Arbuscular Mycorrhizal Fungi Colonization Research Articles

Interactions between arbuscular mycorrhizal fungi and phosphate-soluble bacteria affect ginsenoside compositions by modulating the C:N:P stoichiometry in Panax ginseng.

The biomass production as well as the accumulation of secondary metabolites of plant is highly determined by the absorption of nutritional elements, in particular nitrogen (N) and phosphorus (P). Arbuscular mycorrhizal fungi (AMF) can absorb soluble P and transport it to plants, while phosphate solubilizing bacteria (PSB) can increase the content of solubilizing P in soil. Previous studies have identified the effects of either AMF or PSB inoculation on altering plant C:N:P stoichiometry, whether AMF interact with PSB in promoting plant growth and changing elemental concentration and composition of secondary metabolites by altering plant C:N:P stoichiometry remains ambiguous. In this study, we investigated the effects of inoculation of AMF, PSB, and their co-inoculation AMP (AMF and PSB) on the biomass growth, the C:N:P stoichiometry, the core microorganisms of rhizosphere soil, and the ginsenoside compositions of ginseng (Panax ginseng). The results showed that compared to control or single inoculation of AMF or PSB, co-inoculation of AMF and PSB significantly increased the AMF colonization rate on ginseng roots, increased the biomass of both above and under-ground parts of ginseng. Similarly, co-inoculation of AMF and PSB substantially increased the concentrations of N and P, reduced the ratios of C:P and N:P in the above-ground part of ginseng. The co-inoculation of AMF and PSB also increased concentrations of total ginsenosides and altered the compositions of ginsenosides in both the above and under-ground parts of ginseng. Analysis the rhizosphere microorganism showed that the co-inoculation of AMF and PSB recruited distinct core microorganisms that differ from the control and treatments with single inoculation of AMF or PSB. Our results suggested that PSB inoculation enhanced the positive effect of AMF in improving the absorption of nutrimental elements, altered the C:N:P stoichiometry and, ginsenosides concentration and composition of ginseng, influenced the plant rhizosphere microbial community. These findings offer valuable insights into enhancing plant biomass production and promoting secondary metabolites by improving the plant-fungi-bacterial relationships.

Synergism or Antagonism: Do Arbuscular Mycorrhizal Fungi and Plant Growth-Promoting Rhizobacteria Work Together to Benefit Plants?

In agriculture, abiotic and biotic stress reduce yield by 51–82% and 10–16%, respectively. Applications of biological agents such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) can improve plant growth. Applications of lone PGPR and AMF also help plants resist abiotic and biotic stressors. The reports for dual inoculation of AMF and PGPR to benefit plants and tackle stressors are largely unknown. It is speculated that PGPR colonization in plants enhances AMF infection during dual AMF and PGPR application, although increased AMF colonization does not always correlate with the increased benefits for the plant hosts. Further research is needed regarding molecular mechanisms of communication during dual inoculations, and dual-inoculation enhancement of induced systemic resistance under pathogen stress, to understand how dual inoculations can result in enhanced plant benefits. The influence of application timing of AMF and PGPR dual inoculations on mitigating abiotic and biotic stress is also not well understood. This review documents the factors that govern and modulate the dual application of AMF and PGPR for plant benefits against stress responses, specifically abiotic (drought) stress and stress from pathogen infection.

Micorrizas arbusculares y endófitos septados en tres especies de Thelypteridaceae de ambientes riparios de las Yungas (Tucumán, Argentina)

Background and aims: The status of the presence of arbuscular mycorrhizal fungi (AMF) in lycophytes and ferns has been analysed in 11% of them. This work aims to characterise and quantify the AMF colonisation and to characterise septate endophytes present on the roots of the Thelypteridaceae: Amauropelta jujuyensis, A. nubicola, and Pelazoneuron patens. M&M: Ten individuals per species were collected in August 2022. Conventional staining and techniques were used to estimate colonisation. Results: The root of Amauropelta jujuyensis, A. nubicola, and Pelazoneuron patens showed AMF with Arum and Paris morphological types simultaneously. The hyphal colonization showed no significant difference among species, arbuscular colonization was significantly higher in A. jujuyensis, while vesicular colonization was considerably higher in A. nubicola. In addition, septate endophytes were evident in the species of the genus Amauropelta. Conclusion: The association of AMF and other fungal endophytes with the native Argentine Thelypteridaceae Amauropelta jujuyensis, A. nubicola, and Pelazoneuron patens is evidenced for the first time in riparian environments of the Yungas. The coexistence of Arum and Paris morphological types in the three studied fern species is demonstrated.

