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

    PubMed

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

    2016-10-01

    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.

  3. 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.

  4. 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

  5. Triclosan inhibits arbuscular mycorrhizal colonization in three wetland plants.

    PubMed

    Twanabasu, Bishnu R; Smith, Caleb M; Stevens, Kevin J; Venables, Barney J; Sears, William C

    2013-03-01

    In terrestrial ecosystems, plant growth, plant community structure, and ultimately the ecosystem services provided by plants are dependent on the presence and composition of below ground arbuscular mycorrhizal (AM) fungal communities. AM fungi form obligate symbioses with plants providing nutrients to their host plants in exchange for photosynthates. While AM have been found in most wetland ecosystems, the effects of urban contaminants on AM associations are largely unknown. Triclosan (5-chloro-2-[2,4-dichlorophenoxy]phenol; TCS) is a widespread contaminant found in surface waters throughout North America and in addition to antimicrobial properties is purported to have antifungal properties. To determine the effects of TCS on arbuscular mycorrhizal associations, we exposed AM inoculated wetland plant species (Eclipta prostrata, Hibiscus laevis, and Sesbania herbacea) to TCS at concentrations of 0.0, 0.4 and 4.0 μg/L in a continuous flow-through exposure system. TCS exposure caused significant reductions in hyphal and arbuscular colonization while no significant effect was detected for vesicular colonization. Across all species, hyphal colonization was significantly higher in controls (18.58 ± 1.84%) compared to 0.4 and 4.0 μg/L (10.20 ± 1.34% and 9.86 ± 1.32% respectively) TCS treatments. Similarly, arbuscular colonization was significantly higher in the controls (4.58 ± 0.75%) compared to 0.4 μg/L (2.20 ± 0.38%) and 4.0 μg/L (1.22 ± 0.24%) TCS exposures. Since our lowest effect concentration, 0.4 μg/L, lies within the range of concentrations found in North American streams it is plausible that AM colonization has been impacted in streams receiving WWTP effluent. Further studies are required to understand the mechanism of TCS inhibition of mycorrhizal colonization in wetland plant species as well as the potential ecological consequences that a decline in the AM colonization levels may represent. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. 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.

  7. Genetic variability in arbuscular mycorrhizal fungi compatibility supports the selection of durum wheat genotypes for enhancing soil ecological services and cropping systems in Canada.

    PubMed

    Singh, A K; Hamel, C; Depauw, R M; Knox, R E

    2012-03-01

    Crop nutrient- and water-use efficiency could be improved by using crop varieties highly compatible with arbuscular mycorrhizal fungi (AMF). Two greenhouse experiments demonstrated the presence of genetic variability for this trait in modern durum wheat ( Triticum turgidum L. var. durum Desf.) germplasm. Among the five cultivars tested, 'AC Morse' had consistently low levels of AM root colonization and DT710 had consistently high levels of AM root colonization, whereas 'Commander', which had the highest colonization levels under low soil fertility conditions, developed poor colonization levels under medium fertility level. The presence of genetic variability in durum wheat compatibility with AMF was further evidenced by significant genotype × inoculation interaction effects in grain and straw biomass production; grain P, straw P, and straw K concentrations under medium soil fertility level; and straw K and grain Fe concentrations at low soil fertility. Mycorrhizal dependency was an undesirable trait of 'Mongibello', which showed poor growth and nutrient balance in the absence of AMF. An AMF-mediated reduction in grain Cd under low soil fertility indicated that breeding durum wheat for compatibility with AMF could help reduce grain Cd concentration in durum wheat. Durum wheat genotypes should be selected for compatibility with AMF rather than for mycorrhizal dependency.

  8. 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.

  9. 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

  10. 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.

  11. Occurrence of arbuscular mycorrhizal fungi on King George Island, South Shetland Islands, Antarctica.

    PubMed

    Barbosa, Marisângela V; Pereira, Elismara A; Cury, Juliano C; Carneiro, Marco A C

    2017-08-17

    Arbuscular mycorrhizal fungi make up an important ecological niche in ecosystems, and knowledge of their diversity in extreme environments is still incipient. The objective of this work was to evaluate the density and diversity of arbuscular mycorrhizal fungi in the soil of King George Island in the South Shetland Islands archipelago, Antarctica. For that, soil and roots of Deschampsia antarctica were collected at the brazilian research station in Antarctica. The spore density, species diversity and mycorrhizal colonization in the roots were evaluated. There was a low density of spores (27.4 ± 17.7) and root mycorrhizal colonization (6 ± 5.1%), which did not present statistical difference. Four species of arbuscular mycorrhizal fungi were identified, distributed in two genera: three species of the genus Glomus (Glomus sp1, Glomus sp2 and Glomus sp3) and one of the genus Acaulospora, which was identified at species level (Acaulospora mellea). Greater soil diversity was verified with pH 5.9 and phosphorus concentration of 111 mg dm-3, occurring two species of genus Glomus and A. mellea. Based on literature data, this may be the first record of this species of Acaulospora mellea in Antarctic soils, colonizing D. antarctica plants.

  12. Can Arbuscular Mycorrhizal Fungi Reduce the Growth of Agricultural Weeds?

    PubMed Central

    Veiga, Rita S. L.; Jansa, Jan; Frossard, Emmanuel; van der Heijden, Marcel G. A.

    2011-01-01

    Background Arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects on plants. However, there is increasing evidence that some ruderal plants, including several agricultural weeds, respond negatively to AMF colonization. Here, we investigated the effect of AMF on the growth of individual weed species and on weed-crop interactions. Methodology/Principal Findings First, under controlled glasshouse conditions, we screened growth responses of nine weed species and three crops to a widespread AMF, Glomus intraradices. None of the weeds screened showed a significant positive mycorrhizal growth response and four weed species were significantly reduced by the AMF (growth responses between −22 and −35%). In a subsequent experiment, we selected three of the negatively responding weed species – Echinochloa crus-galli, Setaria viridis and Solanum nigrum – and analyzed their responses to a combination of three AMF (Glomus intraradices, Glomus mosseae and Glomus claroideum). Finally, we tested whether the presence of a crop (maize) enhanced the suppressive effect of AMF on weeds. We found that the growth of the three selected weed species was also reduced by a combination of AMF and that the presence of maize amplified the negative effect of AMF on the growth of E. crus-galli. Conclusions/Significance Our results show that AMF can negatively influence the growth of some weed species indicating that AMF have the potential to act as determinants of weed community structure. Furthermore, mycorrhizal weed growth reductions can be amplified in the presence of a crop. Previous studies have shown that AMF provide a number of beneficial ecosystem services. Taken together with our current results, the maintenance and promotion of AMF activity may thereby contribute to sustainable management of agroecosystems. However, in order to further the practical and ecological relevance of our findings, additional experiments should be performed under field conditions. PMID

  13. 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

  14. 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.

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

    USDA-ARS?s Scientific Manuscript database

    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...

  16. 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

  17. Arsenic uptake and phytoremediation potential by arbuscular mycorrhizal fungi

    Treesearch

    Xinhua He; Erik Lilleskov

    2014-01-01

    Arsenic (As) contamination of soils and water is a global problem because of its impacts on ecosystems and human health. Various approaches have been attempted for As remediation, with limited success. Arbuscular mycorrhizal (AM) fungi play vital roles in the uptake of water and essential nutrients, especially phosphorus (P), and hence enhance plant performance and...

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. Soil characteristics driving arbuscular mycorrhizal fungi communities in semiarid soils

    NASA Astrophysics Data System (ADS)

    Torrecillas, Emma; del Mar Alguacil, Maria; Torres, Pilar; Díaz, Gisela; Caravaca, Fuensanta; Montesinos, Alicia; Roldán, Antonio

    2014-05-01

    Arbuscular mycorrhizal fungi (AMF) are an important soil microbial group that affects multiple ecosystems functions and processes, including nutrient cycling, plant productivity and competition, and plant diversity. We carried out a study to investigate AMF communities in the roots and the rhizosphere of Brachypodium retusum (Pers.) Beauv., a common plant species of great ecological importance that grows in different type of soils in semiarid Mediterranean areas with similar climatic conditions. We hypothesized that if both factors, host plant species and climatic conditions, cannot influence the differences in AMF communities in the roots and in the rhizosphere of Brachypodium retusum, variances in AMF richness and diversity could be due to soil characteristics. Hence we study the relationships between physical, chemical and biological soil characteristics and AMF community composition found in the roots and in the rhizospheres. We recorded sixty-seven AMF operational taxonomical units (OTUs). Each soil type presented a different AMF community composition and thus, can be characterized by its own AMF communities. A combination among some of the soil parameters could define the AMF species present in the roots and the rhizosphere of B. retusum. It was the case for calcium, urease, protease and ß-glucosidase which explained the variation in the AMF communities. In conclusion, soil charactristics can be decisive in the assembling of the AMF communities, managing the diversity and composition of these communities.

  3. 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. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

  4. [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.

  5. 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.

  6. 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

  7. Differences in arbuscular mycorrhizal fungi among three coffee cultivars in Puerto Rico

    Treesearch

    Ligia Lebrón; Jean D. Lodge; Paul. Bayman

    2012-01-01

    Mycorrhizal symbiosis is important for growth of coffee (Coffea arabica), but differences among coffee cultivars in response to mycorrhizal interactions have not been studied. We compared arbuscular mycorrhizal (AM) extraradical hyphae in the soil and diversity of AM fungi among three coffee cultivars, Caturra, Pacas, and Borbon, at three farms in...

  8. 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

  9. 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

  10. 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.

  11. Global and Regional Pools of Arbuscular Mycorrhizal Fungi, a Common Soil Microbe

    NASA Astrophysics Data System (ADS)

    Treseder, K. K.; Cross, A.; Randerson, J. T.

    2003-12-01

    Belowground carbon pools in ecosystems have historically been difficult to quantify. Particularly challenging to measure are arbuscular mycorrhizal fungi, a functional group that forms mutualistic symbioses with plants and augments nutrient uptake. These fungi also produce glomalin, a recalcitrant protein that is abundant enough in the soil to constitute a potentially significant carbon sink. We estimated standing stocks of arbuscular mycorrhizal hyphae using "bottom-up" and "top-down" approaches based, respectively, on published values of root colonization by arbuscular mycorrhizal fungi, and a model incorporating net primary productivity derived from remote sensing data. Global biomass of arbuscular mycorrhizal hyphae was approximated as 43 Tg in bottom-up estimates and 140 Tg in top-down calculations. Thus, hyphal biomass was equivalent to only 0.3 to 1% of standing root biomass. However, the estimated total length of arbuscular mycorrhizal hyphae (18 x 1018 to 59 x 1018 m) was more than 20 times the length of their associated live fine roots. Temperate grasslands, savannas, and tropical rainforests contained the largest pools of arbuscular mycorrhizal hyphae. These budgets could assist researchers in predicting larger-scale responses of arbuscular mycorrhizal fungi--and ecosystems in general--to global change.

  12. 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.

  13. Effects of Organic Farming on Communities of Arbuscular Mycorrhizal Fungi

    PubMed Central

    Lee, Si-Woo; Lee, Eun-Hwa

    2008-01-01

    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. PMID:23997602

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. The role of metal nanoparticles in influencing arbuscular mycorrhizal fungi effects on plant growth.

    PubMed

    Feng, Youzhi; Cui, Xiangchao; He, Shiying; Dong, Ge; Chen, Min; Wang, Junhua; Lin, Xiangui

    2013-08-20

    A knowledge gap still remains concerning the in situ influences of nanoparticles on plant systems, partly due to the absence of soil microorganisms. Arbuscular mycorrhizal fungi (AMF) can form a mutualistic symbiosis with the roots of over 90% of land plants. This investigation sought to reveal the responses of mycorrhizal clover (Trifolium repens) to silver nanoparticles (AgNPs) and iron oxide nanoparticles (FeONPs) along a concentration gradient of each. FeONPs at 3.2 mg/kg significantly reduced mycorrhizal clover biomass by 34% by significantly reducing the glomalin content and root nutrient acquisition of AMF. In contrast, no negative effects of AgNPs at concentrations over 0.1 mg/kg were observed; however, AgNPs at 0.01 mg/kg inhibited mycorrhizal clover growth. In response to the elevated AgNPs content, the ability of AMF to alleviate AgNPs stress (via increased growth and ecological behaviors) was enhanced, which decreased Ag content and the activities of antioxidant enzymes in plants. These results were further supported by X-ray microcomputed tomography. Our findings suggest that in soil ecosystem, the influence of nanometals on plant systems would be more complicated than expected, and more attention should be focused on plant responses in combination with those of soil microorganisms.

  2. 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.

  3. Plant Functional Traits Associated with Mycorrhizal Root Foraging in Arbuscular Mycorrhizal and Ectomycorrhizal Trees

    NASA Astrophysics Data System (ADS)

    Eissenstat, D. M.; Chen, W.; Cheng, L.; Liu, B.; Koide, R. T.; Guo, D.

    2016-12-01

    Root foraging for nutrient "hot spots" is a key strategy by which some plants maximize nutrient gain from their carbon investment in root and mycorrhizal hyphae. Foraging strategies may depend on costs of root construction, with thick roots generally costing more per unit length than thin roots. Investment in mycorrhizal hyphae, which are considerably thinner than roots, may represent an alternative strategy for cost-effective nutrient foraging, especially for thick-root species. Type of mycorrhiza may matter, as ectomycorrhizal (EM) fungi are more associated with longer hyphae and ability to mineralize organic matter than arbuscular mycorrhizal (AM) fungi. Among AM trees in both subtropical forests in SE China and in temperate forests in central Pennsylvania, USA, we found that tree species with thin roots proliferated their roots in soil patches enriched with mineral nutrients to a greater extent than species with thick roots. In addition, thick-root species were consistently colonized more heavily with mycorrhizal fungi than thin root species, although nutrient addition tended to diminish colonization. In a common garden in central Pennsylvania of both AM and EM tree species, we found that nutrient patches enriched with organic materials resulted in greater root and mycorrhizal fungal proliferation compared to those enriched with inorganic nutrients and that thick-root species proliferated more with their mycorrhizal fungi whereas thin-root species proliferated more with their roots. We further examined with many more species, patterns of root and mycorrhizal fungal proliferation in organic-nutrient-enriched patches. Foraging precision, or the extent that roots or mycorrhizal hyphae grew in the enriched patch relative to the unenriched patch, was related to both root thickness and type of mycorrhiza. In both AM and EM trees, thick-root species were not selective foragers of either their roots or hyphae. In thin-root species, there was strong selectivity in

  4. Meta-analysis of crop and weed growth responses to arbuscular-mycorrhizal fungi

    USDA-ARS?s Scientific Manuscript database

    Arbuscular mycorrhizal fungi (AMF) have long been regarded as beneficial soil microorganisms, but have been reported to have detrimental effects on several non-mycorrhizal agricultural weed species. If AMF have negative effects on weeds but neutral or positive effects on crops under certain cropping...

  5. Increasing diveristy of arbuscular mycorrhizal fungi in agroecosystems using specific cover crops

    USDA-ARS?s Scientific Manuscript database

    Fall-planted cover crops provide a plant host for obligate symbiotic arbuscular mycorrhizal fungi (AMF) during otherwise fallow periods and thus may increase AMF numbers in agroecosystems. Increased AMF numbers should increase mycorrhizal colonization of the subsequent cash crops, which has been li...

  6. 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.

  7. Diet of Arbuscular Mycorrhizal Fungi: Bread and Butter?

    PubMed

    Rich, Mélanie K; Nouri, Eva; Courty, Pierre-Emmanuel; Reinhardt, Didier

    2017-08-01

    Most plants entertain mutualistic interactions known as arbuscular mycorrhiza (AM) with soil fungi (Glomeromycota) which provide them with mineral nutrients in exchange for reduced carbon from the plant. Mycorrhizal roots represent strong carbon sinks in which hexoses are transferred from the plant host to the fungus. However, most of the carbon in AM fungi is stored in the form of lipids. The absence of the type I fatty acid synthase (FAS-I) complex from the AM fungal model species Rhizophagus irregularis suggests that lipids may also have a role in nutrition of the fungal partner. This hypothesis is supported by the concerted induction of host genes involved in lipid metabolism. We explore the possible roles of lipids in the light of recent literature on AM symbiosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. 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.

  9. 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.

  10. [Interactions between invasive plants and arbuscular mycorrhizal fungi: a review].

    PubMed

    Bai, Yan-fang; Guo, Shao-xia; Li, Min

    2011-09-01

    The invasion of invasive plants changes the biological community structure in their invaded lands, leading to the biodiversity loss. As an important component of soil microorganisms in terrestrial ecosystem, arbuscular mycorrhizal (AM) fungi can affect the growth performance of invasive plants. This kind of specific relations between AM fungi and invasive plants also implies that AM fungi can affect plant invasion. On the other hand, the invasion of invasive plants can affect the community structure and function of AM fungi. This paper summarized the species and harms of invasive plants in China, and discussed the relationships between AM fungi and invasive plants invasion, including the roles of AM fungi in the processes of invasive plants invasion, the effects of the invasion on AM fungi, and the interactive mechanisms between the invasion and AM fungi.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Arbuscular mycorrhizal fungi ameliorate temperature stress in thermophilic plants.

    PubMed

    Bunn, Rebecca; Lekberg, Ylva; Zabinski, Catherine

    2009-05-01

    Biotic interactions can affect the distribution of species across environmental gradients, and as air and soil temperatures increase, plant community response may depend on interactions with symbionts. We measured the effect of elevated soil temperatures on mycorrhizal function and on the response of both plant and fungal symbionts, using fungal inoculum isolated from either high-temperature thermal or nonthermal grassland soils. Our source for thermal soils was Yellowstone National Park, USA, where plants experience rooting zone temperatures of 45 degrees C or more. In the greenhouse, we grew three plant species (Dichanthelium lanuginosum, Agrostis scabra, and Mimulus guttatus) with three arbuscular mycorrhizal fungal (AMF) treatments (no AMF, nonthermal AMF, thermal AMF) and two soil temperatures (ambient, elevated). Biomass of the facultative thermal plants Agrostis scabra and Mimulus guttatus decreased by 50% in elevated-temperature soils, and AMF had no effect on measured plant traits. In contrast, the biomass and total root length of the obligate thermal plant Dichanthelium lanuginosum were greater at elevated soil temperatures, but only when mycorrhizal. Both mycorrhizal colonization levels and length of extraradical hyphae (ERH) increased with soil temperature across all host species. The source of the AMF inoculum, on the other hand, did not affect colonization level, ERH length, host plant biomass, or flowering for all host species in either temperature treatment, suggesting that AMF from thermal soils are not specifically adapted to higher temperatures. In the field we collected soil cores to measure in situ depth distributions of D. lanuginosum roots and ERH, and to determine which AMF species were active in plants growing in thermal soils. Roots were limited to soils with an average temperature < or =30 degrees C, while ERH existed in the hottest soils we sampled, averaging 35 degrees C. Molecular analyses of roots indicated that thermal AMF

  17. 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.

  18. 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.

  19. Arbuscular mycorrhizal colonization in soil fertilized by organic and mineral fertilizers

    NASA Astrophysics Data System (ADS)

    Dvořáčková, Helena; Záhora, Jaroslav; Mikajlo, Irina; Elbl, Jakub; Kynický, Jindřich; Hladký, Jan; Brtnický, Martin

    2017-04-01

    The level of arbuscular mycorrhizal colonization of roots represents one of the best parameters for assessing soil quality. This special type of symbiosis helps plants to obtain nutrients of the distant area which are unavailable without cooperation with arbuscular mycorrhizal fungi. For example the plant available form of phosphorus is of the most important elements in plant nutrition. This element can't move (significantly) throw the soil and it could be unachievable for root system of plant. The same situation also applies to other important nutrients and water. Colonization of individual roots by arbuscular mycorrhizal fungi has a direct effect on the enlargement of the root system but plant needs to invest sugar substance for development of fungi. It's very difficult to understand when fungi colonization represents indicator of good soil condition. And when it provides us with information "about plant stress". The main goal of our work was to compare the effect of different fertilizers application on development of arbuscular mycorrhizal colonization. We worked with organic fertilizers such as biochar from residual biomass, biochar from sewage sludge and ageing biochar and with mineral fertilizer DAM 390 (mixture of ammonium 25 %, nitrate 25 % and urea nitrogen 50 %). Effect of different types of the above fertilizers on development of arbuscular mycorrhizal colonization was tested by pot experiment with indicator plant Lactuca sativa L. The highest (P < 0.05) colonization of roots was found in variant with biochar from sewage sludge. The lower colonization was recognized in control variant and variant with addition of mineral fertilizer. Our results indicate positive effect of modified biochar application to soil on increase in level of arbuscular mycorrhizal colonization of roots.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  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. Linking symbiont community structures in a model arbuscular mycorrhizal system.

    PubMed

    Meadow, James F; Zabinski, Catherine A

    2012-05-01

    • The influence of plant communities on symbiotic arbuscular mycorrhizal fungal (AMF) communities is difficult to study in situ as both symbionts are strongly influenced by some of the same soil and environmental conditions, and thus we have a poor understanding of the potential links in community composition and structure between host and fungal communities. • AMF were characterized in colonized roots of thermal soil Mimulus guttatus in both isolated plants supporting AMF for only a few months of the growing season and plants growing in mixed plant communities composed of annual and perennial hosts. Cluster and discriminant analysis were used to compare competing models based on either communities or soil conditions. • Mimulus guttatus in adjacent contrasting plant community situations harbored distinct AMF communities with few fungal taxa occurring in both community types. Isolated plants harbored communities of fewer fungal taxa with lower diversity than plants in mixed communities. Host community type was more indicative than pH of AMF community structure. • Our results support an inherent relationship between host plant and AMF community structures, although pH-based models were also statistically supported. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

  9. Arbuscular mycorrhizal fungal communities are phylogenetically clustered at small scales

    PubMed Central

    Horn, Sebastian; Caruso, Tancredi; Verbruggen, Erik; Rillig, Matthias C; Hempel, Stefan

    2014-01-01

    Next-generation sequencing technologies with markers covering the full Glomeromycota phylum were used to uncover phylogenetic community structure of arbuscular mycorrhizal fungi (AMF) associated with Festuca brevipila. The study system was a semi-arid grassland with high plant diversity and a steep environmental gradient in pH, C, N, P and soil water content. The AMF community in roots and rhizosphere soil were analyzed separately and consisted of 74 distinct operational taxonomic units (OTUs) in total. Community-level variance partitioning showed that the role of environmental factors in determining AM species composition was marginal when controlling for spatial autocorrelation at multiple scales. Instead, phylogenetic distance and spatial distance were major correlates of AMF communities: OTUs that were more closely related (and which therefore may have similar traits) were more likely to co-occur. This pattern was insensitive to phylogenetic sampling breadth. Given the minor effects of the environment, we propose that at small scales closely related AMF positively associate through biotic factors such as plant-AMF filtering and interactions within the soil biota. PMID:24824667

  10. 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.

