mycorrhizal-colonized tomato grown under heavy metal stress.

    PubMed

    Ouziad, Fouad; Hildebrandt, Ulrich; Schmelzer, Elmon; Bothe, Hermann

    2005-06-01

    When tomato was grown in either "Breinigerberg" soil, which has a high content of Zn and of other heavy metals or in non-polluted soil enriched with up to 1 mM CdCl2, plants colonized with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices grew distinctly better than non-mycorrhizal controls. An analysis of differential mRNA transcript formations was performed on several plant genes coding for products potentially involved in heavy metal tolerance. Northern blot analyses indicated that the mRNA from either roots or leaves was not differentially expressed in the case of LePCS1 (coding for phytochelatin synthase), Lemt1, Lemt3 and Lemt4 (for metallothioneins) or LeNramp2 (for a broad range heavy metal transporter) in both mycorrhizal and non-mycorrhizal plants, grown either with or without heavy metals. In contrast, Lemt2 was strongly expressed only in non-AMF-colonized roots, and only after growth in the Breinigerberg soil or in the presence of high CdCl2-concentrations. AMF colonization distinctly reduced the level of Lemt2 transcripts. This was also the case for the root specific LeNramp1 transporter, however, only after growth in the Breinigerberg soil, but not under Cd-stress. Likewise, the levels of LeNramp3 transcripts were reduced by the AMF colonization in roots, but not in leaves. Quantitative Real-Time RT-PCR-experiments performed with Lemt2, LeNramp1 and LeNramp3 largely corroborated the Northern analysis data. In situ hybridization experiments with Lemt2 and LeNramp1 showed that both genes were strongly expressed throughout the plant cells in non-colonized roots, whereas colonized roots revealed only few signals restricted to some parenchyma cells. All the data suggest that the transcript levels of some, but not all genes of the Nramp or mt family are elevated under heavy metal stress. AMF colonization results in a down-regulation of these genes, presumably due to the fact that the content of heavy metals is lower in mycorrhizal than in non

  15. Arbuscular mycorrhizal symbiosis alleviates detrimental effects of saline reclaimed water in lettuce plants.

    PubMed

    Vicente-Sánchez, J; Nicolás, E; Pedrero, F; Alarcón, J J; Maestre-Valero, J F; Fernández, F

    2014-07-01

    The present study evaluated the effects of inoculation with arbuscular mycorrhizal fungi (AMF; Glomus iranicum var. tenuihypharum sp. nova) on the physiological performance and production of lettuce plants grown under greenhouse conditions and supplied with reclaimed water (RW; urban-treated wastewater with high electrical conductivity; 4.19 dS m(-1)). Four treatments, fresh water, fresh water plus AMF inoculation, RW and RW plus AMF inoculation, were applied and their effects, over time, analyzed. Root mycorrhizal colonization, plant biomass, leaf-ion content, stomatal conductance and net photosynthesis were assessed. Overall, our results highlight the significance of the AMF in alleviation of salt stress and their beneficial effects on plant growth and productivity. Inoculated plants increased the ability to acquire N, Ca, and K from both non-saline and saline media. Moreover, mycorrhization significantly reduced Na plant uptake. Under RW conditions, inoculated plants also showed a better performance of physiological parameters such as net photosynthesis, stomatal conductance and water-use efficiency than non-mycorrhizal plants. Additionally, the high concentration of nutrients already dissolved in reclaimed water suggested that adjustments in the calculation of the fertigation should be conducted by farmers. Finally, this experiment has proved that mycorrhization could be a suitable way to induce salt stress resistance in iceberg lettuce crops as plants supplied with reclaimed water satisfied minimum legal commercial size thresholds. Moreover, the maximum values of Escherichia coli in the reclaimed water were close to but never exceeded the international thresholds established (Spanish Royal Decree 1620/2007; Italian Decree, 2003) and hence lettuces were apt for sale.

  16. Arbuscular mycorrhizal fungi alter plant allometry and biomass–density relationships

    PubMed Central

    Zhang, Qian; Zhang, Lu; Weiner, Jacob; Tang, Jianjun; Chen, Xin

    2011-01-01

    Background and Aims Plant biomass–density relationships during self-thinning are determined mainly by allometry. Both allometry and biomass–density relationship have been shown to vary with abiotic conditions, but the effects of biotic interactions have not been investigated. Arbuscular mycorrhizal fungi (AMF) can promote plant growth and affect plant form. Here experiments were carried out to test whether AMF affect plant allometry and the self-thinning trajectory. Methods Two experiments were conducted on Medicago sativa L., a leguminous species known to be highly dependent on mycorrhiza. Two mycorrhizal levels were obtained by applying benomyl (low AMF) or not (high AMF). Experiment 1 investigated the effects of AMF on plant growth in the absence of competition. Experiment 2 was a factorial design with two mycorrhizal levels and two plant densities (6000 and 17 500 seeds m−2). Shoot biomass, root biomass and canopy radius were measured 30, 60, 90 and 120 d after sowing. The allometric relationships among these aspects of size were estimated by standardized major axis regression on log-transformed data. Key Results Shoot biomass in the absence of competition was lower under low AMF treatment. In self-thinning populations, the slope of the log (mean shoot biomass) vs. log density relationship was significantly steeper for the high AMF treatment (slope = –1·480) than for the low AMF treatment (–1·133). The canopy radius–biomass allometric exponents were not significantly affected by AMF level, but the root–shoot allometric exponent was higher in the low AMF treatment. With a high level of AMF, the biomass–density exponent can be predicted from the above-ground allometric model of self-thinning, while this was not the case when AMF were reduced by fungicide. Conclusions AMF affected the importance of below-ground relative to above-ground interactions and changed root vs. shoot allocation. This changed allometric allocation of biomass and altered

  17. Impact of an invasive nitrogen-fixing tree on arbuscular mycorrhizal fungi and the development of native species

    PubMed Central

    Guisande-Collazo, Alejandra; González, Luís; Souza-Alonso, Pablo

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) are obligate soil biotrophs that establish intimate relationships with 80 % of terrestrial plant families. Arbuscular mycorrhizal fungi obtain carbon from host plants and contribute to the acquisition of mineral nutrients, mainly phosphorus. The presence of invasive plants has been identified as a soil disturbance factor, often conditioning the structure and function of soil microorganisms. Despite the investigation of many aspects related to the invasion of Acacia dealbata, the effect produced on the structure of AMF communities has never been assessed. We hypothesize that A. dealbata modifies the structure of AMF community, influencing the establishment and growth of plants that are dependent on these mutualisms. To validate our hypothesis, we carried out denaturing gradient gel electrophoresis (DGGE) analysis and also grew plants of Plantago lanceolata in pots using roots of native shrublands or from A. dealbata, as inoculum of AMF. Cluster analyses from DGGE indicated an alteration in the structure of AMF communities in invaded soils. After 15 weeks, we found that plants grown in pots containing native roots presented higher stem and root growth and also produced higher biomass in comparison with plants grown with A. dealbata inoculum. Furthermore, plants that presented the highest biomass and growth exhibited the maximum mycorrhizal colonization and phosphorus content. Moreover, fluorescence measurements indicated that plants grown with A. dealbata inoculum even presented higher photosynthetic damage. Our results indicate that the presence of the invader A. dealbata modify the composition of the arbuscular fungal community, conditioning the establishment of native plants. PMID:26984185

  18. Phosphorus supply, arbuscular mycorrhizal fungal species, and plant genotype impact on the protective efficacy of mycorrhizal inoculation against wheat powdery mildew.

    PubMed

    Mustafa, G; Randoux, B; Tisserant, B; Fontaine, J; Magnin-Robert, M; Lounès-Hadj Sahraoui, A; Reignault, Ph

    2016-10-01

    A potential alternative strategy to chemical control of plant diseases could be the stimulation of plant defense by arbuscular mycorrhizal fungi (AMF). In the present study, the influence of three parameters (phosphorus supply, mycorrhizal inoculation, and wheat cultivar) on AMF protective efficiency against Blumeria graminis f. sp. tritici, responsible for powdery mildew, was investigated under controlled conditions. A 5-fold reduction (P/5) in the level of phosphorus supply commonly recommended for wheat in France improved Funneliformis mosseae colonization and promoted protection against B. graminis f. sp. tritici in a more susceptible wheat cultivar. However, a further decrease in P affected plant growth, even under mycorrhizal conditions. Two commercially available AMF inocula (F. mosseae, Solrize®) and one laboratory inoculum (Rhizophagus irregularis) were tested for mycorrhizal development and protection against B. graminis f. sp. tritici of two moderately susceptible and resistant wheat cultivars at P/5. Mycorrhizal levels were the highest with F. mosseae (38 %), followed by R. irregularis (19 %) and Solrize® (SZE, 8 %). On the other hand, the highest protection level against B. graminis f. sp. tritici was obtained with F. mosseae (74 %), followed by SZE (58 %) and R. irregularis (34 %), suggesting that inoculum type rather than mycorrhizal levels determines the protection level of wheat against B. graminis f. sp. tritici. The mycorrhizal protective effect was associated with a reduction in the number of conidia with haustorium and with an accumulation of polyphenolic compounds at B. graminis f. sp. tritici infection sites. Both the moderately susceptible and the most resistant wheat cultivar were protected against B. graminis f. sp. tritici infection by F. mosseae inoculation at P/5, although the underlying mechanisms appear rather different between the two cultivars. This study emphasizes the importance of taking into account the considered

  19. Aligning molecular studies of mycorrhizal fungal diversity with ecologically important levels of diversity in ecosystems

    PubMed Central

    Sanders, Ian R; Rodriguez, Alia

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) occur in the roots of most plants and are an ecologically important component of the soil microbiome. Richness of AMF taxa is a strong driver of plant diversity and productivity, thus providing a rationale for characterizing AMF diversity in natural ecosystems. Consequently, a large number of molecular studies on AMF community composition are currently underway. Most published studies, at best, only address species or genera-level resolution. However, several experimental studies indicate that variation in plant performance is large among plants colonised by different individuals of one AMF species. Thus, there is a potential disparity between how molecular community ecologists are currently describing AMF diversity and the level of AMF diversity that may actually be ecologically relevant. We propose a strategy to find many polymorphic loci that can define within-species genetic variability within AMF, or at any level of resolution desired within the Glomermycota. We propose that allele diversity at the intraspecific level could then be measured for target AMF groups, or at other levels of resolution, in environmental DNA samples. Combining the use of such markers with experimental studies on AMF diversity would help to elucidate the most important level(s) of AMF diversity in plant communities. Our goal is to encourage ecologists who are trying to explain how mycorrhizal fungal communities are structured to take an approach that could also yield meaningful information that is relevant to the diversity, functioning and productivity of ecosystems. PMID:27128992

  20. Fern-associated arbuscular mycorrhizal fungi are represented by multiple Glomus spp.: do environmental factors influence partner identity?

    PubMed

    West, Brittany; Brandt, Jessica; Holstien, Kay; Hill, April; Hill, Malcolm

    2009-06-01

    Symbioses involving arbuscular mycorrhizal fungi (AMF) are among the most important ecological associations for many plant species. The diversity of AMF associated with ferns, however, remains poorly studied. Using recently designed Glomus-specific primers, we surveyed the AMF community associated with ferns from deciduous, broad-leaved second-growth forest habitats at the eastern edge of the piedmont region of central Virginia, USA. Results indicate that this molecular approach may be a useful tool for detecting AMF in ferns compared to traditional techniques based on morphology. Over 30 potential fungal ribotypes were identified from eight fern species using denaturing gradient gel electrophoresis. Fungal ribotypes were found to differ widely in terms of (1) the number of fern partners with which they interact and (2) their relative frequency within each fern. Sequence analysis of fungal isolates from three species of fern indicated that the primers were generally highly specific for Glomus species but some non-target DNA was also amplified. Cloned polymerase chain reaction (PCR) products from Polystichum acrostichoides and Osmunda regalis revealed several phylogenetically distinct Glomus species. A single Glomus species was identified in the cloned PCR products from Botrychium virginianum. These findings challenge the hypothesis that the extent or degree of fern-fungal symbiosis is somehow tied to root complexity. Environmental factors appear to influence the suite of AMF that form partnerships with ferns. Some species of fern from similar habitats associated with dissimilar fungal partners (e.g., P. acrostichoides and Athyrium filix-femina var. asplenioides), whereas others harbored uniform fungal communities (e.g., Asplenium platyneuron). The significance of these data in terms of ecological and evolutionary dynamics of the AMF-fern symbiosis is discussed.

  1. Septoglomus fuscum and S. furcatum, two new species of arbuscular mycorrhizal fungi (Glomeromycota).

    PubMed

    Blaszkowski, Janusz; Chwat, Gerard; Kovács, Gábor M; Gáspár, Bence K; Ryszka, Przemyslaw; Orlowska, Elzbieta; Pagano, Marcela C; Araújo, Francisca S; Wubet, Tesfaye; Buscot, François

    2013-01-01

    Two new arbuscular mycorrhizal fungal species, (Glomeromycota) Septoglomus fuscum and S. furcatum, are described and illustrated. Spores of S. fuscum usually occur in loose hypogeous clusters, rarely singly in soil or inside roots, and S. furcatum forms only single spores in soil. Spores of S. fuscum are brownish orange to dark brown, globose to subglobose, (20-)47(-90) μm diam, rarely ovoid, 21-50 × 23-60 μm. Their spore wall consists of a semi-persistent, semi-flexible, orange white to golden yellow, rarely hyaline, outer layer, easily separating from a laminate, smooth, brownish orange to dark brown inner layer. Spores of S. furcatum are reddish brown to dark brown, globose to subglobose, (106-) 138(-167) μm diam, rarely ovoid, 108-127 × 135-160 μm, usually with one subtending hypha that is frequently branched below the spore base, or occasionally with two subtending hyphae located close together. Spore walls consists of a semipermanent, hyaline to light orange outermost layer, a semipermanent, hyaline to golden yellow middle layer, and a laminate, smooth, reddish brown to dark brown innermost layer. None of the spore-wall layers of S. fuscum and S. furcatum stain in Melzer's reagent. In the field, S. fuscum was associated with roots of Arctotheca populifolia colonizing maritime dunes located near Strand in South Africa and S. furcatum was associated with Cordia oncocalyx growing in a dry forest in the Ceará State, Brazil. In single-species cultures with Plantago lanceolata as host plant, S. fuscum and S. furcatum formed arbuscular mycorrhizae. Phylogenetic analyses of the SSU, ITS and LSU nrDNA sequences placed the two new species in genus Septoglomus and both new taxa were separated from described Septoglomus species.

  2. Dynamics of periarbuscular membranes visualized with a fluorescent phosphate transporter in arbuscular mycorrhizal roots of rice.

    PubMed

    Kobae, Yoshihiro; Hata, Shingo

    2010-03-01

    In arbuscular mycorrhizal (AM) symbiosis, host plants supply photosynthates to AM fungi and, in return, they receive inorganic nutrients such as phosphate from finely branched fungal arbuscules. Plant cortical cells envelope arbuscules with periarbuscular membranes that are continuous with the plant plasma membranes. We prepared transgenic rice (Oryza sativa) plants that express a fusion of green fluorescent protein with rice AM-inducible phosphate transporter, OsPT11-GFP, and grew them with AM fungi. The fluorescence of the fusion transporter was observed in the arbuscule branch domain, where active nutrient exchange seems to occur. In contrast, a signal was not detected around intracellular hyphal coils on colonization by either Glomus mosseae or Gigaspora rosea, making the difference between Arum- and Paris-type mycorrhizae ambiguous. We also invented a simple device involving glass-bottomed Petri dishes for in planta observation of fluorescent proteins in living AM roots with an inverted fluorescence microscope. The plant bodies remain completely intact, avoiding any stressful procedure such as cutting, staining, etc. Since rice roots exhibit a very low level of autofluorescence, the device enabled clear time-lapse imaging to analyze the formation, function and degeneration of arbuscules. In cortical cells, arbuscules seemed to be functional for only 2-3 d. Suddenly, the arbuscular branches became fragile and they shrank. At this stage, however, the periarbuscular membranes appeared intact. Then, the fluorescence of the transporter disappeared within only 2.5-5.5 h. The collapse of arbuscules occurred in the subsequent several days. Thus, our device has a great advantage for investigation of dynamic features of AM symbiosis.

  3. Arbuscular mycorrhizal fungi facilitate the invasion of Solidago canadensis L. in southeastern China

    NASA Astrophysics Data System (ADS)

    Yang, Ruyi; Zhou, Gang; Zan, Shuting; Guo, Fuyu; Su, Nannan; Li, Jing

    2014-11-01

    The significance of arbuscular mycorrhizal fungi (AMF) in the process of plant invasion is still poorly understood. We hypothesize that invasive plants would change local AMF community structure in a way that would benefit themselves but confer less advantages to native plants, thus influencing the extent of plant interactions. An AMF spore community composed of five morphospecies of Glomus with equal density (initial AMF spore community, I-AMF) was constructed to test this hypothesis. The results showed that the invasive species, Solidago canadensis, significantly increased the relative abundance of G. geosperum and G. etunicatum (altered AMF spore community, A-AMF) compared to G. mosseae, which was a dominant morphospecies in the monoculture of native Kummerowia striata. The shift in AMF spore community composition driven by S. canadensis generated functional variation between I-AMF and A-AMF communities. For example, I-AMF increased biomass and nutrient uptake of K. striata in both monocultures and mixtures of K. striata and S. canadensis compared to A-AMF. In contrast, A-AMF significantly enhanced root nitrogen (N) acquisition of S. canadensis grown in mixture. Moreover, mycorrhizal-mediated 15N uptake provided direct evidence that I-AMF and A-AMF differed in their affinities with native and invading species. The non-significant effect of A-AMF on K. striata did not result from allelopathy as root exudates of S. canadensis exhibited positive effects on seed germination and biomass of K. striata under naturally occurring concentrations. When considered together, we found that A-AMF facilitated the invasion of S. canadensis through decreasing competitiveness of the native plant K. striata. The results supported our hypothesis and can be used to improve our understanding of an ecosystem-based perspective towards exotic plant invasion.

  4. [Effects of different peony cultivars on community structure of arbuscular mycorrhizal fungi in rhizosphere soil].

    PubMed

    Guo, Shao-Xia; Liu, Run-Jin

    2010-08-01

    This paper studied the community structure of arbuscular mycorrhizal (AM) fungi in the rhizosphere soil of different peony (Paeonia suffruticosa) cultivars grown in Zhaolou Peony Garden of Heze in Shandong Province. A number of parameters describing this community structure, e. g., spore density, species- and genera composition, species richness, distribution frequency, species diversity indices, and Sorenson's similarity coefficient, were examined. The species- and genera composition, species richness, and distribution frequency of AM fungi in rhizosphere soil varied with planted peony cultivars. A total of 10 AM fungal species were isolated from the rhizosphere soil of cultivars 'Fengdan' and 'Zhaofen', 9 species from the rhizosphere soil of 'Wulong pengsheng' and 'Luoyang red', and 8 species from the rhizosphere soil of 'Hu red'. The spore density was the highest (59 per 50 g soil) in the rhizosphere soil of 'Fengdan', but the lowest (47 per 50 g soil) in the rhizosphere soil of 'Hu red'; the species diversity index was the highest (1.89) in the rhizosphere soil of 'Zhaofen', but the lowest (1.71) in the rhizosphere soil of 'Hu red'; and the mycorrhizal colonization rate was the highest (63.6%) in rhizosphere soil of 'Fengdan' and 'Hu red', but the lowest (52.7%) in the rhizosphere soil of 'Wulong pengsheng'. The Sorenson's similarity coefficient of AM fungal species composition in the rhizosphere soil among the test cultivars ranged from 0.71 to 0.95, being the highest between 'Wulong pengsheng' and 'Fengdan', and the lowest between 'Luoyang red' and 'Hu red'. It was concluded that the gene type of peony could change the community structure of AM fungi in rhizosphere soil.

  5. Response of endangered plant species to inoculation with arbuscular mycorrhizal fungi and soil bacteria.

    PubMed

    Zubek, Szymon; Turnau, Katarzyna; Tsimilli-Michael, Merope; Strasser, Reto J

    2009-02-01

    Three endangered plant species, Plantago atrata and Pulsatilla slavica, which are on the IUCN red list of plants, and Senecio umbrosus, which is extinct in the wild in Poland, were inoculated with soil microorganisms to evaluate their responsiveness to inoculation and to select the most effective microbial consortium for application in conservation projects. Individuals of these taxa were cultivated with (1) native arbuscular mycorrhizal fungi (AMF) isolated from natural habitats of the investigated species, (2) a mixture of AMF strains available in the laboratory, and (3) a combination of AMF lab strains with rhizobacteria. The plants were found to be dependent on AMF for their growth; the mycorrhizal dependency for P. atrata was 91%, S. umbrosus-95%, and P. slavica-65%. The applied inocula did not significantly differ in the stimulation of the growth of P. atrata and S. umbrosus, while in P. slavica, native AMF proved to be the less efficient. We therefore conclude that AMF application can improve the ex situ propagation of these three threatened taxa and may contribute to the success of S. umbrosus reintroduction. A multilevel analysis of chlorophyll a fluorescence transients by the JIP test permitted an in vivo evaluation of plant vitality in terms of biophysical parameters quantifying photosynthetic energy conservation, which was found to be in good agreement with the results concerning physiological parameters. Therefore, the JIP test can be used to evaluate the influence of AMF on endangered plants, with the additional advantage of being applicable in monitoring in a noninvasive way the acclimatization of reintroduced species in nature.

  6. Community Dynamics of Arbuscular Mycorrhizal Fungi in High-Input and Intensively Irrigated Rice Cultivation Systems

    PubMed Central

    Wang, Yutao; Li, Ting; Li, Yingwei; Björn, Lars Olof; Rosendahl, Søren; Olsson, Pål Axel; Fu, Xuelin

    2015-01-01

    Application of a mycorrhizal inoculum could be one way to increase the yield of rice plants and reduce the application of fertilizer. We therefore studied arbuscular mycorrhizal fungi (AMF) in the roots of wetland rice (Oryza sativa L.) collected at the seedling, tillering, heading, and ripening stages in four paddy wetlands that had been under a high-input and intensively irrigated rice cultivation system for more than 20 years. It was found that AMF colonization was mainly established in the heading and ripening stages. The AMF community structure was characterized in rhizosphere soils and roots from two of the studied paddy wetlands. A fragment covering the partial small subunit (SSU), the whole internal transcribed spacer (ITS), and the partial large subunit (LSU) rRNA operon regions of AMF was amplified, cloned, and sequenced from roots and soils. A total of 639 AMF sequences were obtained, and these were finally assigned to 16 phylotypes based on a phylogenetic analysis, including 12 phylotypes from Glomeraceae, one phylotype from Claroideoglomeraceae, two phylotypes from Paraglomeraceae, and one unidentified phylotype. The AMF phylotype compositions in the soils were similar between the two surveyed sites, but there was a clear discrepancy between the communities obtained from root and soil. The relatively high number of AMF phylotypes at the surveyed sites suggests that the conditions are suitable for some species of AMF and that they may have an important function in conventional rice cultivation systems. The species richness of root-colonizing AMF increased with the growth of rice, and future studies should consider the developmental stages of this crop in the exploration of AMF function in paddy wetlands. PMID:25681190

  7. Red list plants: colonization by arbuscular mycorrhizal fungi and dark septate endophytes.

    PubMed

    Fuchs, B; Haselwandter, K

    2004-08-01

    Since information concerning the mycorrhization of endangered plants is of major importance for their potential re-establishment, we determined the mycorrhizal status of Serratula tinctoria (Asteraceae), Betonica officinalis (Lamiaceae), Drosera intermedia (Droseraceae) and Lycopodiella inundata (Lycopodiaceae), occurring at one of two wetland sites (fen meadow and peat bog), which differed in soil pH and available P levels. Root colonization by arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) was quantified. Colonization by AMF appeared to be more frequent in the fen meadow than in the peat bog, and depended on the host plant. Roots of S. tinctoria and B. officinalis were well colonized by AMF in the fen meadow (35-55% root length) and both arbuscules and vesicles were observed to occur in spring as well as in autumn. In the peat bog, L. inundata showed a low level of root colonization in spring, when vesicles were found frequently but no arbuscules. In roots of D. intermedia from the peat bog, arbuscules and vesicles were observed, but AMF colonization was lower than in L. inundata. In contrast, the amount of AMF spores extracted from soil at the peat bog site was higher than from the fen meadow soil. Spore numbers did not differ between spring and autumn in the fen meadow, but they were higher in spring than in autumn in the peat bog. Acaulospora laevis or A. colossica and Glomus etunicatum were identified amongst the AMF spores extracted from soil at the two sites. S. tinctoria and B. officinalis roots were also regularly colonized by DSE (18-40% root length), while L. inundata was only rarely colonized and D. intermedia did not seem to be colonized by DSE at all.

  8. Colonization of pennycresses (Thlaspi spp.) of the Brassicaceae by arbuscular mycorrhizal fungi.

    PubMed

    Regvar, Marjana; Vogel, Katarina; Irgel, Nina; Wraber, Tone; Hildebrandt, Ulrich; Wilde, Petra; Bothe, Hermann

    2003-06-01

    Members of the Brassicaceae are generally believed to be non-mycorrhizal. Pennycress (Thlaspi) species of this family from diverse locations in Slovenia, Austria, Italy and Germany were examined for their colonisation by arbuscular mycorrhizal fungi (AMF). Meadow species (T. praecox, T. caerulescens and T. montanum) were sparsely but distinctly colonised, as indicated by the occurrence of intraradical hyphae, vesicles, coils, and occasionally arbuscules. Species from other locations were poorly colonised, but arbuscules were not discernible. The genus Thlaspi comprises several heavy metal hyperaccumulating species (T. caerulescens, T. goesingense, T. calaminare, T. cepaeifolium). All samples collected from heavy metal soils were at best poorly colonized. Thus the chance is small to find a "hypersystem" in phytoremediation consisting of an AM fungus which prevents the uptake of the major part of the heavy metals and of a Thlaspi species which effectively deposits the residual heavy metals inevitably taken up into its vacuoles. In two different PCR approaches, fungal DNA was amplified from most of the Thlaspi roots examined, even from those with a very low incidence of AMF colonization. Sequencing of the 28S- and 18S-rDNA PCR-products revealed that different Thlaspi field samples were colonized by Glomus intraradices and thus by a common AM fungus. However, none of the sequences obtained was identical to any other found in the present study or deposited in the databanks, which might indicate that a species continuum exists in the G. intraradices clade. An effective colonization of Thlaspi by AMF could not be established in greenhouse experiments. Although the data show that Thlaspi can be colonized by AMF, it is doubtful whether an effective symbiosis with the mutual exchange of metabolites is formed by both partners.

  9. Gibberellins Interfere with Symbiosis Signaling and Gene Expression and Alter Colonization by Arbuscular Mycorrhizal Fungi in Lotus japonicus1

    PubMed Central

    Takeda, Naoya; Handa, Yoshihiro; Tsuzuki, Syusaku; Kojima, Mikiko; Sakakibara, Hitoshi; Kawaguchi, Masayoshi

    2015-01-01

    Arbuscular mycorrhiza is a mutualistic plant-fungus interaction that confers great advantages for plant growth. Arbuscular mycorrhizal (AM) fungi enter the host root and form symbiotic structures that facilitate nutrient supplies between the symbionts. The gibberellins (GAs) are phytohormones known to inhibit AM fungal infection. However, our transcriptome analysis and phytohormone quantification revealed GA accumulation in the roots of Lotus japonicus infected with AM fungi, suggesting that de novo GA synthesis plays a role in arbuscular mycorrhiza development. We found pleiotropic effects of GAs on the AM fungal infection. In particular, the morphology of AM fungal colonization was drastically altered by the status of GA signaling in the host root. Exogenous GA treatment inhibited AM hyphal entry into the host root and suppressed the expression of Reduced Arbuscular Mycorrhization1 (RAM1) and RAM2 homologs that function in hyphal entry and arbuscule formation. On the other hand, inhibition of GA biosynthesis or suppression of GA signaling also affected arbuscular mycorrhiza development in the host root. Low-GA conditions suppressed arbuscular mycorrhiza-induced subtilisin-like serine protease1 (SbtM1) expression that is required for AM fungal colonization and reduced hyphal branching in the host root. The reduced hyphal branching and SbtM1 expression caused by the inhibition of GA biosynthesis were recovered by GA treatment, supporting the theory that insufficient GA signaling causes the inhibitory effects on arbuscular mycorrhiza development. Most studies have focused on the negative role of GA signaling, whereas our study demonstrates that GA signaling also positively interacts with symbiotic responses and promotes AM colonization of the host root. PMID:25527715

  10. The roles of arbuscular mycorrhizal fungi (AMF) in phytoremediation and tree-herb interactions in Pb contaminated soil

    PubMed Central

    Yang, Yurong; Liang, Yan; Han, Xiaozhen; Chiu, Tsan-Yu; Ghosh, Amit; Chen, Hui; Tang, Ming

    2016-01-01

    Understanding the roles of arbuscular mycorrhizal fungi (AMF) in plant interaction is essential for optimizing plant distribution to restore degraded ecosystems. This study investigated the effects of AMF and the presence of legume or grass herbs on phytoremediation with a legume tree, Robinia pseudoacacia, in Pb polluted soil. In monoculture, mycorrhizal dependency of legumes was higher than that of grass, and AMF benefited the plant biomass of legumes but had no effect on grass. Mycorrhizal colonization of plant was enhanced by legume neighbors but inhibited by grass neighbor in co-culture system. N, P, S and Mg concentrations of mycorrhizal legumes were larger than these of non-mycorrhizal legumes. Legume herbs decreased soil pH and thereby increased the Pb concentrations of plants. The neighbor effects of legumes shifted from negative to positive with increasing Pb stress levels, whereas grass provided a negative effect on the growth of legume tree. AMF enhanced the competition but equalized growth of legume-legume under unpolluted and Pb stress conditions, respectively. In conclusion, (1) AMF mediate plant interaction through directly influencing plant biomass, and/or indirectly influencing plant photosynthesis, macronutrient acquisition, (2) legume tree inoculated with AMF and co-planted with legume herbs provides an effective way for Pb phytoremediation. PMID:26842958

  11. ARBUSCULAR MYCORRHIZAL COLONIZATION OF LARREA TRIDENTATA AND AMBROSIA DUMOSA ROOTS VARIES WITH PRECIPITATION AND SEASON IN THE MOJAVE DESERT

    SciTech Connect

    M. E. APPLE; C. I. THEE; V. L. SMITH-LONGOZO; C. R. COGAR; C. E. WELLS; R. S. NOWAK

    2004-01-01

    The percentage of fine roots colonized by arbuscular mycorrhizal (AM) fungi varied with season and with species in the co-dominant shrubs Lurreu tridentutu and Ambrosia dumosu at a site adjacent to the Nevada Desert FACE (Free-Air CO{sub 2} Enrichment) Facility (NDFF) in the Mojave Desert. We excavated downward and outward from the shrub bases in both species to collect and examine fine roots (< 1.0 mm diameter) at monthly intervals throughout 2001 and from October 2002 to September 2003. Fungal structures became visible in cleared roots stained with trypan blue. We quantified the percent colonization of roots by AM fungi via the line intercept method. In both years and for both species, colonization was highest in fall, relatively low in spring when root growth began, increased in late spring, and decreased during summer drought periods. Increases in colonization during summer and fall reflect corresponding increases in precipitation. Spring mycorrhizal colonization is low despite peaks in soil water availability and precipitation, indicating that precipitation is not the only factor influencing mycorrhizal colonization. Because the spring decrease in mycorrhizal colonization occurs when these shrubs initiate a major flush of fine root growth, other phenological events such as competing demands for carbon by fine root initiation, early season shoot growth, and flowering may reduce carbon availability to the fungus, and hence decrease colonization. Another possibility is that root growth exceeds the rate of mycorrhizal colonization.

  12. Colonization by Arbuscular Mycorrhizal Fungi of Sorghum Leads to Reduced Germination and Subsequent Attachment and Emergence of Striga hermonthica.

    PubMed

    Lendzemo, Venasius W; Kuyper, Thomas W; Matusova, Radoslava; Bouwmeester, Harro J; Van Ast, Aad

    2007-01-01

    TWO SORGHUM CULTIVARS: the Striga-tolerant S-35 and the Striga-sensitive CK60-B were grown with or without arbuscular mycorrhizal (AM) fungi, and with or without phosphorus addition. At 24 and 45 days after sowing (DAS) of sorghum, root exudates were collected and tested for effects on germination of preconditioned Striga hermonthica seeds. Root exudates from AM sorghum plants induced lower germination of S. hermonthica seeds than exudates from non-mycorrhizal sorghum. The magnitude of this effect depended on the cultivar and harvest time. A significantly (88-97%) lower germination of S. hermonthica seeds upon exposure to root exudates from AM S-35 plants was observed at both harvest times whereas for AM inoculated CK60-B plants a significantly (41%) lower germination was observed only at 45 DAS. The number of S. hermonthica seedlings attached to and emerged on both sorghum cultivars were also lower in mycorrhizal than in non-mycorrhizal plants. Again, this reduction was more pronounced with S-35 than with CK60-B plants. There was no effect of phosphorus addition on Striga seed germination, attachment or emergence. We hypothesize that the negative effect of mycorrhizal colonization on Striga germination and on subsequent attachment and emergence is mediated through the production of signaling molecules (strigolactones) for AM fungi and parasitic plants.

  13. The roles of arbuscular mycorrhizal fungi (AMF) in phytoremediation and tree-herb interactions in Pb contaminated soil

    SciTech Connect

    Yang, Yurong; Liang, Yan; Han, Xiaozhen; Chiu, Tsan-Yu; Ghosh, Amit; Chen, Hui; Tang, Ming

    2016-02-04

    Understanding the roles of arbuscular mycorrhizal fungi (AMF) in plant interaction is essential for optimizing plant distribution to restore degraded ecosystems. Here, our study investigated the effects of AMF and the presence of legume or grass herbs on phytoremediation with a legume tree, Robinia pseudoacacia, in Pb polluted soil. In monoculture, mycorrhizal dependency of legumes was higher than that of grass, and AMF benefited the plant biomass of legumes but had no effect on grass. Mycorrhizal colonization of plant was enhanced by legume neighbors but inhibited by grass neighbor in co-culture system. N, P, S and Mg concentrations of mycorrhizal legumes were larger than these of non-mycorrhizal legumes. Legume herbs decreased soil pH and thereby increased the Pb concentrations of plants. The neighbor effects of legumes shifted from negative to positive with increasing Pb stress levels, whereas grass provided a negative effect on the growth of legume tree. AMF enhanced the competition but equalized growth of legume-legume under unpolluted and Pb stress conditions, respectively. In conclusion, (1) AMF mediate plant interaction through directly influencing plant biomass, and/or indirectly influencing plant photosynthesis, macronutrient acquisition, (2) legume tree inoculated with AMF and co-planted with legume herbs provides an effective way for Pb phytoremediation.

  14. Mycorrhizal status of Cyperaceae from New Caledonian ultramafic soils: effects of phosphorus availability on arbuscular mycorrhizal colonization of Costularia comosa under field conditions.

    PubMed

    Lagrange, Alexandre; L'huillier, Laurent; Amir, Hamid

    2013-11-01

    Plants from the Cyperaceae family (sedges), usually considered as non-mycorrhizal, constitute almost exclusively the herbaceous stratum of the ultramafic maquis in New Caledonia. These plants are pioneers and are important for the ecological restoration of mined areas. Costularia comosa, one of the most common sedges in this environment, was grown under field conditions on ultramafic soil, fertilized or not with phosphate and/or nitrogen. Results showed that the addition of phosphate to the soil induced a clear increase in mycorrhizal colonization of C. comosa and an increase in arbuscule abundance, reflecting the establishment of a functional mycorrhizal symbiosis. Significant positive correlations were found among mycorrhizal parameters and plant or soil phosphorus concentrations. Nitrogen fertilization did not affect mycorrhizal colonization of C. comosa. The improvement in mycorrhizal colonization by phosphate fertilization did not influence significantly nickel concentrations in the roots and shoots of plants. This study demonstrated that phosphate fertilization of ultramafic soil improved mycorrhizal colonization of C. comosa, with formation of a functional symbiosis under field conditions.

  15. Transcriptomes of Arbuscular Mycorrhizal Fungi and Litchi Host Interaction after Tree Girdling

    PubMed Central

    Shu, Bo; Li, Weicai; Liu, Liqin; Wei, Yongzan; Shi, Shengyou

    2016-01-01

    Trunk girdling can increase carbohydrate content above the girdling site and is an important strategy for inhibiting new shoot growth to promote flowering in cultivated litchi (Litchi chinensis Sonn.). However, girdling inhibits carbohydrate transport to the root in nearly all of the fruit development periods and consequently decreases root absorption. The mechanism through which carbohydrates regulate root development in arbuscular mycorrhiza (AM) remains largely unknown. Carbohydrate content, AM colonization, and transcriptome in the roots were analyzed to elucidate the interaction between host litchi and AM fungi when carbohydrate content decreases. Girdling decreased glucose, fructose, sucrose, quebrachitol, and starch contents in the litchi mycorrhizal roots, thereby reducing AM colonization. RNA-seq achieved approximately 60 million reads of each sample, with an average length of reads reaching 100 bp. Assembly of all the reads of the 30 samples produced 671,316 transcripts and 381,429 unigenes, with average lengths of 780 and 643 bp, respectively. Litchi (54,100 unigenes) and AM fungi unigenes (33,120 unigenes) were achieved through sequence annotation during decreased carbohydrate content. Analysis of differentially expressed genes (DEG) showed that flavonoids, alpha-linolenic acid, and linoleic acid are the main factors that regulate AM colonization in litchi. However, flavonoids may play a role in detecting the stage at which carbohydrate content decreases; alpha-linolenic acid or linoleic acid may affect AM formation under the adaptation process. Litchi trees stimulated the expression of defense-related genes and downregulated symbiosis signal-transduction genes to inhibit new AM colonization. Moreover, transcription factors of the AP2, ERF, Myb, WRKY, bHLH families, and lectin genes altered maintenance of litchi mycorrhizal roots in the post-symbiotic stage for carbohydrate starvation. Similar to those of the litchi host, the E3 ubiquitin ligase complex

  16. Spatio-Temporal Variation of Core and Satellite Arbuscular Mycorrhizal Fungus Communities in Miscanthus giganteus

    PubMed Central

    Barnes, Christopher J.; Burns, Caitlin A.; van der Gast, Christopher J.; McNamara, Niall P.; Bending, Gary D.

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) are a group of obligate plant symbionts which can promote plant nutrition. AMF communities are diverse, but the factors which control their assembly in space and time remain unclear. In this study, the contributions of geographical distance, environmental heterogeneity and time in shaping AMF communities associated with Miscanthus giganteus (a perennial grass originating from south-east Asia) were determined over a 13 months period. In particular, the community was partitioned into core (abundant and persistent taxa) and satellite (taxa with low abundance and persistence) constituents and the drivers of community assembly for each determined. β-diversity was exceptionally low across the 140 m line transects, and there was limited evidence of geographical scaling effects on the composition of the core, satellite or combined communities. However, AMF richness and community composition changed over time associated with fluctuation within both the core and satellite communities. The degree to which AMF community variation was explained by soil properties was consistently higher in the core community than the combined and satellite communities, suggesting that the satellite community had considerable stochasticity associated with it. We suggest that the partitioning of communities into their core and satellite constituents could be employed to enhance the variation explained within microbial community analyses. PMID:27597844

  17. Arbuscular mycorrhizal symbiosis and methyl jasmonate avoid the inhibition of root hydraulic conductivity caused by drought.

    PubMed

    Sánchez-Romera, Beatriz; Ruiz-Lozano, Juan Manuel; Zamarreño, Ángel María; García-Mina, José María; Aroca, Ricardo

    2016-02-01

    Hormonal regulation and symbiotic relationships provide benefits for plants to overcome stress conditions. The aim of this study was to elucidate the effects of exogenous methyl jasmonate (MeJA) application on root hydraulic conductivity (L) of Phaseolus vulgaris plants which established arbuscular mycorrhizal (AM) symbiosis under two water regimes (well-watered and drought conditions). The variation in endogenous contents of several hormones (MeJA, JA, abscisic acid (ABA), indol-3-acetic acid (IAA), salicylic acid (SA)) and the changes in aquaporin gene expression, protein abundance and phosphorylation state were analyzed. AM symbiosis decreased L under well-watered conditions, which was partially reverted by the MeJA treatment, apparently by a drop in root IAA contents. Also, AM symbiosis and MeJA prevented inhibition of L under drought conditions, most probably by a reduction in root SA contents. Additionally, the gene expression of two fungal aquaporins was upregulated under drought conditions, independently of the MeJA treatment. Plant aquaporin gene expression could not explain the behaviour of L. Conversely, evidence was found for the control of L by phosphorylation of aquaporins. Hence, MeJA addition modified the response of L to both AM symbiosis and drought, presumably by regulating the root contents of IAA and SA and the phosphorylation state of aquaporins.

  18. Arbuscular mycorrhizal symbiosis induces strigolactone biosynthesis under drought and improves drought tolerance in lettuce and tomato.

    PubMed

    Ruiz-Lozano, Juan Manuel; Aroca, Ricardo; Zamarreño, Ángel María; Molina, Sonia; Andreo-Jiménez, Beatriz; Porcel, Rosa; García-Mina, José María; Ruyter-Spira, Carolien; López-Ráez, Juan Antonio

    2016-02-01

    Arbuscular mycorrhizal (AM) symbiosis alleviates drought stress in plants. However, the intimate mechanisms involved, as well as its effect on the production of signalling molecules associated with the host plant-AM fungus interaction remains largely unknown. In the present work, the effects of drought on lettuce and tomato plant performance and hormone levels were investigated in non-AM and AM plants. Three different water regimes were applied, and their effects were analysed over time. AM plants showed an improved growth rate and efficiency of photosystem II than non-AM plants under drought from very early stages of plant colonization. The levels of the phytohormone abscisic acid, as well as the expression of the corresponding marker genes, were influenced by drought stress in non-AM and AM plants. The levels of strigolactones and the expression of corresponding marker genes were affected by both AM symbiosis and drought. The results suggest that AM symbiosis alleviates drought stress by altering the hormonal profiles and affecting plant physiology in the host plant. In addition, a correlation between AM root colonization, strigolactone levels and drought severity is shown, suggesting that under these unfavourable conditions, plants might increase strigolactone production in order to promote symbiosis establishment to cope with the stress.

  19. Plant Identity Exerts Stronger Effect than Fertilization on Soil Arbuscular Mycorrhizal Fungi in a Sown Pasture.

    PubMed

    Zheng, Yong; Chen, Liang; Luo, Cai-Yun; Zhang, Zhen-Hua; Wang, Shi-Ping; Guo, Liang-Dong

    2016-10-01

    Arbuscular mycorrhizal (AM) fungi play key roles in plant nutrition and plant productivity. AM fungal responses to either plant identity or fertilization have been investigated. However, the interactive effects of different plant species and fertilizer types on these symbiotic fungi remain poorly understood. We evaluated the effects of the factorial combinations of plant identity (grasses Avena sativa and Elymus nutans and legume Vicia sativa) and fertilization (urea and sheep manure) on AM fungi following 2-year monocultures in a sown pasture field study. AM fungal extraradical hyphal density was significantly higher in E. nutans than that in A. sativa and V. sativa in the unfertilized control and was significantly increased by urea and manure in A. sativa and by manure only in E. nutans, but not by either fertilizers in V. sativa. AM fungal spore density was not significantly affected by plant identity or fertilization. Forty-eight operational taxonomic units (OTUs) of AM fungi were obtained through 454 pyrosequencing of 18S rDNA. The OTU richness and Shannon diversity index of AM fungi were significantly higher in E. nutans than those in V. sativa and/or A. sativa, but not significantly affected by any fertilizer in all of the three plant species. AM fungal community composition was significantly structured directly by plant identity only and indirectly by both urea addition and plant identity through soil total nitrogen content. Our findings highlight that plant identity has stronger influence than fertilization on belowground AM fungal community in this converted pastureland from an alpine meadow.

  20. Bioremediation of adverse impact of cadmium toxicity on Cassia italica Mill by arbuscular mycorrhizal fungi

    PubMed Central

    Hashem, Abeer; Abd_Allah, E.F.; Alqarawi, A.A.; Egamberdieva, Dilfuza

    2015-01-01

    Cassia italica Mill is an important medicinal plant within the family Fabaceae. Pot experiment was conducted to evaluate cadmium stress induced changes in physiological and biochemical attributes in C. italica with and without arbuscular mycorrhizal fungi (AMF). Cadmium stressed plant showed reduced chlorophyll pigment and protein content while AMF inoculation enhanced the chlorophyll and protein content considerably. AMF also ameliorated the cadmium stress induced reduction in total chlorophyll and protein contents by 19.30% and 38.29%, respectively. Cadmium stress enhanced lipid peroxidation while AMF inoculation reduced lipid peroxidation considerably. Increase in proline and phenol content was observed due to cadmium stress and AMF inoculation caused a further increase in proline and phenol content ensuring better growth under stressed conditions. AMF alone also enhanced proline and phenol content. Activity of antioxidant enzymes enhanced under cadmium treatment and AMF inoculation further enhanced their activity thereby strengthening the antioxidant system. Enhanced activities of antioxidants and increased accumulation of osmolytes help plants to avoid damaging impact of oxidative damage. The research has shown that AMF inoculation mitigated the negative impact of stress by reducing the lipid peroxidation and enhancing the antioxidant activity. The present study strongly supports employing AMF as the biological mean for enhancing the cadmium stress tolerance of C. italica. PMID:26858537

  1. A plausible mechanism of biosorption in dual symbioses by vesicular-arbuscular mycorrhizal in plants.

    PubMed

    Azmat, Rafia; Hamid, Neelofer

    2015-03-01

    Dual symbioses of vesicular-arbuscular mycorrhizal (VAM) fungi with growth of Momordica charantia were elucidated in terms of plausible mechanism of biosorption in this article. The experiment was conducted in green house and mixed inoculum of the VAM fungi was used in the three replicates. Results demonstrated that the starch contents were the main source of C for the VAM to builds their hyphae. The increased plant height and leaves surface area were explained in relation with an increase in the photosynthetic rates to produce rapid sugar contents for the survival of plants. A decreased in protein, and amino acid contents and increased proline and protease activity in VAM plants suggested that these contents were the main bio-indicators of the plants under biotic stress. The decline in protein may be due to the degradation of these contents, which later on converted into dextrose where it can easily be absorbed by for the period of symbioses. A mechanism of C chemisorption in relation with physiology and morphology of plant was discussed.

  2. Upscaling Arbuscular Mycorrhizal Symbiosis and Related Agroecosystems Services in Smallholder Farming Systems

    PubMed Central

    Oruru, Marjorie Bonareri; Njeru, Ezekiel Mugendi

    2016-01-01

    Smallholder farming systems form unique ecosystems that can protect beneficial soil biota and form an important source of useful genetic resources. They are characterized by high level of agricultural diversity mainly focused on meeting farmers' needs. Unfortunately, these systems often experience poor crop production mainly associated with poor planning and resource scarcity. Soil fertility is among the primary challenges faced by smallholder farmers, which necessitate the need to come up with affordable and innovative ways of replenishing soils. One such way is the use of microbial symbionts such as arbuscular mycorrhizal fungi (AMF), a beneficial group of soil microbiota that form symbiotic associations with majority of cultivated crops and play a vital role in biological soil fertility, plant nutrition, and protection. AMF can be incorporated in smallholder farming systems to help better exploit chemical fertilizers inputs which are often unaffordable to many smallholder farmers. The present review highlights smallholder farming practices that could be innovatively redesigned to increase AMF symbiosis and related agroecosystem services. Indeed, the future of global food security depends on the success of smallholder farming systems, whose crop productivity depends on the services provided by well-functioning ecosystems, including soil fertility. PMID:26942194

  3. Production of Vesicular-Arbuscular Mycorrhizal Fungus Inoculum in Aeroponic Culture †

    PubMed Central

    Hung, Ling-Ling L.; Sylvia, David M.

