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Arbuscular mycorrhizal (AM) symbiosis plays an important role in ecosystem functioning, particularly in fragile environments. Little is known, however, about how AM fungus community composition responds to slope aspect. Our objective was to compare the AM fungus communities between sunny and shady slopes and to detect factors that influenced the distributions of AM fungi in arid ecosystems of the Daqingshan Mountains, Inner Mongolia, North China. AM fungus communities were evaluated based on small subunit ribosomal RNA genes (SSUs) using Illumina MiSeq sequencing. AM fungus community composition differed significantly between slope aspects, and sunny slopes had significantly higher AM fungus diversity and richness as well as spore density, total root colonization, arbuscule abundance, vesicle abundance, and hyphal colonization than shady slopes. Structural equation modeling (SEM) illustrated that the effects of slope aspect on AM fungus richness likely were mediated by available phosphorus, soil organic carbon, plant cover, and plant diversity. Available phosphorus was the principal factor that influenced AM fungus species richness, and soil organic carbon was the principal factor influencing spore density and total root colonization, suggesting that these factors especially might be responsible for differences between the AM fungus communities of different slope aspects. These findings elucidate the influence of slope aspect on AM fungus communities and may inform use of AM fungi in protection and restoration of vegetation with different slope aspects in arid ecosystems.

In epiphytic orchids, distinctive groups of fungi are involved in the symbiotic association. However, little is known about the factors that determine the mycorrhizal community structure. Here, we analyzed the orchid mycorrhizal fungi communities associated with three sympatric Cymbidieae epiphytic tropical orchids (Cyrtochilum flexuosum, Cyrtochilum myanthum, and Maxillaria calantha) at two sites located within the mountain rainforest of southern Ecuador. To characterize these communities at each orchid population, the ITS2 region was analyzed by Illumina MiSeq technology. Fifty-five mycorrhizal fungi operational taxonomic units (OTUs) putatively attributed to members of Serendipitaceae, Ceratobasidiaceae and Tulasnellaceae were identified. Significant differences in mycorrhizal communities were detected between the three sympatric orchid species as well as among sites/populations. Interestingly, some mycorrhizal OTUs overlapped among orchid populations. Our results suggested that populations of studied epiphytic orchids have site-adjusted mycorrhizal communities structured around keystone fungal species. Interaction with multiple mycorrhizal fungi could favor orchid site occurrence and co-existence among several orchid species.

The order Endogonales in Mucoromycotina, an early divergent lineage of fungi, includes ectomycorrhizal (EM) fungi. This order is therefore considered a key taxon for elucidation of the evolution of EM associations. Recent studies have revealed high diversity of EM lineages of Basidiomycota and Ascomycota; however, EM associations of Endogonales and its relatives remain largely unknown. In this study, EM root tips with a unique fungal sheath, with aseptate and highly branched hyphae of variable widths, were identified in Quercus acutissima and Quercus crispula forests in the temperate zone of Japan. The mycobionts were confirmed as Endogone sp., which were placed as a sister clade of Endogone pisiformis, based on phylogenetic analyses of the small and large subunits of the nuclear ribosomal RNA and elongation factor-1α genes. This is the first report of EM of Endogone in natural forests of the Northern Hemisphere and the first finding on Quercus.

The Alpine porcini, Boletus reticuloceps, is an ectomycorrhizal mushroom distributed in subalpine areas of Southwest China, central China, and Taiwan Island. This distribution pattern makes it an ideal organism to infer how ectomycorrhizal fungi have reacted to historical tectonic and climatic changes, and to illustrate the mechanism for the disjunction of organisms between Southwest China and Taiwan. In this study, we explored the phylogeographic pattern of B. reticuloceps by microsatellite genotyping, DNA sequencing, ecological factor analysis, and species distribution modeling. Three genetic groups from the East Himalayas (EH), northern Hengduan Mountains (NHM), and southern Hengduan Mountains (SHM), were identified. The earlier divergent SHM group is found under Abies in moister environments, whereas the EH and NHM groups, which are physically separated by the Mekong-Salween Divide, are found mainly under Picea in drier environments. Samples from Taiwan showed a close relationship with the SHM group. High mountains did not form dispersal barriers among populations in each of the EH, NHM, and SHM groups, probably due to the relatively weak host specificity of B. reticuloceps. Our study indicated that ecological heterogeneity could have contributed to the divergence between the SHM and the NHM-EH groups, while physical barriers could have led to the divergence of the NHM and the EH groups. Dispersal into Taiwan via Central China during the Quaternary glaciations is likely to have shaped its disjunct distribution.

Little is known about Orchidaceae plants in Chile and their mycorrhizal associations, a key issue for designing protective actions for endangered species. We investigated root fungi from seven terrestrial orchid species to identify potential mycorrhizal fungi. The main characteristics of Rhizoctonia-like fungi were observed under light microscopy, and isolates were identified through PCR-ITS sequencing. Molecular identification of fungal sequences showed a high diversity of fungi colonizing roots. Fungal ability to germinate seeds of different orchids was determined in symbiotic germination tests; 24 fungal groups were isolated, belonging to the genera Tulasnella, Ceratobasidium, and Thanatephorus. Furthermore, dark septate and other endophytic fungi were identified. The high number of Rhizoctonia-like fungi obtained from adult orchids from the Coastal mountain range suggests that, after germination, these orchids may complement their nutritional demands through mycoheterotrophy. Nonetheless, beneficial associations with other endophytic fungi may also co-exist. In this study, isolated mycorrhizal fungi had the ability to induce seed germination at different efficiencies and with low specificity. Germin ation rates were low, but protocorms continued to develop for 60 days. A Tulasnella sp. isolated from Chloraea gavilu was most effective to induce seed germination of different species. The dark septate endophytic (DSE) fungi did not show any effect on seed development; however, their widespread occurrence in some orchids suggests a putative role in plant establishment.

After stand-replacing disturbance, regenerating conifer seedlings become colonized by different ectomycorrhizal fungi (EMF) than the locally adapted EMF communities present on seedlings in mature forests. We studied whether EMF species that colonized subalpine fir (Abies lasiocarpa) seedlings in clearcuts differed from those that colonized seedlings in adjacent mature forests with respect to mycorrhizoplane extracellular enzyme activities (EEAs) and N status of the seedlings. We tested two alternate hypotheses: (1) that EEAs would differ between the two EMF communities, with higher activities associated with forest-origin communities, and (2) that acclimation to soil environment was considerable enough that EEAs would be determined primarily by the soil type in which the ectomycorrhizas were growing. Naturally colonized fir seedlings were reciprocally transplanted between clearcuts and forests, carrying different EMF communities with them. EEAs were influenced more by destination environment than by EMF community. EEAs were as high in early-successional as in late-successional communities in both destination environments. Buds of clearcut-origin seedlings had the same or higher N contents as forest seedlings after a growing season in either environment. These results indicate that (i) symbiotic EMF and/or their associated microbial communities demonstrate substantial ability to acclimate to new field environments; (ii) the ability to produce organic matter-degrading enzymes is not a trait that necessarily distinguishes early- and late-successional EMF communities in symbiosis; (iii) early-successional EMF are as capable of supporting seedling N accumulation in forest soils as late-successional EMF; and (iv) disturbed ecosystems where early-successional EMF are present should have high resilience for organic matter degradation.