  11. 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

  12. Arbuscular mycorrhizal fungal communities are phylogenetically clustered at small scales.

    PubMed

    Horn, Sebastian; Caruso, Tancredi; Verbruggen, Erik; Rillig, Matthias C; Hempel, Stefan

    2014-11-01

    Next-generation sequencing technologies with markers covering the full Glomeromycota phylum were used to uncover phylogenetic community structure of arbuscular mycorrhizal fungi (AMF) associated with Festuca brevipila. The study system was a semi-arid grassland with high plant diversity and a steep environmental gradient in pH, C, N, P and soil water content. The AMF community in roots and rhizosphere soil were analyzed separately and consisted of 74 distinct operational taxonomic units (OTUs) in total. Community-level variance partitioning showed that the role of environmental factors in determining AM species composition was marginal when controlling for spatial autocorrelation at multiple scales. Instead, phylogenetic distance and spatial distance were major correlates of AMF communities: OTUs that were more closely related (and which therefore may have similar traits) were more likely to co-occur. This pattern was insensitive to phylogenetic sampling breadth. Given the minor effects of the environment, we propose that at small scales closely related AMF positively associate through biotic factors such as plant-AMF filtering and interactions within the soil biota.

  13. Biofertilizers and sustainable agriculture: exploring arbuscular mycorrhizal fungi.

    PubMed

    Igiehon, Nicholas O; Babalola, Olubukola O

    2017-06-01

    Worldwide agricultural food production has to double in 2050 so as to feed the global increasing population while reducing dependency on conventional chemical fertilizers plus pesticides. To accomplish this objective, there is the need to explore the several mutualistic interactions between plant roots and rhizosphere microbiome. Biofertilization is the process of boosting the abundance of microorganisms such as arbuscular mycorrhizal fungi (AMF) in the natural plant rhizosphere which depicts a beneficial alternative to chemical fertilization practices. Mineral nutrients uptake by AMF are plausible by means of transporters coded for by different genes and example include phosphate transporter. These fungi can be produced industrially using plant host and these, including the possibility of AMF contamination by other microorganism, are factors militating against large scale production of AMF. AMF isolates can be inoculated in the greenhouse or field, and it has been shown that AMF survival and colonization level were enhanced in soybeans grown on land that was previously cultivated with the same plant. Next generation sequencing (NGS) is now used to gain insight into how AMF interact with indigenous AMF and screen for beneficial microbial candidates. Besides application as biofertilizers, novel findings on AMF that could contribute to maintenance of agricultural development include AMF roles in controlling soil erosion, enhancing phytoremediation, and elimination of other organisms that may be harmful to crops through common mycelia network. The combination of these potentials when fully harnessed under agricultural scenario will help to sustain agriculture and boost food security globally.

  14. Alleviation of drought stress of marigold (Tagetes erecta) plants by using arbuscular mycorrhizal fungi

    PubMed Central

    Asrar, Abdul-Wasea A.; Elhindi, Khalid M.

    2010-01-01

    The effect of an arbuscular mycorrhizal fungus “AMF” (Glomus constrictum Trappe) on growth, pigments, and phosphorous content of marigold (Tagetes erecta) plant grown under different levels of drought stress was investigated. The applied drought stress levels reduced growth vigor (i.e. plant height, shoot dry weight, flower diameter as well as its fresh and dry weights) of mycorrhizal and non-mycorrhizal plant as compared to control plant (non-drought stressed plant). The presence of mycorrhizal fungus, however, stimulated all growth parameters of the treated plant comparing to non-mycorrhizal treated plant. The photosynthetic pigments (carotene in flowers and chlorophylls a and b in leaves) were also stimulated by the mycorrhizal fungi of well-watered as well as of water-stressed plants. The total pigments of mycorrhizal plants grown under well-watered conditions were higher than those of non-mycorrhizal ones by 60%. In most cases, drought-stressed mycorrhizal plants were significantly better than those of the non-mycorrhizal plants. So, the overall results suggest that mycorrhizal fungal colonization affects host plant positively on growth, pigments, and phosphorous content, flower quality and thereby alleviates the stress imposed by water with holding. PMID:23961109

  15. Alleviation of drought stress of marigold (Tagetes erecta) plants by using arbuscular mycorrhizal fungi.

    PubMed

    Asrar, Abdul-Wasea A; Elhindi, Khalid M

    2011-01-01

    The effect of an arbuscular mycorrhizal fungus "AMF" (Glomus constrictum Trappe) on growth, pigments, and phosphorous content of marigold (Tagetes erecta) plant grown under different levels of drought stress was investigated. The applied drought stress levels reduced growth vigor (i.e. plant height, shoot dry weight, flower diameter as well as its fresh and dry weights) of mycorrhizal and non-mycorrhizal plant as compared to control plant (non-drought stressed plant). The presence of mycorrhizal fungus, however, stimulated all growth parameters of the treated plant comparing to non-mycorrhizal treated plant. The photosynthetic pigments (carotene in flowers and chlorophylls a and b in leaves) were also stimulated by the mycorrhizal fungi of well-watered as well as of water-stressed plants. The total pigments of mycorrhizal plants grown under well-watered conditions were higher than those of non-mycorrhizal ones by 60%. In most cases, drought-stressed mycorrhizal plants were significantly better than those of the non-mycorrhizal plants. So, the overall results suggest that mycorrhizal fungal colonization affects host plant positively on growth, pigments, and phosphorous content, flower quality and thereby alleviates the stress imposed by water with holding.

  16. 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.

  17. Gr and hp-1 tomato mutants unveil unprecedented interactions between arbuscular mycorrhizal symbiosis and fruit ripening.

    PubMed

    Chialva, Matteo; Zouari, Inès; Salvioli, Alessandra; Novero, Mara; Vrebalov, Julia; Giovannoni, James J; Bonfante, Paola

    2016-07-01

    Systemic responses to an arbuscular mycorrhizal fungus reveal opposite phenological patterns in two tomato ripening mutants depending whether ethylene or light reception is involved. The availability of tomato ripening mutants has revealed many aspects of the genetics behind fleshy fruit ripening, plant hormones and light signal reception. Since previous analyses revealed that arbuscular mycorrhizal symbiosis influences tomato berry ripening, we wanted to test the hypothesis that an interplay might occur between root symbiosis and fruit ripening. With this aim, we screened seven tomato mutants affected in the ripening process for their responsiveness to the arbuscular mycorrhizal fungus Funneliformis mosseae. Following their phenological responses we selected two mutants for a deeper analysis: Green ripe (Gr), deficient in fruit ethylene perception and high-pigment-1 (hp-1), displaying enhanced light signal perception throughout the plant. We investigated the putative interactions between ripening processes, mycorrhizal establishment and systemic effects using biochemical and gene expression tools. Our experiments showed that both mutants, notwithstanding a normal mycorrhizal phenotype at root level, exhibit altered arbuscule functionality. Furthermore, in contrast to wild type, mycorrhization did not lead to a higher phosphate concentration in berries of both mutants. These results suggest that the mutations considered interfere with arbuscular mycorrhiza inducing systemic changes in plant phenology and fruits metabolism. We hypothesize a cross talk mechanism between AM and ripening processes that involves genes related to ethylene and light signaling.

  18. 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.

  19. Predictors of Arbuscular Mycorrhizal Fungal Communities in the Brazilian Tropical Dry Forest.

    PubMed

    Sousa, Natália M F; Veresoglou, Stavros D; Oehl, Fritz; Rillig, Matthias C; Maia, Leonor C

    2017-08-04

    Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi with a broad distribution, and many taxa have physiological and ecological adaptations to specific environments, including semiarid ecosystems. Our aim was to address regional distribution patterns of AMF communities in such semiarid environments based on spore morphological techniques. We assessed AMF spores at the bottom and top of inselbergs distributed throughout the tropical dry forest in the Northeast region of Brazil. Across 10 replicate inselbergs and the surrounding area, spanning a range of altitude between 140 and 2000 m, we scored the AMF soil diversity and properties in 52 plots. We fitted parsimonious ordination analyses and variance partitioning models to determine the environmental factors which explained the variation in AMF community, based on morphological spore analysis. The diversity of AMF was similar at the bottom and top of inselbergs; however, we detected high variation in abundance and richness across sites. We formulated a parsimonious richness model that used physical soil factors as predictors. The AMF community structure could be best explained through the variables coarse and total sand, iron, organic matter, potassium, silt, and sodium which together accounted for 17.8% of total variance. Several AMF species were indicators of either deficiency or high values of specific soil properties. We demonstrated that habitat isolation of the inselbergs compared with surrounding areas did not trigger differences in AMF communities in semiarid regions of Brazil. At the regional scale, soil predictors across sites drove the distribution of symbiotic mycorrhizal fungi.

  20. 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.

  1. Arbuscular mycorrhizal infection in two morphological root types of Araucaria araucana (Molina) K. Koch.

    PubMed

    Diehl, P; Fontenla, S B

    2010-01-01

    Araucaria araucana (Molina) K. Koch is a conifer distributed in the Andean-Patagonian forests in the south of Argentina and Chile. The main objective of this work was to relate the different root classes appearing in A. araucana to mycorrhizal behavior. Samples were collected in three different sites in the Lanín National Park (NW Patagonia, Argentina). Two different root classes were present in A. araucana: longitudinal fine roots (LFR) and globular short roots (GSR). Both had extensive mycorrhizal arbuscular symbiosis (AM) and presented abundant hyphae and coils in root cells, a characteristic of the anatomical Paris-type. Dark septate fungal endophytes were also observed. Values of total AM colonization were high, with similar partial AM% values for each root class. Seasonal differences were found for total and partial colonization, with higher values in spring compared to autumn. Regarding the percentage of fungal structures between root classes, values were similar for vesicles and arbuscules, but higher coil percentages were observed in GSR compared to LFR. The percentages of vesicles increased in autumn, whereas the arbuscule percentages increased in spring, coinciding with the plant growth peak. Results show that both root classes of A. araucana in Andean-Patagonian forests are associated with AM fungi, which may have ecological relevance in terms of the importance of this symbiosis, in response to soil nutrient-deficiencies, especially high P-retention.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Influence of arbuscular mycorrhizal fungi on the growth and nutrient status of bermudagrass grown in alkaline bauxite processing residue.

    PubMed

    Giridhar Babu, A; Sudhakara Reddy, M

    2011-01-01

    A nursery experiment was conducted to evaluate the potential role of arbuscular mycorrhizal (AM) fungi in encouraging the vegetation cover on bauxite residue (red mud) sites. An alkali tolerant bermudagrass (Cynodon dactylon) adapted to local conditions were grown in red mud with different amendments with and without AM fungi to assess mycorrhizal effects on plant growth, mineral nutrition, metal uptake and neutralization of bauxite residue. Inoculation of AM fungi significantly increased the plant growth, nutrient uptake and reduced Fe, Al accumulation in plant tissue and also improved the soil physico-chemical and biochemical properties. Gypsum and sludge amended treatments inoculated with AM fungi had maximum biomass, nutrient uptake and reduced accumulation of metals. The neutralization of red mud was significant in presence of AM fungi than control. The experiment provided evidence for the potential use of bermudagrass in combination with AM fungi for ecological restoration of bauxite residue sites. Copyright © 2010 Elsevier Ltd. All rights reserved.

  8. 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. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. 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.

  10. Large-scale diversity patterns in spore communities of Arbuscular mycorrhizal fungi [Chapter 2

    Treesearch

    Javier Alvarez-Sanchez; Nancy C. Johnson; Anita Antoninka; V. Bala Chaudhary; Matthew K. Lau; Suzanne M. Owen; Patricia Gauadarrama; Silvia. Castillo

    2010-01-01

    Surprising little is known about the factors controlling Arbuscular Mycorrhizal (AM) fungal diversity and distribution patterns. A better understanding of these factors is necessary before mycorrhizas can be effectively managed for their benefits in ecosystem restoration and agriculture. The goal of this chapter is to examine the relationships between AM fungal...

  11. Simulated nitrogen deposition affects community structure of arbuscular mycorrhizal fungi in northern hardwood forests

    Treesearch

    Linda T.A. Van Diepen; Erik Lilleskov; Kurt S. Pregitzer

    2011-01-01

    Our previous investigation found elevated nitrogen deposition caused declines in abundance of arbuscular mycorrhizal fungi (AMF) associated with forest trees, but little is known about how nitrogen affects the AMF community composition and structure within forest ecosystems. We hypothesized that N deposition would lead to significant changes in the AMF community...

  12. Fungicidal seed coatings exert minor effects on arbuscular mycorrhizal fungi and plant nutrient content

    USDA-ARS?s Scientific Manuscript database

    Aims: Determine if contemporary, seed-applied fungicidal formulations inhibit colonization of plant roots by arbuscular mycorrhizal (AM) fungi, plant development, or plant nutrient content during early vegetative stages of several commodity crops. Methods: We evaluated seed-applied commercial fungic...

  13. Inoculation of fumigated nursery beds and containers with arbuscular mycorrhizal products for eastern redcedar production

    Treesearch

    Michelle M. Cram; Stephen W. Fraedrich

    2015-01-01

    Commercially available arbuscular mycorrhizal (AM) products were applied at an operational rate to eastern redcedar (Juniperus virginiana L.) nursery beds and containers to evaluate seedling growth and colonization responses. A field study at the Augusta Forestry Center in Crimora, VA, and a companion container study were initiated in the fall of 2012. MycoApply® Endo...

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

    USDA-ARS?s Scientific Manuscript database

    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...

  15. Impact of arbuscular mycorrhizal fungi on maize physiology and biochemical response under variable nitrogen levels

    USDA-ARS?s Scientific Manuscript database

    Arbuscular mycorrhizal (AM) fungi are known for colonizing plant roots, transporting water and nutrients from the soil to the plant. Therefore, environmental conditions set mainly by soil water and nutrient levels are important determinants of AM function and host plant response. Mechanisms of nitro...

  16. Carbon availability for the fungus triggers nitrogen uptake and transport in the arbuscular mycorrhizal symbiosis

    USDA-ARS?s Scientific Manuscript database

    The arbuscular mycorrhizal (AM) symbiosis is characterized by a transfer of nutrients in exchange for carbon. We tested the effect of the carbon availability for the AM fungus Glomus intraradices on nitrogen (N) uptake and transport in the symbiosis. We followed the uptake and transport of 15N and ...

  17. Impacts of farm management upon arbuscular mycorrhizal fungi and production and utilization of inoculum

    USDA-ARS?s Scientific Manuscript database

    Arbuscular mycorrhizal [AM] fungi are naturally-occurring soil fungi that form a mutualistic symbiosis with the roots of most crop plants. The plant benefits through increased: nutrient uptake from the soil, disease resistance, and water stress resistance. Optimal utilization of AM fungi is essen...

  18. Decline of arbuscular mycorrhizal fungi in northern hardwood forests exposed to chronic nitrogen additions

    Treesearch

    Linda T.A. van Diepen; Erik A. Lilleskov; Kurt S. Pregitzer; R. Michael Miller

    2007-01-01

    Arbuscular mycorrhizal (AM) fungi are important below-ground carbon (C) sinks that can be sensitive to increased nitrogen (N) availability. The abundance of AM fungi (AMF) was estimated in maple (Acer spp.) fine roots following more than a decade of experimental additions of N designed to simulate chronic atmospheric N deposition.

  19. Ink and Vinegar, a Simple Staining Technique for Arbuscular-Mycorrhizal Fungi

    PubMed Central

    Vierheilig, Horst; Coughlan, Andrew P.; Wyss, Urs; Piché, Yves

    1998-01-01

    We developed a reliable, inexpensive, and simple method for staining arbuscular-mycorrhizal fungal colonizations in root tissues. Apart from applications in research, this nontoxic, high-quality staining method also could be of great utility in teaching exercises. After adequate clearing with KOH, an ink-vinegar solution successfully stained all fungal structures, rendering them clearly visible. PMID:9835596

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

    USDA-ARS?s Scientific Manuscript database

    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 ...

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

    USDA-ARS?s Scientific Manuscript database

    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...

  2. PAHs pass through the cell wall and partition into organelles of arbuscular mycorrhizal roots of ryegrass.

    PubMed

    Gao, Yanzheng; Cao, Xuezhang; Kang, Fuxing; Cheng, Zhaoxia

    2011-01-01

    The subcellular process and distribution of polycyclic aromatic hydrocarbons (PAHs) in arbuscular mycorrhizal plants remains to be elucidated. This work used a greenhouse experiment to show that, accompanied by the apoplastic and symplastic water movement through the root, acenaphthene (ACE) as a representative PAH passed through the cell-wall boundary, dissolved in the cell solution, and partition organelles in arbuscular mycorrhizal roots of ryegrass (Lolium multiflorum Lam.). The observed concentrations of ACE in organelles were 0.6 to 4.4 times higher than in the cell walls. The cell wall and organelles were the dominant storage domains for ACE in the root, and the distribution of ACE in cells of mycorrhizal ryegrass roots was, in descending order, cell organelles (40.8-70.8%) > cell wall (19.7-3.8%) cell solution (9.6-20.5%).

  3. 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.

  4. 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

  5. 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

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

    PubMed

    Alguacil, Maria Del Mar; Torres, Maria Pilar; Montesinos-Navarro, Alicia; Roldán, Antonio

    2016-06-01

    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. 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) were the main factors

  7. 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

  8. Quantification of the proliferation of arbuscular mycorrhizal fungi in soil

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Lilje, Osu; McGee, Peter

    2013-04-01

    Good soil structure is important for sustaining agricultural production and preserving functions of the soil ecosystem. Soil aggregation is a critically important component of soil structure. Stable aggregates enable water infiltration, gas exchange for biological activities of plant roots and microorganisms, living space and surfaces for soil microbes, and contribute to stabilization of organic matter and storage of organic carbon (OC) in soil. Soil aggregation involves fine roots, organic matter and hyphae of arbuscular mycorrhizal (AM) fungi. Hyphal proliferation is essential for soil aggregation and sequestration of OC in soil. We do not yet have a mechanism to directly quantify the density of hyphae in soil. Organic materials and available phosphorus are two of the major factors that influence fungi in soil. Organic materials are a source of energy for saprotrophic microbes. Fungal hyphae increase in the presence of organic matter. Phosphorus is an important element usually found in ecosystems. The low availability of phosphorus limits the biological activity of microbes. AM fungi benefit plants by delivering phosphorus to the root system. However, the density and the length of hyphae of AM fungi do not appear to be influenced by available phosphorus. A number of indirect methods have been used to visualize distribution of fungi in soil. Reliable analyses of soil are limited because of soil characteristics. Soils are fragile, and fragility limits opportunity for non-destructive analysis. The soil ecosystem is complex. Soil particles are dense and the density obscures the visualization of fungal hyphae. Fungal hyphae are relatively fine and information at the small scale (<250µm) is key to understanding how fungi respond to environmental stimuli. This experiment tested whether organic carbon (starch), phosphorus (K2HPO4) and their mixture influences proliferation of hyphae of AM fungi. Hyphae were quantified in an artificial soil matrix using micro

  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. Arbuscular mycorrhizal fungi (AMF) improved growth and nutritional quality of greenhouse-grown lettuce.

    PubMed

    Baslam, Marouane; Garmendia, Idoia; Goicoechea, Nieves

    2011-05-25

    Lettuce can be associated with arbuscular mycorrhizal fungi (AMF). This symbiosis involves a molecular dialogue between fungus and plant that includes the activation of antioxidant, phenylpropanoid, or carotenoid pathways. The objective of this study was to test if the association of lettuce with AMF benefited plant growth and increased the contents of compounds potentially beneficial for human health. Results showed that AMF improved growth of lettuce, thus producing a dilution effect on the concentrations of some mineral nutrients (e.g., Ca and Mn). However, Cu, Fe, anthocyanins, carotenoids, and, to a lesser extent, phenolics appeared in higher concentrations (on a wet basis) in mycorrhizal than in nonmycorrhizal plants.

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

    PubMed

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

    2009-05-13

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

  13. Nitrogen isotope fractionation during N uptake via arbuscular mycorrhizal and ectomycorrhizal fungi into grey alder.

    PubMed

    Schweiger, Peter F

    2016-10-20

    Arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi affect plant nitrogen (N) dynamics. Plant N isotope patterns have been used to characterise the contribution of ECM fungi to plant N uptake. By quantifying and comparing the effects of an AM and an ECM fungus on growth, N uptake and isotopic composition of one host plant grown at different relative N supply levels, the aim of this study was to improve the mechanistic understanding of natural (15)N abundance patterns in mycorrhizal plants and their underlying causes. Grey alders were inoculated with one ECM fungus or one AM fungus or left non-mycorrhizal. Plants were grown under semi-hydroponic conditions and were supplied with three rates of relative N supply ranging from deficient to luxurious. Neither mycorrhizal fungus increased plant growth or N uptake. AM root colonisation had no effect on whole plant δ(15)N and decreased foliar δ (15)N only under N deficiency. The roots of these plants were (15)N-enriched. ECM root colonisation consistently decreased foliar and whole plant δ(15)N. It is concluded, that both mycorrhizal fungi contributed to plant N uptake into the shoot. Nitrogen isotope fractionation during N assimilation and transformations in fungal mycelia is suggested to have resulted in plants receiving (15)N-depleted N via the mycorrhizal uptake pathways. Negative mycorrhizal growth effects are explained by symbiotic resource trade on carbon and N and decreased direct plant N uptake. Copyright © 2016 Elsevier GmbH. All rights reserved.

  14. 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.

  15. Arbuscular mycorrhizal colonization has little consequence for plant heavy metal uptake in contaminated field soils.

    PubMed

    Dietterich, Lee H; Gonneau, Cédric; Casper, Brenda B

    2017-09-01

    The factors affecting plant uptake of heavy metals from metalliferous soils are deeply important to the remediation of polluted areas. Arbuscular mycorrhizal fungi (AMF), soil-dwelling fungi that engage in an intimate exchange of nutrients with plant roots, are thought to be involved in plant metal uptake as well. Here, we used a novel field-based approach to investigate the effects of AMF on plant metal uptake from soils in Palmerton, Pennsylvania, USA contaminated with heavy metals from a nearby zinc smelter. Previous studies often focus on one or two plant species or metals, tend to use highly artificial growing conditions and metal applications, and rarely consider metals' effects on plants and AMF together. In contrast, we examined both direct and AMF-mediated effects of soil concentrations on plant concentrations of 8-13 metals in five wild plant species sampled across a field site with continuous variation in Zn, Pb, Cd, and Cu contamination. Plant and soil metal concentration profiles were closely matched despite high variability in soil metal concentrations even at small spatial scales. However, we observed few effects of soil metals on AMF colonization, and no effects of AMF colonization on plant metal uptake. Manipulating soil chemistry or plant community composition directly may control landscape-level plant metal uptake more effectively than altering AMF communities. Plant species identities may serve as highly local indicators of soil chemical characteristics. © 2017 by the Ecological Society of America.