Effects of warming and parasitism on root traits and the root economics space

Abstract Plants infected by parasitic species might be further stressed by climate warming as both factors can influence the host plant's nutrient acquisition and growth. The root economics space, defined by root functional traits, reflects a plant's nutrient acquisition strategy. However, the combined effects of warming and parasitism on root functional traits and their positions within the root economics space have not been extensively studies. We grew soybean plants in pot cultures outdoor in the absence or presence of parasitism by Cuscuta gronovii and with or without simulated climate warming using infrared heater lamps. We measured various root functional traits of soybean, including root morphological traits, symbiosis with arbuscular mycorrhizal fungi (AMF) and rhizobia and enzyme activity. Correlations among these traits were analysed, and principal component analysis was used to determine the position of the plants in the root economics space. Parasitism significantly reduced AMF colonization rate, nodule biomass, root tissue density (RTD) and phosphatase activity in the rhizosheath, while increasing root nitrogen concentration (RN). Nodule biomass was positively correlated with AMF colonization, indicating an ‘outsourcing’ strategy for nutrient foraging. Parasitized soybeans occupied a trait space with higher RN and lower RTD, indicative of a ‘fast’ nutrient acquisition strategy. Warming did not significantly affect root functional traits or the plants' positions in the root economics space, regardless of parasitism presence. This study is the first to demonstrate that rhizobial colonization, similar to AMF colonization, is part of the ‘outsourcing’ strategy and that parasitism shifts host plants from a ‘slow’ to a ‘fast’ nutrient uptake strategy. These findings provide new insights into plant below‐ground strategies under warming and parasitism. Read the free Plain Language Summary for this article on the Journal blog.

Microplastic additions modulate intraspecific variability in root traits and mycorrhizal responses across root‐life history strategies

Abstract Microplastics (MP) are recognized as a major pollutant in terrestrial environments, prompting concerns about their effects on plant–soil dynamics. Despite evidence of MP altering soil physicochemical properties, impacts on belowground root traits and arbuscular mycorrhizal (AM) fungi remain poorly explored. Existing research has mainly centred on a few model plant species, emphasizing root biomass, and often employs single polymer types and addition rates that surpass realistic scenarios. To investigate how environmentally relevant mixtures and concentrations of MPs impact plant growth, root trait expression and AM fungal colonization, we conducted a greenhouse experiment using six plant species chosen for their contrasting root life strategies; three species in the Amaryllidaceae family represented resource conservation root traits (Allium fistulosum (onion), Allium tuberosum (chive), Allium porrum (leek)), and three from the Solanaceae family, represented plants with resource acquisitive root traits (Solanum lycopersicum (tomato), Solanum melongena (eggplant), Capsicum annuum (pepper)). MP treatments consisted of control (0% MP), low (0.1% w/w) and high (1% w/w) MP additions, using an environmentally relevant MP mixture of weathered polymer types and shapes. We measured above and belowground biomass, average root trait expression (specific root length (SRL), average root diameter (D) and root tissue density (RTD)), AM fungal colonization, as well as intraspecific variability across MP addition treatments. We found that responses to environmentally relevant additions of MPs were species specific and not determined by root life‐strategy. MPs increased biomass in leek, eggplant and tomato, while decreasing AM fungal colonization in tomato. MP additions had no discernible impact on average root functional trait expression across species. However, the addition of MPs resulted in altered intraspecific variability in root traits and AM fungal colonization, indicating a mechanism for plant tolerance to MPs. To address the impacts of MPs on plant functioning, research needs to focus on environmentally relevant mixtures of MPs, considering various plant species' capacities to tolerate soil contamination and the potential for tipping points under real‐world conditions. Read the free Plain Language Summary for this article on the Journal blog.

Cover crop grazing length impacts on soil health and crop productivity in US Coastal Plain soils

