Soil Arbuscular Mycorrhizal Fungi Research Articles

Importance and roles of arbuscular mycorrhizal fungi in new Caledonian ultramafic soils

ABSTRACT Our knowledge about New Caledonian serpentine ecosystems has increased greatly during the past half-century, mainly thanks to Jaffré’s group. However, research on soil microflora and plant symbionts started only in the nineties and was mainly published during the last two decades. We aim to synthesize these studies, focusing particularly on arbuscular mycorrhizal fungi (AMF). Research on AMF consists firstly of a global and inventory approach aiming to produce a basic but essential lacking knowledge. These studies showed that AMF are abundant in ultramafic soils and concerned nearly all plant species of these ecosystems. Even Ni-hyperaccumulator plants and sedges, generally considered non-mycorrhizal, were found to be functionally colonized by AMF in New Caledonian ultramafic soils. The adaptation of AMF communities to the extreme conditions of these soils led to high levels of metal tolerance (particularly to Ni) and noticeable originality of the taxa. The influence of these symbionts on plant growth and adaptation was assessed in greenhouse and field conditions. An accurate selection of AMF isolates that improve plant growth, and plant metal tolerance was performed. It was demonstrated that combinations of AMF isolates with complementary functional traits showed highly synergistic effects on plant development. Finally, a partnership with a biotechnological company led to the production of an efficient commercial inoculant now used in the ecological restoration of mine-degraded areas. Today studies are focused mainly on the additive effects of AMF and mycorrhiza-helper bacteria.

Assessment of Community Dynamics of Arbuscular Mycorrhizal Fungi in the Rice (Oryza sativa L.) Rhizosphere and Potential Application as Biofertilizer

Arbuscular mycorrhizal fungi (AMF) have the potential to maintain the sustainability of rice cultivation via maintaining soil health. The objective of this study was to produce an AMF-based biofertilizer for the rice variety Bg350 using indigenous dominant species of AMF that are adapted to paddy wetland soil conditions in dry, wet, and intermediate zones in Sri Lanka and are co-inoculated with the bacterium Azospirillum. A pot experiment was carried out to evaluate the effectiveness of the produced biofertilizer using the rice variety Bg350. Treatments were inorganic fertilizer, compost, biochar, produced AMF-biofertilizer [1 kg of ground carrier material inoculated with 50 g of AMF propagules and 20 mL of 1.5 × 108 (CFU/mL) of Azospirillum], and the control. A two-factor factorial, completely randomized design was used under sterilized and non-sterilized soil conditions with four replicates. The genera Glomus, Claroideoglomus, and Aculospora were identified as the most common AMFs in paddy soil in all investigated sites. In the 9th week of sampling, AMF root colonization was positively correlated (p = 0.028) with spore density. In Sri Lanka, for the first time, the highest AMF colonization rates in rice were recorded at 36.40% in the roots of the Bg350 from the Gampaha district. AMF root colonization increased over sampling time and was different according to the interactive effect of fertilizer application and soil condition. The biometric parameters and yield-attributing characteristics were significantly higher in the rice plants grown in sterilized soil, independent of the tested treatments. The number of grains per panicle was significantly similar (p ≤ 0.05) in the compost, AMF-biofertilizer, and inorganic fertilizer added treatments. It can be concluded that application of paddy soil adapted AMF species as a biofertilizer increased rice plant growth, productivity, and yield.

Biocontrol and plant growth promotion by combined Bacillus spp. inoculation affecting pathogen and AMF communities in the wheat rhizosphere at low salt stress conditions.

