Plant Arbuscular Mycorrhizal Fungi Research Articles

Response of a wild-type and modern cowpea cultivars to arbuscular mycorrhizal inoculation in sterilized and non-sterilized soil

ABSTRACTCowpea is an important crop that serves as a legume and vegetable source to many smallholder farmers in sub-Saharan Africa. Soil fertility is a significant limitation to its production thus; inoculation with beneficial soil biota such as arbuscular mycorrhizal fungi (AMF) could improve its performance. However, plant–AMF interaction could vary based on crop cultivar hence affecting overall crop production. The present study aimed at determining the effect of AMF inoculation and soil sterilization on root colonization and growth of a wild-type and three modern cowpea cultivars grown by smallholder farmers in Kenya. Potted cowpea plants were inoculated with a commercial AMF inoculum comprising of Rhizophagus irregularis, Funneliformis mosseae, Glomus aggregatum and Glomus etunicatum and maintained in a greenhouse for 40 days. After harvesting, mycorrhizal colonization, nodule number and dry weight, root and shoot dry weights, nitrogen (N,) phosphorus (P) and potassium (K) content were determined. Interestingly, the modern cultivars showed significantly (p < 0.001) higher root colonization, nodulation, shoot P and N compared to the wild-type cultivar. Moreover, a strong positive correlation between AMF root colonization and shoot P (r2 = 0.73, 0.90, p < 0.001), AMF root colonization and shoot N (r2 = 0.78; 0.89, p < 0.001) was observed in both sterilized and non-sterilized soil, respectively. Soil sterilization affected root colonization and growth parameters with plants grown in non-sterilized soil performing better than those grown in sterilized soil. This study provides major evidence that modern cowpea cultivars are still responsive to mycorrhizal inoculation suggesting that modern breeding programs are not deleterious AMF symbiosis.

Recent Perspectives on Cross Talk Between Cadmium, Zinc, and Arbuscular Mycorrhizal Fungi in Plants

Soils polluted with heavy metals result into various environmental and ecological tribulations like alterations in microbial community, deterioration of soil, and induction of metals into the human food chain. Noxious heavy metals, for instance, cadmium (Cd) and essential micronutrients like zinc (Zn) have identical chemical properties and are normally taken up by plants via similar carrier proteins as those of indispensable micronutrients. Cohesive interactions between plants and microbes and their co-existence or struggle for survival play a fundamental role in acclimatizing to metal-polluted environments. In this context, arbuscular mycorrhizal (AM) fungi are regarded as a prospective biotechnological approach for increasing tolerance of plants to heavy metal-polluted soils. However, the vital molecular factors responsible for regulating metal homeostasis/balance in these microbes have been poorly understood. Moreover, combined studies assessing the effect of AM fungal inoculation in alleviating Cd and/or Zn toxicity in plants and the underlying mechanisms are still unclear. This review presents the updated information on cross talk between Cd–Zn–AM in plants grown on agricultural and metal-contaminated soils.

Plant-symbiont interactions: the functional role of expansins

Expansins are non-enzymatic cell wall proteins that mediate plant growth by catalyzing loosening of cell walls without lysing the wall polymers. Advances in the field of bioinformatics have facilitated the prediction of the members of expansin gene family across several model plants. Expansins constitutes into four sub-families; α-expansin, β-expansin, expansin-like A and expansin-like B. Biological functions of expansin gene family include diverse aspects of plant growth and development, shoot and root elongation, leaf morphogenesis, flower and fruit development, embryogenesis, pollen tube growth, stress tolerance, etc. Recent studies have demonstrated the role of expansins in plant-symbiotic interactions. The present review reveals the factors that govern plant-arbuscular mycorrhizal fungi (AMF) and legume-rhizobia symbioses; and the genes that participate in these diverse symbiont interactions. Further, we focus on the expression profiles and the functions of expansins during plant-AMF and legume-rhizobia interactions. The key roles of expansin proteins during AMF invasion, arbuscule formation, rhizobial infection and nodule organogenesis were uncovered during symbioses. This review summarizes discoveries that support the key and versatile roles of various expansin members in the plant-mycorrhizal and legume-rhizobial symbioses.

