Low Arbuscular Mycorrhizal Fungi Research Articles

Resilience of root and soil bacteria to drought stress depends on host plant's colonization affinity towards arbuscular mycorrhiza fungi

Water deficit is one of the most important climate events that has strong effect on agricultural ecosystem functionality comprising soil microbial communities and their functions. Arbuscular mycorrhizal fungi (AMF) are widely known for their roles in combating drought, including facilitation of drought-tolerant bacteria. However, differences in cultivar/variety affinity for mycorrhization have never been considered as influencing factors. In the present study, we evaluated the influence of mycorrhizal affinity of two durum wheat (T. turgidum subsp. Durum (Desf.)) varieties, Iride and Ramirez (high and low, respectively) on root and soil bacteriomes under well-watered and drought conditions. We used the 16S metagenomics approach (amplicon sequencing) to assess the bacterial communities of root and soil samples. The suppression effect of drought was evident across a wide range of bacterial taxa, including drought-tolerant taxa, especially in the non-inoculated plants. Nevertheless, the protective effect of AMF was also shown, especially in the Iride variety (high AMF colonization affinity) in both compartments (root and soil), as the relative abundance of drought-depleted taxa, such as Planctomycetes, Bacteroidetes and Verrucomicrobia, was either similar under well-watered and water deficit conditions or increased under water deficit conditions. Moreover, drought reduced the network complexity of root and soil bacteria, especially in Ramirez variety which has a lower AMF colonization affinity. Together, our results suggest that not only AMF colonization, but also host plant colonization affinity is one of the regulating factors in alleviating drought-induced changes in wheat plants by altering plant-fungal-bacterial interactions.

Characterization of the arbuscular mycorrhizal fungal community associated with rosewood in threatened Miombo forests.

Understanding the dynamics of arbuscular mycorrhizal fungi (AMF) in response to land use change is important for the restoration of degraded forests. Here, we investigated the AMF community composition in the roots of Pterocarpus tinctorius sampled from agricultural and forest fallow soils rich in aluminum and iron. By sequencing the large subunit region of the rRNA gene, we identified a total of 30 operational taxonomic units (OTUs) in 33 root samples. These OTUs belonged to the genera Rhizophagus, Dominikia, Glomus, Sclerocystis, and Scutellospora. The majority of these OTUs did not closely match any known AMF species. We found that AMF species richness was significantly influenced by soil properties and overall tree density. Acidic soils with high levels of aluminum and iron had a low mean AMF species richness of 3.2. Indicator species analyses revealed several AMF OTUs associated with base saturation (4 OTUs), high aluminum (3 OTUs), and iron (2 OTUs). OTUs positively correlated with acidity (1 OTU), iron, and available phosphorus (2 OTUs) were assigned to the genus Rhizophagus, suggesting their tolerance to aluminum and iron. The results highlight the potential of leguminous trees in tropical dry forests as a reservoir of unknown AMF species. The baseline data obtained in this study opens new avenues for future studies, including the use of indigenous AMF-based biofertilizers to implement ecological revegetation strategies and improve land use.

Contrasting mycorrhizal growth responses in native and invasive woody species are associated with distinct root trait syndromes

Abstract Invasive plant species often express resource‐acquisitive leaf traits that support rapid growth, but associated fine root traits and the role of microbial mutualists in invader whole‐plant functioning remain poorly understood. We performed an experiment of 12 phylogenetically grouped native and non‐native, invasive woody species, grown with or without a common inoculum of arbuscular mycorrhizal fungi (AMF) across two nutrient levels. We measured 10 fine root traits associated with nutrient uptake and suitability of AMF colonization. The presence of AMF increased the growth rate of all species, but native species were significantly more dependent on AMF than invaders. Furthermore, invaders expressed a distinct syndrome of first‐order root traits, including longer, thinner roots of high specific root length, greater branching intensity and lower tissue density, which are traits associated with rapid nutrient uptake and low AMF association. This syndrome was independent of phylogeny, AMF inoculation and soil fertility. An acquisitive fine root trait syndrome for invaders supports high photosynthetic and growth rates, linking above‐ and below‐ground functioning. The occurrence of this syndrome across phylogenetic groups indicates that lineages of woody invaders typically associated with arbuscular mycorrhizas may be generally less dependent on AMF than native species. Read the free Plain Language Summary for this article on the Journal blog.