AbstractIntroducing integrated crop‐livestock systems into row crop production promotes income diversification and potential soil health benefits through cover crop grazing on degraded soils of the southeastern United States, but effects of these practices on crop yields and soil health in Coastal Plain soils are not well established. A 4‐year study was performed to evaluate the effects of grazing a multi‐species winter cover crop on soil health and crop yields under mid‐February, mid‐March, and mid‐April cattle removal dates and a non‐grazed control within an annual cotton (Gossypium hirsutum L.) and peanut crop rotation (Arachis hypogaea L.). Chemical soil health indicators (soil organic carbon and permanganate oxidizable carbon), physical soil health indicators (water‐stable aggregates and penetration resistance), biological soil health indicators (microbial biomass carbon, soil respiration, and arbuscular mycorrhizal fungi colonization), crop yield, and cover crop biomass were evaluated. Cover crop biomass at termination was reduced by 3660, 5250, and 5610 kg ha−1 for the mid‐February, mid‐March, and mid‐April cattle removal treatments compared to the non‐grazed control. No grazing treatment effects were observed for biological soil properties. Soil organic carbon was higher in the non‐grazed treatment than the mid‐April grazing treatment across 0‐ to 30‐cm depth. Penetration resistance across 0‐ to 50‐cm depth and water‐stable aggregates at the 0‐ to 30‐cm depth were both negatively impacted by increased grazing period lengths. Results from this study suggest that longer cover crop grazing periods have little effect on biological and chemical soil health indicators in the short term but can negatively impact some physical soil health indicators.

Winter forage crops influence soil properties through establishing different arbuscular mycorrhizal fungi communities in paddy field

Winter planting is promising for improving the utilization rate of fallow paddy fields in southern China by establishing arbuscular mycorrhizal fungi (AMF) communities. However, the effects of different winter forage crops on AMF community construction remain unknown. The AMF community establishment of different winter planting forage crops were conducted in oat, rye, Chinese milk vetch, and ryegrass, with winter fallow as a control. The AMF colonization rate, soil AMF spore density, community structure and diversity, and soil physicochemical properties were determined. The results showed that the total nitrogen and available nitrogen in winter Chinese milk vetch were 11.11% and 16.92% higher than those in winter fallow (P < 0.05). After planting winter forage crops, the AMF spore density in winter oat, rye, Chinese milk vetch, and ryegrass soil were 127.90%, 64.37%, 59.91%, and 73.62% higher than that before planting, respectively (P < 0.05). Claroideoglomus was the dominant AMF genus in the soil of winter planting oat, rye, and ryegrass. The average membership function value of winter Chinese milk vetch was the highest, indicating that it had the best comprehensive effect on soil physicochemical properties, AMF community structure and diversity, and fresh forage yield. Winter forage crops could increase the spore pool of soil AMF and improve the soil AMF community structure and diversity. Winter Chinese milk vetch in paddy field had the best comprehensive effect on soil physicochemical properties and soil AMF community according to the comprehensive evaluation. These findings provide a theoretical basis for sustainable development and utilization of the southern rice paddy ecosystem.

Role of Arbuscular Mycorrhizal Fungi in Alleviating Salinity Stress and Improving Physiological Parameters of Wheat (Triticum aestivum L.): A Review

Salinity stress poses a significant threat to global wheat production, impacting crop yield and food security. In recent years, Arbuscular Mycorrhizal Fungi (AMF) have gained attention as potential bioinoculants capable of mitigating salinity-induced stress and improving plant physiological parameters. This review provides a comprehensive examination of the role of AMF in alleviating salinity stress and enhancing physiological parameters in wheat (Triticum aestivum L.). Through a systematic analysis of relevant literature, we explore the mechanisms underlying the beneficial interactions between AMF and wheat under saline conditions. Key findings from various studies demonstrate that AMF colonization enhances wheat growth, nutrient uptake, and antioxidant enzyme activities, while reducing the adverse effects of salinity stress. However, challenges such as variability in AMF effectiveness and compatibility with modern agricultural practices persist. Future research directions should focus on refining AMF inoculation techniques and developing strains with enhanced salt tolerance to maximize their potential in sustainable agriculture. Overall, this review underscores the promising role of AMF in revolutionizing wheat cultivation in saline environments, offering insights for enhancing crop productivity and resilience to salinity stress.

The crosstalk interaction of ethylene, gibberellins, and arbuscular mycorrhiza improves growth in salinized tomato plants by modulating the hormonal balance

Ethylene (ET) and gibberellins (GAs) play key roles in controlling the biotic and abiotic interactions between plants and environment. To gain insights about the role of ET and GAs interactions in the mycorrization and response to salinity of tomato (Solanum lycopersicum L.) plants, the ET-insensitive (Never-ripe, Nr), and the ET-overproducer (Epinastic, Epi) mutants and their wild type cv. Micro-Tom (MT), were inoculated or not with the arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis and exposed to control (0 mM NaCl) and salinity (100 mM NaCl) conditions, with and without gibberellic acid (10−6 M GA3) application during four weeks. Exogenous GA3 enhanced plant growth irrespective of the genotype, AMF, and salinity conditions, while an additional effect on growth by AMF was only found in the ET-overproducer (Epi) mutant under control and salinity conditions. Epi almost doubled the AMF colonization level under both conditions but was the most affected by salinity and GA3 application compared to MT and Nr. In contrast, Nr registered the lowest AMF colonization level, but GA3 produced a positive effect, particularly under salinity, with the highest leaf growth recovery. Foliar GA3 application increased the endogenous concentration of GA1, GA3, and total GAs, more intensively in AMF-Epi plants, where induced levels of the ET-precursor ACC were also found. Interestingly, GA4 which is associated with AMF colonization, registered the strongest genotype x GA x AMF × salinity interactions. The different growth responses in relation to those interactions are discussed.