  16. Exploring the symbiont diversity of ancient western redcedars: arbuscular mycorrhizal fungi of long-lived hosts.

    PubMed

    Gorzelak, Monika A; Pickles, Brian J; Hart, Miranda M

    2017-03-01

    Arbuscular mycorrhizal fungi (AMF) are globally distributed, monophyletic root symbionts with ancient origins. Their contribution to carbon cycling and nutrient dynamics is ecologically important, given their obligate association with over 70% of vascular plant species. Current understanding of AMF species richness and community structure is based primarily on studies of grasses, herbs and agricultural crops, typically in disturbed environments. Few studies have considered AMF interactions with long-lived woody perennial species in undisturbed ecosystems. Here we examined AMF communities associated with roots and soils of young, mature and old western redcedar (Thuja plicata) at two sites in the old-growth temperate rainforests of British Columbia. Due to the unique biology of AMF, community richness and structure were assessed using a conservative, clade-based approach. We found 91 AMF OTUs across all samples, with significantly greater AMF richness in the southern site, but no differences in richness along the host chronosequence at either site. All host age classes harboured AMF communities that were overdispersed (more different to each other than expected by chance), with young tree communities most resembling old tree communities. A comparison with similar clade richness data obtained from the literature indicates that western redcedar AMF communities are as rich as those of grasses, tropical trees and palms. Our examination of undisturbed temperate old-growth rainforests suggests that priority effects, rather than succession, are an important aspect of AMF community assembly in this ecosystem. © 2017 John Wiley & Sons Ltd.

  17. Phylogenetic trait conservatism and the evolution of functional trade-offs in arbuscular mycorrhizal fungi

    PubMed Central

    Powell, Jeff R.; Parrent, Jeri L.; Hart, Miranda M.; Klironomos, John N.; Rillig, Matthias C.; Maherali, Hafiz

    2009-01-01

    The diversity of functional and life-history traits of organisms depends on adaptation as well as the legacy of shared ancestry. Although the evolution of traits in macro-organisms is well studied, relatively little is known about character evolution in micro-organisms. Here, we surveyed an ancient and ecologically important group of microbial plant symbionts, the arbuscular mycorrhizal (AM) fungi, and tested hypotheses about the evolution of functional and life-history traits. Variation in the extent of root and soil colonization by AM fungi is constrained to a few nodes basal to the most diverse groups within the phylum, with relatively little variation associated with recent divergences. We found no evidence for a trade-off in biomass allocated to root versus soil colonization in three published glasshouse experiments; rather these traits were positively correlated. Partial support was observed for correlated evolution between fungal colonization strategies and functional benefits of the symbiosis to host plants. The evolution of increased soil colonization was positively correlated with total plant biomass and shoot phosphorus content. Although the effect of AM fungi on infection by root pathogens was phylogenetically conserved, there was no evidence for correlated evolution between the extent of AM fungal root colonization and pathogen infection. Variability in colonization strategies evolved early in the diversification of AM fungi, and we propose that these strategies were influenced by functional interactions with host plants, resulting in an evolutionary stasis resembling trait conservatism. PMID:19740877

  18. 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.

  19. 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.

  20. 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.

  1. 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. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  2. 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. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  3. Quantification of arbuscular mycorrhizal fungal DNA in roots: how important is material preservation?

    PubMed

    Janoušková, Martina; Püschel, David; Hujslová, Martina; Slavíková, Renata; Jansa, Jan

    2015-04-01

    Monitoring populations of arbuscular mycorrhizal fungi (AMF) in roots is a pre-requisite for improving our understanding of AMF ecology and functioning of the symbiosis in natural conditions. Among other approaches, quantification of fungal DNA in plant tissues by quantitative real-time PCR is one of the advanced techniques with a great potential to process large numbers of samples and to deliver truly quantitative information. Its application potential would greatly increase if the samples could be preserved by drying, but little is currently known about the feasibility and reliability of fungal DNA quantification from dry plant material. We addressed this question by comparing quantification results based on dry root material to those obtained from deep-frozen roots of Medicago truncatula colonized with Rhizophagus sp. The fungal DNA was well conserved in the dry root samples with overall fungal DNA levels in the extracts comparable with those determined in extracts of frozen roots. There was, however, no correlation between the quantitative data sets obtained from the two types of material, and data from dry roots were more variable. Based on these results, we recommend dry material for qualitative screenings but advocate using frozen root materials if precise quantification of fungal DNA is required.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Which role can arbuscular mycorrhizal fungi play in the facilitation of Ambrosia artemisiifolia L. invasion in France?

    PubMed

    Fumanal, B; Plenchette, C; Chauvel, B; Bretagnolle, F

    2006-12-01

    Ambrosia artemisiifolia L. (common ragweed), an annual invasive plant, was introduced more than 100 years ago from North America to Europe. Like the majority of other invasive plants in Europe, it develops in open, disturbed areas such as fields, wastelands, roadsides, and riverbanks. Recently, arbuscular mycorrhizal fungi (AMF) have been suspected to play a role in some plant invasion processes. As the common ragweed is known to be colonized by AMF in its native range, the intensity of mycorrhizal root colonization was studied in 35 natural populations in eastern France. About 94% of the A. artemisiifolia populations sampled were mycorrhizal. Root colonization levels varied from 1 to 40% depending on the ecological sites, with lower levels for agricultural habitats and higher levels in disturbed sites, such as wastelands or roadsides. A subsequent greenhouse experiment showed positive impacts of AMF on the growth and development of A. artemisiifolia. It is proposed that the spread of this invasive plant species could be facilitated by AMF, underlining the need to integrate symbiotic interactions in future work on invasive plant processes.

  9. Dependence of Arbuscular-Mycorrhizal Fungi on Their Plant Host for Palmitic Acid Synthesis

    PubMed Central

    Trépanier, Martin; Bécard, Guillaume; Moutoglis, Peter; Willemot, Claude; Gagné, Serge; Avis, Tyler J.; Rioux, Jacques-André

    2005-01-01

    Lipids are the major form of carbon storage in arbuscular-mycorrhizal fungi. We studied fatty acid synthesis by Glomus intraradices and Gigaspora rosea. [14C]Acetate and [14C]sucrose were incorporated into a synthetic culture medium to test fatty acid synthetic ability in germinating spores (G. intraradices and G. rosea), mycorrhized carrot roots, and extraradical fungal mycelium (G. intraradices). Germinating spores and extraradical hyphae could not synthesize 16-carbon fatty acids but could elongate and desaturate fatty acids already present. The growth stimulation of germinating spores by root exudates did not stimulate fatty acid synthesis. 16-Carbon fatty acids (16:0 and 16:1) were synthesized only by the fungi in the mycorrhized roots. Our data strongly suggest that the fatty acid synthase activity of arbuscular-mycorrhizal fungi is expressed exclusively in the intraradical mycelium and indicate that fatty acid metabolism may play a major role in the obligate biotrophism of arbuscular-mycorrhizal fungi. PMID:16151123

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. Extracellular polysaccharides are involved in the attachment of Azospirillum brasilense and Rhizobium leguminosarum to arbuscular mycorrhizal structures.

    PubMed

    Bianciotto, V; Andreotti, S; Balestrini, R; Bonfante, P; Perotto, S

    2001-01-01

    Arbuscular mycorrhizal (AM) fungi, one of the most important component of the soil microbial community, establish physical interactions with naturally occurring and genetically modified bacterial biofertilizers and biopesticides, commonly referred to as plant growth-promoting rhizobacteria (PGPR). We have used a genetic approach to investigate the bacterial components possibly involved in the attachment of two PGPR (Azospirillum and Rhizobium) to AM roots and AM fungal structures. Mutants affected in extracellular polysaccharides (EPS) have been tested in in vitro adhesion assays and shown to be strongly impaired in the attachment to both types of surfaces as well as to quartz fibers. Anchoring of rhizobacteria to AM fungal structures may have special ecological and biotechnological significance because it may facilitate colonisation of new rhizospheres by the bacteria, and may be an essential trait for the development of mixed inocula.

  18. Does responsiveness to arbuscular mycorrhizal fungi depend on plant invasive status?

    PubMed

    Reinhart, Kurt O; Lekberg, Ylva; Klironomos, John; Maherali, Hafiz

    2017-08-01

    Differences in the direction and degree to which invasive alien and native plants are influenced by mycorrhizal associations could indicate a general mechanism of plant invasion, but whether or not such differences exist is unclear. Here, we tested whether mycorrhizal responsiveness varies by plant invasive status while controlling for phylogenetic relatedness among plants with two large grassland datasets. Mycorrhizal responsiveness was measured for 68 taxa from the Northern Plains, and data for 95 taxa from the Central Plains were included. Nineteen percent of taxa from the Northern Plains had greater total biomass with mycorrhizas while 61% of taxa from the Central Plains responded positively. For the Northern Plains taxa, measurable effects often depended on the response variable (i.e., total biomass, shoot biomass, and root mass ratio) suggesting varied resource allocation strategies when roots are colonized by arbuscular mycorrhizal fungi. In both datasets, invasive status was nonrandomly distributed on the phylogeny. Invasive taxa were mainly from two clades, that is, Poaceae and Asteraceae families. In contrast, mycorrhizal responsiveness was randomly distributed over the phylogeny for taxa from the Northern Plains, but nonrandomly distributed for taxa from the Central Plains. After controlling for phylogenetic similarity, we found no evidence that invasive taxa responded differently to mycorrhizas than other taxa. Although it is possible that mycorrhizal responsiveness contributes to invasiveness in particular species, we find no evidence that invasiveness in general is associated with the degree of mycorrhizal responsiveness. However, mycorrhizal responsiveness among species grown under common conditions was highly variable, and more work is needed to determine the causes of this variation.

  19. 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.

  20. 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.

  1. Arbuscular mycorrhizal induced changes to plant growth and root system morphology in Prunus cerasifera.

    PubMed

    Berta, G; Trotta, A; Fusconi, A; Hooker, J E; Munro, M; Atkinson, D; Giovannetti, M; Morini, S; Fortuna, P; Tisserant, B; Gianinazzi-Pearson, V; Gianinazzi, S

    1995-05-01

    We compared root system morphogenesis of micropropogated transplants of Prunus cerasifera L. inoculated with either of the arbuscular mycorrhizal (AM) fungi Glomus mosseae or Glomus intraradices or with the ericoid mycorrhizal species Hymenoscyphus ericae. All plants were grown in sand culture, irrigated with a nutrient solution that included a soluble source of phosphorus, for 75 days after transplanting. Arbuscular mycorrhizal colonization increased both the survival and growth (by over 100%) of transplants compared with either uninoculated controls or transplants inoculated with H. ericae. Arbuscular mycorrhizal colonization increased root, stem and leaf weights, leaf area, root length and specific leaf area, and it decreased root length/leaf area ratio, root/shoot weight ratio and specific root length. Both uptake of phosphorus and its concentration in leaves were increased by AM infection, although the time course of the relationships between intensity of AM infection and P nutrition were complex and suggested a role for factors other than nutrition. The time course for the development of infection varied. It was most rapid with G. mosseae, but it was ultimately higher with G. intraradices. None of the treatments significantly affected the lengths of adventitious roots or the first-, second- or third-order laterals that developed from them. Arbuscular mycorrhizal colonization increased the intensity of branching in all root orders with the effect being most obvious on first-order lateral roots where the number of branches increased from under 100 to over 300 brances m(-1). As a result, although first-order laterals made up 55% of the root systems of control plants, the comparable value was 36% in AM-infected plants. In contrast, second-order laterals represented 25% of control root systems, but 50% of AM-colonized root systems. Glomus intraradices but not G. mosseae increased root diameter. Anatomical studies revealed no changes in the overall form of the root

  2. Quality of rooting environments and patterns of root colonization by arbuscular mycorrhizal fungi in strangler figs in a Mexican palmetto woodland.

    PubMed

    Guevara, Roger; López, Juan C

    2007-10-01

    Arbuscular mycorrhizal colonization in strangler figs, spore richness, and abundance of arbuscular mycorrhizal fungi were quantified in epiphytic and ground-rooted trees in a Sabal palmetto woodland that had marked heterogeneity in rooting environments for hemiepiphytic plants. An inoculation experiment was performed to assess whether low spore density could limit mycorrhizal colonization. There was no significant difference in mycorrhizal colonization among Ficus species, but epiphytic plants in nutrient-rich rooting environments had less mycorrhizal colonization than ground-rooted plants in low-nutrient soils. However, richness and abundance of spores was low, and to some extent, this limited the mycorrhizal colonization of strangler figs. Nevertheless, our results suggest intraindividual adjusting levels of root colonization in strangler figs in accordance with mineral availability. Such responses could maximize the cost-benefit balance of arbuscular mycorrhizal interactions throughout the development of strangler figs from epiphytic young plants to ground-rooted trees.

  3. 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

  4. Microbial activity, arbuscular mycorrhizal fungi and inoculation of woody plants in lead contaminated soil

    PubMed Central

    Gattai, Graziella S.; Pereira, Sônia V.; Costa, Cynthia M. C.; Lima, Cláudia E. P.; Maia, Leonor C.

    2011-01-01

    The goals of this study were to evaluate the microbial activity, arbuscular mycorrhizal fungi and inoculation of woody plants (Caesalpinia ferrea, Mimosa tenuiflora and Erythrina velutina) in lead contaminated soil from the semi-arid region of northeastern of Brazil (Belo Jardim, Pernambuco). Dilutions were prepared by adding lead contaminated soil (270 mg Kg-1) to uncontaminated soil (37 mg Pb Kg soil-1) in the proportions of 7.5%, 15%, and 30% (v:v). The increase of lead contamination in the soil negatively influenced the amount of carbon in the microbial biomass of the samples from both the dry and rainy seasons and the metabolic quotient only differed between the collection seasons in the 30% contaminated soil. The average value of the acid phosphatase activity in the dry season was 2.3 times higher than observed during the rainy season. There was no significant difference in the number of glomerospores observed between soils and periods studied. The most probable number of infective propagules was reduced for both seasons due to the excess lead in soil. The mycorrhizal colonization rate was reduced for the three plant species assayed. The inoculation with arbuscular mycorrhizal fungi benefited the growth of Erythrina velutina in lead contaminated soil. PMID:24031701

  5. Inhibitory effect of TiO2 NPs on symbiotic arbuscular mycorrhizal fungi in plant roots.

    PubMed

    Priyanka, Karathan Parakkandi; Harikumar, Variampally Sankar; Balakrishna, Kagalagodu Manjunthiah; Varghese, Thomas

    2017-02-01

    While nanoparticles (NPs) are known to exhibit antimicrobial properties, their effects on symbiotic arbuscular mycorrhizal fungi (AMF) in plant roots has to be carefully examined as NPs particularly of titanium dioxide (TiO2) reach plant roots through varied sources such as fertilisers, plant protection products and other nanoproducts. The objective of the present study is to assess the effect of TiO2 NPs on the symbiotic behaviour of AMF colonising rice (Oryza sativa L.) plants. Using sol-gel method, TiO2 NPs with three different sizes were successfully synthesised employing doping. Characterisation of the prepared material was done by X-ray powder diffraction and scanning electron microscopy. The synthesised materials were applied at 0, 25, 50 and 100 mg plant-1 to the rhizosphere of mycorrhizal rice plants maintained in pots. The study revealed that the prepared NPs had an inhibitory effect on arbuscular mycorrhizal symbiosis in plant roots. Development of AMF structures such as vesicles and arbuscules was significantly reduced in TiO2-doped NPs with a relatively more inhibition in 2% TiO2-doped NPs. Among the concentrations of TiO2 NPs applied to different treatments, %F was significantly (P < 0.001) affected at medium to higher levels of application.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Phosphorus-32 absorption and translocation to host plants by arbuscular mycorrhizal fungi at low root-zone temperature.

    PubMed

    Wang, B; Funakoshi, D M; Dalpé, Y; Hamel, C

    2002-04-01

    Arbuscular mycorrhizal (AM) mycelia persist in soil over winter. Functioning of the AM symbiosis very early in the spring when the soil temperature is low may be of ecological significance for perennial and biannual plants in cool climates. An indoor experiment was conducted to investigate the effects of low root-zone temperatures on 32P uptake by 10-week-old leek plants (Allium porrum L.) inoculated or not with the AM fungus Glomus intraradices Schenck & Smith. Plants were grown in a greenhouse at approximately 23 degrees C prior to exposing their roots to 23 degrees C, 15 degrees C or 0 degree C. Mycorrhizal colonization increased 32P activity of leek leaves at a root-zone temperature of 23 degrees C seven days after injection of 32P into the soil, whereas 14 days after injection, 32P increases were measured at both 23 degrees C and 15 degrees C. The lack of difference in 32P activity between AM and non-AM plants at 0 degree C, both 7 and 14 days after injection, suggests that the AM fungus is not functional at this low root-zone temperature.

  14. Beyond nutrients: a meta-analysis of the diverse effects of arbuscular mycorrhizal fungi on plants and soils.

    PubMed

    Delavaux, Camille S; Smith-Ramesh, Lauren M; Kuebbing, Sara E

    2017-08-01

    Arbuscular mycorrhizal fungi (AMF) can increase plant fitness under certain environmental conditions. Among the mechanisms that may drive this mutualism, the most studied is provisioning of nutrients by AMF in exchange for carbon from plant hosts. However, AMF may also provide a suite of non-nutritional benefits to plants including improved water uptake, disease resistance, plant chemical defense, soil aggregation, and allelochemical transport and protection. Here, we use a meta-analysis of 93 studies to assess the relative effect of AMF on nutritional and non-nutritional factors that may influence plant fitness. We find that the positive effects of AMF on soil aggregation, water flow and disease resistance are equal to the effect of AMF on plant nitrogen and phosphorus uptake. However, AMF had no effect on the uptake of other nutrients, plant water content, allelopathic transport or production of chemical defense compounds. We suggest future research directions, including experimentally assessing the relative contribution on plant fitness of AMF interactions by untangling the independence of alternative benefits of AMF from an increase in nutrient uptake. This will lead to a more holistic view of the mycorrhizal-plant association and a more accurate picture of the net impact on the plant or plant community in question. © 2017 by the Ecological Society of America.

  15. Root Age-Dependent Changes in Arbuscular Mycorrhizal Fungal Communities Colonizing Roots of Panax ginseng.

    PubMed

    Kil, Yi-Jong; Eo, Ju-Kyeong; Lee, Eun-Hwa; Eom, Ahn-Heum

    2014-12-01

    In this study, we examined arbuscular mycorrhizal fungal (AMF) community structure colonizing field-cultivated ginseng roots according of different ages, such as 1- to 5-year-old plant, collected from Geumsan-gun, Korea. A total of seven AMF species namely, Funnelliformis caledonium, F. moseae, Gigaspora margarita, Paraglomus laccatum, P. occultum, Rhizophagus irregularis, and Scutellospora heterogama were identified from the roots using cloning, PCR-restriction fragment length polymorphism and sequence analysis of the large subunit region in rDNA. AMF species diversity in the ginseng roots decreased with the increase in root age because of the decreased species evenness. In addition, the community structures of AMF in the roots became more uniform. These results suggest that the age of ginseng affects mycorrhizal colonization and its community structure.

  16. Root Age-Dependent Changes in Arbuscular Mycorrhizal Fungal Communities Colonizing Roots of Panax ginseng

    PubMed Central

    Kil, Yi-Jong; Eo, Ju-Kyeong; Lee, Eun-Hwa

    2014-01-01

    In this study, we examined arbuscular mycorrhizal fungal (AMF) community structure colonizing field-cultivated ginseng roots according of different ages, such as 1- to 5-year-old plant, collected from Geumsan-gun, Korea. A total of seven AMF species namely, Funnelliformis caledonium, F. moseae, Gigaspora margarita, Paraglomus laccatum, P. occultum, Rhizophagus irregularis, and Scutellospora heterogama were identified from the roots using cloning, PCR-restriction fragment length polymorphism and sequence analysis of the large subunit region in rDNA. AMF species diversity in the ginseng roots decreased with the increase in root age because of the decreased species evenness. In addition, the community structures of AMF in the roots became more uniform. These results suggest that the age of ginseng affects mycorrhizal colonization and its community structure. PMID:25606018

  17. 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.

  18. The plasma membrane proteome of Medicago truncatula roots as modified by arbuscular mycorrhizal symbiosis.

    PubMed

    Aloui, Achref; Recorbet, Ghislaine; Lemaître-Guillier, Christelle; Mounier, Arnaud; Balliau, Thierry; Zivy, Michel; Wipf, Daniel; Dumas-Gaudot, Eliane

    2017-07-19

    In arbuscular mycorrhizal (AM) roots, the plasma membrane (PM) of the host plant is involved in all developmental stages of the symbiotic interaction, from initial recognition to intracellular accommodation of intra-radical hyphae and arbuscules. Although the role of the PM as the agent for cellular morphogenesis and nutrient exchange is especially accentuated in endosymbiosis, very little is known regarding the PM protein composition of mycorrhizal roots. To obtain a global overview at the proteome level of the host PM proteins as modified by symbiosis, we performed a comparative protein profiling of PM fractions from Medicago truncatula roots either inoculated or not with the AM fungus Rhizophagus irregularis. PM proteins were isolated from root microsomes using an optimized discontinuous sucrose gradient; their subsequent analysis by liquid chromatography followed by mass spectrometry (MS) identified 674 proteins. Cross-species sequence homology searches combined with MS-based quantification clearly confirmed enrichment in PM-associated proteins and depletion of major microsomal contaminants. Changes in protein amounts between the PM proteomes of mycorrhizal and non-mycorrhizal roots were monitored further by spectral counting. This workflow identified a set of 82 mycorrhiza-responsive proteins that provided insights into the plant PM response to mycorrhizal symbiosis. Among them, the association of one third of the mycorrhiza-responsive proteins with detergent-resistant membranes pointed at partitioning to PM microdomains. The PM-associated proteins responsive to mycorrhization also supported host plant control of sugar uptake to limit fungal colonization, and lipid turnover events in the PM fraction of symbiotic roots. Because of the depletion upon symbiosis of proteins mediating the replacement of phospholipids by phosphorus-free lipids in the plasmalemma, we propose a role of phosphate nutrition in the PM composition of mycorrhizal roots.