    1988-01-01

    Bahia grass (Paspalum notatum) and industrial sweet potato (Ipomoea batatas) colonized by Glomus deserticola, G. etunicatum, and G. intraradices were grown in aeroponic cultures. After 12 to 14 weeks, all roots were colonized by the inoculated vesicular-arbuscular mycorrhizal fungi. Abundant vesicles and arbuscules formed in the roots, and profuse sporulation was detected intra-and extraradically. Within each fungal species, industrial sweet potato contained significantly more roots and spores per plant than bahia grass did, although the percent root colonization was similar for both hosts. Mean percent root colonization and sporulation per centimeter of colonized root generally increased with time, although with some treatments colonization declined by week 14. Spore production ranged from 4 spores per cm of colonized root for G. etunicatum to 51 spores per cm for G. intraradices. Infectivity trials with root inocula resulted in a mean of 38, 45, and 28% of bahia grass roots colonized by G. deserticola, G. etunicatum, and G. intraradices, respectively. The germination rate of G. etunicatum spores produced in soil was significantly higher than that produced in aeroponic cultures (64% versus 46%) after a 2-week incubation at 28°C. However, infectivity studies comparing G. etunicatum spores from soil and aeroponic culture indicated no biological differences between the spore sources. Aeroponically produced G. deserticola and G. etunicatum inocula retained their infectivity after cold storage (4°C) in either sterile water or moist vermiculite for at least 4 and 9 months, respectively. PMID:16347548

  4. Potato-associated arbuscular mycorrhizal fungal communities in the Peruvian Andes.

    PubMed

    Senés-Guerrero, Carolina; Torres-Cortés, Gloria; Pfeiffer, Stefan; Rojas, Mercy; Schüßler, Arthur

    2014-08-01

    The world's fourth largest food crop, potato, originates in the Andes. Here, the community composition of arbuscular mycorrhizal fungi (AMF) associated with potato in Andean ecosystems is described for the first time. AMF were studied in potato roots and rhizosphere soil at four different altitudes from 2,658 to 4,075 m above mean sea level (mamsl) and in three plant growth stages (emergence, flowering, and senescence). AMF species were distinguished by sequencing an approx. 1,500 bp nuclear rDNA region. Twenty species of AMF were identified, of which 12 came from potato roots and 15 from rhizosphere soil. Seven species were found in both roots and soil. Interestingly, altitude affected species composition with the highest altitude exhibiting the greatest species diversity. The three most common colonizers of potato roots detected were Funneliformis mosseae, an unknown Claroideoglomus sp., and Rhizophagus irregularis. Notably, the potato-associated AMF diversity observed in this Andean region is much higher than that reported for potato in other ecosystems. Potato plants were colonized by diverse species from 8 of the 11 Glomeromycota families. Identification of the AMF species is important for their potential use in sustainable management practices to improve potato production in the Andean region.

  5. Biology and evolution of arbuscular mycorrhizal symbiosis in the light of genomics.

    PubMed

    Kamel, Laurent; Keller-Pearson, Michelle; Roux, Christophe; Ané, Jean-Michel

    2017-01-01

    531 I. 531 II. 532 III. 532 IV. 534 V. 534 535 References 535 SUMMARY: Arbuscular mycorrhizal (AM) fungi associate with the vast majority of land plants, providing mutual nutritional benefits and protecting hosts against biotic and abiotic stresses. Significant progress was made recently in our understanding of the genomic organization, the obligate requirements, and the sexual nature of these fungi through the release and subsequent mining of genome sequences. Genomic and genetic approaches also improved our understanding of the signal repertoire used by AM fungi and their plant hosts to recognize each other for the initiation and maintenance of this association. Evolutionary and bioinformatic analyses of host and nonhost plant genomes represent novel ways with which to decipher host mechanisms controlling these associations and shed light on the stepwise acquisition of this genetic toolkit during plant evolution. Mining fungal and plant genomes along with evolutionary and genetic approaches will improve understanding of these symbiotic associations and, in the long term, their usefulness in agricultural settings.

  6. Global sampling of plant roots expands the described molecular diversity of arbuscular mycorrhizal fungi.

    PubMed

    Öpik, Maarja; Zobel, Martin; Cantero, Juan J; Davison, John; Facelli, José M; Hiiesalu, Inga; Jairus, Teele; Kalwij, Jesse M; Koorem, Kadri; Leal, Miguel E; Liira, Jaan; Metsis, Madis; Neshataeva, Valentina; Paal, Jaanus; Phosri, Cherdchai; Põlme, Sergei; Reier, Ülle; Saks, Ülle; Schimann, Heidy; Thiéry, Odile; Vasar, Martti; Moora, Mari

    2013-07-01

    We aimed to enhance understanding of the molecular diversity of arbuscular mycorrhizal fungi (AMF) by building a new global dataset targeting previously unstudied geographical areas. In total, we sampled 96 plant species from 25 sites that encompassed all continents except Antarctica. AMF in plant roots were detected by sequencing the nuclear SSU rRNA gene fragment using either cloning followed by Sanger sequencing or 454-sequencing. A total of 204 AMF phylogroups (virtual taxa, VT) were recorded, increasing the described number of Glomeromycota VT from 308 to 341 globally. Novel VT were detected from 21 sites; three novel but nevertheless widespread VT (Glomus spp. MO-G52, MO-G53, MO-G57) were recorded from six continents. The largest increases in regional VT number were recorded in previously little-studied Oceania and in the boreal and polar climatic zones - this study providing the first molecular data from the latter. Ordination revealed differences in AM fungal communities between different continents and climatic zones, suggesting that both biogeographic history and environmental conditions underlie the global variation of those communities. Our results show that a considerable proportion of Glomeromycota diversity has been recorded in many regions, though further large increases in richness can be expected in remaining unstudied areas.

  7. Genetic variation in the response of the weed Ruellia nudiflora (Acanthaceae) to arbuscular mycorrhizal fungi.

    PubMed

    Ramos-Zapata, José Alberto; Campos-Navarrete, María José; Parra-Tabla, Víctor; Abdala-Roberts, Luis; Navarro-Alberto, Jorge

    2010-04-01

    The main goal of this work was to test for plant genetic variation in the phenotypic plasticity response of the weed Ruellia nudiflora to arbuscular mycorrhizal (AM) fungi inoculation. We collected plants in the field, kept them under homogeneous conditions inside a nursery, and then collected seeds from these parent plants to generate five inbred lines (i.e., genetic families). Half of the plants of each inbred line were inoculated with AM fungi while the other half were not (controls); a fully crossed experimental design was then used to test for the effects of treatment (with or without AM fungi inoculation) and inbred line (genetic family). For each plant, we recorded the number of leaves produced and the number of days it survived during a 2-month period. Results showed a strong positive treatment effect (plastic response to AM fungi inoculation) for leaf production and survival. Moreover, in terms of survival, the treatment effect differed between genetic families (significant genetic family by treatment interaction). These findings indicate that the positive effect of AM fungi on plant survival (and potentially also growth) differs across plant genotypes and that such condition may contribute to R. nudiflora's capacity to colonize new environments.

  8. Arbuscular mycorrhizal status of spring ephemerals in the desert ecosystem of Junggar Basin, China.

    PubMed

    Shi, Z Y; Feng, G; Christie, P; Li, X L

    2006-06-01

    A survey was made of the arbuscular mycorrhizal (AM) status of 73 spring ephemeral plant species that grow in the desert ecosystem of Junggar Basin, northwest China. The proportion of AM colonization ranged from 7 to 73% with a mean value of 30%. A total of 65 plant species studied were AM with coils/arbuscules or vesicles and the remaining eight species were possibly AM with no coils/arbuscules or vesicles but with fungal mycelia in the root cortex. AM fungal spores were isolated from rhizosphere samples of all 73 plant species and identified. The mean spore density was 22 per 20 ml of air-dried soil, ranging from 0 to 120. Colonization and spore density of perennials were slightly higher than of annuals and varied among different plant families. A total of 603 AM fungal spore (or sporocarp) specimens were isolated belonging to six genera, Acaulospora, Archaeopora, Entrophospora, Glomus, Paraglomus, and Scutellospora; Glomus was the dominant genus. We conclude that spring ephemerals may be highly dependent on AM associations for survival in the very infertile and arid soils of this desert ecosystem.

  9. Reducing nitrogen runoff from paddy fields with arbuscular mycorrhizal fungi under different fertilizer regimes.

    PubMed

    Zhang, Shujuan; Wang, Li; Ma, Fang; Zhang, Xue; Fu, Dafang

    2016-08-01

    Nitrogen (N) runoff from paddy fields serves as one of the main sources of water pollution. Our aim was to reduce N runoff from paddy fields by fertilizer management and inoculation with arbuscular mycorrhizal fungi (AMF). In northeast China, Shuangcheng city in Heilongjiang province, a field experiment was conducted, using rice provided with 0%, 20%, 40%, 60%, 80%, and 100% of the local norm of fertilization (including N, phosphorus and potassium), with or without inoculation with Glomus mosseae. The volume, concentrations of total N (TN), dissolved N (DN) and particulate N (PN) of runoff water were measured. We found that the local norm of fertilization led to 18.9kg/ha of N runoff during rice growing season, with DN accounting for 60%-70%. We also found that reduction in fertilization by 20% cut down TN runoff by 8.2% while AMF inoculation decreased N runoff at each fertilizer level and this effect was inhibited by high fertilization. The combination of inoculation with AMF and 80% of the local norm of fertilization was observed to reduce N runoff by 27.2%. Conclusively, we suggested that the contribution of AMF inoculation combined with decreasing fertilization should get more attention to slow down water eutrophication by reducing N runoff from paddy fields.

  10. Root and arbuscular mycorrhizal mycelial interactions with soil microorganisms in lowland tropical forest.

    PubMed

    Nottingham, Andrew T; Turner, Benjamin L; Winter, Klaus; Chamberlain, Paul M; Stott, Andrew; Tanner, Edmund V J

    2013-07-01

    Tropical forests have high rates of soil carbon cycling, but little information is available on how roots, arbuscular mycorrhizal fungi (AMF), and free-living microorganisms interact and influence organic matter mineralization in these ecosystems. We used mesh ingrowth cores and isotopic tracers in phospholipid fatty acid biomarkers to investigate the effects of roots and AMF mycelia on (1) microbial community composition, microbial carbon utilization, and hydrolytic enzyme activities for large, potted tropical trees and (2) enzyme activities and litter mass loss in a lowland tropical forest. Under the tropical tree, plant-derived carbon was incorporated predominantly into bacterial groups in both rhizosphere and AMF-only soils. Gram-positive bacteria incorporated additional soil-derived carbon in rhizosphere soils, which also contained the highest microbial biomass. For hydrolytic enzymes, β-glucosidase and N-acetyl β-glucosaminidase activities were highest in rhizosphere soils, while phosphomonoesterase activity was highest in AMF-only soil. In the forest, leaf litter mass loss was increased by the presence of roots, but not by the presence of AMF mycelia only. Root-microbial interactions influenced organic matter cycling, with evidence for rhizosphere priming and accelerated leaf litter decomposition in the presence of roots. Although AMF mycelia alone did not stimulate organic matter mineralization, they were a conduit of carbon to other soil microorganisms.

  11. Effect of rice cultivation systems on indigenous arbuscular mycorrhizal fungal community structure.

    PubMed

    Watanarojanaporn, Nantida; Boonkerd, Nantakorn; Tittabutr, Panlada; Longtonglang, Aphakorn; Young, J Peter W; Teaumroong, Neung

    2013-01-01

    Arbuscular mycorrhizal fungi (AMF) in an agricultural ecosystem are necessary for proper management of beneficial symbiosis. Here we explored how the patterns of the AMF community in rice roots were affected by rice cultivation systems (the system of rice intensification [SRI] and the conventional rice cultivation system [CS]), and by compost application during growth stages. Rice plants harvested from SRI-managed plots exhibited considerably higher total biomass, root dry weight, and seed fill than those obtained from conventionally managed plots. Our findings revealed that all AMF sequences observed from CS plots belonged (only) to the genus Glomus, colonizing in rice roots grown under this type of cultivation, while rice roots sown in SRI showed sequences belonging to both Glomus and Acaulospora. The AMF community was compared between the different cultivation types (CS and SRI) and compost applications by principle component analysis. In all rice growth stages, AMF assemblages of CS management were not separated from those of SRI management. The distribution of AMF community composition based on T-RFLP data showed that the AMF community structure was different among four cultivation systems, and there was a gradual increase of Shannon-Weaver indices of diversity (H') of the AMF community under SRI during growth stages. The results of this research indicated that rice grown in SRI-managed plots had more diverse AMF communities than those grown in CS plots.

  12. Evaluation of commercial arbuscular mycorrhizal inocula in a sand/peat medium.

    PubMed

    Tarbell, T J; Koske, R E

    2007-12-01

    Eight commercial inocula of arbuscular mycorrhizal fungi (AMF) were tested for their ability to colonize plant roots in the sand/peat medium specified by the U.S. Golf Association for use in putting greens. Using the standard assay for potency of inocula (Zea mays grown for 6 weeks in containers), inocula were added at the rate recommended by the manufacturer as well as at five and ten times the recommended rate. To ensure that growth conditions were conducive to AM formation, a soil-based inoculum of native AMF also was assessed for inoculum potential. Only three of the commercial inocula formed mycorrhizas when used at the recommended rate, and the extent of colonization ranged from 0.4 to 8%. Increasing the amount of inoculum resulted in colonization levels of 8.6 to 72.5% at the highest rate (10x). Mean colonization using the native AMF was 60%. One inoculum that did not form mycorrhizas at the recommended rate or at 5x produced 8.6% colonization at 10x. An inoculum that did not produce mycorrhizas at any application rate did contain a fungus tentatively identified as a root pathogen (Olpidium brassicae) that colonized the corn roots. The failure of five of the eight commercial inocula to colonize roots when applied at the recommended rate suggests that preliminary trials should be made before commercial AMF inocula are used in important plantings.

  13. A dipeptide transporter from the arbuscular mycorrhizal fungus Rhizophagus irregularis is upregulated in the intraradical phase

    PubMed Central

    Belmondo, Simone; Fiorilli, Valentina; Pérez-Tienda, Jacob; Ferrol, Nuria; Marmeisse, Roland; Lanfranco, Luisa

    2014-01-01

    Arbuscular mycorrhizal fungi (AMF), which form an ancient and widespread mutualistic symbiosis with plants, are a crucial but still enigmatic component of the plant micro biome. Nutrient exchange has probably been at the heart of the success of this plant-fungus interaction since the earliest days of plants on land. To characterize genes from the fungal partner involved in nutrient exchange, and presumably important for the functioning of the AM symbiosis, genome-wide transcriptomic data obtained from the AMF Rhizophagus irregularis were exploited. A gene sequence, showing amino acid sequence and transmembrane domains profile similar to members of the PTR2 family of fungal oligopeptide transporters, was identified and called RiPTR2. The functional properties of RiPTR2 were investigated by means of heterologous expression in Saccharomyces cerevisiae mutants defective in either one or both of its di/tripeptide transporter genes PTR2 and DAL5. These assays showed that RiPTR2 can transport dipeptides such as Ala-Leu, Ala-Tyr or Tyr-Ala. From the gene expression analyses it seems that RiPTR2 responds to different environmental clues when the fungus grows inside the root and in the extraradical phase. PMID:25232358

  14. Arbuscular mycorrhizal fungi reduce the differences in competitiveness between dominant and subordinate plant species.

    PubMed

    Mariotte, Pierre; Meugnier, Claire; Johnson, David; Thébault, Aurélie; Spiegelberger, Thomas; Buttler, Alexandre

    2013-05-01

    In grassland communities, plants can be classified as dominants or subordinates according to their relative abundances, but the factors controlling such distributions remain unclear. Here, we test whether the presence of the arbuscular mycorrhizal (AM) fungus Glomus intraradices affects the competitiveness of two dominant (Taraxacum officinale and Agrostis capillaris) and two subordinate species (Prunella vulgaris and Achillea millefolium). Plants were grown in pots in the presence or absence of the fungus, in monoculture and in mixtures of both species groups with two and four species. In the absence of G. intraradices, dominants were clearly more competitive than subordinates. In inoculated pots, the fungus acted towards the parasitic end of the mutualism-parasitism continuum and had an overall negative effect on the growth of the plant species. However, the negative effects of the AM fungus were more pronounced on dominant species reducing the differences in competitiveness between dominant and subordinate species. The effects of G. intraradices varied with species composition highlighting the importance of plant community to mediate the effects of AM fungi. Dominant species were negatively affected from the AM fungus in mixtures, while subordinates grew identically with and without the fungus. Therefore, our findings predict that the plant dominance hierarchy may flatten out when dominant species are more reduced than subordinate species in an unfavourable AM fungal relationship (parasitism).

  15. Impact of alien pines on local arbuscular mycorrhizal fungal communities-evidence from two continents.

    PubMed

    Gazol, Antonio; Zobel, Martin; Cantero, Juan José; Davison, John; Esler, Karen J; Jairus, Teele; Öpik, Maarja; Vasar, Martti; Moora, Mari

    2016-06-01

    The introduction of alien plants can influence biodiversity and ecosystems. However, its consequences for soil microbial communities remain poorly understood. We addressed the impact of alien ectomycorrhizal (EcM) pines on local arbuscular mycorrhizal (AM) fungal communities in two regions with contrasting biogeographic histories: in South Africa, where no native EcM plant species are present; and in Argentina, where EcM trees occur naturally. The effect of alien pines on AM fungal communities differed between these regions. In South Africa, plantations of alien EcM pines exhibited lower AM fungal richness and significantly altered community composition, compared with native fynbos. In Argentina, the richness and composition of local AM fungal communities were similar in plantations of alien EcM pines and native forest. However, the presence of alien pines resulted in slight changes to the phylogenetic structure of root AM fungal communities in both regions. In pine clearcut areas in South Africa, the richness and composition of AM fungal communities were intermediate between the native fynbos and the alien pine plantation, which is consistent with natural regeneration of former AM fungal communities following pine removal. We conclude that the response of local AM fungal communities to alien EcM pines differs between biogeographic regions with different histories of species coexistence.

  16. Phylogenetically structured traits in root systems influence arbuscular mycorrhizal colonization in woody angiosperms

    DOE PAGES

    Valverde-Barrantes, Oscar J.; Horning, Amber L.; Smemo, Kurt A.; ...

    2016-02-10

    In this study, there is little quantitative information about the relationship between root traits and the extent of arbuscular mycorrhizal fungi (AMF) colonization. We expected that ancestral species with thick roots will maximize AMF habitat by maintaining similar root traits across root orders (i.e., high root trait integration), whereas more derived species are expected to display a sharp transition from acquisition to structural roots. Moreover, we hypothesized that interspecific morphological differences rather than soil conditions will be the main driver of AMF colonization We analyzed 14 root morphological and chemical traits and AMF colonization rates for the first three rootmore » orders of 34 temperate tree species grown in two common gardens. We also collected associated soil to measure the effect of soil conditions on AMF colonization Results Thick-root magnoliids showed less variation in root traits along root orders than more-derived angiosperm groups. Variation in stele:root diameter ratio was the best indicator of AMF colonization within and across root orders. Root functional traits rather than soil conditions largely explained the variation in AMF colonization among species. In conclusion, not only the traits of first order but the entire structuring of the root system varied among plant lineages, suggesting alternative evolutionary strategies of resource acquisition. Understanding evolutionary pathways in below ground organs could open new avenues to understand tree species influence on soil carbon and nutrient cycling.« less

  17. Transition Metal Transport in Plants and Associated Endosymbionts: Arbuscular Mycorrhizal Fungi and Rhizobia.

    PubMed

    González-Guerrero, Manuel; Escudero, Viviana; Saéz, Ángela; Tejada-Jiménez, Manuel

    2016-01-01

    Transition metals such as iron, copper, zinc, or molybdenum are essential nutrients for plants. These elements are involved in almost every biological process, including photosynthesis, tolerance to biotic and abiotic stress, or symbiotic nitrogen fixation. However, plants often grow in soils with limiting metallic oligonutrient bioavailability. Consequently, to ensure the proper metal levels, plants have developed a complex metal uptake and distribution system, that not only involves the plant itself, but also its associated microorganisms. These microorganisms can simply increase metal solubility in soils and making them more accessible to the host plant, as well as induce the plant metal deficiency response, or directly deliver transition elements to cortical cells. Other, instead of providing metals, can act as metal sinks, such as endosymbiotic rhizobia in legume nodules that requires relatively large amounts to carry out nitrogen fixation. In this review, we propose to do an overview of metal transport mechanisms in the plant-microbe system, emphasizing the role of arbuscular mycorrhizal fungi and endosymbiotic rhizobia.

  18. Strigolactones, host recognition signals for root parasitic plants and arbuscular mycorrhizal fungi, from Fabaceae plants.

    PubMed

    Yoneyama, Kaori; Xie, Xiaonan; Sekimoto, Hitoshi; Takeuchi, Yasutomo; Ogasawara, Shin; Akiyama, Kohki; Hayashi, Hideo; Yoneyama, Koichi

    2008-07-01

    Both root parasitic plants and arbuscular mycorrhizal (AM) fungi take advantage of strigolactones, released from plant roots as signal molecules in the initial communication with host plants, in order to commence parasitism and mutualism, respectively. In this study, strigolactones in root exudates from 12 Fabaceae plants, including hydroponically grown white lupin (Lupinus albus), a nonhost of AM fungi, were characterized by comparing retention times of germination stimulants on reverse-phase high-performance liquid chromatography (HPLC) with those of standards and by using tandem mass spectrometry (LC/MS/MS). All the plant species examined were found to exude known strigolactones, such as orobanchol, orobanchyl acetate, and 5-deoxystrigol, suggesting that these strigolactones are widely distributed in the Fabaceae. It should be noted that even the nonmycotrophic L. albus exuded orobanchol, orobanchyl acetate, 5-deoxystrigol, and novel germination stimulants. By contrast to the mycotrophic Fabaceae plant Trifolium pratense, in which phosphorus deficiency promoted strigolactone exudation, neither phosphorus nor nitrogen deficiency increased exudation of these strigolactones in L. albus. Therefore, the regulation of strigolactone production and/or exudation seems to be closely related to the nutrient acquisition strategy of the plants.

  19. The Scion/Rootstock Genotypes and Habitats Affect Arbuscular Mycorrhizal Fungal Community in Citrus

    PubMed Central

    Song, Fang; Pan, Zhiyong; Bai, Fuxi; An, Jianyong; Liu, Jihong; Guo, Wenwu; Bisseling, Ton; Deng, Xiuxin; Xiao, Shunyuan

    2015-01-01

    Citrus roots have rare root hairs and thus heavily depend on arbuscular mycorrhizal fungi (AMF) for mineral nutrient uptake. However, the AMF community structure of citrus is largely unknown. By using 454-pyrosequencing of 18S rRNA gene fragment, we investigated the genetic diversity of AMF colonizing citrus roots, and evaluated the impact of habitats and rootstock and scion genotypes on the AMF community structure. Over 7,40,000 effective sequences were obtained from 77 citrus root samples. These sequences were assigned to 75 AMF virtual taxa, of which 66 belong to Glomus, highlighting an absolute dominance of this AMF genus in symbiosis with citrus roots. The citrus AMF community structure is significantly affected by habitats and host genotypes. Interestingly, our data suggests that the genotype of the scion exerts a greater impact on the AMF community structure than that of the rootstock where the physical root-AMF association occurs. This study not only provides a comprehensive assessment for the community composition of the AMF in citrus roots under different conditions, but also sheds novel insights into how the AMF community might be indirectly influenced by the spatially separated yet metabolically connected partner—the scion—of the grafted citrus tree. PMID:26648932

  20. Arbuscular mycorrhizal fungi enhance soil carbon sequestration in the coalfields, northwest China

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Gang; Bi, Yin-Li; Jiang, Bin; Zhakypbek, Yryszhan; Peng, Su-Ping; Liu, Wen-Wen; Liu, Hao

    2016-10-01

    Carbon storage is affected by photosynthesis (Pn) and soil respiration (Rs), which have been studied extensively in natural and agricultural systems. However, the effects of Pn and Rs on carbon storages in the presence of arbuscular mycorrhizal fungi (AMF) in coalfields remain unclear. A field experiment was established in 2014 in Shendong coal mining subsidence area. The treatments comprised two inoculation levels (inoculated with or without 100 g AMF inoculums per seedlings) and four plant species [wild cherry (Prunus discadenia Koebne L.), cerasus humilis (Prunus dictyneura Diels L.), shiny leaf Yellow horn (Xanthoceras sorbifolium Bunge L.) and apricot (Armeniaca sibirica L.)]. AMF increased Pn of four species ranging from 15.3% to 33.1% and carbon storage, averaged by 17.2% compared to controls. Soil organic carbon (OC), easily extractable glomalin-relation soil protein (EE-GRSP), and total glomalin-relation soil protein (T-GRSP) were significantly increased by AMF treatment. The effect of AMF on the sensitivity of Rs depended on soil temperature. The results highlighted the exponential models to explain the responses of Rs to soil temperature, and for the first time quantified AMF caused carbon sequestration and Rs. Thus, to our knowledge, AMF is beneficial to ecosystems through facilitating carbon conservation in coalfield soils.

  1. Arbuscular mycorrhizal fungi in Mimosa tenuiflora (Willd.) Poir from Brazilian semi-arid.

    PubMed

    de Souza, Tancredo Augusto Feitosa; Rodriguez-Echeverría, Susana; de Andrade, Leonaldo Alves; Freitas, Helena

    2016-01-01

    Many plant species from Brazilian semi-arid present arbuscular mycorrhizal fungi (AMF) in their rhizosphere. These microorganisms play a key role in the establishment, growth, survival of plants and protection against drought, pathogenic fungi and nematodes. This study presents a quantitative analysis of the AMF species associated with Mimosa tenuiflora, an important native plant of the Caatinga flora. AMF diversity, spore abundance and root colonization were estimated in seven sampling locations in the Ceará and Paraíba States, during September of 2012. There were significant differences in soil properties, spore abundance, percentage of root colonization, and AMF diversity among sites. Altogether, 18 AMF species were identified, and spores of the genera Acaulospora, Claroideoglomus, Dentiscutata, Entrophospora, Funneliformis, Gigaspora, Glomus, Racocetra, Rhizoglomus and Scutellospora were observed. AMF species diversity and their spore abundance found in M. tenuiflora rhizosphere shown that this native plant species is an important host plant to AMF communities from Brazilian semi-arid region. We concluded that: (a) during the dry period and in semi-arid conditions, there is a high spore production in M. tenuiflora root zone; and (b) soil properties, as soil pH and available phosphorous, affect AMF species diversity, thus constituting key factors for the similarity/dissimilarity of AMF communities in the M. tenuiflora root zone among sites.

  2. [Photosynthetic parameters and physiological indexes of Paris polyphylla var. yunnanensis influenced by arbuscular mycorrhizal fungi].

    PubMed

    Wei, Zheng-xin; Guo, Dong-qin; Li, Hai-feng; Ding, Bo; Zhang, Jie; Zhou, Nong; Yu, Jie

    2015-10-01

    Through potted inoculation test at room temperature and indoor analysis, the photosynthetic parameters and physiological and biochemical indexes of Paris polyphylla var. yunnanensis were observed after 28 arbuscular mycorrhizal (AM) fungi were injected into the P. polyphylla var. yunnanensis growing in a sterile soil environment. The results showed that AM fungi established a good symbiosis with P. polyphylla var. yunnanensis. The AM fungi influenced the photosynthetic parameters and physiological and biochemical indexes of P. polyphylla var. yunnanensis. And the influences were varied depending on different AM fungi. The application of AM fungi improved photosynthesis intensity of P. polyphylla var. yunnanensis mesophyll cells, the contents of soluble protein and soluble sugar, protective enzyme activity of P. polyphylla var. yunnanensis leaf, which was beneficial to resist the adverse environment and promote the growth of P. polyphylla var. yunnanensis. Otherwise, there was a certain mutual selectivity between P. polyphylla var. yunnanensis and AM fungi. From the comprehensive effect of inoculation, Racocetra coralloidea, Scutellospora calospora, Claroideoglomus claroideum, S. pellucida and Rhizophagus clarus were the most suitable AM fungi to P. polyphylla var. yunnanensis when P. polyphylla var. yunnanensis was planted in the field.

  3. [Characteristics of arbuscular mycorrhizal fungal diversity and functions in saline-alkali land].

    PubMed

    Yang, Hai-xia; Guo, Shao-xia; Liu, Run-jin

    2015-01-01

    Arbuscular mycorrhizal (AM) fungi, widely distributing in various terrestrial ecosys- tems, are one of the important functional biotic components in soil habitats and play a vital role in improving soil evolution, maintaining soil health and sustainable productivity. Saline-alkali soil is a special habitat affecting plant growth and grain yield. Under the influence of a series of factors, such as human activities on the nature, S and N deposition, ozone, greenhouse effect, climate anomalies, and alien species invasions etc., soil salinization, biodiversity and functions of saline farmlands may be greatly affected, which could consequently influence agricultural production and the sustainable development of ecosystems. Followed by an introduction of the changing characteristics of saline soil area and the secondary salinization under the background of global changes, the present review mainly discussed the changing features of diversity and functions of AM fungi in saline habitats, summarized the factors influencing AM fungal diversity and functions, and the factors' changing characters under the global changes, in order to provide new ideas and ways in further elucidating the position, role and function of AM fungi in saline soil, and in strengthening saline farmland remediation in response to global changes.

  4. The Use of Arbuscular Mycorrhizal Fungi to Improve Strawberry Production in Coir Substrate

    PubMed Central

    Robinson Boyer, Louisa; Feng, Wei; Gulbis, Natallia; Hajdu, Klara; Harrison, Richard J.; Jeffries, Peter; Xu, Xiangming

    2016-01-01

    Strawberry is an important fruit crop within the UK. To reduce the impact of soil-borne diseases and extend the production season, more than half of the UK strawberry production is now in substrate (predominantly coir) under protection. Substrates such as coir are usually depleted of microbes including arbuscular mycorrhizal fungi (AMF) and consequently the introduction of beneficial microbes is likely to benefit commercial cropping systems. Inoculating strawberry plants in substrate other than coir has been shown to increase plants tolerance to soil-borne pathogens and water stress. We carried out studies to investigate whether AMF could improve strawberry production in coir under low nitrogen input and regulated deficit irrigation. Application of AMF led to an appreciable increase in the size and number of class I fruit, especially under either deficient irrigation or low nitrogen input condition. However, root length colonization by AMF was reduced in strawberry grown in coir compared to soil and Terragreen. Furthermore, the appearance of AMF colonizing strawberry and maize roots grown in coir showed some physical differences from the structure in colonized roots in soil and Terragreen: the colonization structure appeared to be more compact and smaller in coir. PMID:27594859

  5. Arbuscular mycorrhizal fungi associated with Populus-Salix stands in a semiarid riparian ecosystem

    USGS Publications Warehouse

    Beauchamp, Vanessa B.; Stromberg, J.C.; Stutz, J.C.

    2006-01-01

    ??? This study examined the activity, species richness, and species composition of the arbuscular mycorrhizal fungal (AMF) community of Populus-Salix stands on the Verde River (Arizona, USA), quantified patterns of AMF richness and colonization along complex floodplain gradients, and identified environmental variables responsible for structuring the AMF community. ??? Samples from 61 Populus-Salix stands were analyzed for AMF and herbaceous composition, AMF colonization, gravimetric soil moisture, soil texture, per cent organic matter, pH, and concentrations of nitrate, bicarbonate phosphorus and exchangeable potassium. ??? AMF species richness declined with stand age and distance from and elevation above the channel and was positively related to perennial species cover and richness and gravimetric soil moisture. Distance from and elevation above the active channel, forest age, annual species cover, perennial species richness, and exchangeable potassium concentration all played a role in structuring the AMF community in this riparian area. ??? Most AMF species were found across a wide range of soil conditions, but a subset of species tended to occur more often in hydric areas. This group of riparian affiliate AMF species includes several not previously encountered in the surrounding Sonoran desert. ?? New Phytologist (2006).

  6. Nitrogen-fixing bacteria, arbuscular mycorrhizal fungi, and the productivity and structure of prairie grassland communities.

    PubMed

    Bauer, Jonathan T; Kleczewski, Nathan M; Bever, James D; Clay, Keith; Reynolds, Heather L

    2012-12-01

    Due to their complementary roles in meeting plant nutritional needs, arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (N(2)-fixers) may have synergistic effects on plant communities. Using greenhouse microcosms, we tested the effects of AMF, N(2)-fixers (symbiotic: rhizobia, and associative: Azospirillum brasilense), and their potential interactions on the productivity, diversity, and species composition of diverse tallgrass prairie communities and on the productivity of Panicum virgatum in monoculture. Our results demonstrate the importance of AMF and N(2)-fixers as drivers of plant community structure and function. In the communities, we found a positive effect of AMF on diversity and productivity, but a negative effect of N(2)-fixers on productivity. Both AMF and N(2)-fixers affected relative abundances of species. AMF shifted the communities from dominance by Elymus canadensis to Sorghastrum nutans, and seven other species increased in abundance with AMF, accounting for the increased diversity. N(2)-fixers led to increases in Astragalus canadensis and Desmanthus illinoense, two legumes that likely benefited from the presence of the appropriate rhizobia symbionts. Sorghastrum nutans declined 44 % in the presence of N(2)-fixers, with the most likely explanation being increased competition from legumes. Panicum monocultures were more productive with AMF, but showed no response to N(2)-fixers, although inference was constrained by low Azospirillum treatment effectivity. We did not find interactions between AMF and N(2)-fixers in communities or Panicum monocultures, indicating that short-term effects of these microbial functional groups are additive.

  7. Upscaling Arbuscular Mycorrhizal Symbiosis and Related Agroecosystems Services in Smallholder Farming Systems.

    PubMed

    Oruru, Marjorie Bonareri; Njeru, Ezekiel Mugendi

    2016-01-01

    Smallholder farming systems form unique ecosystems that can protect beneficial soil biota and form an important source of useful genetic resources. They are characterized by high level of agricultural diversity mainly focused on meeting farmers' needs. Unfortunately, these systems often experience poor crop production mainly associated with poor planning and resource scarcity. Soil fertility is among the primary challenges faced by smallholder farmers, which necessitate the need to come up with affordable and innovative ways of replenishing soils. One such way is the use of microbial symbionts such as arbuscular mycorrhizal fungi (AMF), a beneficial group of soil microbiota that form symbiotic associations with majority of cultivated crops and play a vital role in biological soil fertility, plant nutrition, and protection. AMF can be incorporated in smallholder farming systems to help better exploit chemical fertilizers inputs which are often unaffordable to many smallholder farmers. The present review highlights smallholder farming practices that could be innovatively redesigned to increase AMF symbiosis and related agroecosystem services. Indeed, the future of global food security depends on the success of smallholder farming systems, whose crop productivity depends on the services provided by well-functioning ecosystems, including soil fertility.

  8. Diversity of arbuscular mycorrhizal fungus populations in heavy-metal-contaminated soils

    SciTech Connect

    Del Val, C.; Barea, J.M.; Azcon-Aguilar, C.

    1999-02-01

    High concentrations of heavy metals have been shown to adversely affect the size, diversity, and activity of microbial populations in soil. The aim of this work was to determine how the diversity of arbuscular mycorrhizal (AM) fungi is affected by the addition of sewage-amended sludge containing heavy metals in a long-term experiment. Due to the reduced number of indigenous AM fungal (AMF) propagules in the experimental soils, several host plants with different life cycles were used to multiply indigenous fungi. Six AMF ecotypes were found in the experimental soils, showing consistent differences with regard to their tolerance to the presence of heavy metals. AMF ecotypes ranged from very sensitive to the presence of metals to relatively tolerant to high rates of heavy metals in soil. Total AMF spore numbers decreased with increasing amounts of heavy metals in the soil. However, species richness and diversity as measured by the Shannon-Wiener index increased in soils receiving intermediate rates of sludge contamination but decreased in soils receiving the highest rate of heavy-metal-contaminated sludge. Relative densities of most AMF species were also significantly influenced by soil treatments. Host plant species exerted a selective influence on AMF population size and diversity. The authors conclude based on the results of this study that size and diversity of AMF populations were modified in metal-polluted soils, even in those with metal concentrations that were below the upper limits accepted by the European Union for agricultural soils.

  9. Organic amendments increase phylogenetic diversity of arbuscular mycorrhizal fungi in acid soil contaminated by trace elements.

    PubMed

    Montiel-Rozas, María Del Mar; López-García, Álvaro; Kjøller, Rasmus; Madejón, Engracia; Rosendahl, Søren

    2016-08-01

    In 1998, a toxic mine spill polluted a 55-km(2) area in a basin southward to Doñana National Park (Spain). Subsequent attempts to restore those trace element-contaminated soils have involved physical, chemical, or biological methodologies. In this study, the restoration approach included application of different types and doses of organic amendments: biosolid compost (BC) and leonardite (LEO). Twelve years after the last addition, molecular analyses of arbuscular mycorrhizal (AM) fungal communities associated with target plants (Lamarckia aurea and Chrysanthemum coronarium) as well as analyses of trace element concentrations both in soil and in plants were performed. The results showed an improved soil quality reflected by an increase in soil pH and a decrease in trace element availability as a result of the amendments and dosages. Additionally, the phylogenetic diversity of the AM fungal community increased, reaching the maximum diversity at the highest dose of BC. Trace element concentration was considered the predominant soil factor determining the AM fungal community composition. Thereby, the studied AM fungal community reflects a community adapted to different levels of contamination as a result of the amendments. The study highlights the long-term effect of the amendments in stabilizing the soil system.

  10. Host Preferences of Arbuscular Mycorrhizal Fungi Colonizing Annual Herbaceous Plant Species in Semiarid Mediterranean Prairies

    PubMed Central

    Torrecillas, E.; Roldán, A.

    2012-01-01

    In this study, we have analyzed and compared the diversities of the arbuscular mycorrhizal fungi (AMF) colonizing the roots of five annual herbaceous species (Hieracium vulgare, Stipa capensis, Anagallis arvensis, Carduus tenuiflorus, and Avena barbata) and a perennial herbaceous species (Brachypodium retusum). Our goal was to determine the differences in the communities of the AMF among these six plant species belonging to different families, using B. retusum as a reference. The AMF small-subunit rRNA genes (SSU) were subjected to nested PCR, cloning, sequencing, and phylogenetic analysis. Thirty-six AMF phylotypes, belonging to Glomus group A, Glomus group B, Diversispora, Paraglomus, and Ambispora, were identified. Five sequence groups identified in this study clustered to known glomalean species or isolates: group Glomus G27 to Glomus intraradices, group Glomus G19 to Glomus iranicum, group Glomus G10 to Glomus mosseae, group Glomus G1 to Glomus lamellosum/etunicatum/luteum, and group Ambispora 1 to Ambispora fennica. The six plant species studied hosted different AMF communities. A certain trend of AMF specificity was observed when grouping plant species by taxonomic families, highlighting the importance of protecting and even promoting the native annual vegetation in order to maintain the biodiversity and productivity of these extreme ecosystems. PMID:22752164

  11. Arbuscular mycorrhizal fungi regulate soil respiration and its response to precipitation change in a semiarid steppe

    PubMed Central

    Zhang, Bingwei; Li, Shan; Chen, Shiping; Ren, Tingting; Yang, Zhiqiang; Zhao, Hanlin; Liang, Yu; Han, Xingguo

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) are critical links in plant–soil continuum and play a critical role in soil carbon cycles. Soil respiration, one of the largest carbon fluxes in global carbon cycle, is sensitive to precipitation change in semiarid ecosystems. In this study, a field experiment with fungicide application and water addition was conducted during 2010–2013 in a semiarid steppe in Inner Mongolia, China, and soil respiration was continuously measured to investigate the influences of AMF on soil respiration under different precipitation regimes. Results showed that soil respiration was promoted by water addition treatment especially during drought seasons, which induced a nonlinear response of soil respiration to precipitation change. Fungicide application suppressed AMF root colonization without impacts on soil microbes. AMF suppression treatment accelerated soil respiration with 2.7, 28.5 and 37.6 g C m−2 across three seasons, which were mainly caused by the enhanced heterotrophic component. A steeper response of soil respiration rate to precipitation was found under fungicide application treatments, suggesting a greater dampening effect of AMF on soil carbon release as water availability increased. Our study highlighted the importance of AMF on soil carbon stabilization and sequestration in semiarid steppe ecosystems especially during wet seasons. PMID:26818214

  12. Fungi in the future: Interannual variation and effects of atmospheric change on arbuscular mycorrhizal fungal communities

    SciTech Connect

    Cotton, T. E. Anne; Fitter, Alastair H.; Miller, R. Michael; Dumbrell, Alex J.; Helgason, Thorunn

    2015-01-05

    Understanding the natural dynamics of arbuscular mycorrhizal (AM) fungi and their response to global environmental change is essential for the prediction of future plant growth and ecosystem functions. We investigated the long-term temporal dynamics and effect of elevated atmospheric carbon dioxide (CO2) and ozone (O3) concentrations on AM fungal communities. Molecular methods were used to characterize the AM fungal communities of soybean (Glycine max) grown under elevated and ambient atmospheric concentrations of both CO2 and O3 within a free air concentration enrichment experiment in three growing seasons over 5 yr. Elevated CO2 altered the community composition of AM fungi, increasing the ratio of Glomeraceae to Gigasporaceae. By contrast, no effect of elevated O3 on AM fungal communities was detected. However, the greatest compositional differences detected were between years, suggesting that, at least in the short term, large-scale interannual temporal dynamics are stronger mediators than atmospheric CO2 concentrations of AM fungal communities. We conclude that, although atmospheric change may significantly alter AM fungal communities, this effect may be masked by the influences of natural changes and successional patterns through time. We suggest that changes in carbon availability are important determinants of the community dynamics of AM fungi.

  13. Fungi in the future: Interannual variation and effects of atmospheric change on arbuscular mycorrhizal fungal communities

    DOE PAGES

    Cotton, T. E. Anne; Fitter, Alastair H.; Miller, R. Michael; ...

    2015-01-05

    Understanding the natural dynamics of arbuscular mycorrhizal (AM) fungi and their response to global environmental change is essential for the prediction of future plant growth and ecosystem functions. We investigated the long-term temporal dynamics and effect of elevated atmospheric carbon dioxide (CO2) and ozone (O3) concentrations on AM fungal communities. Molecular methods were used to characterize the AM fungal communities of soybean (Glycine max) grown under elevated and ambient atmospheric concentrations of both CO2 and O3 within a free air concentration enrichment experiment in three growing seasons over 5 yr. Elevated CO2 altered the community composition of AM fungi, increasingmore » the ratio of Glomeraceae to Gigasporaceae. By contrast, no effect of elevated O3 on AM fungal communities was detected. However, the greatest compositional differences detected were between years, suggesting that, at least in the short term, large-scale interannual temporal dynamics are stronger mediators than atmospheric CO2 concentrations of AM fungal communities. We conclude that, although atmospheric change may significantly alter AM fungal communities, this effect may be masked by the influences of natural changes and successional patterns through time. We suggest that changes in carbon availability are important determinants of the community dynamics of AM fungi.« less

  14. The Glyoxylate Cycle in an Arbuscular Mycorrhizal Fungus. Carbon Flux and Gene Expression

    PubMed Central

    Lammers, Peter J.; Jun, Jeongwon; Abubaker, Jehad; Arreola, Raul; Gopalan, Anjali; Bago, Berta; Hernandez-Sebastia, Cinta; Allen, James W.; Douds, David D.; Pfeffer, Philip E.; Shachar-Hill, Yair

    2001-01-01

    The arbuscular mycorrhizal (AM) symbiosis is responsible for huge fluxes of photosynthetically fixed carbon from plants to the soil. Lipid, which is the dominant form of stored carbon in the fungal partner and which fuels spore germination, is made by the fungus within the root and is exported to the extraradical mycelium. We tested the hypothesis that the glyoxylate cycle is central to the flow of carbon in the AM symbiosis. The results of 13C labeling of germinating spores and extraradical mycelium with 13C2-acetate and 13C2-glycerol and analysis by nuclear magnetic resonance spectroscopy indicate that there are very substantial fluxes through the glyoxylate cycle in the fungal partner. Full-length sequences obtained by polymerase chain reaction from a cDNA library from germinating spores of the AM fungus Glomus intraradices showed strong homology to gene sequences for isocitrate lyase and malate synthase from plants and other fungal species. Quantitative real-time polymerase chain reaction measurements show that these genes are expressed at significant levels during the symbiosis. Glyoxysome-like bodies were observed by electron microscopy in fungal structures where the glyoxylate cycle is expected to be active, which is consistent with the presence in both enzyme sequences of motifs associated with glyoxysomal targeting. We also identified among several hundred expressed sequence tags several enzymes of primary metabolism whose expression during spore germination is consistent with previous labeling studies and with fluxes into and out of the glyoxylate cycle. PMID:11706207

  15. Anthropogenic land use shapes the composition and phylogenetic structure of soil arbuscular mycorrhizal fungal communities.

    PubMed

    Moora, Mari; Davison, John; Öpik, Maarja; Metsis, Madis; Saks, Ülle; Jairus, Teele; Vasar, Martti; Zobel, Martin

    2014-12-01

    Arbuscular mycorrhizal (AM) fungi play an important role in ecosystems, but little is known about how soil AM fungal community composition varies in relation to habitat type and land-use intensity. We molecularly characterized AM fungal communities in soil samples (n = 88) from structurally open (permanent grassland, intensive and sustainable agriculture) and forested habitats (primeval forest and spruce plantation). The habitats harboured significantly different AM fungal communities, and there was a broad difference in fungal community composition between forested and open habitats, the latter being characterized by higher average AM fungal richness. Within both open and forest habitats, intensive land use significantly influenced community composition. There was a broad difference in the phylogenetic structure of AM fungal communities between mechanically disturbed and nondisturbed habitats. Taxa from Glomeraceae served as indicator species for the nondisturbed habitats, while taxa from Archaeosporaceae, Claroideoglomeraceae and Diversisporaceae were indicators for the disturbed habitats. The distribution of these indicator taxa among habitat types in the MaarjAM global database of AM fungal diversity was in accordance with their local indicator status.

  16. Arbuscular mycorrhizal fungal community differs between a coexisting native shrub and introduced annual grass.

    PubMed

    Busby, Ryan R; Stromberger, Mary E; Rodriguez, Giselle; Gebhart, Dick L; Paschke, Mark W

    2013-02-01

    Arbuscular mycorrhizal fungi (AMF) have been implicated in non-native plant invasion success and persistence. However, few studies have identified the AMF species associating directly with plant invaders, or how these associations differ from those of native plant species. Identifying changes to the AMF community due to plant invasion could yield key plant-AMF interactions necessary for the restoration of native plant communities. This research compared AMF associating with coexisting Bromus tectorum, an invasive annual grass, and Artemisia tridentata, the dominant native shrub in western North America. At three sites, soil and root samples from Bromus and Artemisia were collected. Sporulation was induced using trap cultures, and spores were identified using morphological characteristics. DNA was extracted from root and soil subsamples and amplified. Sequences obtained were aligned and analyzed to compare diversity, composition, and phylogenetic distance between hosts and sites. Richness of AMF species associated with Artemisia in cultures was higher than AMF species associated with Bromus. Gamma diversity was similar and beta diversity was higher in AMF associated with Bromus compared to Artemisia. AMF community composition differed between hosts in both cultures and roots. Two AMF species (Archaeospora trappei and Viscospora viscosum) associated more frequently with Artemisia than Bromus across multiple sites. AMF communities in Bromus roots were more phylogenetically dispersed than in Artemisia roots, indicating a greater competition for resources within the invasive grass. Bromus associated with an AMF community that differed from Artemisia in a number of ways, and these changes could restrict native plant establishment.

  17. Spatio-Temporal Variation of Core and Satellite Arbuscular Mycorrhizal Fungus Communities in Miscanthus giganteus.

    PubMed

    Barnes, Christopher J; Burns, Caitlin A; van der Gast, Christopher J; McNamara, Niall P; Bending, Gary D

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) are a group of obligate plant symbionts which can promote plant nutrition. AMF communities are diverse, but the factors which control their assembly in space and time remain unclear. In this study, the contributions of geographical distance, environmental heterogeneity and time in shaping AMF communities associated with Miscanthus giganteus (a perennial grass originating from south-east Asia) were determined over a 13 months period. In particular, the community was partitioned into core (abundant and persistent taxa) and satellite (taxa with low abundance and persistence) constituents and the drivers of community assembly for each determined. β-diversity was exceptionally low across the 140 m line transects, and there was limited evidence of geographical scaling effects on the composition of the core, satellite or combined communities. However, AMF richness and community composition changed over time associated with fluctuation within both the core and satellite communities. The degree to which AMF community variation was explained by soil properties was consistently higher in the core community than the combined and satellite communities, suggesting that the satellite community had considerable stochasticity associated with it. We suggest that the partitioning of communities into their core and satellite constituents could be employed to enhance the variation explained within microbial community analyses.

