Hyphae Of Arbuscular Mycorrhizal Fungi Research Articles

Arbuscular mycorrhizal fungi reduce N2O emissions from degraded residue patches

Nitrous oxide (N2O) is a potent greenhouse gas, and agricultural soils represent a major anthropogenic source. Crop residues provide nutrients for plants but also act as hotspots of N2O production. The hyphae of arbuscular mycorrhizal fungi (AMF) could proliferate in organic patches, utilize released N from the organic patches, and potentially mitigate N2O emissions. However, the effect of AMF on N2O emissions in degraded residue patches and the possible microbial mechanism remain uncertain. Here, a mesocosm experiment was conducted to investigate the impact of AMF (Funneliformis mosseae) inoculation on N2O emissions, availabilities of carbon and nitrogen, extracellular enzyme activities, and the abundance of key N-cycling genes in degraded residue patches. Our results showed that AMF hyphae significantly reduced N2O emissions from degraded residue patches. Quantitative PCR analysis of key functional genes involved in N2O production (amoA, nirK, nirS) and consumption (nosZ) showed that AMF significantly reduced the abundance of the bacterial amoA and nirS genes. NH4+, NO3−, total dissolved nitrogen (TDN), total nitrogen (TN), and dissolved organic carbon (DOC) contents decreased drastically in the presence of AMF. In addition, the activities of all tested extracellular enzymes were significantly decreased by AMF and positively correlated with DOC content. Multiple stepwise regression analysis demonstrated that the abundance of the nirS gene primarily influenced N2O emissions and was positively correlated with DOC content in degraded residue patches. Our findings indicate that AMF suppressed N2O producers, particularly nirS-type denitrifiers, by slowing down the release of C and N from degraded residues, thereby leading to a cascade effect on the decrease of N2O emissions. This study provides a promising approach to mitigate N2O emissions by enhancing AMF in the agroecosystems.

Multiple facets of cutting-edge mycorrhizal research: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, August 2022: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, 1-5 August 2022.

Multiple facets of cutting-edge mycorrhizal research: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, August 2022: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, 1-5 August 2022.

Arbuscular mycorrhizal fungi and common mycorrhizal networks benefit plants through morphological, physiological and productive traits and soil quality

The extraradical hyphae of arbuscular mycorrhizal fungi (AMF) of one plant root system forage for the soil nutrients and induce the root colonization of the nearby plants, which leads to the formation of common mycorrhizal networks (CMNs) that interconnect roots. Inoculation with AMF can increase the root length, surface area and volume of seedlings in nutrient-limited karstic soils. Mycorrhizal symbioses can secrete glomalin to help promoting soil aggregates for water and nutrients storage, through an extended hyphae to absorb water and nutrients from long distances. AMF can boost rhizosphere soil enzyme activities, and may help to drive carbon sequestration. AMF also improve plant growth by advancing soil quality through influencing its structure and texture. As a result, AMF and CMNs benefit plants through improving soil quality and enhancing morphological (e.g., hyphal length, tillering, number of stolons per individual), physiological (e.g., water use efficiency) and productive (e.g., fresh and dry shoot and root weights) traits.

Parasitic plants indirectly regulate decomposition of soil organic matter

Abstract Parasitic plants have been shown to affect soil‐organic‐matter (SOM) decomposition, but the mechanism is unknown. As arbuscular mycorrhizal fungi (AMF) can affect decomposition and compete with parasitic plants for carbon, we hypothesized that parasitic plants can indirectly regulate SOM decomposition by suppressing the effects of AMF on decomposition. To test this hypothesis, we conducted two container experiments in which the herbaceous plant Bidens pilosa was inoculated with the AMF Rhizophagus intraradices or not, and Cuscuta australis or not. In one experiment, we provided SOM within hyphae‐in‐growth bags as 13C‐/15 N‐labelled maize leaves and in the other experiment as phytate‐P. We assessed growth and nutrient uptake of B. pilosa, growth of C. australis, the SOM remaining in the hyphae‐in‐growth bags, and the bacterial communities. Parasitization increased the 13C and decreased the organic P remaining in the bags, but only in the presence of the extraradical AMF hyphae. AMF decreased the 13C and increased the organic P remaining in the absence of the parasite, but not in the presence of the parasite. Our results demonstrate that parasitic plants can regulate the decomposition of organic materials indirectly by suppressing the effect of the extraradical AMF hyphae on decomposition. In other words, parasitic plants can regulate SOM decomposition indirectly via a multitrophic cascading effect. Our study helps to unravel the mechanisms of a sophisticated hidden ecological process, and is an important step forward in elucidating the roles of parasitic plants in soil nutrient cycling. Read the free Plain Language Summary for this article on the Journal blog.