  19. The importance of integration and scale in the arbuscular mycorrhizal symbiosis.

    SciTech Connect

    Miller, R. M.; Kling, M.; Environmental Research; Swedish Univ. of Agricultural Sciences

    2000-01-01

    The arbuscular mycorrhizal (AM) fungus contributes to system processes and functions at various hierarchical organizational levels, through their establishment of linkages and feedbacks between whole-plants and nutrient cycles. Even though these fungal mediated feedbacks and linkages involve lower-organizational level processes (e.g. photo-assimilate partitioning, interfacial assimilate uptake and transport mechanisms, intraradical versus extraradical fungal growth), they influence higher-organizational scales that affect community and ecosystem behavior (e.g. whole-plant photosynthesis, biodiversity, nutrient and carbon cycling, soil structure). Hence, incorporating AM fungi into research directed at understanding many of the diverse environmental issues confronting society will require knowledge of how these fungi respond to or initiate changes in vegetation dynamics, soil fertility or both. Within the last few years, the rapid advancement in the development of analytical tools has increased the resolution by which we are able to quantify the mycorrhizal symbiosis. It is important that these tools are applied within a conceptual framework that is temporally and spatially relevant to fungus and host. Unfortunately, many of the studies being conducted on the mycorrhizal symbiosis at lower organizational scales are concerned with questions directed solely at understanding fungus or host without awareness of what the plant physiologist or ecologist needs for integrating the mycorrhizal association into larger organizational scales or process levels. We show by using the flow of C from plant-to-fungus-to-soil, that through thoughtful integration, we have the ability to bridge different organizational scales. Thus, an essential need of mycorrhizal research is not only to better integrate the various disciplines of mycorrhizal research, but also to identify those relevant links and scales needing further investigation for understanding the larger-organizational level

  20. Survival strategies of plants associated with arbuscular mycorrhizal fungi on toxic mine tailings.

    PubMed

    Leung, H M; Ye, Z H; Wong, M H

    2007-01-01

    A field survey of metal concentrations and arbuscular mycorrhizal (AM) components of plants growing on five mining sites was conducted in Chenzhou City, Hunan Province, Southern China and a control site in Hong Kong. Significant differences were observed in the average concentrations of total heavy metals (Pb, Zn, Cu, Cd) and one metalloid (As) in contaminated soils compared with the control site. Gramineae and Compositae were the dominant plant families growing on mine tailings, with Chrysanthemum moritolium (common chrysanthemum), Cynodon dactylon (Bermuda grass), Miscanthus florodulus (Sword grass) and Pteris vittata (Ladder brake fern) commonly found at all sites. AM fungal colonization was detected in most of the plants. Comparing the four common plant species, three components of mycorrhizal colonization (arbuscules, vesicles and coiled hyphae) were found in the roots of C. dactylon and P. vittata growing at Do Shun Long (DSL) mine site. Concentrations of As in fronds were 24-fold higher than in roots of P. vittata with the highest mycorrhizal colonization rate (73%) among all sampling sites. Extensive mycorrhizal colonization (85%) was also recorded in the roots of C. dactylon with As accumulation 57 times higher than in shoots. The four common plants found in metal contaminated sites had developed different strategies for survival in the contaminated sites with the aid of indigenous AM fungi.

  1. 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. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

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

    PubMed

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

    2013-07-01

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

  3. Effect of arbuscular mycorrhizal fungi on young vines in copper-contaminated soil

    PubMed Central

    Ambrosini, Vítor Gabriel; Voges, Joana Gerent; Canton, Ludiana; Couto, Rafael da Rosa; Ferreira, Paulo Ademar Avelar; Comin, Jucinei José; de Melo, George Wellington Bastos; Brunetto, Gustavo; Soares, Cláudio Roberto Fonsêca Sousa

    2015-01-01

    Abstract High copper (Cu) levels in uprooted old vineyard soils may cause toxicity in transplanted young vines, although such toxicity may be reduced by inoculating plants with arbuscular mycorrhizal fungi (AMF). The objective of this study was to evaluate the effects of AMF on the plant growth, chlorophyll contents, mycorrhizal colonization, and Cu and phosphorus (P) absorption in young vines cultivated in a vineyard soil contaminated by Cu. Commercial vineyard soil with high Cu levels was placed in plastic tubes and transplanted with young vines, which were inoculated with six AMF species (Dentiscutata heterogama, Gigaspora gigantea, Acaulospora morrowiae, A. colombiana, Rhizophagus clarus, R. irregularis) and a control treatment on randomized blocks with 12 replicates. After 130 days, the mycorrhizal colonization, root and shoot dry matter (DM), height increment, P and Cu absorption, and chlorophyll contents were evaluated. The height increment, shoot DM and chlorophyll contents were not promoted by AMF, although the root DM was increased by R. clarus and R. irregularis, which had the greatest mycorrhizal colonization and P uptake. AMF increased Cu absorption but decreased its transport to shoots. Thus, AMF species, particularly R. clarus and R. irregularis, contribute to the establishment of young vines exposed to high Cu levels. PMID:26691462

  4. Effect of arbuscular mycorrhizal fungi on young vines in copper-contaminated soil.

    PubMed

    Ambrosini, Vítor Gabriel; Voges, Joana Gerent; Canton, Ludiana; Couto, Rafael da Rosa; Ferreira, Paulo Ademar Avelar; Comin, Jucinei José; de Melo, George Wellington Bastos; Brunetto, Gustavo; Soares, Cláudio Roberto Fonsêca Sousa

    2015-01-01

    High copper (Cu) levels in uprooted old vineyard soils may cause toxicity in transplanted young vines, although such toxicity may be reduced by inoculating plants with arbuscular mycorrhizal fungi (AMF). The objective of this study was to evaluate the effects of AMF on the plant growth, chlorophyll contents, mycorrhizal colonization, and Cu and phosphorus (P) absorption in young vines cultivated in a vineyard soil contaminated by Cu. Commercial vineyard soil with high Cu levels was placed in plastic tubes and transplanted with young vines, which were inoculated with six AMF species (Dentiscutata heterogama, Gigaspora gigantea, Acaulospora morrowiae, A. colombiana, Rhizophagus clarus, R. irregularis) and a control treatment on randomized blocks with 12 replicates. After 130 days, the mycorrhizal colonization, root and shoot dry matter (DM), height increment, P and Cu absorption, and chlorophyll contents were evaluated. The height increment, shoot DM and chlorophyll contents were not promoted by AMF, although the root DM was increased by R. clarus and R. irregularis, which had the greatest mycorrhizal colonization and P uptake. AMF increased Cu absorption but decreased its transport to shoots. Thus, AMF species, particularly R. clarus and R. irregularis, contribute to the establishment of young vines exposed to high Cu levels.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. Arbuscular mycorrhizal colonization and nodulation improve flooding tolerance in Pterocarpus officinalis Jacq. seedlings.

    PubMed

    Fougnies, L; Renciot, S; Muller, F; Plenchette, C; Prin, Y; de Faria, S M; Bouvet, J M; Sylla, S Nd; Dreyfus, B; Bâ, A M

    2007-05-01

    Pterocarpus officinalis (Jacq.) seedlings inoculated with the arbuscular mycorrhizal fungus, Glomus intraradices, and the strain of Bradyrhizobium sp. (UAG 11A) were grown under stem-flooded or nonflooded conditions for 13 weeks after 4 weeks of nonflooded pretreatment under greenhouse conditions. Flooding of P. officinalis seedlings induced several morphological and physiological adaptive mechanisms, including formation of hypertrophied lenticels and aerenchyma tissue and production of adventitious roots on submerged portions of the stem. Flooding also resulted in an increase in collar diameter and leaf, stem, root, and total dry weights, regardless of inoculation. Under flooding, arbuscular mycorrhizas were well developed on root systems and adventitious roots compared with inoculated root systems under nonflooding condition. Arbuscular mycorrhizas made noteworthy contributions to the flood tolerance of P. officinalis seedlings by improving plant growth and P acquisition in leaves. We report in this study the novel occurrence of nodules connected vascularly to the stem and nodule and arbuscular mycorrhizas on adventitious roots of P. officinalis seedlings. Root nodules appeared more efficient fixing N(2) than stem nodules were. Beneficial effect of nodulation in terms of total dry weight and N acquisition in leaves was particularly noted in seedlings growing under flooding conditions. There was no additive effect of arbuscular mycorrhizas and nodulation on plant growth and nutrition in either flooding treatment. The results suggest that the development of adventitious roots, aerenchyma tissue, and hypertrophied lenticels may play a major role in flooded tolerance of P. officinalis symbiosis by increasing oxygen diffusion to the submerged part of the stem and root zone, and therefore contribute to plant growth and nutrition.

  10. 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.

  11. Diversity of arbuscular mycorrhizal fungi in Tectona grandis Linn.f. plantations and their effects on growth of micropropagated plantlets

    USDA-ARS?s Scientific Manuscript database

    Regeneration of stands of valuable tropical hardwood tree species for sustainable harvest requires production of seedlings with high probabilities of survival. One way to enhance the vigor of plants for outplanting is pre-colonization of roots by arbuscular mycorrhizal [AM] fungi. We pursued the s...

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

    USDA-ARS?s Scientific Manuscript database

    A greenhouse experiment was conducted to study the expression of two phosphate (P) transporter genes ZEAma:Pht1;3 (epidermal-expressed) and ZEAma:Pht1;6 (AM specific induced, and expressed around arbuscules) in maize root to colonization by different arbuscular mycorrhizal (AM) fungal inoculants. No...

  13. 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.

  14. 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.

  15. 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

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

    PubMed

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

    2016-07-20

    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.

  17. 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.

  18. Genetic diversity patterns of arbuscular mycorrhizal fungi associated with the mycoheterotroph Arachnitis uniflora Phil. (Corsiaceae).

    PubMed

    Renny, Mauricio; Acosta, M Cristina; Cofré, Noelia; Domínguez, Laura S; Bidartondo, Martin I; Sérsic, Alicia N

    2017-06-01

    Arachnitis uniflora is a mycoheterotrophic plant that exploits arbuscular mycorrhizal fungi of neighbouring plants. We tested A. uniflora 's specificity towards fungi across its large latitudinal range, as well as the role of historical events and current environmental, geographical and altitudinal variables on fungal genetic diversity. Arachnitis uniflora mycorrhizas were sampled at 25 sites. Fungal phylogenetic relationships were reconstructed, genetic diversity was calculated and the main divergent lineages were dated. Phylogeographical analysis was performed with the main fungal clade. Fungal diversity correlations with environmental factors were investigated. Glomeraceae fungi dominated, with a main clade that likely originated in the Upper Cretaceous and diversified in the Miocene. Two other arbuscular mycorrhizal fungal families not previously known to be targeted by A. uniflora were detected rarely and appear to be facultative associations. High genetic diversity, found in Bolivia and both northern and southern Patagonia, was correlated with temperature, rainfall and soil features. Fungal genetic diversity and its distribution can be explained by the ancient evolutionary history of the target fungi and by micro-scale environmental conditions with a geographical mosaic pattern.

  19. 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

  20. 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

  1. Auxin perception is required for arbuscule development in arbuscular mycorrhizal symbiosis.

    PubMed

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

    2014-09-01

    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. © 2014 American Society of Plant Biologists. All Rights Reserved.

  2. Prospects for arbuscular mycorrhizal fungi (AMF) to assist in phytoremediation of soil hydrocarbon contaminants.

    PubMed

    Rajtor, Monika; Piotrowska-Seget, Zofia

    2016-11-01

    Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with the roots of 80-90% of vascular plant species and may constitute up to 50% of the total soil microbial biomass. AMF have been considered to be a tool to enhance phytoremediation, as their mycelium create a widespread underground network that acts as a bridge between plant roots, soil and rhizosphere microorganisms. Abundant extramatrical hyphae extend the rhizosphere thus creating the hyphosphere, which significantly increases the area of a plant's access to nutrients and contaminants. The paper presents and evaluates the role and significance of AMF in phytoremediation of hydrocarbon contaminated sites. We focused on (1) an impact of hydrocarbons on arbuscular mycorrhizal symbiosis, (2) a potential of AMF to enhance phytoremediation, (3) determinants that influence effectiveness of hydrocarbon removal from contaminated soils. This knowledge may be useful for selection of proper plant and fungal symbionts and crucial to optimize environmental conditions for effective AMF-mediated phytoremediation. It has been concluded that three-component phytoremediation systems based on synergistic interactions between plant roots, AMF and hydrocarbon-degrading microorganisms demonstrated high effectiveness in dissipation of organic pollutants in soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. [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.

  4. 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.

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

    PubMed Central

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

    2013-01-01

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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Arbuscular-Mycorrhizal Networks Inhibit Eucalyptus tetrodonta Seedlings in Rain Forest Soil Microcosms

    PubMed Central

    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. PMID:23460899

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  19. [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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. Arbuscular mycorrhizal fungi reduce growth and infect roots of the non-host plant Arabidopsis thaliana.

    PubMed

    Veiga, Rita S L; Faccio, Antonella; Genre, Andrea; Pieterse, Corné M J; Bonfante, Paola; van der Heijden, Marcel G A

    2013-11-01

    The arbuscular mycorrhizal (AM) symbiosis is widespread throughout the plant kingdom and important for plant nutrition and ecosystem functioning. Nonetheless, most terrestrial ecosystems also contain a considerable number of non-mycorrhizal plants. The interaction of such non-host plants with AM fungi (AMF) is still poorly understood. Here, in three complementary experiments, we investigated whether the non-mycorrhizal plant Arabidopsis thaliana, the model organism for plant molecular biology and genetics, interacts with AMF. We grew A. thaliana alone or together with a mycorrhizal host species (either Trifolium pratense or Lolium multiflorum) in the presence or absence of the AMF Rhizophagus irregularis. Plants were grown in a dual-compartment system with a hyphal mesh separating roots of A. thaliana from roots of the host species, avoiding direct root competition. The host plants in the system ensured the presence of an active AM fungal network. AM fungal networks caused growth depressions in A. thaliana of more than 50% which were not observed in the absence of host plants. Microscopy analyses revealed that R. irregularis supported by a host plant was capable of infecting A. thaliana root tissues (up to 43% of root length colonized), but no arbuscules were observed. The results reveal high susceptibility of A. thaliana to R. irregularis, suggesting that A. thaliana is a suitable model plant to study non-host/AMF interactions and the biological basis of AM incompatibility. © 2013 John Wiley & Sons Ltd.

  7. Two putative-aquaporin genes are differentially expressed during arbuscular mycorrhizal symbiosis in Lotus japonicus

    PubMed Central

    2012-01-01

    Background Arbuscular mycorrhizas (AM) are widespread symbioses that provide great advantages to the plant, improving its nutritional status and allowing the fungus to complete its life cycle. Nevertheless, molecular mechanisms that lead to the development of AM symbiosis are not yet fully deciphered. Here, we have focused on two putative aquaporin genes, LjNIP1 and LjXIP1, which resulted to be upregulated in a transcriptomic analysis performed on mycorrhizal roots of Lotus japonicus. Results A phylogenetic analysis has shown that the two putative aquaporins belong to different functional families: NIPs and XIPs. Transcriptomic experiments have shown the independence of their expression from their nutritional status but also a close correlation with mycorrhizal and rhizobial interaction. Further transcript quantification has revealed a good correlation between the expression of one of them, LjNIP1, and LjPT4, the phosphate transporter which is considered a marker gene for mycorrhizal functionality. By using laser microdissection, we have demonstrated that one of the two genes, LjNIP1, is expressed exclusively in arbuscule-containing cells. LjNIP1, in agreement with its putative role as an aquaporin, is capable of transferring water when expressed in yeast protoplasts. Confocal analysis have demonstrated that eGFP-LjNIP1, under its endogenous promoter, accumulates in the inner membrane system of arbusculated cells. Conclusions Overall, the results have shown different functionality and expression specificity of two mycorrhiza-inducible aquaporins in L. japonicus. One of them, LjNIP1 can be considered a novel molecular marker of mycorrhizal status at different developmental stages of the arbuscule. At the same time, LjXIP1 results to be the first XIP family aquaporin to be transcriptionally regulated during symbiosis. PMID:23046713

  8. 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.

  9. 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.

  10. 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.

  11. Arbuscular mycorrhizal symbiosis mitigates the negative effects of salinity on durum wheat.

    PubMed

    Fileccia, Veronica; Ruisi, Paolo; Ingraffia, Rosolino; Giambalvo, Dario; Frenda, Alfonso Salvatore; Martinelli, Federico

    2017-01-01

    Arbuscular mycorrhizal (AM) symbiosis is generally considered to be effective in ameliorating the plant tolerance to salt stress. Unfortunately, the comprehension of the mechanisms implicated in salinity stress alleviation by AM symbiosis is far from being complete. Thus, an experiment was performed by growing durum wheat (Triticum durum Desf.) plants under salt-stress conditions to evaluate the influence of AM symbiosis on both the plant growth and the regulation of a number of genes related to salt stress and nutrient uptake. Durum wheat plants were grown outdoors in pots in absence or in presence of salt stress and with or without AM fungi inoculation. The inoculum consisted of a mixture of spores of Rhizophagus irregularis (formerly Glomus intraradices) and Funneliformis mosseae (formerly G. mosseae). Results indicate that AM symbiosis can alleviate the detrimental effects of salt stress on the growth of durum wheat plants. In fact, under salt stress conditions mycorrhizal plants produced more aboveground and root biomass, had higher N uptake and aboveground N concentration, and showed greater stability of plasma membranes compared to non-mycorrhizal plants. Inoculation with AM fungi had no effect on the expression of the N transporter genes AMT1.1, AMT1.2, and NAR2.2, either under no-stress or salt stress conditions, probably due to the fact that plants were grown under optimal N conditions; on the contrary, NRT1.1 was always upregulated by AM symbiosis. Moreover, the level of expression of the drought stress-related genes AQP1, AQP4, PIP1, DREB5, and DHN15.3 observed in the mycorrhizal stressed plants was markedly lower than that observed in the non-mycorrhizal stressed plants and very close to that observed in the non-stressed plants. Our hypothesis is that, in the present study, AM symbiosis did not increase the plant tolerance to salt stress but instead generated a condition in which plants were subjected to a level of salt stress lower than that of non-mycorrhizal

  12. 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.

  13. Increased Sporulation of Vesicular-Arbuscular Mycorrhizal Fungi by Manipulation of Nutrient Regimens †

    PubMed Central

    Douds, David D.; Schenck, N. C.

    1990-01-01

    Adjustment of pot culture nutrient solutions increased root colonization and sporulation of vesicular-arbuscular mycorrhizal (VAM) fungi. Paspalum notatum Flugge and VAM fungi were grown in a sandy soil low in N and available P. Hoagland nutrient solution without P enhanced sporulation in soil and root colonization of Acaulospora longula, Scutellospora heterogama, Gigaspora margarita, and a wide range of other VAM fungi over levels produced by a tap water control or nutrient solutions containing P. However, Glomus intraradices produced significantly more spores in plant roots in the tap water control treatment. The effect of the nutrient solutions was not due solely to N nutrition, because the addition of NH4NO3 decreased both colonization and sporulation by G. margarita relative to levels produced by Hoagland solution without P. PMID:16348115

  14. 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

  15. Organic nitrogen uptake by arbuscular mycorrhizal fungi in a boreal forest

    PubMed Central

    Whiteside, Matthew D.; Digman, Michelle A.; Gratton, Enrico; Treseder, Kathleen K.

    2013-01-01

    The breakdown of organic nitrogen in soil is a potential rate-limiting step in nitrogen cycling. Arbuscular mycorrhizal (AM) fungi are root symbionts that might improve the ability of plants to compete for organic nitrogen products against other decomposer microbes. However, AM uptake of organic nitrogen, especially in natural systems, has traditionally been difficult to test. We developed a novel quantitative nanotechnological technique to determine in situ that organic nitrogen uptake by AM fungi can occur to a greater extent than has previously been assumed. Specifically, we found that AM fungi acquired recalcitrant and labile forms of organic nitrogen. Moreover, N enrichment of soil reduced plot-scale uptake of these compounds. Since most plants host AM fungi, AM use of organic nitrogen could widely influence plant productivity, especially where N availability is relatively low. PMID:24371363

  16. 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.

  17. 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

  18. 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.

  19. [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.

  20. FUNGAL SYMBIONTS. Global assessment of arbuscular mycorrhizal fungus diversity reveals very low endemism.

    PubMed

    Davison, J; Moora, M; Öpik, M; Adholeya, A; Ainsaar, L; Bâ, A; Burla, S; Diedhiou, A G; Hiiesalu, I; Jairus, T; Johnson, N C; Kane, A; Koorem, K; Kochar, M; Ndiaye, C; Pärtel, M; Reier, Ü; Saks, Ü; Singh, R; Vasar, M; Zobel, M

    2015-08-28

    The global biogeography of microorganisms remains largely unknown, in contrast to the well-studied diversity patterns of macroorganisms. We used arbuscular mycorrhizal (AM) fungus DNA from 1014 plant-root samples collected worldwide to determine the global distribution of these plant symbionts. We found that AM fungal communities reflected local environmental conditions and the spatial distance between sites. However, despite AM fungi apparently possessing limited dispersal ability, we found 93% of taxa on multiple continents and 34% on all six continents surveyed. This contrasts with the high spatial turnover of other fungal taxa and with the endemism displayed by plants at the global scale. We suggest that the biogeography of AM fungi is driven by unexpectedly efficient dispersal, probably via both abiotic and biotic vectors, including humans.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Bacteria associated with spores of the arbuscular mycorrhizal fungi Glomus geosporum and Glomus constrictum.

    PubMed

    Roesti, David; Ineichen, Kurt; Braissant, Olivier; Redecker, Dirk; Wiemken, Andres; Aragno, Michel

    2005-11-01

    Spores of the arbuscular mycorrhizal fungi (AMF) Glomus geosporum and Glomus constrictum were harvested from single-spore-derived pot cultures with either Plantago lanceolata or Hieracium pilosella as host plants. PCR-denaturing gradient gel electrophoresis analysis revealed that the bacterial communities associated with the spores depended more on AMF than host plant identity. The composition of the bacterial populations linked to the spores could be predominantly influenced by a specific spore wall composition or AMF exudate rather than by specific root exudates. The majority of the bacterial sequences that were common to both G. geosporum and G. constrictum spores were affiliated with taxonomic groups known to degrade biopolymers (Cellvibrio, Chondromyces, Flexibacter, Lysobacter, and Pseudomonas). Scanning electron microscopy of G. geosporum spores revealed that these bacteria are possibly feeding on the outer hyaline spore layer. The process of maturation and eventual germination of AMF spores might then benefit from the activity of the surface microorganisms degrading the outer hyaline wall layer.

  6. Different levels of hyphal self-incompatibility modulate interconnectedness of mycorrhizal networks in three arbuscular mycorrhizal fungi within the Glomeraceae.