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.

This study aims to determine the spatiotemporal dynamics of root colonization and spore density of arbuscular mycorrhizal fungi (AMF) in the rhizosphere of olive trees (Olea europaea) with different plantation ages and under different climatic areas in Algeria. Soil and root samples were seasonally collected from three olive plantations of different ages. Other samples were carried out in productive olive orchards cultivated under a climatic gradient (desertic, semi-arid, subhumid, and humid). The olive varieties analysed in this study were Blanquette, Rougette, Chemlel and the wild-olive. Spore density, mycorrhization intensity (M%), spore diversity and the most probable number (MPN) were determined. Both the intensity of mycorrhizal colonization and spore density increased with the increase of seasonal precipitation and decreased with the increase of air temperature regardless of the climatic region or olive variety. The variety Rougette had the highest mycorrhizal levels in all plantation ages and climates. Spore community was composed of the genera Rhizophagus, Funneliformis, Glomus, Septoglomus, Gigaspora, Scutellospora and Entrophospora. The genus Glomus, with four species, predominated in all climate regions. Spores of Gigaspora sp. and Scutellospora sp. were the most abundant in desertic plantations. Statistical models indicated a positive relationship between spore density and M% during spring and winter in young seedlings and old plantations. A significant positive relationship was found between MPN and spore density under different climates. For a mycotrophic species, the rhizosphere of olive trees proved to be poor in mycorrhiza in terms of mycorrhizal colonization and numbers of the infective AMF propagules., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Forestry reshapes ecosystems with respect to tree age structure, soil properties and vegetation composition. These changes are likely to be paralleled by shifts in microbial community composition with potential feedbacks on ecosystem functioning. Here, we assessed fungal communities across a chronosequence of managed Pinus sylvestris stands and investigated correlations between taxonomic composition and extracellular enzyme activities. Not surprisingly, clear-cutting had a negative effect on ectomycorrhizal fungal abundance and diversity. In contrast, clear-cutting favoured proliferation of saprotrophic fungi correlated with enzymes involved in holocellulose decomposition. During stand development, the re-establishing ectomycorrhizal fungal community shifted in composition from dominance by Atheliaceae in younger stands to Cortinarius and Russula species in older stands. Late successional ectomycorrhizal taxa correlated with enzymes involved in mobilisation of nutrients from organic matter, indicating intensified nutrient limitation. Our results suggest that maintenance of functional diversity in the ectomycorrhizal fungal community may sustain long-term forest production by retaining a capacity for symbiosis-driven recycling of organic nutrient pools.

Ectomycorrhizal (EM) fungal taxonomic, phylogenetic, and trait diversity (exploration types) were analyzed in beech and conifer forests along a north-to-south gradient in three biogeographic regions in Germany. The taxonomic community structures of the ectomycorrhizal assemblages in top soil were influenced by stand density and forest type, by biogeographic environmental factors (soil physical properties, temperature, and precipitation), and by nitrogen forms (amino acids, ammonium, and nitrate). While α-diversity did not differ between forest types, β-diversity increased, leading to higher γ-diversity on the landscape level when both forest types were present. The highest taxonomic diversity of EM was found in forests in cool, moist climate on clay and silty soils and the lowest in the forests in warm, dry climate on sandy soils. In the region with higher taxonomic diversity, phylogenetic clustering was found, but not trait clustering. In the warm region, trait clustering occurred despite neutral phylogenetic effects. These results suggest that different forest types and favorable environmental conditions in forests promote high EM species richness in top soil presumably with both high functional diversity and phylogenetic redundancy, while stressful environmental conditions lead to lower species richness and functional redundancy.

The success of dispersal events depend on the organism's ability to reach and establish in a new habitat. In symbiotic organisms, establishment also depends on the presence of their symbiont partner in the new habitat. For instance, the establishment of obligate ectomycorrhizal (EM) trees outside the forest is largely limited by the presence of EM fungi in soil. Wild boars (Sus scrofa) are important dispersal agents of EM fungal spores, particularly in the moderately dry Mediterranean region. The aim of this study was to explore how EM fungal spores dispersed by wild boars influence the EM fungal community associated with the roots of Pinus halepensis seedlings at different habitat types. Using a greenhouse bioassay, we grew pine seedlings in two soil types: old-field and forest soils mixed with either natural or autoclaved wild boar feces. In both soils, we observed a community dominated by a few EM fungal species. Geopora (85 %) and Suillus (68 %) species dominated the forest and old-field soils, respectively. The addition of natural wild boar feces increased the abundance of Tuber species in both EM fungal communities. However, this effect was more pronounced in pots with old-field soil, leading to a more even community, equally dominated by both Tuber and Suillus species. In forest soil, Geopora maintained dominance, but decreased in abundance (67 %), due to the addition of Tuber species. Our findings indicate that wild boar feces can be an important source for EM inoculum, especially in habitats poor in EM fungi such as old-fields.

Arbuscular mycorrhizal fungi (AMF) affect multiple ecosystem functions and processes, the assemblages of which vary across ecosystems. However, the influences of environmental factors on AMF communities which may shape these communities are still largely unknown. In this study, AMF communities from roots and rhizosphere soils of Chenopodium ambrosioides in different natural soils were investigated. The root habitat showed significantly smaller numbers of OTUs and lower community richness compared to the rhizosphere soil habitat. Most OTUs in the root habitat were shared by the soil habitat from the same sampling site, indicating that rhizosphere soils represent a pool of AMF species, a fraction of which is recruited by plants. Most of the AMF in root habitats were Glomeraceae, suggesting recruitment preferences of AMF by plants. The relative contributions of environmental factors to explain variations in AMF community composition and phylogenetic structure were assessed. The results revealed soil properties predominantly explained the variation, followed by geographic and climate parameters which explained a small fraction independently, while the host plant showed few explanations. Overall, our results indicated that soil and root habitats as well as soil characters, especially pH, nitrogen and micronutrients (Zn and Cu) affected AMF communities significantly.