Pb Transfer Preference of Arbuscular Mycorrhizal Fungus Rhizophagus irregularis in Morus alba under Different Light Intensities.

Arbuscular mycorrhizal (AM) fungi can improve the lead (Pb) tolerance of host plants and accumulate intensive Pb in mycorrhizal roots. However, the detailed contribution of AM fungal extraradical hyphae to the plants' Pb uptake remains unknown. In this study, mulberry (Morus alba) colonized by the AM fungus (Rhizophagus irregularis) with light treatments were linked by fungal extraradical hyphae using a three-compartment system (pot test), and their differences in responding to Pb application were compared. Shading inhibited mulberry photosynthesis and the growth of mulberry. In this study, Pb application did not affect the colonization of R. irregularis when symbiosis had already formed as the root was not exposed to Pb during the colonization and formation of the AM fungal hyphae network. The R. irregularis preferred to transfer more Pb to the unshaded mulberry than to the shaded mulberry, a condition capable of providing more C supply for fungal survival than to low-light mulberry. The Pb transferred through the mycorrhizal pathway to mulberry had low mobility and might be compartmented in the root by R. irregularis until exceeding a threshold. The relatively high expressions of MaABCG16 with high Pb concentrations in plants suggest that MaABCG16 might play an important role in Pb translocation.

Dynamics of fungal community structure in a silver birch (Betula pendula Roth) succession chronosequence on poor-quality post-arable soil

Soil fungal communities are critical components in soil ecosystems, but experimental researches on their responses to the silver birch succession are limited. Arbuscular mycorrhizal (AM) fungi and glomalin-related soil protein (GRSP) – a type of glycoprotein produced by hyphae of AM fungi, are highly correlated with soil physicochemical parameters and are sensitive to changes in the soil environment. This study aimed to analyze the dynamics of a soil fungal community, with particular emphasis on the AM fungi and GRSP contents and their responses to a silver birch succession on abandoned post-arable land. The studies were conducted in central Poland and covered five stands that included arable field (AF) and fallow (FA) land, and 8-year-old/young (YS), 33-year-old/middle (MS), and 40-year-old/old (OS) successions of silver birch. The diversity and compositions of the fungal communities were examined using ITS high-throughput gene sequencing. We found that the dominant soil fungal phylum transitioned from Olpidiomycota through Ascomycota to Basidiomycota with the change from AF to OS. Silver birch development increased the soil fungal diversity and richness compared with that of the AF soil, but these decreased compared with the FA soil. The predominant fungi in the soils under silver birch development belonged to the families Pezizaceae, Russulaceae, and Cortinariceae. The birch succession significantly decreased the abundance of potential pathotrophs and increased the relative abundance of symbiotrophic fungi. The AM fungi abundance varied across the successional stages and was affected by plant cover and N content, and positively correlated with the EE-GRSP and T-GRSP contents. Additionally, the EE-GRSP and T-GRSP contents positively correlated with the TOC, N and SOM content, and Tp, and negatively correlated with Bd. Across the successional stages, the YS was devoid of AM fungi and characterized by the lowest EE-GRSP T-GRSP (1.89 mg g-1), Tp (43.4%), and TOC (7.3 g kg-1) and P (11.7 g kg-1) contents. In summary, the development of young silver birch on generally poor Brunic Arenosols tends to have a negative effect on the soil fungal community and selected soil properties, but these effects ease over time.

Arbuscular mycorrhizal hyphal respiration makes a large contribution to soil respiration in a subtropical forest under various N input rates

Arbuscular mycorrhizal fungi (AMF) are widespread in subtropical forests and play a crucial role in belowground carbon (C) dynamics. Nitrogen (N) deposition or fertilization may affect AMF and thus the flux of plant-derived C back to the atmosphere via AMF hyphae. However, the contribution of AMF hyphal respiration to soil respiration and the response AMF hyphal respiration to increased soil N availability remain unknown. We studied the effect of N fertilization (0, 50, 100 and 200 kg N ha−1 yr−1) on AMF hyphal respiration, root respiration and heterotrophic (microbial) respiration in a subtropical Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantation. We found that short-term N addition did not affect root, AMF hyphal and soil microbial respiration, because soil N availability and extraradical hyphae were not affected by N addition. The AMF hyphal respiration contributed 12 % of total soil respiration and 25 % of the autotrophic respiration. Root, AMF hyphal and soil microbial respiration were positively correlated with soil moisture content but not with soil temperature. Our results indicate that AMF hyphal respiration is a large source of soil respiration, and should be considered in partitioning soil respiration into different components in future studies to better understand the response of soil respiration to N addition.