    PubMed

    Pepe, Alessandra; Giovannetti, Manuela; Sbrana, Cristiana

    2016-05-01

    Arbuscular mycorrhizal fungi (AMF) live in symbiosis with most plant species and produce underground extraradical hyphal networks functional in the uptake and translocation of mineral nutrients from the soil to host plants. This work investigated whether fungal genotype can affect patterns of interconnections and structural traits of extraradical mycelium (ERM), by comparing three Glomeraceae species growing in symbiosis with five plant hosts. An isolate of Funneliformis coronatus consistently showed low ability to form interconnected ERM and self-incompatibility that represented up to 21% of hyphal contacts. The frequency of post-fusion self-incompatible interactions, never detected before in AMF extraradical networks, was 8.9%. In F. coronatus ERM, the percentage of hyphal contacts leading to perfect hyphal fusions was 1.2-7.7, while it ranged from 25.8-48 to 35.6-53.6 in Rhizophagus intraradices and Funneliformis mosseae, respectively. Low interconnectedness of F. coronatus ERM resulted also from a very high number of non-interacting contacts (83.2%). Such findings show that AMF genotypes in Glomeraceae can differ significantly in anastomosis behaviour and that ERM interconnectedness is modulated by the fungal symbiont, as F. coronatus consistently formed poorly interconnected networks when growing in symbiosis with five different host plants and in the asymbiotic stage. Structural traits, such as extent, density and hyphal self-compatibility/incompatibility, may represent key factors for the differential performance of AMF, by affecting fungal absorbing surface and foraging ability and thus nutrient flow from soil to host roots.

  7. 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.

  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. 'Candidatus glomeribacter gigasporarum' gen. nov., sp. nov., an endosymbiont of arbuscular mycorrhizal fungi.

    PubMed

    Bianciotto, Valeria; Lumini, Erica; Bonfante, Paola; Vandamme, Peter

    2003-01-01

    Arbuscular mycorrhizal fungi are obligate endosymbionts that colonize the roots of almost 80 % of land plants. The present paper describes morphological and molecular data on a bacterial endosymbiont living in the cytoplasm of dormant or germinating spores and symbiotic mycelia of the fungal species Gigaspora margarita, Scutellospora persica and Scutellospora castanea. PCR amplification of almost the entire 16S rRNA gene of the Gigaspora margarita BEG 34 endosymbiont, using universal bacterial primers, and subsequent sequence analysis demonstrated that this organism occupies a very distinct phylogenetic position within the beta-Proteobacteria, with the genera Burkholderia, Pandoraea and Ralstonia as its closest neighbours. Primers specific to the 16S rDNA of the endosymbiotic bacteria of BEG 34 allowed amplification of spore DNA from endosymbionts of Gigaspora margarita, Gigaspora decipiens, S. persica and S. castanea, but not from the Gigaspora gigantea endosymbiont (which was morphologically different) or from the cytoplasm of Gigaspora rosea (which did not contain endosymbiotic bacteria). These specific primers were successfully used as a probe for the in-situ hybridization of endobacteria in Gigaspora margarita spores. The overall rod-shaped morphology of the Gigaspora margarita, Gigaspora decipiens, S. persica and S. castanea endosymbionts was similar, and amplification and sequence analysis of the almost-complete 16S rRNA genes of several Gigaspora margarita, S. persica and S. castanea endosymbionts revealed over 98% sequence similarity. These morphological and genomic characteristics were used to assign the endosymbionts of these three species (five isolates) of arbuscular mycorrhizal fungi as 'Candidatus Glomeribacter gigasporarum' gen. nov., sp. nov.

  10. 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

  11. 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.

  12. Diversity and Spatial Structure of Belowground Plant–Fungal Symbiosis in a Mixed Subtropical Forest of Ectomycorrhizal and Arbuscular Mycorrhizal Plants

    PubMed Central

    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

  13. 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

  14. 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.

  15. 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

  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. [Response of arbuscular mycorrhizal fungal lipid metabolism to symbiotic signals in mycorrhiza].

    PubMed

    Tian, Lei; Li, Yuanjing; Tian, Chunjie

    2016-01-04

    Arbuscular mycorrhizal (AM) fungi play an important role in energy flow and nutrient cycling, besides their wide distribution in the cosystem. With a long co-evolution, AM fungi and host plant have formed a symbiotic relationship, and fungal lipid metabolism may be the key point to find the symbiotic mechanism in arbusculart mycorrhiza. Here, we reviewed the most recent progress on the interaction between AM fungal lipid metabolism and symbiotic signaling networks, especially the response of AM fungal lipid metabolism to symbiotic signals. Furthermore, we discussed the response of AM fungal lipid storage and release to symbiotic or non-symbiotic status, and the correlation between fungal lipid metabolism and nutrient transfer in mycorrhiza. In addition, we explored the feedback of the lipolysis process to molecular signals during the establishment of symbiosis, and the corresponding material conversion and energy metabolism besides the crosstalk of fungal lipid metabolism and signaling networks. This review will help understand symbiotic mechanism of arbuscular mycorrhiza fungi and further application in ecosystem.

  18. 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.

  19. Expression of phenazine biosynthetic genes during the arbuscular mycorrhizal symbiosis of Glomus intraradices

    PubMed Central

    León-Martínez, Dionicia Gloria; Vielle-Calzada, Jean-Philippe; Olalde-Portugal, Víctor

    2012-01-01

    To explore the molecular mechanisms that prevail during the establishment of the arbuscular mycorrhiza symbiosis involving the genus Glomus, we transcriptionally analysed spores of Glomus intraradices BE3 during early hyphal growth. Among 458 transcripts initially identified as being expressed at presymbiotic stages, 20% of sequences had homology to previously characterized eukaryotic genes, 30% were homologous to fungal coding sequences, and 9% showed homology to previously characterized bacterial genes. Among them, GintPbr1a encodes a homolog to Phenazine Biosynthesis Regulator (Pbr) of Burkholderia cenocepacia, an pleiotropic regulatory protein that activates phenazine production through transcriptional activation of the protein D isochorismatase biosynthetic enzyme phzD (Ramos et al., 2010). Whereas GintPbr1a is expressed during the presymbiotic phase, the G. intraradices BE3 homolog of phzD (BGintphzD) is transcriptionally active at the time of the establishment of the arbuscular mycorrhizal symbiosis. DNA from isolated bacterial cultures found in spores of G. intraradices BE3 confirmed that both BGintPbr1a and BGintphzD are present in the genome of its potential endosymbionts. Taken together, our results indicate that spores of G. intraradices BE3 express bacterial phenazine biosynthetic genes at the onset of the fungal-plant symbiotic interaction. PMID:24031884

  20. Arbuscular mycorrhizal fungi increased early growth of two nontimber forest product species Dyera polyphylla and Aquilaria filaria under greenhouse conditions.

    PubMed

    Turjaman, Maman; Tamai, Yutaka; Santoso, Erdy; Osaki, Mitsuru; Tawaraya, Keitaro

    2006-10-01

    Nontimber forest products (NTFPs) represent an important source of income to millions of people in tropical forest regions, but some NTFP species have decreased in number and become endangered due to overexploitation. There is increasing concern that the planting stocks of Dyera polyphylla and Aquilaria filaria are not sufficient to sustain the yield of NTFPs and promote forest conservation. The objective of this study was to determine the effect of two arbuscular mycorrhizal (AM) fungi, Glomus clarum and Gigaspora decipiens, on the early growth of two NTFP species, D. polyphylla and A. filaria, under greenhouse conditions. The seedlings of both species were inoculated with G. clarum or G. decipiens, or uninoculated (control) under greenhouse conditions. Percentage of AM colonization, plant growth, survival rate, and nitrogen (N) and phosphorus (P) concentrations were measured after 180 days of growth. The percentage of AM colonization of D. polyphylla and A. filaria ranged from 87 to 93% and from 22 to 39%, respectively. Colonization by G. clarum and G. decipiens increased plant height, diameter, and shoot and root dry weights. Shoot N and P concentrations of the seedlings were increased by AM colonization by as much as 70-153% and 135-360%, respectively. Survival rates were higher in the AM-colonized seedlings at 180 days after transplantation than in the control seedlings. The results suggest that AM fungi can accelerate the establishment of the planting stocks of D. polyphylla and A. filaria, thereby promoting their conservation ecologically and sustaining the production of these NTFPs economically.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  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. The regulation of arbuscular mycorrhizal symbiosis by phosphate in pea involves early and systemic signalling events.

    PubMed

    Balzergue, Coline; Puech-Pagès, Virginie; Bécard, Guillaume; Rochange, Soizic F

    2011-01-01

    Most plants form root symbioses with arbuscular mycorrhizal (AM) fungi, which provide them with phosphate and other nutrients. High soil phosphate levels are known to affect AM symbiosis negatively, but the underlying mechanisms are not understood. This report describes experimental conditions which triggered a novel mycorrhizal phenotype under high phosphate supply: the interaction between pea and two different AM fungi was almost completely abolished at a very early stage, prior to the formation of hyphopodia. As demonstrated by split-root experiments, down-regulation of AM symbiosis occurred at least partly in response to plant-derived signals. Early signalling events were examined with a focus on strigolactones, compounds which stimulate pre-symbiotic fungal growth and metabolism. Strigolactones were also recently identified as novel plant hormones contributing to the control of shoot branching. Root exudates of plants grown under high phosphate lost their ability to stimulate AM fungi and lacked strigolactones. In addition, a systemic down-regulation of strigolactone release by high phosphate supply was demonstrated using split-root systems. Nevertheless, supplementation with exogenous strigolactones failed to restore root colonization under high phosphate. This observation does not exclude a contribution of strigolactones to the regulation of AM symbiosis by phosphate, but indicates that they are not the only factor involved. Together, the results suggest the existence of additional early signals that may control the differentiation of hyphopodia.

  8. Improvement of Cupressus atlantica Gaussen growth by inoculation with native arbuscular mycorrhizal fungi.

    PubMed

    Ouahmane, L; Hafidi, M; Thioulouse, J; Ducousso, M; Kisa, M; Prin, Y; Galiana, A; Boumezzough, A; Duponnois, R

    2007-09-01

    The study aimed to determine whether inoculation with native arbuscular mycorrhizal (AM) fungi could improve survival and growth of seedlings in degraded soils of Morocco. Soil samples were collected from the rhizosphere of Cupressus atlantica trees in the N'Fis valley (Haut Atlas, Morocco). AM spores were extracted from the soil, identified and this mixture of native AM fungi was propagated on maize for 12 weeks on a sterilized soil to enrich the fungal inoculum. Then C. atlantica seedlings were inoculated with and without (control) mycorrhizal maize roots, cultured in glasshouse conditions and further, transplanted into the field. The experiment was a randomized block design with one factor and three replication blocks. The results showed that a high AM fungal diversity was associated with C. atlantica; native AM fungi inoculation was very effective on the growth of C. atlantica seedlings in glasshouse conditions and this plant growth stimulation was maintained for 1 year after outplanting. Inoculation of C. atlantica with AM fungi increased growth and survival in greenhouse and field. The data indicate that use of native species of AM fungi may accelerate reforestation of degraded soils. Further studies have to be performed to determine the persistence of these mycorrhizae for a longer period of plantation and to measure the effects of this microbial inoculation on soil biofunctioning.

  9. 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.

  10. 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

  11. 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.

  12. [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.

  13. Plant growth depressions in arbuscular mycorrhizal symbioses: not just caused by carbon drain?

    PubMed

    Li, Huiying; Smith, F Andrew; Dickson, Sandy; Holloway, Robert E; Smith, Sally E

    2008-01-01

    * This study investigated effects of plant density and arbuscular mycorrhizal (AM) colonization on growth and phosphorus (P) nutrition of a cultivar of wheat (Triticum aestivum) that often shows early AM-induced growth depressions. * Two experiments were conducted. Expt 1 had three plant densities and one soil P concentration. Expt 2 had two plant densities and two P concentrations. Plants were grown in calcareous P-fixing soil, inoculated with Glomus intraradices or Gigaspora margarita, or noninoculated (nonmycorrhizal (NM)). Glomus intraradices colonized well and caused a growth depression only in Expt 1. Gigaspora margarita caused large growth depressions in both experiments even though it colonized poorly. * The results showed that growth depressions were mitigated by changes in relative competition for soil P by NM and AM plants, and probably by decreasing carbon costs of the fungi. * The different effects of the two fungi appear to be attributable to differences in the balance between P uptake by the fungal pathway and direct uptake via the roots. These differences may be important in other AM symbioses that result in growth depressions. The results show that mycorrhizal growth responses of plants grown singly may not apply at the population or community level.

  14. The regulation of arbuscular mycorrhizal symbiosis by phosphate in pea involves early and systemic signalling events

    PubMed Central

    Balzergue, Coline; Puech-Pagès, Virginie; Bécard, Guillaume; Rochange, Soizic F.

    2011-01-01

    Most plants form root symbioses with arbuscular mycorrhizal (AM) fungi, which provide them with phosphate and other nutrients. High soil phosphate levels are known to affect AM symbiosis negatively, but the underlying mechanisms are not understood. This report describes experimental conditions which triggered a novel mycorrhizal phenotype under high phosphate supply: the interaction between pea and two different AM fungi was almost completely abolished at a very early stage, prior to the formation of hyphopodia. As demonstrated by split-root experiments, down-regulation of AM symbiosis occurred at least partly in response to plant-derived signals. Early signalling events were examined with a focus on strigolactones, compounds which stimulate pre-symbiotic fungal growth and metabolism. Strigolactones were also recently identified as novel plant hormones contributing to the control of shoot branching. Root exudates of plants grown under high phosphate lost their ability to stimulate AM fungi and lacked strigolactones. In addition, a systemic down-regulation of strigolactone release by high phosphate supply was demonstrated using split-root systems. Nevertheless, supplementation with exogenous strigolactones failed to restore root colonization under high phosphate. This observation does not exclude a contribution of strigolactones to the regulation of AM symbiosis by phosphate, but indicates that they are not the only factor involved. Together, the results suggest the existence of additional early signals that may control the differentiation of hyphopodia. PMID:21045005

  15. 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. Copyright 2010 Elsevier Ltd. All rights reserved.

  16. 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

  17. 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

  18. 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.

  19. Transcriptome diversity among rice root types during asymbiosis and interaction with arbuscular mycorrhizal fungi.

    PubMed

    Gutjahr, Caroline; Sawers, Ruairidh J H; Marti, Guillaume; Andrés-Hernández, Liliana; Yang, Shu-Yi; Casieri, Leonardo; Angliker, Herbert; Oakeley, Edward J; Wolfender, Jean-Luc; Abreu-Goodger, Cei; Paszkowski, Uta

    2015-05-26

    Root systems consist of different root types (RTs) with distinct developmental and functional characteristics. RTs may be individually reprogrammed in response to their microenvironment to maximize adaptive plasticity. Molecular understanding of such specific remodeling--although crucial for crop improvement--is limited. Here, RT-specific transcriptomes of adult rice crown, large and fine lateral roots were assessed, revealing molecular evidence for functional diversity among individual RTs. Of the three rice RTs, crown roots displayed a significant enrichment of transcripts associated with phytohormones and secondary cell wall (SCW) metabolism, whereas lateral RTs showed a greater accumulation of transcripts related to mineral transport. In nature, arbuscular mycorrhizal (AM) symbiosis represents the default state of most root systems and is known to modify root system architecture. Rice RTs become heterogeneously colonized by AM fungi, with large laterals preferentially entering into the association. However, RT-specific transcriptional responses to AM symbiosis were quantitatively most pronounced for crown roots despite their modest physical engagement in the interaction. Furthermore, colonized crown roots adopted an expression profile more related to mycorrhizal large lateral than to noncolonized crown roots, suggesting a fundamental reprogramming of crown root character. Among these changes, a significant reduction in SCW transcripts was observed that was correlated with an alteration of SCW composition as determined by mass spectrometry. The combined change in SCW, hormone- and transport-related transcript profiles across the RTs indicates a previously overlooked switch of functional relationships among RTs during AM symbiosis, with a potential impact on root system architecture and functioning.

  20. 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

  1. 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.

  2. 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.

  3. Stressed out symbiotes: hypotheses for the influence of abiotic stress on arbuscular mycorrhizal fungi.

    PubMed

    Millar, Niall S; Bennett, Alison E

    2016-11-01

    Abiotic stress is a widespread threat to both plant and soil communities. Arbuscular mycorrhizal (AM) fungi can alleviate effects of abiotic stress by improving host plant stress tolerance, but the direct effects of abiotic stress on AM fungi are less well understood. We propose two hypotheses predicting how AM fungi will respond to abiotic stress. The stress exclusion hypothesis predicts that AM fungal abundance and diversity will decrease with persistent abiotic stress. The mycorrhizal stress adaptation hypothesis predicts that AM fungi will evolve in response to abiotic stress to maintain their fitness. We conclude that abiotic stress can have effects on AM fungi independent of the effects on the host plant. AM fungal communities will change in composition in response to abiotic stress, which may mean the loss of important individual species. This could alter feedbacks to the plant community and beyond. AM fungi will adapt to abiotic stress independent of their host plant. The adaptation of AM fungi to abiotic stress should allow the maintenance of the plant-AM fungal mutualism in the face of changing climates.

  4. 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.

  5. Arbuscular mycorrhizal fungi in saline soils: vertical distribution at different soil depth.

    PubMed

    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.

  6. 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. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  7. 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.

  8. 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

  9. 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

  10. Reduced aboveground tree growth associated with higher arbuscular mycorrhizal fungal diversity in tropical forest restoration.

    PubMed

    Holste, Ellen K; Holl, Karen D; Zahawi, Rakan A; Kobe, Richard K

    2016-10-01

    Establishing diverse mycorrhizal fungal communities is considered important for forest recovery, yet mycorrhizae may have complex effects on tree growth depending on the composition of fungal species present. In an effort to understand the role of mycorrhizal fungi community in forest restoration in southern Costa Rica, we sampled the arbuscular mycorrhizal fungal (AMF) community across eight sites that were planted with the same species (Inga edulis, Erythrina poeppigiana, Terminalia amazonia, and Vochysia guatemalensis) but varied twofold to fourfold in overall tree growth rates. The AMF community was measured in multiple ways: as percent colonization of host tree roots, by DNA isolation of the fungal species associated with the roots, and through spore density, volume, and identity in both the wet and dry seasons. Consistent with prior tropical restoration research, the majority of fungal species belonged to the genus Glomus and genus Acaulospora, accounting for more than half of the species and relative abundance found on trees roots and over 95% of spore density across all sites. Greater AMF diversity correlated with lower soil organic matter, carbon, and nitrogen concentrations and longer durations of prior pasture use across sites. Contrary to previous literature findings, AMF species diversity and spore densities were inversely related to tree growth, which may have arisen from trees facultatively increasing their associations with AMF in lower soil fertility sites. Changes to AMF community composition also may have led to variation in disturbance susceptibility, host tree nutrient acquisition, and tree growth. These results highlight the potential importance of fungal-tree-soil interactions in forest recovery and suggest that fungal community dynamics could have important implications for tree growth in disturbed soils.

  11. Arbuscular mycorrhizal fungi alter the competitive hierarchy among old-field plant species.

    PubMed

    Stanescu, Sabina; Maherali, Hafiz

    2017-02-01

    Inoculation with arbuscular mycorrhizal (AM) fungi is known to increase the species diversity of plant communities. One mechanism that can increase the likelihood of species co-existence, and thus species diversity, is a trade-off between competitive ability and the magnitude of plant growth response to AM fungal inoculation. By suppressing the growth of strong competitors while simultaneously enhancing the growth of weak competitors, this trade-off would cause the competitive hierarchy to be less pronounced in soil inoculated with AM fungi relative to non-inoculated conditions. To test whether such a trade-off exists, we quantified competitive abilities and mycorrhizal growth response (MGR) among 21 species that co-occur in old fields in southern Ontario. Competitive ability was determined by calculating competitive effect (CE), or the degree to which each species suppressed the biomass of a common phytometer species, Plantago lanceolata. Higher CE values represent stronger competitive ability. Old-field species varied in their ability to suppress the biomass of the phytometer and MGR was generally positive. There was a statistically significant negative correlation between CE in non-inoculated soil and MGR (r = -0.49, P = 0.02). In addition, variance in CE was 73% lower in soil inoculated with AM fungi compared to non-inoculated soil (P = 0.0023). These findings support the hypothesis that AM fungi weaken strong competitors while enhancing the performance of weak competitors. Because this trade-off compressed the competitive hierarchy among old-field species in soil inoculated with AM fungi, it may be a mechanism by which mycorrhizal fungi enhance species evenness and diversity.

  12. 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.

  13. 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

  14. Arbuscular mycorrhizal fungi enhance photosynthesis, water use efficiency, and growth of frankincense seedlings under pulsed water availability conditions.

    PubMed

    Birhane, Emiru; Sterck, Frank J; Fetene, Masresha; Bongers, Frans; Kuyper, Thomas W

    2012-08-01

    Under drought conditions, arbuscular mycorrhizal (AM) fungi alter water relationships of plants and improve their resistance to drought. In a factorial greenhouse experiment, we tested the effects of the AM symbiosis and precipitation regime on the performance (growth, gas exchange, nutrient status and mycorrhizal responsiveness) of Boswellia papyrifera seedlings. A continuous precipitation regime was imitated by continuous watering of plants to field capacity every other day during 4 months, and irregular precipitation by pulsed watering of plants where watering was switched every 15 days during these 4 months, with 15 days of watering followed by 15 days without watering. There were significantly higher levels of AM colonization under irregular precipitation regime than under continuous precipitation. Mycorrhizal seedlings had higher biomass than control seedlings. Stomatal conductance and phosphorus mass fraction in shoot and root were also significantly higher for mycorrhizal seedlings. Mycorrhizal seedlings under irregular watering had the highest biomass. Both a larger leaf area and higher assimilation rates contributed to higher biomass. Under irregular watering, the water use efficiency increased in non-mycorrhizal seedlings through a reduction in transpiration, while in mycorrhizal seedlings irregular watering increased transpiration. Because assimilation rates increased even more, mycorrhizal seedlings achieved an even higher water use efficiency. Boswellia seedlings allocated almost all carbon to the storage root. Boswellia seedlings had higher mass fractions of N, P, and K in roots than in shoots. Irregular precipitation conditions apparently benefit Boswellia seedlings when they are mycorrhizal. Electronic supplementary material The online version of this article (doi:10.1007/s00442-012-2258-3) contains supplementary material, which is available to authorized users.