Management of the biological diversity of AM fungi by combination of host plant succession and integrity of extraradical mycelium

As functional diversity influences the benefits conferred on host plants by arbuscular mycorrhizal fungi (AMF) and large scale commercial inoculation is currently impracticable, strategies are required to manage communities of indigenous AMF associated with different hosts within agricultural cropping systems. In a non-sterilized soil, using 454 pyrosequencing of the LSU-D2 rDNA gene, host plant AMF diversity was assessed following successions of different plant species, grown with or without prior soil disturbance. Diversity present in the roots of two species of the Fabaceae (Ornithopus compressus and Trifolium subterraneum) was compared with those of two species of Poaceae (Lolium rigidum and Triticum aestivum). When spores and colonised root fragments formed were the main propagules source (disturbed soil), the communities of AMF present in the two legumes were clearly different from those of the two members of the Poaceae but were similar for plants within each family, consistent with there being preferential symbioses existing within an AMF population for host classes. Significantly, wheat grown in undisturbed soil immediately after the legume O. compressus acquired a mycorrhizal fungal community closely related to that of the previous host plant, and different to that found when the soil was disturbed or not cropped prior to the growth of the wheat. Parallel effects were seen in the succession from L. rigidum to T. subterraneum, indicating that these effects are not unique to the legume-wheat sequence. These results also suggest that, under no-till cropping, selected cover crops or crops in rotation could help build mycorrhizal communities that function throughout a sequence of several main crops.

The abundance and diversity of arbuscular mycorrhizal fungi are linked to the soil chemistry of screes and to slope in the Alpic paleo-endemic Berardia subacaulis.

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.

PERTUMBUHAN KACANG HIAS (Arachis pintoi) PADA MEDIA TANAH PASCA PENAMBANGAN BATUBARA YANG DIPERKAYA MIKORIZA, KAPUR DAN PUPUK NPK

This study aimed to determine the effects of the provision of arbuscular mycorrhizal fungi (AMF), the provision of lime, and the provision of NPK fertilizer, and the interaction effect of the provision of Arbuscular mycorrhizal fungi (AMF), lime and NPK fertilizers in promoting the growth of pinto peanut in the soil media of post-mining land. The research method used was a completely randomized design (CRD) three-factor factorial with the first factor is the type of inoculant FMA (M) = 3 levels, the second factor is the provision of lime (K) = 3 levels, and the third factor is the NPK fertilizer (P) = 3 levels. These results indicated that the interaction between AMF Glomus sp. and NPK fertilizer dose of 1 gram/polybag can increase height increase pinto peanut plants for 34.16 % of the controls. The interaction between AMF Gigaspora sp. The lime dose of 50 % Al-dd and Fertilizers NPK dose of 1 gram/polybag can increase the growth of leaves pinto peanut plants at 108.33 % of the controls. The interaction between AMF Glomus sp. and NPK fertilizer dose of 2 grams/polybag can increase canopy and root biomass pinto peanut plants at 245.21 % of the controls. The interaction between AMF Glomus sp. and NPK fertilizer dose of 2 grams/polybag can increase canopy and root biomass pinto peanut plants at 245.21 % of the controls. Level relative mycorrhizal dependency (RMD) was influenced by the type of AMF plant inoculated host. Highest RMD shown in pinto peanut using AMF Glomus sp. is 31.99% at moderately dependent.

Arbuscular mycorrhizal fungi in changing mountain grassland ecosystems: a challenge for research

Even though arbuscular mycorrhizal fungi (AMF) are present from foothills to all alpine habitats, research on their role in mountain ecosystems remains incomplete. Here we provide a literature review of the ecology and functioning of AMF in mountain ecosystems, as well as their response to global change. We investigated how AM fungal abundance, community composition, and fungal traits are studied under field conditions and are affected by altitude, habitat patchiness, succession, host identity, seasonality, and interaction with other living organisms. The effects of climate change, nutrient enrichment, land-use change, and their interactions are also addressed in this review, as well as the possible applications of AMF for grassland restoration. We show that altitudinal effects on AMF are blurred by other environmental gradients and by host-plant identity. The benefits to plants and possible facilitation effects by AMF in mountain ecosystems have not yet been identified. Based on the stress-gradient hypothesis, the symbiosis between plants and AMF should become more mutualistic with increasing environmental stress. We propose a working hypothesis for the functioning of the AMF–plant interaction along altitudinal gradients by grading it along the mutualism–parasitism continuum, considering current and global climate and environmental change conditions. We conclude by suggesting further research directions.