Suppression of AMF accelerates N2O emission by altering soil bacterial community and genes abundance under varied precipitation conditions in a semiarid grassland.

Nitrous oxide (N2O) is one of the most important greenhouse gases contributing to global climate warming. Recently, studies have shown that arbuscular mycorrhizal fungi (AMF) could reduce N2O emissions in terrestrial ecosystems; however, the microbial mechanisms of how AMF reduces N2O emissions under climate change are still not well understood. We tested the influence of AMF on N2O emissions by setting up a gradient of precipitation intensity (+50%, +30%, ambient (0%), −30%, −50%, and −70%) and manipulating the presence or exclusion of AMF hyphae in a semiarid grassland located in northeast China. Our results showed that N2O fluxes dramatically declined with the decrease in precipitation gradient during the peak growing season (June–August) in both 2019 and 2020. There was a significantly positive correlation between soil water content and N2O fluxes. Interestingly, N2O fluxes significantly decreased when AMF were present compared to when they were absent under all precipitation conditions. The contribution of AMF to mitigate N2O emission increased gradually with decreasing precipitation magnitudes, but no contribution in the severe drought (−70%). AMF significantly reduced the soil’s available nitrogen concentration and altered the composition of the soil bacteria community including those associated with N2O production. Hyphal length density was negatively correlated with the copy numbers of key genes for N2O production (nirK and nirS) and positively correlated with the copy numbers of key genes for N2O consumption (nosZ). Our results highlight that AMF would reduce the soil N2O emission under precipitation variability in a temperate grassland except for extreme drought.

Calling for comprehensive explorations between soil invertebrates and arbuscular mycorrhizas.

Arbuscular mycorrhizal (AM) fungi and soil invertebrates represent a large proportion of total soil biomass and biodiversity and are vital for plant performance, soil structure, and biogeochemical cycling. However, the role of soil invertebrates in AM fungi development remains elusive. In this opinion article, we summarize the ecological importance of AM fungi and soil invertebrates in the plant-soil continuum and highlight the effects of soil invertebrates on AM fungal hyphae development and functioning. In a context of global change, we envision that better mechanistic understanding of the complex feedback via chemical signaling pathways across the interactions between soil invertebrates and AM fungi is critical to predict their ecological consequences and will open new avenues for promoting ecosystem resilience and sustainability.

In Vitro Propagation of A Cuban Arbuscular Mycorrhizal Fungal Strain

In vitro root cultivation techniques based on modified root systems are often used in studies on Arbuscular Mycorrhizal Fungi (AMF). It is a simplified but powerful tool to investigate AMF root colonization and development of the extraradical mycelium. The aim of this study was to establish and characterize the in vitro culture of a Cuban strain of Rhizophagus irregularis (INCAM 11) by using transformed chicory roots. For that, superficially disinfected propagules of R. irregularis were co-culture with the hairy transformed chicory roots on Modified Strullu and Romand (MSR) medium during five months. Spore germination was observed 3-5 days after surface disinfection. The first contact between AMF hyphae and roots occurred 1-3 days after germination and a significant production of extensive extraradical mycelium was observed. New spore formation started within 21-25 days. After 5 months, 2000 spores could be observed per plate which were able to germinate, colonize, establish and reproduce again spores when associated to young transformed roots of chicory. The most frequent associated microorganism to the in vitro culture of INCAM 11 was isolated and identified as Paenibacillus sp.

Recreating in vitro tripartite mycorrhizal associations through functional bacterial biofilms.

Arbuscular mycorrhizal fungi (AMF) and beneficial bacteria are found naturally associated with most terrestrial plant roots. While it is now well known that bacteria colonize AMF and can form aggregates and biofilms, little is known about how interactions between bacterial communities and AMF take place under both in situ and in vitro conditions. We investigated the impact of inoculation with AMF-associated bacteria (AABs) of AMF by in vitro recreation of the interaction on synthetic growth media in a two-compartment Petri plate system. The inoculated AABs were found to be associated with the mycorrhizal co-culture and were found to migrate along growing AMF hyphae and to be associated with the spore surface. AABs differentially influenced the growth of the AMF and their functional capability demonstrated by analysis of phosphate solubilization, nitrogen fixation, and biofilm formation. We have thus characterized these important interactions adding to a further understanding of the synergistic relationship between the two cross-kingdom microbial partners. KEY POINTS: • An in vitro assay was utilized to recreate functional biofilms with AMF-associated bacteria. • AMF-associated bacteria formed a biofilm and enhanced sporulation of Rhizophagus irregularis. • AMF-bacterial interactions through biofilm formation influence the functional capability of both partners.