  18. Influence of Arbuscular Mycorrhizal Fungus (AMF) on degradation of iron-cyanide complexes

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Soil contamination in the vicinities of former Manufactured Gas Plant (MGP) sites is a worldwide known environmental issue. The pollutants, in form of iron-cyanide complexes, originating from the gas purification process, create a risk for human health due to potential release of toxic free cyanide, CN(aq) and HCN(g), (aq).The management and remediation of cyanide contaminated soil can be very challenging due to the complex chemistry and toxicity of CN compounds. The employment of phytoremediation to remove or stabilize contaminants at a former MGP site is an inexpensive process, but can be limited through shallow rotting, decreased biomass, poor growing and the risk of secondary accumulation. However, this adaptation may be enhanced via arbuscular mycorrhizal fungi (AMF) activity, which may cooperate on the degradation, transformation or uptake of the contaminants. We would like to present our preliminary results from the ongoing project concerning toxic substrate-AMF-plant relation, based on studying the site of a former MGP site. In situ experiments contributed to identifying those fungi that are likely to persist in extremely acidic and toxic conditions. Subsequently, commercially available Rhizophagus irregularis was grown in sterilized, un-spiked soil with the roots of the host plant Calamagrostis epigejos. Extracted roots and AMF hyphae were used in the batch experiment, were the potential of this association on degradation of iron-cyanide complexes, in form of potassium ferrocyanide solution, was assessed.

  19. Arbuscular mycorrhizal fungal networks vary throughout the growing season and between successional stages.

    PubMed

    Bennett, Alison Elizabeth; Daniell, Tim John; Öpik, Maarja; Davison, John; Moora, Mari; Zobel, Martin; Selosse, Marc-André; Evans, Darren

    2013-01-01

    To date, few analyses of mutualistic networks have investigated successional or seasonal dynamics. Combining interaction data from multiple time points likely creates an inaccurate picture of the structure of networks (because these networks are aggregated across time), which may negatively influence their application in ecosystem assessments and conservation. Using a replicated bipartite mutualistic network of arbuscular mycorrhizal (AM) fungal-plant associations, detected using large sample numbers of plants and AM fungi identified through molecular techniques, we test whether the properties of the network are temporally dynamic either between different successional stages or within the growing season. These questions have never been directly tested in the AM fungal-plant mutualism or the vast majority of other mutualisms. We demonstrate the following results: First, our examination of two different successional stages (young and old forest) demonstrated that succession increases the proportion of specialists within the community and decreases the number of interactions. Second, AM fungal-plant mutualism structure changed throughout the growing season as the number of links between partners increased. Third, we observed shifts in associations between AM fungal and plant species throughout the growing season, potentially reflecting changes in biotic and abiotic conditions. Thus, this analysis opens up two entirely new areas of research: 1) identifying what influences changes in plant-AM fungal associations in these networks, and 2) what aspects of temporal variation and succession are of general importance in structuring bipartite networks and plant-AM fungal communities.

  20. Diurnal patterns of productivity of arbuscular mycorrhizal fungi revealed with the Soil Ecosystem Observatory.

    PubMed

    Hernandez, Rebecca R; Allen, Michael F

    2013-10-01

    Arbuscular mycorrhizal (AM) fungi are the most abundant plant symbiont and a major pathway of carbon sequestration in soils. However, their basic biology, including their activity throughout a 24-h day : night cycle, remains unknown. We employed the in situ Soil Ecosystem Observatory to quantify the rates of diurnal growth, dieback and net productivity of extra-radical AM fungi. AM fungal hyphae showed significantly different rates of growth and dieback over a period of 24 h and paralleled the circadian-driven photosynthetic oscillations observed in plants. The greatest rates (and incidences) of growth and dieback occurred between noon and 18:00 h. Growth and dieback events often occurred simultaneously and were tightly coupled with soil temperature and moisture, suggesting a rapid acclimation of the external phase of AM fungi to the immediate environment. Changes in the environmental conditions and variability of the mycorrhizosphere may alter the diurnal patterns of productivity of AM fungi, thereby modifying soil carbon sequestration, nutrient cycling and host plant success.

  1. Invasion of Spores of the Arbuscular Mycorrhizal Fungus Gigaspora decipiens by Burkholderia spp.

    PubMed Central

    Levy, Avram; Chang, Barbara J.; Abbott, Lynette K.; Kuo, John; Harnett, Gerry; Inglis, Timothy J. J.

    2003-01-01

    Burkholderia species are bacterial soil inhabitants that are capable of interacting with a variety of eukaryotes, in some cases occupying intracellular habitats. Pathogenic and nonpathogenic Burkholderia spp., including B. vietnamiensis, B. cepacia, and B. pseudomallei, were grown on germinating spores of the arbuscular mycorrhizal fungus Gigaspora decipiens. Spore lysis assays revealed that all Burkholderia spp. tested were able to colonize the interior of G. decipiens spores. Amplification of specific DNA sequences and transmission electron microscopy confirmed the intracellular presence of B. vietnamiensis. Twelve percent of all spores were invaded by B. vietnamiensis, with an average of 1.5 × 106 CFU recovered from individual infected spores. Of those spores inoculated with B. pseudomallei, 7% were invaded, with an average of 5.5 × 105 CFU recovered from individual infected spores. Scanning electron and fluorescence microscopy provided insights into the morphology of surfaces of spores and hyphae of G. decipiens and the attachment of bacteria. Burkholderia spp. colonized both hyphae and spores, attaching to surfaces in either an end-on or side-on fashion. Adherence of Burkholderia spp. to eukaryotic surfaces also involved the formation of numerous fibrillar structures. PMID:14532087

  2. Temperature constraints on the growth and functioning of root organ cultures with arbuscular mycorrhizal fungi.

    PubMed

    Gavito, Mayra E; Olsson, Pål A; Rouhier, Hervé; Medina-Peñafiel, Almudena; Jakobsen, Iver; Bago, Albert; Azcón-Aguilar, Concepción

    2005-10-01

    In this study we investigated the effects of temperature on fungal growth and tested whether the differences in fungal growth were related to the effects of temperature on carbon movement to, or within, the fungus. Growth curves and C uptake-transfer-translocation measurements were obtained for three arbuscular mycorrhizal fungi (AMF) isolates cultured within a 6-30 degrees C temperature range. A series of experiments with a model fungal isolate, Glomus intraradices, was used to examine the effects of temperature on lipid body and 33P movement, and to investigate the role of acclimation and incubation time. Temperature effects on AMF growth were both direct and indirect because, despite clear independent root and AMF growth responses in some cases, the uptake and translocation of 13C was also affected within the temperature range tested. Root C uptake and, to a lesser extent, C translocation in the fungus, were reduced by low temperatures (< 18 degrees C). Uptake and translocation of 33P by fungal hyphae were, by contrast, similar between 10 and 25 degrees C. We conclude that temperature, between 6 and 18 degrees C, reduces AMF growth, and that C movement to the fungus is involved in this response.

  3. Genetic Diversity and Association Characters of Bacteria Isolated from Arbuscular Mycorrhizal Fungal Spore Walls.

    PubMed

    Selvakumar, Gopal; Krishnamoorthy, Ramasamy; Kim, Kiyoon; Sa, Tong-Min

    2016-01-01

    Association between arbuscular mycorrhizal fungi (AMF) and bacteria has long been studied. However, the factors influencing their association in the natural environment is still unknown. This study aimed to isolate bacteria associated with spore walls of AMF and identify their potential characters for association. Spores collected from coastal reclamation land were differentiated based on their morphology and identified by 18S rDNA sequencing as Funneliformis caledonium, Racocetra alborosea and Funneliformis mosseae. Bacteria associated with AMF spore walls were isolated after treating them with disinfection solution at different time intervals. After 0, 10 and 20 min of spore disinfection, 86, 24 and 10 spore associated bacteria (SAB) were isolated, respectively. BOX-PCR fingerprinting analysis showed that diverse bacterial communities were associated to AMF spores. Bacteria belonging to the same genera could associate with different AMF spores. Gram positive bacteria were more closely associated with AMF spores. Isolated SAB were characterized and tested for spore association characters such as chitinase, protease, cellulase enzymes and exopolysaccharide production (EPS). Among the 120 SAB, 113 SAB were able to show one or more characters for association and seven SAB did not show any association characters. The 16S rDNA sequence of SAB revealed that bacteria belonging to the phyla Firmicutes, Proteobacteria, Actinobacteria and Bactereiodes were associated with AMF spore walls.

  4. Genetic Diversity and Association Characters of Bacteria Isolated from Arbuscular Mycorrhizal Fungal Spore Walls

    PubMed Central

    Selvakumar, Gopal; Krishnamoorthy, Ramasamy; Kim, Kiyoon; Sa, Tong-Min

    2016-01-01

    Association between arbuscular mycorrhizal fungi (AMF) and bacteria has long been studied. However, the factors influencing their association in the natural environment is still unknown. This study aimed to isolate bacteria associated with spore walls of AMF and identify their potential characters for association. Spores collected from coastal reclamation land were differentiated based on their morphology and identified by 18S rDNA sequencing as Funneliformis caledonium, Racocetra alborosea and Funneliformis mosseae. Bacteria associated with AMF spore walls were isolated after treating them with disinfection solution at different time intervals. After 0, 10 and 20 min of spore disinfection, 86, 24 and 10 spore associated bacteria (SAB) were isolated, respectively. BOX-PCR fingerprinting analysis showed that diverse bacterial communities were associated to AMF spores. Bacteria belonging to the same genera could associate with different AMF spores. Gram positive bacteria were more closely associated with AMF spores. Isolated SAB were characterized and tested for spore association characters such as chitinase, protease, cellulase enzymes and exopolysaccharide production (EPS). Among the 120 SAB, 113 SAB were able to show one or more characters for association and seven SAB did not show any association characters. The 16S rDNA sequence of SAB revealed that bacteria belonging to the phyla Firmicutes, Proteobacteria, Actinobacteria and Bactereiodes were associated with AMF spore walls. PMID:27479250

  5. Variation of arbuscular mycorrhizal fungal communities along an altitudinal gradient in rupestrian grasslands in Brazil.

    PubMed

    Coutinho, Etiene Silva; Fernandes, G Wilson; Berbara, Ricardo Luís Louro; Valério, Henrique Maia; Goto, Bruno Tomio

    2015-11-01

    Variation in arbuscular mycorrhizal fungi (AMF) communities is described for the first time in rupestrian grasslands in Brazil along an altitudinal gradient of 700 m (800 to 1400 m a.s.l.). Hypotheses tested were that soil properties influence the variation in AMF communities and that the frequency of the most common species of AMF is inversely influenced by the richness of other AMF. Field and laboratory data were collected on AMF community composition, richness, density, and frequency in the altitudinal gradient, and the relationships with several physical-chemical soil properties and altitude were evaluated. Fifty-one species of AMF were recorded, with 14 species being reported as possibly new to science and nine species representing new records for Brazil. This single elevation gradient alone contains 22% of the known world diversity of AMF. Soil properties and AMF community density and richness varied significantly along the elevation (p < 0.05). AMF density and richness were higher at the intermediate altitude, while AMF species composition differed statistically among the altitudes.

  6. [Seasonal variation and related affecting factors of arbuscular mycorrhizal fungi in Caragana korshinskii roots].

    PubMed

    Liu, Yong-Jun; Zheng, Hong; He, Lei; An, Li-Zhe; Feng, Hu-Yuan

    2009-05-01

    With the combination of root staining and PCR-DGGE, the seasonal variation of arbuscular mycorrhizal fungi (AMF) in Caragana korshinskii roots was investigated; and by the methods of principal component analysis and canonical correspondence analysis, the relationships between this variation and soil factors were analyzed. It was found that the total infection rate of AMF and the infection rates of arbuscules and vesicles in C. korshinskii roots as well as the spore density of AMF in soil varied significantly among seasons. From spring to autumn, the total infection rate of AMF had a decreasing trend, whereas the other three indicators were in adverse. A total of nine AMF phylotypes were detected in spring, summer, and autumn, but the community composition and diversity indices of AMF had definite differences among the seasons. The infection rate of vesicles decreased with increasing soil total N, P, and organic C, while the spore density of AMF increased with decreasing soil moisture and available P. The seasonal variation of AMF community composition in C. korshinskii roots was mainly affected by soil total P, available P, and organic C.

  7. Arbuscular Mycorrhizal Fungal Networks Vary throughout the Growing Season and between Successional Stages

    PubMed Central

    Bennett, Alison Elizabeth; Daniell, Tim John; Öpik, Maarja; Davison, John; Moora, Mari; Zobel, Martin; Selosse, Marc-André; Evans, Darren

    2013-01-01

    To date, few analyses of mutualistic networks have investigated successional or seasonal dynamics. Combining interaction data from multiple time points likely creates an inaccurate picture of the structure of networks (because these networks are aggregated across time), which may negatively influence their application in ecosystem assessments and conservation. Using a replicated bipartite mutualistic network of arbuscular mycorrhizal (AM) fungal-plant associations, detected using large sample numbers of plants and AM fungi identified through molecular techniques, we test whether the properties of the network are temporally dynamic either between different successional stages or within the growing season. These questions have never been directly tested in the AM fungal-plant mutualism or the vast majority of other mutualisms. We demonstrate the following results: First, our examination of two different successional stages (young and old forest) demonstrated that succession increases the proportion of specialists within the community and decreases the number of interactions. Second, AM fungal-plant mutualism structure changed throughout the growing season as the number of links between partners increased. Third, we observed shifts in associations between AM fungal and plant species throughout the growing season, potentially reflecting changes in biotic and abiotic conditions. Thus, this analysis opens up two entirely new areas of research: 1) identifying what influences changes in plant-AM fungal associations in these networks, and 2) what aspects of temporal variation and succession are of general importance in structuring bipartite networks and plant-AM fungal communities. PMID:24358265

  8. Arbuscular mycorrhizal fungi regulate soil respiration and its response to precipitation change in a semiarid steppe.

    PubMed

    Zhang, Bingwei; Li, Shan; Chen, Shiping; Ren, Tingting; Yang, Zhiqiang; Zhao, Hanlin; Liang, Yu; Han, Xingguo

    2016-01-28

    Arbuscular mycorrhizal fungi (AMF) are critical links in plant-soil continuum and play a critical role in soil carbon cycles. Soil respiration, one of the largest carbon fluxes in global carbon cycle, is sensitive to precipitation change in semiarid ecosystems. In this study, a field experiment with fungicide application and water addition was conducted during 2010-2013 in a semiarid steppe in Inner Mongolia, China, and soil respiration was continuously measured to investigate the influences of AMF on soil respiration under different precipitation regimes. Results showed that soil respiration was promoted by water addition treatment especially during drought seasons, which induced a nonlinear response of soil respiration to precipitation change. Fungicide application suppressed AMF root colonization without impacts on soil microbes. AMF suppression treatment accelerated soil respiration with 2.7, 28.5 and 37.6 g C m(-2) across three seasons, which were mainly caused by the enhanced heterotrophic component. A steeper response of soil respiration rate to precipitation was found under fungicide application treatments, suggesting a greater dampening effect of AMF on soil carbon release as water availability increased. Our study highlighted the importance of AMF on soil carbon stabilization and sequestration in semiarid steppe ecosystems especially during wet seasons.

  9. Arbuscular mycorrhizal fungi protect a native plant from allelopathic effects of an invader.

    PubMed

    Barto, Kathryn; Friese, Carl; Cipollini, Don

    2010-04-01

    The allelopathic potential of the Eurasian invasive plant Alliaria petiolata has been well documented, with the bulk of the effects believed to be mediated by arbuscular mycorrhizal fungi (AMF). We exposed the herbaceous annual Impatiens pallida, which is native to North America, to fractionated A. petiolata extracts at four developmental stages (germination, presymbiosis growth, symbiosis formation, and symbiosis growth) by using exposure levels expected to be similar to field levels. Surprisingly, we found strong direct effects on I. pallida germination and growth, but no indirect effects on I. pallida growth mediated by AMF. We also observed strong synergistic effects with a complete A. petiolata extract that inhibited I. pallida germination and presymbiosis root growth more than either a glucosinolate or flavonoid enriched fraction alone. In fact, the flavonoid enriched fraction tended to stimulate germination and presymbiosis root growth. In contrast to these strong direct effects, I. pallida plant growth during both the symbiosis formation and symbiosis growth phases was unaffected by A. petiolata extracts. We also found no inhibition of AMF colonization of roots or soils by A. petiolata extracts. We show that AMF can actually ameliorate allelopathic effects of an invasive plant, and suggest that previously observed allelopathic effects of A. petiolata may be due to direct inhibition of plant and fungal growth before symbiosis formation.

  10. Interactions between Trichoderma pseudokoningii strains and the arbuscular mycorrhizal fungi Glomus mosseae and Gigaspora rosea.

    PubMed

    Martinez, Alicia; Obertello, Mariana; Pardo, Alejandro; Ocampo, Juan A; Godeas, Alicia

    2004-04-01

    The interaction between Trichoderma pseudokoningii (Rifai) 511, 2212, 741A, 741B and 453 and the arbuscular mycorrhizal fungi Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe BEG12 and Gigaspora rosea Nicolson & Schenck BEG9 were studied in vitro and in greenhouse experiments. All T. pseudokoningii strains inhibited the germination of G. mosseae and Gi. rosea except the strain 453, which did not affect the germination of Gi. rosea. Soluble exudates and volatile substances produced by all T. pseudokoningii strains inhibited the spore germination of G. mosseae. The germination of Gi. rosea spores was inhibited by the soluble exudates produced by T. pseudokoningii 2212 and 511, whereas T. pseudokoningii 714A and 714B inhibited the germination of Gi. rosea spores by the production of volatile substances. The strains of T. pseudokoningii did not affect dry matter and percentage of root length colonization of soybean inoculated with G. mosseae, except T. pseudokoningii 2212, which inhibited both parameters. However, all T. pseudokoningii strains decreased the shoot dry matter and the percentage of AM root length colonization of soybean inoculated with Gi. rosea. The saprotrophic fungi tested seem to affect AM colonization of root by effects on the presymbiotic phase of the AM fungi. No influence of AM fungi on the number of CFUs of T. pseudokoningii was found. The effect of saprotrophic fungi on AM fungal development and function varied with the strain of the saprotrophic species tested.

  11. Tolerance and induction of tolerance to Ni of arbuscular mycorrhizal fungi from New Caledonian ultramafic soils.

    PubMed

    Amir, Hamid; Jasper, David A; Abbott, Lynette K

    2008-12-01

    The influence of Ni on arbuscular mycorrhizal fungi (AMF) has not been studied yet. We tested the tolerance to Ni of five AMF isolates from New Caledonian ultramafic soils. Spore germination indicated that these isolates were clearly more tolerant to Ni than three other isolates from non-ultramafic soils. They were able to germinate at 30 microg g(-1) Ni, whereas spores of the non-ultramafic isolates were totally inhibited at 15 microg g(-1) Ni. Among the ultramafic isolates, two were obtained from roots of Ni-hyperaccumulating plants. Their tolerance to Ni was clearly higher than all the other isolates. The proportion of germinated spores of the different isolates in contact with ultramafic soils showed the same tendencies as those observed with Ni solutions. Tolerance to Ni increased when spores were produced from mycorrhiza on plants grown on sand containing 20 microg g(-1) Ni, in comparison with those produced on sand without Ni. These results indicate that the tolerance to Ni of AMF spores can be induced by the presence of this metal in the substrate.

  12. Arbuscular mycorrhizal fungi enhance soil carbon sequestration in the coalfields, northwest China

    PubMed Central

    Wang, Zhi-Gang; Bi, Yin-Li; Jiang, Bin; Zhakypbek, Yryszhan; Peng, Su-Ping; Liu, Wen-Wen; Liu, Hao

    2016-01-01

    Carbon storage is affected by photosynthesis (Pn) and soil respiration (Rs), which have been studied extensively in natural and agricultural systems. However, the effects of Pn and Rs on carbon storages in the presence of arbuscular mycorrhizal fungi (AMF) in coalfields remain unclear. A field experiment was established in 2014 in Shendong coal mining subsidence area. The treatments comprised two inoculation levels (inoculated with or without 100 g AMF inoculums per seedlings) and four plant species [wild cherry (Prunus discadenia Koebne L.), cerasus humilis (Prunus dictyneura Diels L.), shiny leaf Yellow horn (Xanthoceras sorbifolium Bunge L.) and apricot (Armeniaca sibirica L.)]. AMF increased Pn of four species ranging from 15.3% to 33.1% and carbon storage, averaged by 17.2% compared to controls. Soil organic carbon (OC), easily extractable glomalin-relation soil protein (EE-GRSP), and total glomalin-relation soil protein (T-GRSP) were significantly increased by AMF treatment. The effect of AMF on the sensitivity of Rs depended on soil temperature. The results highlighted the exponential models to explain the responses of Rs to soil temperature, and for the first time quantified AMF caused carbon sequestration and Rs. Thus, to our knowledge, AMF is beneficial to ecosystems through facilitating carbon conservation in coalfield soils. PMID:27748365

  13. A Medicago truncatula phosphate transporter indispensable for the arbuscular mycorrhizal symbiosis.

    PubMed

    Javot, Hélène; Penmetsa, R Varma; Terzaghi, Nadia; Cook, Douglas R; Harrison, Maria J

    2007-01-30

    The arbuscular mycorrhizal (AM) symbiosis is a mutualistic endosymbiosis formed by plant roots and AM fungi. Most vascular flowering plants have the ability to form these associations, which have a significant impact on plant health and consequently on ecosystem function. Nutrient exchange is a central feature of the AM symbiosis, and AM fungi obtain carbon from their plant host while assisting the plant with the acquisition of phosphorus (as phosphate) from the soil. In the AM symbiosis, the fungus delivers P(i) to the root through specialized hyphae called arbuscules. The molecular mechanisms of P(i) and carbon transfer in the symbiosis are largely unknown, as are the mechanisms by which the plant regulates the symbiosis in response to its nutrient status. Plants possess many classes of P(i) transport proteins, including a unique clade (Pht1, subfamily I), members of which are expressed only in the AM symbiosis. Here, we show that MtPT4, a Medicago truncatula member of subfamily I, is essential for the acquisition of P(i) delivered by the AM fungus. However, more significantly, MtPT4 function is critical for AM symbiosis. Loss of MtPT4 function leads to premature death of the arbuscules; the fungus is unable to proliferate within the root, and symbiosis is terminated. Thus, P(i) transport is not only a benefit for the plant but is also a requirement for the AM symbiosis.

  14. Experimental warming decreases arbuscular mycorrhizal fungal colonization in prairie plants along a Mediterranean climate gradient

    PubMed Central

    Johnson, Bart R.; Bohannan, Brendan; Pfeifer-Meister, Laurel; Mueller, Rebecca; Bridgham, Scott D.

    2016-01-01

    Background: Arbuscular mycorrhizal fungi (AMF) provide numerous services to their plant symbionts. Understanding climate change effects on AMF, and the resulting plant responses, is crucial for predicting ecosystem responses at regional and global scales. We investigated how the effects of climate change on AMF-plant symbioses are mediated by soil water availability, soil nutrient availability, and vegetation dynamics. Methods: We used a combination of a greenhouse experiment and a manipulative climate change experiment embedded within a Mediterranean climate gradient in the Pacific Northwest, USA to examine this question. Structural equation modeling (SEM) was used to determine the direct and indirect effects of experimental warming on AMF colonization. Results: Warming directly decreased AMF colonization across plant species and across the climate gradient of the study region. Other positive and negative indirect effects of warming, mediated by soil water availability, soil nutrient availability, and vegetation dynamics, canceled each other out. Discussion: A warming-induced decrease in AMF colonization would likely have substantial consequences for plant communities and ecosystem function. Moreover, predicted increases in more intense droughts and heavier rains for this region could shift the balance among indirect causal pathways, and either exacerbate or mitigate the negative, direct effect of increased temperature on AMF colonization. PMID:27280074

  15. Effect of organic farming on spore diversity of arbuscular mycorrhizal fungi and glomalin in soil.

    PubMed

    Lee, Ji-Eun; Eom, Ahn-Heum

    2009-12-01

    In this study, eight soil samples were collected from organic and conventional farms in a central area of South Korea. Spore communities of arbuscular mycorrhizal fungi (AMF) and glomalin, a glycoprotein produced by AMF, were analyzed. Spores of Glomus clarum, G. etunicatum, G. mosseae, G. sp., Acaulospora longula, A. spinosa, Gigaspora margarita, and Paraglomus occultum were identified at the study sites, based on morphological and molecular characteristics. While Acaulospora longula was the most dominant species in soils at organic farms, Paraglomus occultum was the most dominant species in soils at conventional farms. Species diversity and species number in AMF communities found in soils from organic farms were significantly higher than in soils from conventional farms. Glomalin was also extracted from soil samples collected at organic and conventional farms and was analyzed using both Bradford and enzyme-linked immunosorbent assays. The glomalin content in soils from organic farms was significantly higher than in soils from conventional farms. These results indicate that agricultural practices significantly affect AMF abundance and community structure.

  16. Transition Metal Transport in Plants and Associated Endosymbionts: Arbuscular Mycorrhizal Fungi and Rhizobia

    PubMed Central

    González-Guerrero, Manuel; Escudero, Viviana; Saéz, Ángela; Tejada-Jiménez, Manuel

    2016-01-01

    Transition metals such as iron, copper, zinc, or molybdenum are essential nutrients for plants. These elements are involved in almost every biological process, including photosynthesis, tolerance to biotic and abiotic stress, or symbiotic nitrogen fixation. However, plants often grow in soils with limiting metallic oligonutrient bioavailability. Consequently, to ensure the proper metal levels, plants have developed a complex metal uptake and distribution system, that not only involves the plant itself, but also its associated microorganisms. These microorganisms can simply increase metal solubility in soils and making them more accessible to the host plant, as well as induce the plant metal deficiency response, or directly deliver transition elements to cortical cells. Other, instead of providing metals, can act as metal sinks, such as endosymbiotic rhizobia in legume nodules that requires relatively large amounts to carry out nitrogen fixation. In this review, we propose to do an overview of metal transport mechanisms in the plant–microbe system, emphasizing the role of arbuscular mycorrhizal fungi and endosymbiotic rhizobia. PMID:27524990

  17. Phylogenetically structured traits in root systems influence arbuscular mycorrhizal colonization in woody angiosperms

    SciTech Connect

    Valverde-Barrantes, Oscar J.; Horning, Amber L.; Smemo, Kurt A.; Blackwood, Christopher B.

    2016-02-10

    In this study, there is little quantitative information about the relationship between root traits and the extent of arbuscular mycorrhizal fungi (AMF) colonization. We expected that ancestral species with thick roots will maximize AMF habitat by maintaining similar root traits across root orders (i.e., high root trait integration), whereas more derived species are expected to display a sharp transition from acquisition to structural roots. Moreover, we hypothesized that interspecific morphological differences rather than soil conditions will be the main driver of AMF colonization We analyzed 14 root morphological and chemical traits and AMF colonization rates for the first three root orders of 34 temperate tree species grown in two common gardens. We also collected associated soil to measure the effect of soil conditions on AMF colonization Results Thick-root magnoliids showed less variation in root traits along root orders than more-derived angiosperm groups. Variation in stele:root diameter ratio was the best indicator of AMF colonization within and across root orders. Root functional traits rather than soil conditions largely explained the variation in AMF colonization among species. In conclusion, not only the traits of first order but the entire structuring of the root system varied among plant lineages, suggesting alternative evolutionary strategies of resource acquisition. Understanding evolutionary pathways in below ground organs could open new avenues to understand tree species influence on soil carbon and nutrient cycling.

  18. Precipitation shapes communities of arbuscular mycorrhizal fungi in Tibetan alpine steppe

    PubMed Central

    Zhang, Jing; Wang, Fang; Che, Rongxiao; Wang, Ping; Liu, Hanke; Ji, Baoming; Cui, Xiaoyong

    2016-01-01

    Tibetan Plateau is one of the largest and most unique habitats for organisms including arbuscular mycorrhizal fungi (AMF). However, it remains unclear how AMF communities respond to key environmental changes in this harsh environment. To test if precipitation could be a driving force in shaping AMF community structures at regional scale, we examined AMF communities associated with dominant plant species along a precipitation gradient in Tibetan alpine steppe. Rhizosphere soils were collected from five sites with annual precipitation decreasing from 400 to 50 mm. A total of 31 AMF operational taxonomic units (OTUs) were identified. AMF community composition varied significantly among sites, whereas AMF community composition did not vary among plant species. Path analysis revealed that precipitation directly affected AMF hyphal length density, and indirectly influenced AMF species richness likely through the mediation of plant coverage. Our results suggested that water availability could drive the changes of AMF communities at regional scale. Given the important roles AMF could play in the dynamics of plant communities, exploring the changes of AMF communities along key environmental gradients would help us better predict the ecosystem level responses of the Tibetan vegetation to future climate change. PMID:27002188

  19. Effects of arbuscular mycorrhizal colonization and phosphorus application on nuclear ploidy in Allium porrum plants.

    PubMed

    Fusconi, Anna; Lingua, Guido; Trotta, Antonio; Berta, Graziella

    2005-07-01

    Arbuscular mycorrhizal (AM) colonization can strongly affect the plant cell nucleus, causing displacement from the periphery to the center of the cell, hypertrophy and polyploidization. The hypertrophy response has been shown in a variety of AM plants whilst polyploidization has been reported only in Lycopersicon esculentum, a multiploid species with a small genome. In order to determine whether polyploidization is a general plant response to AM colonization, analyses were performed on Allium porrum, a plant with a large genome, which is much less subject to polyploidization than L. esculentum. The ploidy status of leaves, complete root systems and four zones of the adventitious roots was investigated in relation to phosphorus content, AM colonization and root differentiation in A. porrum plants grown under two different regimes of phosphate nutrition in order to distinguish direct effects of the fungus from those of improved nutrition. Results showed the presence of two nuclear populations (2C and 4C) in all treatments and samples. Linear regression analyses suggested a general negative correlation between phosphorus content and the proportion of 2C nuclei. The percentage of 2C nuclei (and consequently that of 4C nuclei), was also influenced by AM colonization, differentiation and ageing of the root cells, which resulted in earlier occurrence, in time and space, of polyploid nuclei.

  20. Arbuscular mycorrhizal fungi reduced the ratios of inorganic/organic arsenic in rice grains.

    PubMed

    Li, H; Chen, X W; Wong, M H

    2016-02-01

    Arbuscular mycorrhizal fungi (AMF) - Rhizophagus intraradices was inoculated to rice to investigate its effects on arsenic (As) uptake, grain As speciation, and rhizospheric As concentration of six rice cultivars grown in As-amended soil (60 mg As kg(-1) soil). The AMF inoculation induced either positive, neutral or negative responses in rice grown in As contaminated soil, suggesting that functional diversity may exist in AMF symbiosis when As is taken up and transferred. The ratios of inorganic/organic As concentrations in rice grains of all cultivars were significantly reduced by AMF, that involved the transformation of inorganic As into less toxic organic form dimethylarsinic acid (DMA) in rice. AMF decreased significantly total As and inorganic As concentrations in rice grains of Handao 3. Positive correlations (R(2) = 0.30-0.56, P < 0.05) between As in the rhizospheric soil solution and As in rice grain at different periods were observed. This inferred that the As survey of soil solution can be an effective measure for evaluating As in grains.

  1. A history of the taxonomy and systematics of arbuscular mycorrhizal fungi belonging to the phylum Glomeromycota.

    PubMed

    Stürmer, Sidney Luiz

    2012-05-01

    Arbuscular mycorrhizal fungi (AMF) are grouped in a monophyletic group, the phylum Glomeromycota. In this review, the history and complexity of the taxonomy and systematics of these obligate biotrophs is addressed by recognizing four periods. The initial discovery period (1845-1974) is characterized by description mainly of sporocarp-forming species and the proposal of a classification for these fungi. The following alpha taxonomy period (1975-1989) established a solid morphological basis for species identification and classification, resulting in a profuse description of new species and a need to standardize the nomenclature of spore subcellular structures. The cladistics period from 1990 to 2000 saw the first cladistic classification of AMF based on phenotypic characters only. At the end of this period, genetic characters played a role in defining taxa and elucidating evolutionary relationships within the group. The most recent phylogenetic synthesis period (2001 to present) started with the proposal of a new classification based on genetic characters using sequences of the multicopy rRNA genes.

  2. Wetland dicots and monocots differ in colonization by arbuscular mycorrhizal fungi and dark septate endophytes.

    PubMed

    Weishampel, Peter A; Bedford, Barbara L

    2006-10-01

    As an initial step towards evaluating whether mycorrhizas influence composition and diversity in calcareous fen plant communities, we surveyed root colonization by arbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi (DSE) in 67 plant species in three different fens in central New York State (USA). We found colonization by AMF and DSE in most plant species at all three sites, with the type and extent of colonization differing between monocots and dicots. On average, AMF colonization was higher in dicots (58+/-3%, mean+/-SE) than in monocots (13+/-4%) but DSE colonization followed the opposite trend (24+/-3% in monocots and 9+/-1% in dicots). In sedges and cattails, two monocot families that are often abundant in fens and other wetlands, AMF colonization was usually very low (<10%) in five species and completely absent in seven others. However, DSE colonization in these species was frequently observed. Responses of wetland plants to AMF and DSE are poorly understood, but in the fen communities surveyed, dicots appear to be in a better position to respond to AMF than many of these more abundant monocots (e.g., sedges and cattails). In contrast, these monocots may be more likely to respond to DSE. Future work directed towards understanding the response of these wetland plants to AMF and DSE should provide insight into the roles these fungal symbionts play in influencing diversity in fen plant communities.

  3. Contrasting preferences of arbuscular mycorrhizal and dark septate fungi colonizing boreal and subarctic Avenella flexuosa.

    PubMed

    Kauppinen, M; Raveala, K; Wäli, P R; Ruotsalainen, A L

    2014-04-01

    Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungi are ubiquitous in grass roots, but their colonizations may vary according to latitudinal gradient and site conditions. We investigated how vegetation zone (boreal vs. subarctic), humus thickness, and site openness affect root fungal colonizations of the grass Avenella flexuosa. More precisely, we hypothesized that AM and DSE fungal colonizations would have different responses to environmental conditions such that AM fungi could be more common in boreal zone, whereas we expected DSE fungi to be more affected by the amount of humus. We found site openness to affect AM and DSE fungi in a contrasting manner, in interaction with the vegetation zone. AM colonization was high at open coastal dunes, whereas DSE fungi were more common at forested sites, in the boreal zone. Humus thickness affected AM fungi negatively and DSE fungi positively. To conclude, the observed AM and DSE fungal colonization patterns were largely contrasting. AM fungi were favored in seashore conditions characterized by thin humus layer, whereas DSE fungi were favored in conditions of higher humus availability.

  4. Species richness of arbuscular mycorrhizal fungi: associations with grassland plant richness and biomass.

    PubMed

    Hiiesalu, Inga; Pärtel, Meelis; Davison, John; Gerhold, Pille; Metsis, Madis; Moora, Mari; Öpik, Maarja; Vasar, Martti; Zobel, Martin; Wilson, Scott D

    2014-07-01

    Although experiments show a positive association between vascular plant and arbuscular mycorrhizal fungal (AMF) species richness, evidence from natural ecosystems is scarce. Furthermore, there is little knowledge about how AMF richness varies with belowground plant richness and biomass. We examined relationships among AMF richness, above- and belowground plant richness, and plant root and shoot biomass in a native North American grassland. Root-colonizing AMF richness and belowground plant richness were detected from the same bulk root samples by 454-sequencing of the AMF SSU rRNA and plant trnL genes. In total we detected 63 AMF taxa. Plant richness was 1.5 times greater belowground than aboveground. AMF richness was significantly positively correlated with plant species richness, and more strongly with below- than aboveground plant richness. Belowground plant richness was positively correlated with belowground plant biomass and total plant biomass, whereas aboveground plant richness was positively correlated only with belowground plant biomass. By contrast, AMF richness was negatively correlated with belowground and total plant biomass. Our results indicate that AMF richness and plant belowground richness are more strongly related with each other and with plant community biomass than with the plant aboveground richness measures that have been almost exclusively considered to date.

  5. Red/Far Red Light Controls Arbuscular Mycorrhizal Colonization via Jasmonic Acid and Strigolactone Signaling.

    PubMed

    Nagata, Maki; Yamamoto, Naoya; Shigeyama, Tamaki; Terasawa, Yohei; Anai, Toyoaki; Sakai, Tatsuya; Inada, Sayaka; Arima, Susumu; Hashiguchi, Masatsugu; Akashi, Ryo; Nakayama, Hideyuki; Ueno, Daisuke; Hirsch, Ann M; Suzuki, Akihiro

    2015-11-01

    Establishment of a nitrogen-fixing symbiosis between legumes and rhizobia not only requires sufficient photosynthate, but also the sensing of the ratio of red to far red (R/FR) light. Here, we show that R/FR light sensing also positively influences the arbuscular mycorrhizal (AM) symbiosis of a legume and a non-legume through jasmonic acid (JA) and strigolactone (SL) signaling. The level of AM colonization in high R/FR light-grown tomato and Lotus japonicus significantly increased compared with that determined for low R/FR light-grown plants. Transcripts for JA-related genes were also elevated under high R/FR conditions. The root exudates derived from high R/FR light-grown plants contained more (+)-5-deoxystrigol, an AM-fungal hyphal branching inducer, than those from low R/FR light-grown plants. In summary, high R/FR light changes not only the levels of JA and SL synthesis, but also the composition of plant root exudates released into the rhizosphere, in this way augmenting the AM symbiosis.

  6. Arbuscular mycorrhizal fungal community response to warming and nitrogen addition in a semiarid steppe ecosystem.

    PubMed

    Kim, Yong-Chan; Gao, Cheng; Zheng, Yong; He, Xin-Hua; Yang, Wei; Chen, Liang; Wan, Shi-Qiang; Guo, Liang-Dong

    2015-05-01

    Understanding the response of arbuscular mycorrhizal (AM) fungi to warming and nitrogen (N) fertilization is critical to assess the impact of anthropogenic disturbance on ecosystem functioning under global climate change scenarios. In this study, AM fungal communities were examined in a full factorial design with warming and N addition in a semiarid steppe in northern China. Warming significantly increased AM fungal spore density, regardless of N addition, whilst N addition significantly decreased AM fungal extraradical hyphal density, regardless of warming. A total of 79 operational taxonomic units (OTUs) of AM fungi were recovered by 454 pyrosequencing of SSU rDNA. Warming, but not N addition, had a significant positive effect on AM fungal OTU richness, while warming and N addition significantly increased AM fungal Shannon diversity index. N addition, but not warming, significantly altered the AM fungal community composition. Furthermore, the changes in AM fungal community composition were associated with shifts in plant community composition indirectly caused by N addition. These findings highlight the different effects of warming and N addition on AM fungal communities and contribute to understanding AM fungal community responses to global environmental change scenarios in semiarid steppe ecosystems.

  7. Increase of multi-metal tolerance of three leguminous plants by arbuscular mycorrhizal fungi colonization.

    PubMed

    Lin, Ai-Jun; Zhang, Xu-Hong; Wong, Ming-Hung; Ye, Zhi-Hong; Lou, Lai-Qing; Wang, You-Shan; Zhu, Yong-Guan

    2007-12-01

    A greenhouse pot experiment was conducted to investigate the effects of the colonization of arbuscular mycorrhizal fungus (AMF) Glomus mosseae on the growth and metal uptake of three leguminous plants (Sesbania rostrata, Sesbania cannabina, Medicago sativa) grown in multi-metal contaminated soil. AMF colonization increased the growth of the legumes, indicating that AMF colonization increased the plant's resistance to heavy metals. It also significantly stimulated the formation of root nodules and increased the N and P uptake of all of the tested leguminous plants, which might be one of the tolerance mechanisms conferred by AMF. Compared with the control, colonization by G. mosseae decreased the concentration of metals, such as Cu, in the shoots of the three legumes, indicating that the decreased heavy metals uptake and growth dilution were induced by AMF treatment, thereby reducing the heavy metal toxicity to the plants. The root/shoot ratios of Cu in the three legumes and Zn in M. sativa were significantly increased (P<0.05) with AMF colonization, indicating that heavy metals were immobilized by the mycorrhiza and the heavy metal translocations to the shoot were decreased.

  8. Effect of arbuscular mycorrhizal fungi on phytoextraction by corn (Zea mays) of lead-contaminated soil.

    PubMed

    Hovsepyan, A; Greipsson, S

    2004-01-01

    The role of arbuscular mycorrhizal fungi (AMF) in lead (Pb) uptake by corn (Zea mays) grown in soil supplemented with Pb was examined. Plants were subjected to four Pb levels: 0 (control); 10 (low); 100 (medium); and 500 mg L(-1) (high). At each Pb level, plants were grown in soil without and with fungicide (benomyl) (20 mg kg(-1)) to suppress AMF activity. Benomyl significantly reduced AMF colonization at high. medium, and zero Pb exposures. Benomyl application resulted in significantly lower concentrations of phosphorus in leaves at low and medium Pb exposures. The benomyl-treated plants had higher Pb and manganese concentrations in leaves than plants not treated with benomyl. In addition, benomyl-treated plants had generally lower concentrations of zinc and copper in leaves than plants not treated with benomyl. These results suggest that the role of AMF in heavy metal uptake is metal specific. Based on this work, the use of benomyl on soils contaminated with Pb can be recommended in phytoextraction.

  9. Diversity of arbuscular mycorrhizal fungus populations in heavy-metal-contaminated soils.

    PubMed

    Del Val, C; Barea, J M; Azcón-Aguilar, C

    1999-02-01

    High concentrations of heavy metals have been shown to adversely affect the size, diversity, and activity of microbial populations in soil. The aim of this work was to determine how the diversity of arbuscular mycorrhizal (AM) fungi is affected by the addition of sewage-amended sludge containing heavy metals in a long-term experiment. Due to the reduced number of indigenous AM fungal (AMF) propagules in the experimental soils, several host plants with different life cycles were used to multiply indigenous fungi. Six AMF ecotypes were found in the experimental soils, showing consistent differences with regard to their tolerance to the presence of heavy metals. AMF ecotypes ranged from very sensitive to the presence of metals to relatively tolerant to high rates of heavy metals in soil. Total AMF spore numbers decreased with increasing amounts of heavy metals in the soil. However, species richness and diversity as measured by the Shannon-Wiener index increased in soils receiving intermediate rates of sludge contamination but decreased in soils receiving the highest rate of heavy-metal-contaminated sludge. Relative densities of most AMF species were also significantly influenced by soil treatments. Host plant species exerted a selective influence on AMF population size and diversity. We conclude based on the results of this study that size and diversity of AMF populations were modified in metal-polluted soils, even in those with metal concentrations that were below the upper limits accepted by the European Union for agricultural soils.

  10. Diversity of Arbuscular Mycorrhizal Fungus Populations in Heavy-Metal-Contaminated Soils

    PubMed Central

    Del Val, C.; Barea, J. M.; Azcón-Aguilar, C.

    1999-01-01

    High concentrations of heavy metals have been shown to adversely affect the size, diversity, and activity of microbial populations in soil. The aim of this work was to determine how the diversity of arbuscular mycorrhizal (AM) fungi is affected by the addition of sewage-amended sludge containing heavy metals in a long-term experiment. Due to the reduced number of indigenous AM fungal (AMF) propagules in the experimental soils, several host plants with different life cycles were used to multiply indigenous fungi. Six AMF ecotypes were found in the experimental soils, showing consistent differences with regard to their tolerance to the presence of heavy metals. AMF ecotypes ranged from very sensitive to the presence of metals to relatively tolerant to high rates of heavy metals in soil. Total AMF spore numbers decreased with increasing amounts of heavy metals in the soil. However, species richness and diversity as measured by the Shannon-Wiener index increased in soils receiving intermediate rates of sludge contamination but decreased in soils receiving the highest rate of heavy-metal-contaminated sludge. Relative densities of most AMF species were also significantly influenced by soil treatments. Host plant species exerted a selective influence on AMF population size and diversity. We conclude based on the results of this study that size and diversity of AMF populations were modified in metal-polluted soils, even in those with metal concentrations that were below the upper limits accepted by the European Union for agricultural soils. PMID:9925606

  11. Effects of inoculation with arbuscular mycorrhizal fungi on maize grown in multi-metal contaminated soils.

    PubMed

    Liang, Chang-Cong; Li, Tao; Xiao, Yan-ping; Liu, Mao-Jun; Zhang, Han-Bo; Zhao, Zhi-Wei

    2009-01-01

    Pot culture experiments were established to determine the effects of colonization by arbuscular mycorrhizal fungi (AMF) (Glomus mosseae and G. sp) on maize (Zea mays L.) grown in Pb, Zn, and Cd complex contaminated soils. AMF and non-AMF inoculated maize were grown in sterilized substrates and subjected to different soil heavy metal (Pb, Zn, Cd) concentrations. The root and shoot biomasses of inoculated maize were significantly higher than those of non-inoculated maize. Pb, Zn, and Cd concentrations in roots were significantly higher than those in shoots in both the inoculated and non-inoculated maize, indicating the heavy metals mostly accumulated in the roots of maize. The translocation rates of Pb, Zn, and Cd from roots to shoots were not significantly difference between inoculated and non-inoculated maize. However, at high soil heavy metal concentrations, Pb, Zn, and Cd in the shoots and Pb in the roots of inoculated maize were significantly reduced by about 50% compared to the non-inoculated maize. These results indicated that AMF could promote maize growth and decrease the uptake of these heavy metals at higher soil concentrations, thus protecting their hosts from the toxicity of heavy metals in Pb, Zn, and Cd complex contaminated soils.

  12. Heavy-metal stress and developmental patterns of arbuscular mycorrhizal fungi.

    PubMed

    Pawlowska, Teresa E; Charvat, Iris

    2004-11-01

    The rate of global deposition of Cd, Pb, and Zn has decreased over the past few decades, but heavy metals already in the soil may be mobilized by local and global changes in soil conditions and exert toxic effects on soil microorganisms. We examined in vitro effects of Cd, Pb, and Zn on critical life stages in metal-sensitive ecotypes of arbuscular mycorrhizal (AM) fungi, including spore germination, presymbiotic hyphal extension, presymbiotic sporulation, symbiotic extraradical mycelium expansion, and symbiotic sporulation. Despite long-term culturing under the same low-metal conditions, two species, Glomus etunicatum and Glomus intraradices, had different levels of sensitivity to metal stress. G. etunicatum was more sensitive to all three metals than was G. intraradices. A unique response of increased presymbiotic hyphal extension occurred in G. intraradices exposed to Cd and Pb. Presymbiotic hyphae of G. intraradices formed presymbiotic spores, whose initiation was more affected by heavy metals than was presymbiotic hyphal extension. In G. intraradices grown in compartmentalized habitats with only a portion of the extraradical mycelium exposed to metal stress, inhibitory effects of elevated metal concentrations on symbiotic mycelial expansion and symbiotic sporulation were limited to the metal-enriched compartment. Symbiotic sporulation was more sensitive to metal exposure than symbiotic mycelium expansion. Patterns exhibited by G. intraradices spore germination, presymbiotic hyphal extension, symbiotic extraradical mycelium expansion, and sporulation under elevated metal concentrations suggest that AM fungi may be able to survive in heavy metal-contaminated environments by using a metal avoidance strategy.