Applying plant growth-promoting rhizobacteria (PGPR) improves the efficiency of soil-borne disease control and is considered a sustainable practice. However, the effect of PGPR on the fungal community, especially pathogenic fungi and arbuscular mycorrhizal fungi (AMF), remains unclear. In this study, we examined the effects of a compound microbial agent (consisting of Bacillus subtilis HG-15 and Bacillus velezensis JC-K3) on the incidence and yield of wheat under low salt stress, as well as compared the diversity and community composition of the rhizosphere fungal and AMF communities of wheat in the CK (not inoculated bacterial agent) and BIO (inoculated with a bacterial agent) groups. Chlorophyll relative content (SPAD), net photosynthesis rate (Pn), transpiration rate (Tr), leaf water use efficiency (WUE L), grains per spike and wheat yield in the BIO group increased more than in the CK group. The number of diseased plants and disease incidence was observed to be reduced. The relative efficacy reached 79.80%. We classified 1007 fungal operational taxonomic units (OTU) based on Miseq sequencing data: 11 phyla, 173 families, 319 genera, and 521 species. Fifty-four OTUs were classified from the AMF effective sequences, including 1 phylum, 3 families, 3 genera, and 17 species. The inoculation of bacterial agents reduced the relative abundance of pathogen genera such as Gibberella, Fusarium, Cladosporium, and Alternaria in wheat rhizosphere. It increased the relative abundance of AMF species such as Glomus-group-B-Glomus-lamellosu-VTX00193, Glomus-viscosum-VTX00063, and Glomus-Glo2-VTX00280. In addition, pH, EC, exchangeable K, available N, total N, organic matter, and olsen P were the main driving forces for shaping wheat rhizosphere fungi. The pH value was positively correlated with the relative abundance of fungal communities in soil, especially Gibberella, Cladosporium, Fusarium, and Alternaria. In summary, inoculation with Bacillus subtilis HG-15 and Bacillus velezensis JC-K3 affected wheat yield, incidence, rhizosphere soil chemical properties, rhizosphere fungi, and AMF fungal diversity and community. The findings may provide a theoretical foundation and strain support for constructing efficient PGPR-community and clarifying its mechanism of pathogenic bacteria inhibition.

Impacts of Biogas Slurry Fertilization on Arbuscular Mycorrhizal Fungal Communities in the Rhizospheric Soil of Poplar Plantations.

The majority of terrestrial plants are symbiotic with arbuscular mycorrhizal fungi (AMF). Plants supply carbohydrates to microbes, whereas AMF provide plants with water and other necessary nutrients-most typically, phosphorus. Understanding the response of the AMF community structure to biogas slurry (BS) fertilization is of great significance for sustainable forest management. This study aimed to look into the effects of BS fertilization at different concentrations on AMF community structures in rhizospheric soil in poplar plantations. We found that different fertilization concentrations dramatically affected the diversity of AMF in the rhizospheric soil of the poplar plantations, and the treatment with a high BS concentration showed the highest Shannon diversity of AMF and OTU richness (Chao1). Further analyses revealed that Glomerales, as the predominant order, accounted for 36.2-42.7% of the AMF communities, and the relative abundance of Glomerales exhibited negligible changes with different BS fertilization concentrations, whereas the order Paraglomerales increased significantly in both the low- and high-concentration treatments in comparison with the control. Furthermore, the addition of BS drastically enhanced the relative abundance of the dominant genera, Glomus and Paraglomus. The application of BS could also distinguish the AMF community composition in the rhizospheric soil well. An RDA analysis indicated that the dominant genus Glomus was significantly positively correlated with nitrate reductase activity, while Paraglomus showed a significant positive correlation with available P. Overall, the findings suggest that adding BS fertilizer to poplar plantations can elevate the diversity of AMF communities in rhizospheric soil and the relative abundance of some critical genera that affect plant nutrient uptake.

Biostimulatory effect of vermicompost extract enhances soil mycorrhizal activity and selectively improves crop productivity

PurposeCommercial production and the use of liquid vermicompost extract (LVE) is gaining attention as a technique that supports integrated soil-microbial-crop management for sustainable agriculture. However, the interaction effects of LVE, arbuscular mycorrhizal fungi (AMF), and host plants on the delivery of agroecosystem services in alkaline soil have been less studied.MethodsWe carried out a 3-year field experiment in Central Italy, to investigate the short-term effect of LVE on soil mycorrhizal inoculum potential (MIP), AMF root colonization, and productivity of berseem clover, lentil, and sunflower. LVE produced in different years were screened for microbial properties using Illumina Miseq sequencing. LVE was applied at seeding, crop stem elongation and flowering stages. Control crops received water as a placebo.ResultsLVE bacterial communities were more diverse and showed a higher turnover between 2019 and 2020 than fungal communities. Diverse microbial groups, the majority of which belonged to phyla Proteobacteria, Bacteroidetes, Firmicutes, and Mucoromycota, were detected, including N-fixers (Flavobacterium, Malikia, and Citrobacter), P-solubilizers (Pseudomonas), and C-degraders (Tolumonas, Arcobacter, and Mucor). Notably, LVE treatment enhanced soil MIP and AMF root colonization in most crops, but selectively improved shoot biomass of berseem clover (+ 32%) and sunflower (+ 34%), and grain yield (+ 37%) and oil concentration (+ 5%) in sunflower, compared to the corresponding non-treated controls.ConclusionsLVE had diverse groups of bacteria and a few fungal taxa, and its application enhanced mycorrhizal properties and selected growth- and yield-related variables in lentil, berseem clover, and sunflower. This could be due to LVE’s biostimulating effect arising from the vermicompost-associated microbiome and biomolecules.