Arbuscular mycorrhizal fungi conducting the hyphosphere bacterial orchestra.

More than two-thirds of terrestrial plants acquire nutrients by forming a symbiosis with arbuscular mycorrhizal (AM) fungi. AM fungal hyphae recruit distinct microbes into their hyphosphere, the narrow region of soil influenced by hyphal exudates. They thereby shape this so-called second genome of AM fungi, which significantly contributes to nutrient mobilization and turnover. We summarize current insights into characteristics of the hyphosphere microbiome and the role of hyphal exudates on orchestrating its composition. The hyphal exudates not only contain carbon-rich compounds but also promote bacterial growth and activity and influence the microbial community structure. These effects lead to shifts in function and cause changes in organic nutrient cycling, making the hyphosphere a unique and largely overlooked functional zone in ecosystems.

Nitrogen fertilisation disrupts the temporal dynamics of arbuscular mycorrhizal fungal hyphae but not spore density and community composition in a wheat field.

Elucidating the temporal dynamics of arbuscular mycorrhizal (AM) fungi is critical for understanding their functions. Furthermore, research investigating the temporal dynamics of AM fungi in response to agricultural practices remains in its infancy. We investigated the effect of nitrogen fertilisation and watering reduction on the temporal dynamics of AM fungi, across the lifespan of wheat. Nitrogen fertilisation decreased AM fungal spore density (SD), extraradical hyphal density (ERHD), and intraradical colonisation rate (IRCR) in both watering conditions. Nitrogen fertilisation affected AM fungal community composition in soil but not in roots, regardless of watering conditions. The temporal analysis revealed that AM fungal ERHD and IRCR were higher under conventional watering and lower under reduced watering in March than in other growth stages at low (≤ 70 kg N ha-1 yr-1 ) but not at high (≥ 140) nitrogen fertilisation levels. AM fungal SD was lower in June than in other growth stages and community composition varied with plant development at all nitrogen fertilisation levels, regardless of watering conditions. This study demonstrates that high nitrogen fertilisation levels disrupt the temporal dynamics of AM fungal hyphal growth but not sporulation and community composition.

Multimodal correlative imaging and modelling of phosphorus uptake from soil by hyphae of mycorrhizal fungi.

Summary Phosphorus (P) is essential for plant growth. Arbuscular mycorrhizal fungi (AMF) aid its uptake by acquiring P from sources distant from roots in return for carbon. Little is known about how AMF colonise soil pore‐space, and models of AMF‐enhanced P‐uptake are poorly validated.We used synchrotron X‐ray computed tomography to visualize mycorrhizas in soil and synchrotron X‐ray fluorescence/X‐ray absorption near edge structure (XRF/XANES) elemental mapping for P, sulphur (S) and aluminium (Al) in combination with modelling.We found that AMF inoculation had a suppressive effect on colonisation by other soil fungi and identified differences in structure and growth rate between hyphae of AMF and nonmycorrhizal fungi. Our results showed that AMF co‐locate with areas of high P and low Al, and preferentially associate with organic‐type P species over Al‐rich inorganic P.We discovered that AMF avoid Al‐rich areas as a source of P. Sulphur‐rich regions were found to be correlated with higher hyphal density and an increased organic‐associated P‐pool, whilst oxidized S‐species were found close to AMF hyphae. Increased S oxidation close to AMF suggested the observed changes were microbiome‐related. Our experimentally‐validated model led to an estimate of P‐uptake by AMF hyphae that is an order of magnitude lower than rates previously estimated – a result with significant implications for the modelling of plant–soil–AMF interactions.