Negative population feedbacks mediated by natural enemies can promote species coexistence at the community scale through disproportionate mortality of numerically dominant (common) tree species. Simultaneously, associations with arbuscular mycorrhizal fungi (AMF) can result in positive effects on tree populations. Coupling data on seedling foliar damage from herbivores and pathogens and DNA sequencing of soil AMF diversity, we assessed the effects of these factors on tree seedling mortality at local (1 m 2 ) and community (16 ha plot) scales in a tropical rainforest in Puerto Rico. At the local scale, AMF diversity in soil counteracted negative effects from foliar damage on seedling mortality. At the community scale, mortality of seedlings of common tree species increased with foliar damage while rare tree species benefited from soil AMF diversity. Together, the effects of foliar damage and soil AMF diversity on seedling mortality might foster tree species coexistence in this forest., (© 2016 by the Ecological Society of America.)

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.)

Fungal viruses (mycoviruses) are considered to be highly host specific, but phylogenetic analysis supports the occasional occurrence of horizontal transmission between species. We used an extensive sampling strategy to investigate whether similar viruses occur in more than one fungal species of the same forest habitat. Mycelial samples were collected from in-growth mesh bags (N = 259), fruiting bodies (N = 173) and cultured isolates (N = 68) at a forest site where the spatial distribution of viral infections in clonal individuals of the wood decay fungus Heterobasidion parviporum was mapped in detail earlier. The investigation revealed previously known Heterobasidion viruses in ∼2% of the single or pooled mycorrhizal samples from mesh bags, ∼3% of the fruiting body samples and none of the fungal cultures analyzed. Novel virus strains distinct from known Heterobasidion viruses were detected in cultures of ectomycorrhizal fungi (Lactarius tabidus, L. rufus) and saprotrophic fungi (Megacollybia platyphylla, Mucoraceae spp.). Overall, our results support the view that mycoviruses do not readily cross species borders. Regarding potential virocontrol applications, the introduction of Heterobasidion viruses into natural habitats is not expected to cause a major infection pressure towards the indigenous fungal community. However, the ecological consequences of the putative interspecies virus transmission events detected require further investigation., (© FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Some green orchids obtain carbon from their mycorrhizal fungi, as well as from photosynthesis. These partially mycoheterotrophic orchids sometimes produce fully achlorophyllous, leaf-bearing (albino) variants. Comparing green and albino individuals of these orchids will help to uncover the molecular mechanisms associated with mycoheterotrophy. We compared green and albino Epipactis helleborine by molecular barcoding of mycorrhizal fungi, nutrient sources based on 15 N and 13 C abundances and gene expression in their mycorrhizae by RNA-seq and cDNA de novo assembly. Molecular identification of mycorrhizal fungi showed that green and albino E. helleborine harboured similar mycobionts, mainly Wilcoxina. Stable isotope analyses indicated that albino E. helleborine plants were fully mycoheterotrophic, whereas green individuals were partially mycoheterotrophic. Gene expression analyses showed that genes involved in antioxidant metabolism were upregulated in the albino variants, which indicates that these plants experience greater oxidative stress than the green variants, possibly due to a more frequent lysis of intracellular pelotons. It was also found that some genes involved in the transport of some metabolites, including carbon sources from plant to fungus, are higher in albino than in green variants. This result may indicate a bidirectional carbon flow even in the mycoheterotrophic symbiosis. The genes related to mycorrhizal symbiosis in autotrophic orchids and arbuscular mycorrhizal plants were also upregulated in the albino variants, indicating the existence of common molecular mechanisms among the different mycorrhizal types., (© 2017 John Wiley & Sons Ltd.)

What factors determine the distribution of a species is a central question in ecology and conservation biology. In general, the distribution of plant species is assumed to be controlled by dispersal or environmentally controlled recruitment. For plant species which are critically dependent on mycorrhizal symbionts for germination and seedling establishment, specificity in mycorrhizal associations and availability of suitable mycorrhizal fungi can be expected to have a major impact on successful colonization and establishment and thus ultimately on a species distribution. We combined seed germination experiments with soil analyses and fungal assessments using 454 amplicon pyrosequencing to test the relative importance of dispersal limitation, mycorrhizal availability and local growth conditions on the distribution of the orchid species Liparis loeselii, which, despite being widely distributed, is rare and endangered in Europe. We compared local soil conditions, seed germination and mycorrhizal availability in the soil between locations in northern Belgium and France where L. loeselii occurs naturally and locations where conditions appear suitable, but where adults of the species are absent. Our results indicated that mycorrhizal communities associating with L. loeselii varied among sites and plant life cycle stages, but the observed variations did not affect seed germination, which occurred regardless of current L. loeselii presence and was significantly affected by soil moisture content. These results indicate that L. loeselii is a mycorrhizal generalist capable of opportunistically associating with a variety of fungal partners to induce seed germination. They also indicate that availability of fungal associates is not necessarily the determining factor driving the distribution of mycorrhizal plant species., (© 2017 John Wiley & Sons Ltd.)

Berardia subacaulis Vill. is a monospecific genus that is endemic to the South-western Alps, where it grows on alpine screes, which are extreme habitats characterized by soil disturbance and limiting growth conditions. Root colonization by arbuscular mycorrhizal fungi (AMF) is presumably of great importance in these environments, because of its positive effect on plant nutrition and stress tolerance, as well as on structuring the soil. However, there is currently a lack of information on this topic. In this paper, we tested which soil characteristics and biotic factors could contribute to determining the abundance and community composition of AMF in the roots of B. subacaulis, which had previously been found to be mycorrhizal. For such a reason, the influence of soil properties and environmental factors on AMF abundance and community composition in the roots of B. subacaulis, sampled on three different scree slopes, were analysed through microscopic and molecular analysis. The results have shown that the AMF community of Berardia roots was dominated by Glomeraceae, and included a core of AMF taxa, common to all three scree slopes. The vegetation coverage and dark septate endophytes were not related to the AMF colonization percentage and plant community did not influence the root AMF composition. The abundance of AMF in the roots was related to some chemical (available extractable calcium and potassium) and physical (cation exchange capacity, electrical conductivity and field capacity) properties of the soil, thus suggesting an effect of AMF on improving the soil quality. The non-metric multidimensional scaling (NMDS) ordination of the AMF community composition showed that the diversity of AMF in the various sites was influenced not only by the soil quality, but also by the slope. Therefore, the slope-induced physical disturbance of alpine screes may contribute to the selection of disturbance-tolerant AMF taxa, which in turn may lead to different plant-fungus assemblages., Competing Interests: The authors have declared that no competing interests exist.