Arbuscular mycorrhizal fungi contribute to wheat yield in an agroforestry system with different tree ages.

Intercropping achieved through agroforestry is increasingly being recognized as a sustainable form of land use. In agroforestry, the roots of trees and crops are intermingled, and their interactions and the production of exudates alter the soil environment and soil microbial community. Although tree-crop interactions vary depending on the stand age of the trees, how stand age affects beneficial microorganisms, including arbuscular mycorrhizal fungi (AMF), and whether changes in soil microorganisms feed back on crop growth in agroforestry systems are unknown. We therefore conducted a long-term field study to compare changes in the soil microbial and AMF communities in a jujube/wheat agroforestry system containing trees of different stand ages: 3-year-old jujube, 8-year-old jujube, and 13-year-old jujube. Our results showed that by changing soil moisture and available phosphorus content, the stand age of the trees had a significant effect on the soil microbial and AMF communities. Soil moisture altered the composition of soil bacteria, in particular the proportions of Gram-positive and Gram-negative species, and available phosphorus had significant effects on the AMF community. A network analysis showed that older stands of trees reduced both AMF diversity and network complexity. An ordinary least squares regression analysis indicated that AMF diversity, network complexity, and stability contributed to wheat yield. Finally, structural equation modeling showed that changes in edaphic factors induced by tree age brought about significant variation in the soil microbial and AMF communities, in turn, affecting crop growth. Our study highlights the crucial roles of soil microorganisms, in particular AMF, in supporting plant growth in agroforestry systems as well as the need to consider stand age in the establishment of these systems.

Allelopathic Effects of Foliar Epichloë Endophytes on Belowground Arbuscular Mycorrhizal Fungi: A Meta-Analysis

Many grasses are simultaneously symbiotic with Epichloë fungal endophytes and arbuscular mycorrhizal fungi (AMF). Epichloë endophytes are a group of filamentous fungi that colonize and grow within aerial plant tissues, such as leaves and stems. Infection and hyphal growth of Epichloë endophytes confer fitness advantages to the host plants. In addition to producing fungal alkaloids and altering host metabolic/genetic profiles, it is proven that symbiosis of plants with root/foliar endophytes affects the plant–soil relationship. We propose that the Epichloë presence/infection results in variations of soil and root AMF through allelopathic effects. We performed a meta-analysis that integrated the allelopathic effects of Epichloë endophytes on grass–AMF development. In the pre-symbiotic phase of grass–AMF symbiosis, root exudation from Epichloë-infected plants positively affected AMF growth, whereas the shoot exudates of Epichloë-infected plants inhibited AMF growth. In the symbiotic phase of grass–AMF symbiosis, the Epichloë infection was found to reduce root mycorrhizal colonization in plants. No pattern in the response of soil AMF to Epichloë presence was found. This study should improve our understanding of the impact of Epichloë endophytes on belowground microbial symbionts within the same host plant. Grass–Epichloë–AMF symbiosis may become an important model for studying above–belowground interactions.

Genetic diversity and community composition of arbuscular mycorrhizal fungi associated with root and rhizosphere soil of the pioneer plant Pueraria phaseoloides.

The pioneering plant Pueraria phaseoloides had a strong modulation effect on arbuscular mycorrhizal fungi (AMF) communities. Irrespective of geographical location, community composition of AMF in rhizosphere soil differed from that of the root. Co-occurrence network analysis revealed two AMF keystone species in rhizosphere soil (Acaulospora) and roots (Rhizophagus) of P. phaseoloides.