Indigenous arbuscular mycorrhizal fungi play a role in phosphorus depletion in organic manure amended high fertility soil

The species richness and propagule number of arbuscular mycorrhizal fungi (AMF) are high in intensively-managed agricultural soils. Past research has shown that AMF improve crop phosphorus (P) uptake under low soil P conditions, however it is unclear if AMF play a role in high Olsen-P soils. In this study, we investigated whether native fungal benefits exist under high P input field conditions in-situ and contribute to P utilization. We installed in-grow tubes which were sealed with different membrane pore sizes (30 or 0.45 μm) to allow or prevent AMF hyphae access to the hyphal compartment and prevent cotton roots from penetrating the chamber. We used the depletion of soil available P (Olsen-P) in the hyphae accessed compartment to indicate P uptake by the native AMF community. Our results showed that the native AMF mediated P depletion and microbial biomass P (MBP) turnover and caused the largest Olsen-P depletion ratio and MBP turnover ratio in the high P treatments (Olsen-P: 78.29 mg kg−1). The cotton roots in each fertilization regime were colonized by a unique AMF community and Glomus and Paraglomus were the dominant genera, implying the long-term fertilization regimes domesticated the AMF community. We conclude that native AMF caused the P depletion and P turnover even under high soil Olsen-P conditions.

Impact of salinity and phosphorus on growth of Phaseolus Vulgaris inoculated with Arbuscular Mycorrhizal Fungi

As the supply of rock phosphate decreases, it is essential that the agriculture industry reduces wasteful phosphorus (P) fertilizer application by improving crop acquisition of P. Arbuscular mycorrhizal fungi (AMF), a fungus that forms a beneficial relationship with many crops, is one potential solution to this problem. Numerous studies show that crops inoculated with AMF have many benefits such as increased P uptake, resulting in higher yield and resistance to abiotic stresses. The objective of this study was to understand the impact of mycorrhizal symbiosis on bean growth under varying soil conditions of P and salinity. We tested several P concentrations and salinity levels and found that beans planted in soil conditions containing the highest levels of P and salinity exhibited significantly lower root-to-shoot ratios than any other trials while still maintaining similar biomass weight. This suggests that AMF hyphae increased the affinity of the plant for absorbing nutrients, allowing it to focus on shoot growth instead of root growth. We also observed that adding more P fertilizer to the AMF-inoculated bean plants both under salt and non-salt conditions led to diminishing returns in terms of plant height and dry weight. Hence, adding more P fertilizer to compensate for high soil salinity in AMF-inoculated soil could be inefficient and lead to fertilizer run-off that would negatively impact surrounding ecosystems.

Diversity and Functionalities of Unknown Mycorrhizal Fungal Microbiota

Beneficial ecosystem services provided by arbuscular mycorrhizal fungi (AMF) are the outcome of their synergistic actions with diverse bacterial communities (AMF–associated bacteria; AAB) living in strict association with AMF hyphae and spores. Herein, bacterial diversity associated with 6 AMF species from 33 different co-cultures belonging to order Glomerales and Diversisporales were identified, using a combination of culture-dependent functional analyses and amplicon sequencing. Overall, 231 bacterial strains were isolated from the AMF spores and hyphae which covered 30 bacterial genera and 52 species. Hierarchical clustering based on plant growth promoting traits identified 9 clades comprising diverse bacterial genera with clades 7, 8 and 9 representing the most functionally rich AAB. High-throughput amplicon sequencing across a small subset of 8 AMF co-cultures spread across 3 AMF genera identified Operational Taxonomic Units belonging to 118 bacterial genera. The study revealed a greater diversity of AAB from spores of in vitro transformed AMF root co-cultures rather than in situ, pot AMF cultures. Functionally active, culturable AABs with multiple plant growth promoting traits such as phosphate solubilisation, nitrogen fixation, biofilm formation, enzyme and plant growth regulator production along with biocontrol activity were identified. These properties could be utilized individually and/or as consortia with AMF, as biological growth enhancers.

Arbuscular mycorrhizal fungi outcompete fine roots in determining soil multifunctionality and microbial diversity in a desert ecosystem