Modeling geographic distribution of arbuscular mycorrhizal fungi from molecular evidence in soils of Argentinean Puna using a maximum entropy approach.

The biogeographic region of Argentinean Puna mainly extends at elevations higher than 3,000 m within the Andean Plateau and hosts diverse ecological communities highly adapted to extreme aridity and low temperatures. Soils of Puna are typically poorly evolved and geomorphology is shaped by drainage networks, resulting in highly vegetated endorheic basins and hypersaline basins known as salar or salt flats. Local communities rely on soil fertility for agricultural practices and on pastures for livestock rearing. From this perspective, investigating the scarcely explored microbiological diversity of these soils as indicators of ecosystems functioning might help to predict the fragility of these harsh environments. In this study we collected soil samples from 28 points, following a nested design within three different macro-habitats, i.e., Puna grassland, hypersaline salar and family-run crop fields. Total fungi and arbuscular mycorrhizal fungi (AMF) occurrence were analyzed using eDNA sequencing. In addition, the significance of soil salinity and organic matter content as significant predictors of AMF occurrence, was assessed through Generalized Linear Mixed Modeling. We also investigated whether intensive grazing by cattle and lama in Puna grasslands may reduce the presence of AMF in these highly disturbed soils, driving or not major ecological changes, but no consistent results were found, suggesting that more specific experiments and further investigations may address the question more specifically. Finally, to predict the suitability for AMF in the different macro-habitats, Species Distribution Modeling (SDM) was performed within an environmental coherent area comprising both the phytogeographic regions of Puna and Altoandino. We modeled AMF distribution with a maximum entropy approach, including bioclimatic and edaphic predictors and obtaining maps of environmental suitability for AMF within the predicted areas. To assess the impact of farming on AMF occurrence, we set a new series of models excluding the cultivated Chaupi Rodeo samples. Overall, SDM predicted a lower suitability for AMF in hypersaline salar areas, while grassland habitats and a wider temperature seasonality range appear to be factors significantly related to AMF enrichment, suggesting a main role of seasonal dynamics in shaping AMF communities. The highest abundance of AMF was observed in Vicia faba crop fields, while potato fields yielded a very low AMF occurrence. The models excluding the cultivated Chaupi Rodeo samples highlighted that if these cultivated areas had theoretically remained unmanaged habitats of Puna and Altoandino, then large-scale soil features and local bioclimatic constraints would likely support a lower suitability for AMF. Using SDM we evidenced the influence of bioclimatic, edaphic and anthropic predictors in shaping AMF occurrence and highlighted the relevance of considering human activities to accurately predict AMF distribution.

The root-associated arbuscular mycorrhizal fungal assemblages of exotic alien plants are simplified in invaded distribution ranges, but dominant species are retained: A trans-continental perspective.

Arbuscular mycorrhizal fungi (AMF) provide crucial support for the establishment of plants in novel environments. We hypothesized that the OTU/genus richness and diversity of soil- and root-associated AMF associated with alien plant species in their exotic ranges are lower than those in their native ranges. We examined the root-associated and soil-dwelling AMF of 11 invasive plant species in their native and exotic ranges in the United States and Europe by DNA sequencing of the ITS2 locus. Examined root-associated AMF assemblages were simplified, which manifested as the loss of several AMF genera in the exotic ranges of the plants. These fungal assemblages were also characterized by greater dominance and simplification of the fungal assemblages. The dominant fungal genera were present regardless of whether their host plants were in their native or exotic ranges. Interestingly, both the native and invaded soils hosted diverse local AMF assemblages. Therefore, alien plant invasions were not limited to soils with low AMF diversity. Some AMF taxa could be context-dependent passengers rather than drivers of alien plant invasions. Further studies should identify functions of AMF missing or less abundant in roots of plants growing in exotic ranges.