Arbuscular Mycorrhizal Fungi in Sustainable Agriculture

The coevolution of mycorrhizae with plants represents a major evolutionary adaptation to the land environment. As a bioinoculant, arbuscular mycorrhizal fungi (AMF) play a beneficial role in sustainable agriculture by symbiotically associating with many crop plants. In this review, we primarily focus on the nutritional and non-nutritional functionality of AMF in soil and plant productivity. AMF maintain soil quality and health via three aspects: soil structure, plant physiology, and ecological interactions. These lead plants to increase their functionality, further growth, and productivity. The formation of soil aggregates via glomalin production maintains the soil structure. Physiologically, AMF change nutrient acquisition and thereby increase soil fertility and productivity. Biotic (pathogens and weed plants) and abiotic (salinity, drought, extreme temperature, soil pH, and heavy metals) stress alleviation is also achieved via altering a plant’s physiological status. By serving as a biocontrol agent, AMF negatively interact with plant pathogens. As a result of beneficial interactions with other rhizosphere microorganisms and above-ground organisms, AMF induce a synergistic effect on plant performance. Moreover, they are also involved in land restoration and seedling establishment. The collective effect of all these functions positively influences overall plant performance and productivity.

Positive feedback between peanut and arbuscular mycorrhizal fungi with the application of hairy vetch in Ultisol.

Multiple agricultural practices are being applied to increase crop yield in order to overcome the food shortage. Green manure has emerged as an appropriate practice to improve soil fertility and crop yield. However, the potential functions of arbuscular mycorrhizal fungi (AMF) in the below-ground ecosystems following the application of green manure in Ultisols remain largely unexplored. In this study, qPCR and high-throughput sequencing were used to investigate the response of AMF abundance and communities in different treatment groups, i.e., control (without fertilization), mineral fertilization (NPK), mineral fertilization with returning peanut straw (NPKS), and with green manure (hairy vetch; NPKG). The NPKG treatment significantly increased soil fertility compared to other treatment groups. Compared with control, the NPK, NPKS, and NPKG treatments increased peanut yield by 12.3, 13.1, and 25.4%, respectively. NPKS and NPKG treatments significantly altered the AMF community composition decreased the AMF diversity and increased AMF abundance compared to the control. The AMF network of the NPKG treatment group showed the highest complexity and stability compared to other treatment groups. The structural equation modeling revealed that the application of hairy vetch improved soil nutrients and peanut yield by increasing the soil AMF abundance and network stability. Overall, the results suggested that the application of hairy vetch might trigger positive feedback between the peanut and AMF community, contributing to fertility and yield improvement in the dryland of Ultisol.

Rehabilitation promotes rapid recovery of arbuscular mycorrhizal fungi in iron mining areas

Arbuscular mycorrhizal fungi (AMF) perform important ecological functions in the rehabilitation of degraded areas, acting through several mechanisms, such as the production of glomalin-related soil proteins (glomalin), which act as cementing agents and nutritional reserves and sequester carbon in soil. The aim of the present study was to determine whether a short rehabilitation time influenced the soil AMF community diversity and glomalin production in areas undergoing rehabilitation after iron mining. We analyzed the number of spores, mycorrhizal colonization, AMF species richness, and concentrations of easily extractable and total glomalin-related soil proteins. Species richness was reduced by approximately 50 % after mining activity. However, after the initial rehabilitation of degraded areas, we observed an increase in the number of spores, colonization, and AMF species. Families Glomeraceae and Acaulosporaceae were considered dominant in the studied areas. Glomus sp.1 and Acaulospora mellea were the most frequent morphotypes. The relationship between glomalin and the levels of dissolved organic carbon, total carbon, and total nitrogen in the soil was found to be an interesting and easily interpretable parameter of the influence of AMF on the storage of organic matter in the soil, indicating the degree of equilibrium and/or recovery of revegetated environments. Rehabilitation, even in early stages, favored improvements in AMF status and provided increases in total glomalin-related soil protein production, which may have contributed to the enrichment of carbon and nitrogen in the soil. These characteristics are indicative of the success of the rehabilitation actions carried out in these areas after mining activity.

Effects of grass cultivation on soil arbuscular mycorrhizal fungi community in a tangerine orchard

Grass co-cultivation has been widely adopted to increase fruit quality by improving soil fertility. However, the response characteristics of soil arbuscular mycorrhizal fungi (AMF) community in tangerine orchards under grass co-cultivation environments is still poorly understood. Therefore, in order to reveal the effects of the co-cultivation of different grasses in tangerine orchards on the community structure and diversity of rhizospheric arbuscular mycorrhizal fungi (AMF), as well as soil properties, a 10 year study was undertaken at a tangerine orchard with four treatments: sod cultures with either white clover, ryegrass, natural grass or clear tillage as the control. The results showed that grass co-cultivation increased soil nutrient contents and AMF community richness, but had no significant effect on AMF community diversity (P > 0.05). The AMF detected in all soil samples belonged to one phylum, three classes, four orders, five families and five genera. The composition and structure of the AMF community varied among four treatments. Redundancy analysis (RDA) revealed that ​soil physicochemical properties impacted variations in the AMF community characteristics diversely. Furthermore, network analysis showed that grass co-cultivation increased the scale and complexity of the microbial co-occurrence network. In summary, grass co-cultivation in tangerine orchards not only improved soil fertility and soil structure, but also improved the stability and stress resistance of soil AMF community, which is conducive to promoting the sustainable development of the tangerine industry.