  13. Heavy-Metal Stress and Developmental Patterns of Arbuscular Mycorrhizal Fungi

    PubMed Central

    Pawlowska, Teresa E.; Charvat, Iris

    2004-01-01

    The rate of global deposition of Cd, Pb, and Zn has decreased over the past few decades, but heavy metals already in the soil may be mobilized by local and global changes in soil conditions and exert toxic effects on soil microorganisms. We examined in vitro effects of Cd, Pb, and Zn on critical life stages in metal-sensitive ecotypes of arbuscular mycorrhizal (AM) fungi, including spore germination, presymbiotic hyphal extension, presymbiotic sporulation, symbiotic extraradical mycelium expansion, and symbiotic sporulation. Despite long-term culturing under the same low-metal conditions, two species, Glomus etunicatum and Glomus intraradices, had different levels of sensitivity to metal stress. G. etunicatum was more sensitive to all three metals than was G. intraradices. A unique response of increased presymbiotic hyphal extension occurred in G. intraradices exposed to Cd and Pb. Presymbiotic hyphae of G. intraradices formed presymbiotic spores, whose initiation was more affected by heavy metals than was presymbiotic hyphal extension. In G. intraradices grown in compartmentalized habitats with only a portion of the extraradical mycelium exposed to metal stress, inhibitory effects of elevated metal concentrations on symbiotic mycelial expansion and symbiotic sporulation were limited to the metal-enriched compartment. Symbiotic sporulation was more sensitive to metal exposure than symbiotic mycelium expansion. Patterns exhibited by G. intraradices spore germination, presymbiotic hyphal extension, symbiotic extraradical mycelium expansion, and sporulation under elevated metal concentrations suggest that AM fungi may be able to survive in heavy metal-contaminated environments by using a metal avoidance strategy. PMID:15528529

  14. Arbuscular mycorrhizal fungi regulate soil respiration and its response to precipitation change in a semiarid steppe

    NASA Astrophysics Data System (ADS)

    Zhang, Bingwei; Li, Shan; Chen, Shiping; Ren, Tingting; Yang, Zhiqiang; Zhao, Hanlin; Liang, Yu; Han, Xingguo

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) are critical links in plant–soil continuum and play a critical role in soil carbon cycles. Soil respiration, one of the largest carbon fluxes in global carbon cycle, is sensitive to precipitation change in semiarid ecosystems. In this study, a field experiment with fungicide application and water addition was conducted during 2010–2013 in a semiarid steppe in Inner Mongolia, China, and soil respiration was continuously measured to investigate the influences of AMF on soil respiration under different precipitation regimes. Results showed that soil respiration was promoted by water addition treatment especially during drought seasons, which induced a nonlinear response of soil respiration to precipitation change. Fungicide application suppressed AMF root colonization without impacts on soil microbes. AMF suppression treatment accelerated soil respiration with 2.7, 28.5 and 37.6 g C m‑2 across three seasons, which were mainly caused by the enhanced heterotrophic component. A steeper response of soil respiration rate to precipitation was found under fungicide application treatments, suggesting a greater dampening effect of AMF on soil carbon release as water availability increased. Our study highlighted the importance of AMF on soil carbon stabilization and sequestration in semiarid steppe ecosystems especially during wet seasons.

  15. Enhanced Pb Absorption by Hordeum vulgare L. and Helianthus annuus L. Plants Inoculated with an Arbuscular Mycorrhizal Fungi Consortium.

    PubMed

    Arias, Milton Senen Barcos; Peña-Cabriales, Juan José; Alarcón, Alejandro; Maldonado Vega, María

    2015-01-01

    The effect of an arbuscular mycorrhizal fungi (AMF) consortium conformed by (Glomus intraradices, Glomus albidum, Glomus diaphanum, and Glomus claroideum) on plant growth and absorption of Pb, Fe, Na, Ca, and (32)P in barley (Hordeum vulgare L.) and sunflower (Helianthus annuus L.) plants was evaluated. AMF-plants and controls were grown in a substrate amended with powdered Pb slag at proportions of 0, 10, 20, and 30% v/v equivalent to total Pb contents of 117; 5,337; 13,659, and 19,913 mg Pb kg(-1) substrate, respectively. Mycorrhizal root colonization values were 70, 94, 98, and 90%, for barley and 91, 97, 95, and 97%, for sunflower. AMF inoculum had positive repercussions on plant development of both crops. Mycorrhizal barley absorbed more Pb (40.4 mg Pb kg(-1)) shoot dry weight than non-colonized controls (26.5 mg Pb kg(-1)) when treated with a high Pb slag dosage. This increase was higher in roots than shoots (650.0 and 511.5 mg Pb kg(-1) root dry weight, respectively). A similar pattern was found in sunflower. Plants with AMF absorbed equal or lower amounts of Fe, Na and Ca than controls. H. vulgare absorbed more total P (1.0%) than H. annuus (0.9%). The arbuscular mycorrizal consortium enhanced Pb extraction by plants.

  16. Seven years of carbon dioxide enrichment, nitrogen fertilization and plant diversity influence arbuscular mycorrhizal fungi in a grassland ecosystem.

    PubMed

    Antoninka, Anita; Reich, Peter B; Johnson, Nancy Collins

    2011-10-01

    • We tested the prediction that the abundance and diversity of arbuscular mycorrhizal (AM) fungi are influenced by resource availability and plant community composition by examining the joint effects of carbon dioxide (CO(2) ) enrichment, nitrogen (N) fertilization and plant diversity on AM fungi. • We quantified AM fungal spores and extramatrical hyphae in 176 plots after 7 yr of treatment with all combinations of ambient or elevated CO(2) (368 or 560 ppm), with or without N fertilization (0 or 4 g Nm(-2) ), and one (monoculture) or 16 host plant species (polyculture) in the BioCON field experiment at Cedar Creek Ecosystem Science Reserve, Minnesota, USA. • Extramatrical hyphal lengths were increased by CO(2) enrichment, whereas AM spore abundance decreased with N fertilization. Spore abundance, morphotype richness and extramatrical hyphal lengths were all greater in monoculture plots. A structural equation model showed AM fungal biovolume was most influenced by CO(2) enrichment, plant community composition and plant richness, whereas spore richness was most influenced by fungal biovolume, plant community composition and plant richness. • Arbuscular mycorrhizal fungi responded to differences in host community and resource availability, suggesting that mycorrhizal functions, such as carbon sequestration and soil stability, will be affected by global change.

  17. Effect of arbuscular mycorrhizal inoculation on water status and photosynthesis of Populus cathayana males and females under water stress.

    PubMed

    Li, Zhen; Wu, Na; Liu, Ting; Chen, Hui; Tang, Ming

    2015-02-27

    Drought is one of the most serious environmental limitations for poplar growth. Although the ways in which plants deal with water stress and the effects of arbuscular mycorrhizal (AM) formation have been well documented, little is known about how the male and female plants of Populus cathayana respond to drought and AM formation. We also aimed to investigate the potential role of AM fungi in maintaining gender balance. We tested the impact of drought and AM formation on water status and photosynthesis. The results suggested that both sexes showed similar responses to water stress: drought decreased the growth of stem length (GSL), growth of ground diameter (GGD), relative water content (RWC), increased the relative electrolyte leakage (REL), and limited the photosynthesis and chlorophyll fluorescence indexes. However, the responses of the two sexes to drought and AM formation differed to some extent. AM formation had positive effects on RWC, photosynthesis and the intrinsic water use efficiency (WUEi) but negative effects on the REL of males and females, especially under drought. AM formation enhanced the maximum quantum yield of photosystem II (PSII) (Fv/Fm), the actual quantum yield of PSII (ΦPSII), non-photochemical quenching (qN) and photochemical quenching (qP) under drought conditions, and had no significant effects under well-watered conditions except on the qP of males. Principal component analysis showed that males were significantly more drought tolerant than females, and AM formation enhanced drought tolerance, particularly among males, which suggested that AM fungi are beneficial for ecological stability and for P. cathayana survival under drought conditions.

  18. The arbuscular mycorrhizal Rhizophagus irregularis activates storage lipid biosynthesis to cope with the benzo[a]pyrene oxidative stress.

    PubMed

    Calonne, Maryline; Fontaine, Joël; Debiane, Djouher; Laruelle, Frédéric; Grandmougin-Ferjani, Anne; Lounès-Hadj Sahraoui, Anissa

    2014-01-01

    The phytoremediation assisted by arbuscular mycorrhizal fungi (AMF) could constitute an ecological and economic method to restore polycyclic aromatic hydrocarbon (PAH) polluted soils. Unfortunately, little is known about the PAH impact on the beneficial symbiotic AMF. Using radiolabelling experiments, our work aims to understand how benzo[a]pyrene (B[a]P), a representative of high molecular weight PAH, acts on the AMF lipid metabolism. Our results showed decreases in the sterol precursors as well as in total phospholipid quantities, in link with the [1-(14)C]acetate incorporation decreases in these lipids. Interestingly, a concomitant increase of [1-(14)C]acetate incorporation by 29.5% into phosphatidylcholine with its content decrease in Rhizophagus irregularis extraradical mycelium was observed, suggesting a membrane regeneration. A second concomitant increase (estimated to 69%) of [1-(14)C]acetate incorporation into triacylglycerols (TAG) with the content decrease was also observed. This suggests a fungal TAG biosynthesis activation probably to offset the decrease in storage lipid content when the fungus was grown under B[a]P pollution. In addition, our findings showed that lipase activity was induced by more than 3 fold in the presence of B[a]P in comparison to the control indicating that the drop in TAG content could be a consequence of their active degradation. Taken together, our data suggest the involvement of the fungal TAG metabolism to cope B[a]P toxicity through two means: (i) by providing carbon skeletons and energy necessary for membrane regeneration and/or for B[a]P translocation and degradation as well as (ii) by activating the phosphatidic acid and hexose metabolisms which may be involved in cellular stress defence.

  19. Carlactone-type strigolactones and their synthetic analogues as inducers of hyphal branching in arbuscular mycorrhizal fungi.

    PubMed

    Mori, Narumi; Nishiuma, Kenta; Sugiyama, Takuya; Hayashi, Hideo; Akiyama, Kohki

    2016-10-01

    Hyphal branching in the vicinity of host roots is a host recognition response of arbuscular mycorrhizal fungi. This morphological event is elicited by strigolactones. Strigolactones are carotenoid-derived terpenoids that are synthesized from carlactone and its oxidized derivatives. To test the possibility that carlactone and its oxidized derivatives might act as host-derived precolonization signals in arbuscular mycorrhizal symbiosis, carlactone, carlactonoic acid, and methyl carlactonoate as well as monohydroxycarlactones, 4-, 18-, and 19-hydroxycarlactones, were synthesized chemically and evaluated for hyphal branching-inducing activity in germinating spores of the arbuscular mycorrhizal fungus Gigaspora margarita. Hyphal branching activity was found to correlate with the degree of oxidation at C-19 methyl. Carlactone was only weakly active (100 ng/disc), whereas carlactonoic acid showed comparable activity to the natural canonical strigolactones such as strigol and sorgomol (100 pg/disc). Hydroxylation at either C-4 or C-18 did not significantly affect the activity. A series of carlactone analogues, named AD ester and AA'D diester, was synthesized by reacting formyl Meldrum's acid with benzyl, cyclohexylmethyl, and cyclogeranyl alcohols (the A-ring part), followed by coupling of the potassium enolates of the resulting formylacetic esters with the D-ring butenolide. AD ester analogues exhibited moderate activity (1 ng-100 pg/disc), while AA'D diester analogues having cyclohexylmethyl and cyclogeranyl groups were highly active on the AM fungus (10 pg/disc). These results indicate that the oxidation of methyl to carboxyl at C-19 in carlactone is a prerequisite but BC-ring formation is not essential to show hyphal branching activity comparable to that of canonical strigolactones.

  20. Effect of Rhizobium and arbuscular mycorrhizal fungi inoculation on electrolyte leakage in Phaseolus vulgaris roots overexpressing RbohB.

    PubMed

    Arthikala, Manoj-Kumar; Nava, Noreide; Quinto, Carmen

    2015-01-01

    Respiratory oxidative burst homolog (RBOH)-mediated reactive oxygen species (ROS) regulate a wide range of biological functions in plants. They play a critical role in the symbiosis between legumes and nitrogen-fixing bacteria or arbuscular mycorrhizal (AM) fungi. For instance, overexpression of PvRbohB enhances nodule numbers, but reduces mycorrhizal colonization in Phaseolus vulgaris hairy roots and downregulation has the opposite effect. In the present study, we assessed the effect of both rhizobia and AM fungi on electrolyte leakage in transgenic P. vulgaris roots overexpressing (OE) PvRbohB. We demonstrate that elevated levels of electrolyte leakage in uninoculated PvRbohB-OE transgenic roots were alleviated by either Rhizobium or AM fungi symbiosis, with the latter interaction having the greater effect. These results suggest that symbiont colonization reduces ROS elevated electrolyte leakage in P. vulgaris root cells.

  1. Effect of Rhizobium and arbuscular mycorrhizal fungi inoculation on electrolyte leakage in Phaseolus vulgaris roots overexpressing RbohB

    PubMed Central

    Arthikala, Manoj-Kumar; Nava, Noreide; Quinto, Carmen

    2015-01-01

    Respiratory oxidative burst homolog (RBOH)-mediated reactive oxygen species (ROS) regulate a wide range of biological functions in plants. They play a critical role in the symbiosis between legumes and nitrogen-fixing bacteria or arbuscular mycorrhizal (AM) fungi. For instance, overexpression of PvRbohB enhances nodule numbers, but reduces mycorrhizal colonization in Phaseolus vulgaris hairy roots and downregulation has the opposite effect. In the present study, we assessed the effect of both rhizobia and AM fungi on electrolyte leakage in transgenic P. vulgaris roots overexpressing (OE) PvRbohB. We demonstrate that elevated levels of electrolyte leakage in uninoculated PvRbohB-OE transgenic roots were alleviated by either Rhizobium or AM fungi symbiosis, with the latter interaction having the greater effect. These results suggest that symbiont colonization reduces ROS elevated electrolyte leakage in P. vulgaris root cells. PMID:25946118

  2. Remediation of PAH-contaminated soil by the combination of tall fescue, arbuscular mycorrhizal fungus and epigeic earthworms.

    PubMed

    Lu, Yan-Fei; Lu, Mang

    2015-03-21

    A 120-day experiment was performed to investigate the effect of a multi-component bioremediation system consisting of tall fescue (Festuca arundinacea), arbuscular mycorrhizal fungus (AMF) (Glomus caledoniun L.), and epigeic earthworms (Eisenia foetida) for cleaning up polycyclic aromatic hydrocarbons (PAHs)-contaminated soil. Inoculation with AMF and/or earthworms increased plant yield and PAH accumulation in plants. However, PAH uptake by tall fescue accounted for a negligible portion of soil PAH removal. Mycorrhizal tall fescue significantly enhanced PAH dissipation, PAH degrader density and polyphenol oxidase activity in soil. The highest PAH dissipation (93.4%) was observed in the combination treatment: i.e., AMF+earthworms+tall fescue, in which the soil PAH concentration decreased from an initial value of 620 to 41 mg kg(-1) in 120 days. This concentration is below the threshold level required for Chinese soil PAH quality (45 mg kg(-1) dry weight) for residential use.

  3. Role of arbuscular mycorrhizal fungus Rhizophagus custos in the dissipation of PAHs under root-organ culture conditions.

    PubMed

    Aranda, Elisabet; Scervino, José Martín; Godoy, Patricia; Reina, Rocío; Ocampo, Juan Antonio; Wittich, Regina-Michaela; García-Romera, Inmaculada

    2013-10-01

    Polycyclic aromatic hydrocarbons (PAHs) are one of the most common contaminants in soil. Arbuscular mycorrhizal (AM) fungi make host plants resistant to pollutants. This study aims to evaluate the impact of anthracene, phenanthrene and dibenzothiophene on the AM fungus Rhizophagus custos, isolated from soil contaminated by heavy metals and PAHs, under monoxenic conditions. We found a high level of tolerance in R. custos to the presence of PAHs, especially in the case of anthracene, in which no negative effect on AM-colonized root dry weight (root yield) was observed, and also a decrease in the formation of anthraquinone was detected. Increased PAH dissipation in the mycorrhizal root culture medium was observed; however, dissipation was affected by the level of concentration and the specific PAH, which lead us to a better understanding of the possible contribution of AM fungi, and in particular R. custos, to pollutant removal.

  4. Community structure of arbuscular mycorrhizal fungi associated to Veronica rechingeri at the Anguran zinc and lead mining region.

    PubMed

    Zarei, M; König, S; Hempel, S; Nekouei, M Khayam; Savaghebi, Gh; Buscot, F

    2008-12-01

    Root colonization and diversity of arbuscular mycorrhizal fungi (AMF) were analyzed in Veronica rechingeri growing in heavy metal (HM) and non-polluted soils of the Anguran Zn and Pb mining region (Iran). Three species could be separated morphologically, while phylogenetic analyses after PCR amplification of the ITS region followed by RFLP and sequencing revealed seven different AMF sequence types all within the genus Glomus. Rarefaction analysis confirmed exhaustive molecular characterization of the AMF diversity present within root samples. Increasing heavy metal contamination between the sites studied was accompanied by a decrease in AMF spore numbers, mycorrhizal colonization parameters and the number of AMF sequence types colonizing the roots. Some AMF sequence types were only found at sites with the highest and lowest soil HM contents, respectively.

  5. Effect of Various Organic Matter stimulates Bacteria and Arbuscular Mycorrhizal Fungi Plantations on Eroded Slopes in Nepal

    NASA Astrophysics Data System (ADS)

    Shrestha Vaidya, G.; Shrestha, K.; Wallander, H.

    2009-04-01

    Erosion resulting from landslides is a serious problem in mountainous countries such as Nepal. To restore such sites it is essential to establish plant cover that protects the soil and reduces erosion. Trees and shrubs on the lower hillsides in Nepal form symbiosis with arbuscular mycorrhizal (AM) fungi and these fungi are important for the uptake of mineral nutrients from the soil. In addition, the mycelia formed by these fungi have an important function in stabilizing the soil. The success of plantations of these eroded slopes is therefore highly dependent on the extent of mycorrhizal colonization of the plants. Mycorrhizal fungi growing in symbiosis with plants are essential in this respect because they improve both plant and nutrient uptake and soil structure. We investigated the influence of organic matter and P amendment on recently produced biomass of bacteria and arbuscular mycorrhizal (AM) fungi in eroded slopes in Nepal. Eroded soil mixed with different types of organic matter was placed in mesh bags which were buried around the trees of Bauhinia purpurea and Leucaena diversifolia .This experiment were done in two seasons ( (the wet and the dry season). Signature fatty acids were used to determine bacterial and AM fungal biomass after the six month intervals. The amount and composition of AM fungal spores were analyzed in the mesh bags from the wet and dry seasons. More microbial biomass was produced during wet season than during dry season. Further more, organic matter addition enhanced the production of AM fungal and bacterial biomass during both seasons. The positive influence of organic matter addition on AM fungi could be an important contribution to plant survival, growth and nutrient composition in the soil in plantations on eroded slopes. Different AM spore communities and bacterial profiles were obtained with different organic amendments and this suggests a possible way of selecting for specific microbial communities in the management of eroded

  6. Arbuscular mycorrhizal colonization in field-collected terrestrial cordate gametophytes of pre-polypod leptosporangiate ferns (Osmundaceae, Gleicheniaceae, Plagiogyriaceae, Cyatheaceae).

    PubMed

    Ogura-Tsujita, Yuki; Hirayama, Yumiko; Sakoda, Aki; Suzuki, Ayako; Ebihara, Atsushi; Morita, Nana; Imaichi, Ryoko

    2016-02-01

    To determine the mycorrhizal status of pteridophyte gametophytes in diverse taxa, the mycorrhizal colonization of wild gametophytes was investigated in terrestrial cordate gametophytes of pre-polypod leptosporangiate ferns, i.e., one species of Osmundaceae (Osmunda banksiifolia), two species of Gleicheniaceae (Diplopterygium glaucum, Dicranopteris linearis), and four species of Cyatheales including tree ferns (Plagiogyriaceae: Plagiogyria japonica, Plagiogyria euphlebia; Cyatheaceae: Cyathea podophylla, Cyathea lepifera). Microscopic observations revealed that 58 to 97% of gametophytes in all species were colonized with arbuscular mycorrhizal (AM) fungi. Fungal colonization was limited to the multilayered midrib (cushion) tissue in all gametophytes examined. Molecular identification using fungal SSU rDNA sequences indicated that the AM fungi in gametophytes primarily belonged to the Glomeraceae, but also included the Claroideoglomeraceae, Gigasporaceae, Acaulosporaceae, and Archaeosporales. This study provides the first evidence for AM fungal colonization of wild gametophytes in the Plagiogyriaceae and Cyatheaceae. Taxonomically divergent photosynthetic gametophytes are similarly colonized by AM fungi, suggesting that mycorrhizal associations with AM fungi could widely occur in terrestrial pteridophyte gametophytes.

  7. Shedding light onto nutrient responses of arbuscular mycorrhizal plants: nutrient interactions may lead to unpredicted outcomes of the symbiosis.

    PubMed

    Corrêa, Ana; Cruz, Cristina; Pérez-Tienda, Jacob; Ferrol, Nuria

    2014-05-01

    The role and importance of arbuscular mycorrhizae (AM) in plant nitrogen (N) nutrition is uncertain. We propose that this be clarified by using more integrative experimental designs, with the use of a gradient of N supply and the quantification of an extensive array of plant nutrient contents. Using such an experimental design, we investigated AM effects on plant N nutrition, whether the mycorrhizal N response (MNR) determines the mycorrhizal growth response (MGR), and how MNR influences plants' C economy. Oryza sativa plants were inoculated with Rhizophagus irregularis or Funneliformis mossae. AM effects were studied along a gradient of N supplies. Biomass, photosynthesis, nutrient and starch contents, mycorrhizal colonization and OsPT11 gene expression were measured. C investment in fungal growth was estimated. Results showed that, in rice, MGR was dependent on AM nutrient uptake effects, namely on the synergy between N and Zn, and not on C expenditure. The supply of C to the fungus was dependent on the plant's nutrient demand, indicated by high shoot C/N or low %N. We conclude that one of the real reasons for the negative MGR of rice, Zn deficiency of AMF plants, would have remained hidden without an experimental design allowing the observation of plants' response to AM along gradients of nutrient concentrations. Adopting more integrative and comprehensive experimental approaches in mycorrhizal studies seems therefore essential if we are to achieve a true understanding of AM function, namely of the mechanisms of C/N exchange regulation in AM.

  8. The roles of arbuscular mycorrhizal fungi (AMF) in phytoremediation and tree-herb interactions in Pb contaminated soil

    DOE PAGES

    Yang, Yurong; Liang, Yan; Han, Xiaozhen; ...

    2016-02-04

    Understanding the roles of arbuscular mycorrhizal fungi (AMF) in plant interaction is essential for optimizing plant distribution to restore degraded ecosystems. Here, our study investigated the effects of AMF and the presence of legume or grass herbs on phytoremediation with a legume tree, Robinia pseudoacacia, in Pb polluted soil. In monoculture, mycorrhizal dependency of legumes was higher than that of grass, and AMF benefited the plant biomass of legumes but had no effect on grass. Mycorrhizal colonization of plant was enhanced by legume neighbors but inhibited by grass neighbor in co-culture system. N, P, S and Mg concentrations of mycorrhizalmore » legumes were larger than these of non-mycorrhizal legumes. Legume herbs decreased soil pH and thereby increased the Pb concentrations of plants. The neighbor effects of legumes shifted from negative to positive with increasing Pb stress levels, whereas grass provided a negative effect on the growth of legume tree. AMF enhanced the competition but equalized growth of legume-legume under unpolluted and Pb stress conditions, respectively. In conclusion, (1) AMF mediate plant interaction through directly influencing plant biomass, and/or indirectly influencing plant photosynthesis, macronutrient acquisition, (2) legume tree inoculated with AMF and co-planted with legume herbs provides an effective way for Pb phytoremediation.« less

  9. Resistance Responses of Potato to Vesicular-Arbuscular Mycorrhizal Fungi under Varying Abiotic Phosphorus Levels.

    PubMed

    McArthur, D A; Knowles, N R

    1992-09-01

    In mycorrhizal symbioses, susceptibility of a host plant to infection by fungi is influenced by environmental factors, especially the availability of soil phosphorus. This study describes morphological and biochemical details of interactions between a vesicular-arbuscular mycorrhizal (VAM) fungus and potato (Solanum tuberosum L. cv Russet Burbank) plants, with a particular focus on the physiological basis for P-induced resistance of roots to infection. Root infection by the VAM fungus Glomus fasciculatum ([Thaxt. sensu Gerdemann] Gerdemann and Trappe) was extensive for plants grown with low abiotic P supply, and plant biomass accumulation was enhanced by the symbiosis. The capacity of excised roots from P-deficient plants to produce ethylene in the presence or absence of exogenous 1-amino cyclopropane-1-carboxylic acid (ACC) was markedly reduced by VAM infection. This apparent inhibition of ACC oxidase (ACC(ox)) activity was localized to areas containing infected roots, as demonstrated in split-root studies. Furthermore, leachate from VAM roots contained a potent water-soluble inhibitor of ethylene generation from exogenous ACC by nonmycorrhizal (NM) roots. The leachate from VAM-infected roots had a higher concentration of phenolics, relative to that from NM roots. Moreover, the rates of ethylene formation and phenolic concentration in leachates from VAM roots were inversely correlated, suggesting that this inhibitor may be of a phenolic nature. The specific activity of extracellular peroxidase recovered in root leachates was not stimulated by VAM infection, although activity on a fresh weight basis was significantly enhanced, reflecting the fact that VAM roots had higher protein content than NM roots. Polyphenol oxidase activity of roots did not differ between NM and VAM roots. These results characterize the low resistance response of P-deficient plants to VAM infection. When plants were grown with higher abiotic P supply, the relative benefit of the VAM symbiosis

  10. Organic Nitrogen-Driven Stimulation of Arbuscular Mycorrhizal Fungal Hyphae Correlates with Abundance of Ammonia Oxidizers.

    PubMed

    Bukovská, Petra; Gryndler, Milan; Gryndlerová, Hana; Püschel, David; Jansa, Jan

    2016-01-01

    Large fraction of mineral nutrients in natural soil environments is recycled from complex and heterogeneously distributed organic sources. These sources are explored by both roots and associated mycorrhizal fungi. However, the mechanisms behind the responses of arbuscular mycorrhizal (AM) hyphal networks to soil organic patches of different qualities remain little understood. Therefore, we conducted a multiple-choice experiment examining hyphal responses to different soil patches within the root-free zone by two AM fungal species (Rhizophagus irregularis and Claroideoglomus claroideum) associated with Medicago truncatula, a legume forming nitrogen-fixing root nodules. Hyphal colonization of the patches was assessed microscopically and by quantitative real-time PCR (qPCR) using AM taxon-specific markers, and the prokaryotic and fungal communities in the patches (pooled per organic amendment treatment) were profiled by 454-amplicon sequencing. Specific qPCR markers were then designed and used to quantify the abundance of prokaryotic taxa showing the strongest correlation with the pattern of AM hyphal proliferation in the organic patches as per the 454-sequencing. The hyphal density of both AM fungi increased due to nitrogen (N)-containing organic amendments (i.e., chitin, DNA, albumin, and clover biomass), while no responses as compared to the non-amended soil patch were recorded for cellulose, phytate, or inorganic phosphate amendments. Abundances of several prokaryotes, including Nitrosospira sp. (an ammonium oxidizer) and an unknown prokaryote with affiliation to Acanthamoeba endosymbiont, which were frequently recorded in the 454-sequencing profiles, correlated positively with the hyphal responses of R. irregularis to the soil amendments. Strong correlation between abundance of these two prokaryotes and the hyphal responses to organic soil amendments by both AM fungi was then confirmed by qPCR analyses using all individual replicate patch samples. Further

  11. Organic Nitrogen-Driven Stimulation of Arbuscular Mycorrhizal Fungal Hyphae Correlates with Abundance of Ammonia Oxidizers

    PubMed Central

    Bukovská, Petra; Gryndler, Milan; Gryndlerová, Hana; Püschel, David; Jansa, Jan

    2016-01-01

    Large fraction of mineral nutrients in natural soil environments is recycled from complex and heterogeneously distributed organic sources. These sources are explored by both roots and associated mycorrhizal fungi. However, the mechanisms behind the responses of arbuscular mycorrhizal (AM) hyphal networks to soil organic patches of different qualities remain little understood. Therefore, we conducted a multiple-choice experiment examining hyphal responses to different soil patches within the root-free zone by two AM fungal species (Rhizophagus irregularis and Claroideoglomus claroideum) associated with Medicago truncatula, a legume forming nitrogen-fixing root nodules. Hyphal colonization of the patches was assessed microscopically and by quantitative real-time PCR (qPCR) using AM taxon-specific markers, and the prokaryotic and fungal communities in the patches (pooled per organic amendment treatment) were profiled by 454-amplicon sequencing. Specific qPCR markers were then designed and used to quantify the abundance of prokaryotic taxa showing the strongest correlation with the pattern of AM hyphal proliferation in the organic patches as per the 454-sequencing. The hyphal density of both AM fungi increased due to nitrogen (N)-containing organic amendments (i.e., chitin, DNA, albumin, and clover biomass), while no responses as compared to the non-amended soil patch were recorded for cellulose, phytate, or inorganic phosphate amendments. Abundances of several prokaryotes, including Nitrosospira sp. (an ammonium oxidizer) and an unknown prokaryote with affiliation to Acanthamoeba endosymbiont, which were frequently recorded in the 454-sequencing profiles, correlated positively with the hyphal responses of R. irregularis to the soil amendments. Strong correlation between abundance of these two prokaryotes and the hyphal responses to organic soil amendments by both AM fungi was then confirmed by qPCR analyses using all individual replicate patch samples. Further

  12. The role of community and population ecology in applying mycorrhizal fungi for improved food security.

    PubMed

    Rodriguez, Alia; Sanders, Ian R

    2015-05-01

    The global human population is expected to reach ∼9 billion by 2050. Feeding this many people represents a major challenge requiring global crop yield increases of up to 100%. Microbial symbionts of plants such as arbuscular mycorrhizal fungi (AMF) represent a huge, but unrealized resource for improving yields of globally important crops, especially in the tropics. We argue that the application of AMF in agriculture is too simplistic and ignores basic ecological principals. To achieve this challenge, a community and population ecology approach can contribute greatly. First, ecologists could significantly improve our understanding of the determinants of the survival of introduced AMF, the role of adaptability and intraspecific diversity of AMF and whether inoculation has a direct or indirect effect on plant production. Second, we call for extensive metagenomics as well as population genomics studies that are crucial to assess the environmental impact that introduction of non-local AMF may have on native AMF communities and populations. Finally, we plead for an ecologically sound use of AMF in efforts to increase food security at a global scale in a sustainable manner.

  13. Prunus persica crop management differentially promotes arbuscular mycorrhizal fungi diversity in a tropical agro-ecosystem.

    PubMed

    Alguacil, Maria del Mar; Torrecillas, Emma; Lozano, Zenaida; Torres, Maria Pilar; Roldán, Antonio

    2014-01-01

    Due to the important role of arbuscular mycorrhizal fungi (AMF) in ecosystem functioning, determination of the effect of management practices on the AMF diversity in agricultural soils is essential for the sustainability of these agro-ecosystems. The objective of this study was to compare the AMF diversity in Prunus persica roots under two types of fertilisation (inorganic, with or without manure) combined with integrated or chemical pest management in a Venezuelan agro-ecosystem. The AM fungal small-subunit (SSU) rRNA genes were subjected to PCR, cloning, sequencing and phylogenetic analyses. Twenty-one different phylotypes were identified: 15 belonged to the genus Glomus, one to Claroideoglomus, two to Paraglomus, one to Acaulospora, one to Scutellospora and one to Archaeospora. The distribution of the AMF community composition differed as a consequence of the treatment effects. The treatment combining organic and inorganic fertilisation with chemical pest control had the highest AMF richness and the treatment combining inorganic fertilisation with chemical pest had the lowest. The real causes and effects of these differences in the AMF community are very difficult to establish, since the crop management regimes tested were composed of several interacting factors. In conclusion, the crop management practices can exert a significant influence on the populations of AMF. The treatment combining organic and inorganic fertilisation with chemical pest control appears to be the most suitable agricultural management strategy with respect to improving the AMF diversity in this crop under tropical conditions, and thus for maintaining the agricultural and environmental sustainability of this agro-ecosystem.

  14. Substantial nitrogen acquisition by arbuscular mycorrhizal fungi from organic material has implications for N cycling.

    PubMed

    Hodge, Angela; Fitter, Alastair H

    2010-08-03

    Arbuscular mycorrhizal (AM) fungi are obligate biotrophs that acquire carbon (C) solely from host plants. AM fungi can proliferate hyphae in, and acquire nitrogen (N) from, organic matter. Although they can transfer some of that N to plants, we tested the hypothesis that organic matter is an important N source for the AM fungi themselves. We grew pairs of plants with and without the AM fungus Glomus hoi in microcosms that allowed only the fungus access to a 15N/13C-labeled organic patch; in some cases, one plant was shaded to reduce C supply to the fungus. The fungal hyphae proliferated vigorously in the patch, irrespective of shading, and increased plant growth and N content; approximately 3% of plant N came from the patch. The extraradical mycelium of the fungus was N-rich (3-5% N) and up to 31% of fungal N came from the patch, confirming the hypothesis. The fungus acquired N as decomposition products, because hyphae were not 13C-enriched. In a second experiment, hyphae of both G. hoi and Glomus mosseae that exploited an organic material patch were also better able to colonize a new host plant, demonstrating a fungal growth response. These findings show that AM fungi can obtain substantial amounts of N from decomposing organic materials and can enhance their fitness as a result. The large biomass and high N demand of AM fungi means that they represent a global N pool equivalent in magnitude to fine roots and play a substantial and hitherto overlooked role in the nitrogen cycle.

  15. Effects of flower dimorphism and light environment on arbuscular mycorrhizal colonisation in a cleistogamous herb.

    PubMed

    Parra-Tabla, V; Munguía-Rosas, M; Campos-Navarrete, M J; Ramos-Zapata, J A

    2015-01-01

    Although it is known that floral dimorphism contributes to the maintenance of mixed breeding systems, the consequences of producing progeny of a contrasting genetic background and seeds with differential resource allocation has been practically ignored regarding establishment of belowground organisms-plant interactions. This article evaluates the combined effect of floral dimorphism with cross type and light environment on interactions between Ruellia nudiflora and arbuscular mycorrhizal fungi (AMF). R. nudiflora produces cleistogamous (CL) flowers that exhibit obligate self-pollination and chasmogamous (CH) flowers with facultative self- (CHs) or cross- (CHc) pollination. We evaluated the establishment of the plant-AMF interaction in progeny derived from each floral type, under two light conditions (shaded versus open). We established different scenarios depending on the existence of inbreeding depression (ID) and whether the differential resource allocation (DRA) to CH and CL flowers affected the R. nudiflora-AMF interaction. We predicted that under shaded light conditions there might be an intensification of ID, having a negative effect on AMF colonisation. The percentages of hyphae and vesicles in the harvested roots was significantly higher in the shaded plants (F ≥ 4.11, P < 0.05), while progeny of CHc and CHs presented a higher percentage of hyphae and vesicle colonisation compared to CL progeny (F = 15.26, P < 0.01). The results show that DRA to CH flowers and light availability both determines the establishment of R. nudiflora-AMF interaction. The results also suggest that even under stressful light conditions, endogamy does not affect this interaction, which may explain the success of R. nudiflora as an invasive species.

  16. 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.

  17. The effect of different land uses on arbuscular mycorrhizal fungi in the northwestern Black Sea Region.

    PubMed

    Palta, Şahin; Lermi, Ayşe Genç; Beki, Rıdvan

    2016-06-01

    The object of the present research was to establish correlations between the status of root colonization of arbuscular mycorrhizal fungi (AMF) and different types of land use. In order to achieve this aim, rhizosphere soil samples from grassland crops were taken during June and July of 2013 in order to use for determining several soil characteristics. The 27 different taxa and 60 soil samples were collected from the rhizosphere level in the study areas. The existence of AMF was confirmed in 100 % of these plants with different rations of colonization (approximately 12-89 %). Bromus racemosus L. (pasture) was the most dense taxon with the percentage of AMF colonization of 88.9 %, and Trifolium pratense L. (forest) was the least dense taxon with the percentage of AMF colonization of 12.2 % (average 52.0 %). As a result of the statistical analysis, a positive relationship was found between the botanical composition of legumes and AMF colonization (r = 0.35; p = 0.006). However, a negative relationship was determined between botanical composition of other plant families and AMF colonization (r = -0.39; p = 0.002). In addition, a positive relationship was defined between soil pH (H2O) and the root colonization of AMF (r = 0.35; p = 0.005). The pasture had the highest mean value of AMF root colonization. However, the pasture and gap in the forest were in the same group, according to the results of the S-N-K test.

  18. Biodiversity of arbuscular mycorrhizal fungi in roots and soils of two salt marshes.

    PubMed

    Wilde, Petra; Manal, Astrid; Stodden, Marc; Sieverding, Ewald; Hildebrandt, Ulrich; Bothe, Hermann

    2009-06-01

    The occurrence of arbuscular mycorrhizal fungi (AMF) was assessed by both morphological and molecular criteria in two salt marshes: (i) a NaCl site of the island Terschelling, Atlantic Coast, the Netherlands and (ii) a K(2)CO(3) marsh at Schreyahn, Northern Germany. The overall biodiversity of AMF, based on sequence analysis, was comparably low in roots at both sites. However, the morphological spore analyses from soil samples of both sites exhibited a higher AMF biodiversity. Glomus geosporum was the only fungus of the Glomerales that was detected both as spores in soil samples and in roots of the AMF-colonized salt plants Aster tripolium and Puccinellia sp. at both saline sites and on all sampling dates (one exception). In roots, sequences of Glomus intraradices prevailed, but this fungus could not be identified unambiguously from DNA of soil spores. Likewise, Glomus sp. uncultured, only deposited as sequence in the database, was widely detected by DNA sequencing in root samples. All attempts to obtain the corresponding sequences from spores isolated from soil samples failed consistently. A small sized Archaeospora sp. was detected, either/or by morphological and molecular analyses, in roots or soil spores, in dead AMF spores or orobatid mites. The study noted inconsistencies between morphological characterization and identification by DNA sequencing of the 5.8S rDNA-ITS2 region or part of the 18S rDNA gene. The distribution of AMF unlikely followed the salt gradient at both sites, in contrast to the zone formation of plant species. Zygotes of the alga Vaucheria erythrospora (Xanthophyceae) were retrieved and should not be misidentified with AMF spores.

  19. Arbuscular Mycorrhizal Fungal Hyphae Alter Soil Bacterial Community and Enhance Polychlorinated Biphenyls Dissipation

    PubMed Central

    Qin, Hua; Brookes, Philip C.; Xu, Jianming

    2016-01-01

    We investigated the role of arbuscular mycorrhizal fungal (AMF) hyphae in alternation of soil microbial community and Aroclor 1242 dissipation. A two-compartment rhizobox system with double nylon meshes in the central was employed to exclude the influence of Cucurbita pepo L. root exudates on hyphal compartment soil. To assess the quantitative effect of AMF hyphae on soil microbial community, we separated the hyphal compartment soil into four horizontal layers from the central mesh to outer wall (e.g., L1–L4). Soil total PCBs dissipation rates ranged from 35.67% of L4 layer to 57.39% of L1 layer in AMF inoculated treatment, which were significant higher than the 17.31% of the control (P < 0.05). The dissipation rates of tri-, tetrachlorinated biphenyls as well as the total PCBs were significantly correlated with soil hyphal length (P < 0.01). Real-time quantitative PCR results indicated that the Rhodococcus-like bphC gene was 2–3 orders of magnitude more than that of Pseudomonas-like bphC gene, and was found responded positively to AMF. Phylogenetic analyses of the 16S rDNA sequenced by the Illumina Miseq sequencing platform indicated that AMF hyphae altered bacterial community compositions. The phylum Betaproteobacteria and Actinobacteria were dominated in the soil, while Burkholderiales and Actinomycetales were dominated at the order level. Taxa from the Comamonadaceae responded positively to AMF and trichlorinated biphenyl dissipation, while taxa from the Oxalobacteraceae and Streptomycetaceae responded negatively to AMF and PCB congener dissipation. Our results suggested that the AMF hyphal exudates as well as the hyphae per se did have quantitative effects on shaping soil microbial community, and could modify the PCBs dissipation processes consequently. PMID:27379068

  20. Arbuscular mycorrhizal fungal phylogenetic groups differ in affecting host plants along heavy metal levels.

    PubMed

    He, Lei; Yang, Haishui; Yu, Zhenxing; Tang, Jianjun; Xu, Ligen; Chen, Xin

    2014-10-01

    Arbuscular mycorrhizal fungi (AMF) are important components of soil microbial communities, and play important role in plant growth. However, the effects of AMF phylogenetic groups (Glomeraceae and non-Glomeraceae) on host plant under various heavy metal levels are not clear. Here we conducted a meta-analysis to compare symbiotic relationship between AMF phylogenetic groups (Glomeraceae and non-Glomeraceae) and host plant functional groups (herbs vs. trees, and non-legumes vs. legumes) at three heavy metal levels. In the meta-analysis, we calculate the effect size (ln(RR)) by taking the natural logarithm of the response ratio of inoculated to non-inoculated shoot biomass from each study. We found that the effect size of Glomeraceae increased, but the effect size of non-Glomeraceae decreased under high level of heavy metal compared to low level. According to the effect size, both Glomeraceae and non-Glomeraceae promoted host plant growth, but had different effects under various heavy metal levels. Glomeraceae provided more benefit to host plants than non-Glomeraceae did under heavy metal condition, while non-Glomeraceae provided more benefit to host plants than Glomeraceae did under no heavy metal. AMF phylogenetic groups also differed in promoting plant functional groups under various heavy metal levels. Interacting with Glomeraceae, herbs and legumes grew better than trees and non-legumes did under high heavy metal level, while trees and legumes grew better than herbs and non-legumes did under medium heavy metal level. Interacting with non-Glomeraceae, herbs and legumes grew better than trees and non-legumes did under no heavy metal. We suggested that the combination of legume with Glomeraceae could be a useful way in the remediation of heavy metal polluted environment.

  1. Arbuscular mycorrhizal colonization of giant sequoia (Sequoiadendron giganteum) in response to restoration practices.

    PubMed

    Fahey, Catherine; York, Robert A; Pawlowska, Teresa E

    2012-01-01

    Interactions with soil microbiota determine the success of restoring plants to their native habitats. The goal of our study was to understand the effects of restoration practices on interactions of giant sequoia Sequoiadendron giganteum with arbuscular mycorrhizal (AM) fungi (Glomeromycota). Natural regeneration of Sequoiadendron is threatened by the absence of severe fires that create forest canopy gaps. Generating artificial canopy gaps offers an alternative tool for giant sequoia restoration. We investigated the effect of regeneration practices, including (i) sapling location within gaps, (ii) gap size and (iii) soil substrate, on AM fungal colonization of giant sequoia sapling roots in a native giant sequoia grove of the Sierra Nevada, California. We found that the extent of AM fungal root colonization was positively correlated with sapling height and light availability, which were related to the location of the sapling within the gap and the gap size. While colonization frequency by arbuscules in saplings on ash substrate was higher relative to saplings in mineral soil, the total AM fungal root colonization was similar between the substrates. A negative correlation between root colonization by Glomeromycota and non-AM fungal species indicated antagonistic interactions between different classes of root-associated fungi. Using DNA genotyping, we identified six AM fungal taxa representing genera Glomus and Ambispora present in Sequoiadendron roots. Overall, we found that AM fungal colonization of giant sequoia roots was associated with availability of plant-assimilated carbon to the fungus rather than with the AM fungal supply of mineral nutrients to the roots. We conclude that restoration practices affecting light availability and carbon assimilation alter feedbacks between sapling growth and activity of AM fungi in the roots.

  2. Variation of soil arbuscular mycorrhizal fungal communities across land use gradient

    NASA Astrophysics Data System (ADS)

    Moora, M.; Davison, J.; Metsis, M.; Öpik, M.; Vasar, M.; Zobel, M.

    2012-04-01

    Arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota) colonize the roots of most terrestrial plants, facilitating mineral nutrient uptake from soil in exchange for plant-assimilated carbon. While investigating functional aspects of plant-AM fungi interactions has been a major focus of research, there is increasing interest in describing and explaining the distribution of AM fungal diversity. Different management practices has been shown to influence the AM fungal communities while more intense management can bring along the loss of AM fungal diversity. Such a loss may have negative consequences on ecosystem service delivery, primary production and soil sustainability. However, due to cryptic lifestyle of AM fungi, relatively few information is available about variability of diversity and composition of AM fungal communities in the soils from differently managed ecosystems. To study the variation of soil AM fungal communities in response to the land use intensity, replicated soil samples were collected along land use gradient from intensively managed agricultural fields, organic fields, forest plantations and managed natural forest to primeval forest in Estonia. Soil AM fungal communities were described using molecular tools: DNA extraction, amplicon isolation and 454 large scale parallel pyrosequencing. Glomeromycota sequences were amplified using the SSU rDNA primers NS31 and AML2. We shall analyse and describe AM fungal community changes along land use intensity gradient and seek finding indicator taxa characteristic to particular land use types. We shall also address changes in the diversity of AM fungal taxa and check whether the decrease of diversity along land use intensity is a ubiquitous phenomenon.