  15. 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

  16. 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

  17. Revealing Natural Relationships among Arbuscular Mycorrhizal Fungi: Culture Line BEG47 Represents Diversispora epigaea, Not Glomus versiforme

    PubMed Central

    Schüßler, Arthur; Krüger, Manuela; Walker, Christopher

    2011-01-01

    Background Understanding the mechanisms underlying biological phenomena, such as evolutionarily conservative trait inheritance, is predicated on knowledge of the natural relationships among organisms. However, despite their enormous ecological significance, many of the ubiquitous soil inhabiting and plant symbiotic arbuscular mycorrhizal fungi (AMF, phylum Glomeromycota) are incorrectly classified. Methodology/Principal Findings Here, we focused on a frequently used model AMF registered as culture BEG47. This fungus is a descendent of the ex-type culture-lineage of Glomus epigaeum, which in 1983 was synonymised with Glomus versiforme. It has since then been used as ‘G. versiforme BEG47’. We show by morphological comparisons, based on type material, collected 1860–61, of G. versiforme and on type material and living ex-type cultures of G. epigaeum, that these two AMF species cannot be conspecific, and by molecular phylogenetics that BEG47 is a member of the genus Diversispora. Conclusions This study highlights that experimental works published during the last >25 years on an AMF named ‘G. versiforme’ or ‘BEG47’ refer to D. epigaea, a species that is actually evolutionarily separated by hundreds of millions of years from all members of the genera in the Glomerales and thus from most other commonly used AMF ‘laboratory strains’. Detailed redescriptions substantiate the renaming of G. epigaeum (BEG47) as D. epigaea, positioning it systematically in the order Diversisporales, thus enabling an evolutionary understanding of genetical, physiological, and ecological traits, relative to those of other AMF. Diversispora epigaea is widely cultured as a laboratory strain of AMF, whereas G. versiforme appears not to have been cultured nor found in the field since its original description. PMID:21853113

  18. 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.

  19. 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.

  20. 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.

  1. Insights on the Impact of Arbuscular Mycorrhizal Symbiosis on Tomato Tolerance to Water Stress.

    PubMed

    Chitarra, Walter; Pagliarani, Chiara; Maserti, Biancaelena; Lumini, Erica; Siciliano, Ilenia; Cascone, Pasquale; Schubert, Andrea; Gambino, Giorgio; Balestrini, Raffaella; Guerrieri, Emilio

    2016-06-01

    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. © 2016 American Society of Plant Biologists. All Rights Reserved.

  2. The intercropping partner affects arbuscular mycorrhizal fungi and Fusarium oxysporum f. sp. lycopersici interactions in tomato.

    PubMed

    Hage-Ahmed, Karin; Krammer, Johannes; Steinkellner, Siegrid

    2013-10-01

    Arbuscular mycorrhizal fungi (AMF) and their bioprotective aspects are of great interest in the context of sustainable agriculture. Combining the benefits of AMF with the utilisation of plant species diversity shows great promise for the management of plant diseases in environmentally compatible agriculture. In the present study, AMF were tested against Fusarium oxysporum f. sp. lycopersici with tomato intercropped with either leek, cucumber, basil, fennel or tomato itself. Arbuscular mycorrhizal (AM) root colonisation of tomato was clearly affected by its intercropping partners. Tomato intercropped with leek showed even a 20 % higher AM colonisation rate than tomato intercropped with tomato. Positive effects of AMF expressed as an increase of tomato biomass compared to the untreated control treatment could be observed in root as well as in shoot weights. A compensation of negative effects of F. oxysporum f. sp. lycopersici on tomato biomass by AMF was observed in the tomato/leek combination. The intercropping partners leek, cucumber, basil and tomato had no effect on F. oxysporum f. sp. lycopersici disease incidence or disease severity indicating no allelopathic suppression; however, tomato co-cultivated with tomato clearly showed a negative effect on one plant/pot with regard to biomass and disease severity of F. oxysporum f. sp. lycopersici. Nonetheless, bioprotective effects of AMF resulting in the decrease of F. oxysporum f. sp. lycopersici disease severity were evident in treatments with AMF and F. oxysporum f. sp. lycopersici co-inoculation. However, these bioprotective effects depended on the intercropping partner since these effects were only observed in the tomato/leek and tomato/basil combination and for the better developed plant of tomato/tomato. In conclusion, the effects of the intercropping partner on AMF colonisation of tomato are of great interest for crop plant communities and for the influences on each other. The outcome of the bioprotective

  3. 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

  4. Gibberellins interfere with symbiosis signaling and gene expression and alter colonization by arbuscular mycorrhizal fungi in Lotus japonicus.

    PubMed

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

    2015-02-01

    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. © 2015 American Society of Plant Biologists. All Rights Reserved.

  5. Context-dependency of arbuscular mycorrhizal fungi on plant-insect interactions in an agroecosystem

    PubMed Central

    Barber, Nicholas A.; Kiers, E. Toby; Hazzard, Ruth V.; Adler, Lynn S.

    2013-01-01

    Plants interact with a variety of other community members that have the potential to indirectly influence each other through a shared host plant. Arbuscular mycorrhizal fungi (AMF) are generally considered plant mutualists because of their generally positive effects on plant nutrient status and growth. AMF may also have important indirect effects on plants by altering interactions with other community members. By influencing plant traits, AMF can modify aboveground interactions with both mutualists, such as pollinators, and antagonists, such as herbivores. Because herbivory and pollination can dramatically influence plant fitness, comprehensive assessment of plant–AMF interactions should include these indirect effects. To determine how AMF affect plant–insect interactions, we grew Cucumis sativus (Cucurbitaceae) under five AMF inoculum treatments and control. We measured plant growth, floral production, flower size, and foliar nutrient content of half the plants, and transferred the other half to a field setting to measure pollinator and herbivore preference of wild insects. Mycorrhizal treatment had no effect on plant biomass or floral traits but significantly affected leaf nutrients, pollinator behavior, and herbivore attack. Although total pollinator visitation did not vary with AMF treatment, pollinators exhibited taxon-specific responses, with honey bees, bumble bees, and Lepidoptera all responding differently to AMF treatments. Flower number and size were unaffected by treatments, suggesting that differences in pollinator preference were driven by other floral traits. Mycorrhizae influenced leaf K and Na, but these differences in leaf nutrients did not correspond to variation in herbivore attack. Overall, we found that AMF indirectly influence both antagonistic and mutualistic insects, but impacts depend on the identity of both the fungal partner and the interacting insect, underscoring the context-dependency of plant–AMF interactions. PMID:24046771

  6. 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.

  7. Glomus intraradices dominates arbuscular mycorrhizal communities in a heavy textured agricultural soil.

    PubMed

    Mathimaran, N; Ruh, R; Vullioud, P; Frossard, E; Jansa, J

    2005-12-01

    Arbuscular mycorrhizal fungal (AMF) spore communities were surveyed in a long-term field fertilization experiment in Switzerland, where different amounts of phosphorus (P) were applied to soil. Plots receiving no P as well as plots systematically fertilized in excess to plant needs for 31 years were used to test the hypothesis that application of P fertilizer changes the composition and diversity of AMF communities. AMF spores were isolated from the field soil, identified, and counted so as to quantify the effect of P fertilization on AMF spore density, composition, and diversity. Trap cultures were established from field soil with four host plants (sunflower, leek, maize, and Crotalaria grahamiana), and the spore communities were then analyzed in substrate samples from the pots. Altogether, nine AMF species were detected in the soil. No evidence has been acquired for effect of P fertilization on spore density, composition, and diversity of AMF in both the field soil and in trap cultures. On the other hand, we observed strong effect of crop plant species on spore densities in the soil, the values being lowest under rapeseed and highest under Phacelia tanacetifolia covercrop. The identity of plant species in trap pots also significantly affected composition and diversity of associated AMF communities, probably due to preferential establishment of symbiosis between certain plant and AMF species. AMF spore communities under mycorrhizal host plants (wheat and Phacelia in the fields and four host plant species in trap pots) were dominated by a single AMF species, Glomus intraradices. This resulted in exceptionally low AMF spore diversity that seems to be linked to high clay content of the soil.

  8. Common and divergent roles of plant hormones in nodulation and arbuscular mycorrhizal symbioses.

    PubMed

    Foo, Eloise; Ferguson, Brett J; Reid, James B

    2014-06-18

    All of the classical plant hormones have been suggested to influence nodulation, including some that interact with the Autoregulation of Nodulation (AON) pathway. Leguminous plants strictly regulate the number of nodules formed through this AON pathway via a root-shoot-root loop that acts to suppress excessive nodulation. A related pathway, the Autoregulation of Mycorrhization (AOM) pathway controls the more ancient, arbuscular mycorrhizal (AM) symbiosis. A comparison of the published responses to the classical hormones in these 2 symbioses shows that most influence the symbioses in the same direction. This may be expected if they affect the symbioses via common components of these symbiotic regulatory pathways. However, some hormones influence these symbioses in opposite directions, suggesting a more complex relationship, and probably one that is not via the common components of these pathways. In a recent paper (1) we showed, using a genetic approach, that strigolactones and brassinosteroids do not act downstream of the AON genes examined and argued that they probably act independently to promote nodule formation. Recently it has been shown that the control of nodulation via the AON pathway involves mobile CLE peptide signals. It is therefore suggested that a more direct avenue to determine if the classical hormones play a direct role in the autoregulatory pathways is to further examine whether CLE peptides and other components of these processes can influence, or be influenced by, the classical hormones. Such studies and other comparisons between the nodulation and mycorrhizal symbioses should allow the role of the classical hormones in these critical symbioses to be rapidly advanced.

  9. Common and divergent roles of plant hormones in nodulation and arbuscular mycorrhizal symbioses.

    PubMed

    Foo, Eloise; Ferguson, Brett J; Reid, James B

    2014-01-01

    All of the classical plant hormones have been suggested to influence nodulation, including some that interact with the Autoregulation of Nodulation (AON) pathway. Leguminous plants strictly regulate the number of nodules formed through this AON pathway via a root-shoot-root loop that acts to suppress excessive nodulation. A related pathway, the Autoregulation of Mycorrhization (AOM) pathway controls the more ancient, arbuscular mycorrhizal (AM) symbiosis. A comparison of the published responses to the classical hormones in these 2 symbioses shows that most influence the symbioses in the same direction. This may be expected if they affect the symbioses via common components of these symbiotic regulatory pathways. However, some hormones influence these symbioses in opposite directions, suggesting a more complex relationship, and probably one that is not via the common components of these pathways. In a recent paper we showed, using a genetic approach, that strigolactones and brassinosteroids do not act downstream of the AON genes examined and argued that they probably act independently to promote nodule formation. Recently it has been shown that the control of nodulation via the AON pathway involves mobile CLE peptide signals. It is therefore suggested that a more direct avenue to determine if the classical hormones play a direct role in the autoregulatory pathways is to further examine whether CLE peptides and other components of these processes can influence, or be influenced by, the classical hormones. Such studies and other comparisons between the nodulation and mycorrhizal symbioses should allow the role of the classical hormones in these critical symbioses to be rapidly advanced.

  10. 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.

  11. [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.

  12. Indirect interactions between arbuscular mycorrhizal fungi and Spodoptera exigua alter photosynthesis and plant endogenous hormones.

    PubMed

    He, Lei; Li, Changyou; Liu, Runjin

    2017-08-01

    Peanut (Arachis hypogaea Linn. cv: Luhua 11) and tomato (Lycopersicon esculentum Mill. cv: Zhongshu 4) were inoculated with arbuscular mycorrhizal fungi (AMF) Funneliformis mosseae BEG167 (Fm), Rhizophagus intraradices BEG141 (Ri), and Glomus versiforme Berch (Gv), and/or Spodoptera exigua (S. exigua) under greenhouse conditions. Results indicated that feeding by S. exigua had little influence on colonization of peanut plants by AMF, but improved colonization of tomato by Fm and Gv. Feeding by S. exigua had little influence on leaf net photosynthetic rate, transpiration rate, and stomatal conductance of nonmycorrhizal peanut plants but significantly improved net photosynthetic rate and transpiration rate of mycorrhizal plants of both hosts. AMF with or without S. exigua inoculation improved host plant photosynthetic characteristics, growth, and hormone status. Fm showed maximum beneficial effects, followed by Gv. The concentrations and ratios of phytohormones abscisic acid (ABA), indole-3-acetic acid (IAA), gibberellin (GA), zeatin riboside (ZR), and jasmonic acid (JA) in the leaves of the host plants were changed due to the interaction between AMF and S. exigua. Generally, AMF with or without S. exigua inoculation increased the concentrations of GA, ZR, and JA and the ratios of IAA/ABA, GA/ABA, ZR/ABA, and IAA + GA + ZR/ABA, while feeding by S. exigua on nonmycorrhizal plants showed the opposite effect. The concentration of JA in the leaves of peanut and tomato inoculated with Fm or Fm + S. exigua was 1.9 and 1.9 times and 2.5 and 2.7 times, respectively, greater than that of the controls inoculated with neither. There was a negative correlation between the JA concentration and the survival percentage of S. exigua larva. We conclude that indirect interactions between AMF and insect herbivores changed the photosynthetic and hormone characteristics, and ratios of phytohormones, thereby revealing mechanisms of belowground-aboveground interactions.

  13. Context-dependency of arbuscular mycorrhizal fungi on plant-insect interactions in an agroecosystem.

    PubMed

    Barber, Nicholas A; Kiers, E Toby; Hazzard, Ruth V; Adler, Lynn S

    2013-01-01

    Plants interact with a variety of other community members that have the potential to indirectly influence each other through a shared host plant. Arbuscular mycorrhizal fungi (AMF) are generally considered plant mutualists because of their generally positive effects on plant nutrient status and growth. AMF may also have important indirect effects on plants by altering interactions with other community members. By influencing plant traits, AMF can modify aboveground interactions with both mutualists, such as pollinators, and antagonists, such as herbivores. Because herbivory and pollination can dramatically influence plant fitness, comprehensive assessment of plant-AMF interactions should include these indirect effects. To determine how AMF affect plant-insect interactions, we grew Cucumis sativus (Cucurbitaceae) under five AMF inoculum treatments and control. We measured plant growth, floral production, flower size, and foliar nutrient content of half the plants, and transferred the other half to a field setting to measure pollinator and herbivore preference of wild insects. Mycorrhizal treatment had no effect on plant biomass or floral traits but significantly affected leaf nutrients, pollinator behavior, and herbivore attack. Although total pollinator visitation did not vary with AMF treatment, pollinators exhibited taxon-specific responses, with honey bees, bumble bees, and Lepidoptera all responding differently to AMF treatments. Flower number and size were unaffected by treatments, suggesting that differences in pollinator preference were driven by other floral traits. Mycorrhizae influenced leaf K and Na, but these differences in leaf nutrients did not correspond to variation in herbivore attack. Overall, we found that AMF indirectly influence both antagonistic and mutualistic insects, but impacts depend on the identity of both the fungal partner and the interacting insect, underscoring the context-dependency of plant-AMF interactions.

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. Translocation and Utilization of Fungal Storage Lipid in the Arbuscular Mycorrhizal Symbiosis[w

    PubMed Central

    Bago, Berta; Zipfel, Warren; Williams, Rebecca M.; Jun, Jeongwon; Arreola, Raoul; Lammers, Peter J.; Pfeffer, Philip E.; Shachar-Hill, Yair

    2002-01-01

    The arbuscular mycorrhizal (AM) symbiosis is responsible for huge fluxes of photosynthetically fixed carbon from plants to the soil. Carbon is transferred from the plant to the fungus as hexose, but the main form of carbon stored by the mycobiont at all stages of its life cycle is triacylglycerol. Previous isotopic labeling experiments showed that the fungus exports this storage lipid from the intraradical mycelium (IRM) to the extraradical mycelium (ERM). Here, in vivo multiphoton microscopy was used to observe the movement of lipid bodies through the fungal colony and to determine their sizes, distribution, and velocities. The distribution of lipid bodies along fungal hyphae suggests that they are progressively consumed as they move toward growing tips. We report the isolation and measurements of expression of an AM fungal expressed sequence tag that encodes a putative acyl-coenzyme A dehydrogenase; its deduced amino acid sequence suggests that it may function in the anabolic flux of carbon from lipid to carbohydrate. Time-lapse image sequences show lipid bodies moving in both directions along hyphae and nuclear magnetic resonance analysis of labeling patterns after supplying 13C-labeled glycerol to either extraradical hyphae or colonized roots shows that there is indeed significant bidirectional translocation between IRM and ERM. We conclude that large amounts of lipid are translocated within the AM fungal colony and that, whereas net movement is from the IRM to the ERM, there is also substantial recirculation throughout the fungus. PMID:11788757

  5. 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.

  6. 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.

  7. 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

  8. Seedling performance of Phragmites australis (Cav.) Trin ex. Steudel in the presence of arbuscular mycorrhizal fungi.

    PubMed

    Wu, J; Ma, F; Wang, L; Yang, J; Huang, X; An, G; Liu, S

    2014-06-01

    Arbuscular mycorrhizal (AM) fungus-plant symbiosis may induce morphological, physiological and/or biochemical changes in the host plants. This study was performed to investigate the effects of AM fungi on Phragmites australis (Cav.) Trin ex. Steudel. Funnelliformis mosseae and Rhizophagus irregularis were chosen as inocula, and detailed attributes related to seedling performance (from seed to five-leaf stage), rhizospheric conditions and micro-organisms were measured and compared. Both of the chosen AM fungal inocula accelerated seed germination and enhanced growth and development, especially in the underground tissues, of seedlings. Specifically, AM fungal colonization improved the photosynthetic efficiency, rhizospheric soil respiration and absorption of certain nutrients in Ph. australis seedlings as well as the rhizospheric microbial metabolic activity and richness in different extents. However, the decreased metabolic diversity suggested that the effects of AM fungi on rhizospheric microbial communities are specific and selective. As a whole, F. mosseae showed greater improvements in the performance of Ph. australis seedlings than R. irregularis. In addition, the potential applications of AM fungi as a 'bio-accelerator', 'biofortifier', and 'bio-enhancer' in phyto-rhizoremediation have been discussed. The main findings could preliminarily reveal the mechanisms behind AM fungus-plant symbioses and could be referred to when optimizing combined phyto-rhizoremediation before practical applications take place. © 2014 The Society for Applied Microbiology.

  9. 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

  10. 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.

  11. [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.

  12. Host preferences of arbuscular mycorrhizal fungi colonizing annual herbaceous plant species in semiarid Mediterranean prairies.

    PubMed

    Torrecillas, E; Alguacil, M M; Roldán, A

    2012-09-01

    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.

  13. 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. Copyright © 2016. Published by Elsevier B.V.

  14. [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.

  15. 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

  16. Options of partners improve carbon for phosphorus trade in the arbuscular mycorrhizal mutualism.

    PubMed

    Argüello, Alicia; O'Brien, Michael J; van der Heijden, Marcel G A; Wiemken, Andres; Schmid, Bernhard; Niklaus, Pascal A

    2016-06-01

    The mutualism between plants and arbuscular mycorrhizal fungi (AMF) is widespread and has persisted for over 400 million years. Although this mutualism depends on fair resource exchange between plants and fungi, inequality exists among partners despite mechanisms that regulate trade. Here, we use (33) P and (14) C isotopes and a split-root system to test for preferential allocation and reciprocal rewards in the plant-AMF symbiosis by presenting a plant with two AMF that differ in cooperativeness. We found that plants received more (33) P from less cooperative AMF in the presence of another AMF species. This increase in (33) P resulted in a reduced (14) C cost per unit of (33) P from less cooperative AMF when alternative options were available. Our results indicate that AMF diversity promotes cooperation between plants and AMF, which may be an important mechanism maintaining the evolutionary persistence of and diversity within the plant-AMF mutualism. © 2016 John Wiley & Sons Ltd/CNRS.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Lipid content disturbance in the arbuscular mycorrhizal, Glomus irregulare grown in monoxenic conditions under PAHs pollution.

    PubMed

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

    2011-08-01

    Most polycyclic aromatic hydrocarbons (PAHs) are ubiquitous natural and/or anthropogenic pollutants that have adverse effects on the human health and the environment. Little is known about their potential effects on arbuscular mycorrhizal fungi (AMF). Thus, using monoxenic cultures, this work aims to study the impact of increasing concentrations (140 and 280 μM) of two PAHs [anthracene and benzo[a]pyrene (B[a]P)] on Glomus irregulare lipid content in relation with its development. Changes in the total lipids [fatty acids (FA), sterols, phospholipids (PL) and their associated FA (PLFA)] compositions and contents as well as [malondialdehyde (MDA)] production, of the AMF G. irregulare were examined. Direct toxic effects of both PAHs on the AMF were shown as compared to the control culture. The extraradical hyphae length and spore production were drastically restricted in the presence of PAHs. Significant decreases of the main membrane constituents, phosphatidylcholine (PC) and sterols (in particular 24-methycholesterol) were shown in G. irregulare grown under PAHs treatment. Moreover, PAHs exposure caused an oxidative stress in the AMF extraradical structures pointed out by an increase of the lipid peroxidation biomarker production (MDA). All the observed changes were less marked in presence of anthracene, which was found to be less toxic than B[a]P. Taken together, our results suggested that the drastic decrease of the AMF growth under PAHs pollution could partially be explained by depletions in sterols, PC and MDA accumulation. Copyright © 2011 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

  5. The Arbuscular Mycorrhizal Fungus Funneliformis mosseae Alters Bacterial Communities in Subtropical Forest Soils during Litter Decomposition.

    PubMed

    Gui, Heng; Purahong, Witoon; Hyde, Kevin D; Xu, Jianchu; Mortimer, Peter E

    2017-01-01

    Bacterial communities and arbuscular mycorrhizal fungi (AMF) co-occur in the soil, however, the interaction between these two groups during litter decomposition remains largely unexplored. In order to investigate the effect of AMF on soil bacterial communities, we designed dual compartment microcosms, where AMF (Funneliformis mosseae) was allowed access (AM) to, or excluded (NM) from, a compartment containing forest soil and litterbags. Soil samples from this compartment were analyzed at 0, 90, 120, 150, and 180 days. For each sample, Illumina sequencing was used to assess any changes in the soil bacterial communities. We found that most of the obtained operational taxonomic units (OTUs) from both treatments belonged to the phylum of Proteobacteria, Acidobacteria, and Actinobacteria. The community composition of bacteria at phylum and class levels was slightly influenced by both time and AMF. In addition, time and AMF significantly affected bacterial genera (e.g., Candidatus Solibacter, Dyella, Phenylobacterium) involved in litter decomposition. Opposite to the bacterial community composition, we found that overall soil bacterial OTU richness and diversity are relatively stable and were not significantly influenced by either time or AMF inoculation. OTU richness at phylum and class levels also showed consistent results with overall bacterial OTU richness. Our study provides new insight into the influence of AMF on soil bacterial communities at the genus level.

  6. 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.