Experimental assessment of forest floor geophyte and hemicryptophyte impact on arbuscular mycorrhizal fungi communities

PurposeHerbaceous plants are important components of temperate forest structure and its functioning, however, their impacts on arbuscular mycorrhizal fungi (AMF) remain largely unexplored. We studied the influence of forest herbaceous plant species on AMF abundance, morphospecies richness, and community composition in soil.MethodsWe tested the influence of plant species identity in an outdoor mesocosm experiment, using two soils, differing in physicochemical properties, planted with four plant species of contrasting traits related to morphology, phenology, reproduction, and ecology; the hemicryptophyte, summer-green Aegopodium podagraria, and spring ephemeral geophytes comprising Allium ursinum, Anemone nemorosa, and Ficaria verna. The plants were grown on both soils in four monocultures, in a combination of A. podagraria and A. ursinum, and a mixture of all four species.ResultsAegopodium podagraria and A. ursinum promoted AMF abundance and diversity the most. Higher AMF root colonization and/or soil concentrations of AMF structural and storage markers 16:1ω5 PLFA and NLFA, as well as higher AMF spore and morphospecies numbers were found in the A. podagraria and A. ursinum monocultures and mixture. The short period of photosynthetic activity of A. ursinum due to rapid leaf decay does not negatively affect the symbiosis with AMF. Although A. nemorosa and F. verna are mycorrhizal, their effect on AMF in soil was weak.ConclusionsThe plant impact on AMF may be related to the differences in plant coverage and the character of their interactions with AMF. The herbaceous plants can form niches in soil differing in AMF abundance and diversity.

Long-term phosphorus addition inhibits phosphorus transformations involved in soil arbuscular mycorrhizal fungi and acid phosphatase in two tropical rainforests

Increasing atmospheric nitrogen (N) and phosphorus (P) deposition affect soil nutrient availability and biogeochemical cycles, yet the impacts on the regulatory processes of soil P in P-poor tropical rainforests are not well understood. Based on a ten-year N and P addition experiment in primary and secondary rainforests in Hainan, China, we investigated the effects of N and P additions on four soil P fractions, acid phosphatase (ACP) activity, kinetic characteristics and arbuscular mycorrhizal (AM) diversity. Our results showed that P addition significantly increased soil available P (AP), but had no significant effects on microbial P and microbial N:P ratio in both rainforests. Late-successional primary rainforest had higher microbial P and lower N:P ratio compared to early-successional secondary rainforest, suggesting that forest succession would not aggravate microbial P limitation. Plants and microorganisms accessed most inorganic P by releasing hydrion and organic acids to mobilize soil P, whereas inorganic P accessed by root interception and organic P readily mineralized by ACP and phytase enzymes were relatively low. In the primary rainforest, ACP and kinetic parameters were significantly increased under low N addition, while P addition remarkedly declined ACP activity and AM diversity in both rainforests. Additionally, CaCl2 extractable P, citrate extractable P, and HCl extractable P in the two forests were significantly positively associated with soil AP, but negatively associated with ACP activity, kinetic parameters and AM diversity. Therefore, the transformations of organic P were inhibited after the exogenous addition of inorganic P. Overall, our study evaluates the soil P acquisition strategies and regulatory processes in tropical rainforests with different successional stages, which can be used to predict the effects of long-term N and P deposition on soil P cycling in P-poor tropical rainforests.