We introduce an easy, fast and effective method to analyze the influence of genetically modified (GM) plants on soil and model organisms in the laboratory to substitute laborious and time consuming field trials. For the studies described here we focused on two GM plants of the so-called 3rd generation: GM plants producing pharmaceuticals (PMP) and plant made industrials (PMI). Cyanophycin synthetase (cphA) was chosen as model for PMI and Choleratoxin B (CTB) as model for PMP. The model genes are expressed in transgenic roots of composite Vicia hirsuta plants grown in petri dishes for semi-sterile growth or small containers filled with non-sterile soil. No significant influence of the model gene expression on root induction, growth, biomass, interaction with symbionts such as rhizobia (number, size and functionality of nodules, selection of nodulating strains) or arbuscular mycorrhizal fungi could be detected. In vitro, but not in situ under field conditions, structural diversity of the bulk soil microbial community between transgenic and non-transgenic cultivars was determined by PLFA pattern-derived ratios of bacteria: fungi and of gram + : gram - bacteria. Significant differences in PLFA ratios were associated with dissimilarities in the quantity and molecular composition of rhizodeposits as revealed by Py-FIMS analyses. Contrary to field trials, where small effects based on the transgene expression might be hidden by the immense influence of various environmental factors, our in vitro system can detect even minor effects and correlates them to transgene expression with less space, time and labour., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Soil fungal community and dominant mycorrhizal types are known to shift along with plant community changes during primary succession. However, it is not well understood how and why root fungal symbionts and colonization types vary within the plant host when the host species is able to thrive both at young and at old successional stages with different light and nutrient resource availability. We asked (i) how root fungal colonization of Deschampsia flexuosa (Poaceae) by arbuscular mycorrhizal (AM) fungi and dark septate endophytes (DSE) changes along a postglacial primary successional land uplift gradient. As neighboring vegetation may play a role in root fungal colonization, we also asked (ii) whether removal of the dominant neighbor, Empetrum nigrum ssp. hermaphroditum (Ericaceae), affects root fungal colonization of Deschampsia. We also studied whether (iii) foliar carbon (C) and nitrogen (N) concentration of Deschampsia is related to successional changes along a land uplift gradient. AM colonization decreased (-50 %), DSE colonization increased (+200 %), and foliar C declined in Deschampsia along with increasing successional age, whereas foliar N was not affected. Empetrum removal did not affect AM colonization but increased DSE sclerotial colonization especially at older successional stages. The observed decrease in foliar C coincides with an increase in canopy closure along with increasing successional age. We suggest that the shift from an AM-dominated to a DSE-dominated root fungal community in Deschampsia along a land uplift successional gradient may be related to different nutritional benefits gained through these root fungal groups.

Terrestrial orchids depend on orchid mycorrhizal fungi (OMF) as symbionts for their survival, growth and nutrition. The ability of OMF from endangered orchid species to compete for available resources with OMF from common species may affect the distribution, abundance and therefore conservation status of their orchid hosts. Eight symbiotically effective OMF from endangered and more common Caladenia species were tested for their ability to utilise complex insoluble and simple soluble carbon sources produced during litter degradation by growth with different carbon sources in liquid medium to measure the degree of OMF variation with host conservation status or taxonomy. On simple carbon sources, fungal growth was assessed by biomass. On insoluble substrates, ergosterol content was assessed using ultra-performance liquid chromatography (UPLC). The OMF grew on all natural materials and complex carbon sources, but produced the greatest biomass on xylan and starch and the least on bark and chitin. On simple carbon sources, the greatest OMF biomass was measured on most hexoses and disaccharides and the least on galactose and arabinose. Only some OMF used sucrose, the most common sugar in green plants, with possible implications for symbiosis. OMF from common orchids produced more ergosterol and biomass than those from endangered orchids in the Dilatata and Reticulata groups but not in the Patersonii and Finger orchids. This suggests that differences in carbon source utilisation may contribute to differences in the distribution of some orchids, if these differences are retained on site.

Pesticide contamination of the environment can result from agricultural practices. Persistence of pesticide residues is a threat to the soil biota including plant roots and beneficial microorganisms, which support an important number of soil ecosystem services. Arbuscular mycorrhizal fungi (AMF) are key symbiotic microorganisms contributing to plant nutrition. In the present study, we assessed whether AMF could indicate eventual side effects of pesticides when directly applied to field soils. We evaluated the ecotoxicological impact of a cocktail of three commonly used agricultural pesticides (fenhexamid, folpel, deltamethrin) on the abundance and composition of the AMF community in vineyard (Montagne de Saint-Emilion) and arable (Martincourt) soils subjected to different agricultural practices. The dissipation of applied pesticides was monitored by multiresidual analyses to determine the scenario of exposure of the AMF community. Diversity analysis before application of the pesticide cocktail showed that the AMF communities of vineyard soils, subjected to mechanical weeding or grass cover, and of the arable soil subjected to intensive agriculture, were dominated by Glomerales. Ribotypes specific to each soil and to each agricultural practice in the same soil were found, with the highest abundance and diversity of AMF being observed in the vineyard soil with a grass-cover. The abundance of the global AMF community (Glomeromycota) and of three taxa of AMF (Funneliformis mosseae, Claroideoglomus etunicatum/C. claroideum) was evaluated after pesticide application. The abundance of Glomeromycota decreased in both soils after pesticide application while the abundance of Claroideoglomus and F. mosseae decreased only in the arable soil. These results show that higher doses of pesticide exposure did not affect the global abundance, but altered the composition, of the AMF community. Resilience of the AMF community composition was observed only in the vineyard soil, where F. mosseae was the most tolerant taxon to pesticide exposure., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Amanita is a worldwide-distributed fungal genus, with approximately 600 known species. Most species within the genus are ectomycorrhizal (ECM), with some saprotrophic representatives. In this study, we constructed the first comprehensive phylogeny including ECM species from Colombia collected in native Quercus humboldtii forests and in introduced Pinus patula plantations. We included 8 species (A. brunneolocularis, A. colombiana, A. flavoconia, A. fuligineodisca, A. muscaria, A. rubescens, A. sororcula, and A. xylinivolva) out of 16 species reported for the country, two new reports: A. citrina and A. virosa, and a new variety A. brunneolocularis var. pallida. Morphological taxonomic keys together with a phylogenetic approach using three nuclear gene regions: partial nuc rDNA 28S nuc rDNA internal transcribed spacers ITS1 and ITS2 and partial translation elongation factor 1-α gene (TEF1), were used to classify the specimens. Several highly supported clades were obtained from the phylogenetic hypotheses obtained by Bayesian inference and maximum likelihood approaches, allowing us to position the Colombian collections in a coherent infrageneric level and to contribute to the knowledge of local Amanita diversity.