Mycorrhizal biofertilization improves grain yield and quality of hulless Barley (Hordeum vulgare ssp. nudum L.) under water stress conditions

Drought is one of the most important factors worldwide, which limits the crop production, especially in semi-arid areas. The use of beneficial microorganisms such as arbuscular mycorrhizal fungi (AMF) may represent an eco-friendly and biological technique to increase crops yields and ensure food security. The purpose of this paper was to evaluate the effect of AMF inoculation on a promised variety of hulless barley (Hordeum vulgare ssp. nudum L.) under three levels of water stress (well-watered, moderate drought and severe drought). Hulless barley plants were inoculated, or not, with autochthonous inoculum (AI) containing five native AMF species (Pacispora franciscana, Funneliformis mosseae, Funneliformis geosporum, Rhizophagus irregularis and Glomus tenebrosum), or commercial inoculum (CI) containing Glomus sp. strains. Under water stress, AMF inoculation especially, with autochthonous consortium has higher mycorrhizal root colonization of hulless barley by 7-fold and 23-fold in comparison to the non-inoculated controls, under moderate drought and severe drought conditions, respectively. Water stress decreased grain yield and thousand-kernel weight of hulless barley. The reduction was less pronounced in AMF inoculated plants compared to the non-inoculated control ones. Plants with higher mycorrhizal colonization showed higher grain yield and thousand-kernel weight by approximately 90% and 68.2% with AI, and by 106% and 83% with CI, respectively than control plants with lower AMF colonization, especially under severe drought. At the same time, the amount of K, Cu, Fe, Zn and Ca in hulless barley grain increased significantly in AMF inoculated plants with AI as well as with CI. Compared to the control plants, using autochthonous AMF species led to significantly decreased Na content in grain. Fatty acids in hulless barley grain decreased with the severity of water stress. Only under well-watered condition, AMF inoculation enhance C18:0 and C18:1 contents as compared to control plants. Moreover, total polyphenol and flavonoid increased due to AMF inoculation under both medium drought and severe drought conditions. The results obtained herein indicated that inoculation with AMF can enhance the water tolerance resulting in higher hulless barley grain yield and quality. Therefore, using AMF as biofertilizers may be important in regions suffering from lack of water in order to ensure sustainable agricultural systems.

Diverse and abundant arbuscular mycorrhizal fungi in ecological floating beds used to treat eutrophic water.

An increasing number of investigations have shown the universal existence of arbuscular mycorrhizal fungi (AMF) in aquatic ecosystems. However, little is known about the accurate distribution and function of AMF inhabiting aquatic ecosystems, especially ecological floating beds (EFBs), which are constructed for the remediation of polluted water bodies. In this study, we collected root samples of Canna generalis, Cyperus alternifolius, and Eichhornia crassipes from three EFBs on two eutrophic lakes in Wuhan, China. We aimed to investigate the resources and distribution of AMF in EFBs using Illumina Mi-seq technology. A total of 229 operational taxonomic units (OTUs) and 21 taxa from 348,799 Glomeromycota sequences were detected. Glomus and Acaulospora were the most dominant and second most dominant genera of AMF in the three EFBs, respectively. Different aquatic plant species showed varying degrees of AMF colonization (3.83-71%), diversity (6-103 OTUs, 3-15 virtual taxa), and abundance (14-57,551 sequences). Low AMF abundance, but relatively high AMF diversity, was found in C. alternifolius, which is usually considered non-mycorrhizal. This finding indicated the high accuracy of Illumina sequencing. Our results also revealed a lognormal species abundance distribution that was observed across AMF taxa in the three plant species. The AMF community composition was closely related to nitrogen and phosphorus contents. Overall, our data show that EFBs harbor diverse and abundant AMF communities. Additionally, the AMF community composition is closely related to the water quality of eutrophic lakes treated by the EFBs, indicating the potential application of AMF in plant-based bioremediation of wastewater. KEYPOINTS: • Aquatic plants in EFBs harbor diverse (229 OTUs) and abundant (348,799 sequences) AMF. • Different plant species host different taxa of AMF. Cyperaceae, originally considered non-mycorrhizal, may in fact be a variable mycorrhizal plant family. • The AMF community composition in EFBs is closely related to nutrient concentrations (nitrogen and phosphorus).