Plant–mycorrhizal fungus co‐occurrence network lacks substantial structure

The interactions between plants and arbuscular mycorrhizal fungi (AMF) maintain a crucial link between macroscopic organisms and the soil microbial world. These interactions are of extreme importance for the diversity of plant communities and ecosystem functioning. Despite this importance, only recently has the structure of plant–AMF interaction networks been studied. These recent studies, which used genetic data, suggest that these networks are highly structured, very similar to plant–animal mutualistic networks. However, the assembly process of plant–AMF communities is still largely unknown, and an important feature of plant–AMF interactions has not been incorporated: they occur at an extremely localized scale. Studying plant–AMF networks in a spatial context seems therefore a crucial step. This paper studies a plant–AMF spatial co‐occurrence network using novel methodology based on information theory and a unique set of spatially explicit species‐level data. We apply three null models of which only one accounts for spatial effects. We find that the data show substantial departures from null expectations for the two non‐spatial null models. However, for the null model considering spatial effects, there are few significant co‐occurrences compared with the other two null models. Thus, plant–AMF spatial co‐occurrences seem to be mostly explained by stochasticity, with a small role for other factors related to plant–AMF specialization. Furthermore, we find that the network is not significantly nested or modular. We conclude that this plant–AMF spatial co‐occurrence network lacks substantial structure and, therefore, plants and AMF species do not track each other over space. Thus, random encounters seem more important in the first step of the assembly of plant–AMF communities.SynthesisThe symbiotic interaction between plants and arbuscular mycorrhizal fungi (AMF) is crucial for ecosystem functioning. However, the factors affecting the assembly of plant‐AMF communities are poorly understood. An important factor of the assembly of plant‐AMF communities has been overlooked: plant‐AMF interactions occur at a localized spatial scale. Our study investigated the importance of space in the structure of plant‐AMF communities. We studied a plant‐AMF spatial co‐occurrence network using a unique set of spatially explicit data and applied three null models. We found that plant‐AMF spatial co‐occurrences seem to be mostly explained by stochasticity. In particular, our study shows that this plant‐AMF spatial co‐occurrence network lacks substantial structure and, therefore, plants and AMF species do not track each other over space. Thus, random encounters seem to drive the assembly of plant‐AMF communities.

Effects of arbuscular mycorrhizal fungi onCapsicumspp.

SUMMARYThe benefits of mycorrhizal inoculation on growth, yield and nutrition of plants are well documented. However, mycorrhiza use in pepper and sweet pepper crops (Capsicumspp.) is still rarely exploited compared to other crops of economic importance. The current paper reviews the main aspects of the association between arbuscular mycorrhizal (AM) fungi and plants of pepper and sweet pepper. It includes topics about the effects of AM fungi on nutrition, growth and yield inCapsicumspp., paying particular attention to AM fungi–pathogen interactions, responses to some environmental stresses, as well as biochemical and physiological aspects of AM fungi–plant interaction inCapsicum annuumL.

Plant identity and density can influence arbuscular mycorrhizal fungi colonization, plant growth, and reproduction investment in coculture

Reciprocal effects between arbuscular mycorrhizal fungi (AMF) and plant communities are essential to study the complexity of interactions in a grassland ecosystem. Here, we investigated the effects of plant community density and composition on AMF colonization, plant growth, and reproduction investment. We developed an experimental system with three compartments, each containing either three or six Medicago truncatula Gaertn. plants, or three M. truncatula plants associated with three Silene vulgaris (Moench) Garcke plants. All three compartments shared the same common mycorrhizal network built either by Rhizophagus irregularis MUCL 43194, by Rhizophagus clarus MUCL 46238, or by both AMF in association grown in a central compartment on Plantago lanceolata L. Our results demonstrate an absence of effect of plant density but a positive influence of mixed cultures on AMF root colonization compared with monocultures. This higher AMF development resulted in a positive feedback on shoot biomass and number of flowers and fruits produced by M. truncatula. Although both fungal strains were present in root systems, co-inoculation did not generate a synergistic effect on plant development. These results highlight the importance of plant associations on AMF dynamics, which requires further investigation at the community scale to improve our understanding of the intricate AMF – host plant relationships.