Premise of the Study: Symbioses are almost universal, but little is known about how symbiont abundance can affect host performance. Many orchids undergo vegetative dormancy and frequent and protracted dormancy have been associated with population declines. If mycorrhizal fungi affect host plant performance, those effects are likely to alter patterns of vegetative dormancy. The goal of this study was to determine whether the abundance of mycorrhizal fungi is related to the likelihood of entering dormancy and whether fungal abundance varied with dormancy duration in the federally listed threatened orchid Isotria medeoloides., Methods: We studied three populations of the threatened North American terrestrial orchid Isotria medeoloides using long-term emergence data and evaluated the relationship between the abundance of associated mycorrhizal fungi (Russulaceae) and orchid dormancy and emergence. Mycorrhizal fungi in soil adjacent to orchids were quantified in two ways. First, ectomycorrhizal (ECM) fungi on adjacent root tips were identified using DNA sequencing to determine their phylogenetic relationship to fungi that are known to form mycorrhizae with I. medeoloides. Second, we extracted DNA from soil samples and used quantitative real-time PCR to estimate the abundance of Russulaceae hyphae adjacent to each orchid., Key Results: We found that the abundance of Russulaceae, both in the soil and on nearby ECM root tips, was significantly related to orchid prior emergence. Both abundance and prior emergence history were predictive of future emergence., Conclusions: These results suggest that the abundance of mycorrhizal fungi can influence orchid population dynamics and is an essential component of orchid conservation., (© 2017 Botanical Society of America.)

Human activity has more than doubled the amount of nitrogen entering the global nitrogen cycle, and the boreal forest biome is a nitrogen-limited ecosystem sensitive to nitrogen load perturbation. Although bryophyte-associated microbes contribute significantly to boreal forest ecosystem function, particularly in carbon and nitrogen cycling, little is known about their responses to anthropogenic global change. Amplicon pyrosequencing of the ITS2 region of rDNA was used to investigate how fungal communities associated with three bryophyte species responded to increased nitrogen loads in a long-term fertilization experiment in a boreal Picea abies forest in southern Norway. Overall, OTU richness, community composition and the relative abundance of specific ecological guilds were primarily influenced by host species identity and tissue type. Although not the primary factor affecting fungal communities, nitrogen addition did impact the abundance of specific guilds of fungi and the resulting overall community composition. Increased nitrogen loads decreased ectomycorrhizal abundance, with Amphinema, Cortinarius, Russula and Tylospora OTUs responding negatively to fertilization. Pathogen abundance increased with fertilization, particularly in the moss pathogen Eocronartium. Saprophytic fungi were both positively and negatively impacted by the nitrogen addition, indicating a complex community level response. The overshadowing of the effects of increased nitrogen loads by variation related to host and tissue type highlights the complexity of bryophyte-associated microbial communities and the intricate nature of their responses to anthropogenic global change., (© 2016 John Wiley & Sons Ltd.)

The study is aimed to estimate the diversity of arbuscular mycorrhizal fungi (AMF) in the main producing areas of Salvia miltiorrhiza.Diversity of AMF was surveyed directly on spores isolated from the field soil, collected from 20 sites of 8 provinces. Identification of the AMF was made by observation of spore morphology. At least 27 recognized AMF species were identified in samples from field soil, belonging to seven genera of AMF-Acaulospora, Glomus, Funneliformis, Ambispora, Rhizophagus, Pacispora, and Claroideoglomus. Acaulospora and Glomus were the dominant genera, respectively including nine and eight species. A. laevis (90%), R.manihotis (80%), A. brieticulata (75%), A. tuberculata (70%) were the dominant species.Colonization rate was determined,colonization was easily found, but the colonization intensities were low, the colonization rate remained at 10.92%-25.93%. The similarity between provinces is generally low, and the similarity coefficients were from 0.20 to 0.57., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Chinese Pharmaceutical Association.)

Fungal diversity of Australian eucalypt forests remains underexplored. We investigated the ectomycorrhizal (EcM) fungal community characteristics of declining temperate eucalypt forests in Tasmania. Within this context, we explored the diversity of EcM fungi of two forest types in the northern highlands in the east and west of the island. We hypothesised that EcM fungal community richness and composition would differ between forest type but that the Cortinariaceae would be the dominant family irrespective of forest type. We proposed that EcM richness would be greater in the wet sclerophyll forest than the dry sclerophyll forest type. Using both sporocarps and EcM fungi from root tips amplified by PCR and sequenced in the rDNA ITS region, 175 EcM operational taxonomic units were identified of which 97 belonged to the Cortinariaceae. The Cortinariaceae were the most diverse family, in both the above and below ground communities. Three distinct fungal assemblages occurred within the wet and dry sclerophyll forest types and two geographic regions that were studied, although this pattern did not remain when only the root tip data were analysed. EcM sporocarp richness was unusually higher than root tip richness and EcM richness did not significantly differ among forest types. The results are discussed in relation to the importance of the Cortinariaceae and the drivers of EcM fungal community composition within these forests.

Abies religiosa is an endemic conifer of Mexico, where its monodominant forests are the winter refuge of the monarch butterfly. Due to climate change, it has been estimated that by 2090, A. religiosa populations will decline by 96.5 %. To achieve success, reforestation programs should consider its ectomycorrhizal (ECM) fungi. We used ITS nrDNA sequences to identify the ECM fungi associated with A. religiosa and, based on its abundance and frequency, determined the diversity and community structure in a pure A. religiosa forest near Mexico City. Using sequence metadata, we inferred the species geographic distribution and host preferences. We conducted phylogenetic analyses of the Clavulinaceae (the most important family). The ECM community held 83 species, among which the richest genera were Inocybe (21 species), Tomentella (10 species), and Russula (8 species). Besides its low species richness, the Clavulina-Membranomyces lineage was the most dominant family. Clavulina cf. cinerea and Membranomyces sp. exhibited the highest relative abundance and relative frequency values. Phylogenetic analyses placed the Clavulinaceae genotypes in three different clades: one within Membranomyces and two within Clavulina. A meta-analysis showed that the majority of the ECM fungi (45.78 %) associated with A. religiosa in Mexico have also been sequenced from North America and are shared by Pinaceae and Fagaceae. In contrast, because they have not been sequenced previously, 32.2 % of the species have a restricted distribution. Here, we highlight the emerging pattern that the Clavulina-Membranomyces lineage is dominant in several ECM communities in the Neotropics, including Aldinia and Dicymbe legume tropical forests in the Guyana Shield, the Alnus acuminata subtropical communities, and the A. religiosa temperate forests in Mexico.

Rhizopogon species are ecologically significant ectomycorrhizal fungi in conifer ecosystems. The importance of this system merits the development and utilization of a more robust set of molecular markers specifically designed to evaluate their evolutionary ecology. Anonymous nuclear loci (ANL) were developed for R. subgenus Amylopogon. Members of this subgenus occur throughout the United States and are exclusive fungal symbionts associated with Pterospora andromedea, a threatened mycoheterotrophic plant endemic to disjunct eastern and western regions of North America. Candidate ANL were developed from 454 shotgun pyrosequencing and assessed for positive amplification across targeted species, sequencing success, and recovery of phylogenetically informative sites. Ten ANL were successfully developed and were subsequently used to sequence representative taxa, herbaria holotype and paratype specimens in R. subgenus Amylopogon. Phylogenetic reconstructions were performed on individual and concatenated data sets by Bayesian inference and maximum likelihood methods. Phylogenetic analyses of these 10 ANL were compared with a phylogeny traditionally constructed using the universal fungal barcode nuc rDNA ITS1-5.8S-ITS2 region (ITS). The resulting ANL phylogeny was consistent with most of the species designations delineated by ITS. However, the ANL phylogeny provided much greater phylogenetic resolution, yielding new evidence for cryptic species within previously defined species of R. subgenus Amylopogon. Additionally, the rooted ANL phylogeny provided an alternate topology to the ITS phylogeny, which inferred a novel set of evolutionary relationships not identified in prior phylogenetic studies.