Plant neighbours shape fungal assemblages associated with plant roots: A new understanding of niche‐partitioning in plant communities

Abstract Understanding the assembly rules of mycorrhizal fungi is crucial, given their tremendous importance in plant nutrition and health. Differentiation in plant‐associated arbuscular mycorrhizal fungi (AMF) is likely driven by a host‐preference effect. Coexisting plant species may then affect a focal plant microbiota through fungal dispersal among plants, and plant preferential recruitment of AMF. Both mechanisms are likely shaped by the plant's phylogenetic and functional strategies. We expected that (a) the structure of AMF assemblages associated with a focal plant depends on the identity of the neighbouring plant species; (b) this effect would be predicted by the phylogenetic and functional similarity between the focal and neighbouring plant species. These predictions were tested during the first stages of growth, by simulating the early development of plants within a community Using an experimental matrix‐focal plant species design testing 15 neighbouring plants from five taxonomic families, we demonstrated that the neighbouring plants provided different species pools for the focal plant, Medicago truncatula, and influenced AMF communities associated with focal plant, especially in terms of richness but not relative evenness. Medicago truncatula grown with Brassicaceae or other Poaceae species displayed respectively no or low AMF richness compared to those grown with Rosaceae and Asteraceae species. These effects were weakly dependent on the phylogenetic distance from the neighbouring plant but were predicted by the functional proximity. AMF assemblages were enriched and bore more resemblance to the neighbouring plants when the neighbouring plants were functionally dissimilar from the focal one. Functional dissimilarity was only a significant predictor when based on traits characterizing the nutrient use and uptake strategy rather than on a more integrated growing strategy of the plant. Microbiota composition was shown to be dependent on the identity of the neighbouring plant, particularly on its functional below‐ground niche. At the colonization stage, when the plant arrives in a community, plant mycobiota might be influenced by the spatial distribution of plants already present in the community. This work suggests a new view of the concept of niche partitioning in space for plants based on microorganism–plant interactions. A free Plain Language Summary can be found within the Supporting Information of this article.

Species-specific trade-offs between regrowth and mycorrhizas in the face of defoliation and phosphorus addition

Arbuscular mycorrhizal fungi (AMF) enhance nutrient provision in exchange for carbon. However, a shift from nutrient to carbon limitation, induced by repeated or intense defoliation, can represent a trade-off between plant regrowth and the maintenance of mycorrhiza. The combined effects of AMF, phosphorus and defoliation on growth of A gropyron elongatum (C 3 grass, low mycorrhizal responsiveness) and B rachiaria brizantha (C 4 grass, high mycorrhizal responsiveness) were explored. Each species was subjected to a manipulative experiment with AMF inoculation (non-inoculated, inoculated), soluble P supply (low, high) and defoliation (non-defoliated, 60% defoliated). In A. elongatum , at low P supply, mycorrhizal plants showed increased growth rates following defoliation without substantial changes in AMF colonization. At high P supply instead, we found a clear trade-off between regrowth and the maintenance of mycorrhiza evidenced by growth depression (biomass and tillers) and lower AMF activity (reduction of arbuscules). In contrast, in B. brizantha , defoliation effects on plant regrowth were independent from AMF at any P supply (no trade-off). This indicates that cost-benefit relationship in defoliated plants is highly context-dependent and may vary with mycorrhizal responsiveness of species. This variation of responses can play a decisive role on plant recovery in pastures and natural grasslands subjected to herbivory. • First comparative study of AMF, defoliation and P supply in C 3 and C 4 grasses. • In the C 3 grass, AMF promoted recovery from defoliation at low P supply. • Mycorrhiza and defoliation trade off in the C 3 grass at high P supply. • In the C 4 grass, mycorrhizae were beneficial at all environmental contexts. • AMF effects on the recovery from defoliation depend on P supply and plant identity.