Application of dry olive residue-based biochar in combination with arbuscular mycorrhizal fungi enhances the microbial status of metal contaminated soils

Biochar made-up of dry olive residue (DOR), a biomass resulting from the olive oil extraction industry, has been proposed to be used as a reclamation agent for the recovery of metal contaminated soils. The aim of the present study was to investigate whether the soil application of DOR-based biochar alone or in combination with arbuscular mycorrhizal fungi (AMF) leads to an enhancement in the functionality and abundance of microbial communities inhabiting metal contaminated soils. To study that, a greenhouse microcosm experiment was carried out, where the effect of the factors (i) soil application of DOR-based biochar, (ii) biochar pyrolysis temperature (considering the variants 350 and 500 °C), (iii) soil application dose of biochar (2 and 5%), (iv) soil contamination level (slightly, moderately and highly polluted), (v) soil treatment time (30, 60 and 90 days) and (vi) soil inoculation with Funneliformis mosseae (AM fungus) on β-glucosidase and dehydrogenase activities, FA (fatty acid)-based abundance of soil microbial communities, soil glomalin content and AMF root colonization rates of the wheat plants growing in each microcosm were evaluated. Biochar soil amendment did not stimulate enzyme activities but increased microbial abundances. Dehydrogenase activity and microbial abundances were found to be higher in less contaminated soils and at shorter treatment times. Biochar pyrolysis temperature and application dose differently affected enzyme activities, but while the first factor did not have a significant effect on glucosidase and dehydrogenase, a higher biochar dose resulted in boosted microbial abundances. Soil inoculation with F. mosseae favored the proliferation of soil AMF community and increased soil glomalin content as well as rates of AMF root colonization. This factor also interacted with many of the others evaluated to significantly affect soil enzyme activities, microbial abundances and AMF community. Our results indicate that the application of DOR-based biochar along with AMF fungi is an appropriate approach to improve the status of microbial communities in soils with a moderate metal contamination at short-term.

Agricultural management and pesticide use reduce the functioning of beneficial plant symbionts.

Phosphorus (P) acquisition is key for plant growth. Arbuscular mycorrhizal fungi (AMF) help plants acquire P from soil. Understanding which factors drive AMF-supported nutrient uptake is essential to develop more sustainable agroecosystems. Here, we collected soils from 150 cereal fields and 60 non-cropped grassland sites across a 3,000 km trans-European gradient. In a greenhouse experiment, we tested the ability of AMF in these soils to forage for the radioisotope 33P from a hyphal compartment. AMF communities in grassland soils were much more efficient in acquiring 33P and transferred 64% more 33P to plants compared to AMF in cropland soils. Fungicide application best explained hyphal 33P transfer in cropland soils. The use of fungicides and subsequent decline in AMF richness in croplands reduced 33P uptake by 43%. Our results suggest that land-use intensity and fungicide use are major deterrents to the functioning and natural nutrient uptake capacity of AMF in agroecosystems.

Forest density and edge effects on soil microbial communities in deciduous forests across Europe

Forest fragmentation increases the proportion of edge area and this, in turn, induces changes in forest structure, species composition and microclimate. These factors are also strongly determined by the forest management regime. Although the interactive effects of edges and density on forest plant communities have been extensively studied, little is known about the response of the belowground communities. Here we investigated the variation of soil microbiota in 45 deciduous broadleaved forests along a latitudinal gradient from Italy to Norway at a continental scale across Europe. Phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) were used to map the microbial community in the forest edge and interior across three forest densities (dense, intermediate, open forest). Microbial community composition was only affected by forest edge effects and not by forest density. We did not find any interaction effects between forest density and distance-to-edge. Arbuscular mycorrhizal fungi (AMF) were significantly more abundant in edges and Gram-negative bacteria more abundant in interiors, respectively. The microbial community composition was closely related to soil pH, soil potassium and nitrogen, texture (percent sand) and soil temperature. Soil pH was positively correlated with the saprotrophic fungi and potassium was positively correlated with Gram-negative bacteria but negatively correlated with Actinobacteria. In sum, we reveal the notable effects of forest edges on the soil AMF abundance. This result indicated that AMF could possess a stronger affinity with species growing in the edges, which may help to improve plant performance under hostile conditions herein.

Arbuscular Mycorrhizal Fungi and Soil Quality Indicators in Eucalyptus genotypes With Different Drought Tolerance Levels.