  3. Impact of Land Use on Arbuscular Mycorrhizal Fungal Communities in Rural Canada

    PubMed Central

    Dai, Mulan; Bainard, Luke D.; Gan, Yantai; Lynch, Derek

    2013-01-01

    The influence of land use on soil bio-resources is largely unknown. We examined the communities of arbuscular mycorrhizal (AM) fungi in wheat-growing cropland, natural areas, and seminatural areas along roads. We sampled the Canadian prairie extensively (317 sites) and sampled 20 sites in the Atlantic maritime ecozone for comparison. The proportions of the different AM fungal taxa in the communities found at these sites varied with land use type and ecozones, based on pyrosequencing of 18S rRNA gene (rDNA) amplicons, but the lists of AM fungal taxa obtained from the different land use types and ecozones were very similar. In the prairie, the Glomeraceae family was the most abundant and diverse family of Glomeromycota, followed by the Claroideoglomeraceae, but in the Atlantic maritime ecozone, the Claroideoglomeraceae family was most abundant. In the prairie, species richness and Shannon's diversity index were highest in roadsides, whereas cropland had a higher degree of species richness than roadsides in the Atlantic maritime ecozone. The frequencies of occurrence of the different AM fungal taxa in croplands in the prairie and Atlantic maritime ecozones were highly correlated, but the AM fungal communities in these ecozones had different structures. We conclude that the AM fungal resources of soils are resilient to disturbance and that the richness of AM fungi under cropland management has been maintained, despite evidence of a structural shift imposed by this type of land use. Roadsides in the Canadian prairie are a good repository for the conservation of AM fungal diversity. PMID:23995929

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

    PubMed Central

    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. PMID:27303367

  5. Arbuscular mycorrhizal colonization, plant chemistry, and aboveground herbivory on Senecio jacobaea

    NASA Astrophysics Data System (ADS)

    Reidinger, Stefan; Eschen, René; Gange, Alan C.; Finch, Paul; Bezemer, T. Martijn

    2012-01-01

    Arbuscular mycorrhizal fungi (AMF) can affect insect herbivores by changing plant growth and chemistry. However, many factors can influence the symbiotic relationship between plant and fungus, potentially obscuring experimental treatments and ecosystem impacts. In a field experiment, we assessed AMF colonization levels of individual ragwort ( Senecio jacobaea) plants growing in grassland plots that were originally sown with 15 or 4 plant species, or were unsown. We measured the concentrations of carbon, nitrogen and pyrrolizidine alkaloids (PAs), and assessed the presence of aboveground insect herbivores on the sampled plants. Total AMF colonization and colonization by arbuscules was lower in plots sown with 15 species than in plots sown with 4 species and unsown plots. AMF colonization was positively related to the cover of oxeye daisy ( Leucanthemum vulgare) and a positive relationship between colonization by arbuscules and the occurrence of a specialist seed-feeding fly ( Pegohylemyia seneciella) was found. The occurrence of stem-boring, leaf-mining and sap-sucking insects was not affected by AMF colonization. Total PA concentrations were negatively related to colonization levels by vesicles, but did not differ among the sowing treatments. No single factor explained the observed differences in AMF colonization among the sowing treatments or insect herbivore occurrence on S. jacobaea. However, correlations across the treatments suggest that some of the variation was due to the abundance of one plant species, which is known to stimulate AMF colonization of neighbouring plants, while AMF colonization was related to the occurrence of a specialist insect herbivore. Our results thus illustrate that in natural systems, the ecosystem impact of AMF through their influence on the occurrence of specialist insects can be recognised, but they also highlight the confounding effect of neighbouring plant species identity. Hence, our results emphasise the importance of field

  6. Prunus persica Crop Management Differentially Promotes Arbuscular Mycorrhizal Fungi Diversity in a Tropical Agro-Ecosystem

    PubMed Central

    Alguacil, Maria del Mar; Torrecillas, Emma; Lozano, Zenaida; Torres, Maria Pilar; Roldán, Antonio

    2014-01-01

    Due to the important role of arbuscular mycorrhizal fungi (AMF) in ecosystem functioning, determination of the effect of management practices on the AMF diversity in agricultural soils is essential for the sustainability of these agro-ecosystems. The objective of this study was to compare the AMF diversity in Prunus persica roots under two types of fertilisation (inorganic, with or without manure) combined with integrated or chemical pest management in a Venezuelan agro-ecosystem. The AM fungal small-subunit (SSU) rRNA genes were subjected to PCR, cloning, sequencing and phylogenetic analyses. Twenty-one different phylotypes were identified: 15 belonged to the genus Glomus, one to Claroideoglomus, two to Paraglomus, one to Acaulospora, one to Scutellospora and one to Archaeospora. The distribution of the AMF community composition differed as a consequence of the treatment effects. The treatment combining organic and inorganic fertilisation with chemical pest control had the highest AMF richness and the treatment combining inorganic fertilisation with chemical pest had the lowest. The real causes and effects of these differences in the AMF community are very difficult to establish, since the crop management regimes tested were composed of several interacting factors. In conclusion, the crop management practices can exert a significant influence on the populations of AMF. The treatment combining organic and inorganic fertilisation with chemical pest control appears to be the most suitable agricultural management strategy with respect to improving the AMF diversity in this crop under tropical conditions, and thus for maintaining the agricultural and environmental sustainability of this agro-ecosystem. PMID:24520389

  7. The Potential Role of Arbuscular Mycorrhizal Fungi in the Restoration of Degraded Lands

    PubMed Central

    Asmelash, Fisseha; Bekele, Tamrat; Birhane, Emiru

    2016-01-01

    Experiences worldwide reveal that degraded lands restoration projects achieve little success or fail. Hence, understanding the underlying causes and accordingly, devising appropriate restoration mechanisms is crucial. In doing so, the ever-increasing aspiration and global commitments in degraded lands restoration could be realized. Here we explain that arbuscular mycorrhizal fungi (AMF) biotechnology is a potential mechanism to significantly improve the restoration success of degraded lands. There are abundant scientific evidences to demonstrate that AMF significantly improve soil attributes, increase above and belowground biodiversity, significantly improve tree/shrub seedlings survival, growth and establishment on moisture and nutrient stressed soils. AMF have also been shown to drive plant succession and may prevent invasion by alien species. The very few conditions where infective AMF are low in abundance and diversity is when the soil erodes, is disturbed and is devoid of vegetation cover. These are all common features of degraded lands. Meanwhile, degraded lands harbor low levels of infective AMF abundance and diversity. Therefore, the successful restoration of infective AMF can potentially improve the restoration success of degraded lands. Better AMF inoculation effects result when inocula are composed of native fungi instead of exotics, early seral instead of late seral fungi, and are consortia instead of few or single species. Future research efforts should focus on AMF effect on plant community primary productivity and plant competition. Further investigation focusing on forest ecosystems, and carried out at the field condition is highly recommended. Devising cheap and ethically widely accepted inocula production methods and better ways of AMF in situ management for effective restoration of degraded lands will also remain to be important research areas. PMID:27507960

  8. Arbuscular mycorrhizal fungi alleviate oxidative stress induced by ADOR and enhance antioxidant responses of tomato plants.

    PubMed

    García-Sánchez, Mercedes; Palma, José Manuel; Ocampo, Juan Antonio; García-Romera, Inmaculada; Aranda, Elisabet

    2014-03-15

    The behaviour of tomato plants inoculated with arbuscular mycorrhizal (AM) fungi grown in the presence of aqueous extracts from dry olive residue (ADOR) was studied in order to understand how this symbiotic relationship helps plants to cope with oxidative stress caused by ADOR. The influence of AM symbiosis on plant growth and other physiological parameters was also studied. Tomato plants were inoculated with the AM fungus Funneliformis mosseae and were grown in the presence of ADOR bioremediated and non-bioremediated by Coriolopsis floccosa and Penicillium chrysogenum-10. The antioxidant response as well as parameters of oxidative damage were examined in roots and leaves. The data showed a significant increase in the biomass of AM plant growth in the presence of ADOR, regardless of whether it was bioremediated. The establishment and development of the symbiosis were negatively affected after plants were exposed to ADOR. No differences were observed in the relative water content (RWC) or PS II efficiency between non-AM and AM plants. The increase in the enzymatic activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and glutathione-S-transferase (GST; EC 2.5.1.18) were simultaneous to the reduction of MDA levels and H2O2 content in AM root growth in the presence of ADOR. Similar H2O2 levels were observed among non-AM and AM plants, although only AM plants showed reduced lipid peroxidation content, probably due to the involvement of antioxidant enzymes. The results highlight how the application of both bioremediated ADOR and AM fungi can alleviate the oxidative stress conditions, improving the growth and development of tomato plants.

  9. Soil salinity delays germination and limits growth of hyphae from propagules of arbuscular mycorrhizal fungi.

    PubMed

    Juniper, S; Abbott, L K

    2006-07-01

    Colonisation of plant roots by some arbuscular mycorrhizal (AM) fungi is reduced in the presence of sodium chloride (NaCl), probably due to a direct effect of NaCl on the fungi. However, there appear to be differences between the fungi in their ability to colonise plants in the presence of NaCl. This experiment tested the hypothesis that propagules of different isolates and species of AM fungi from saline and nonsaline soils would differ in their ability to germinate and grow in the presence of NaCl in the soil solution. Spores or pieces of root colonised by a range of AM fungi were incubated between filters buried in soil to which NaCl had been added at concentrations of 0, 150 or 300 mM in the soil solution. At regular intervals, filters were removed from the soil and both the percentage of propagules which had germinated and the length of proliferating hyphae were determined. Germination of spores of AM fungi studied was delayed in the presence of NaCl, but the fungi differed in the extent to which germination was inhibited. Two isolates of Scutellospora calospora reached maximum germination in 300 mM NaCl, but neither of two isolates of Acaulospora laevis germinated in the presence of NaCl. Germination of spores of the other fungi, including some isolated from saline soil, fell between these extremes. For some fungi, the specific rate of hyphal extension was reduced by NaCl. For others, the specific rate of growth was similar in the presence of NaCl to that in the control treatment, but overall production of hyphae was reduced in the NaCl treatments because germination was reduced.

  10. Impact of long-term conventional and organic farming on the diversity of arbuscular mycorrhizal fungi.

    PubMed

    Oehl, Fritz; Sieverding, Ewald; Mäder, Paul; Dubois, David; Ineichen, Kurt; Boller, Thomas; Wiemken, Andres

    2004-03-01

    Previous work has shown considerably enhanced soil fertility in agroecosystems managed by organic farming as compared to conventional farming. Arbuscular mycorrhizal fungi (AMF) play a crucial role in nutrient acquisition and soil fertility. The objective of this study was to investigate the diversity of AMF in the context of a long-term study in which replicated field plots, at a single site in Central Europe, had been cultivated for 22 years according to two "organic" and two "conventional" farming systems. In the 23rd year, the field plots, carrying an 18-month-old grass-clover stand, were examined in two ways with respect to AMF diversity. Firstly, AMF spores were isolated and morphologically identified from soil samples. The study revealed that the AMF spore abundance and species diversity was significantly higher in the organic than in the conventional systems. Furthermore, the AMF community differed in the conventional and organic systems: Glomus species were similarly abundant in all systems but spores of Acaulospora and Scutellospora species were more abundant in the organic systems. Secondly, the soils were used to establish AMF-trap cultures using a consortium of Plantago lanceolata, Trifolium pratense and Lolium perenne as host plants. The AMF spore community developing in the trap cultures differed: after 12 months, two species of the Acaulosporaceae (A. paulinae and A. longula) were consistently found to account for a large part of the spore community in the trap cultures from the organic systems but were found rarely in the ones from the conventional systems. The findings show that some AMF species present in natural ecosystems are maintained under organic farming but severely depressed under conventional farming, indicating a potentially severe loss of ecosystem function under conventional farming.

  11. Arctic arbuscular mycorrhizal spore community and viability after storage in cold conditions.

    PubMed

    Varga, Sandra; Finozzi, Chiara; Vestberg, Mauritz; Kytöviita, Minna-Maarit

    2015-07-01

    Arbuscular mycorrhizal fungi (AMF) form probably the most widespread symbiosis on earth and are found across all ecosystems including the Arctic regions. In the Arctic, the prevalent harsh cold conditions experienced by both host plants and fungi may have selected for AMF species with long-surviving spores, the principal means for dispersal and survival. However, basic knowledge about their viability is lacking. AMF spore assembly from two Arctic sites was examined in soil samples collected across an 11-year period and stored at -20 °C for up to 10 years. AMF spore viability and ability to colonize plants were investigated in the greenhouse using Plantago lanceolata. It was predicted that Arctic AMF spores would survive in cold conditions for several years, with an expected decrease in viability over time as suggested by other experiments with temperate material. Results show that even though the two study sites differed in AMF spore density, the relative abundance of spore morphotypes was rather similar across sites and years. Furthermore, spore viability over time was site-dependent as it decreased only in one site. Although spores were viable, only a very small proportion of hosts and roots became colonized in the greenhouse even 21 months after inoculation. Taken together, these results suggest a certain site-dependent variability in AMF spore communities and the ability of Arctic AMF spores to remain viable after a long-term storage in cold conditions. The lack of host colonization in the greenhouse may be related to the inability to overcome spore dormancy under these conditions.

  12. Isolation and phenotypic characterization of Lotus japonicus mutants specifically defective in arbuscular mycorrhizal formation.

    PubMed

    Kojima, Tomoko; Saito, Katsuharu; Oba, Hirosuke; Yoshida, Yuma; Terasawa, Junya; Umehara, Yosuke; Suganuma, Norio; Kawaguchi, Masayoshi; Ohtomo, Ryo

    2014-05-01

    Several symbiotic mutants of legume plants defective in nodulation have also been shown to be mutants related to arbuscular mycorrhizal (AM) symbiosis. The origin of the AM symbiosis can be traced back to the early land plants. It has therefore been postulated that the older system of AM symbiosis was partially incorporated into the newer system of legume-rhizobium symbiosis. To unravel the genetic basis of the establishment of AM symbiosis, we screened about 34,000 plants derived from ethyl methanesulfonate (EMS)-mutagenized Lotus japonicus seeds by microscopic observation. As a result, three lines (ME778, ME966 and ME2329) were isolated as AM-specific mutants that exhibit clear AM-defective phenotypes but form normal effective root nodules with rhizobial infection. In the ME2329 mutant, AM fungi spread their hyphae into the intercellular space of the cortex and formed trunk hyphae in the cortical cells, but the development of fine branches in the arbuscules was arrested. The ME2329 mutant carried a nonsense mutation in the STR-homolog gene, implying that the line may be an str mutant in L. japonicus. On the ME778 and ME966 mutant roots, the entry of AM fungal hyphae was blocked between two adjacent epidermal cells. Occasionally, hyphal colonization accompanied by arbuscules was observed in the two mutants. The genes responsible for the ME778 and ME966 mutants were independently located on chromosome 2. These results suggest that the ME778 and ME966 lines are symbiotic mutants involved in the early stage of AM formation in L. japonicus.

  13. Serpentine and non-serpentine ecotypes of Collinsia sparsiflora associate with distinct arbuscular mycorrhizal fungal assemblages.

    PubMed

    Schechter, S P; Bruns, T D

    2008-07-01

    Although plant adaptation to serpentine soils has been studied for several decades, the mechanisms of plant adaptation to edaphic extremes are still poorly understood. Arbuscular mycorrhizal fungi (AMF) are common root symbionts that can increase the plant hosts' establishment and growth in stressful environments. However, little is known about the role plant-AMF interactions play in plant adaptation to serpentine. As a first step towards understanding this role, we examined the AMF assemblages associated with field populations of serpentine and non-serpentine ecotypes of California native plant Collinsia sparsiflora. We sampled roots of C. sparsiflora from three serpentine and three non-serpentine sites in close proximity (110 m to 1.94 km between sites) and analysed the small subunit ribosomal DNA gene amplified from root DNA extracts using AMF-specific primers. A total of 1952 clones from 24 root samples (four from each site) were sequenced. We used sequence similarity and phylogenetic analysis to determine operational taxonomic units (OTU) resulting in 19 OTUs representing taxa from six AMF genera, including one serpentine-specific OTU. We used Bray-Curtis similarity, multidimensional scaling and analysis of similarity to compare root sample AMF assemblages. These analyses clearly showed that plant ecotypes associated with distinct AMF assemblages; an Acaulospora OTU-dominated serpentine, and a Glomus OTU-dominated non-serpentine assemblages. Species diversity and evenness were significantly higher in serpentine assemblages. Finally, relate analysis showed a relationship between ecotype AMF assemblages and soil nutrients. This study reveals a strong relationship between AMF associates and plant adaptation to edaphic extremes.

  14. Do arbuscular mycorrhizal fungi affect cadmium uptake kinetics, subcellular distribution and chemical forms in rice?

    PubMed

    Li, Hui; Luo, Na; Zhang, Li Jun; Zhao, Hai Ming; Li, Yan Wen; Cai, Quan Ying; Wong, Ming Hung; Mo, Ce Hui

    2016-11-15

    Rice (Oryza sativa L.) plants were inoculated with two species of arbuscular mycorrhizal fungi (AMF) - Rhizophagus intraradices (RI) and Funneliformis mosseae (FM) and grown for 60days to ensure strong colonization. Subsequently, a short-term hydroponic experiment was carried out to investigate the effects of AMF on cadmium (Cd) uptake kinetics, subcellular distribution and chemical forms in rice exposed to six Cd levels (0, 0.005, 0.01, 0.025, 0.05, 0.1mM) for three days. The results showed that the uptake kinetics of Cd fitted the Michaelis-Menten model well (R(2)>0.89). AMF significantly decreased the Cd concentrations both in shoots and roots in Cd solutions. Furthermore, the decrement of Cd concentrations by FM was significantly higher than RI treatment in roots. AMF reduced the Cd concentrations markedly in the cell wall fractions at high Cd substrate (≥0.025mM). The main subcellular fraction contributed to Cd detoxification was cell wall at low Cd substrate (<0.05mM), while vacuoles at high Cd substrate (≥0.05mM). Moreover, the concentrations and proportions of Cd in inorganic and water-soluble form also reduced by AMF colonization at high Cd substrate (≥0.05mM), both in shoots and roots. This suggested that AMF could convert Cd into inactive forms which were less toxic. Therefore, AMF could enhance rice resistance to Cd through altering subcellular distribution and chemical forms of Cd in rice.

  15. The role of arbuscular mycorrhizal fungi in grain production and nutrition of sorghum genotypes: Enhancing sustainability through plant-microbial partnership

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The role of arbuscular mycorrhizal (AM) fungi and fertilization in sorghum grain production and quality was assessed for 3 hybrid genotypes, 2 open-pollinated African genotypes, and 1 open-pollinated Latin American genotype. The open-pollinated genotypes produced an average of 206% more vegetative b...

  16. Frequent cultivation prior to planting to prevent weed competition results in an opportunity for the use of arbuscular mycorrhizal fungus inoculum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Inoculation with arbuscular mycorrhizal [AM] fungi is a potentially useful tool in agricultural systems with limited options regarding use of synthetic chemicals for fertility and pest control. We tested the response of Allium porrum cv. Lancelot to inoculation with AM fungi in a field high in avai...

  17. Influence of host plants and soil diluents on arbuscular mycorrhizal fungus propagation for on-farm inoculum production using leaf litter compost and agrowastes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arbuscular mycorrhizal (AM) fungi (Claroideoglomus etunicatum NNT10, C. etunicatum PBT03 and Funneliformis mosseae RYA08) were propagated using different culture materials (sterile sandy soil by itself or mixed 1:1 (v/v) with clay-brick granules, rice husk charcoal, or vermiculite) and host plants (...

  18. On-farm production of arbuscular mycorrhizal funus inoculum in compost and vermiculite mixtures: results of on-farm demonstrations and impact of compost microbiological quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The sustainability and profitability of many agricultural systems can be enhanced through the utilization of inoculum of arbuscular mycorrhizal fungi. Inocula are commercially available, but inoculum can also be produced on-farm in mixtures of compost and vermiculite with a nurse host plant. Demon...

  19. Reactive Oxygen Species Generation-Scavenging and Signaling during Plant-Arbuscular Mycorrhizal and Piriformospora indica Interaction under Stress Condition

    PubMed Central

    Nath, Manoj; Bhatt, Deepesh; Prasad, Ram; Gill, Sarvajeet S.; Anjum, Naser A.; Tuteja, Narendra

    2016-01-01

    A defined balance between the generation and scavenging of reactive oxygen species (ROS) is essential to utilize ROS as an adaptive defense response of plants under biotic and abiotic stress conditions. Moreover, ROS are not only a major determinant of stress response but also act as signaling molecule that regulates various cellular processes including plant-microbe interaction. In particular, rhizosphere constitutes the biologically dynamic zone for plant–microbe interactions which forms a mutual link leading to reciprocal signaling in both the partners. Among plant–microbe interactions, symbiotic associations of arbuscular mycorrhizal fungi (AMF) and arbuscular mycorrhizal-like fungus especially Piriformospora indica with plants are well known to improve plant growth by alleviating the stress-impacts and consequently enhance the plant fitness. AMF and P. indica colonization mainly enhances ROS-metabolism, maintains ROS-homeostasis, and thereby averts higher ROS-level accrued inhibition in plant cellular processes and plant growth and survival under stressful environments. This article summarizes the major outcomes of the recent reports on the ROS-generation, scavenging and signaling in biotic-abiotic stressed plants with AMF and P. indica colonization. Overall, a detailed exploration of ROS-signature kinetics during plant-AMF/P. indica interaction can help in designing innovative strategies for improving plant health and productivity under stress conditions. PMID:27818671

  20. Arbuscular mycorrhizal fungi diversity influenced by different agricultural management practices in a semi-arid Mediterranean agro-ecosystem

    NASA Astrophysics Data System (ADS)

    de Mar Alguacil, Maria; Torrecillas, Emma; Garcia-Orenes, Fuensanta; Torres, Maria Pilar; Roldan, Antonio

    2013-04-01

    The arbuscular mycorrhizal fungi (AMF) are a key, integral component of the stability, sustainability and functioning of ecosystems. In this study a field experiment was performed at the El Teularet-Sierra de Enguera Experimental Station (eastern Spain) to assess the influence during a 6-yr period of different agricultural practices on the diversity of arbuscular mycorrhizal fungi (AMF). The management practices included residual herbicide use, ploughing, ploughing + oats, addition of oat straw mulch and a control (land abandonment). Adjacent soil under natural vegetation was used as a reference for local, high-quality soil and as a control for comparison with the agricultural soils under different management practices. The AM fungal small-subunit (SSU) rRNA genes were subjected to PCR, cloning, sequencing and phylogenetic analyses. Thirty-six different phylotypes were identified, which were grouped in four families: Glomeraceae, Paraglomeraceae, Ambisporaceae and Claroideoglomeraceae. The first results showed significant differences in the distribution of the AMF phylotypes as consequence of the difference between agricultural management practices. Thus, the lowest diversity was observed for the plot that was treated with herbicide. The management practices including ploughing and ploughing + oats had similar AMF diversity. Oat straw mulching yielded the highest number of different AMF sequence types and showed the highest diversity index. Thus, this treatment could be more suitable in sustainable soil use and therefore protection of biodiversity.

  1. Arbuscular mycorrhizal fungi associations of vascular plants confined to river valleys: towards understanding the river corridor plant distribution.

    PubMed

    Nobis, Agnieszka; Błaszkowski, Janusz; Zubek, Szymon

    2015-01-01

    The group of river corridor plants (RCP) includes vascular plant species which grow mainly or exclusively in the valleys of large rivers. Despite the long recognized fact that some plant species display a corridor-like distribution pattern in Central Europe, there is still no exhaustive explanation of the mechanisms generating this peculiar distribution. The main goal of this study was therefore to investigate whether arbuscular mycorrhizal fungi (AMF) and fungal root endophytes influence the RCP distribution. Arbuscular mycorrhizae (AM) were observed in 19 out of 33 studied RCP. Dark septate endophytes (DSE) and Olpidium spp. were recorded with low abundance in 15 and 10 plant species, respectively. The spores of AMF were found only in 32% of trap cultures established from the soils collected in the river corridor habitats. In total, six widespread AMF species were identified. Because the percentage of non-mycorrhizal species in the group of RCP is significant and the sites in river corridors are characterized by low AMF species diversity, RCP can be outcompeted outside river valleys by the widespread species that are able to benefit from AM associations in more stable plant-AMF communities in non-river habitats.

  2. The best for the guest: high Andean nurse cushions of Azorella madreporica enhance arbuscular mycorrhizal status in associated plant species.

    PubMed

    Casanova-Katny, M Angélica; Torres-Mellado, Gustavo Adolfo; Palfner, Goetz; Cavieres, Lohengrin A

    2011-10-01

    Positive interactions between cushion plant and associated plants species in the high Andes of central Chile should also include the effects of fungal root symbionts. We hypothesized that higher colonization by arbuscular mycorrhizal (AM) fungi exists in cushion-associated (nursling) plants compared with conspecific individuals growing on bare ground. We assessed the AM status of Andean plants at two sites at different altitudes (3,200 and 3,600 ma.s.l.) in 23 species, particularly in cushions of Azorella madreporica and five associated plants; additionally, AM fungal spores were retrieved from soil outside and beneath cushions. 18 of the 23 examined plant species presented diagnostic structures of arbuscular mycorrhiza; most of them were also colonized by dark-septate endophytes. Mycorrhization of A. madreporica cushions showed differences between both sites (68% and 32%, respectively). In the native species Hordeum comosum, Nastanthus agglomeratus, and Phacelia secunda associated to A. madreporica, mycorrhization was six times higher than in the same species growing dispersed on bare ground at 3,600 ma.s.l., but mycorrhiza development was less cushion dependent in the alien plants Cerastium arvense and Taraxacum officinale at both sites. The ratio of AM fungal spores beneath versus outside cushions was also 6:1. The common and abundant presence of AM in cushion communities at high altitudes emphasizes the importance of the fungal root symbionts in such situations where plant species benefit from the microclimatic conditions generated by the cushion and also from well-developed mycorrhizal networks.

  3. Arbuscular mycorrhizal symbiosis elicits shoot proteome changes that are modified during cadmium stress alleviation in Medicago truncatula

    PubMed Central

    2011-01-01

    Background Arbuscular mycorrhizal (AM) fungi, which engage a mutualistic symbiosis with the roots of most plant species, have received much attention for their ability to alleviate heavy metal stress in plants, including cadmium (Cd). While the molecular bases of Cd tolerance displayed by mycorrhizal plants have been extensively analysed in roots, very little is known regarding the mechanisms by which legume aboveground organs can escape metal toxicity upon AM symbiosis. As a model system to address this question, we used Glomus irregulare-colonised Medicago truncatula plants, which were previously shown to accumulate and tolerate heavy metal in their shoots when grown in a substrate spiked with 2 mg Cd kg-1. Results The measurement of three indicators for metal phytoextraction showed that shoots of mycorrhizal M. truncatula plants have a capacity for extracting Cd that is not related to an increase in root-to-shoot translocation rate, but to a high level of allocation plasticity. When analysing the photosynthetic performance in metal-treated mycorrhizal plants relative to those only Cd-supplied, it turned out that the presence of G. irregulare partially alleviated the negative effects of Cd on photosynthesis. To test the mechanisms by which shoots of Cd-treated mycorrhizal plants avoid metal toxicity, we performed a 2-DE/MALDI/TOF-based comparative proteomic analysis of the M. truncatula shoot responses upon mycorrhization and Cd exposure. Whereas the metal-responsive shoot proteins currently identified in non-mycorrhizal M. truncatula indicated that Cd impaired CO2 assimilation, the mycorrhiza-responsive shoot proteome was characterised by an increase in photosynthesis-related proteins coupled to a reduction in glugoneogenesis/glycolysis and antioxidant processes. By contrast, Cd was found to trigger the opposite response coupled the up-accumulation of molecular chaperones in shoot of mycorrhizal plants relative to those metal-free. Conclusion Besides drawing a

  4. Beneficial contribution of the arbuscular mycorrhizal fungus, Rhizophagus irregularis, in the protection of Medicago truncatula roots against benzo[a]pyrene toxicity.

    PubMed

    Lenoir, Ingrid; Fontaine, Joël; Tisserant, Benoît; Laruelle, Frédéric; Lounès-Hadj Sahraoui, Anissa

    2017-02-15

    Arbuscular mycorrhizal fungi are able to improve plant establishment in polluted soils but little is known about the genes involved in the plant protection against pollutant toxicity by mycorrhization, in particular in the presence of polycyclic aromatic hydrocarbons (PAH). The present work aims at studying in both symbiotic partners, Medicago truncatula and Rhizophagus irregularis: (i) expression of genes putatively involved in PAH tolerance (MtSOD, MtPOX, MtAPX, MtGST, MtTFIIS, and MtTdp1α), (ii) activities of antioxidant (SOD, POX) and detoxification (GST) enzymes, and (iii) H2O2 and the heavy PAH, benzo[a]pyrene (B[a]P) accumulation. In the presence of B[a]P, whereas induction of the enzymatic activities was detected in R. irregularis and non-mycorrhizal roots as well as upregulation of the gene expressions in the non-mycorrhizal roots, downregulation of the gene expressions and decrease of enzyme activities were observed in mycorrhizal roots. Moreover, B[a]P increased H2O2 production in non-mycorrhizal roots and in R. irregularis but not in mycorrhizal roots. In addition, a lower B[a]P bioaccumulation in mycorrhizal roots was measured in comparison with non-mycorrhizal roots. Being less affected by pollutant toxicity, mycorrhizal roots did not activate any defense mechanism either at the gene expression regulation level or at the enzymatic level.

  5. 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.

  6. The impact of arbuscular mycorrhizal fungi in mitigating salt-induced adverse effects in sweet basil (Ocimum basilicum L.).

    PubMed

    Elhindi, Khalid M; El-Din, Ahmed Sharaf; Elgorban, Abdallah M

    2017-01-01

    Salinity is one of the serious abiotic stresses adversely affecting the majority of arable lands worldwide, limiting the crop productivity of most of the economically important crops. Sweet basil (Osmium basilicum) plants were grown in a non-saline soil (EC = 0.64 dS m(-1)), in low saline soil (EC = 5 dS m(-1)), and in a high saline soil (EC = 10 dS m(-1)). There were differences between arbuscular mycorrhizal (Glomus deserticola) colonized plants (+AMF) and non-colonized plants (-AMF). Mycorrhiza mitigated the reduction of K, P and Ca uptake due to salinity. The balance between K/Na and between Ca/Na was improved in +AMF plants. Growth enhancement by mycorrhiza was independent from plant phosphorus content under high salinity levels. Different growth parameters, salt stress tolerance and accumulation of proline content were investigated, these results showed that the use of mycorrhizal inoculum (AMF) was able to enhance the productivity of sweet basil plants under salinity conditions. Mycorrhizal inoculation significantly increased chlorophyll content and water use efficiency under salinity stress. The sweet basil plants appeared to have high dependency on AMF which improved plant growth, photosynthetic efficiency, gas exchange and water use efficiency under salinity stress. In this study, there was evidence that colonization with AMF can alleviate the detrimental salinity stress influence on the growth and productivity of sweet basil plants.

  7. 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

  8. 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.

  9. Detection of a plant enzyme exhibiting chlorogenate-dependant caffeoyltransferase activity in methanolic extracts of arbuscular mycorrhizal tomato roots.

    PubMed

    Negrel, Jonathan; Javelle, Francine; Morandi, Dominique

    2013-05-01

    When Glomus intraradices-colonised tomato roots were extracted in methanol at 6 °C, chlorogenic acid (5-caffeoylquinic acid), naturally present in the extract, was slowly converted by transesterification into methyl caffeate. The progress of the reaction could be monitored by HPLC. The reaction only occurred when the ground roots were left in contact with the hydro-alcoholic extract and required the presence of 15-35% water in the mixture. When the roots were extracted in ethanol, chlorogenic acid was transformed to ethyl caffeate in the same conditions. The reaction was also detected in Glomus mosseae-colonised tomato root extracts. It was also detectable in non-mycorrhizal root extracts but was 10-25 times slower. By contrast it was undetectable in extracts of the aerial parts of tomato plants, which also contain high amounts of chlorogenic acid, whether or not these plants were inoculated by the arbuscular mycorrhizal fungus. We found that this transesterification reaction is catalysed by a tomato enzyme, which remains active in hydro-alcoholic mixtures and exhibits chlorogenate-dependant caffeoyltransferase activity in the presence of methanol or ethanol. This transferase activity is inhibited by phenylmethanesulfonyl fluoride. The 4- and 3-caffeoylquinic acid isomers were also used as substrates but were less active than chlorogenic acid. Highest activity was detected in mycorrhizal roots of nutrient-deprived tomato plants. Surprisingly this caffeoyltransferase activity could also be detected in hydro-alcoholic extracts of G. intraradices-colonised roots of leek, sorghum or barrel medic.

  10. Effect of arbuscular mycorrhizal fungal inoculation on heavy metal accumulation of maize grown in a naturally contaminated soil.

    PubMed

    Wang, Fa Yuan; Lin, Xian Gui; Yin, Rui

    2007-01-01

    A pot culture experiment was carried out to study heavy metal (HM) phytoaccumulation from soil contaminated with Cu, Zn, Pb, and Cd by maize (Zea mays L.) inoculated with arbuscular mycorrhizal (AM) fungi (AMF). Two AM fungal inocula--MI containing only one AM fungal strain (Glomus caledonium 90036) and MII consisting of Gigaspora margarita ZJ37, Gigaspora decipens ZJ38, Scutellospora gilmori ZJ39, Acaulospora spp., and Glomus spp.--were applied to the soil under unsterilized conditions. The control received no mycorrhizal inoculation. The maize plants were harvested after 10 wk of growth. MI-treated plants had higher mycorrhizal colonization than MII-treated plants. Both MI and MII increased P concentrations in roots, but not in shoots. Neither MI nor MII had significant effects on shoot or root dry weight (DW). Compared with the control, shoot Cu, Zn, Pb, and Cd concentrations were decreased by MI but increased by MII. Cu, Zn, Pb, and Cd uptake into shoots and roots all increased in MII-treated plants, while in MI-treated plants Cu, Zn, and Pb uptake into shoots and Cd uptake into roots decreased but Cu, Zn, and Pb uptake into roots and Cd into shoots increased. MII was more effective than MI in promoting HM extraction efficiencies. The results indicate that MII can benefit HMphytoextraction and, therefore, show potential in the phytoremediation of HM-contaminated soils.

  11. High compatibility between arbuscular mycorrhizal fungal communities and seedlings of different land use types in a tropical dry ecosystem.

    PubMed

    Gavito, Mayra E; Pérez-Castillo, Daniel; González-Monterrubio, César F; Vieyra-Hernández, Teresa; Martínez-Trujillo, Miguel

    2008-12-01

    We conducted this study to explore limitations for the establishment of mycorrhizal associations in disturbed areas of the tropical dry ecosystem in the Chamela region of Jalisco, Mexico. Specifically, we: (1) assessed the diversity and composition of arbuscular mycorrhizal fungal (AMF) communities through spore morphospecies identification in three common land uses (primary forest, secondary forest, and pasture), (2) tested the inoculum potential of the AMF communities and the effect of water stress on the establishment of mycorrhizal associations in seedlings of various plant species, and (3) explored the importance of AMF community composition on early seedling development. Soil and root samples were taken from 15 random points in each of three plots established in two primary forests, two 26-year-old secondary forests, and two 26-year-old pastures. We expected that because of soil degradation and management, pastures would have the lowest and primary forests the highest AMF species richness. We found evidence for changes in AMF species composition due to land use and for higher morphospecies richness in primary forests than in secondary forests and pastures. We expected also that water stress limited plant and mycorrhizal development and that plants and AMF communities from secondary forests and pastures would be less affected by (better adapted to) water stress than those from the primary forest. We found that although all plant species showed biomass reductions under water stress, only some of the plant species had lower mycorrhizal development under water stress, and this was regardless of the AMF community inoculated. The third hypothesis was that plant species common to all land use types would respond similarly to all AMF communities, whereas plant species found mainly in one land use type would grow better when inoculated with the AMF community of that specific land use type. All plant species were however equally responsive to the three AMF communities

  12. Phosphorus acquisition efficiency in arbuscular mycorrhizal maize is correlated with the abundance of root-external hyphae and the accumulation of transcripts encoding PHT1 phosphate transporters.

    PubMed

    Sawers, Ruairidh J H; Svane, Simon F; Quan, Clement; Grønlund, Mette; Wozniak, Barbara; Gebreselassie, Mesfin-Nigussie; González-Muñoz, Eliécer; Chávez Montes, Ricardo A; Baxter, Ivan; Goudet, Jerome; Jakobsen, Iver; Paszkowski, Uta

    2017-04-01

    Plant interactions with arbuscular mycorrhizal fungi have long attracted interest for their potential to promote more efficient use of mineral resources in agriculture. Their use, however, remains limited by a lack of understanding of the processes that determine the outcome of the symbiosis. In this study, the impact of host genotype on growth response to mycorrhizal inoculation was investigated in a panel of diverse maize lines. A panel of 30 maize lines was evaluated with and without inoculation with arbuscular mycorrhizal fungi. The line Oh43 was identified to show superior response and, along with five other reference lines, was characterized in greater detail in a split-compartment system, using (33) P to quantify mycorrhizal phosphorus uptake. Changes in relative growth indicated variation in host capacity to profit from the symbiosis. Shoot phosphate content, abundance of root-internal and -external fungal structures, mycorrhizal phosphorus uptake, and accumulation of transcripts encoding plant PHT1 family phosphate transporters varied among lines. Superior response in Oh43 is correlated with extensive development of root-external hyphae, accumulation of specific Pht1 transcripts and high phosphorus uptake by mycorrhizal plants. The data indicate that host genetic factors influence fungal growth strategy with an impact on plant performance.

  13. [Effects of Arbuscular Mycorrhizal Fungi on the Growth of Reeds in Wetland Soils with Different Salt Content].

    PubMed

    Guo, Jiang-yuan; Guo, Wei; Bi, Na; Fu, Rui-ying; Zhao, Wen-jing; Zhao, Ren-xin; Wang, Li-xin

    2015-04-01

    A greenhouse pot experiment was conducted to investigate the effects of arbuscular mycorrhizal (AM) fungi Claroideoglomus etunicatum (CE), Rhizophagus intraradices (RI), Funneliformis mosseae (FM) and Glomus versiforme (GV) on AM colonization rate, biomass, mineral nutrient uptake, C: N: P ratios and Na and Cl- concentrations of reeds (Phragmites australis) grown in saline and non-saline wetland soils. The aim was to provide a technical basis for the ecological revegetation and salinity restoration of wetland ecosystem. The results indicated that symbiotic associations were successfully established between the four isolates and reeds grown in the two types of wetland soils. The average AM colonization rates ranged from 2.5% to 38%. The mean root colonization rate of CE was significantly higher than those of the other three isolates. There were no significant differences in root colonization rates between saline and non-saline wetland soils. The biomass and nutrient contents of reeds grown in non-saline wetland soils were significantly higher than those grown in saline wetland soils. However, Na+ and Cl- concentrations of reeds grown in non-saline wetland soils were significantly lower than those grown in saline wetland soils. In non-saline wetland soils, inoculation with GV significantly increased the shoot dry weight and the shoot N, P, K, Ca and Mg contents of reeds. Inoculation with GV and RI significantly improved the root P and K contents of reeds. Inoculation with the four AM fungi significantly reduced the shoot N: P ratios. Inoculation with FM and GV significantly reduced the root C : N and C : P ratios. Inoculation with the four AM fungi significantly reduced the shoot Cl- concentrations. Inoculation with RI significantly reduced the shoot Na+ concentrations. In saline wetland soils, inoculation with AM fungi had no significant effect on the biomass, mineral nutrient uptake and Na+ and Cl- concentrations of reeds. The results demonstrated that the four AM

  14. Evolutionary ecology of mycorrhizal functional diversity in agricultural systems

    PubMed Central

    Verbruggen, Erik; Toby Kiers, E

    2010-01-01

    The root systems of most agronomic crops are colonized by diverse assemblages of arbuscular mycorrhizal fungi (AMF), varying in the functional benefits (e.g. nutrient transfer, pathogen protection, water uptake) provided to hosts. Little is known about the evolutionary processes that shape the composition of these fungal assemblages, nor is it known whether more diverse assemblages are beneficial to crop productivity. In this review we aim to identify the evolutionary selection pressures that shape AMF diversity in agricultural systems and explore whether promotion of AMF diversity can convincingly be linked to increases in agricultural productivity and/or sustainability. We then ask whether farmers can (and should) actively modify evolutionary selection pressures to increase AMF functioning. We focus on three agriculturally imposed selection regimes: tillage, fertilization, and continuous monoculture. We find that the uniform nature of these practices strongly selects for dominance of few AMF species. These species exhibit predictable, generally non-beneficial traits, namely heavy investment in reproduction at the expense of nutrient scavenging and transfer processes that are beneficial for hosts. A number of focus-points are given based on empirical and theoretical evidence that could be utilized to slow down negative selection pressures on AMF functioning, therein increasing crop benefit. PMID:25567946

  15. Selecting Native Arbuscular Mycorrhizal Fungi to Promote Cassava Growth and Increase Yield under Field Conditions

    PubMed Central

    Séry, D. Jean-Marc; Kouadjo, Z. G. Claude; Voko, B. R. Rodrigue; Zézé, Adolphe

    2016-01-01

    The use of arbuscular mycorrhizal fungal (AMF) inoculation in sustainable agriculture is now widespread worldwide. Although the use of inoculants consisting of native AMF is highly recommended as an alternative to commercial ones, there is no strategy to allow the selection of efficient fungal species from natural communities. The objective of this study was (i) to select efficient native AMF species (ii) evaluate their impact on nematode and water stresses, and (iii) evaluate their impact on cassava yield, an important food security crop in tropical and subtropical regions. Firstly, native AMF communities associated with cassava rhizospheres in fields were collected from different areas and 7 AMF species were selected, based upon their ubiquity and abundance. Using these criteria, two morphotypes (LBVM01 and LBVM02) out of the seven AMF species selected were persistently dominant when cassava was used as a trap plant. LBVM01 and LBVM02 were identified as Acaulospora colombiana (most abundant) and Ambispora appendicula, respectively, after phylogenetic analyses of LSU-ITS-SSU PCR amplified products. Secondly, the potential of these two native AMF species to promote growth and enhance tolerance to root-knot nematode and water stresses of cassava (Yavo variety) was evaluated using single and dual inoculation in greenhouse conditions. Of the two AMF species, it was shown that A. colombiana significantly improved the growth of the cassava and enhanced tolerance to water stress. However, both A. colombiana and A. appendicula conferred bioprotective effects to cassava plants against the nematode Meloidogyne spp., ranging from resistance (suppression or reduction of the nematode reproduction) or tolerance (low or no suppression in cassava growth). Thirdly, the potential of these selected native AMF to improve cassava growth and yield was evaluated under field conditions, compared to a commercial inoculant. In these conditions, the A. colombiana single inoculation and the

  16. Arbuscular Mycorrhizal Fungi as Natural Biofertilizers: Let's Benefit from Past Successes

    PubMed Central

    Berruti, Andrea; Lumini, Erica; Balestrini, Raffaella; Bianciotto, Valeria

    2016-01-01

    Arbuscular Mycorrhizal Fungi (AMF) constitute a group of root obligate biotrophs that exchange mutual benefits with about 80% of plants. They are considered natural biofertilizers, since they provide the host with water, nutrients, and pathogen protection, in exchange for photosynthetic products. Thus, AMF are primary biotic soil components which, when missing or impoverished, can lead to a less efficient ecosystem functioning. The process of re-establishing the natural level of AMF richness can represent a valid alternative to conventional fertilization practices, with a view to sustainable agriculture. The main strategy that can be adopted to achieve this goal is the direct re-introduction of AMF propagules (inoculum) into a target soil. Originally, AMF were described to generally lack host- and niche-specificity, and therefore suggested as agriculturally suitable for a wide range of plants and environmental conditions. Unfortunately, the assumptions that have been made and the results that have been obtained so far are often worlds apart. The problem is that success is unpredictable since different plant species vary their response to the same AMF species mix. Many factors can affect the success of inoculation and AMF persistence in soil, including species compatibility with the target environment, the degree of spatial competition with other soil organisms in the target niche and the timing of inoculation. Thus, it is preferable to take these factors into account when “tuning” an inoculum to a target environment in order to avoid failure of the inoculation process. Genomics and transcriptomics have led to a giant step forward in the research field of AMF, with consequent major advances in the current knowledge on the processes involved in their interaction with the host-plant and other soil organisms. The history of AMF applications in controlled and open-field conditions is now long. A review of biofertilization experiments, based on the use of AMF, has

  17. A molecular approach to study the arbuscular mycorrhizal fungi community in a typical Piedmont grapevine cultivar

    NASA Astrophysics Data System (ADS)

    Magurno, F.; Bughi Peruglia, G.; Lumini, E.; Bianciotto, V.; Balestrini, R.

    2009-04-01

    Viticulture and wine production represent one of the most relevant agro-food sectors for the Piedmont Region (Italy) in terms of value, with more than 400 millions € a year (12 % of total agricultural production of the Region and the 10 % of the national grape and wine production). The soil where grapevines (Vitis spp.) grow is one of the first parameters influencing the complex grapevine-wine chain. Arbuscular mycorrhizal fungi (AMFs), a main component of soil microbiota in most agrosystems, are considered crucial biomarkers of soil quality because of their biofertilisers role. As mutualistic symbionts, they colonize the roots of the majority of plants. Benefits in symbiosis are well showed as an improvement in shoot/root growth, mineral transport, water-stress tolerance and resistance to certain diseases. Grapevines roots are often heavily colonized by AMFs under field conditions and in some cases AMFs appear to be necessary for their normal growth and survival. Even so, little information are until now available about composition of AMFs communities living in the vineyards soil and in associations with grapevine roots, mainly related to morphological characterization. Vineyard of Nebbiolo, one of the most important Piedmont cultivar, was selected in order to study the AMFs community using a molecular approach. Soil samples and roots from an experimental vineyard located in Lessona (Biella, Piedmont, Italy) were analyzed using AM fungal-specific primers to partially amplify the small subunit (SSU) of the ribosomal DNA genes. Much more than 650 clones were sequenced. Phylogenetic analyses identified 32 OTUs from soil, clustered into Glomus groups Aa, Ab, Ad and B, Diversisporaceae and Gigasporaceae families. Thirteen OTUs from roots were determined, clustered into Glomus groups Ab, Ad and B, and Gigasporaceae family. In particular, Glomus group Ad was the best represented in both compartments, suggesting a correlation between intra and extra radical communities

  18. Influence of Vesicular-Arbuscular Mycorrhizal Fungi on the Response of Potato to Phosphorus Deficiency.

    PubMed Central

    McArthur, DAJ.; Knowles, N. R.

    1993-01-01

    Morphological and biochemical interactions between a vesicular-arbuscular mycorrhizal (VAM) fungus (Glomus fasciculatum [Thaxt. sensu Gerdemann] Gerdemann and Trappe) and potato (Solanum tuberosum L.) plants during the development of P deficiency were characterized. Nonmycorrhizal (NM) plants grown for 63 d with low abiotic P supply (0.5 mM) produced 34, 52, and 73% less root, shoot, and tuber dry matter, respectively, than plants grown with high P (2.5 mM). The total leaf area and the leaf area:plant dry weight ratio of low-P plants were substantially lower than those of high-P plants. Moreover, a lower shoot:root dry weight ratio and tuber:plant dry weight ratio in low-P plants than in high-P plants characterized a major effect of P deficiency stress on dry matter partitioning. In addition to a slower rate of growth, low-P plants accumulated nonreducing sugars and nitrate. Furthermore, root respiration and leaf nitrate reductase activity were lower in low-P plants than in high-P plants. Low abiotic P supply also induced physiological changes that contributed to the greater efficiency of P acquisition by low-P plants than by high-P plants. For example, allocation of dry matter and P to root growth was less restricted by P deficiency stress than to shoot and tuber growth. Also, the specific activities of root acid phosphatases and vanadate-sensitive microsomal ATPases were enhanced in P-deficient plants. The establishment of a VAM symbiosis by low-P plants was essential for efficient P acquisition, and a greater root infection level for P-stressed plants indicated increased compatibility to the VAM fungus. By 63 d after planting, low-P VAM plants had recovered 42% more of the available soil P than low-P NM plants. However, the VAM fungus only partially alleviated P deficiency stress and did not completely compensate for inadequate abiotic P supply. Although the specific activities of acid phosphatases and microsomal ATPases were only marginally influenced by VAM

  19. [Mechanism of tomato plants enhanced disease resistance against early blight primed by arbuscular mycorrhizal fungus Glomus versiforme].

    PubMed

    Song, Yuan-yuan; Wang, Rui-long; Wei, Xiao-chen; Lu, Yong-jian; Tang, Zhao-yang; Wu, Guo-zhao; Su, Yi-juan; Zeng, Ren-sen

    2011-09-01

    Arbuscular mycorrhiza (AM) can not only improve host plants nutrient absorption, but also enhance their disease resistance. Taking the tomato (Lycopersicon esculentum) seedlings preinoculated with axbuscular mycorrhizal fungus (AMF) Glomus versiforme as test materials, this paper studied their protective enzyme activities and defense-related genes expression, and their resistance against a fungal pathogen Alternaria solani Sorauer which causes early blight. The seedlings pre-inoculated with AMF and later inoculated with A. solani showed significantly higher activities of superoxide dismutase (SOD) and peroxidase (POD) in leaves. The leaf SOD activity of the dually inoculated plants reached the maximum 18 h after pathogen inoculation, being 28.6%, 79.2% and 82.8% higher than that of the plants with G. versiforme inoculation alone, pathogen inoculation alone, and non-inoculation, and the Leaf POD activity reached the maximum 65 h after pathogen inoculation, being 762%, 18.3%, and 1710% higher, respectively. Real time RT-PCR analysis showed that dual inoculation with C. versiforme and A. solani strongly induced the expression of three defense-related genes. The transcript levels of pathogen-related protein (PR1), basic type beta-1,3-glucanase (PR-2), and chitinase (PR-3) in leaves were 9.67-, 8.54-, and 13.4-fold higher, as compared with the non-inoculation control, respectively. Bioassay showed that the disease incidence and disease index of the seedlings pre-inoculated with C. versiforme were reduced by 36.3% and 61.4%, respectively, as compared with the non-mycorrhizal control plants. These findings indicated that mycorrhizal colonization could induce stronger and quicker defense responses of host tomato plants, and priming could be an important mechanism of the enhanced disease resistance of mycorrhizal tomato plants.

  20. Ecto- and arbuscular mycorrhizal symbiosis can induce tolerance to toxic pulses of phosphorus in jarrah (Eucalyptus marginata) seedlings.