  7. Arbuscular mycorrhizal fungi in a semiarid copper mining area in Brazil.

    PubMed

    da Silva, Gladstone Alves; Trufem, Sandra Farto Botelho; Saggin Júnior, Orivaldo José; Maia, Leonor Costa

    2005-01-01

    The occurrence of arbuscular mycorrhizal fungi (AMF) in a copper mining area was investigated. Soil samples were collected from six sites at the Mineração Caraiba, Bahia State, northeastern Brazil, comprising: (1) a site that receives the waste product; (2) a site that receives low grade deposits; (3) the interface between the caatinga and site 1; (4) the surroundings of the industrial area; (5) the site for extracting topsoil for land filling; (6) the preserved caatinga. Thirty-two plant species were identified around the collection locations. Trap cultures were maintained in the greenhouse for 3 months, using bahia grass ( Paspalum notatum Flügge) as the host plant. Spores were extracted from soil and 21 AMF species (15 Glomus and one of each of Acaulospora, Archaeospora, Entrophospora, Gigaspora , Paraglomus and Scutellospora) were identified. In site 1, plants or AMF were not found during the dry season. Site 6, with native vegetation, had the highest number of plants and AMF species. The disturbed sites showed less plant diversification, with the community of AMF being quantitative and qualitatively affected by disturbance.

  8. 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

  9. 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.

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

    PubMed

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

    2016-01-01

    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. 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. 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. 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.

  11. Variable responses of old-field perennials to arbuscular mycorrhizal fungi and phosphorus source.

    PubMed

    Reynolds, Heather L; Vogelsang, Keith M; Hartley, Anne E; Bever, James D; Schultz, P A

    2006-03-01

    If arbuscular mycorrhizal fungi (AMF) promote phosphorus partitioning of plant hosts, they could provide one mechanism for the maintenance of plant community diversity. We investigated whether AMF improved the ability of old field perennials to grow on a range of phosphorus sources and whether AMF facilitated differential performance of plant species on different phosphorus sources (phosphorus niche partitioning). We manipulated form of phosphorus (control versus different inorganic and organic sources) and AM fungal species (control versus four individual AMF species or an AMF community) for five old field perennials grown in a greenhouse in individual culture. Based on biomass after four months of growth, we found no evidence for phosphorus niche partitioning. Rather, we found that effects of AMF varied from parasitic to mutualistic depending on plant species, AMF species, and phosphorus source (significant Plant x Fungus x Phosphorus interaction). Our results suggest that the degree of AMF benefit to a plant host depends not only on AMF species, plant species, and soil phosphorus availability (as has also been found in other work), but can also depend on the form of soil phosphorus. Thus, the position of any AMF species along the mutualism to parasitism continuum may be a complex function of local conditions, and this has implications for understanding plant competitive balance in the field.

  12. Nitrogen-fixing bacteria and arbuscular mycorrhizal fungi in Piptadenia gonoacantha (Mart.) Macbr.

    PubMed

    Júnior, Joel Quintino de Oliveira; Jesus, Ederson da Conceição; Lisboa, Francy Junio; Berbara, Ricardo Luis Louro; Faria, Sergio Miana de

    The family Leguminosae comprises approximately 20,000 species that mostly form symbioses with arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (NFB). This study is aimed at investigating and confirming the dependence on nodulation and biological nitrogen fixation in the specie Piptadenia gonoacantha (Mart.) Macbr., which belongs to the Piptadenia group. Two consecutive experiments were performed in a greenhouse. The experiments were fully randomized with six replicates and a factorial scheme. For the treatments, the two AMF species and three NFB strains were combined to nodulate P. gonoacantha in addition to the control treatments. The results indicate this species' capacity for nodulation without the AMF; however, the AMF+NFB combinations yielded a considerable gain in P. gonoacantha shoot weight compared with the treatments that only included inoculating with bacteria or AMF. The results also confirm that the treatment effects among the AMF+NFB combinations produced different shoot dry weight/root dry weight ratios. We conclude that AMF is not necessary for nodulation and that this dependence improves species development because plant growth increases upon co-inoculation. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

  13. 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.

  14. Phosphorus, arbuscular mycorrhizal fungi and performance of the wetland plant Lythrum salicaria L. under inundated conditions.

    PubMed

    Stevens, K J; Spender, S W; Peterson, R L

    2002-12-01

    The role of arbuscular mycorrhizal (AM) fungi in aquatic and semi-aquatic environments is poorly understood, although they may play a significant role in the establishment and maintenance of wetland plant communities. We tested the hypothesis that AM fungi have little effect on plant response to phosphorus (P) supply in inundated soils as evidenced by an absence of increased plant performance in inoculated (AM+) versus non-inoculated (AM-) Lythrum salicaria plants grown under a range of P availabilities (0-40 mg/l P). We also assessed the relationship between P supply and levels of AM colonization under inundated conditions. The presence of AM fungi had no detectable benefit for any measures of plant performance (total shoot height, shoot dry weight, shoot fresh weight, root fresh weight, total root length or total root surface area). AM+ plants displayed reduced shoot height at 10 mg/l P. Overall, shoot fresh to dry weight ratios were higher in AM+ plants although the biological significance of this was not determined. AM colonization levels were significantly reduced at P concentrations of 5 mg/l and higher. The results support the hypothesis that AM fungi have little effect on plant response to P supply in inundated conditions and suggest that the AM association can become uncoupled at relatively high levels of P supply.

  15. Evidence for functional redundancy in arbuscular mycorrhizal fungi and implications for agroecosystem management.

    PubMed

    Gosling, Paul; Jones, Julie; Bending, Gary D

    2016-01-01

    Arbuscular mycorrhizal (AM) fungi provide benefits to host plants and show functional diversity, with evidence of functional trait conservation at the family level. Diverse communities of AM fungi ought therefore to provide increased benefits to the host, with implications for the management of sustainable agroecosystems. However, this is often not evident in the literature, with diversity saturation at low species number. Growth and nutrient uptake were measured in onions in the glasshouse on AM-free phosphorus (P)-poor soil, inoculated with between one and seven species of AM fungi in all possible combinations. Inoculation with AM fungi increased shoot dry weight as well as P and copper concentrations in shoots but reduced the concentration of potassium and sulphur. There was little evidence of increased benefit from high AM fungal diversity, and increasing diversity beyond three species did not result in significantly higher shoot weight or P or Cu concentrations. Species of Glomeraceae had the greatest impact on growth and nutrient uptake, while species of Acaulospora and Racocetra did not have a significant impact. Failure to show a benefit from high AM fungal diversity in this and other studies may be the result of experimental conditions, with the benefits of AM fungal diversity only becoming apparent when the host plant is faced with multiple stress factors. Replicating the complex interactions between AM fungi, the host plant and their environment in the laboratory in order to fully understand these interactions is a major challenge to AM research.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. The impact of tillage practices on arbuscular mycorrhizal fungal diversity in subtropical crops.

    PubMed

    Alguacil, M M; Lumini, E; Roldán, A; Salinas-García, J R; Bonfante, P; Bianciotto, V

    2008-03-01

    Arbuscular mycorrhizal fungi (AMF) are a main component of soil microbiota in most agrosystems. As obligately mutualistic symbionts, they colonize the roots of the majority of plants, including crop plants. We used molecular techniques to investigate how different tillage systems (moldboard, shred-bedding, subsoil-bedding, and no tillage) can influence the AM fungal community colonizing maize, bean, and sorghum roots in an experimental site located in northern Tamaulipas, Mexico. Roots from 36 plants were analyzed using AM fungal-specific primers to partially amplify the small subunit (SSU) of the ribosomal DNA genes. More than 880 clones were screened for restriction fragment length polymorphism (RFLP) variation, and 173 of these were sequenced. Ten AM fungal types were identified and clustered into three AM fungal families: Gigasporaceae, Glomaceae, and Paraglomaceae. Glomus was the dominating taxon in all the samples. Four of the 10 identified types were distinct from any previously published sequences and could correspond to either known unsequenced species or unknown species. The fungal diversity was low in the four agriculture management systems, but the multidimensional scaling (MDS) analysis and log-linear-saturated model indicated that the composition of the AMF community was significantly affected by the tillage system. In conclusion, since some fungal types were treatment specific, agricultural practices could directly or indirectly influence AM biodiversity.

  7. 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

  8. 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.

  9. Phytoprotective effect of arbuscular mycorrhizal fungi species against arsenic toxicity in tropical leguminous species.

    PubMed

    de Melo, Rangel Wesley; Schneider, Jerusa; de Souza, Costa Enio Tarso; Sousa, Soares Cláudio Roberto Fonsêca; Guimarães, Guilherme Luiz Roberto; de Souza, Moreira Fatima Maria

    2014-01-01

    Arbuscular mycorrhizal fungi (AMF) improve the tolerance of hosting plants to arsenic (As) in contaminated soils. This work assessed the phytoprotective effect of Glomus etunicatum, Acaulospora morrowiae, Gigaspora gigantea, and Acaulospora sp. on four leguminous species (Acacia mangium, Crotalaria juncea, Enterolobium contortisiliquum, and Stizolobium aterrimum) in an As-contaminated soil from a gold mining area. AMF root colonization, biomass production, As and P accumulation, as well as arsenic translocation index (TI) from roots to shoots were measured. The AMF phytoprotective effect was assessed by the P/As ratio and the activity of plant antioxidant enzymes. The AMF colonization ranged from 24 to 28%. In general, all leguminous species had low As TI when inoculated with AMF species. Inoculation of C. juncea with Acaulospora sp. improved significantly As accumulation in roots, and decreased the activity of ascorbate peroxidase (APX) and superoxide dismutase (SOD), highlighting its phytoprotective effect and the potential use of this symbiosis for phytoremediation of As-contaminated soils. However, S. aterrimum has also shown a potential for phytoremediation irrespectively of AMF inoculation. APX was a good indicator of the phytoprotective effect against As contamination in C. juncea and A. mangium. In general P/As ratio in shoots was the best indicator of the phytoprotective effect of all AMF species in all plant species.

  10. 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

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

    PubMed

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

    2017-01-01

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

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. Development of soils and communities of plants and arbuscular mycorrhizal fungi on West Virginia surface mines.

    PubMed

    Levy, Michael A; Cumming, Jonathan R

    2014-11-01

    Surface mining followed by reclamation to pasture is a major driver of land use and cover change in Appalachia. Prior research suggests that many aspects of ecosystem recovery are either slow or incomplete. We examined ecosystem structure-including soil physical and chemical properties, arbuscular mycorrhizal fungal (AMF) infectivity and community composition, and plant diversity and community composition-on a chronosequence of pasture-reclaimed surface mines and a non-mined pasture in northern West Virginia. Surface mining and reclamation dramatically altered ecosystem structure. Some aspects of ecosystem structure, including many measures of soil chemistry and infectivity of AMF, returned rapidly to levels found on the non-mined reference site. Other aspects of ecosystem structure, notably soil physical properties and AMF and plant communities, showed incomplete or no recovery over the short-to-medium term. In addition, invasive plants were prevalent on reclaimed mine sites. The results point to the need for investigation on how reclamation practices could minimize establishment of exotic invasive plant species and reduce the long-term impacts of mining on ecosystem structure and function.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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).

  12. Linking the community structure of arbuscular mycorrhizal fungi and plants: a story of interdependence?

    PubMed

    Horn, Sebastian; Hempel, Stefan; Verbruggen, Erik; Rillig, Matthias C; Caruso, Tancredi

    2017-06-01

    Arbuscular mycorrhizal fungi (AMF) are crucial to plants and vice versa, but little is known about the factors linking the community structure of the two groups. We investigated the association between AMF and the plant community structure in the nearest neighborhood of Festuca brevipila in a semiarid grassland with steep environmental gradients, using high-throughput sequencing of the Glomeromycotina (former Glomeromycota). We focused on the Passenger, Driver and Habitat hypotheses: (i) plant communities drive AMF (passenger); (ii) AMF communities drive the plants (driver); (iii) the environment shapes both communities causing covariation. The null hypothesis is that the two assemblages are independent and this study offers a spatially explicit novel test of it in the field at multiple, small scales. The AMF community consisted of 71 operational taxonomic units, the plant community of 47 species. Spatial distance and spatial variation in the environment were the main determinants of the AMF community. The structure of the plant community around the focal plant was a poor predictor of AMF communities, also in terms of phylogenetic community structure. Some evidence supports the passenger hypothesis, but the relative roles of the factors structuring the two groups clearly differed, leading to an apparent decoupling of the two assemblages at the relatively small scale of this study. Community phylogenetic structure in AMF suggests an important role of within-assemblage interactions.

  13. Simulated nitrogen deposition affects community structure of arbuscular mycorrhizal fungi in northern hardwood forests.

    PubMed

    VAN Diepen, Linda T A; Lilleskov, Erik A; Pregitzer, Kurt S

    2011-02-01

    Our previous investigation found elevated nitrogen deposition caused declines in abundance of arbuscular mycorrhizal fungi (AMF) associated with forest trees, but little is known about how nitrogen affects the AMF community composition and structure within forest ecosystems. We hypothesized that N deposition would lead to significant changes in the AMF community structure. We studied the diversity and community structure of AMF in northern hardwood forests after more than 12 years of simulated nitrogen deposition. We performed molecular analyses on maple (Acer spp.) roots targeting the 18S rDNA region using the fungal-specific primers AM1 and NS31. PCR products were cloned and identified using restriction fragment length polymorphism (RFLP) and sequencing. N addition significantly altered the AMF community structure, and Glomus group A dominated the AMF community. Some Glomus operational taxonomic units (OTUs) responded negatively to N inputs, whereas other Glomus OTUs and an Acaulospora OTU responded positively to N inputs. The observed effect on community structure implies that AMF species associated with maples differ in their response to elevated nitrogen. Given that functional diversity exists among AMF species and that N deposition has been shown to select less beneficial fungi in some ecosystems, this change in community structure could have implications for the functioning of this type of ecosystem. Published 2011. This article is a US Government work and is in the public domain in the USA.

  14. Meta-analysis of interactions between arbuscular mycorrhizal fungi and biotic stressors of plants.

    PubMed

    Yang, Haishui; Dai, Yajun; Wang, Xiaohua; Zhang, Qian; Zhu, Liqun; Bian, Xinmin

    2014-01-01

    Naturally, simultaneous interactions occurred among plants, herbivores, and soil biota, that is, arbuscular mycorrhizal fungi (AMF), nematodes, and fungal pathogens. These multiple interactions play fundamental roles in driving process, structure, and functioning of ecosystems. In this study, we conducted a meta-analysis with 144 papers to investigate the interactions between AMF and plant biotic stressors and their effects on plant growth performance. We found that AMF enhanced plant tolerance to herbivores, nematodes, and fungal pathogens. We also found reciprocal inhibition between AMF and nematodes as well as fungal pathogens, but unidirectional inhibition for AMF on herbivores. Negative effects of AMF on biotic stressors of plants depended on herbivore feeding sites and actioning modes of fungal pathogens. More performance was reduced in root-feeding than in shoot-feeding herbivores and in rotting- than in wilt-fungal pathogens. However, no difference was found for AMF negative effects between migratory and sedentary nematodes. In return, nematodes and fungal pathogens generated more reduction of root colonization in Non-Glomeraceae than in Glomeraceae. Our results suggested that AMF positive effects on plants might be indirectly mediated by competitive inhibition with biotic stressors of plants. These positive and negative interactions make potential contributions to maintaining ecosystem stability and functioning.

  15. 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

  16. 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.

  17. Effect of Rice Cultivation Systems on Indigenous Arbuscular Mycorrhizal Fungal Community Structure

    PubMed Central

    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. PMID:23719585

  18. 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

  19. Diversity of Arbuscular Mycorrhizal Fungi in a Brazilian Atlantic Forest Toposequence.

    PubMed

    Bonfim, Joice Andrade; Vasconcellos, Rafael Leandro Figueiredo; Gumiere, Thiago; de Lourdes Colombo Mescolotti, Denise; Oehl, Fritz; Nogueira Cardoso, Elke Jurandy Bran

    2016-01-01

    The diversity of arbuscular mycorrhizal fungi (AMF) was studied in the Atlantic Forest in Serra do Mar Park (SE Brazil), based on seven host plants in relationship to their soil environment, altitude and seasonality. The studied plots along an elevation gradient are located at 80, 600, and 1,000 m. Soil samples (0-20 cm) were collected in four seasons from SE Brazilian winter 2012 to autumn 2013. AMF spores in rhizosperic soils were morphologically classified and chemical, physical and microbiological soil caracteristics were determined. AMF diversity in roots was evaluated using the NS31/AM1 primer pair, with subsequent cloning and sequencing. In the rhizosphere, 58 AMF species were identified. The genera Acaulospora and Glomus were predominant. However, in the roots, only 14 AMF sequencing groups were found and all had high similarity to Glomeraceae. AMF species identities varied between altitudes and seasons. There were species that contributed the most to this variation. Some soil characteristics (pH, organic matter, microbial activity and microbial biomass carbon) showed a strong relationship with the occurrence of certain species. The highest AMF species diversity, based on Shannon's diversity index, was found for the highest altitude. Seasonality did not affect the diversity. Our results show a high AMF diversity, higher than commonly found in the Atlantic Forest. The AMF detected in roots were not identical to those detected in rhizosperic soil and differences in AMF communities were found in different altitudes even in geographically close-lying sites.

  20. Patterns of Arbuscular Mycorrhizal Fungal Distribution on Mainland and Island Sandy Coastal Plain Ecosystems in Brazil.

    PubMed

    da Silva, Iolanda Ramalho; de Souza, Francisco Adriano; da Silva, Danielle Karla Alves; Oehl, Fritz; Maia, Leonor Costa

    2017-04-11

    Although sandy coastal plains are important buffer zones to protect the coast line and maintain biological diversity and ecosystem services, these ecosystems have been endangered by anthropogenic activities. Thus, information on coastal biodiversity and forces shaping coastal biological diversity are extremely important for effective conservation strategies. In this study, we aimed to compare arbuscular mycorrhizal (AM) fungal communities from soil samples collected on the mainland and nearby islands located in Brazilian sandy coastal plain ecosystems (Restingas) to get information about AM fungal biogeography and identify factors shaping these communities. Soil samples were collected in 2013 and 2014 on the beachfront of the tropical sandy coastal plain at six sites (three island and three mainland locations) across the northeast, southeast, and south regions of Brazil. Overall, we recorded 53 AM fungal species from field and trap culture samples. The richness and diversity of AM fungal species did not differ between mainland and island locations, but AM fungal community assemblages were different between mainland and island environments and among most sites sampled. Glomeromycota communities registered from island samples showed higher heterogeneity than communities from mainland samples. Sandy coastal plains harbor diverse AM fungal communities structured by climatic, edaphic, and spatial factors, while the distance from the colonizing source (mainland environments) does not strongly affect the AM fungal communities in Brazilian coastal environments.

  1. Genome of an arbuscular mycorrhizal fungus provides insight into the oldest plant symbiosis

    PubMed Central

    Tisserant, Emilie; Malbreil, Mathilde; Kuo, Alan; Kohler, Annegret; Symeonidi, Aikaterini; Balestrini, Raffaella; Charron, Philippe; Duensing, Nina; Frei dit Frey, Nicolas; Gianinazzi-Pearson, Vivienne; Gilbert, Luz B.; Handa, Yoshihiro; Herr, Joshua R.; Hijri, Mohamed; Koul, Raman; Kawaguchi, Masayoshi; Krajinski, Franziska; Lammers, Peter J.; Masclaux, Frederic G.; Murat, Claude; Morin, Emmanuelle; Ndikumana, Steve; Pagni, Marco; Petitpierre, Denis; Requena, Natalia; Rosikiewicz, Pawel; Riley, Rohan; Saito, Katsuharu; San Clemente, Hélène; Shapiro, Harris; van Tuinen, Diederik; Bécard, Guillaume; Bonfante, Paola; Paszkowski, Uta; Shachar-Hill, Yair Y.; Tuskan, Gerald A.; Young, J. Peter W.; Sanders, Ian R.; Henrissat, Bernard; Rensing, Stefan A.; Grigoriev, Igor V.; Corradi, Nicolas; Roux, Christophe; Martin, Francis

    2013-01-01

    The mutualistic symbiosis involving Glomeromycota, a distinctive phylum of early diverging Fungi, is widely hypothesized to have promoted the evolution of land plants during the middle Paleozoic. These arbuscular mycorrhizal fungi (AMF) perform vital functions in the phosphorus cycle that are fundamental to sustainable crop plant productivity. The unusual biological features of AMF have long fascinated evolutionary biologists. The coenocytic hyphae host a community of hundreds of nuclei and reproduce clonally through large multinucleated spores. It has been suggested that the AMF maintain a stable assemblage of several different genomes during the life cycle, but this genomic organization has been questioned. Here we introduce the 153-Mb haploid genome of Rhizophagus irregularis and its repertoire of 28,232 genes. The observed low level of genome polymorphism (0.43 SNP per kb) is not consistent with the occurrence of multiple, highly diverged genomes. The expansion of mating-related genes suggests the existence of cryptic sex-related processes. A comparison of gene categories confirms that R. irregularis is close to the Mucoromycotina. The AMF obligate biotrophy is not explained by genome erosion or any related loss of metabolic complexity in central metabolism, but is marked by a lack of genes encoding plant cell wall-degrading enzymes and of genes involved in toxin and thiamine synthesis. A battery of mycorrhiza-induced secreted proteins is expressed in symbiotic tissues. The present comprehensive repertoire of R. irregularis genes provides a basis for future research on symbiosis-related mechanisms in Glomeromycota. PMID:24277808

  2. 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.

  3. 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.

  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. 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).

  6. 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. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  7. 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

  8. 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.

  9. 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.

  10. Diversity of Rhizosphere Soil Arbuscular Mycorrhizal Fungi in Various Soybean Cultivars under Different Continuous Cropping Regimes

    PubMed Central

    Jie, Weiguang; Liu, Xiaorui; Cai, Baiyan

    2013-01-01

    Recent studies have shown that continuous cropping in soybean causes substantial changes to the microbial community in rhizosphere soil. In this study, we investigated the effects of continuous cropping for various time periods on the diversity of rhizosphere soil arbuscular mycorrhizal (AM) fungi in various soybean cultivars at the branching stage. The soybean cultivars Heinong 37 (an intermediate cultivar), Heinong 44 (a high-fat cultivar) and Heinong 48 (a high-protein cultivar) were seeded in a field and continuously cropped for two or three years. We analyzed the diversity of rhizosphere soil AM fungi of these soybean plants at the branching stage using morphological and denaturing gradient gel electrophoresis (DGGE) techniques. The clustering analysis of unweighted pair-group method with arithmetic averages (UPGMA) was then used to investigate the AM fungal community shifts. The results showed that increasing the number of years of continuous cropping can improve the colonization rate of AM fungi in different soybean cultivars at the branching stage. The dominant AM fungi in the experimental fields were Funneliformismosseae and Glomus spp. The number of years of continuous cropping and the soybean cultivar both had obvious effects on the diversity of AM fungi, which was consistent with the results of colonization rate analysis. This study establishes a basis for screening dominant AM fungi of soybean. In addition, the results of this study may be useful for the development of AM fungal inoculants. PMID:23977368

  11. [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.