The effects of field inoculation of arbuscular mycorrhizal fungi through rye donor plants on grapevine performance and soil properties

Grapevines are highly dependent on arbuscular mycorrhizal fungi (AMF) for normal growth and development. However, vineyard soils may have low AMF abundance and diversity due to conventional soil management practices that are detrimental for these fungi. In this context, the establishment of AMF-inoculated cover crops can be a highly convenient strategy to reestablish soil mycorrhizal potential, as it combines the advantages of a vigorous inoculum source coming from mycorrhizal donor plants with the overall benefits of green covers for grape quality, microbial diversity and soil health. In this work, the potential benefits of Funneliformis mosseae-inoculated under-vine cover crops on grapevine growth, physiology and production were compared to those derived from 1) the establishment of non-inoculated under-vine cover crops, and 2) conventional herbicide-based weed control in the under-vine space. In addition, grapevine root AMF community composition was analyzed to assess if the introduction of a non-native AMF species induced changes on resident mycorrhizal community assemblies and to unveil potential variations in AMF diversity associated to herbicide replacement by green covers. Results indicated that under-vine cover crops, inoculated or not, led to a general vigor decrease in grapevines, probably due to competition between the two species. However, after a heat wave that occurred at harvest time in the second year of the experiment, grapevines growing in plots with inoculated cover crops had the highest photochemical reflectance indices and net photosynthesis rates, and partially compensated production losses due to berry sunburn. Root mycorrhizal community analysis by the end of the experiment revealed that the inoculated F. mosseae isolate colonized grapevine roots from inoculated plots, while it was absent in the other ones. Moreover, inoculation of this AMF did not lead to a replacement of native root AMF communities, but allowed further colonization by other resident Glomeraceae and non-Glomeraceae AMF taxa. Overall, the work herein demonstrates that the introduction of F. mosseae through donor plants is a suitable field inoculation method for grapevines and can help them to better withstand heat waves.

Arbuscular mycorrhizal colonization rate of an exotic plant, Galinsoga quadriradiata, in mountain ranges changes with altitude.

Arbuscular mycorrhizal fungi (AMF) are suggested to be important for invasions by many exotic plants. However, it is not yet known how associations between AMF and invasive plant populations change in mountains ranges and how changed associations affect further expansion of different populations in new habitats. We conducted a field survey to detect AMF colonization rate of the invasive Galinsoga quadriradiata along an elevational gradient ranging from 223 to 1947masl in the Qinling and Bashan Mountains, China. Additionally, a greenhouse experiment was conducted to compare plant growth performance among five elevational populations. In the field, total plant mass and seed production, as well as root AMF colonization rate, significantly decreased with elevation. When populations were grown in a novel soil environment in the greenhouse, the high-altitude populations achieved higher seed and total mass at lower AMF colonization rate than the low-altitude populations. Moreover, high AMF association was related to high intraspecific competition within low-altitude populations and limited seed production. Our results revealed that the associations between AMF and G. quadriradiata decrease with altitude in mountain ranges, and this may indicate that differentiation of association between AMF and elevational populations occurs during range expansion of G. quadriradiata. The results of the greenhouse experiment suggest that the high-altitude populations are more aggressive than the low-altitude populations in a non-stressful environment.

A comparison of the arbuscular mycorrhizal fungal communities among Bangladeshi modern high yielding and traditional rice varieties

Arbuscular Mycorrhizal Fungi (AMF) are ubiquitous soil microorganisms playing a vital role in the functioning of agricultural ecosystems. Although AMF are generally considered to have a low host specificity, it has been suggested that modern plant breeding has selected crop genotypes that are more selectively associated with AMF, possibly resulting in modern high yielding varieties (HYV) having a lower AMF diversity than traditional crop varieties. Whether this is true for paddy rice varieties under field conditions is not known so far. Here, we aimed at comparing differences of AMF communities among modern HYV and traditional rice varieties. We collected root and soil samples of five Bangladeshi rice varieties (two traditional and three modern HYV) from 40 different rice fields and quantified AMF richness, diversity and community composition through high throughput amplicon sequencing of the small subunit (SSU) of the ribosomal RNA cistron. Overall, 75 AMF OTUs, distributed over six AMF families with Glomeraceae as predominant family were found. After accounting for differences in soil conditions, we found that AMF diversity significantly differed among the five varieties and was higher in the traditional than modern varieties. The composition and structure of the AMF communities were distinct between the traditional and modern varieties. An indicator species analysis detected 9 OTUs significantly associated with traditional rice varieties, whereas no indicator OTUs were found for the modern HYV. We conclude that modern breeding coupled with high fertilizer application rates provide a plausible explanation for the reduced AMF diversity and the different AMF community composition between Bangladeshi modern HYV and traditional varieties.