Land-use change is known to be a major threat to biodiversity and ecosystem services in Mediterranean areas. However, the potential for different host plants to modulate the effect of land-use intensification on community composition of arbuscular mycorrhizal fungi (AMF) is still poorly understood. To test the hypothesis that low land-use intensity promotes AMF diversity at different taxonomic scales and to determine whether any response is dependent upon host plant species identity, we characterised AMF communities in the roots of 10 plant species across four land use types of differing intensity in a Mediterranean peatland system. AMF were identified using 454 pyrosequencing. This revealed an overall low level of AMF richness in the peaty soils; lowest AMF richness in the intense cropping system at both virtual taxa and family level; strong modulation by the host plant of the impact of land-use intensification on AMF communities at the virtual taxa level; and a significant effect of land-use intensification on AMF communities at the family level. These findings have implications for understanding ecosystem stability and productivity and should be considered when developing soil-improvement strategies in fragile ecosystems, such as Mediterranean peatlands., (© FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

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.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous mutualists of terrestrial plants and play key roles in regulating various ecosystem processes, but little is known about AMF biogeography at regional scale. This study aims at exploring the key predictors of AMF communities across a 5000-km transect in northern China. We determined the soil AMF species richness and community composition at 47 sites representative of four vegetation types (meadow steppe, typical steppe, desert steppe and desert) and related them to plant community characteristics, abiotic factors and geographic distance. The results showed that soil pH was the strongest predictor of AMF richness and phylogenetic diversity. However, abiotic factors only have a low predictive effect on AMF community composition or phylogenetic patterns. By contrast, we found a significant relationship between community composition of AMF and plants, which was a surprising result given the extent of heterogeneity in the plant community across this transect. Moreover, the geographic distance predominantly explained the AMF phylogenetic structure, implying that history evolutionary may play a role in shaping AMF biogeographic patterns. This study highlighted the different roles of main factors in predicting AMF biogeography, and bridge landscape-scale studies to more recent global-scale efforts., (© 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.)

A new genus and three new species of Agaricales are described from the Pakaraima Mountains of Guyana in the central Guiana Shield. All three of these new species fruit on the ground in association with species of the ectomycorrhizal (ECM) tree genus Dicymbe (Fabaceae subfam. Caesalpinioideae) and one species has been shown to form ectomycorrhizas. Multi-locus molecular phylogenetic analyses place Guyanagarika gen. nov. within the Catathelasma clade, a lineage in the suborder Tricholomatineae of the Agaricales. We formally recognize this 'Catathelasma clade' as an expanded family Catathelasmataceae that includes the genera Callistosporium, Catathelasma, Guyanagarika, Macrocybe, Pleurocollybia, and Pseudolaccaria. Within the Catathelasmataceae, Catathelasma and Guyanagarika represent independent origins of the ectomycorrhizal habit. Guyanagarika is the first documented case of an ECM Agaricales genus known only from the Neotropics., (Copyright © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.)

Little is known about edaphic selection pressures as drivers of contrasting white spruce ectomycorrhizal fungal community structure and diversity in the Canadian boreal forest. We hypothesized that community composition differs among the four sites sampled-nursery, mining site, forest edge, and natural forest. Ectomycorrhizal (ECM) fungal community structure and diversity was studied at the four locations with soil fertility gradient through morpho-molecular and phylogenetic analyses in relationships with rhizospheric soil chemical properties. 41 different species were identified. Mining site had a significantly different species composition than the surrounding environments. Soil pH and percentage of roots colonized by ECM fungi increased while soil P, N, Fe, C, K, Mg, Al, Ca, and Na contents declined across the soil fertility gradient: nursery → natural forest → forest edge → mining site. Contrary to the preference of acid soils by ECM fungi, a few ecologically adapted to high pH, poor soil chemical fertility, and low organic matter content colonize white spruce roots on the non-acidogenic mining site, allowing natural regeneration of white spruce seedlings. Other ECM fungi are adapted to high fertigation level of commercial nursery. This study clearly shows the contrasting difference in white spruce ectomycorrhizal fungal community structure and diversity driven by edaphic selection pressures., Competing Interests: The authors have declared that no competing interests exist.

Bistorta vivipara is a widespread arctic-alpine ectomycorrhizal (ECM) plant species. Recent findings suggest that fungal communities associated with B. vivipara roots appear random over short distances, but at larger scales, environmental filtering structure fungal communities. Habitats in highly stressful environments where specialist species with narrower niches may have an advantage represent unique opportunity to test the effect of environmental filtering. We utilised high-throughput amplicon sequencing to identify ECM communities associated with B. vivipara in Svalbard. We compared ECM communities in a core habitat where B. vivipara is frequent (Dryas-heath) with edge habitats representing extremes in terms of nutrient availability where B. vivipara is less frequent (bird-manured meadow and a nutrient-depleted mine tilling). Our analysis revealed that soil conditions in edge habitats favour less diverse but more distinct ECM fungal communities with functional traits adapted to local conditions. ECM richness was overall lower in both edge habitats, and the taxonomic compositions of ECM fungi were in line with our functional expectations. Stress-tolerant genera such as Laccaria and Hebeloma were abundant in nutrient-poor mine site whereas functional competitors genera such as Lactarius and Russula were dominant in the nutrient-rich bird-cliff site. Our results suggest that ECM communities in rare edge habitats are most likely not subsets of the larger pool of ECM fungi found in natural tundra, and they may represent a significant contribution to the overall diversity of ECM fungi in the Arctic.