Using hybrid automata modelling to study phenotypic plasticity and allocation strategies in the plant mycorrhizal mutualism

Plants are exemplified by high plasticity in resource allocation strategies which allows them to maximize their fitness under changing resource conditions. In many plant species, obtaining resources involves mutualistic interactions with arbuscular mycorrhizal fungi (AMF), where plants provide the AMF with sugars in exchange for soil nutrients like phosphorus (P). These nutrient exchange rates have high context dependency, influenced by both the cooperative level of the AMF species involved (a qualitative trait) and the ambient nutrient concentrations in the soil (a quantitative value). Because this context dependency arises from a mix of both quantitative and qualitative factors, standard ordinary differential equation (ODE) modeling methods often complicate the representation of resource allocation strategies. Here, we explore the utility of a hybrid automata modeling framework that can intuitively combine the qualitative AMF traits and quantitative nutrient concentrations. This allows for a better analysis and understanding of phenotypic plasticity in resource allocation in the plant–AMF, and other nutrient exchange mutualisms. We consider a focal strategy in which nutrients are allocated to growth at times of nutrient limitations, and to storage otherwise and ask how this changes plant allocation to growth vs. storage. We first model this system dynamically to show how the plant responds to different environmental conditions and interacts with AMF and show that our hybrid automata model can replicate experimental data from the plant–AMF system. From our work, novel perceptions into the well-studied plant–AMF symbiosis and testable hypotheses can be underlined: (1) leaf biomass does not increase proportionally with the level of AMF cooperation; (2) in the context of multiple AMF simultaneously colonizing a host–plant, a narrow variance of response is observed and explained by an auction-like mechanism of the AMF to acquire C from the plant.

Species-dependent partitioning of C and N stable isotopes between arbuscular mycorrhizal fungi and their C3 and C4 hosts

Natural 13C and 15N abundances of mycorrhizal fungi are increasingly used in ecology but reference data on arbuscular mycorrhizal fungi (AMF) are scarce. In experiments with nine phylogenetically dispersed AMF strains inoculated on leek (C3 plant) and sorghum (C4) in pot cultures, we measured the 13C/12C and 15N/14N ratios in shoots, roots, AMF spores as well as carbon isotope signature of the C16:1ω5 fatty acid (FA), which is diagnostic for AMF. Spore δ13C values varied among AMF strains on any given host. They were significantly lower than shoot δ13C for sorghum (−2.5‰ on average) while for leek, no clear C isotope partitioning between spores and host shoots was observed. The FA C16:1ω5 fatty acids were more 13C-depleted than spores, without correlation with spore δ13C values. For both, sorghum and leek, spore δ15N was higher (+1–2‰ on average) than for shoots. We found no evidence that isotopic partitioning between the partners drives 13C and 15N abundances in plant–AMF symbiosis. Mycorrhizal roots displayed relatively high δ13C typical for heterotrophic organs, and not a mix between AMF and plant signatures. Interestingly, inoculation slightly decreased shoot δ13C on leek but not on sorghum, as compared with non-mycorrhizal plants, suggesting that AMF improved the plant's water status, a parameter affecting the δ13C of C3 but not C4 plants. Phylogenetically closer AMF displayed more similar spore δ13C and induced similar 13C and 15N abundances on leek shoots, but this observation was not confirmed for sorghum. Plant and AMF isotopic abundances hardly correlated with other parameters related to plant development, mineral nutrition or root mycorrhizal colonisation, and these correlations were never consistent between sorghum and leek. Thus, isotopic abundances in plant–AMF symbiosis were rather constrained by each AMF/plant interaction. Nevertheless, our data provide a valuable reference for future investigations of AMF communities and AM symbiosis in situ.