Fine roots and mycorrhizal fungi play a crucial role in soil nutrient cycling and microbial processes. However, the importance of the symbioses between fine roots and arbuscular mycorrhizal fungi (AMF) in different plant functional groups to maintain soil multifunctionality (the ability to provide multiple functions and services) and microbial diversity remains unclear, especially in desert ecosystems. In this study, we conducted an ingrowth core experiment on three vegetation types, namely shrub-dominated, grass-dominated, and mixed vegetation communities, in the Mu Us Desert, northern China, to investigate the importance of fine roots and mycorrhizal fungi in shaping soil nutrient composition and microbiome. Furthermore, we detected the relationships among AMF-related inputs [extraradical AMF hyphae and glomalin-related soil protein (GRSP)], soil multifunctionality, and soil microbial diversity. We found that most of the soil properties associated with nutrient cycling and microbial community composition and diversity varied among the three vegetation types, but were not significantly different between distinct ingrowth core treatments with fine root and hyphal access. AMF-related inputs, especially the easily extractable GRSP, were the most important determinants of soil multifunctionality and microbial community diversity across the shrub and grass communities, while the changes in soil multifunctionality and microbial diversity were inconsistent with the trend of fine root biomass. Moreover, AMF-related inputs were positively correlated with soil nutrients, particularly soil organic carbon (SOC). In contrast to the minimal negative correlation between SOC and soil microbial richness, soil multifunctionality was positively correlated with SOC. These findings support the role of AMF in shaping soil multifunctionality and microbial diversity by stabilizing SOC in a desert ecosystem, regardless of the fine root accessibility of plant functional groups. Therefore, this study improved our understanding of plant-derived carbon in the soil and its effects on the induction of soil abiotic and biotic processes in resource-limited ecosystems.

Foliar-applied potassium improved mycorrhizal Goji (Lycium barbarum L.) growth of the potassium free - compartment in a compartmented culture system

Arbuscular mycorrhizal (AM) fungi promote plant mineral nutrient acquisition, and AM fungal hyphae can transport water and nutrients. Potassium has significant effects on plant photosynthesis, stomatal conductance, and other physiological processes. However, it is little known whether foliar-applied potassium in one plant could affect the nearby plant that connected by the AM fungal hyphae network. We analyzed the effects of foliar-applied potassium (2% K2SO4) in the potassium additional compartment (potassium was foliar-sprayed on plant in this compartment) on growth, photosynthesis, chlorophyll fluorescence parameters, potassium content, and the relative expression of potassium channel/transporter genes (LbHAK, LbKAT3, LbAKT2, LbKT1, and LbSKOR) of mycorrhizal Lycium barbarum in the potassium-free compartment (potassium was not foliar-sprayed on plant in this compartment) via AM fungal hyphae network of a three compartments culture system (the system contains three compartments, namely two root compartments on the left and right and a hyphal compartment in the middle). Compared with inoculation of Rhizophagus irregularis, foliar-applied potassium improved growth, photosynthesis, and potassium content of mycorrhizal L. barbarum in the potassium-free compartment, but had no effect on mycorrhizal L. barbarum chlorophyll fluorescence parameters. Additionally, foliar-applied potassium increased the relative expressions of LbHAK, LbKAT3 LbKT1 and LbSKOR in roots of mycorrhizal plants in the potassium-free compartment, while the relative expression of LbAKT2 in shoots of mycorrhizal plant was increased in the potassium-free compartment. This study suggests that AM fungal hyphae network transports potassium to the potassium-free compartment, then potassium regulates the expression of potassium channel/transporter genes to promote potassium uptake and transport, thus improves photosynthesis, and ultimately, promotes the growth of mycorrhizal L. barbarum in the potassium-free compartment.

Enrichment of nosZ-type denitrifiers by arbuscular mycorrhizal fungi mitigates N2 O emissions from soybean stubbles.

Hotspots of N2 O emissions are generated from legume residues during decomposition. Arbuscular mycorrhizal fungi (AMF) from co-cultivated intercropped plants may proliferate into the microsites and interact with soil microbes to reduce N2 O emissions. Yet, the mechanisms by which or how mycorrhizal hyphae affect nitrifiers and denitrifiers in the legume residues remain ambiguous. Here, a split-microcosm experiment was conducted to assess hyphae of Rhizophagus aggregatus from neighbouring maize on overall N2 O emissions from stubbles of nodulated or non-nodulated soybean. Soil microbes from fields intercropped with maize/soybean amended with fertilizer nitrogen (SS-N1) or unamended (SS-N0) were added to the soybean chamber only. AMF hyphae consistently reduced N2 O emissions by 20.8%-61.5%. Generally, AMF hyphae promoted the abundance of N2 O-consuming (nosZ-type) denitrifiers and altered their community composition. The effects were partly associated with increasing MBC and DOC. By contrast, AMF reduced the abundance of nirK-type denitrifiers in the nodulated SS-N0 treatment only and that of AOB in the non-nodulated SS-N1 treatment. Taken together, our results show that AMF reduced N2 O emissions from soybean stubbles, mainly through the promotion of N2 O-consuming denitrifiers. This holds promise for mitigating N2 O emissions by manipulating the efficacious AMF and their associated microbes in cereal/legume intercropping systems.