Glomalin-Related Soil Protein Reflects the Heterogeneity of Substrate and Vegetation in the campo rupestre Ecosystem

We examined whether glomalin-related soil protein (GRSP), produced by arbuscular mycorrhizal fungi (AMF), and with role in soil quality, structuring, and carbon storage, varies in relation to substrate and plant community in the campo rupestre ecosystem. Soil samples were collected for physical-chemical and GRSP content analysis, in 40 plots, where the vegetation was also surveyed. GRSP content was compared between substrate types, and its relationship was assessed against soil attributes, vegetation dissimilarity, and abundance of non-mycorrhizal species and species with low AMF dependency. GRSP content varied greatly among the sites (total fraction ranging from 4.66 to 135.46 mg g−1), differed significantly between ferruginous and quartzitic substrates, and was correlated with soil organic carbon (SOC), soil nutrients, soil texture, and vegetation dissimilarity. Total glomalin contributed about 20% to the SOC. GRSP content declined with increasing cover of species that are both sand-binding and have AMF associations, and non-mycorrhizal species. The study shows how AMF, through GRSP, is associated to the ecosystem heterogeneity, suggesting the GRSP as an important soil factor to be considered in management and conservation issues in campo rupestre and similar ecosystems. GRSP content was shown to contribute to carbon storage and was linked to soil chemical and physical properties, and affected by variation in cover of non- or less-AMF-dependent plant species, perhaps providing a useful indicator in the heterogeneous campo rupestre system.

Silencing MdGH3-2/12 in apple reduces cadmium resistance via the regulation of AM colonization

Arbuscular mycorrhizal fungi (AMF) can form a symbiotic relationship with most terrestrial plant roots, promote plant growth, and heavy metal (HM) tolerance and thus plays a crucial role in phytoremediation. However, research on the relationship between colonization level and HM tolerance is limited. In this study, apple (Malus domestica) Gretchen Hagen3 genes MdGH3-2/12 silencing plants were treated with four AMF and Cd combination treatments to determine AMF colonization levels, biomass, Cd accumulation, photosynthesis, fluorescence, reactive oxygen species (ROS) and antioxidant substance accumulation, and Cd uptake, transport and detoxification gene expression levels. Results indicate the greater sensitivity of transgenic plants under AMF inoculation and Cd treatment compared with wild type (WT) via lower AMF colonization levels, biomass accumulation, photosynthetic parameters, and the accumulation and clearance homeostasis of ROS, as well as lower detoxification expression levels and higher Cd uptake and transport expression levels. Our study essentially demonstrates that MdGH3-2/12 plays an important role in Cd stress tolerance by regulating AM colonization in apple.

Effects of single and multiple species inocula of arbuscular mycorrhizal fungi on the salinity tolerance of a Bangladeshi rice (Oryza sativa L.) cultivar.

Soil salinization due to sea level rise and groundwater irrigation has become an important agronomic problem in many parts of the world. Symbiosis between crop species and arbuscular mycorrhizal fungi (AMF) may alleviate salt stress-induced detrimental effects on crop growth and yield, for example, through helping the host plant to selectively absorb potassium while avoiding uptake of excessive sodium. Here, we performed a greenhouse experiment to evaluate growth, grain yield, and salt tolerance of a Bangladeshi rice cultivar under three levels of salt stress (0, 75, and 120mM) after inoculation with three different AMF species from three different genera (Funnelliformis mosseae (BEG12), Acaulospora laevis (BEG13), and Gigaspora margarita (BEG34)), singly and in combination. We found that under salt stress, AMF inoculation enhanced total chlorophyll concentration, shoot K+/Na+ ratio, and lowered shoot Na+/root Na+ ratio, accompanied by increased root biomass, spikelet fertility, and grain yield compared with the non-inoculated control plants. Specifically, we found that the combination of BEG13 and BEG34 increased rice yield by 125 and 143% as compared with the non-inoculated controls, at the 75 and 120mM salt levels, respectively. In general, the low AMF diversity treatments (one species or a combination of two AMF species) were found to be the most effective in mediating salt stress tolerance for the majority of the measured crop performance variables. Overall, our results indicate that specific AMF species can promote the salt tolerance and productivity of rice, likely by increasing photosynthetic efficiency and restricting Na+ uptake and transport from root to shoot in AMF-inoculated plants.