Fungal communities are important for carbon (C) transformations in boreal forests that are one of the largest C pools in terrestrial ecosystems, warranting thus further investigation of fungal community dynamics in time and space. We investigated fungal diversity and community composition seasonally and across defined soil horizons in boreal Scots pine forest in Finland using 454 pyrosequencing. We collected a total of 120 samples from five vertical soil horizons monthly from March to October; in March, under snow. Boreal forest soil generally harbored diverse fungal communities across soil horizons. The communities shifted drastically and rapidly over time. In late winter, saprotrophs dominated the community and were replaced by ectomycorrhizal fungi during the growing season. Our studies are among the first to dissect the spatial and temporal dynamics in boreal forest ecosystems and highlights the ecological importance of vertically distinct communities and their rapid seasonal dynamics. As climate change is predicted to result in warmer and longer snow-free winter seasons, as well as increase the rooting depth of trees in boreal forest, the seasonal and vertical distribution of fungal communities may change. These changes are likely to affect the organic matter decomposition by the soil-inhabiting fungi and thus alter organic C pools., (© FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Rubber tree (Hevea brasiliensis) is of major economic importance in Southeast Asia and for small land holders in Thailand in particular. Due to the high value of latex, plantations are expanding into unsuitable areas, such as the northeast province of Thailand where soil fertility is very low and therefore appropriate management practices are of primary importance. Arbuscular mycorrhizal fungi (AMF) contribute to plant growth through a range of mechanisms and could play a key role in a more sustainable management of the rubber plantations. We described the diversity of AMF associated with rubber tree roots in Northeast Thailand in relation to tree age and soil parameters along a chronosequence of rubber tree plantations. Cassava fields were included for comparison. Rubber tree and cassava roots harbored high diversity of AMF (111 Virtual Taxa, VT), including 20 novel VT. AMF VT richness per sample was consistently high (per site mean 16 to 21 VT per sample) along the chronosequence and was not related to soil properties. The composition of AMF communities differed between cassava and rubber tree plantations and was influenced by soil texture and nutrient content (sand, K, P, Ca). AMF community composition gradually shifted with the age of the trees. Our results suggest that the high diversity of AMF in this region is potentially significant for maintaining high functionality of AMF communities.

Mycorrhizal symbiosis often displays low specificity, except for mycoheterotrophic plants that obtain carbon from their mycorrhizal fungi and often have higher specificity to certain fungal taxa. Partially mycoheterotrophic (or mixotrophic, MX) plant species tend to have a larger diversity of fungal partners, e.g., in the genus Pyrola (Monotropoideae, Ericaceae). Preliminary evidence however showed that the Japanese Pyrola japonica has preference for russulacean fungi based on direct sequencing of the fungal internal transcribed spacer (ITS) region from a single site. The present study challenges this conclusion using (1) sampling of P. japonica in different Japanese regions and forest types and (2) fungal identification by ITS cloning. Plants were sampled from eight sites in three regions, in one of which the fungal community on tree ectomycorrhizal (ECM) tips surrounding P. japonica was also analyzed. In all, 1512 clone sequences were obtained successfully from 35 P. japonica plants and 137 sequences from ECM communities. These sequences were collectively divided into 74 molecular operational taxonomic units (MOTUs) (51 and 33 MOTUs, respectively). MOTUs from P. japonica involved 36 ECM taxa (96 % of all clones), and 17 of these were Russula spp. (76.2 % of all clones), which colonized 33 of the 35 sampled plants. The MOTU composition significantly differed between P. japonica and ECM tips, although shared species represented 26.3 % of the ECM tips community in abundance. This suggests that P. japonica has a preference for russulacean fungi.

Soil acidity is a major constraint on plant productivity. Arbuscular mycorrhizal (AM) fungi support plant colonization in acidic soil, but soil acidity also constrains fungal growth and diversity. Fungi in extreme environments generally evolve towards specialists, suggesting that AM fungi in acidic soil are acidic-soil specialists. In our previous surveys, however, some AM fungi detected in strongly acidic soils could also be detected in a soil with moderate pH, which raised a hypothesis that the fungi in acidic soils are pH generalists. To test the hypothesis, we conducted a pH-manipulation experiment and also analyzed AM fungal distribution along a pH gradient in the field using a synthesized dataset of the previous and recent surveys. Rhizosphere soils of the generalist plant Miscanthus sinensis were collected both from a neutral soil and an acidic soil, and M. sinensis seedlings were grown at three different pH. For the analysis of field communities, rhizosphere soils of M. sinensis were collected from six field sites across Japan, which covered a soil pH range of 3.0-7.4, and subjected to soil trap culture. AM fungal community compositions were determined based on LSU rDNA sequences. In the pH-manipulation experiment the acidification of medium had a significant impact on the compositions of the community from the neutral soil, but the neutralization of the medium had no effect on those of the community from the acidic soil. Furthermore, the communities in lower -pH soils were subsets of (nested in) those in higher-pH soils. In the field communities a significant nestedness pattern was observed along the pH gradient. These observations suggest that the fungi in strongly acidic soils are pH generalists that occur not only in acidic soil but also in wide ranges of soil pH. Nestedness in AM fungal community along pH gradients may have important implications for plant community resilience and early primary succession after disturbance in acidic soils., Competing Interests: The authors have declared that no competing interests exist.

While it is generally acknowledged that orchid species rely on mycorrhizal fungi for completion of their life cycle, little is yet known about how mycorrhizal fungal diversity and community composition vary within and between closely related orchid taxa. In this study, we used 454 amplicon pyrosequencing to investigate variation in mycorrhizal communities between pure (allopatric) and mixed (sympatric) populations of two closely related Platanthera species (Platanthera bifolia and P. chlorantha) and putative hybrids. Consistent with previous research, the two species primarily associated primarily with members of the Ceratobasidiaceae and, to a lesser extent, with members of the Sebacinales and Tulasnellaceae. In addition, a large number of ectomycorrhizal fungi belonging to various families were observed. Although a considerable number of mycorrhizal fungi were common to both species, the fungal communities were significantly different between the two species. Individuals with intermediate morphology showed communities similar to P. bifolia, confirming previous results based on the genetic architecture and fragrance composition that putative hybrids essentially belonged to one of the parental species (P. bifolia). Differences in mycorrhizal communities between species were smaller in mixed populations than between pure populations, suggesting that variation in mycorrhizal communities was largely controlled by local environmental conditions. The small differences in mycorrhizal communities in mixed populations suggests that mycorrhizal fungi are most likely not directly involved in maintaining species boundaries between the two Platanthera species. However, seed germination experiments are needed to unambiguously assess the contribution of mycorrhizal divergence to reproductive isolation., Competing Interests: The authors have declared that no competing interests exist.

Ectomycorrhizal (ECM) fungal communities covary with host plant communities along soil fertility gradients, yet it is unclear whether this reflects changes in host composition, fungal edaphic specialization or priority effects during fungal community establishment. We grew two co-occurring ECM plant species (to control for host identity) in soils collected along a 2-million-year chronosequence representing a strong soil fertility gradient and used soil manipulations to disentangle the effects of edaphic properties from those due to fungal inoculum. Ectomycorrhizal fungal community composition changed and richness declined with increasing soil age; these changes were linked to pedogenesis-driven shifts in edaphic properties, particularly pH and resin-exchangeable and organic phosphorus. However, when differences in inoculum potential or soil abiotic properties among soil ages were removed while host identity was held constant, differences in ECM fungal communities and richness among chronosequence stages disappeared. Our results show that ECM fungal communities strongly vary during long-term ecosystem development, even within the same hosts. However, these changes could not be attributed to short-term fungal edaphic specialization or differences in fungal inoculum (i.e. density and composition) alone. Rather, they must reflect longer-term ecosystem-level feedback between soil, vegetation and ECM fungi during pedogenesis., (© 2016 John Wiley & Sons Ltd.)