Effect of biosolids-derived triclosan and triclocarban on the colonization of plant roots by arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) form a symbiotic relationship with the majority of crop plants. AMF provide plants with nutrients (e.g., P), modulate the effect of metal and pathogen exposure, and increase tolerance to moisture stress. The benefits of AMF to plant growth make them important to the development of sustainable agriculture. The land application of biosolids is becoming an increasingly common practice in sustainable agriculture, as a source of nutrients. However, biosolids have been found to contain numerous pharmaceutical and personal care products including antimicrobial chemicals such as triclosan and triclocarban. The potential risks that these two compounds may pose to plant–AMF interactions are poorly understood. The current study investigated whether biosolids-derived triclosan and triclocarban affect the colonization of the roots of lettuce and corn plants by AMF. Plants were grown in soil amended with biosolids that contained increasing concentrations of triclosan (0 to 307μg/g dw) or triclocarban (0 to 304μg/g dw). A relationship between the concentration of triclosan or triclocarban and colonization of plants roots by AMF was not observed. The presence of biosolids did not have a significant (p>0.05) effect on percent colonization of corn roots but had a significant, positive effect (p<0.05) on lettuce roots. Biosolids-derived triclosan and triclocarban did not inhibit the colonization of crop plant roots by AMF.

Evidence for phylogenetic correlation of plant-AMF assemblages?

Specificity in biotic interactions is mediated' by functional traits inducing shifts in the community species composition. Functional traits are often evolutionarily conserved, resulting in closely related species tending to interact with similar species. This tendency may initially shape the phylogenetic composition of coexisting guilds, but other intraguild ecological processes may either blur or promote the mirroring of the phylogenetic compositions between guilds. The roles of intra- and interguild interactions in shaping the phylogenetic community composition are largely unknown, beyond the mere selectivity in the interguild interactions. Plant facilitation is a phylogenetically structured species-specific process involving interactions not only between the same guild of plants, but also between plants and other guilds such as arbuscular mycorrhizal fungi (AMF). In this study it is hypothesized that reciprocal plant-AMF interactions will leave an interdependent phylogenetic signal in the community composition of both plants and AMF. A correlation was used to test for a relationship between the phylogenetic composition of plant and AMF assemblages in a patchy xeric shrubland environment shaped by plant facilitation. In addition, a null model was used to test whether this correlation can be solely explained by selectivity in plant-AMF interactions. A significant correlation was observed between the phylogenetic composition of plant and AMF assemblages. Plant phylogenetic composition in a patch was related to the predominance of plant species with high nursery quality that can influence the community assembly. AMF phylogenetic composition was related to the AMF phylogenetic diversity in each patch. This study shows that shifts in the phylogenetic composition of plants and AMF assemblages do not occur independently. It is suggested that besides selectivity in plant-AMF interactions, inter-related succession dynamics of plants and AMF within patches could be an ecological mechanism driving community assembly. Future lines of research might explore whether interlinked above- and below-ground dynamics could be occurring across multiple guilds simultaneously.

Arbuscular mycorrhizal symbiosis influences arsenic accumulation and speciation in Medicago truncatula L. in arsenic-contaminated soil

In two pot experiments, wild type and a non-mycorrhizal mutant (TR25:3-1) of Medicago truncatula were grown in arsenic (As)-contaminated soil to investigate the influences of arbuscular mycorrhizal fungi (AMF) on As accumulation and speciation in host plants. The results indicated that the plant biomass of M. truncatula was dramatically increased by AM symbiosis. Mycorrhizal colonization significantly increased phosphorus concentrations and decreased As concentrations in plants. Moreover, mycorrhizal colonization generally increased the percentage of arsenite in total As both in shoots and roots, while dimethylarsenic acid (DMA) was only detected in shoots of mycorrhizal plants. The results suggested that AMF are most likely to get involved in the methylating of inorganic As into less toxic organic DMA and also in the reduction of arsenate to arsenite. The study allowed a deeper insight into the As detoxification mechanisms in AM associations. By using the mutant M. truncatula, we demonstrated the importance of AMF in plant As tolerance under natural conditions.