    PubMed

    Kariman, Khalil; Barker, Susan J; Finnegan, Patrick M; Tibbett, Mark

    2014-10-01

    In common with many plants native to low P soils, jarrah (Eucalyptus marginata) develops toxicity symptoms upon exposure to elevated phosphorus (P). Jarrah plants can establish arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) associations, along with a non-colonizing symbiosis described recently. AM colonization is known to influence the pattern of expression of genes required for P uptake of host plants and our aim was to investigate this phenomenon in relation to P sensitivity. Therefore, we examined the effect on hosts of the presence of AM and ECM fungi in combination with toxic pulses of P and assessed possible correlations between the induced tolerance and the shoot P concentration. The P transport dynamics of AM (Rhizophagus irregularis and Scutellospora calospora), ECM (Scleroderma sp.), non-colonizing symbiosis (Austroboletus occidentalis), dual mycorrhizal (R. irregularis and Scleroderma sp.), and non-mycorrhizal (NM) seedlings were monitored following two pulses of P. The ECM and A. occidentalis associations significantly enhanced the shoot P content of jarrah plants growing under P-deficient conditions. In addition, S. calospora, A. occidentalis, and Scleroderma sp. all stimulated plant growth significantly. All inoculated plants had significantly lower phytotoxicity symptoms compared to NM controls 7 days after addition of an elevated P dose (30 mg P kg(-1) soil). Following exposure to toxicity-inducing levels of P, the shoot P concentration was significantly lower in R. irregularis-inoculated and dually inoculated plants compared to NM controls. Although all inoculated plants had reduced toxicity symptoms and there was a positive linear relationship between rank and shoot P concentration, the protective effect was not necessarily explained by the type of fungal association or the extent of mycorrhizal colonization.

  1. Influence of phosphorus application and arbuscular mycorrhizal inoculation on growth, foliar nitrogen mobilization, and phosphorus partitioning in cowpea plants.

    PubMed

    Taffouo, Victor Désiré; Ngwene, Benard; Akoa, Amougou; Franken, Philipp

    2014-07-01

    The present study was undertaken to evaluate the effects of phosphorus (P) application and arbuscular mycorrhizal (AM) fungi (Funneliformis mosseae) on growth, foliar nitrogen mobilization, and phosphorus partitioning in cowpea (Vigna unguiculata cv. Vita-5) plants. The experiment was conducted in a greenhouse in pots containing a mixture of vermiculite and sterilized quartz sand. Mycorrhizal and non-mycorrhizal cowpea plants were supplied with three levels of soluble P (0.1 (low P), 0.5 (medium P), or 1.0 mM (high P)).Cowpea plants supplied with low P fertilization showed significantly (p < 0.05) higher root colonization than those with medium and high P fertilization at both the vegetative and pod-filling stages. P uptake and growth parameters of cowpea plants were positively influenced by mycorrhizal inoculation only in the medium P fertilization treatment at the vegetative stage. Lack of these effects in the other treatments may be linked to either a very low P supply (in the low P treatment at the vegetative stage) or the availability of optimal levels of freely diffusible P in the substrate towards the pod-filling stage due to accumulation with time. The N concentration in leaves of all cowpea plants were lower at the pod-filling stage than at the vegetative stage, presumably as a result of N mobilization from vegetative organs to the developing pods. This was however not influenced by AM fungal inoculation and may be a consequence of the lack of an improved plant P acquisition by the fungus at the pod-filling stage.

  2. Plant Signals Disrupt (regulate?) Arbuscular Mycorrhizal Fungal Growth Under Enhanced Ozone and CO2 Growing Conditions for Populus tremuloides

    NASA Astrophysics Data System (ADS)

    Miller, R. M.; Podila, G. K.

    2008-12-01

    An understanding of the genetic determinants of keystone symbiotic relationships is essential to elucidating adaptive mechanisms influencing higher-order processes, including shifts in community composition following environmental perturbations. The Aspen FACE project offers a unique opportunity to address adaptive processes with an imposed three way interaction experiment composed of the atmospheric pollutant ozone (eO3), elevated CO2 (eCO2) fumigations, five Populus tremuloides (aspen) genotypes, and both arbuscular mycorrhizal and ectomycorrhizal fungal interactions. The 10 year time span of this experiment has allowed for a realistic and mechanistic understanding of above ground responses of the aspen genotypes to eCO2, eO3 and the interaction effects of eCO2 and eO3. Even so, treatment influences to the below ground, including carbon allocation to roots and associated mycorrhizal symbionts, and rhizosphere dynamics are just beginning to be understood. We hypothesized that mycorrhizal fungal responses to eCO2, eO3, and the interaction effects of eCO2+eO3 are conditioned by the degree of response of their aspen hosts. We intend to describe the molecular mechanisms of an important critical interaction between host and fungus using microarray analysis of expression profiles, as well as metabolic profiling of aspen roots and their associated mycorrhizal partner, the arbuscular mycorrhizal fungus (AMF) Glomus intraradices, under eCO2, eO3 and eCO2+eO3. We present evidence that host-derived factors, expressed in response to eCO2+eO3, trigger responses in Glomus leading to the partitioning or metabolic shift in lipid biosynthesis that is associated with reduced extraradical hyphae growth and altered lipid metabolism. We then scale these lower-level responses to give better insight to fungal intraradical and extraradical allocation of biomass and fungal and root lipid and carbohydrate content in association with aspen genotype responses to the imposed treatments. By

  3. Differential response of delta13C and water use efficiency to arbuscular mycorrhizal infection in two aridland woody plant species.

    PubMed

    Querejeta, José Ignacio; Barea, José Miguel; Allen, Michael F; Caravaca, Fuensanta; Roldán, Antonio

    2003-05-01

    During a revegetation field experiment in Southeast Spain, we measured foliar carbon isotope ratios (delta13C) and gas exchange parameters in order to evaluate the influence of arbuscular mycorrhizal (AM) infection on the water use efficiency (WUE) of two semiarid woodland species. WUE during drought was significantly enhanced by inoculation with Glomus intraradices in Olea europaea ssp sylvestris, but not in Rhamnus lycioides. While Olea is a long-lived, slow-growing evergreen tree with a conservative water use strategy, Rhamnus is a drought-deciduous shrub with a shorter lifespan; these differences may explain their dissimilar patterns of physiological response to inoculation with the same AM fungus. Differences in delta13C and WUE between Olea and Rhamnus were larger when comparing AM inoculated than non-inoculated seedlings. This result suggests that some of the interspecific variability in delta13C observed for aridland plant communities may be due to different physiological responses to mycorrhization.

  4. Effect of environmental gradient in coastal vegetation on communities of arbuscular mycorrhizal fungi associated with Ixeris repens (Asteraceae).

    PubMed

    Yamato, Masahide; Yagame, Takahiro; Yoshimura, Yuko; Iwase, Koji

    2012-11-01

    The community structure of arbuscular mycorrhizal (AM) fungi associated with Ixeris repens was studied in coastal vegetation near the Tottori sand dunes in Japan. I. repens produces roots from a subterranean stem growing near the soil surface which provides an opportunity to examine the effects of an environmental gradient related to distance from the sea on AM fungal communities at a regular soil depth. Based on partial sequences of the nuclear large subunit ribosomal RNA gene, AM fungi in root samples were divided into 17 phylotypes. Among these, five AM fungal phylotypes in Glomus and Diversispora were dominant near the seaward forefront of the vegetation. Redundancy analysis of the AM fungal community showed significant relationships between the distribution of phylotypes and environmental variables such as distance from the sea, water-soluble sodium in soil, and some coexisting plant species. These results suggest that environmental gradients in the coastal vegetation can be determinants of the AM fungal community.

  5. Remediation of polychlorinated biphenyl-contaminated soil by using a combination of ryegrass, arbuscular mycorrhizal fungi and earthworms.

    PubMed

    Lu, Yan-Fei; Lu, Mang; Peng, Fang; Wan, Yun; Liao, Min-Hong

    2014-07-01

    In this work, a laboratory experiment was performed to investigate the influences of inoculation with the arbuscular mycorrhizal fungus (AMF) Glomus caledoniun L. and/or epigeic earthworms (Eisenia foetida) on phytoremediation of a PCB-contaminated soil by ryegrass grown for 180d. Planting ryegrass, ryegrass inoculated with earthworms, ryegrass inoculated with AMF, and ryegrass co-inoculated with AMF and earthworms decreased significantly initial soil PCB contents by 58.4%, 62.6%, 74.3%, and 79.5%, respectively. Inoculation with AMF and/or earthworms increased the yield of plants, and the accumulation of PCBs in ryegrass. However, PCB uptake by ryegrass accounted for a negligible portion of soil PCB removal. The number of soil PCB-degrading populations increased when ryegrass was inoculated with AMF and/or earthworms. The data show that fungal inoculation may significantly increase the remedial potential of ryegrass for soil contaminated with PCBs.

  6. The exotic legume tree species Acacia holosericea alters microbial soil functionalities and the structure of the arbuscular mycorrhizal community.

    PubMed

    Remigi, P; Faye, A; Kane, A; Deruaz, M; Thioulouse, J; Cissoko, M; Prin, Y; Galiana, A; Dreyfus, B; Duponnois, R

    2008-03-01

    The response of microbial functional diversity as well as its resistance to stress or disturbances caused by the introduction of an exotic tree species, Acacia holosericea, ectomycorrhized or not with Pisolithus albus, was examined. The results show that this ectomycorrhizal fungus promotes drastically the growth of this fast-growing tree species in field conditions after 7 years of plantation. Compared to the crop soil surrounding the A. holosericea plantation, this exotic tree species, associated or not with the ectomycorrhizal symbiont, induced strong modifications in soil microbial functionalities (assessed by measuring the patterns of in situ catabolic potential of microbial communities) and reduced soil resistance in response to increasing stress or disturbance (salinity, temperature, and freeze-thaw and wet-dry cycles). In addition, A. holosericea strongly modified the structure of arbuscular mycorrhizal fungus communities. These results show clearly that exotic plants may be responsible for important changes in soil microbiota affecting the structure and functions of microbial communities.

  7. The role of carbon in fungal nutrient uptake and transport: implications for resource exchange in the arbuscular mycorrhizal symbiosis.

    PubMed

    Fellbaum, Carl R; Mensah, Jerry A; Pfeffer, Philip E; Kiers, E Toby; Bücking, Heike

    2012-11-01

    The arbuscular mycorrhizal (AM) symbiosis, which forms between plant hosts and ubiquitous soil fungi of the phylum Glomeromycota, plays a key role for the nutrient uptake of the majority of land plants, including many economically important crop species. AM fungi take up nutrients from the soil and exchange them for photosynthetically fixed carbon from the host. While our understanding of the exact mechanisms controlling carbon and nutrient exchange is still limited, we recently demonstrated that (i) carbon acts as an important trigger for fungal N uptake and transport, (ii) the fungus changes its strategy in response to an exogenous supply of carbon, and that (iii) both plants and fungi reciprocally reward resources to those partners providing more benefit. Here, we summarize recent research findings and discuss the implications of these results for fungal and plant control of resource exchange in the AM symbiosis.

  8. Beneficial role of plant growth promoting bacteria and arbuscular mycorrhizal fungi on plant responses to heavy metal stress.

    PubMed

    Gamalero, Elisa; Lingua, Guido; Berta, Graziella; Glick, Bernard R

    2009-05-01

    Heavy metal pollution is a major worldwide environmental concern that has recently motivated researchers to develop a variety of novel approaches towards its cleanup. As an alternative to traditional physical and chemical methods of environmental cleanup, scientists have developed phytoremediation approaches that include the use of plants to remove or render harmless a range of compounds. Both plant growth promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) can be used to facilitate the process of phytoremediation and the growth of plants in metal-contaminated soils. This review focuses on the recent literature dealing with the effects of plant growth-promoting bacteria and AM fungi on the response of plants to heavy metal stress and points the way to strategies that may facilitate the practical realization of this technology.

  9. Arbuscular mycorrhizal morphology and dark septate fungal associations in medicinal and aromatic plants of Western Ghats, Southern India.

    PubMed

    Muthukumar, T; Senthilkumar, M; Rajangam, M; Udaiyan, K

    2006-12-01

    We investigated roots of 107 medicinal and aromatic plants (MAPs) in the Western Ghats region of Southern India for arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) associations. Of the 107 MAPs belonging to 98 genera in 52 families examined, 79 were AM and 38 harbored a DSE association. Typical Arum- and Paris-type mycorrhizas are first reported in the presumed nonmycorrhizal family Amaranthaceae. Similarly, DSE associations are recorded for the first time in nine plant families and 37 plant species. Thirty MAPs had both AM and DSE associations. The number of MAPs having Arum-type mycorrhiza was greater than those having Paris-type. This was more prominent among herbaceous plants than in trees where the Paris-type was predominant. Similarly, the Arum-type was more prevalent in annuals than in perennials. DSE associations were more frequent in herbs and perennials compared to other MAPs.

  10. Arbuscular mycorrhizal fungi in phytoremediation of contaminated areas by trace elements: mechanisms and major benefits of their applications.

    PubMed

    Cabral, Lucélia; Soares, Claúdio Roberto Fonsêca Sousa; Giachini, Admir José; Siqueira, José Oswaldo

    2015-11-01

    In recent decades, the concentration of trace elements has increased in soil and water, mainly by industrialization and urbanization. Recovery of contaminated areas is generally complex. In that respect, microorganisms can be of vital importance by making significant contributions towards the establishment of plants and the stabilization of impacted areas. Among the available strategies for environmental recovery, bioremediation and phytoremediation outstand. Arbuscular mycorrhizal fungi (AMF) are considered the most important type of mycorrhizae for phytoremediation. AMF have broad occurrence in contaminated soils, and evidences suggest they improve plant tolerance to excess of certain trace elements. In this review, the use of AMF in phytoremediation and mechanisms involved in their trace element tolerance are discussed. Additionally, we present some techniques used to study the retention of trace elements by AMF, as well as a summary of studies showing major benefits of AMF for phytoremediation.

  11. Synergistic effects of arbuscular mycorrhizal fungi and phosphate rock on heavy metal uptake and accumulation by an arsenic hyperaccumulator.

    PubMed

    Leung, H M; Wu, F Y; Cheung, K C; Ye, Z H; Wong, M H

    2010-09-15

    The effects of arbuscular mycorrhizal (AM) fungi and phosphate rock on the phytorextraction efficiency of a hyperaccumulator (Pteris vittata) and a non-hyperaccumulator (Cynodon dactylon) plant were studied. Both seedlings were planted in As contaminated soil under different treatments [(1) control (contaminated soil only), (2) indigenous mycorrhizas (IM), (3) mixed AM inoculum [indigenous mycorrhiza + Glomus mosseae (IM/Gm)] and (4) IM/Gm + phosphate rock (P rock)] with varying intensities (40%, 70% and 100%) of water moisture content (WMC). Significant As reduction in soil (23.8% of soil As reduction), increase in plant biomass (17.8 g/pot) and As accumulation (2054 mg/kg DW) were observed for P. vittata treated with IM/Gm + PR at 100% WMC level. The overall results indicated that the synergistic effect of mycorrhiza and P rock affected As subcellular distribution of the hyperaccumulator and thereby altered its As removal efficiency under well-watered conditions.

  12. Molecular community analysis of arbuscular mycorrhizal fungi in roots of geothermal soils in Yellowstone National Park (USA).

    PubMed

    Appoloni, Susann; Lekberg, Ylva; Tercek, Michael T; Zabinski, Catherine A; Redecker, Dirk

    2008-11-01

    To better understand adaptation of plants and their mycorrhizae to extreme environmental conditions, we analyzed the composition of communities of arbuscular mycorrhizal fungi (AMF) in roots from geothermal sites in Yellowstone National Park (YNP), USA. Arbuscular mycorrhizal fungi were identified using molecular methods including seven specific primer pairs for regions of the ribosomal DNA that amplify different subgroups of AMF. Roots of Dichanthelium lanuginosum, a grass only occurring in geothermal areas, were sampled along with thermal and nonthermal Agrostis scabra and control plants growing outside the thermally influenced sites. In addition, root samples of Agrostis stolonifera from geothermal areas of Iceland were analyzed to identify possible common mycosymbionts between these geographically isolated locations. In YNP, 16 ribosomal DNA phylotypes belonging to the genera Archaeospora, Glomus, Paraglomus, Scutellospora, and Acaulospora were detected. Eight of these phylotypes could be assigned to known morphospecies, two others have been reported previously in molecular studies from different environments, and six were new to science. The most diverse and abundant lineage was Glomus group A, with the most frequent phylotype corresponding to Glomus intraradices. Five of the seven phylotypes detected in a preliminary sampling in a geothermal area in Iceland were also found in YNP. Nonthermal vegetation was dominated by a high diversity of Glomus group A phylotypes while nonthermal plants were not. Using multivariate analyses, a subset of three phylotypes were determined to be associated with geothermal conditions in the field sites analyzed. In conclusion, AMF communities in geothermal soils are distinct in their composition, including both unique phylotypes and generalist fungi that occur across a broad range of environmental conditions.

  13. The composition of arbuscular mycorrhizal fungal communities in the roots of a ruderal forb is not related to the forest fragmentation process.

    PubMed

    Grilli, Gabriel; Urcelay, Carlos; Galetto, Leonardo; Davison, John; Vasar, Martti; Saks, Ülle; Jairus, Teele; Öpik, Maarja

    2015-08-01

    Land-use changes and forest fragmentation have strong impact on biodiversity. However, little is known about the influence of new landscape configurations on arbuscular mycorrhizal fungal (AMF) community composition. We used 454 pyrosequencing to assess AMF diversity in plant roots from a fragmented forest. We detected 59 virtual taxa (VT; phylogenetically defined operational taxonomic units) of AMF - including 10 new VT - in the roots of Euphorbia acerensis. AMF communities were mainly composed of members of family Glomeraceae and were similar throughout the fragmented landscape, despite variation in forest fragment size (i.e. small, medium and large) and isolation (i.e. varying pairwise distances). AMF communities in forest fragments were phylogenetically clustered compared with the global, but not regional and local AMF taxon pools. This indicates that non-random community assembly processes possibly related to dispersal limitation at a large scale, rather than habitat filtering or biotic interactions, may be important in structuring the AMF communities. In this system, forest fragmentation did not appear to influence AMF community composition in the roots of the ruderal plant. Whether this is true for AMF communities in soil and the roots of other ecological groups of host plants or in other habitats deserves further study.

  14. The Cry1Ab Protein Has Minor Effects on the Arbuscular Mycorrhizal Fungal Communities after Five Seasons of Continuous Bt Maize Cultivation

    PubMed Central

    Shu, Yinghua; Zhang, Yanyan; Feng, Yuanjiao; Wang, Jianwu

    2015-01-01

    The cultivation of genetically modified plants (GMP) has raised concerns regarding the plants’ ecological safety. A greenhouse experiment was conducted to assess the impact of five seasons of continuous Bt (Bacillus thuringiensis) maize cultivation on the colonisation and community structure of the non-target organisms arbuscular mycorrhizal fungi (AMF) in the maize roots, bulk soils and rhizospheric soils using the terminal restriction fragment length polymorphism (T-RFLP) analysis of the 28S ribosomal DNA and sequencing methods. AMF colonisation was significantly higher in the two Bt maize lines that express Cry1Ab, 5422Bt1 (event Bt11) and 5422CBCL (MON810) than in the non-Bt isoline 5422. No significant differences were observed in the diversity of the AMF community between the roots, bulk soils and rhizospheric soils of the Bt and non-Bt maize cultivars. The AMF genus Glomus was dominant in most of the samples, as detected by DNA sequencing. A clustering analysis based on the DNA sequence data suggested that the sample types (i.e., the samples from the roots, bulk soils or rhizospheric soils) might have greater influence on the AMF community phylotypes than the maize cultivars. This study indicated that the Cry1Ab protein has minor effects on the AMF communities after five seasons of continuous Bt maize cultivation. PMID:26717324

  15. [Community diversity of bacteria and arbuscular mycorrhizal fungi in the rhizosphere of eight plants in Liudaogou watershed on the Loess Plateau China].

    PubMed

    Feng, Ye; Tang, Ming; Chen, Hui; Cong, Wei

    2012-01-01

    Terminal restriction fragment length polymorphism (T-RFLP) was used to examine the community diversity of bacteria and arbuscular mycorrhizal fungi (AMF) and their interrelation in the rhizosphere of 8 plants in the Liudaogou watershed in Shenmu County. The objective was to obtain diversity indices and provide theoretical basis for ecological restoration. Results showed significant variations in the species and abundances of rhizospheric bacteria and AMF associated with 8 plants. Among these, the Shannon diversity index of rhizospheric bacteria was the highest for Robinia pseudoacacia (4.01) and the lowest for Salix babylonica (2.18), whereas the Shannon diversity index of rhizospheric AMF was the highest for Populus simonii (2.07) and the lowest for Hippophae rhamnoides (1.21). Cluster analysis and redundancy analysis indicated a significant difference in associated microbial community structure, while the similarity among community diversity of rhizospheric bacteria and AMF associated with specific plants was also found. There was a significant correlation between diversity indices of bacteria and AMF (P < 0.01). Associated microbial community diversity was influenced primarily by organic matter and total nitrogen content. Our work demonstrated strong impacts of plant species and rhizospheric environment on associated microbial community structure. Due to the high diversity indices of rhizospheric bacteria and AMF, R. pseudoacacia was considered to be a pioneer plant species for vegetation restoration in the Liudaogou watershed.

  16. Arbuscular Mycorrhizal Fungi Community Structure, Abundance and Species Richness Changes in Soil by Different Levels of Heavy Metal and Metalloid Concentration

    PubMed Central

    Krishnamoorthy, Ramasamy; Kim, Chang-Gi; Subramanian, Parthiban; Kim, Ki-Yoon; Selvakumar, Gopal; Sa, Tong-Min

    2015-01-01

    Arbuscular Mycorrhizal Fungi (AMF) play major roles in ecosystem functioning such as carbon sequestration, nutrient cycling, and plant growth promotion. It is important to know how this ecologically important soil microbial player is affected by soil abiotic factors particularly heavy metal and metalloid (HMM). The objective of this study was to understand the impact of soil HMM concentration on AMF abundance and community structure in the contaminated sites of South Korea. Soil samples were collected from the vicinity of an abandoned smelter and the samples were subjected to three complementary methods such as spore morphology, terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis (DGGE) for diversity analysis. Spore density was found to be significantly higher in highly contaminated soil compared to less contaminated soil. Spore morphological study revealed that Glomeraceae family was more abundant followed by Acaulosporaceae and Gigasporaceae in the vicinity of the smelter. T-RFLP and DGGE analysis confirmed the dominance of Funneliformis mosseae and Rhizophagus intraradices in all the study sites. Claroideoglomus claroideum, Funneliformis caledonium, Rhizophagus clarus and Funneliformis constrictum were found to be sensitive to high concentration of soil HMM. Richness and diversity of Glomeraceae family increased with significant increase in soil arsenic, cadmium and zinc concentrations. Our results revealed that the soil HMM has a vital impact on AMF community structure, especially with Glomeraceae family abundance, richness and diversity. PMID:26035444

  17. Arbuscular mycorrhizal fungi community structure, abundance and species richness changes in soil by different levels of heavy metal and metalloid concentration.

    PubMed

    Krishnamoorthy, Ramasamy; Kim, Chang-Gi; Subramanian, Parthiban; Kim, Ki-Yoon; Selvakumar, Gopal; Sa, Tong-Min

    2015-01-01

    Arbuscular Mycorrhizal Fungi (AMF) play major roles in ecosystem functioning such as carbon sequestration, nutrient cycling, and plant growth promotion. It is important to know how this ecologically important soil microbial player is affected by soil abiotic factors particularly heavy metal and metalloid (HMM). The objective of this study was to understand the impact of soil HMM concentration on AMF abundance and community structure in the contaminated sites of South Korea. Soil samples were collected from the vicinity of an abandoned smelter and the samples were subjected to three complementary methods such as spore morphology, terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis (DGGE) for diversity analysis. Spore density was found to be significantly higher in highly contaminated soil compared to less contaminated soil. Spore morphological study revealed that Glomeraceae family was more abundant followed by Acaulosporaceae and Gigasporaceae in the vicinity of the smelter. T-RFLP and DGGE analysis confirmed the dominance of Funneliformis mosseae and Rhizophagus intraradices in all the study sites. Claroideoglomus claroideum, Funneliformis caledonium, Rhizophagus clarus and Funneliformis constrictum were found to be sensitive to high concentration of soil HMM. Richness and diversity of Glomeraceae family increased with significant increase in soil arsenic, cadmium and zinc concentrations. Our results revealed that the soil HMM has a vital impact on AMF community structure, especially with Glomeraceae family abundance, richness and diversity.

  18. Molecular diversity of arbuscular mycorrhizal fungi in onion roots from organic and conventional farming systems in the Netherlands.

    PubMed

    Galván, Guillermo A; Parádi, István; Burger, Karin; Baar, Jacqueline; Kuyper, Thomas W; Scholten, Olga E; Kik, Chris

    2009-06-01

    Diversity and colonization levels of naturally occurring arbuscular mycorrhizal fungi (AMF) in onion roots were studied to compare organic and conventional farming systems in the Netherlands. In 2004, 20 onion fields were sampled in a balanced survey between farming systems and between two regions, namely, Zeeland and Flevoland. In 2005, nine conventional and ten organic fields were additionally surveyed in Flevoland. AMF phylotypes were identified by rDNA sequencing. All plants were colonized, with 60% for arbuscular colonization and 84% for hyphal colonization as grand means. In Zeeland, onion roots from organic fields had higher fractional colonization levels than those from conventional fields. Onion yields in conventional farming were positively correlated with colonization level. Overall, 14 AMF phylotypes were identified. The number of phylotypes per field ranged from one to six. Two phylotypes associated with the Glomus mosseae-coronatum and the G. caledonium-geosporum species complexes were the most abundant, whereas other phylotypes were infrequently found. Organic and conventional farming systems had similar number of phylotypes per field and Shannon diversity indices. A few organic and conventional fields had larger number of phylotypes, including phylotypes associated with the genera Glomus-B, Archaeospora, and Paraglomus. This suggests that farming systems as such did not influence AMF diversity, but rather specific environmental conditions or agricultural practices.

  19. Rapid nitrogen transfer from ectomycorrhizal pines to adjacent ectomycorrhizal and arbuscular mycorrhizal plants in a California oak woodland.

    PubMed

    He, Xinhua; Bledsoe, Caroline S; Zasoski, Robert J; Southworth, Darlene; Horwath, William R

    2006-01-01

    Nitrogen transfer among plants in a California oak woodland was examined in a pulse-labeling study using 15N. The study was designed to examine N movement among plants that were mycorrhizal with ectomycorrhizas (EM), arbuscular mycorrhizas (AM), or both. Isotopically enriched N (K15NO3-) was applied to gray pine (Pinus sabiniana) foliage (donor) and traced to neighboring gray pine, blue oak (Quercus douglasii), buckbrush (Ceanothus cuneatus) and herbaceous annuals (Cynosurus echinatus, Torilis arvensis and Trifolium hirtum). After 2 wk, needles of 15N-treated pines and foliage from nearby annuals were similarly enriched, but little 15N had appeared in nontreated (receiver) pine needles, oak leaves or buckbrush foliage. After 4 wk foliar and root samples from pine, oak, buckbrush and annuals were significantly 15N-enriched, regardless of the type of mycorrhizal association. The rate of transfer during the first and second 2-wk periods was similar, and suggests that 15N could continue to be mobilized over longer times.

  20. Nonredundant regulation of rice arbuscular mycorrhizal symbiosis by two members of the phosphate transporter1 gene family.

    PubMed

    Yang, Shu-Yi; Grønlund, Mette; Jakobsen, Iver; Grotemeyer, Marianne Suter; Rentsch, Doris; Miyao, Akio; Hirochika, Hirohiko; Kumar, Chellian Santhosh; Sundaresan, Venkatesan; Salamin, Nicolas; Catausan, Sheryl; Mattes, Nicolas; Heuer, Sigrid; Paszkowski, Uta

    2012-10-01

    Pi acquisition of crops via arbuscular mycorrhizal (AM) symbiosis is becoming increasingly important due to limited high-grade rock Pi reserves and a demand for environmentally sustainable agriculture. Here, we show that 70% of the overall Pi acquired by rice (Oryza sativa) is delivered via the symbiotic route. To better understand this pathway, we combined genetic, molecular, and physiological approaches to determine the specific functions of two symbiosis-specific members of the PHOSPHATE TRANSPORTER1 (PHT1) gene family from rice, ORYsa;PHT1;11 (PT11) and ORYsa;PHT1;13 (PT13). The PT11 lineage of proteins from mono- and dicotyledons is most closely related to homologs from the ancient moss, indicating an early evolutionary origin. By contrast, PT13 arose in the Poaceae, suggesting that grasses acquired a particular strategy for the acquisition of symbiotic Pi. Surprisingly, mutations in either PT11 or PT13 affected the development of the symbiosis, demonstrating that both genes are important for AM symbiosis. For symbiotic Pi uptake, however, only PT11 is necessary and sufficient. Consequently, our results demonstrate that mycorrhizal rice depends on the AM symbiosis to satisfy its Pi demands, which is mediated by a single functional Pi transporter, PT11.

  1. Stars and symbiosis: microRNA- and microRNA*-mediated transcript cleavage involved in arbuscular mycorrhizal symbiosis.

    PubMed

    Devers, Emanuel A; Branscheid, Anja; May, Patrick; Krajinski, Franziska

    2011-08-01

    The majority of plants are able to form the arbuscular mycorrhizal (AM) symbiosis in association with AM fungi. During symbiosis development, plant cells undergo a complex reprogramming resulting in profound morphological and physiological changes. MicroRNAs (miRNAs) are important components of the regulatory network of plant cells. To unravel the impact of miRNAs and miRNA-mediated mRNA cleavage on root cell reprogramming during AM symbiosis, we carried out high-throughput (Illumina) sequencing of small RNAs and degradome tags of Medicago truncatula roots. This led to the annotation of 243 novel miRNAs. An increased accumulation of several novel and conserved miRNAs in mycorrhizal roots suggest a role of these miRNAs during AM symbiosis. The degradome analysis led to the identification of 185 root transcripts as mature miRNA and also miRNA*-mediated mRNA cleavage targets. Several of the identified miRNA targets are known to be involved in root symbioses. In summary, the increased accumulation of specific miRNAs and the miRNA-mediated cleavage of symbiosis-relevant genes indicate that miRNAs are an important part of the regulatory network leading to symbiosis development.

  2. Bacterial degradation of Aroclor 1242 in the mycorrhizosphere soils of zucchini (Cucurbita pepo L.) inoculated with arbuscular mycorrhizal fungi.

    PubMed

    Qin, Hua; Brookes, Philip C; Xu, Jianming; Feng, Youzhi

    2014-11-01

    A greenhouse experiment was conducted to investigate the effects of zucchini (Cucurbita pepo L.), inoculated with the arbuscular mycorrhizal (AM) species Acaulospora laevis, Glomus caledonium, and Glomus mosseae, on the soil bacterial community responsible for Aroclor 1242 dissipation. The dissipation rates of Aroclor 1242 and soil bacteria abundance were much higher with the A. laevis and G. mosseae treatments compared to the non-mycorrhizal control. The biphenyl dioxygenase (bphA) and Rhodococcus-like 2,3-dihydroxybiphenyl dioxygenase (bphC) genes were more abundant in AM inoculated soils, suggesting that the bphA and Rhodococcus-like bphC pathways play an important role in Aroclor 1242 dissipation in the mycorrhizosphere. The soil bacterial communities were dominated by classes Betaproteobacteria and Actinobacteria, while the relative proportion of Actinobacteria was significantly (F=2.288, P<0.05) correlated with the PCB congener profile in bulk soil. Our results showed that AM fungi could enhance PCB dissipation by stimulating bph gene abundance and the growth of specific bacterial groups.

  3. Proteomic analysis as a tool for investigating arsenic stress in Pteris vittata roots colonized or not by arbuscular mycorrhizal symbiosis.

    PubMed

    Bona, Elisa; Marsano, Francesco; Massa, Nadia; Cattaneo, Chiara; Cesaro, Patrizia; Argese, Emanuele; Sanità di Toppi, Luigi; Cavaletto, Maria; Berta, Graziella

    2011-08-12

    Pteris vittata can tolerate very high soil arsenic concentration and rapidly accumulates the metalloid in its fronds. However, its tolerance to arsenic has not been completely explored. Arbuscular mycorrhizal (AM) fungi colonize the root of most terrestrial plants, including ferns. Mycorrhizae are known to affect plant responses in many ways: improving plant nutrition, promoting plant tolerance or resistance to pathogens, drought, salinity and heavy metal stresses. It has been observed that plants growing on arsenic polluted soils are usually mycorrhizal and that AM fungi enhance arsenic tolerance in a number of plant species. The aim of the present work was to study the effects of the AM fungus Glomus mosseae on P. vittata plants treated with arsenic using a proteomic approach. Image analysis showed that 37 spots were differently affected (21 identified). Arsenic treatment affected the expression of 14 spots (12 up-regulated and 2 down-regulated), while in presence of G. mosseae modulated 3 spots (1 up-regulated and 2 down-regulated). G. mosseae, in absence of arsenic, modulated 17 spots (13 up-regulated and 4 down-regulated). Arsenic stress was observed even in an arsenic tolerant plant as P. vittata and a protective effect of AM symbiosis toward arsenic stress was observed.

  4. Arbuscular mycorrhizal fungi native from a Mediterranean saline area enhance maize tolerance to salinity through improved ion homeostasis.

    PubMed

    Estrada, Beatriz; Aroca, Ricardo; Maathuis, Frans J M; Barea, José Miguel; Ruiz-Lozano, Juan Manuel

    2013-10-01

    Soil salinity restricts plant growth and productivity. Na(+) represents the major ion causing toxicity because it competes with K(+) for binding sites at the plasma membrane. Inoculation with arbuscular mycorrhizal fungi (AMF) can alleviate salt stress in the host plant through several mechanisms. These may include ion selection during the fungal uptake of nutrients from the soil or during transfer to the host plant. AM benefits could be enhanced when native AMF isolates are used. Thus, we investigated whether native AMF isolated from an area with problems of salinity and desertification can help maize plants to overcome the negative effects of salinity stress better than non-AM plants or plants inoculated with non-native AMF. Results showed that plants inoculated with two out the three native AMF had the highest shoot dry biomass at all salinity levels. Plants inoculated with the three native AMF showed significant increase of K(+) and reduced Na(+) accumulation as compared to non-mycorrhizal plants, concomitantly with higher K(+) /Na(+) ratios in their tissues. For the first time, these effects have been correlated with regulation of ZmAKT2, ZmSOS1 and ZmSKOR genes expression in the roots of maize, contributing to K(+) and Na(+) homeostasis in plants colonized by native AMF.

  5. Native arbuscular mycorrhizal fungi isolated from a saline habitat improved maize antioxidant systems and plant tolerance to salinity.

    PubMed

    Estrada, Beatriz; Aroca, Ricardo; Barea, José Miguel; Ruiz-Lozano, Juan Manuel

    2013-03-01

    High soil salinity is a serious problem for crop production because most of the cultivated plants are salt sensitive, which is also the case for the globally important crop plant maize. Salinity stress leads to secondary oxidative stress in plants and a correlation between antioxidant capacity and salt tolerance has been demonstrated in several plant species. The plant antioxidant capacity may be enhanced by arbuscular mycorrhizal fungi (AMF) and it has been proposed that AM symbiosis is more effective with native than with collection AMF species. Thus, we investigated whether native AMF isolated from a dry and saline environment can help maize plants to overcome salt stress better than AMF from a culture collection and whether protection against oxidative stress is involved in such an effect. Maize plants inoculated with three native AMF showed higher efficiency of photosystem II and stomatal conductance, which surely decreased photorespiration and ROS production. Indeed, the accumulation of hydrogen peroxide, the oxidative damage to lipids and the membrane electrolyte leakage in these AM plants were significantly lower than in non-mycorrhizal plants or in plants inoculated with the collection AMF. The activation of antioxidant enzymes such as superoxide dismutase or catalase also accounted for these effects.

  6. Plant potassium content modifies the effects of arbuscular mycorrhizal symbiosis on root hydraulic properties in maize plants.

    PubMed

    El-Mesbahi, Mohamed Najib; Azcón, Rosario; Ruiz-Lozano, Juan Manuel; Aroca, Ricardo

    2012-10-01

    It is well known that the arbuscular mycorrhizal (AM) symbiosis helps the host plant to overcome several abiotic stresses including drought. One of the mechanisms for this drought tolerance enhancement is the higher water uptake capacity of the mycorrhizal plants. However, the effects of the AM symbiosis on processes regulating root hydraulic properties of the host plant, such as root hydraulic conductivity and plasma membrane aquaporin gene expression, and protein abundance, are not well defined. Since it is known that K(+) status is modified by AM and that it regulates root hydraulic properties, it has been tested how plant K(+) status could modify the effects of the symbiosis on root hydraulic conductivity and plasma membrane aquaporin gene expression and protein abundance, using maize (Zea mays L.) plants and Glomus intraradices as a model. It was observed that the supply of extra K(+) increased root hydraulic conductivity only in AM plants. Also, the different pattern of plasma membrane aquaporin gene expression and protein abundance between AM and non-AM plants changed with the application of extra K(+). Thus, plant K(+) status could be one of the causes of the different observed effects of the AM symbiosis on root hydraulic properties. The present study also highlights the critical importance of AM fungal aquaporins in regulating root hydraulic properties of the host plant.

  7. Evaluation of Arbuscular Mycorrhizal Fungi Capacity to Alleviate Abiotic Stress of Olive (Olea europaea L.) Plants at Different Transplant Conditions

    PubMed Central

    Bompadre, María Josefina; Pérgola, Mariana; Fernández Bidondo, Laura; Colombo, Roxana Paula; Silvani, Vanesa Analía; Pardo, Alejandro Guillermo; Ocampo, Juan Antonio; Godeas, Alicia Margarita

    2014-01-01

    The capacity of roots to sense soil physicochemical parameters plays an essential role in maintaining plant nutritional and developmental functions under abiotic stress. These conditions generate reactive oxygen species (ROS) in plant tissues causing oxidation of proteins and lipids among others. Some plants have developed adaptive mechanisms to counteract such adverse conditions such as symbiotic association with arbuscular mycorrhizal fungi (AMF). AMF enhance plant growth and improve transplant survival by protecting host plants against environmental stresses. The aim of this study was to evaluate the alleviation of transplanting stress by two strains of Rhizophagus irregularis (GC2 and GA5) in olive. Our results show that olive plants have an additional energetic expense in growth due to an adaptative response to the growing stage and to the mycorrhizal colonization at the first transplant. However, at the second transplant the coinoculation improves olive plant growth and protects against oxidative stress followed by the GA5-inoculation. In conclusion, a combination of two AMF strains at the beginning of olive propagation produces vigorous plants successfully protected in field cultivation even with an additional cost at the beginning of growth. PMID:24688382

  8. Diversity and distribution of arbuscular mycorrhizal fungi along altitudinal gradients in Mount Taibai of the Qinling Mountains.

    PubMed

    Shi, Zhaoyong; Wang, Fayuan; Zhang, Kai; Chen, Yinglong

    2014-12-01

    Elevational patterns of plant and animal diversity have been studied for centuries; however, the effects of land elevation on arbuscular mycorrhizal (AM) fungal diversity remains unclear. We examined AM fungal diversity and distribution along 19 elevation belts in Mount Taibai of the Qinling Mountains, with the aim to assess the altitudinal diversity patterns. In total, 63 AM fungal taxa belonging to 12 genera were discovered. Mycorrhizal colonization rates on roots; AM fungal spore density; and fungal species richness, evenness, and diversity had different patterns in terms of the changes of elevation. Root colonization followed a cubical parabolic pattern, with a peak and a foot at an elevation of about 2000 and 3000 m above sea level, respectively. Species richness decreased monotonically from the lowest to the highest elevations. Spore density and α-diversity exhibited a unimodal pattern and peaked at an elevation of 2107 and 1350 m, respectively. Species evenness increased monotonically at an elevation of between 1050 and 2250 m. β-Diversity also presented a basically incremental pattern along altitudinal gradients. Our findings suggest that elevation changes were the main factor governing the patterns of AM fungal diversity.

  9. Evaluation of arbuscular mycorrhizal fungi capacity to alleviate abiotic stress of olive (Olea europaea L.) plants at different transplant conditions.

    PubMed

    Bompadre, María Josefina; Pérgola, Mariana; Fernández Bidondo, Laura; Colombo, Roxana Paula; Silvani, Vanesa Analía; Pardo, Alejandro Guillermo; Ocampo, Juan Antonio; Godeas, Alicia Margarita

    2014-01-01

    The capacity of roots to sense soil physicochemical parameters plays an essential role in maintaining plant nutritional and developmental functions under abiotic stress. These conditions generate reactive oxygen species (ROS) in plant tissues causing oxidation of proteins and lipids among others. Some plants have developed adaptive mechanisms to counteract such adverse conditions such as symbiotic association with arbuscular mycorrhizal fungi (AMF). AMF enhance plant growth and improve transplant survival by protecting host plants against environmental stresses. The aim of this study was to evaluate the alleviation of transplanting stress by two strains of Rhizophagus irregularis (GC2 and GA5) in olive. Our results show that olive plants have an additional energetic expense in growth due to an adaptative response to the growing stage and to the mycorrhizal colonization at the first transplant. However, at the second transplant the coinoculation improves olive plant growth and protects against oxidative stress followed by the GA5-inoculation. In conclusion, a combination of two AMF strains at the beginning of olive propagation produces vigorous plants successfully protected in field cultivation even with an additional cost at the beginning of growth.

  10. Influence of colonisation by an arbuscular mycorrhizal fungus on the growth of seedlings of Banksia ericifolia (Proteaceae).

    PubMed

    Pattinson, G S; McGee, P A

    2004-04-01

    Tap and primary lateral roots of seedlings of the putatively non-mycorrhizal Banksia ericifolia became marginally colonised when grown in an established mycelium of an arbuscular mycorrhizal (AM) fungus in the laboratory. A similar degree of colonisation was found in seedlings from an open woodland. All colonies lacked arbuscules. Two factors influencing colonisation and associated growth of host plants were examined experimentally: concentration of P in the soil and organic energy associated with the fungus. While some inoculated seedlings were slightly smaller when colonised by AM fungi, the results were inconsistent and never statistically significant. Seedlings take up insignificant quantities of soil P during early growth, even in the presence of abundant added P. Though colonisation was minor in all cases, an existing mycelium, whether or not connected to a companion plant, slightly increased the amount of root of B. ericifolia colonised by an AM fungus. All seedlings grew slowly. Shoots were significantly larger than roots, until the initiation of proteoid roots which commenced at about 40 days after germination, with both relatively high and low P supply.

  11. A diffusible signal from arbuscular mycorrhizal fungi elicits a transient cytosolic calcium elevation in host plant cells.

    PubMed

    Navazio, Lorella; Moscatiello, Roberto; Genre, Andrea; Novero, Mara; Baldan, Barbara; Bonfante, Paola; Mariani, Paola

    2007-06-01

    The implication of calcium as intracellular messenger in the arbuscular mycorrhizal (AM) symbiosis has not yet been directly demonstrated, although often envisaged. We used soybean (Glycine max) cell cultures stably expressing the bioluminescent Ca(2+) indicator aequorin to detect intracellular Ca(2+) changes in response to the culture medium of spores of Gigaspora margarita germinating in the absence of the plant partner. Rapid and transient elevations in cytosolic free Ca(2+) were recorded, indicating that diffusible molecules released by the mycorrhizal fungus are perceived by host plant cells through a Ca(2+)-mediated signaling. Similar responses were also triggered by two Glomus isolates. The fungal molecules active in generating the Ca(2+) transient were constitutively released in the medium, and the induced Ca(2+) signature was not modified by the coculture of germinating spores with plant cells. Even ungerminated spores were able to generate the signaling molecules, as proven when the germination was blocked by a low temperature. The fungal molecules were found to be stable to heat treatment, of small molecular mass (<3 kD), and, on the basis of extraction with an organic solvent, partially lipophilic. Evidence for the specificity of such an early fungal signal to the AM symbiosis is suggested by the lack of a Ca(2+) response in cultured cells of the nonhost plant Arabidopsis (Arabidopsis thaliana) and by the up-regulation in soybean cells of genes related to Medicago truncatula DMI1, DMI2, and DMI3 and considered essential for the establishment of the AM symbiosis.

  12. Biotic and Abiotic Stimulation of Root Epidermal Cells Reveals Common and Specific Responses to Arbuscular Mycorrhizal Fungi1[W

    PubMed Central

    Genre, Andrea; Ortu, Giuseppe; Bertoldo, Chiara; Martino, Elena; Bonfante, Paola

    2009-01-01

    During arbuscular mycorrhizal (AM) colonization, a focal accumulation of organelles occurs in root epidermal cells, prior to fungal penetration, beneath adhering hyphopodia. This is followed by the appearance of the prepenetration apparatus (PPA), a transcellular column of cytoplasm connected to the nucleus and rich in cytoskeleton and secretory endomembranes. This apparatus appears to be responsible for the construction of an apoplastic compartment that confines the fungus within the cell lumen. To identify AM-specific elements within the PPA response, we challenged root cultures of Medicago truncatula, expressing a green fluorescent protein tag for the endoplasmic reticulum, with an AM symbiont, a necrotrophic pathogen, a hemibiotrophic pathogen, a noncompatible endomycorrhizal fungus, or abiotic physical stimuli. Parallel experiments were made on a M. truncatula nonsymbiotic mutant (doesn't make infections, dmi3-1). The results have highlighted a correlation between physical stimulation of the cell surface and nuclear repositioning. Cytoplasmic aggregation was only induced by contact with compatible fungi, whereas PPA appearance was specifically triggered by the AM fungus. The dmi3-1 mutant did not develop cytoplasmic aggregation or PPA and underwent cell death upon physical stimulation. The up-regulation of an expansin-like gene, already identified as an early marker of AM fungal contact, was triggered in wild-type roots by all the fungi tested. Such observations identify responses that are specific to mycorrhizal interactions and extend the role of the DMI3 protein, a calcium/calmodulin-dependent kinase, from symbiotic to pathogenic interactions. PMID:19151131

  13. 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.

  14. Arbuscular mycorrhizal fungi increased growth, nutrient uptake and tolerance to salinity in olive trees under nursery conditions.

    PubMed

    Porras-Soriano, Andrés; Soriano-Martín, María Luisa; Porras-Piedra, Andrés; Azcón, Rosario

    2009-09-01

    Inoculating olive plantlets with the arbuscular mycorrhizal fungi (AMF) Glomus mosseae, Glomus intraradices or Glomus claroideum increased plant growth and the ability to acquire nitrogen, phosphorus, and potassium from non-saline as well as saline media. AMF-colonized plants also increased in survival rate after transplant. Osmotic stress caused by NaCl supply reduced stem diameter, number of shoots, shoot length and nutrients in olive plants, but AMF colonization alleviated all of these negative effects on growth. G. mosseae was the most efficient fungus in reducing the detrimental effects of salinity; it increased shoot growth by 163% and root growth by 295% in the non-saline medium, and by 239% (shoot) and by 468% (root) under the saline conditions. AMF colonization enhanced salt tolerance in terms of olive growth and nutrient acquisition. Mycorrhizal olive plants showed the lowest biomass reduction under salinity (34%), while growth was reduced by 78% in control plants. This G. mosseae effect seems to be due to increased K acquisition; K content was enhanced under salt conditions by 6.4-fold with G. mosseae, 3.4-fold with G. intraradices, and 3.7-fold with G. claroideum. Potassium, as the most prominent inorganic solute, plays a key role in the osmoregulation processes and the highest salinity tolerance of G. mosseae-colonized olive trees was concomitant with an enhanced K concentration in olive plants.

  15. Current developments in arbuscular mycorrhizal fungi research and its role in salinity stress alleviation: a biotechnological perspective.

    PubMed

    Kumar, Ashwani; Dames, Joanna F; Gupta, Aditi; Sharma, Satyawati; Gilbert, Jack A; Ahmad, Parvaiz

    2015-01-01

    Arbuscular mycorrhizal fungi (AMF) form widespread symbiotic associations with 80% of known land plants. They play a major role in plant nutrition, growth, water absorption, nutrient cycling and protection from pathogens, and as a result, contribute to ecosystem processes. Salinity stress conditions undoubtedly limit plant productivity and, therefore, the role of AMF as a biological tool for improving plant salt stress tolerance, is gaining economic importance worldwide. However, this approach requires a better understanding of how plants and AMF intimately interact with each other in saline environments and how this interaction leads to physiological changes in plants. This knowledge is important to develop sustainable strategies for successful utilization of AMF to improve plant health under a variety of stress conditions. Recent advances in the field of molecular biology, "omics" technology and advanced microscopy can provide new insight about these mechanisms of interaction between AMF and plants, as well as other microbes. This review mainly discusses the effect of salinity on AMF and plants, and role of AMF in alleviation of salinity stress including insight on methods for AMF identification. The focus remains on latest advancements in mycorrhizal research that can potentially offer an integrative understanding of the role of AMF in salinity tolerance and sustainable crop production.