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

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.

Arbuscular mycorrhizal (AM) fungi are symbionts of most plants, increasing plant growth and diversity. The model AM fungus Rhizophagus irregularis (isolate DAOM 197198) exhibits low within-fungus polymorphism. In contrast, another study reported high within-fungus variability. Experiments with other R. irregularis isolates suggest that within-fungus genetic variation can affect the fungal phenotype and plant growth, highlighting the biological importance of such variation. We investigated whether there is evidence of differing levels of within-fungus polymorphism in an R. irregularis population. We genotyped 20 isolates using restriction site-associated DNA sequencing and developed novel approaches for characterizing polymorphism among haploid nuclei. All isolates exhibited higher within-isolate poly-allelic single-nucleotide polymorphism (SNP) densities than DAOM 197198 in repeated and non-repeated sites mapped to the reference genome. Poly-allelic SNPs were independently confirmed. Allele frequencies within isolates deviated from diploids or tetraploids, or that expected for a strict dikaryote. Phylogeny based on poly-allelic sites was robust and mirrored the standard phylogeny. This indicates that within-fungus genetic variation is maintained in AM fungal populations. Our results predict a heterokaryotic state in the population, considerable differences in copy number variation among isolates and divergence among the copies, or aneuploidy in some isolates. The variation may be a combination of all of these hypotheses. Within-isolate genetic variation in R. irregularis leads to large differences in plant growth. Therefore, characterizing genomic variation within AM fungal populations is of major ecological importance.

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.

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 parameters when considering the use of AMF as biocontrol agents.

This study aimed to isolate, identify, and characterise metal-tolerant fungi colonising poplar roots at a metal-contaminated phytoremediation site. Poplar roots were colonised by arbuscular mycorrhizal, ectomycorrhizal, and endophytic fungi, and the species were determined by ITS molecular analyses. Eight different isolates were successfully isolated into pure culture. Three isolates belonging to the Helotiales (P02, P06) and the Serendipita vermifera species (P04) were highly tolerant to metals (Cd, Zn, Pb, and Cu) compared to the mycorrhizal Hebeloma isolates. The three isolates degraded complex carbohydrates, such as xylan and cellulose, indicating that they could partially degrade root cell walls and penetrate into cells. This hypothesis was confirmed by further in vitro re-synthesis experiments, which showed that the three isolates colonised root tissues of poplar plantlets whereas two of them formed microsclerotia-like structures. Taken together, these results suggest an endophytic lifestyle of these isolates. This is the first evidence of S. vermifera as a root endophyte of poplar. A new endophytic putative species belonging to the Helotiales and closely related to Leohumicola is also reported. Interestingly, and when compared to mock-inoculated plants, both P06 and P04 isolates increased the number of root tips of inoculated poplar plantlets in vitro. Moreover, the S. vermifera P04 isolate also increased the shoot biomass. The results are discussed in relation to the potential use of endophytic strains for tree-based phytoremediation of metal-contaminated sites.

Changing climate is expected to alter precipitation patterns in the Arctic, with consequences for subsurface temperature and moisture conditions, community structure, and nutrient mobilization through microbial belowground processes. Here, we address the effect of increased snow depth on the variation in species richness and community structure of ectomycorrhizal (ECM) and saprotrophic fungi. Soil samples were collected weekly from mid-July to mid-September in both control and deep snow plots. Richness of ECM fungi was lower, while saprotrophic fungi was higher in increased snow depth plots relative to controls. [Correction added on 23 September 2016 after first online publication: In the preceding sentence, the richness of ECM and saprotrophic fungi were wrongly interchanged and have been fixed in this current version.] ECM fungal richness was related to soil NO 3 -N, NH 4 -N, and K; and saprotrophic fungi to NO 3 -N and pH. Small but significant changes in the composition of saprotrophic fungi could be attributed to snow treatment and sampling time, but not so for the ECM fungi. Delayed snow melt did not influence the temporal variation in fungal communities between the treatments. Results suggest that some fungal species are favored, while others are disfavored resulting in their local extinction due to long-term changes in snow amount. Shifts in species composition of fungal functional groups are likely to affect nutrient cycling, ecosystem respiration, and stored permafrost carbon., (© 2016 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

During a study comparing the ectomycorrhizal root communities in a native forest with those at the Arnold Arboretum in Massachusetts (USA), the European species Tuber borchii was detected on the roots of a native red oak in the arboretum over two successive years. Since T. borchii is an economically important edible truffle native to Europe, we conducted a search of other roots in the arboretum to determine the extent of colonization. We also wanted to determine whether other non-native Tuber species had been inadvertently introduced into this 140-year-old Arboretum because many trees were imported into the site with intact soil and roots prior to the 1921 USDA ban on these horticultural practices in the USA. While T. borchii was not found on other trees, seven other native and exotic Tuber species were detected. Among the North American Tuber species detected from ectomycorrhizae, we also collected ascomata of a previously unknown species described here as Tuber arnoldianum. This new species was found colonizing both native and non-native tree roots. Other ectomycorrhizal taxa that were detected included basidiomycetes in the genera Amanita, Russula, Tomentella, and ascomycetes belonging to Pachyphlodes, Helvella, Genea, and Trichophaea. We clarify the phylogenetic relationships of each of the Tuber species detected in this study, and we discuss their distribution on both native and non-native host trees.

While the arbuscular mycorrhizal (AM) symbiosis is known to be widespread in terrestrial ecosystems, there is growing evidence that aquatic plants also form the symbiosis. It has been suggested that symbiosis with AM fungi may represent an important adaptation for isoëtid plants growing on nutrient-poor sediments in oligotrophic lakes. In this study, we address AM fungal root colonization intensity, richness and community composition (based on small subunit (SSU) ribosomal RNA (rRNA) gene sequencing) in five populations of the isoëtid plant species Lobelia dortmanna inhabiting oligotrophic lakes in Southern Sweden. We found that the roots of L. dortmanna hosted rich AM fungal communities and about 15 % of the detected molecular taxa were previously unrecorded. AM fungal root colonization intensity and taxon richness varied along an environmental gradient, being higher in oligotrophic and lower in mesotrophic lakes. The overall phylogenetic structure of this aquatic fungal community differed from that described in terrestrial systems: The roots of L. dortmanna hosted more Archaeosporaceae and fewer Glomeraceae taxa than would be expected based on global data from terrestrial AM fungal communities.