Termites and ungulates affect arbuscular mycorrhizal richness and infectivity in a semiarid savanna

In savanna ecosystems, mound-building termites and ungulate herbivores profoundly affect the abundance and diversity of aboveground organisms. Yet, surprisingly little is known about how these two groups interact to impact belowground communities. Using the Kenya Long-term Exclosure Experiment (KLEE), where ungulate herbivores have been excluded for over 15 years, we examined how the presence of termites and ungulate herbivore exclusion affected species richness, community composition, and infectivity of arbuscular mycorrhizal fungi (AMF). We also measured plant richness and soil nutrients to examine how the effects of termites and ungulate exclusion may indirectly impact AMF communities. AMF richness and infectivity and plant richness were significantly lower on termite mounds than in off-mound areas. AMF infectivity and plant richness were significantly higher in off-mound areas, especially where herbivores had access. Our results revealed a strong suppressive effect of termites on AMF communities that was not enhanced or ameliorated by the presence of ungulate herbivores. Herbivores, by contrast, enhanced the relationship between plants and their fungal symbionts but only in the absence of the suppressive effects of termites. Our results underscore the importance of multiple drivers affecting the patterns of both above- and below-ground communities.

来源对丛枝菌根真菌功能的影响

丛枝菌根真菌（arbuscular mycorrhizal fungi，AMF）是一种具有重要生态功能的根际微生物。影响AMF功能的因素主要包括AMF、宿主，以及其它生物与非生物环境。近年来，大量研究表明不同来源的AMF功能存在显著差异。结合该领域的最新研究成果，从基因变异和表型可塑性两方面分析了来源影响AMF功能的原因和维持机制，并对其生态学意义进行了探讨。认为应从群落水平上研究不同来源的AMF在生态系统中的功能，重视宿主的作用，保持研究对象的对等性，并区分AMF群落结构和来源对功能的不同影响。对未来的研究重点和方向进行了讨论和展望，试图为更加清晰、全面地认识AMF在生态系统中的功能，以及AMF适应特定土壤环境与宿主的机制提供参考。;The ubiquitous arbuscular mycorrhizal fungi (AMF) form obligate symbiotic associations with the roots of more than 80% terrestrial plants. AMF play multiple ecologically important roles in various ecosystems. In exchange for carbon, AMF assist the host plant in acquiring mineral nutrients (especially for the less mobile element, phosphorus), enhance stress tolerance, provide bio-protection from soil-borne pathogens and mediate plant-plant interactions.<br>The effectiveness of AMF in carrying out their ecological role(s) depends on the compatibility between AMF and host plant, and also the corresponding biotic/abiotic environments. In the past decades, there is ample evidence to suggest that in most cases AMF from different origins were significantly different in their effectiveness on host plants. Here, we reviewed the effects of fungal origin on AMF functioning, analyzed its causes, maintenance mechanisms, and ecological significance based on the novel interests and latest advancements. The functional differences could occur among both AMF species and among different isolates of the same species. In general, the native AMF isolates performed better and were more efficient in promoting plant growth when compared to the exotic counterparts, although contradictory results were also reported. At present, however, there were several problems that were not addressed properly in most of the previous studies. Firstly, the disparities of AMF effects on plant performance were rarely measured at the whole community level. AMF typically occur as extensive fungal assemblages in nature, and will colonize most if not all the plant roots simultaneously within the community. The behavior and functioning of a mixture of AMF species are very different to a single species partly due to the functional complementarity, synergistic relationships and competition between various AMF species. Therefore, the community level comparison of AMF functioning is more relevant to the actual field situations. Secondly, the comparisons between different AMF species or single AMF species and community from different origins are probably not useful, as they are intrinsically different by nature. Thirdly, it is incorrect to attribute the functional variation of naturally occurring AMF communities exclusively to their origins, the influences of origin, and structure of AMF communities should be considered as equally important and distinguished explicitly. Fourthly, the effects of host plant or even neighboring plant on AMF functioning should not be ignored as they are likely to change the AMF genotype, phenotype and the associated community structure.<br>The significance of origin in AMF functioning could probably be attributed to the differences in soil physiochemical property and host identity. AMF are characterized by multi-genome inheritance and are susceptible to nuclei segregation and genetic recombination. Perturbations in soil and host will induce rapid genetic variation and this may encourage phenotypic plasticity in AMF at the individual level, or cause structural change at the community level.<br>Finally, we suggest that (1) a combined method of traditional AMF spore counting and molecular analysis of AMF community colonizing plant roots should be used; (2) long-term monitoring and assessment are clearly needed considering the differences of various AMF in adaptability; (3) more attentions should be paid on the effects of AMF on plant-plant interactions and ecological processes rather than focusing on an individual plant. This review article examines the current understanding of the roles AMF play in ecosystems and discusses how a given AMF community is better matched ecologically to its local soil condition and plant habitat than communities from foreign geographical sources.