  16. Distribution of arbuscular mycorrhizal fungi associated with different land use systems of Arunachal Pradesh of Eastern Himalayan region.

    PubMed

    Bordoloi, A; Nath, P C; Shukla, A K

    2015-10-01

    Arbuscular mycorrhizal fungi are the main component of soil microbial population in most agroecosystems. They forms a close association with more than 80% of the plant species making immobilized mineral nutrients available to the plants in order to sustain normal growth and reproduction. In this study the diversity of mycorrhizal fungi has been examined in seven land use ecosystems of Arunachal Pradesh in Eastern Himalayan region. A total of 24 species of AM fungi belonging to 4 genera viz., Glomus, Scutellospora, Aculospora and Gigaspora were isolated from the soil samples collected from different land use systems. Glomus was the dominant genera and Glomus occulatum was the most abundant species in all the seven land use systems. Total spore number was highly variable among all the land use systems. Species richness was recorded highest in natural forest that maintains a faster nutrient cycle with the highest diversity index. The Jhum fallow land and tea garden has the least number of AM fungal species due to high disturbance of fire and application of fungicides and inorganic fertilizer. Further the plant species composition, particularly the ground vegetation coverage and disturbance level affects the distribution of the AM fungal species. In our study it has been shown that AMF diversity is significantly affected by the land use practices practiced by the people. Hence, the AM fungi isolated from different land use system may be useful in improving the agriculture practices particularly the plantation crops in the region.

  17. A shift from arbuscular mycorrhizal to dark septate endophytic colonization in Deschampsia flexuosa roots occurs along primary successional gradient.

    PubMed

    Huusko, K; Ruotsalainen, A L; Markkola, A M

    2017-02-01

    Soil fungal community and dominant mycorrhizal types are known to shift along with plant community changes during primary succession. However, it is not well understood how and why root fungal symbionts and colonization types vary within the plant host when the host species is able to thrive both at young and at old successional stages with different light and nutrient resource availability. We asked (i) how root fungal colonization of Deschampsia flexuosa (Poaceae) by arbuscular mycorrhizal (AM) fungi and dark septate endophytes (DSE) changes along a postglacial primary successional land uplift gradient. As neighboring vegetation may play a role in root fungal colonization, we also asked (ii) whether removal of the dominant neighbor, Empetrum nigrum ssp. hermaphroditum (Ericaceae), affects root fungal colonization of Deschampsia. We also studied whether (iii) foliar carbon (C) and nitrogen (N) concentration of Deschampsia is related to successional changes along a land uplift gradient. AM colonization decreased (-50 %), DSE colonization increased (+200 %), and foliar C declined in Deschampsia along with increasing successional age, whereas foliar N was not affected. Empetrum removal did not affect AM colonization but increased DSE sclerotial colonization especially at older successional stages. The observed decrease in foliar C coincides with an increase in canopy closure along with increasing successional age. We suggest that the shift from an AM-dominated to a DSE-dominated root fungal community in Deschampsia along a land uplift successional gradient may be related to different nutritional benefits gained through these root fungal groups.

  18. Genome-wide analysis of copper, iron and zinc transporters in the arbuscular mycorrhizal fungus Rhizophagus irregularis.

    PubMed

    Tamayo, Elisabeth; Gómez-Gallego, Tamara; Azcón-Aguilar, Concepción; Ferrol, Nuria

    2014-01-01

    Arbuscular mycorrhizal fungi (AMF), belonging to the Glomeromycota, are soil microorganisms that establish mutualistic symbioses with the majority of higher plants. The efficient uptake of low mobility mineral nutrients by the fungal symbiont and their further transfer to the plant is a major feature of this symbiosis. Besides improving plant mineral nutrition, AMF can alleviate heavy metal toxicity to their host plants and are able to tolerate high metal concentrations in the soil. Nevertheless, we are far from understanding the key molecular determinants of metal homeostasis in these organisms. To get some insights into these mechanisms, a genome-wide analysis of Cu, Fe and Zn transporters was undertaken, making use of the recently published whole genome of the AMF Rhizophagus irregularis. This in silico analysis allowed identification of 30 open reading frames in the R. irregularis genome, which potentially encode metal transporters. Phylogenetic comparisons with the genomes of a set of reference fungi showed an expansion of some metal transporter families. Analysis of the published transcriptomic profiles of R. irregularis revealed that a set of genes were up-regulated in mycorrhizal roots compared to germinated spores and extraradical mycelium, which suggests that metals are important for plant colonization.

  19. Arbuscular mycorrhizal fungi and plant growth-promoting pseudomonads improve yield, quality and nutritional value of tomato: a field study.

    PubMed

    Bona, Elisa; Cantamessa, Simone; Massa, Nadia; Manassero, Paola; Marsano, Francesco; Copetta, Andrea; Lingua, Guido; D'Agostino, Giovanni; Gamalero, Elisa; Berta, Graziella

    2017-01-01

    The aim of this work was to assess the effects of plant-beneficial microorganisms (two Pseudomonas strains and a mixed mycorrhizal inoculum, alone or in combination) on the quality of tomato fruits of plants grown in the field and subjected to reduced fertilization. Pseudomonas strain 19Fv1T was newly characterized during this study. The size and quality of the fruits (concentration of sugars, organic acids and vitamin C) were assessed. The microorganisms positively affected the flower and fruit production and the concentrations of sugars and vitamins in the tomato fruits. In particular, the most important effect induced by arbuscular mycorrhizal (AM) fungi was an improvement of citric acid concentration, while bacteria positively modulated sugar production and the sweetness of the tomatoes. The novelty of the present work is the application of soil microorganisms in the field, in a real industrial tomato farm. This approach provided direct information about the application of inocula, allowed the reduction of chemical inputs and positively influenced tomato quality.

  20. The bifunctional plant receptor, OsCERK1, regulates both chitin-triggered immunity and arbuscular mycorrhizal symbiosis in rice.

    PubMed

    Miyata, Kana; Kozaki, Toshinori; Kouzai, Yusuke; Ozawa, Kenjirou; Ishii, Kazuo; Asamizu, Erika; Okabe, Yoshihiro; Umehara, Yosuke; Miyamoto, Ayano; Kobae, Yoshihiro; Akiyama, Kohki; Kaku, Hanae; Nishizawa, Yoko; Shibuya, Naoto; Nakagawa, Tomomi

    2014-11-01

    Plants are constantly exposed to threats from pathogenic microbes and thus developed an innate immune system to protect themselves. On the other hand, many plants also have the ability to establish endosymbiosis with beneficial microbes such as arbuscular mycorrhizal (AM) fungi or rhizobial bacteria, which improves the growth of host plants. How plants evolved these systems managing such opposite plant-microbe interactions is unclear. We show here that knockout (KO) mutants of OsCERK1, a rice receptor kinase essential for chitin signaling, were impaired not only for chitin-triggered defense responses but also for AM symbiosis, indicating the bifunctionality of OsCERK1 in defense and symbiosis. On the other hand, a KO mutant of OsCEBiP, which forms a receptor complex with OsCERK1 and is essential for chitin-triggered immunity, established mycorrhizal symbiosis normally. Therefore, OsCERK1 but not chitin-triggered immunity is required for AM symbiosis. Furthermore, experiments with chimeric receptors showed that the kinase domains of OsCERK1 and homologs from non-leguminous, mycorrhizal plants could trigger nodulation signaling in legume-rhizobium interactions as the kinase domain of Nod factor receptor1 (NFR1), which is essential for triggering the nodulation program in leguminous plants, did. Because leguminous plants are believed to have developed the rhizobial symbiosis on the basis of AM symbiosis, our results suggest that the symbiotic function of ancestral CERK1 in AM symbiosis enabled the molecular evolution to leguminous NFR1 and resulted in the establishment of legume-rhizobia symbiosis. These results also suggest that OsCERK1 and homologs serve as a molecular switch that activates defense or symbiotic responses depending on the infecting microbes.

  1. Local and distal effects of arbuscular mycorrhizal colonization on direct pathway Pi uptake and root growth in Medicago truncatula.

    PubMed

    Watts-Williams, Stephanie J; Jakobsen, Iver; Cavagnaro, Timothy R; Grønlund, Mette

    2015-07-01

    Two pathways exist for plant Pi uptake from soil: via root epidermal cells (direct pathway) or via associations with arbuscular mycorrhizal (AM) fungi, and the two pathways interact in a complex manner. This study investigated distal and local effects of AM colonization on direct root Pi uptake and root growth, at different soil P levels. Medicago truncatula was grown at three soil P levels in split-pots with or without AM fungal inoculation and where one root half grew into soil labelled with (33)P. Plant genotypes included the A17 wild type and the mtpt4 mutant. The mtpt4 mutant, colonized by AM fungi, but with no functional mycorrhizal pathway for Pi uptake, was included to better understand effects of AM colonization per se. Colonization by AM fungi decreased expression of direct Pi transporter genes locally, but not distally in the wild type. In mtpt4 mutant plants, direct Pi transporter genes and the Pi starvation-induced gene Mt4 were more highly expressed than in wild-type roots. In wild-type plants, less Pi was taken up via the direct pathway by non-colonized roots when the other root half was colonized by AM fungi, compared with non-mycorrhizal plants. Colonization by AM fungi strongly influenced root growth locally and distally, and direct root Pi uptake activity locally, but had only a weak influence on distal direct pathway activity. The responses to AM colonization in the mtpt4 mutant suggested that in the wild type, the increased P concentration of colonized roots was a major factor driving the effects of AM colonization on direct root Pi uptake.

  2. [Effects of arbuscular mycorrhizal fungi on the vegetation restoration of different types of coal mine spoil banks].

    PubMed

    Zhao, Ren-Xin; Guo, Wei; Fu, Rui-Ying; Zhao, Wen-Jing; Guo, Jiang-Yuan; Bi, Na; Zhang, Jun

    2013-11-01

    A greenhouse pot experiment was conducted to investigate the influence of arbuscular mycorrhizal (AM) fungi Glomus etunicatum (GE) and Glomus versiforme (GV) on the plant growth, nutrient uptake, C: N: P stoichiometric, uptake of heavy metals by maize (Zea mays L.) grown in three types of coal mine spoil banks. The aim was to provide a technical basis for the revegetation of coal mine spoil banks in grassland ecosystem. The results indicated that the symbiotic associations were successfully established between two isolates and maize grown in the three substrates, with an average mycorrhizal colonization rate ranging from 36% to 54%. The colonization of two AM fungi significantly increased the dry weight of maize grown in recent discharged and weathered coal mine spoils and GE increased those grown in weathered coal mine spoil. Inoculation with AM fungi promoted the uptake of N, P and K by maize to varying degrees. In addition, inoculation with GE and GV also decreased C: N: P ratios, supporting the growth rate hypothesis, and had significantly differences on concentrations of Cu, Fe, Mn and Zn in shoots and roots of maize. The results indicated that GE and GV had different mycorrhizal effects on maize in the three types of substrates. GV was more suitable for the revegetation of recent discharged coal mine spoil and weathered coal mine spoil, while GE was more suitable for the revegetation of spontaneous combusted coal mine spoil. The experiment demonstrates that AM fungi have a potential role for maize to enhance the ability to adapt the composite adversity of different types of coal mine spoil and play a positive role in the revegetation of different coal mine spoil banks. Further field experiments should be conducted to evaluate the practical effects of AM fungi on the vegetation restoration of different types of coal mine spoil under field conditions.

  3. Increased photosynthetic acclimation in alfalfa associated with arbuscular mycorrhizal fungi (AMF) and cultivated in greenhouse under elevated CO2.

    PubMed

    Goicoechea, Nieves; Baslam, Marouane; Erice, Gorka; Irigoyen, Juan José

    2014-11-15

    Medicago sativa L. (alfalfa) can exhibit photosynthetic down-regulation when grown in greenhouse conditions under elevated atmospheric CO2. This forage legume can establish a double symbiosis with nitrogen fixing bacteria and arbuscular mycorrhizal fungi (AMF), which may increase the carbon sink effect of roots. Our aim was to assess whether the association of alfalfa with AMF can avoid, diminish or delay the photosynthetic acclimation observed in previous studies performed with nodulated plants. The results, however, showed that mycorrhizal (M) alfalfa at the end of their vegetative period had lower carbon (C) discrimination than non-mycorrhizal (NM) controls, indicating photosynthetic acclimation under ECO2 in plants associated with AMF. Decreased C discrimination was due to the acclimation of conductance, since the amount of Rubisco and the expression of genes codifying both large and small subunits of Rubisco were similar or slightly higher in M than in NM plants. Moreover, M alfalfa accumulated a greater amount of soluble sugars in leaves than NM plants, thus favoring a down-regulation effect on photosynthetic rates. The enhanced contents of sugars in leaves coincided with a reduced percentage of arbuscules in roots, suggesting decreased sink of carbohydrates from shoots to roots in M plants. The shorter life cycle of alfalfa associated with AMF in comparison with the NM controls may also be related to the accelerated photosynthetic acclimation in M plants. Further research is needed to clarify to what extent this behavior could be extrapolated to alfalfa cultivated in the field and subjected to periodic cutting of shoots under climatic change scenarios.

  4. Transcriptional regulation of host NH₄⁺ transporters and GS/GOGAT pathway in arbuscular mycorrhizal rice roots.

    PubMed

    Pérez-Tienda, Jacob; Corrêa, Ana; Azcón-Aguilar, Concepción; Ferrol, Nuria

    2014-02-01

    Arbuscular mycorrhizal (AM) fungi play a key role in the nutrition of many land plants. AM roots have two pathways for nutrient uptake, directly through the root epidermis and root hairs and via AM fungal hyphae into root cortical cells, where arbuscules or hyphal coils provide symbiotic interfaces. Recent studies demonstrated that the AM symbiosis modifies the expression of plant transporter genes and that NH₄⁺ is the main form of N transported in the symbiosis. The aim of the present work was to get insights into the mycorrhizal N uptake pathway in Oryza sativa by analysing the expression of genes encoding ammonium transporters (AMTs), glutamine synthase (GS) and glutamate synthase (GOGAT) in roots colonized by the AM fungus Rhizophagus irregularis and grown under two N regimes. We found that the AM symbiosis down-regulated OsAMT1;1 and OsAMT1;3 expression at low-N, but not at high-N conditions, and induced, independently of the N status of the plant, a strong up-regulation of OsAMT3;1 expression. The AM-inducible NH₄⁺ transporter OsAMT3;1 belongs to the family 2 of plant AMTs and is phylogenetically related to the AM-inducible AMTs of other plant species. Moreover, for the first time we provide evidence of the specific induction of a GOGAT gene upon colonization with an AM fungus. These data suggest that OsAMT3;1 is likely involved in the mycorrhizal N uptake pathway in rice roots and that OsGOGAT2 plays a role in the assimilation of the NH₄⁺ supplied via the OsAMT3;1 AM-inducible transporter.

  5. Thuja plicata exclusion in ectomycorrhiza-dominated forests: testing the role of inoculum potential of arbuscular mycorrhizal fungi.

    PubMed

    Weber, Adrian; Karst, Justine; Gilbert, Benjamin; Kimmins, J P

    2005-03-01

    The ability of trees dependent on arbuscular mycorrhizal (AM) fungi to establish in ectomycorrhizal forests is unknown. On northern Vancouver Island, Canada, there are sharp boundaries between mixed red cedar (Thuja plicata)-hemlock (Tsuga heterophylla) (CH) stands, and stands of hemlock and amabilis fir (Abies amabilis) (HA). We tested differences in AM colonization of red cedar between ectomycorrhiza-dominated (HA) stands and stands containing red cedar (CH), across a range of light levels. We used a soil bioassay approach to determine whether there was sufficient AM fungal inoculum in the HA tree stands to colonize red cedar seedlings. Seeds of hemlock and red cedar were sown in forest floor samples collected from the two types of forests, and shade treatments ranging from < 1 to 53% of full sunlight were imposed. After 6 months, seedling survival and root and shoot biomass were quantified, and red cedar seedlings were sampled for AM fungal colonization. Hemlock survival and growth did not differ between soil types, suggesting there was no substrate-associated limitation to its establishment in either forest type. Red cedar colonization by AM fungi was significantly correlated with light levels in CH soils but arbuscular mycorrhizas were absent in roots of red cedar seedlings grown in HA soil. Red cedar survival and relative growth rate were significantly greater in the CH than in HA soil; higher growth was due primarily to greater shoot growth in CH soils at high light levels. The low soil inoculum potential for red cedar in ectomycorrhiza-dominated stands may account for the virtual exclusion of red cedar seedlings from these forests.

  6. Mosaic genome of endobacteria in arbuscular mycorrhizal fungi: Transkingdom gene transfer in an ancient mycoplasma-fungus association.

    PubMed

    Torres-Cortés, Gloria; Ghignone, Stefano; Bonfante, Paola; Schüßler, Arthur

    2015-06-23

    For more than 450 million years, arbuscular mycorrhizal fungi (AMF) have formed intimate, mutualistic symbioses with the vast majority of land plants and are major drivers in almost all terrestrial ecosystems. The obligate plant-symbiotic AMF host additional symbionts, so-called Mollicutes-related endobacteria (MRE). To uncover putative functional roles of these widespread but yet enigmatic MRE, we sequenced the genome of DhMRE living in the AMF Dentiscutata heterogama. Multilocus phylogenetic analyses showed that MRE form a previously unidentified lineage sister to the hominis group of Mycoplasma species. DhMRE possesses a strongly reduced metabolic capacity with 55% of the proteins having unknown function, which reflects unique adaptations to an intracellular lifestyle. We found evidence for transkingdom gene transfer between MRE and their AMF host. At least 27 annotated DhMRE proteins show similarities to nuclear-encoded proteins of the AMF Rhizophagus irregularis, which itself lacks MRE. Nuclear-encoded homologs could moreover be identified for another AMF, Gigaspora margarita, and surprisingly, also the non-AMF Mortierella verticillata. Our data indicate a possible origin of the MRE-fungus association in ancestors of the Glomeromycota and Mucoromycotina. The DhMRE genome encodes an arsenal of putative regulatory proteins with eukaryotic-like domains, some of them encoded in putative genomic islands. MRE are highly interesting candidates to study the evolution and interactions between an ancient, obligate endosymbiotic prokaryote with its obligate plant-symbiotic fungal host. Our data moreover may be used for further targeted searches for ancient effector-like proteins that may be key components in the regulation of the arbuscular mycorrhiza symbiosis.

  7. Contrasting impacts of defoliation on root colonization by arbuscular mycorrhizal and dark septate endophytic fungi of Medicago sativa.

    PubMed

    Saravesi, K; Ruotsalainen, A L; Cahill, J F

    2014-05-01

    Individual plants typically interact with multiple mutualists and enemies simultaneously. Plant roots encounter both arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungi, while the leaves are exposed to herbivores. AMF are usually beneficial symbionts, while the functional role of DSE is largely unknown. Leaf herbivory may have a negative effect on root symbiotic fungi due to decreased carbon availability. However, evidence for this is ambiguous and no inoculation-based experiment on joint effects of herbivory on AM and DSE has been done to date. We investigated how artificial defoliation impacts root colonization by AM (Glomus intraradices) and DSE (Phialocephala fortinii) fungi and growth of Medicago sativa host in a factorial laboratory experiment. Defoliation affected fungi differentially, causing a decrease in arbuscular colonization and a slight increase in DSE-type colonization. However, the presence of one fungal species had no effect on colonization by the other or on plant growth. Defoliation reduced plant biomass, with this effect independent of the fungal treatments. Inoculation by either fungal species reduced root/shoot ratios, with this effect independent of the defoliation treatments. These results suggest AM colonization is limited by host carbon availability, while DSE may benefit from root dieback or exudation associated with defoliation. Reductions in root allocation associated with fungal inoculation combined with a lack of effect of fungi on plant biomass suggest DSE and AMF may be functional equivalent to the plant within this study. Combined, our results indicate different controls of colonization, but no apparent functional consequences between AM and DSE association in plant roots in this experimental setup.

  8. Gr and hp-1 tomato mutants unveil unprecedented interactions between arbuscular mycorrhizal symbiosis and fruit ripening

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The roots of plants interact with soil mycorrhizal fungi to facilitate soil nutrient acquisition by the plant and carbon transfer to the fungus. Here we use tomato fruit ripening mutations to demonstrate that this root interaction communicates with and supports genetic mechanisms associated with th...

  9. Arbuscular mycorrhizal symbiosis and osmotic adjustment in response to NaCl stress: a meta-analysis

    PubMed Central

    Augé, Robert M.; Toler, Heather D.; Saxton, Arnold M.

    2014-01-01

    Arbuscular mycorrhizal (AM) symbiosis can enhance plant resistance to NaCl stress in several ways. Two fundamental roles involve osmotic and ionic adjustment. By stimulating accumulation of solutes, the symbiosis can help plants sustain optimal water balance and diminish Na+ toxicity. The size of the AM effect on osmolytes has varied widely and is unpredictable. We conducted a meta-analysis to determine the size of the AM effect on 22 plant solute characteristics after exposure to NaCl and to examine how experimental conditions have influenced the AM effect. Viewed across studies, AM symbioses have had marked effects on plant K+, increasing root and shoot K+ concentrations by an average of 47 and 42%, respectively, and root and shoot K+/Na+ ratios by 47 and 58%, respectively. Among organic solutes, soluble carbohydrates have been most impacted, with AM-induced increases of 28 and 19% in shoots and roots. The symbiosis has had no consistent effect on several characteristics, including root glycine betaine concentration, root or shoot Cl− concentrations, leaf Ψπ, or shoot proline or polyamine concentrations. The AM effect has been very small for shoot Ca++ concentration and root concentrations of Na+, Mg++ and proline. Interpretations about AM-conferred benefits regarding these compounds may be best gauged within the context of the individual studies. Shoot and root K+/Na+ ratios and root proline concentration showed significant between-study heterogeneity, and we examined nine moderator variables to explore what might explain the differences in mycorrhizal effects on these parameters. Moderators with significant impacts included AM taxa, host type, presence or absence of AM growth promotion, stress severity, and whether NaCl constituted part or all of the experimental saline stress treatment. Meta-regression of shoot K+/Na+ ratio showed a positive response to root colonization, and root K+/Na+ ratio a negative response to time of exposure to NaCl. PMID:25368626

  10. Effect of arbuscular mycorrhizal (AM) fungus and plant growth promoting rhizomicroorganisms (PGPR's) on medicinal plant Solanum viarum seedlings.

    PubMed

    Hemashenpagam, N; Selvaraj, T

    2011-09-01

    A green house nursery study was conducted to assess the interaction between arbuscular mycorrhizal (AM) fungus, Glomus aggregatum and some plant growth promoting rhizomicrooganisms (PGPR's), Bacillus coagulans and Trichoderma harzianum, in soil and their consequent effect on growth, nutrition and content of secondary metabolities of Solanum viarum seedlings. Triple inoculation of G. aggregatum+B. coagulans+T. harzainum with Solanum viarum in a green house nursery study resulted in maximum plant biomass (plant height 105 cm and plant dry weight 12.17 g), P, Fe, Zn, Cu and Mn and secondary metabolities [total phenols (129.6 microg g(-1) f.wt.), orthodihydroxy phenols (90.6 microg g(-1) f.wt.), flavonoids (3.94 microg g(-1) f.wt.), alkaloids (5.05 microg g(-1) f.wt.), saponins (5.05 microg g(-1) f.wt.) and tannins (0.324 microg g(-1) f.wt.)] of S. viarum seedlings. The mycorrhizal root colonization and spore numbers in the root zone soil of the inoculated plants increased. The enzyme activity namely acid phosphatase (53.44 microg PNP g(-1) soil), alkaline phosphatase (40.95 microg PNP g(-1) soil) and dehydrogenase (475.5 microg PNP g(-1) soil) and total population of B. coagulans (12.5x10(4) g(-1)) and T. harzianum (12.4 x 10(4) g(-1)), in the root zone soil was found high in the triple inoculation with G. aggregatum+B. coagulans+T. harzianum that proved to be the best microbial consortium.

  11. [Effects of Arbuscular Mycorrhizal Fungi on the Growth and Ce Uptake of Maize Grown in Ce-contaminated Soils].

    PubMed

    Wang, Fang; Guo, Weil; Ma, Peng-kun; Pan, Liang; Zhang, Jun

    2016-01-15

    A greenhouse pot experiment was conducted to investigate the effects of arbuscular mycorrhizal (AM) fungi Glomus aggregatum (GA) and Funneliformis mosseae (FM) on AM colonization rate, biomass, nutrient uptake, C: N: P stoichiometric and Ce uptake and transport by maize (Zea mays L.) grown in soils with different levels of Ce-contaminated (100, 500 and 1000 mg x kg(-1)). The aim was to provide basic data and technical support for the treatment of soils contaminated by rare earth elements. The results indicated that symbiotic associations were successfully established between the two isolates and maize, and the average AM colonization rate ranged from 7. 12% to 74.47%. The increasing concentration of Ce in soils significantly decreased the mycorrhizal colonization rate, biomass, nutrition contents and transport rate of Ce from root to shoot of maize, and significantly increased C: P and N: P ratios and Ce contents in shoot and root of maize. Both AM fungi inoculations promoted the growth of maize, but the promoting role of FM was more significant than that of GA in severe Ce-contaminated soils. There were no significant differences in the growth of maize between two AM fungi in mild and moderate Ce-contaminated soils. Inoculation with AM fungi significantly improved nutritional status of maize by increasing nutrient uptake and decreasing C: N: P ratios. GA was more efficient than FM in enhancing nutrient uptake in mild and moderate Ce-contaminated soils, while FM was more efficient in severe Ce-contaminated soils. Moreover, inoculation with AM fungi significantly increased Ce contents of shoot and root in mild Ce-contaminated soils, but had no significant effect on Ce contents of maize in moderate and severe Ce-contaminated soils, and promoted the transport of Ce from root to shoot. The experiment demonstrates that AM fungi can alleviate toxic effects of Ce on plants and have a potential role in the phytoremediation of soils contaminated by rare earth elements.

  12. The growth and phosphorus acquisition of invasive plants Rudbeckia laciniata and Solidago gigantea are enhanced by arbuscular mycorrhizal fungi.

    PubMed

    Majewska, Marta L; Rola, Kaja; Zubek, Szymon

    2017-02-01

    While a number of recent studies have revealed that arbuscular mycorrhizal fungi (AMF) can mediate invasive plant success, the influence of these symbionts on the most successful and high-impact invaders is largely unexplored. Two perennial herbs of this category of invasive plants, Rudbeckia laciniata and Solidago gigantea (Asteraceae), were thus tested in a pot experiment to determine whether AMF influence their growth, the concentration of phosphorus in biomass, and photosynthesis. The following treatments, including three common AMF species, were prepared on soils representative of two habitats that are frequently invaded by both plants, namely fallow and river valley: (1) control-soil without AMF, (2) Rhizophagus irregularis, (3) Funneliformis mosseae, and (4) Claroideoglomus claroideum. The invaders were strongly dependent on AMF for their growth. The mycorrhizal dependency of R. laciniata was 88 and 63 % and of S. gigantea 90 and 82 % for valley and fallow soils, respectively. The fungi also increased P concentration in their biomass. However, we found different effects of the fungal species in the stimulation of plant growth and P acquisition, with R. irregularis and C. claroideum being the most and least effective symbionts, respectively. None of AMF species had an impact on the photosynthetic performance indexes of both plants. Our findings indicate that AMF have a direct effect on the early stages of R. laciniata and S. gigantea growth. The magnitude of the response of both plant species to AMF was dependent on the fungal and soil identities. Therefore, the presence of particular AMF species in a site may determine the success of their invasion.

  13. Spore population, colonization, species diversity and factors influencing the association of arbuscular mycorrhizal fungi with litchi trees in India.

    PubMed

    Kumar, Vinod; Kumar, Rajesh; Kumar, Ajit; Anal, Dubedi

    2016-01-01

    Abundance and diversity of arbuscular mycorrhizal fungi (AMF) in association with litchi (Litchi chinensis Sonn.) trees were studied during 2012-2013, where orchard soil had high pH (7.42-9.53) and salinity (0.07- 0.39 dSm(-1)). A total of 105 rhizospheric soil and root samples were collected considering variables like location, age of tree, cultivar and production management. Results showed that spore count was in the range of 1-22 g(-1) soil. All the examined root segments had colonization of AMF, which ranged between 3.3 to 90.0%. AMF community comprised of Glomus mosseae, G. intaradices, G. constricta, G. coronatum, G. fasciculatum, G. albidum, G. hoi, G. multicauli, Acaulospora scrobiculata, A. laevis, Rhizophagus litchi and Entrophosphora infrequens. Higher spore density and AMF colonization were observed at medium level (13-28 kg ha(-1)) of available phosphorus that decreased ('r' = -0.21 for spore density, -0.48 for root colonization) with increasing soil phosphorus. While nitrogen did not influence the AMF association, a weak negative linear relationship with AMF colonization ('r' = -0.30) was apparent in the medium level (112-200 kg ha(-1)) of potash. Micronutrients (Zn, Fe, Cu, Mn and B) did not affect spore density (zero or a very weak linear correlation) but influenced root colonization ('r' = -0.53 to -0.44), the effect being more prominent above critical limits. Nutritionally sufficient, irrigated litchi orchards had greater spore count (46% samples having 5-22 spores g(-1) soil) and colonization (> 50% in 37.4% roots examined) than nutrient deficient, non-irrigated orchards, indicating essentiality of a threshold nutrients and moisture regime for the association. AMF symbiosis was influenced by cultivar (greater in 'China'), but tree age was not correlated to mycorrhizal association. A consortium of native species coupled with the understanding of nutrient effects on AMF would be useful for field application in litchi.

  14. Diversity of Arbuscular Mycorrhizal Fungi Associated with a Sb Accumulator Plant, Ramie (Boehmeria nivea), in an Active Sb Mining.

    PubMed

    Wei, Yuan; Chen, ZhiPeng; Wu, FengChang; Li, JiNing; ShangGuan, YuXian; Li, FaSheng; Zeng, Qing Ru; Hou, Hong

    2015-08-01

    Arbuscular mycorrhizal fungi (AMF) have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the symbiosis of AMF associated with an antimony (Sb) accumulator plant under natural conditions. Therefore, the objective of this study was to investigate the colonization and molecular diversity of AMF associated with the Sb accumulator ramie (Boehmeria nivea) growing in Sb-contaminated soils. Four Sb mine spoils and one adjacent reference area were selected from Xikuangshan in southern China. PCR-DGGE was used to analyze the AMF community composition in ramie roots. Morphological identification was also used to analyze the species in the rhizosphere soil of ramie. Results obtained showed that mycorrhizal symbiosis was established successfully even in the most heavily polluted sites. From the unpolluted site Ref to the highest polluted site T4, the spore numbers and AMF diversity increased at first and then decreased. Colonization increased consistently with the increasing Sb concentrations in the soil. A total of 14 species were identified by morphological analysis. From the total number of species, 4 (29%) belonged to Glomus, 2 (14%) belonged to Acaulospora, 2 (14%) belonged to Funneliformis, 1 (7%) belonged to Claroideoglomus, 1 (7%) belonged to Gigaspora, 1 (7%) belonged to Paraglomus, 1 (7%) belonging to Rhizophagus, 1 (7%) belonging to Sclervocystis, and 1 (7%) belonged to Scutellospora. Some AMF sequences were present even in the most polluted site. Morphological identification and phylogenetic analysis both revealed that most species were affiliated withGlomus, suggesting that Glomus was the dominant genus in this AMF community. This study demonstrated that ramie associated with AMF may have great potential for remediation of Sb-contaminated soils.

  15. Colonization of olive trees (Olea europaea L.) with the arbuscular mycorrhizal fungus Glomus sp. modified the glycolipids biosynthesis and resulted in accumulation of unsaturated fatty acids.

    PubMed

    Mechri, Beligh; Attia, Faouzi; Tekaya, Meriem; Cheheb, Hechmi; Hammami, Mohamed

    2014-09-01

    The influence of arbuscular mycorrhizal (AM) fungi colonization on photosynthesis, mineral nutrition, the amount of phospholipids and glycolipids in the leaves of olive (Olea europaea L.) trees was investigated. After six months of growth, the rate of photosynthesis, carboxylation efficiency, transpiration and stomatal conductance in mycorrhizal (M) plants was significantly higher than that of non-mycorrhizal (NM) plants. The inoculation treatment increased the foliar P and Mg but not N. The amount of glycolipids in the leaves of M plants was significantly higher than that of NM plants. However, the amount of phospholipids in the leaves of M plants was not significantly different to that in the leaves of NM plants. Also, we observed a significant increase in the level of α-linolenic acid (C18:3ω3) in glycolipids of M plants. This work supports the view that increased glycolipids level in the leaves of M plants could be involved, at least in part, in the beneficial effects of mycorrhizal colonization on photosynthesis performance of olive trees. To our knowledge, this is the first report on the effect of AM fungi on the amount of glycolipids in the leaves of mycorrhizal plants.

  16. [Mycotrophic capacity and efficiency of microbial consortia of arbuscular mycorrhizal fungi native of soils from Buenos Aires province under contrasting management].

    PubMed

    Thougnon Islas, Andrea J; Eyherabide, Mercedes; Echeverría, Hernán E; Sainz Rozas, Hernán R; Covacevich, Fernanda

    2014-01-01

    We characterized the infective and sporulation capacities of microbial consortia of arbuscular mycorrhizal fungi (AMF) native of Buenos Aires province (Argentina) and determined if some soil characteristics and mycorrhizal parameters could allow to select potentially beneficial inocula. Soil samples were selected from seven locations in Buenos Aires province all under agricultural (A) and pristine (P) conditions. The AMF were multiplied and mycorrhizal root colonization of trap plants was observed at 10 weeks of growth. Spore number in field was low; however, after multiplication spore density accounted for 80-1175 spores per 100g of soil. The principal component analysis showed that the P and Fe soil contents are the main modulators of infectivity and sporulation capacity. The mycorrhizal potential was determined in three locations, being high in Pristine Lobería and Agricultural Trenque Lauquen and low in Junín. Agricultural Lobería (AL) and Pristine Lobería (PL) inocula were selected and their efficiency was evaluated under controlled conditions. Even though shoot dry matter increases after inoculation was not significant (p>0.05) mycorrhizal response was greater than 40% for tomato and 25% for corn, particularly after inoculation with inocula from the agricultural management. These results could be associated to the incipient development of mycorrhizae in both species. Additional research should be conducted to further develop our findings in order to determine the factors involved in the selection of efficient inocula.

  17. Effects of arbuscular mycorrhizal fungi on the growth, photosynthesis and photosynthetic pigments of Leymus chinensis seedlings under salt-alkali stress and nitrogen deposition.

    PubMed

    Lin, Jixiang; Wang, Yingnan; Sun, Shengnan; Mu, Chunsheng; Yan, Xiufeng

    2017-01-15

    Leymus chinensis is the most promising grass species for salt-alkaline grassland restoration in northern China. However, little information exists concerning the role of arbuscular mycorrhizal (AM) symbiosis in the adaptation of seedlings to salt-alkali stress, particularly under increased nitrogen deposition, which has become a major environmental problem throughout the world. In this study, Leymus chinensis seedlings were cultivated in soil with 0, 100 and 200mM NaCl/NaHCO3 under two forms of nitrogen (10mM NH4NO3 or NH4Cl: NH4NO3=3:1), and the root colonization, growth and photosynthetic characteristics of the seedlings were measured. The results showed that the colonization rate and intensity decreased with increasing salt-alkali stress and were much lower under alkali stress. The nitrogen treatments also decreased the colonization, particularly under the NH4(+)-N treatment. Compared with the non-mycorrhizal controls, mycorrhizal seedlings generally presented higher plant biomass, photosynthetic parameters and contents of photosynthetic pigments under stresses, and the inhibitive effects of alkali stress were substantially stronger. In addition, both nitrogen forms decreased the physiological indexes compared with those of the AM seedlings. Our results suggest that salt stress and alkali stress are significantly different and that the salt-alkali tolerance of Leymus chinensis seedlings could be enhanced by associations with arbuscular mycorrhizal fungi, in which would yield better plant growth and photosynthesis. Excessive nitrogen in the soil affects mycorrhizal colonization and thereby inhibits the growth and photosynthetic ability of the seedlings.

  18. Specific interactions between arbuscular mycorrhizal fungi and plant growth-promoting bacteria--as revealed by different combinations

    SciTech Connect

    Jaderlund, Lotta; Arthurson, Veronica; Granhall, Ulf; Jansson, Janet K.

    2008-05-15

    The interactions between two plant growth promoting rhizobacteria (PGPR), Pseudomonas fluorescens SBW25 and Paenibacillus brasilensis PB177, two arbuscular mycorrhizal (AM) fungi (Glomus mosseae and G. intraradices) and one pathogenic fungus (Microdochium nivale) were investigated on winter wheat (Triticum aestivum cultivar Tarso) in a greenhouse trial. PB177, but not SBW25, had strong inhibitory effects on M. nivale in dual culture plate assays. The results from the greenhouse experiment show very specific interactions; e.g. the two AM fungi react differently when interacting with the same bacteria on plants. G. intraradices (single inoculation or together with SBW25) increased plant dry weight on M. nivale infested plants, suggesting that the pathogenic fungus is counteracted by G. intraradices, but PB177 inhibited this positive effect. This is an example of two completely different reactions between the same AM fungus and two species of bacteria, previously known to enhance plant growth and inhibit pathogens. When searching for plant growth promoting microorganisms it is therefore important to test for the most suitable combination of plant, bacteria and fungi in order to get satisfactory plant growth benefits.

  19. Impact of weed control on arbuscular mycorrhizal fungi in a tropical agroecosystem: a long-term experiment.

    PubMed

    Ramos-Zapata, José A; Marrufo-Zapata, Denis; Guadarrama, Patricia; Carrillo-Sánchez, Lilia; Hernández-Cuevas, Laura; Caamal-Maldonado, Arturo

    2012-11-01

    Cover crop species represent an affordable and effective weed control method in agroecosystems; nonetheless, the effect of its use on arbuscular mycorrhizal fungi (AMF) has been scantily studied. The goal of this study was to determine root colonization levels and AMF species richness in the rhizosphere of maize plants and weed species growing under different cover crop and weed control regimes in a long-term experiment. The treatment levels used were (1) cover of Mucuna deeringian (Muc), (2) "mulch" of Leucaena leucocephala (Leu), (3) "mulch" of Lysiloma latisiliquum (Lys), (4) herbicide (Her), (5) manual weeding (CD), (6) no weeding (SD), and (7) no maize and no weeding (B). A total of 18 species of AMF belonging to eight genera (Acaulospora, Ambispora, Claroideoglomus, Funneliformis, Glomus, Rhizophagus, Sclerocystis, and Scutellospora) were identified from trap cultures. Muc and Lys treatments had a positive impact on AMF species richness (11 and seven species, respectively), while Leu and B treatments on the other hand gave the lowest richness values (six species each). AMF colonization levels in roots of maize and weeds differed significantly between treatment levels. Overall, the use of cover crop species had a positive impact on AMF species richness as well as on the percentage of root colonized by AMF. These findings have important implications for the management of traditional agroecosystems and show that the use of cover crop species for weed control can result in a more diverse AMF community which should potentially increase crop production in the long run.

  20. Alleviation of cadmium stress in Solanum lycopersicum L. by arbuscular mycorrhizal fungi via induction of acquired systemic tolerance

    PubMed Central

    Hashem, Abeer; Abd_Allah, E.F.; Alqarawi, A.A.; Al Huqail, Asma A.; Egamberdieva, D.; Wirth, S.

    2015-01-01

    Experiments were conducted to evaluate cadmium (Cd) stress-induced changes in growth, antioxidants and lipid composition of Solanum lycopersicum with and without arbuscular mycorrhizal fungi (AMF). Cadmium stress (50 μM) caused significant changes in the growth and physio-biochemical attributes studied. AMF mitigated the deleterious impact of Cd on the parameters studied. Cadmium stress increased malonaldehyde and hydrogen peroxide production but AMF reduced these parameters by mitigating oxidative stress. The activity of antioxidant enzymes enhanced under Cd treatment and AMF inoculation further enhanced their activity, thus strengthening the plant’s defense system. Proline and phenol content increased in Cd-treated as well as AMF-inoculated plants providing efficient protection against Cd stress. Cadmium treatment resulted in great alterations in the main lipid classes leading to a marked change in their composition. Cadmium stress caused a significant reduction in polyunsaturated fatty acids resulting in enhanced membrane leakage. The present study supports the use of AMF as a biological means to ameliorate Cd stress-induced changes in tomato. PMID:26981010

  1. Effect of different arbuscular mycorrhizal fungi on growth and physiology of maize at ambient and low temperature regimes.

    PubMed

    Chen, Xiaoying; Song, Fengbin; Liu, Fulai; Tian, Chunjie; Liu, Shengqun; Xu, Hongwen; Zhu, Xiancan

    2014-01-01

    The effect of four different arbuscular mycorrhizal fungi (AMF) on the growth and lipid peroxidation, soluble sugar, proline contents, and antioxidant enzymes activities of Zea mays L. was studied in pot culture subjected to two temperature regimes. Maize plants were grown in pots filled with a mixture of sandy and black soil for 5 weeks, and then half of the plants were exposed to low temperature for 1 week while the rest of the plants were grown under ambient temperature and severed as control. Different AMF resulted in different root colonization and low temperature significantly decreased AM colonization. Low temperature remarkably decreased plant height and total dry weight but increased root dry weight and root-shoot ratio. The AM plants had higher proline content compared with the non-AM plants. The maize plants inoculated with Glomus etunicatum and G. intraradices had higher malondialdehyde and soluble sugar contents under low temperature condition. The activities of catalase (CAT) and peroxidase of AM inoculated maize were higher than those of non-AM ones. Low temperature noticeably decreased the activities of CAT. The results suggest that low temperature adversely affects maize physiology and AM symbiosis can improve maize seedlings tolerance to low temperature stress.

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

    PubMed Central

    Lu, Fun-Chi; 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. PMID:26421239

  3. The interaction with arbuscular mycorrhizal fungi or Trichoderma harzianum alters the shoot hormonal profile in melon plants.

    PubMed

    Martínez-Medina, Ainhoa; Roldán, Antonio; Albacete, Alfonso; Pascual, Jose A

    2011-02-01

    Arbuscular mycorrhizal fungi (AMF) and Trichoderma harzianum are known to affect plant growth and disease resistance through interaction with phytohormone synthesis or transport in the plant. Cross-talk between these microorganisms and their host plants normally occurs in nature and may affect plant resistance. Simultaneous quantification in the shoots of melon plants revealed significant changes in the levels of several hormones in response to inoculation with T. harzianum and two different AMF (Glomus intraradices and Glomus mosseae). Analysis of zeatin (Ze), indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylic acid (ACC), salicylic acid (SA), jasmonic acid (JA) and abscisic acid (ABA) in the shoot showed common and divergent responses of melon plants to G. intraradices and G. mosseae. T. harzianum effected systemic increases in Ze, IAA, ACC, SA, JA and ABA. The interaction of T. harzianum and the AMF with the plant produced a characteristic hormonal profile, which differed from that produced by inoculation with each microorganism singly, suggesting an attenuation of the plant response, related to the hormones SA, JA and ethylene. These results are discussed in relation to their involvement in biomass allocation and basal resistance against Fusarium wilt.

  4. Slope aspect influences arbuscular mycorrhizal fungus communities in arid ecosystems of the Daqingshan Mountains, Inner Mongolia, North China.

    PubMed

    Liu, Min; Zheng, Rong; Bai, Shulan; Bai, Yv E; Wang, Jugang

    2017-04-01

    Arbuscular mycorrhizal (AM) symbiosis plays an important role in ecosystem functioning, particularly in fragile environments. Little is known, however, about how AM fungus community composition responds to slope aspect. Our objective was to compare the AM fungus communities between sunny and shady slopes and to detect factors that influenced the distributions of AM fungi in arid ecosystems of the Daqingshan Mountains, Inner Mongolia, North China. AM fungus communities were evaluated based on small subunit ribosomal RNA genes (SSUs) using Illumina MiSeq sequencing. AM fungus community composition differed significantly between slope aspects, and sunny slopes had significantly higher AM fungus diversity and richness as well as spore density, total root colonization, arbuscule abundance, vesicle abundance, and hyphal colonization than shady slopes. Structural equation modeling (SEM) illustrated that the effects of slope aspect on AM fungus richness likely were mediated by available phosphorus, soil organic carbon, plant cover, and plant diversity. Available phosphorus was the principal factor that influenced AM fungus species richness, and soil organic carbon was the principal factor influencing spore density and total root colonization, suggesting that these factors especially might be responsible for differences between the AM fungus communities of different slope aspects. These findings elucidate the influence of slope aspect on AM fungus communities and may inform use of AM fungi in protection and restoration of vegetation with different slope aspects in arid ecosystems.

  5. Land-use intensity and host plant identity interactively shape communities of arbuscular mycorrhizal fungi in roots of grassland plants.

    PubMed

    Vályi, Kriszta; Rillig, Matthias C; Hempel, Stefan

    2015-03-01

    We studied the effect of host plant identity and land-use intensity (LUI) on arbuscular mycorrhizal fungi (AMF, Glomeromycota) communities in roots of grassland plants. These are relevant factors for intraradical AMF communities in temperate grasslands, which are habitats where AMF are present in high abundance and diversity. In order to focus on fungi that directly interact with the plant at the time, we investigated root-colonizing communities. Our study sites represent an LUI gradient with different combinations of grazing, mowing, and fertilization. We used massively parallel multitag pyrosequencing to investigate AMF communities in a large number of root samples, while being able to track the identity of the host. We showed that host plants significantly differed in AMF community composition, while land use modified this effect in a plant species-specific manner. Communities in medium and low land-use sites were subsets of high land-use communities, suggesting a differential effect of land use on the dispersal of AMF species with different abundances and competitive abilities. We demonstrate that in these grasslands, there is a small group of highly abundant, generalist fungi which represent the dominating species in the AMF community.

  6. Effect of biosolids-derived triclosan and triclocarban on the colonization of plant roots by arbuscular mycorrhizal fungi.

    PubMed

    Prosser, R S; Lissemore, L; Shahmohamadloo, R S; Sibley, P K

    2015-03-01

    Arbuscular mycorrhizal fungi (AMF) form a symbiotic relationship with the majority of crop plants. AMF provide plants with nutrients (e.g., P), modulate the effect of metal and pathogen exposure, and increase tolerance to moisture stress. The benefits of AMF to plant growth make them important to the development of sustainable agriculture. The land application of biosolids is becoming an increasingly common practice in sustainable agriculture, as a source of nutrients. However, biosolids have been found to contain numerous pharmaceutical and personal care products including antimicrobial chemicals such as triclosan and triclocarban. The potential risks that these two compounds may pose to plant-AMF interactions are poorly understood. The current study investigated whether biosolids-derived triclosan and triclocarban affect the colonization of the roots of lettuce and corn plants by AMF. Plants were grown in soil amended with biosolids that contained increasing concentrations of triclosan (0 to 307 μg/g dw) or triclocarban (0 to 304 μg/g dw). A relationship between the concentration of triclosan or triclocarban and colonization of plants roots by AMF was not observed. The presence of biosolids did not have a significant (p>0.05) effect on percent colonization of corn roots but had a significant, positive effect (p<0.05) on lettuce roots. Biosolids-derived triclosan and triclocarban did not inhibit the colonization of crop plant roots by AMF.

  7. Arbuscular mycorrhizal fungi in chronically petroleum-contaminated soils in Mexico and the effects of petroleum hydrocarbons on spore germination.