The influence of soil warming on organic carbon sequestration of arbuscular mycorrhizal fungi in a sub-arctic grassland

A substantial portion of grassland photosynthates is allocated belowground to arbuscular mycorrhizal fungi (AMF), but controversy remains about whether this carbon (C) contributes to soil organic carbon (SOC) under warming. The goal of this study was to investigate how AMF biomass and C sequestered by AMF (CNew) are influenced by soil warming. We estimated the AMF biomass and CNew, assumed to be mostly AMF necromass, in mycelial ingrowth bags buried for 1, 2, or 3 years in soil under warming (~+0.5–16.4 °C). The AMF biomass had a positive, curvilinear response to warming gradients after one year of burial. About 107 g C m−2 of CNew accumulated over the three years and ~12% of this C was from glomalin-related soil protein. Modelling suggested the production rate of AMF biomass was 153 g C m−2 yr−1 with a rapid (36–75 days) turnover while AMF necromass turnover was much slower (1.4 ± 0.2 yr−1). Warming duration (7–9 years vs. > 50 years) did not have significant influence on AMF biomass or CNew (P > 0.05). Our results suggest that AMF are more tolerant to increases in temperature than other microbes or fine roots. The dramatic loss of soil C and stable soil aggregates under warming found earlier at this site were not attributed to a decrease in AMF biomass or CNew. Despite a low AMF standing biomass, its contribution to SOC may be substantial.

Genetic and phenotypic associations between root architecture, arbuscular mycorrhizal fungi colonisation and low phosphate tolerance in strawberry (Fragaria \xd7 ananassa)

BackgroundPhosphate is an essential plant macronutrient required to achieve maximum crop yield. Roots are able to uptake soil phosphate from the immediate root area, thus creating a nutrient depletion zone. Many plants are able to exploit phosphate from beyond this root nutrient depletion zone through symbiotic association with Arbuscular Mycorrhizal Fungi (AMF). Here we characterise the relationship between root architecture, AMF association and low phosphate tolerance in strawberries. The contrasting root architecture in the parental strawberry cultivars ‘Redgauntlet’ and ‘Hapil’ was studied through a mapping population of 168 progeny. Low phosphate tolerance and AMF association was quantified for each genotype to allow assessment of the phenotypic and genotypic relationships between traits.ResultsA “phosphate scavenging” root phenotype where individuals exhibit a high proportion of surface lateral roots was associated with a reduction in root system size across genotypes. A genetic correlation between “root system size” traits was observed with a network of pleiotropic QTL found to represent five “root system size” traits. By contrast, average root diameter and the distribution of roots appeared to be under two discrete methods of genetic control. A total of 18 QTL were associated with plant traits, 4 of which were associated with solidity that explained 46% of the observed variation. Investigations into the relationship between AMF association and root architecture found that a higher root density was associated with greater AMF colonisation across genotypes. However, no phenotypic correlation or genotypic association was found between low phosphate tolerance and the propensity for AMF association, nor root architectural traits when plants are grown under optimal nutrient conditions.ConclusionsUnderstanding the genetic relationships underpinning phosphate capture can inform the breeding of strawberry varieties with better nutrient use efficiency. Solid root systems were associated with greater AMF colonisation. However, low P-tolerance was not phenotypically or genotypically associated with root architecture traits in strawberry plants. Furthermore, a trade-off was observed between root system size and root architecture type, highlighting the energetic costs associated with a “phosphate scavenging” root architecture.