Phytate utilization of maize mediated by different nitrogen forms in a plant–arbuscular mycorrhizal fungus–phosphate-solubilizing bacterium system

A pot experiment was conducted to investigate the organic phosphorus (P) (phytate) utilization of Zea mays L. with different nitrogen (N) forms (NH4+ and NO3−) when both arbuscular mycorrhizal (AM) fungus (Funelliformis mosseae) and phosphate-solubilizing bacterium (PSB, Pseudomonas alcaligenes) are present. The soil was supplied with either KNO3 or (NH4)2SO4 (200 mg kg−1 N) with or without phytin (75 mg P kg−1). Results showed that the application of NH4+ to the soil in a plant–AM fungus–PSB system decreased rhizosphere pH and increased phosphatase activity. It also enhanced the mineralization rate of phytin, which resulted in the release of more inorganic P. The application of NO3− promoted mycorrhizal colonization and hyphal length density in the soil. The inorganic P in the hyphosphere decreased, but more P was transferred to the plant through the mycorrhizal hyphae. Hence, in addition, the application of the two different N forms did not significantly alter the content of plant P. The plant supplied with different N fertilizers acquired P through different mechanisms associated with other microbes. NH4+ application promoted phytin mineralization by decreasing soil pH, whereas NO3− application increased inorganic P uptake by strengthening the mycorrhizal pathway.

Differential effects of abiotic factors and host plant traits on diversity and community composition of root-colonizing arbuscular mycorrhizal fungi in a salt-stressed ecosystem

Arbuscular mycorrhizal fungi (AMF) were investigated in roots of 18 host plant species in a salinized south coastal plain of Laizhou Bay, China. From 18 clone libraries of 18S rRNA genes, all of the 22 AMF phylotypes were identified into Glomus, of which 18 and 4 were classified in group A and B in the phylogenetic tree, respectively. The phylotypes related to morphologically defined Glomus species occurred generally in soil with higher salinity. AMF phylotype richness, Shannon index, and evenness were not significantly different between root samples from halophytes vs. non-halophytes, invades vs. natives, or annuals vs. perennials. However, AMF diversity estimates frequently differed along the saline gradient or among locations, but not among pH gradients. Moreover, UniFrac tests showed that both plant traits (salt tolerance, life style or origin) and abiotic factors (salinity, pH, or location) significantly affected the community composition of AMF colonizers. Redundancy and variation partitioning analyses revealed that soil salinity and pH, which respectively explained 6.9 and 4.2 % of the variation, were the most influential abiotic variables in shaping the AMF community structure. The presented data indicate that salt tolerance, life style, and origin traits of host species may not significantly affect the AMF diversity in roots, but do influence the community composition in this salinized ecosystem. The findings also highlight the importance of soil salinity and pH in driving the distribution of AMF in plant and soil systems.

Examining the ecological paradox of the ‘mycorrhizal-metal-hyperaccumulators’

This analysis identifies and attempts to resolve the paradox of combining plant hyperaccumulators and arbuscular mycorrhizal fungi (AMF) for the purpose of post-industrial bioremediation due to the divergence of their respective ecological and evolutionary stress-tolerance behaviors. The identification of a ‘dilemma of resource allocation’ associated with plant resources consumed in intrinsic (e.g. metabolic) vs. extrinsic (e.g. symbiotic) stress-tolerance mechanisms could provide a suitable evolutionary reasoning for the apparent dichotomy existing between the hyperaccumulators and AMF–plant life-history strategies. Ultimately, it is considered that any efforts toward integrating such biotechnology innovations into bioremediation strategies (e.g. ‘mycorrhizal–metal-hyperaccumulators’) should first explicitly consider their inherent environmental and (or) evolutionary contexts to avoid misleading and possibly even unproductive outcomes prior to incorporating these attributes as potential technological solutions.