  12. 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.

  13. 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.

  14. 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.

  15. Succession of arbuscular mycorrhizal fungi along a 52-year agricultural recultivation chronosequence.

    PubMed

    Roy, Julien; Reichel, Rüdiger; Brüggemann, Nicolas; Hempel, Stefan; Rillig, Matthias C

    2017-09-01

    Arbuscular mycorrhizal (AM) fungi provide a range of functions in natural and managed ecosystems. However, the trajectory of AM fungal diversity after land degradation is poorly known. We studied the succession of AM fungi along an agricultural recultivation chronosequence after open-cast mining near Cologne, Germany. We used high-throughput sequencing of the large-subunit ribosomal RNA genes to characterize the soil AM fungal communities of 10 agricultural fields spanning 52 years of recultivation. During three years, soils are recultivated with a legume, and then converted to agriculture to be later returned to local farmers implementing conventional agriculture. Our data reveal a quick and strong recovery of AM fungal richness after a few years of recultivation, but also a rapid decline following years of conventional agriculture. The community structure was strongly correlated to mineral nitrogen and phosphorus, richness peaking at high N:P ratio. This work represents the first molecular data documenting temporal patterns of AM fungal communities in agriculture; it shows the deleterious effect of conventional agricultural practices on AM fungal communities developing over time. Nonetheless, the highly dynamic nature of AM fungal communities suggests strategies for site-level management for which considering N:P stoichiometry is crucial. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  16. Effect of Organic Farming on Spore Diversity of Arbuscular Mycorrhizal Fungi and Glomalin in Soil

    PubMed Central

    Lee, Ji-Eun

    2009-01-01

    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. PMID:23983547

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Relative Importance of Individual Climatic Drivers Shaping Arbuscular Mycorrhizal Fungal Communities.

    PubMed

    Xiang, Dan; Veresoglou, Stavros D; Rillig, Matthias C; Xu, Tianle; Li, Huan; Hao, Zhipeng; Chen, Baodong

    2016-08-01

    The physiological tolerance hypothesis (PTH) postulates that it is the tolerance of species to climatic factors that determines overall community richness. Here, we tested whether a group of mutualistic microbes, Glomeromycota, is distributed in semi-arid environments in ways congruent with the PTH. For this purpose, we modeled with climatic predictors the niche of each of the four orders of Glomeromycota and identified predictors of arbuscular mycorrhizal (AM) fungal operational taxonomic unit (OTU) richness. Our dataset consisted of 50 paired grassland and farmland sites in the farming-pastoral ecotone of northern China. We observed shifts in the relative abundance of AM fungal orders in response to climatic variables but also declines in OTU richness in grassland sites that had experienced high precipitation during the preceding year which was incongruous with the PTH. We found pronounced differences across groups of Glomeromycotan fungi in their responses to climatic variables and identified strong dependencies of AM fungal communities on precipitation. Given that precipitation is expected to further decline in the farming-pastoral ecotone over the coming years and that mycorrhiza represents an integral constituent of ecosystem functioning, it is likely that the ecosystem services in the region will change accordingly.

  8. 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. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

  9. Identification and Isolation of Two Ascomycete Fungi from Spores of the Arbuscular Mycorrhizal Fungus Scutellospora castanea

    PubMed Central

    Hijri, Mohamed; Redecker, Dirk; Petetot, Jean A. MacDonald-Comber; Voigt, Kerstin; Wöstemeyer, Johannes; Sanders, Ian R.

    2002-01-01

    Two filamentous fungi with different phenotypes were isolated from crushed healthy spores or perforated dead spores of the arbuscular mycorrhizal fungus (AMF) Scutellospora castanea. Based on comparative sequence analysis of 5.8S ribosomal DNA and internal transcribed spacer fragments, one isolate, obtained from perforated dead spores only, was assigned to the genus Nectria, and the second, obtained from both healthy and dead spores, was assigned to Leptosphaeria, a genus that also contains pathogens of plants in the Brassicaceae. PCR and randomly amplified polymorphic DNA-PCR analyses, however, did not indicate similarities between pathogens and the isolate. The presence of the two isolates in both healthy spores and perforated dead spores of S. castanea was finally confirmed by transmission electron microscopy by using distinctive characteristics of the isolates and S. castanea. The role of this fungus in S. castanea spores remains unclear, but the results serve as a strong warning that sequences obtained from apparently healthy AMF spores cannot be presumed to be of glomalean origin and that this could present problems for studies on AMF genes. PMID:12200315

  10. 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.

  11. Detection of a novel intracellular microbiome hosted in arbuscular mycorrhizal fungi

    PubMed Central

    Desirò, Alessandro; Salvioli, Alessandra; Ngonkeu, Eddy L; Mondo, Stephen J; Epis, Sara; Faccio, Antonella; Kaech, Andres; Pawlowska, Teresa E; Bonfante, Paola

    2014-01-01

    Arbuscular mycorrhizal fungi (AMF) are important members of the plant microbiome. They are obligate biotrophs that colonize the roots of most land plants and enhance host nutrient acquisition. Many AMF themselves harbor endobacteria in their hyphae and spores. Two types of endobacteria are known in Glomeromycota: rod-shaped Gram-negative Candidatus Glomeribacter gigasporarum, CaGg, limited in distribution to members of the Gigasporaceae family, and coccoid Mollicutes-related endobacteria, Mre, widely distributed across different lineages of AMF. The goal of the present study is to investigate the patterns of distribution and coexistence of the two endosymbionts, CaGg and Mre, in spore samples of several strains of Gigaspora margarita. Based on previous observations, we hypothesized that some AMF could host populations of both endobacteria. To test this hypothesis, we performed an extensive investigation of both endosymbionts in G. margarita spores sampled from Cameroonian soils as well as in the Japanese G. margarita MAFF520054 isolate using different approaches (molecular phylotyping, electron microscopy, fluorescence in situ hybridization and quantitative real-time PCR). We found that a single AMF host can harbour both types of endobacteria, with Mre population being more abundant, variable and prone to recombination than the CaGg one. Both endosymbionts seem to retain their genetic and lifestyle peculiarities regardless of whether they colonize the host alone or together. These findings show for the first time that fungi support an intracellular bacterial microbiome, in which distinct types of endobacteria coexist in a single cell. PMID:24008325

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Bacterial effects on arbuscular mycorrhizal fungi and mycorrhiza development as influenced by the bacteria, fungi, and host plant.

    PubMed

    Pivato, Barbara; Offre, Pierre; Marchelli, Sara; Barbonaglia, Bruno; Mougel, Christophe; Lemanceau, Philippe; Berta, Graziella

    2009-02-01

    Bacterial strains from mycorrhizal roots (three belonging to Comamonadaceae and one to Oxalobacteraceae) and from non-mycorrhizal roots (two belonging to Comamonadaceae) of Medicago truncatula and two reference strains (Collimonas fungivorans Ter331 and Pseudomonas fluorescens C7R12) were tested for their effect on the in vitro saprophytic growth of Glomus mosseae BEG12 and on its colonization of M. truncatula roots. Only the Oxalobacteraceae strain, isolated from barrel medic mycorrhizal roots, and the reference strain P. fluorescens C7R12 promoted both the saprophytic growth and root colonization of G. mosseae BEG12, indicating that they acted as mycorrhiza helper bacteria. Greatest effects were achieved by P. fluorescens C7R12 and its influence on the saprophytic growth of G. mosseae was compared to that on Gigaspora rosea BEG9 to determine if the bacterial stimulation was fungal specific. This fungal specificity, together with plant specificity, was finally evaluated by comparing bacterial effects on arbuscular mycorrhizal symbiosis when each of the fungal species was inoculated to two different plant species (M. truncatula and Lycopersicon esculentum). The results obtained showed that promotion of saprophytic growth by P. fluorescens C7R12 was expressed in vitro towards G. mosseae but not towards G. rosea. Bacterial promotion of mycorhization was also expressed towards G. mosseae, but not G. rosea, in roots of M. truncatula and L. esculentum. Taken together, results indicated that enhancement of arbuscular mycorrhiza development was only induced by a limited number of bacteria, promotion by the most efficient bacterial strain being fungal and not plant specific.

  2. 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

  3. Application of Arbuscular Mycorrhizal Fungi during the Acclimatization of Alpinia purpurata to Induce Tolerance to Meloidogyne arenaria

    PubMed Central

    da Silva Campos, Maryluce Albuquerque; da Silva, Fábio Sérgio Barbosa; Yano-Melo, Adriana Mayumi; de Melo, Natoniel Franklin; Maia, Leonor Costa

    2017-01-01

    An experiment was conducted to evaluate the tolerance of micropropagated and mycorrhized alpinia plants to the parasite Meloidogyne arenaria. The experimental design was completely randomized with a factorial arrangement of four inoculation treatments with arbuscular mycorrhizal fungi (AMF) (Gigaspora albida, Claroideoglomus etunicatum, Acaulospora longula, and a non-inoculated control) in the presence or absence of M. arenaria with five replicates. The following characteristics were evaluated after 270 days of mycorrhization and 170 days of M. arenaria inoculation: height, number of leaves and tillers, fresh mass of aerial and subterranean parts, dry mass of aerial parts, foliar area, nutritional content, mycorrhizal colonization, AMF sporulation, and the number of galls, egg masses, and eggs. The results indicated a significant interaction between the treatments for AMF spore density, total mycorrhizal colonization, and nutrient content (Zn, Na, and N), while the remaining parameters were influenced by either AMF or nematodes. Plants inoculated with A. longula or C. etunicatum exhibited greater growth than the control. Lower N content was observed in plants inoculated with AMF, while Zn and Na were found in larger quantities in plants inoculated with C. etunicatum. Fewer galls were observed on mycorrhized plants, and egg mass production and the number of eggs were lower in plants inoculated with G. albida. Plants inoculated with A. longula showed a higher percentage of total mycorrhizal colonization in the presence of the nematode. Therefore, the association of micropropagated alpinia plants and A. longula enhanced tolerance to parasitism by M. arenaria. PMID:28592951

  4. 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.

  5. 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

  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. Arbuscular mycorrhizal fungi and rhizobium facilitate nitrogen uptake and transfer in soybean/maize intercropping system

    PubMed Central

    Meng, Lingbo; Zhang, Aiyuan; Wang, Fei; Han, Xiaoguang; Wang, Dejiang; Li, Shumin

    2015-01-01

    The tripartite symbiosis between legumes, rhizobia and mycorrhizal fungi are generally considered to be beneficial for the nitrogen (N) uptake of legumes, but the facilitation of symbiosis in legume/non-legume intercropping systems is not clear. Therefore, the aims of the research are as follows: (1) to verify if the dual inoculation can facilitate the N uptake and N transfer in maize/soybean intercropping systems and (2) to calculate how much N will be transferred from soybean to maize. A pot experiment with different root separations [solid barrier, mesh (30 μm) barrier and no barrier] was conducted, and the 15N isotopic tracing method was used to calculate how much N transferred from soybean to maize inoculated with arbuscular mycorrhizal fungi (AMF) and rhizobium in a soybean (Glycine max L.cv. Dongnong No. 42)/maize (Zea mays L.cv. Dongnong No. 48) intercropping system. Compared with the Glomus mosseae inoculation (G.m.), Rhizobium SH212 inoculation (SH212), no inoculation (NI), the dual inoculation (SH212+G.m.) increased the N uptake of soybean by 28.69, 39.58, and 93.07% in a solid barrier system. N uptake of maize inoculated with both G. mosseae and rhizobium was 1.20, 1.28, and 1.68 times more than that of G.m., SH212 and NI, respectively, in solid barrier treatments. In addition, the amount of N transferred from soybean to maize in a dual inoculation system with a mesh barrier was 7.25, 7.01, and 11.45 mg more than that of G.m., SH212 and NI and similarly, 6.40, 7.58, and 12.46 mg increased in no barrier treatments. Inoculating with both AMF and rhizobium in the soybean/maize intercropping system improved the N fixation efficiency of soybean and promoted N transfer from soybean to maize, resulting in the improvement of yield advantages of legume/non-legume intercropping. PMID:26029236

  8. 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

  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. Resistance Responses of Potato to Vesicular-Arbuscular Mycorrhizal Fungi under Varying Abiotic Phosphorus Levels 1

    PubMed Central

    McArthur, David A. J.; Knowles, N. Richard

    1992-01-01

    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 (ACCox) 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

  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. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Seasonal dispersal of arbuscular mycorrhizal fungi by spiny rats in a neotropical forest.

    PubMed

    Mangan, Scott A; Adler, Gregory H

    2002-05-01

    Many species of neotropical rodents consume and subsequently disperse viable spores of arbuscular mycorrhizal fungi (AMF). Consequently, rodents may be important determinants of both AMF and tree community composition in neotropical forests. We examined the influence of both availability of other food resources and season on the consumption and subsequent dispersal of AMF spores by Proechimys semispinosus (the Central American spiny rat) from seven island populations located in Gatun Lake, Panama over a 13-month period. For each island population, we examined the relationship between monthly spore occurrence in fecal pellets and monthly density of trees and lianas producing ripe fruit. During the last 3 months of this study, five islands were provisioned with extra food, while two islands remained unmanipulated to test experimentally whether spiny rats consumed AMF only as an alternative resource when primary resources (fruit) were scarce. Consumption of AMF was highly seasonal, with spores being most common in fecal samples at the end of the rainy season and least common at the end of the dry season. Cross-correlation analysis and logistic regression analysis indicated that spore occurrence in feces varied synchronously among islands and was related positively to soil moisture and unrelated to natural fruit availability. After inoculation with AMF spores isolated from feces, AMF colonized roots of Paspalum notatum (bahia grass) grown in sterilized soil, and total dry weights of host plants increased, confirming the viability of AMF spores passed by spiny rats. The ubiquity of viable spores from several species of AMF occurring in feces of P. semispinosus implicates this rodent as an important AMF disperser. Furthermore, dispersal of AMF spores by spiny rats was not limited to ephemeral periods of primary resource scarcity, thus suggesting that P. semispinosus may influence tree seedling survival by making spores of their mutualistic fungi available throughout the

  19. Propagules of arbuscular mycorrhizal fungi in a secondary dry forest of Oaxaca, Mexico.

    PubMed

    Guadarrama, Patricia; Castillo-Argüero, Silvia; Ramos-Zapata, José A; Camargo-Ricalde, Sara L; Alvarez-Sánchez, Javier

    2008-03-01

    Plant cover loss due to changes in land use promotes a decrease in spore diversity of arbuscular mycorrhizal fungi (AMF), viable mycelium and, therefore, in AMF colonization, this has an influence in community diversity and, as a consequence, in its recovery. To evaluate different AMF propagules, nine plots in a tropical dry forest with secondary vegetation were selected: 0, 1, 7, 10, 14, 18, 22, 25, and 27 years after abandonment in Nizanda, Oaxaca, Mexico. The secondary vegetation with different stages of development is a consequence of slash and burn agriculture, and posterior abandonment. Soil samples (six per plot) were collected and percentage of AMF field colonization, extrarradical mycelium, viable spore density, infectivity and most probable number (MPN) ofAMF propagules were quantified through a bioassay. Means for field colonization ranged between 40% and 70%, mean of total mycelium length was 15.7 +/- 1.88 mg(-1) dry soil, with significant differences between plots; however, more than 40% of extracted mycelium was not viable, between 60 and 456 spores in 100 g of dry soil were recorded, but more than 64% showed some kind of damage. Infectivity values fluctuated between 20% and 50%, while MPN showed a mean value of 85.42 +/- 44.17 propagules (100 g dry soil). We conclude that secondary communities generated by elimination of vegetation with agricultural purposes in a dry forest in Nizanda do not show elimination of propagules, probably as a consequence of the low input agriculture practices in this area, which may encourage natural regeneration.

  20. 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.

  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. The rise and fall of arbuscular mycorrhizal fungal diversity during ecosystem retrogression.

    PubMed

    Krüger, Manuela; Teste, François P; Laliberté, Etienne; Lambers, Hans; Coghlan, Megan; Zemunik, Graham; Bunce, Michael

    2015-10-01

    Ecosystem retrogression following long-term pedogenesis is attributed to phosphorus (P) limitation of primary productivity. Arbuscular mycorrhizal fungi (AMF) enhance P acquisition for most terrestrial plants, but it has been suggested that this strategy becomes less effective in strongly weathered soils with extremely low P availability. Using next generation sequencing of the large subunit ribosomal RNA gene in roots and soil, we compared the composition and diversity of AMF communities in three contrasting stages of a retrogressive >2-million-year dune chronosequence in a global biodiversity hotspot. This chronosequence shows a ~60-fold decline in total soil P concentration, with the oldest stage representing some of the most severely P-impoverished soils found in any terrestrial ecosystem. The richness of AMF operational taxonomic units was low on young (1000's of years), moderately P-rich soils, greatest on relatively old (~120 000 years) low-P soils, and low again on the oldest (>2 000 000 years) soils that were lowest in P availability. A similar decline in AMF phylogenetic diversity on the oldest soils occurred, despite invariant host plant diversity and only small declines in host cover along the chronosequence. Differences in AMF community composition were greatest between the youngest and the two oldest soils, and this was best explained by differences in soil P concentrations. Our results point to a threshold in soil P availability during ecosystem regression below which AMF diversity declines, suggesting environmental filtering of AMF insufficiently adapted to extremely low P availability. © 2015 John Wiley & Sons Ltd.

  3. 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

  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. 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.

  6. Communities of arbuscular mycorrhizal fungi in arable soils are not necessarily low in diversity.

    PubMed

    Hijri, Isabelle; Sýkorová, Zuzana; Oehl, Fritz; Ineichen, Kurt; Mäder, Paul; Wiemken, Andres; Redecker, Dirk

    2006-07-01

    Communities of arbuscular mycorrhizal fungi (AMF) in five agricultural field sites of different management intensities were studied. Variable regions of the ribosomal RNA genes were used to detect and identify AMF directly within colonized roots. Roots from a continuous maize monoculture showed low AMF diversity, in agreement with previous reports on molecular diversity of AMF in agricultural soils. In contrast, a substantially higher diversity of AMF was found throughout the long term 'DOK' field experiment, where organic and conventional agricultural practices have been compared side by side since 1978. In this experiment, a 7-year crop rotation is performed under lower levels of inorganic fertilizer input and chemical pest control. These results are in good agreement with analyses of the spore community previously conducted in these field sites. In a third site, an organically managed leek field with soil of very high phosphate content reflecting the highly intensive conventional field history and intensive tillage, we detected a low-diversity community comparable to the maize monoculture. In addition to fungi from Glomus group A, which have previously been reported to dominate arable soils, we regularly found members of the genera Scutellospora, Paraglomus and Acaulospora. The genus Acaulospora was shown to occur more frequently early in the growing season, suggesting that the life history strategy of AMF may influence the active community at a given time. These data show that the diversity of AMF is not always low in arable soils. Furthermore, low-input agriculture involving crop rotation may provide better conditions to preserve AMF diversity, by preventing the selection for the few AMF taxa tolerating high nutrient levels.

  7. GintAMT3 - a Low-Affinity Ammonium Transporter of the Arbuscular Mycorrhizal Rhizophagus irregularis.

    PubMed

    Calabrese, Silvia; Pérez-Tienda, Jacob; Ellerbeck, Matthias; Arnould, Christine; Chatagnier, Odile; Boller, Thomas; Schüßler, Arthur; Brachmann, Andreas; Wipf, Daniel; Ferrol, Nuria; Courty, Pierre-Emmanuel

    2016-01-01

    Nutrient acquisition and transfer are essential steps in the arbuscular mycorrhizal (AM) symbiosis, which is formed by the majority of land plants. Mineral nutrients are taken up by AM fungi from the soil and transferred to the plant partner. Within the cortical plant root cells the fungal hyphae form tree-like structures (arbuscules) where the nutrients are released to the plant-fungal interface, i.e., to the periarbuscular space, before being taken up by the plant. In exchange, the AM fungi receive carbohydrates from the plant host. Besides the well-studied uptake of phosphorus (P), the uptake and transfer of nitrogen (N) plays a crucial role in this mutualistic interaction. In the AM fungus Rhizophagus irregularis (formerly called Glomus intraradices), two ammonium transporters (AMT) were previously described, namely GintAMT1 and GintAMT2. Here, we report the identification and characterization of a newly identified R. irregularis AMT, GintAMT3. Phylogenetic analyses revealed high sequence similarity to previously identified AM fungal AMTs and a clear separation from other fungal AMTs. Topological analysis indicated GintAMT3 to be a membrane bound pore forming protein, and GFP tagging showed it to be highly expressed in the intraradical mycelium of a fully established AM symbiosis. Expression of GintAMT3 in yeast successfully complemented the yeast AMT triple deletion mutant (MATa ura3 mep1Δ mep2Δ::LEU2 mep3Δ::KanMX2). GintAMT3 is characterized as a low affinity transport system with an apparent Km of 1.8 mM and a V max of 240 nmol(-1) min(-1) 10(8) cells(-1), which is regulated by substrate concentration and carbon supply.

  8. 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.

  9. Intraisolate Mitochondrial Genetic Polymorphism and Gene Variants Coexpression in Arbuscular Mycorrhizal Fungi

    PubMed Central

    Beaudet, Denis; de la Providencia, Ivan Enrique; Labridy, Manuel; Roy-Bolduc, Alice; Daubois, Laurence; Hijri, Mohamed

    2015-01-01

    Arbuscular mycorrhizal fungi (AMF) are multinucleated and coenocytic organisms, in which the extent of the intraisolate nuclear genetic variation has been a source of debate. Conversely, their mitochondrial genomes (mtDNAs) have appeared to be homogeneous within isolates in all next generation sequencing (NGS)-based studies. Although several lines of evidence have challenged mtDNA homogeneity in AMF, extensive survey to investigate intraisolate allelic diversity has not previously been undertaken. In this study, we used a conventional polymerase chain reaction -based approach on selected mitochondrial regions with a high-fidelity DNA polymerase, followed by cloning and Sanger sequencing. Two isolates of Rhizophagus irregularis were used, one cultivated in vitro for several generations (DAOM-197198) and the other recently isolated from the field (DAOM-242422). At different loci in both isolates, we found intraisolate allelic variation within the mtDNA and in a single copy nuclear marker, which highlighted the presence of several nonsynonymous mutations in protein coding genes. We confirmed that some of this variation persisted in the transcriptome, giving rise to at least four distinct nad4 transcripts in DAOM-197198. We also detected the presence of numerous mitochondrial DNA copies within nuclear genomes (numts), providing insights to understand this important evolutionary process in AMF. Our study reveals that genetic variation in Glomeromycota is higher than what had been previously assumed and also suggests that it could have been grossly underestimated in most NGS-based AMF studies, both in mitochondrial and nuclear genomes, due to the presence of low-level mutations. PMID:25527836

  10. 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 pa