Effect of aboveground plant conditioner treatment on arbuscular mycorrhizal colonization of tomato and pepper

We aimed to test the hypothesis that treatment with an aboveground plant conditioner has an effect on important vegetable crops inoculated with arbuscular mycorrhizal fungi (AMF) and on their colonization by AMF. Potting experiments were set with pepper and tomato plants inoculated with commercial AMF inoculum and plants were treated with an aboveground plant conditioner. After harvesting, the dry weight of shoots and roots were measured, and the AMF colonization of the roots was quantified. We found a significant effect of the treatment on fungal colonization: the AMF colonization, the hyphal colonization rate and the frequency of the arbuscules in the roots of both vegetables were lower when aboveground plant conditioner was applied. Although the two species differed, no significant effect of the treatment on the growth of the plants was detected. Based on our findings we assumed that the lower AMF colonization more greatly influenced the growth of the pepper cultivar studied. We demonstrated that treatment with a commercial aboveground plant conditioner had an antagonistic effect on AMF colonization, which, in addition to many other effects, might influence the growth vegetable crops. The interaction of different practices applied simultaneously should be tested to effectively help the development suitable agriculture systems.

Isolation of Iindigenous arbuscular mycorrhizal fungi (AMF) to support revegetation on the nickel post-mining land

The revegetation on the nickel post-mining area requires symbiotic associations with mycorrhizal fungi to support the plant growth because it faces major obstacles of harsh soil condition. The study was conducted to identify the AMF status on the nickel post-mining land and its association with pioneer plant roots. Soil and root sampling werewas collected on 4 type areas of nickel post-mining land i.e TR (top soil + revegetation), TNR (top soil + no revegetation), NTR (no top soil + revegetation) and NTNR (no top soil + no revegetation) to determine spore density, soil chemical properties and AMF colonization. The results showed that the nickel mining activities interfere in soil fertility and soil microbial population. It was denoted by lack available nutrient and low AMF diversity. Population of AMF only 7 – 83 spore per gram soil. Glomus or Acaulospora is dominating genus in each area. However, AMF occurrence is a vital to help the pioneer plants growth. It was proven by 163 species of pioneer plants that colonize nickel post-mining land associated with the AMF in their root system. Grass species have highest AMF colonization level. Therefore, inoculation of AMF indigenous isolate is needed as an intervention ion post-mining reclamation effort, so the possibility of symbiosis between plant roots and AMF becomes increasing. Eventually the development of natural plants will be accelerated to catalytic the natural succession process.

Tripartite Interactions Between Endophytic Fungi, Arbuscular Mycorrhizal Fungi, and Leymus chinensis.

Grasses often establish multiple simultaneous symbiotic associations with endophytic fungi and arbuscular mycorrhizal fungi (AMF). Many studies have examined pair-wise interactions between plants and endophytic fungi or between plants and AMF, overlooking the interplays among multiple endosymbionts and their combined impacts on hosts. Here, we examined both the way in which each symbiont affects the other symbionts and the tripartite interactions between leaf endophytic fungi, AMF, and Leymus chinensis. As for AMF, different species (Glomus etunicatum, GE; Glomus mosseae, GM; Glomus claroideum, GC; and Glomus intraradices, GI) and AMF richness (no AMF, single AMF taxa, double AMF mixtures, triple AMF mixtures, and all four together) were considered. Our results showed that significant interactions were observed between endophytes and AMF, with endophytes interacting antagonistically with GM but synergistically with GI. No definitive interactions were observed between the endophytes and GE or GC. Additionally, the concentration of endophytes in the leaf sheath was positively correlated with the concentration of AMF in the roots under low AMF richness. The shoot biomass of L. chinensis was positively related to both endophyte concentration and AMF concentration, with only endophytes contributing to shoot biomass more than AMF. Endophytes and AMF increased shoot growth by contributing to phosphorus uptake. The interactive effects of endophytes and AMF on host growth were affected by the identity of AMF species. The beneficial effect of the endophytes decreased in response to GM but increased in response to GI. However, no influences were observed with other GC and GE. In addition, endophyte presence can alter the response of host plants to AMF richness. When leaf endophytes were absent, shoot biomass increased with higher AMF richness, only the influence of AMF species identity outweighed that of AMF richness. However, when leaf endophytes were present, no significant association was observed between AMF richness and shoot biomass. AMF species identity rather than AMF richness promoted shoot growth. The results of this study demonstrate that the outcomes of interspecific symbiotic interactions are very complex and vary with partner identity such that the effects of simultaneous symbioses cannot be generalized and highlight the need for studies to evaluate fitness response of all three species, as the interactive effects may not be the same for each partner.