Silviculture has great importance worldwide, and the use of Eucalyptus species, which account for 75% of the local planted forest in Brazil, is one of the factors that contributes to the success of this activity in the country. Despite its adaptability, the yield of Eucalyptus is often affected by climate change, particularly water deficiency. Plants have developed strategies to mitigate water stress, for example, through their association with mycorrhizal fungi. The genus Eucalyptus, particularly in the plant domain, establishes symbioses with arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (ECMF). The influence of Eucalyptus species on AMF and soil quality indicators is not well understood. Our aim was to conduct a preliminary evaluation of the various responses of soil AMF communities and soil nutrient dynamics in the presence of Eucalyptus species with different degrees of drought tolerance. A field experiment was established containing six Eucalyptus species, E. brassiana, E. camaldulensis, E. citriodora, E. cloeziana, E. grandis, and E. urophylla, all of which were planted in large plots. Soil and root samples were taken when the plants were 1.7 and 2.2 years old. We found that Eucalyptus species with low (E. grandis and E. urophylla) and intermediate drought tolerance (E. citriodora and E. cloeziana) showed stronger correlations with the AMF community than Eucalyptus species with high drought tolerance (E. brassiana and E. camaldulensis). Differences were also found between Eucalyptus species for AMF spore numbers and root colonization percentages, which was most evident for E. urophylla. The microbiological attributes found to be most responsive to Eucalyptus species were soil enzyme activities, AMF spore numbers, root colonization percentages, and fungal abundance. Soil organic carbon, phosphorus, potassium, zinc, copper, and iron were the main chemical drivers related to the soil AMF community structure in the presence of E. brassiana.

Effects of no-tillage and biologically-based organic fertilizer on soil arbuscular mycorrhizal fungal communities in winter wheat field

Communities of arbuscular mycorrhizal fungi (AMF) in soil are impacted by agricultural management, which in turn influences crop growth and yield. Yet the combined effects of tillage and fertilization practices upon AMF communities are still poorly understood. This study investigated the interactive effects of tillage (no-tillage and conventional tillage) and fertilization (no-fertilization and biologically based organic fertilization) factors on AMF community structure and yield of winter wheat field. The five-year field experiment was conducted in Longde County, Ningxia, China. Results indicated that no-tillage significantly increased the species richness, evenness, and diversity of soil AMF, whereas bio-organic fertilization was less influential. Under no-tillage, bio-organic fertilization marginally increased the richness and diversity of AMF species; however, under conventional tillage this effect was inversed. Glomus, Claroideoglomus, and Paraglomus AMF genera dominated under no-tillage combined with bio-organic fertilization. No-tillage increased the relative abundance of Glomus, while bio-organic fertilization increased that of Claroideoglomus. Redundancy analysis revealed that total nitrogen and available phosphorus were the most important soil variables related to the diversity and community composition of AMF. The yield of winter wheat was negatively correlated with AMF diversity and positively correlated with Glomus abundance. This study suggests that, compared to single conservation agricultural practices, combining no-tillage with bio-organic fertilization may further improve the benefits of soil AMF for winter wheat crops. However, under low nitrogen and phosphorus inputs, conventional tillage can accelerate the mineralization of organic matter and increase the availability of soil nutrients, thereby improving wheat yield.

Higher diversity and contribution of soil arbuscular mycorrhizal fungi at an optimal P-input level

As not only an indicator but also key determinants of soil health, the performance of arbuscular mycorrhizal (AM) fungi under intensive cropping systems remains incompletely understood, particularly with regard to quantitative contributions to crop phosphorus (P) acquisition and scientific managements of P-input levels. Here, we firstly investigated the diversity and vitality of AM fungi along with decreasing P-input levels from P100 (local regular rate) to P50 (50 % off) in a greenhouse experiment to explore the optimal P-input level, and further determined the apparent contribution of AM fungi to maize (Zea mays L.) P acquisition at optimal level in a field microplot experiment with root mycorrhization inhibition by benomyl application and in another pot experiment upon AM fungal inoculation in a sterilized soil. Decreasing P input decreased the amount but increased the efficiency of plant P acquisition, and increased the diversity and colonization of AM fungi, in addition to shaping the community composition. Notably, P80 (20 % off) appeared to be an optimal level that balanced mycorrhizal vitality, maize growth and P-acquisition efficiency. The apparent contribution of AM fungi to maize P acquisition determined in both field and pot experiments were approximately 36 % and 21 % at P80 and P100, respectively, while grain yields at P80 with mycorrhizae reached the level equivalent to that of P100 without mycorrhizae, indicating a replacement of 20 % of P fertilizers by adequate mycorrhizal management. It highlights that stronger AM associations by optimizing P input allow for relatively high crop P-acquisition efficiency upon high mycorrhizal benefits, favoring agricultural production in a sustainable manner with reduced dependence on inputs.