Combined inoculation of arbuscular mycorrhiza fungi with Meso‐rhizobium improves nutrient uptake, growth performance, and moisture stress tolerance of chickpea (Cicer arietinum L.)

AbstractBiofertilizers can be better alternatives to chemical fertilizers to enhance plant nutrition and productivity as they improve the soil fertility and crop productivity in an eco‐friendly and cost‐effective manner. A pot experiment was conducted between December 2018 and March 2019 in southern Ethiopia to evaluate the combined inoculation of arbuscular mycorrhizal fungi (AMF) and Meso‐rhizobium (MR) on biomass yield, nutrient uptake, and moisture stress tolerance of chickpea (Cicer arietinum L.) (variety: Habru). The experiment was executed as a factorial arrangement using a completely randomized design with three replications. The treatments were control (non‐fertilized), sole AM fungi inoculation, AM fungi inoculation with phosphorus fertilizer (20 kg P ha−1) and MR, and sole inorganic fertilizers (20 kg P;10 kg N ha−1) at four different moisture levels (optimum throughout the growing season, stressed at vegetative, flowering, and seed filling stages). The results demonstrated that biomass yields were limited by moisture stress, especially at vegetative and flowering stages of chickpea. Sole and co‐application of AMF with MR and inorganic P increased biomass yields on average by 19%, 39%, and 33% under water stress conditions, respectively, compared to the non‐inoculated control. The application of AMF with MR and inorganic P also significantly increased nodulation, AMF colonization, and nutrient uptake, but these effects were dependent on soil moisture status. In conclusion, there are potential advantages to be gained from sole and combined AMF application with rhizobium to improve growth and productivity of chickpea through enhanced nutrient and water uptake, though the results of this pot experiment should be validated through field trials.

The effectiveness of combination of arbuscular mycorrhizal fungi and compost ameliorant on sengon growth in former coal mine soil

Abstract Mining activities give a negative impact to the soil which become the ex-coal mine soil. The soil has a solid soil structure and low nutrient content so is not suitable for planting. The problems need to be improved by being treated with biological agents from soil microorganisms such as Arbuscular Mycorrhizal Fungi (AMF). The provision of AMF on ex-coal mine soil with the addition of ameliorant compost can be one strategy that can be used. AMF can help increase plant growth and help the process of absorption of phosphate (P) by plants. Compost from goat manure can help the association between AMF and plant roots, also being a source of nutrients that are free from chemicals. The plants which suitable for this association are sengon. Sengon commonly used to help revegetation of ex-mining soil because it is able to withstand various conditions of overgrown soil. This study aims to determine the effect of the addition of a combination of AMF and compost on the growth of sengon plants in the soil of ex-coal mines. Observations were made weekly until the age of three months, the best results were the results at the end of the observation. The results showed that the AMF dose and the addition of compost had an effect on percent AMF colonization, increasing plant height, dry weight of plant roots increasing plant stem diameter, and number of leaves.

Addition of polyester microplastic fibers to soil alters the diversity and abundance of arbuscular mycorrhizal fungi and affects plant growth and nutrition

Microplastics (MPs) represent an emerging factor in global environmental change and are increasingly found in soils. However, the extent to which they affect plants and their interactions with the soil microbiome is poorly understood. Here, we test the hypothesis that increasing levels of polyester MP fibers in soil alter plant growth and nutrient acquisition responses to arbuscular mycorrhizal (AM) fungi via changes in AM fungal colonization and community composition. We used Sorghum drummondii as a model species in a fully factorial greenhouse experiment. Plants were exposed to soil treatments with 0, 0.2, 1, and 3 % MP polyester fibers either in the presence or absence of an assembled AM fungal community comprising 13 species across three families with contrasting life-history strategies. We found that the 1 % MP treatment promoted plant biomass irrespective of the presence of AM fungi. While no changes in macronutrient concentrations in plant tissues were seen, there was a significant increase in B and Mn when relatively low amounts of MPs were added, and this effect was modulated by AM fungi. Furthermore, there were shifts in AM fungal community composition in response to MP, favoring taxa such as Gigaspora sp. while negatively affecting ruderal taxa like Glomus sp. Overall, our data indicate that MP polyester fibers present in soil can in some cases be beneficial to plants and AM fungal interactions. However, the implications of these findings over the long-term and in the context of ecological repercussions of MP pollution in the environment remain to be seen.