    PubMed

    Franco-Ramírez, Alicia; Ferrera-Cerrato, Ronald; Varela-Fregoso, Lucía; Pérez-Moreno, Jesús; Alarcón, Alejandro

    2007-10-01

    Arbuscular mycorrhizal fungi (AMF) have been hypothesized to enhance plant adaptation and growth in petroleum-contaminated soils. Nevertheless, neither AMF-biodiversity under chronically petroleum-contaminated soils nor spore germination response to petroleum hydrocarbons has been well studied. Chronically petroleum-contaminated rhizosphere soil and roots from Echinochloa polystachya, Citrus aurantifolia and C. aurantium were collected from Activo Cinco Presidentes, Tabasco, Mexico. Root colonization and spore abundance were evaluated. Additionally, rhizosphere soil samples were propagated using Sorghum vulgare L. as a plant trap under greenhouse conditions; subsequently, AMF-spores were identified. AMF-colonization ranged from 63 to 77% while spore number ranged from 715 to 912 in 100 g soil, suggesting that AMF tolerate the presence of petroleum hydrocarbons in the rhizosphere. From grass species, four AMF-morphospecies were identified: Glomus ambisporum, G. sinuosum (previously described as Sclerocystis sinuosum), Acaulospora laevis, and Ambispora gerdermanni. From citrus trees, four AMF-species were also identified: Scutellospora heterogama, G. ambisporum, Acaulospora scrobiculata, and G. citricola. In a second study, it was observed that spore germination and hyphal length of G. mosseae, G. ambisporum, and S. heterogama were significantly reduced by either volatile compounds of crude oil or increased concentrations of benzo[a ]pyrene or phenanthrene in water-agar.

  8. Arbuscular mycorrhizal fungi associated with vegetation and soil parameters under rest grazing management in a desert steppe ecosystem.

    PubMed

    Bai, Gegenbaoleer; Bao, Yuying; Du, Guoxin; Qi, Yunlong

    2013-05-01

    The impact of rest grazing on arbuscular mycorrhizal fungi (AMF) and the interactions of AMF with vegetation and soil parameters under rest grazing condition were investigated between spring and late summer in a desert steppe ecosystem with different grazing managements (rest grazing with different lengths of resting period, banned or continuous grazing) in Inner Mongolia, China. AMF diversity and colonization, vegetation biomass, soil properties and soil phosphatase activity were examined. In rest grazing areas of 60 days, AMF spore number and diversity index at a 0-10 cm soil depth as well as vesicular and hyphal colonization rates were higher compared with other grazing treatments. In addition, soil organic matter and total N contents were highest and soil alkaline phosphatase was most active under 60-day rest grazing. In August and September, these areas also had the highest amount of aboveground vegetation. The results indicated that resting grazing for an appropriate period of time in spring has a positive effect on AMF sporulation, colonization and diversity, and that under rest grazing conditions, AMF parameters are positively correlated with some soil characteristics.

  9. Foliar spray with vermiwash modifies the Arbuscular mycorrhizal dependency and nutrient stoichiometry of Bhut Jolokia (Capsicum assamicum).

    PubMed

    Khan, Mohammad Haneef; Meghvansi, Mukesh K; Gupta, Rajeev; Veer, Vijay; Singh, Lokendra; Kalita, Mohan C

    2014-01-01

    Vermiwash (VW), a liquid extract obtained from vermicomposting beds, is used as an organic fertilizer for crop plants. The current study investigated the effect of a vermiwash foliar spray on the response of bhut jolokia (Capsicum assamicum) exposed to two different arbuscular mycorrhizal fungi (AMF: Rhizophagus irregularis, RI and G. mosseae, GM) in acidic soil under naturally ventilated greenhouse conditions. The VW spray significantly influenced the growth of plants receiving the dual treatment of AMF+VW. Plant growth was more prominent in the GM+VW treatment group than that in the RI+VW treatment group. The plant-AMF interactions in relation to growth and nutrient requirements were also significantly influenced by the application of VW. Interestingly, the VW treatment appeared to contribute more N to plants when compared to that under the AMF treatment, which led to changes in the C:N:P stoichiometry in plant shoots. Furthermore, the increased potassium dependency, as observed in the case of the dual treatments, suggests the significance of such treatments for improving crop conditions under salt stress. Overall, our study shows that the VW foliar spray modifies the response of a crop to inoculations of different AMF with regard to growth and nutrient utilization, which has implications for the selection of an efficient combination of nutrient source for improving crop growth.

  10. Local adaptation to soil hypoxia determines the structure of an arbuscular mycorrhizal fungal community in roots from natural CO₂ springs.

    PubMed

    Maček, Irena; Dumbrell, Alex J; Nelson, Michaela; Fitter, Alastair H; Vodnik, Dominik; Helgason, Thorunn

    2011-07-01

    The processes responsible for producing and maintaining the diversity of natural arbuscular mycorrhizal (AM) fungal communities remain largely unknown. We used natural CO(2) springs (mofettes), which create hypoxic soil environments, to determine whether a long-term, directional, abiotic selection pressure could change AM fungal community structure and drive the selection of particular AM fungal phylotypes. We explored whether those phylotypes that appear exclusively in hypoxic soils are local specialists or widespread generalists able to tolerate a range of soil conditions. AM fungal community composition was characterized by cloning, restriction fragment length polymorphism typing, and the sequencing of small subunit rRNA genes from roots of four plant species growing at high (hypoxic) and low (control) geological CO(2) exposure. We found significant levels of AM fungal community turnover (β diversity) between soil types and the numerical dominance of two AM fungal phylotypes in hypoxic soils. Our results strongly suggest that direct environmental selection acting on AM fungi is a major factor regulating AM fungal communities and their phylogeographic patterns. Consequently, some AM fungi are more strongly associated with local variations in the soil environment than with their host plant's distribution.

  11. Contrasting arbuscular mycorrhizal responses of vascular and non-vascular plants to a simulated Palaeozoic CO₂ decline.

    PubMed

    Field, Katie J; Cameron, Duncan D; Leake, Jonathan R; Tille, Stefanie; Bidartondo, Martin I; Beerling, David J

    2012-05-15

    The arbuscular mycorrhizal (AM) fungal symbiosis is widely hypothesized to have promoted the evolution of land plants from rootless gametophytes to rooted sporophytes during the mid-Palaeozoic (480-360 Myr, ago), at a time coincident with a 90% fall in the atmospheric CO(2) concentration ([CO(2)](a)). Here we show using standardized dual isotopic tracers ((14)C and (33)P) that AM symbiosis efficiency (defined as plant P gain per unit of C invested into fungi) of liverwort gametophytes declines, but increases in the sporophytes of vascular plants (ferns and angiosperms), at 440 p.p.m. compared with 1,500 p.p.m. [CO(2)](a). These contrasting responses are associated with larger AM hyphal networks, and structural advances in vascular plant water-conducting systems, promoting P transport that enhances AM efficiency at 440 p.p.m. [CO(2)](a). Our results suggest that non-vascular land plants not only faced intense competition for light, as vascular land floras grew taller in the Palaeozoic, but also markedly reduced efficiency and total capture of P as [CO(2)](a) fell.

  12. Diversity of root-associated arbuscular mycorrhizal fungal communities in a rubber tree plantation chronosequence in Northeast Thailand.

    PubMed

    Herrmann, Laetitia; Lesueur, Didier; Bräu, Lambert; Davison, John; Jairus, Teele; Robain, Henri; Robin, Agnès; Vasar, Martti; Wiriyakitnateekul, Wanpen; Öpik, Maarja

    2016-11-01

    Rubber tree (Hevea brasiliensis) is of major economic importance in Southeast Asia and for small land holders in Thailand in particular. Due to the high value of latex, plantations are expanding into unsuitable areas, such as the northeast province of Thailand where soil fertility is very low and therefore appropriate management practices are of primary importance. Arbuscular mycorrhizal fungi (AMF) contribute to plant growth through a range of mechanisms and could play a key role in a more sustainable management of the rubber plantations. We described the diversity of AMF associated with rubber tree roots in Northeast Thailand in relation to tree age and soil parameters along a chronosequence of rubber tree plantations. Cassava fields were included for comparison. Rubber tree and cassava roots harbored high diversity of AMF (111 Virtual Taxa, VT), including 20 novel VT. AMF VT richness per sample was consistently high (per site mean 16 to 21 VT per sample) along the chronosequence and was not related to soil properties. The composition of AMF communities differed between cassava and rubber tree plantations and was influenced by soil texture and nutrient content (sand, K, P, Ca). AMF community composition gradually shifted with the age of the trees. Our results suggest that the high diversity of AMF in this region is potentially significant for maintaining high functionality of AMF communities.

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

    PubMed Central

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

    2016-01-01

    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. PMID:26892768

  14. Characterization of arbuscular mycorrhizal fungus communities of Aquilaria crassna and Tectona grandis roots and soils in Thailand plantations.

    PubMed

    Chaiyasen, Amornrat; Young, J Peter W; Teaumroong, Neung; Gavinlertvatana, Paiboolya; Lumyong, Saisamorn

    2014-01-01

    Aquilaria crassna Pierre ex Lec. and Tectona grandis Linn.f. are sources of resin-suffused agarwood and teak timber, respectively. This study investigated arbuscular mycorrhizal (AM) fungus community structure in roots and rhizosphere soils of A. crassna and T. grandis from plantations in Thailand to understand whether AM fungal communities present in roots and rhizosphere soils vary with host plant species and study sites. Terminal restriction fragment length polymorphism complemented with clone libraries revealed that AM fungal community composition in A. crassna and T. grandis were similar. A total of 38 distinct terminal restriction fragments (TRFs) were found, 31 of which were shared between A. crassna and T. grandis. AM fungal communities in T. grandis samples from different sites were similar, as were those in A. crassna. The estimated average minimum numbers of AM fungal taxa per sample in roots and soils of T. grandis were at least 1.89 vs. 2.55, respectively, and those of A. crassna were 2.85 vs. 2.33 respectively. The TRFs were attributed to Claroideoglomeraceae, Diversisporaceae, Gigasporaceae and Glomeraceae. The Glomeraceae were found to be common in all study sites. Specific AM taxa in roots and soils of T. grandis and A. crassna were not affected by host plant species and sample source (root vs. soil) but affected by collecting site. Future inoculum production and utilization efforts can be directed toward the identified symbiotic associates of these valuable tree species to enhance reforestation efforts.

  15. Characterization of Arbuscular Mycorrhizal Fungus Communities of Aquilaria crassna and Tectona grandis Roots and Soils in Thailand Plantations

    PubMed Central

    Chaiyasen, Amornrat; Young, J. Peter W.; Teaumroong, Neung; Gavinlertvatana, Paiboolya; Lumyong, Saisamorn

    2014-01-01

    Aquilaria crassna Pierre ex Lec. and Tectona grandis Linn.f. are sources of resin-suffused agarwood and teak timber, respectively. This study investigated arbuscular mycorrhizal (AM) fungus community structure in roots and rhizosphere soils of A. crassna and T. grandis from plantations in Thailand to understand whether AM fungal communities present in roots and rhizosphere soils vary with host plant species and study sites. Terminal restriction fragment length polymorphism complemented with clone libraries revealed that AM fungal community composition in A. crassna and T. grandis were similar. A total of 38 distinct terminal restriction fragments (TRFs) were found, 31 of which were shared between A. crassna and T. grandis. AM fungal communities in T. grandis samples from different sites were similar, as were those in A. crassna. The estimated average minimum numbers of AM fungal taxa per sample in roots and soils of T. grandis were at least 1.89 vs. 2.55, respectively, and those of A. crassna were 2.85 vs. 2.33 respectively. The TRFs were attributed to Claroideoglomeraceae, Diversisporaceae, Gigasporaceae and Glomeraceae. The Glomeraceae were found to be common in all study sites. Specific AM taxa in roots and soils of T. grandis and A. crassna were not affected by host plant species and sample source (root vs. soil) but affected by collecting site. Future inoculum production and utilization efforts can be directed toward the identified symbiotic associates of these valuable tree species to enhance reforestation efforts. PMID:25397675

  16. Germinating spore exudates from arbuscular mycorrhizal fungi: molecular and developmental responses in plants and their regulation by ethylene.

    PubMed

    Mukherjee, Arijit; Ané, Jean-Michel

    2011-02-01

    Arbuscular mycorrhizal (AM) fungi stimulate root development and induce expression of mycorrhization-specific genes in both eudicots and monocots. Diffusible factors released by AM fungi have been shown to elicit similar responses in Medicago truncatula. Colonization of roots by AM fungi is inhibited by ethylene. We compared the effects of germinating spore exudates (GSE) from Glomus intraradices in monocots and in eudicots, their genetic control, and their regulation by ethylene. GSE modify root architecture and induce symbiotic gene expression in both monocots and eudicots. The genetic regulation of root architecture and gene expression was analyzed using M. truncatula and rice symbiotic mutants. These responses are dependent on the common symbiotic pathway as well as another uncharacterized pathway. Significant differences between monocots and eudicots were observed in the genetic control of plant responses to GSE. However, ethylene inhibits GSE-induced symbiotic gene expression and root development in both groups. Our results indicate that GSE signaling shares similarities and differences in monocots versus eudicots, that only a subset of AM signaling pathways has been co-opted in legumes for the establishment of root nodulation with rhizobia, and that regulation of these pathways by ethylene is a feature conserved across higher land plants.

  17. Effect of Arbuscular Mycorrhizal Fungi on the Growth and Polyphenol Profile of Marjoram, Lemon Balm, and Marigold.

    PubMed

    Engel, Rita; Szabó, Krisztina; Abrankó, László; Rendes, Kata; Füzy, Anna; Takács, Tünde

    2016-05-18

    The aim of this study is to examine the effect of arbuscular mycorrhizal fungi (AMF) colonization on biomass, polyphenol profile, and content of economically important herbs. A pot experiment was performed with marjoram, lemon balm, and marigold applying a commercially available AMF mixture for inoculation. Major polyphenols were identified using HPLC-UV-ESI-qTOFMS on the basis of their UV-vis and mass spectral characteristics, and selected ones were quantified. We showed that AMF can provide different services for each herb. Marjoram had the highest level of fungal colonization (82 M%) followed by lemon balm (62 M%) and marigold (17 M%). AMF inoculation significantly increased the biomass of marjoram (1.5-fold), the number of marigold flowers (1.2-fold), and the yield of rosmarinic acid and lithospermic acid isomers of marjoram (1.5-fold) and lemon balm (1.2-fold). Therefore, the quantity and quality of plant material could be improved by the application of optimized AMF inoculum.

  18. Host and non-host roots in rice: cellular and molecular approaches reveal differential responses to arbuscular mycorrhizal fungi

    PubMed Central

    Fiorilli, Valentina; Vallino, Marta; Biselli, Chiara; Faccio, Antonella; Bagnaresi, Paolo; Bonfante, Paola

    2015-01-01

    Oryza sativa, a model plant for Arbuscular Mycorrhizal (AM) symbiosis, has both host and non-host roots. Large lateral (LLR) and fine lateral (FLR) roots display opposite responses: LLR support AM colonization, but FLR do not. Our research aimed to study the molecular, morphological and physiological aspects related to the non-host behavior of FLR. RNA-seq analysis revealed that LLR and FLR displayed divergent expression profiles, including changes in many metabolic pathways. Compared with LLR, FLR showed down-regulation of genes instrumental for AM establishment and gibberellin signaling, and a higher expression of nutrient transporters. Consistent with the transcriptomic data, FLR had higher phosphorus content. Light and electron microscopy demonstrated that, surprisingly, in the Selenio cultivar, FLR have a two-layered cortex, which is theoretically compatible with AM colonization. According to RNA-seq, a gibberellin inhibitor treatment increased anticlinal divisions leading to a higher number of cortex cells in FLR. We propose that some of the differentially regulated genes that lead to the anatomical and physiological properties of the two root types also function as genetic factors regulating fungal colonization. The rice root apparatus offers a unique tool to study AM symbiosis, allowing direct comparisons of host and non-host roots in the same individual plant. PMID:26322072

  19. Cropping practices modulate the impact of glyphosate on arbuscular mycorrhizal fungi and rhizosphere bacteria in agroecosystems of the semiarid prairie.

    PubMed

    Sheng, Min; Hamel, Chantal; Fernandez, Myriam R

    2012-08-01

    A growing body of evidence obtained from studies performed under controlled conditions suggests that glyphosate use can modify microbial community assemblages. However, few studies have examined the influence of glyphosate in agroecosystems. We examined 4 wheat-based production systems typical of the Canadian prairie over 2 years to answer the following question: Does preseeding of glyphosate impact soil rhizosphere microorganisms? If so, do cropping practices influence this impact? Glyphosate caused a shift in the species dominating the arbuscular mycorrhizal fungal community in the rhizosphere, possibly through the modification of host plant physiology. Glyphosate stimulated rhizobacterial growth while having no influence on saprotrophic fungi, suggesting a greater abundance of glyphosate-tolerant 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in bacteria than in fungi. Glyphosate stimulated rhizosphere bacteria in pea but not in urea-fertilized durum wheat, which is consistent with inhibition of EPSPS tolerance to residual glyphosate through high ammonium levels. Mitigation of the effects of glyphosate on rhizosphere bacteria through tillage suggests a reduction in residual glyphosate activity through increased adsorption to soil binding sites upon soil mixing. The influence of glyphosate on Gram-negative bacteria was mitigated under drought conditions in 2007. Our experiment suggests that interactions between soil fertility, tillage, and cropping practices shape the influence of glyphosate use on rhizosphere microorganisms.

  20. Community analysis of arbuscular mycorrhizal fungi and bacteria in the maize mycorrhizosphere in a long-term fertilization trial.

    PubMed

    Toljander, Jonas F; Santos-González, Juan C; Tehler, Anders; Finlay, Roger D

    2008-08-01

    In this study, we investigated the impact of organic and mineral fertilizers on the community composition of arbuscular mycorrhizal (AM) fungi and bacteria in the mycorrhizosphere of maize in a field experiment established in 1956, in south-east Sweden. Roots and root-associated soil aggregates were sampled four times during the growing season in 2005, in control plots and in plots amended with calcium nitrate, ammonium sulphate, green manure, farmyard manure or sewage sludge. Fungi in roots were identified by cloning and sequencing, and bacteria in soil aggregates were analysed by terminal-restriction fragment length polymorphism, cloning and sequencing. The community composition of AM fungi and bacteria was significantly influenced by the different fertilizers. Changes in microbial community composition were mainly correlated with changes in pH induced by the fertilization regime. However, other factors, including phosphate and soil carbon content, also contributed significantly to these changes. Changes in bacterial community composition and a reduction in bacterial taxon richness throughout the growing season were also manifest. The results of this study highlight the importance and significant effects of the long-term application of different fertilizers on edaphic factors and specific groups of fungi and bacteria playing a key role in arable soils.

  1. Diversity of Arbuscular Mycorrhizal Fungi in the Growth Habitat of Kayu Kuku (Pericopsis mooniana Thw.) In Southeast Sulawesi.

    PubMed

    Husna; Budi, Sri Wilarso; Mansur, Irdika; Kusmana, Dan Cecep

    2015-01-01

    Arbuscular Mycorrhizal Fungi (AMF) are categorized as fungi which have symbioses with terrestrial plants and are distributed in various habitat types. The objectives of this research were to investigate the diversity of AMF in stands of kayu kuku (Pericopsis mooniana Thw.) in Southeast Sulawesi. Collection of samples of soil and root were conducted in six locations. Isolation of spores used the method of wet sieving and decanting, whereas AMF identification was conducted by observing morphology of AMF spores. Parameters of AMF diversity, namely species richness, diversity index, dominance index, evenness index and colonization were studied using method of infected root length. Research results showed that location differences affected significantly the spore density and parameters of AMF diversity, except colonization of AMF (p < 0.116). Location around the Governor office showed the highest number of spores (208.6 spores/100 g of soil). Soil chemical properties, such as C, N, P and heavy metal contributed towards AMF spore density and diversity. Soil C and N correlated negatively with spore density. In terms of location, Glomeraceae constituted the genera with the largest number of species and possessed wide distribution in all research locations. In general, natural forest has higher AMF diversity index (Shannon-Weiner diversity index-H'), evenness (E) and species richness (S) as compared with location of PT. Vale Indonesia Tbk.

  2. Arbuscular mycorrhizal fungi inoculation mediated changes in rhizosphere bacterial community structure while promoting revegetation in a semiarid ecosystem.

    PubMed

    Rodríguez-Caballero, G; Caravaca, F; Fernández-González, A J; Alguacil, M M; Fernández-López, M; Roldán, A

    2017-04-15

    The main goal of this study was to assess the effect of the inoculation of four autochthonous shrub species with the arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices on the rhizosphere bacterial community and to ascertain whether such an effect is dependent on the host plant species. Additionally, analysis of rhizosphere soil chemical and biochemical properties was performed to find relationships between them and the rhizosphere bacterial communities. Non-metric multidimensional scaling analysis and subsequent permutational multivariate analysis of variance revealed differences in bacterial community composition and structure between non-inoculated and inoculated rhizospheres. Moreover, an influence of the plant species was observed. Different bacterial groups were found to be indicator taxonomic groups of non-inoculated and inoculated rhizospheres, Gemmatimonadetes and Anaerolineaceae, respectively, being the most notable indicators. As shown by distance based redundancy analysis, the shifts in bacterial community composition and structure mediated by the inoculation with the AM fungus were mainly related to changes in plant nutrients and growth parameters, such as the shoot phosphorus content. Our findings suggest that the AM fungal inoculum was able to modify the rhizosphere bacterial community assemblage while improving the host plant performance.

  3. Soil and geography are more important determinants of indigenous arbuscular mycorrhizal communities than management practices in Swiss agricultural soils.

    PubMed

    Jansa, Jan; Erb, Angela; Oberholzer, Hans-Rudolf; Smilauer, Petr; Egli, Simon

    2014-04-01

    Arbuscular mycorrhizal fungi (AMF) are ubiquitous soil fungi, forming mutualistic symbiosis with a majority of terrestrial plant species. They are abundant in nearly all soils, less diverse than soil prokaryotes and other intensively studied soil organisms and thus are promising candidates for universal indicators of land management legacies and soil quality degradation. However, insufficient data on how the composition of indigenous AMF varies along soil and landscape gradients have hampered the definition of baselines and effect thresholds to date. Here, indigenous AMF communities in 154 agricultural soils collected across Switzerland were profiled by quantitative real-time PCR with taxon-specific markers for six widespread AMF species. To identify the key determinants of AMF community composition, the profiles were related to soil properties, land management and site geography. Our results indicate a number of well-supported dependencies between abundances of certain AMF taxa and soil properties such as pH, soil fertility and texture, and a surprising lack of effect of available soil phosphorus on the AMF community profiles. Site geography, especially the altitude and large geographical distance, strongly affected AMF communities. Unexpected was the apparent lack of a strong land management effect on the AMF communities as compared to the other predictors, which could be due to the rarity of highly intensive and unsustainable land management in Swiss agriculture. In spite of the extensive coverage of large geographical and soil gradients, we did not identify any taxon suitable as an indicator of land use among the six taxa we studied.

  4. Detection of phosphate transporter genes from arbuscular mycorrhizal fungi in mature tree roots under experimental soil pH manipulation

    DOE PAGES

    Carrino-Kyker, Sarah R.; Kluber, Laurel A.; Coyle, Kaitlin P.; ...

    2016-10-04

    We present the majority of terrestrial plant roots are colonized by arbuscular mycorrhizal (AM) fungi that, in exchange for carbon, provide plants with enhanced nutrient uptake — most notably inorganic phosphate (Pi). To mediate the uptake of Pi from the soil, AM fungi possess high affinity inorganic phosphate transporters (PTs). Under laboratory conditions, Pi concentrations have been shown to regulate AM fungal-specific PT gene expression. The relationship between PT expression and Pi in the field remains unexplored. Here we quantify AM fungal-specific PTs from maple tree roots in situ. In an effort to limit edaphic parameters, root samples were collectedmore » from manipulated forested plots that had elevated soil Pi availability, either through direct Pi application or elevating pH to lower exchangeable aluminum. The aim of the study was to examine AM fungal-specific PT gene expression both prior to and following soil Pi amendment; however, a direct correlation between soil Pi concentration and PT gene expression was not observed. PT transcripts were detected to a greater extent under elevated pH and, while our results are confounded by an overall low detection of PT genes (23 % of all samples collected), our findings raise interesting questions regarding the role of soil pH on PT function. In conclusion, our study is a first step in understanding how edaphic properties influence PT expression and plant P acquisition in mature tree roots.« less

  5. Molecular diversity of arbuscular mycorrhizal fungi associated with two co-occurring perennial plant species on a Tibetan altitudinal gradient.

    PubMed

    Li, Xiaoliang; Gai, Jingping; Cai, Xiaobu; Li, Xiaolin; Christie, Peter; Zhang, Fusuo; Zhang, Junling

    2014-02-01

    Plant communities on Mount Segrila on the Tibetan Plateau show distinct changes at different altitudes, but little information is available on belowground communities of arbuscular mycorrhizal fungi (AMF). Root samples of two co-occurring species, Pennisetum centrasiaticum and Kobresia sp., growing in open grasslands at eight altitudes (3,446-4,556 m) were analyzed for diversity of AMF by PCR, cloning, and sequencing. Dominant plants were well colonized by AMF even at higher altitudes where spore density in rhizospheres decreased dramatically. A total of 29 operational taxonomic units (OTUs) of AMF were detected, and some novel sequence types were found. Acaulosporaceae and Glomeraceae were the dominant families. There was no significant difference in OTU richness along elevational gradients in Kobresia sp., but OTU richness in P. centrasiaticum was higher at intermediate elevations. Elevation, host plant species, and soil variables (pH, soil organic matter, and available P and N) were found to have significant effects on the overall AMF community across all elevations. Fungal community composition differed significantly between the two plant species at each elevation, and the similarity was generally higher at the intermediate elevations. No significant difference in compositional similarity was observed for Kobresia sp. with increasing elevation, but the dissimilarity increased significantly for P. centrasiaticum. These results suggest that host identity is an important determinant for the structure of the AMF communities along the elevational gradients in high altitude environments.

  6. Inoculation of somatic embryos of sweet potato with an arbuscular mycorrhizal fungus improves embryo survival and plantlet formation.

    PubMed

    Bressan, W; de Carvalho, C H; Sylvia, D M

    2000-08-01

    Responses of somatic embryos of sweet potato (Ipomoea batata (L.) Poir., cv. White Star) at different developmental stages to in vitro inoculation with Glomus etunicatum (Becker and Gerdemann) (isolate INVAM FL329) were evaluated. Somatic embryos were grown in glass tubes containing sterilized vermiculite and sand. A layer of natrosol plus White's medium was used as a carrier for arbuscular mycorrhizal (AM) fungal spores. Survival of embryos inoculated with AM fungi was significantly (P < 0.05) greater than that of noninoculated embryos at the rooted-cotyledonary-torpedo and rooted-elongated-torpedo developmental stages. Mycorrhizae significantly (P < 0.05) increased plantlet formation only when inoculation occurred at the rooted-elongated-torpedo developmental stage. The growth stage at which the embryos were inserted into the glass tubes exerted a significant influence upon plantlet formation, and plantlet formation was further enhanced by inoculation with G. etunicatum. Plantlet formation was greatest at the rooted-elongated-torpedo stage. These results demonstrate that inoculation of somatic embryos with AM fungi improves embryo survival and plantlet formation, and could enhance use of somatic embryos as synthetic seeds.

  7. Communities of arbuscular mycorrhizal fungi detected in forest soil are spatially heterogeneous but do not vary throughout the growing season.

    PubMed

    Davison, John; Öpik, Maarja; Zobel, Martin; Vasar, Martti; Metsis, Madis; Moora, Mari

    2012-01-01

    Despite the important ecosystem role played by arbuscular mycorrhizal fungi (AMF), little is known about spatial and temporal variation in soil AMF communities. We used pyrosequencing to characterise AMF communities in soil samples (n = 44) from a natural forest ecosystem. Fungal taxa were identified by BLAST matching of reads against the MaarjAM database of AMF SSU rRNA gene diversity. Sub-sampling within our dataset and experimental shortening of a set of long reads indicated that our approaches to taxonomic identification and diversity analysis were robust to variations in pyrosequencing read length and numbers of reads per sample. Different forest plots (each 10 × 10 m and separated from one another by 30 m) contained significantly different soil AMF communities, and the pairwise similarity of communities decreased with distance up to 50 m. However, there were no significant changes in community composition between different time points in the growing season (May-September). Spatial structure in soil AMF communities may be related to the heterogeneous vegetation of the natural forest study system, while the temporal stability of communities suggests that AMF in soil represent a fairly constant local species pool from which mycorrhizae form and disband during the season.

  8. Arbuscular mycorrhizal fungal communities along a pedo-hydrological gradient in a Central Amazonian terra firme forest.

    PubMed

    de Oliveira Freitas, Rejane; Buscardo, Erika; Nagy, Laszlo; dos Santos Maciel, Alex Bruno; Carrenho, Rosilaine; Luizão, Regina C C

    2014-01-01

    Little attention has been paid to plant mutualistic interactions in the Amazon rainforest, and the general pattern of occurrence and diversity of arbuscular mycorrhizal fungi (AMF) in these ecosystems is largely unknown. This study investigated AMF communities through their spores in soil in a 'terra firme forest' in Central Amazonia. The contribution played by abiotic factors and plant host species identity in regulating the composition, abundance and diversity of such communities along a topographic gradient with different soils and hydrology was also evaluated. Forty-one spore morphotypes were observed with species belonging to the genera Glomus and Acaulospora, representing 44 % of the total taxa. Soil texture and moisture, together with host identity, were predominant factors responsible for shaping AMF communities along the pedo-hydrological gradient. However, the variability within AMF communities was largely associated with shifts in the relative abundance of spores rather than changes in species composition, confirming that common AMF species are widely distributed in plant communities and all plants recruited into the forest are likely to be exposed to the dominant sporulating AMF species.

  9. Arbuscular Mycorrhizal Fungi for the Biocontrol of Plant-Parasitic Nematodes: A Review of the Mechanisms Involved

    PubMed Central

    Schouteden, Nele; De Waele, Dirk; Panis, Bart; Vos, Christine M.

    2015-01-01

    Arbuscular mycorrhizal fungi (AMF) are obligate root symbionts that can protect their host plant against biotic stress factors such as plant-parasitic nematode (PPN) infection. PPN consist of a wide range of species with different life styles that can cause major damage in many important crops worldwide. Various mechanisms have been proposed to play a role in the biocontrol effect of AMF against PPN. This review presents an overview of the different mechanisms that have been proposed, and discusses into more detail the plausibility of their involvement in the biocontrol against PPN specifically. The proposed mechanisms include enhanced plant tolerance, direct competition for nutrients and space, induced systemic resistance (ISR) and altered rhizosphere interactions. Recent studies have emphasized the importance of ISR in biocontrol and are increasingly placing rhizosphere effects on the foreground as well, both of which will be the focal point of this review. Though AMF are not yet widely used in conventional agriculture, recent data help to develop a better insight into the modes of action, which will eventually lead toward future field applications of AMF against PPN. The scientific community has entered an exciting era that provides the tools to actually unravel the underlying molecular mechanisms, making this a timely opportunity for a review of our current knowledge and the challenges ahead. PMID:26635750

  10. 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.

  11. Arbuscular mycorrhizal fungi in soil and roots respond differently to phosphorus inputs in an intensively managed calcareous agricultural soil.

    PubMed

    Liu, Wei; Zhang, Yunlong; Jiang, Shanshan; Deng, Yan; Christie, Peter; Murray, Philip J; Li, Xiaolin; Zhang, Junling

    2016-04-22

    Understanding the diversity and community structure of arbuscular mycorrhizal fungi (AMF) is important for potentially optimizing their role in mining phosphorus (P) in agricultural ecosystems. Here, we conduct a comprehensive study to investigate the vertical distribution of AMF in a calcareous field and their temporal structure in maize-roots with fertilizer P application over a three-year period. The results showed that soil available-P response to P fertilization but maize yields did not. Phosphorus fertilization had no-significant effect on richness of AMF except at greater soil-depths. High P-supply reduced root colonization while optimum-P tended to increase colonization and fungal richness on all sampling occasions. Crop phenology might override P-supply in determining the community composition of active root inhabiting fungi. Significant differences in the community structure of soil AMF were observed between the controls and P treatments in surface soil and the community shift was attributable mainly to available-P, N/P and pH. Vertical distribution was related mainly to soil electrical conductivity and Na content. Our results indicate that the structure of AMF community assemblages is correlated with P fertilization, soil depth and crop phenology. Importantly, phosphorus management must be integrated with other agricultural-practices to ensure the sustainability of agricultural production in salinized soils.

  12. Communities of Arbuscular Mycorrhizal Fungi Detected in Forest Soil Are Spatially Heterogeneous but Do Not Vary throughout the Growing Season

    PubMed Central

    Davison, John; Öpik, Maarja; Zobel, Martin; Vasar, Martti; Metsis, Madis; Moora, Mari

    2012-01-01

    Despite the important ecosystem role played by arbuscular mycorrhizal fungi (AMF), little is known about spatial and temporal variation in soil AMF communities. We used pyrosequencing to characterise AMF communities in soil samples (n = 44) from a natural forest ecosystem. Fungal taxa were identified by BLAST matching of reads against the MaarjAM database of AMF SSU rRNA gene diversity. Sub-sampling within our dataset and experimental shortening of a set of long reads indicated that our approaches to taxonomic identification and diversity analysis were robust to variations in pyrosequencing read length and numbers of reads per sample. Different forest plots (each 10×10 m and separated from one another by 30 m) contained significantly different soil AMF communities, and the pairwise similarity of communities decreased with distance up to 50 m. However, there were no significant changes in community composition between different time points in the growing season (May-September). Spatial structure in soil AMF communities may be related to the heterogeneous vegetation of the natural forest study system, while the temporal stability of communities suggests that AMF in soil represent a fairly constant local species pool from which mycorrhizae form and disband during the season. PMID:22879900

  13. 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.

  14. The effects of triclosan on spore germination and hyphal growth of the arbuscular mycorrhizal fungus Glomus intraradices.

    PubMed

    Twanabasu, Bishnu R; Stevens, Kevin J; Venables, Barney J

    2013-06-01

    The effect of triclosan (5-chloro-2-[2,4-dichlorophenoxy]phenol; TCS), on spore germination, hyphal growth, and hyphal branching of the arbuscular mycorrhizal (AM) fungus, Glomus intraradices spores was evaluated at exposure concentrations of 0.4 and 4.0 μg/L in a static renewal exposure system. To determine if potential effects were mycotoxic or a consequence of impaired signaling between a host plant and the fungal symbiont, spores were incubated with and without the addition of a root exudate. Exposed spores were harvested at days 7, 14, and 21. AM spore germination, hyphal growth, and hyphal branching were significantly lower in both TCS concentrations compared to controls in non-root exudate treatments suggesting direct mycotoxic effects of TCS on AM development. Greater hyphal growth and hyphal branching in controls and 0.4μg/L TCS treatments with root exudate compared to non-root exudate treatments demonstrated growth stimulation by signaling chemicals present in the root exudate. This stimulatory effect was absent in the 4.0 μg/L TCS treatments indicating a direct effect on plant signaling compounds or plant signal response.

  15. Arbuscular mycorrhizal hyphopodia and germinated spore exudates trigger Ca2+ spiking in the legume and nonlegume root epidermis.

    PubMed

    Chabaud, Mireille; Genre, Andrea; Sieberer, Björn J; Faccio, Antonella; Fournier, Joëlle; Novero, Mara; Barker, David G; Bonfante, Paola

    2011-01-01

    • The aim of this study was to investigate Ca(2+) responses to endosymbiotic arbuscular mycorrhizal (AM) fungi in the host root epidermis following pre-infection hyphopodium formation in both legumes and nonlegumes, and to determine to what extent these responses could be mimicked by germinated fungal spore exudate. • Root organ cultures of both Medicago truncatula and Daucus carota, expressing the nuclear-localized cameleon reporter NupYC2.1, were used to monitor AM-elicited Ca(2+) responses in host root tissues. • Ca(2+) spiking was observed in cells contacted by AM hyphopodia for both hosts, with highest frequencies correlating with the epidermal nucleus positioned facing the fungal contact site. Treatment with AM spore exudate also elicited Ca(2+) spiking within the AM-responsive zone of the root and, in both cases, spiking was dependent on the M. truncatula common SYM genes DMI1/2, but not on the rhizobial Nod factor perception gene NFP. • These findings support the conclusion that AM fungal root penetration is preceded by a SYM pathway-dependent oscillatory Ca(2+) response, whose evolutionary origin predates the divergence between asterid and rosid clades. Our results further show that fungal symbiotic signals are already generated during spore germination, and that cameleon-expressing root organ cultures represent a novel AM-specific bio-assay for such signals.

  16. Arbuscular mycorrhizal fungi in soil and roots respond differently to phosphorus inputs in an intensively managed calcareous agricultural soil

    PubMed Central

    Liu, Wei; Zhang, Yunlong; Jiang, Shanshan; Deng, Yan; Christie, Peter; Murray, Philip J.; Li, Xiaolin; Zhang, Junling

    2016-01-01

    Understanding the diversity and community structure of arbuscular mycorrhizal fungi (AMF) is important for potentially optimizing their role in mining phosphorus (P) in agricultural ecosystems. Here, we conduct a comprehensive study to investigate the vertical distribution of AMF in a calcareous field and their temporal structure in maize-roots with fertilizer P application over a three-year period. The results showed that soil available-P response to P fertilization but maize yields did not. Phosphorus fertilization had no-significant effect on richness of AMF except at greater soil-depths. High P-supply reduced root colonization while optimum-P tended to increase colonization and fungal richness on all sampling occasions. Crop phenology might override P-supply in determining the community composition of active root inhabiting fungi. Significant differences in the community structure of soil AMF were observed between the controls and P treatments in surface soil and the community shift was attributable mainly to available-P, N/P and pH. Vertical distribution was related mainly to soil electrical conductivity and Na content. Our results indicate that the structure of AMF community assemblages is correlated with P fertilization, soil depth and crop phenology. Importantly, phosphorus management must be integrated with other agricultural-practices to ensure the sustainability of agricultural production in salinized soils. PMID:27102357

  17. Combined phosphate and nitrogen limitation generates a nutrient stress transcriptome favorable for arbuscular mycorrhizal symbiosis in Medicago truncatula.

    PubMed

    Bonneau, Laurent; Huguet, Stéphanie; Wipf, Daniel; Pauly, Nicolas; Truong, Hoai-Nam

    2013-07-01

    Arbuscular mycorrhizal (AM) symbiosis is stimulated by phosphorus (P) limitation and contributes to P and nitrogen (N) acquisition. However, the effects of combined P and N limitation on AM formation are largely unknown. Medicago truncatula plants were cultivated in the presence or absence of Rhizophagus irregularis (formerly Glomus intraradices) in P-limited (LP), N-limited (LN) or combined P- and N-limited (LPN) conditions, and compared with plants grown in sufficient P and N. The highest AM formation was observed in LPN, linked to systemic signaling by the plant nutrient status. Plant free phosphate concentrations were higher in LPN than in LP, as a result of cross-talk between P and N. Transcriptome analyses suggest that LPN induces the activation of NADPH oxidases in roots, concomitant with an altered profile of plant defense genes and a coordinate increase in the expression of genes involved in the methylerythritol phosphate and isoprenoid-derived pathways, including strigolactone synthesis genes. Taken together, these results suggest that low P and N fertilization systemically induces a physiological state of plants favorable for AM symbiosis despite their higher P status. Our findings highlight the importance of the plant nutrient status in controlling plant-fungus interaction.

  18. On-farm production of inoculum of indigenous arbuscular mycorrhizal fungi and assessment of diluents of compost for inoculum production.

    PubMed

    Douds, David D; Nagahashi, Gerald; Hepperly, Paul Reed

    2010-04-01

    On-farm production of arbuscular mycorrhizal [AM] fungus inoculum can be employed to make the benefits of the symbiosis more available to vegetable farmers. Experiments were conducted to modify an existing method for the production of inoculum in temperate climates to make it more readily adoptable by farmers. Perlite, vermiculite, and peat based potting media were tested as diluents of yard clippings compost for the media in which the inoculum was produced using bahiagrass (Paspalum notatum Flugge) as host plant. All produced satisfactory concentrations of AM fungus propagules, though vermiculite proved to be better than potting media (89 vs. 25 propagules cm(-3), respectively). Two methods were tested for the growth of AM fungi indigenous to the farm: (1) adding field soil into the vermiculite and compost mixture and (2) pre-colonizing the bahiagrass seedlings in media inoculated with field soil prior to transplant into that mixture. Adding 100 cm(3) of field soil to the compost and vermiculite produced 465 compared to 137 propagules cm(-3) for the pre-colonization method. The greater flexibility these modifications give will make it easier for farmers to produce inoculum of AM fungi on-the-farm.

  19. Arbuscular mycorrhizal fungi in national parks, nature reserves and protected areas worldwide: a strategic perspective for their in situ conservation.

    PubMed

    Turrini, Alessandra; Giovannetti, Manuela

    2012-02-01

    Soil fungi play a crucial role in producing fundamental ecosystem services such as soil fertility, formation and maintenance, nutrient cycling and plant community dynamics. However, they have received little attention in the field of conservation biology. Arbuscular mycorrhizal fungi (AMF) are beneficial soil symbionts fulfilling a key function in the complex networks of belowground/aboveground biotic interactions as they live in association with the roots of most (80%) land plant families and influence not only soil fertility but also plant nutrition, diversity and productivity. The diversity of AMF communities can decline due to habitat loss and anthropogenic disturbance, especially in agro-ecosystems, and many valuable ecotypes could become extinct before they are even discovered. Consequently, long-term strategies are urgently needed to ensure their conservation in habitats where they naturally occur and have evolved. Protected areas, where living organisms are under the care of national and international authorities, represent an appropriate place for the in situ conservation of AMF, providing them with adapted situations together with established complex networks of interactions with different components within each specific ecosystem. Here, we review data available about the main present-day threats to AMF and the current state of knowledge about their occurrence in protected sites worldwide, providing a checklist of national parks and nature reserves where they have been reported. The aim was to offer a strategic perspective to increase awareness of the importance of conserving these beneficial plant symbionts and of preserving their biodiversity in the years to come.

  20. Effect of vegetation types on soil arbuscular mycorrhizal fungi and nitrogen-fixing bacterial communities in a karst region.

    PubMed

    Liang, Yueming; Pan, Fujing; He, Xunyang; Chen, Xiangbi; Su, Yirong

    2016-09-01

    Arbuscular mycorrhizal (AM) fungi and nitrogen-fixing bacteria play important roles in plant growth and recovery in degraded ecosystems. The desertification in karst regions has become more severe in recent decades. Evaluation of the fungal and bacterial diversity of such regions during vegetation restoration is required for effective protection and restoration in these regions. Therefore, we analyzed relationships among AM fungi and nitrogen-fixing bacteria abundances, plant species diversity, and soil properties in four typical ecosystems of vegetation restoration (tussock (TK), shrub (SB), secondary forest (SF), and primary forest (PF)) in a karst region of southwest China. Abundance of AM fungi and nitrogen-fixing bacteria, plant species diversity, and soil nutrient levels increased from the tussock to the primary forest. The AM fungus, nitrogen-fixing bacterium, and plant community composition differed significantly between vegetation types (p < 0.05). Plant richness and pH were linked to the community composition of fungi and nitrogen-fixing bacteria, respectively. Available phosphorus, total nitrogen, and soil organic carbon levels and plant richness were positively correlated with the abundance of AM fungi and nitrogen-fixing bacteria (p < 0.05). The results suggested that abundance of AM fungi and nitrogen-fixing bacteria increased from the tussock to the primary forest and highlight the essentiality of these communities for vegetation restoration.

  1. Foliar Spray with Vermiwash Modifies the Arbuscular Mycorrhizal Dependency and Nutrient Stoichiometry of Bhut Jolokia (Capsicum assamicum)

    PubMed Central

    Gupta, Rajeev; Veer, Vijay; Singh, Lokendra; Kalita, Mohan C.

    2014-01-01

    Vermiwash (VW), a liquid extract obtained from vermicomposting beds, is used as an organic fertilizer for crop plants. The current study investigated the effect of a vermiwash foliar spray on the response of bhut jolokia (Capsicum assamicum) exposed to two different arbuscular mycorrhizal fungi (AMF: Rhizophagus irregularis, RI and G. mosseae, GM) in acidic soil under naturally ventilated greenhouse conditions. The VW spray significantly influenced the growth of plants receiving the dual treatment of AMF+VW. Plant growth was more prominent in the GM+VW treatment group than that in the RI+VW treatment group. The plant-AMF interactions in relation to growth and nutrient requirements were also significantly influenced by the application of VW. Interestingly, the VW treatment appeared to contribute more N to plants when compared to that under the AMF treatment, which led to changes in the C:N:P stoichiometry in plant shoots. Furthermore, the increased potassium dependency, as observed in the case of the dual treatments, suggests the significance of such treatments for improving crop conditions under salt stress. Overall, our study shows that the VW foliar spray modifies the response of a crop to inoculations of different AMF with regard to growth and nutrient utilization, which has implications for the selection of an efficient combination of nutrient source for improving crop growth. PMID:24651577

  2. Arbuscular mycorrhizal fungi communities in a coral cay system (Morrocoy, Venezuela) and their relationships with environmental variables.

    PubMed

    Alguacil, M M; Torrecillas, E; Lozano, Z; Roldán, A

    2015-02-01

    Knowledge of the natural diversity of arbuscular mycorrhizal fungi (AMF) and understanding of their biogeographical patterns and what drive them might help to the maintenance and preservation of ecosystems under a changing environment. The objective of this study was to evaluate the contribution of different environmental factors to the determination of the composition of AMF assemblages in representative sites within the Morrocoy National Park (Venezuela). The community structure of the AMF under the canopy of Coccoloba uvifera was investigated in four cays (Borracho, Muerto, Peraza, and Paiclás) and one mainland location (Las Luisas). Based on partial sequences of the nuclear small subunit ribosomal DNA gene, the AM fungi in soil samples were divided into 31 operational taxonomic units, grouped in eight families. The canonical correspondence analysis showed that environmental factors related to insularity (the mean annual rainfall, the distance to the mainland coast, and the cay land area) and a soil property related to biological activity (the total carbohydrate content) were significantly related to the distribution of the AMF communities.

  3. Communities of arbuscular mycorrhizal fungi in Pyrus pyrifolia var. culta (Japanese pear) and an understory herbaceous plant Plantago asiatica.

    PubMed

    Yoshimura, Yuko; Ido, Akifumi; Matsumoto, Teruyuki; Yamato, Masahide

    2013-01-01

    We investigated communities of arbuscular mycorrhizal fungi (AMF) in the fine roots of Pyrus pyrifolia var. culta, and Plantago asiatica to consider the relationship between orchard trees and herbaceous plants in AMF symbioses. The AMF communities were analyzed on the basis of the partial fungal DNA sequences of the nuclear small subunit ribosomal RNA gene (SSU rDNA), which were amplified using the AMF-specific primers AML1 and AML2. Phylogenetic analysis showed that the obtained AMF sequences were divided into 23 phylotypes. Among them, 12 phylotypes included AMF from both host plants, and most of the obtained sequences (689/811) were affiliated to them. Canonical correspondence analysis showed that the host plant species did not have a significant effect on the distribution of AMF phylotypes, whereas the effects of sampling site, soil total C, soil total N and soil-available P were significant. It was also found that the mean observed overlaps of AMF phylotypes between the paired host plants in the same soil cores (27.1% of phylotypes shared) were significantly higher than the mean 1,000 simulated overlaps (14.2%). Furthermore, the same AMF sequences (100% sequence identity) were detected from both host plants in 8/12 soil cores having both roots. Accordingly, we concluded that Py. pyrifolia and Pl. asiatica examined shared some AMF communities, which suggested that understory herbaceous plants may function as AMF inoculum sources for orchard trees.

  4. Interactive Effects of Arbuscular Mycorrhizal Fungi and Copper Stress on Flowering Phenology and Reproduction of Elsholtzia splendens

    PubMed Central

    Jin, Zexin; Li, Junmin; Li, Yueling

    2015-01-01

    Plant responses to heavy metal contamination may depend on the presence of arbuscular mycorrhizal fungi (AMF). Elsholtzia splendens is an indicator species for the presence of copper (Cu) mines because both its flowering phenology and reproduction are tolerant to heavy metals. To test whether effects of Cu on the flowering phenology and reproduction of E. splendens depend on the presence of AMF, we conducted a factorial experiment with two Cu treatments (with or without Cu addition) crossed with two AMF treatments (with or without AMF inoculation). Without AMF, Cu addition significantly delayed the onset dates, ending dates and peak dates of flowering and decreased flowering duration. However, AMF inocula