Can earthworms and root traits improve plant struvite-P uptake? A field mesocosm study

The availability of conventional linear mineral phosphorus (P) fertilization will become lower as phosphate rock stocks are limited and strongly concentrated in a few locations. Therefore, we need to increase agronomic P use efficiency and find alternative, recycled, sources of P. Two possible solutions mentioned in the literature are (i) using struvite, a mineral circular P fertilizer; and (ii) making use of earthworm activity, which has been shown to increase P availability. Here, we study the interaction between these two approaches, with the hypothesis that earthworms could increase the P availability from the poorly soluble struvite. We set up a field-based mesocosm experiment in a sandy soil with a low agronomic P status with 13 different treatments combining three earthworms species (Lumbricus rubellus Hoffmeister, Aporrectodea caliginosa Savigny and A. longa Ude alone or in a threes species mixture), different P fertilizers (no P, Triple Super Phosphate (TSP) and struvite). The experiment lasted 13 months (five fertilisation-harvest cycles). We found that, in field conditions, the yield and P uptake of Lolium perenne did not differ between fertilization with struvite or TSP. Earthworms only played a minor role in explaining ryegrass P uptake compared to fertilisation. We did not see either positive nor negative interactions between earthworms and struvite, meaning that earthworms did not further increase the P availability from struvite. The equal performances of struvite and TSP are explained by an enhanced effort from plants to actively take up P through a modification of root traits. This includes increased arbuscular mycorrhizal fungi colonisation and the production of finer and longer roots. Our results show that struvite performs comparably to TSP under realistic field conditions, making it a viable alternative to phosphate rock-based fertilizers.

Morphological type and taxonomic diversity of arbuscular mycorrhizal fungi along an altitudinal gradient at Mount Ibuki, Japan

ABSTRACT Arbuscular mycorrhiza (AM) associations are among the most widespread interactions between plants and fungi. However, little is known about the AM distribution along altitudinal gradients in forest ecosystems, where the gradients are accompanied by shifts in climatic conditions and soil properties as well as the identity of host plant species. This study aimed to clarify AM fungal associations along an altitudinal gradient. Therefore, we determined the colonization rate and community composition of AM fungi at different elevations on Mount Ibuki, Japan. Root and soil samples were collected from Cryptomeria japonica at altitudes of 200, 500, and 800 m, Acer shirasawanum at an altitude of 1100 m, and Chrysanthemum japonicum at the summit of 1350 m. To evaluate AM fungal colonization, 15 root samples from each altitude were examined microscopically. These samples were identified by targeting V4 and V5 regions of a partial small subunit rRNA gene using Sanger sequencing. AM fungal colonization rates were significantly and positively correlated with altitude. The Arum and Paris types were observed in all plant species examined at each altitude. In total, 101 molecular operational taxonomic units belonging to two genera were identified: Glomus and Diversispora. No significant clustering among elevations was observed in the AM fungal community composition. Among environmental variables, soil temperature, and pH significantly affected AM fungal structure patterns. These results suggest that as altitude increases, plants require more tight mycorrhizal associations, which are selectively filtered by the surrounding environment.

Mycobiota of revegetated post‐mining and adjacent unmined sites 10 years after mining decommissioning

Although overlooked in post‐mining rehabilitation, soil mycobiota constitute an important fraction of biodiversity, playing pivotal functions in soil that contribute to the revegetation process and soil stability in post‐mining environments. Evaluating the rehabilitation progress requires comparing it, when possible, with a reference site, preferably identical or similar to pre‐mining characteristics. Here, we investigated the mycobiota from a reference site, comparable to pre‐mining characteristics, and a post‐mining revegetated site 10 years after decommissioning and revegetation, during rainy and dry seasons. We combined the metabarcoding approach with functional traits from fungal operational taxonomic units and complemented our results with traditional techniques for arbuscular mycorrhizal fungi (AMF) surveys using spore morphology and mycorrhizal colonization. Our findings demonstrated that the composition of the fungal community exhibited more differences between the two sites studied than the intra‐annual periods assessed, even though the sites were under the same climatic conditions, spatially nearby, and without barriers between them. The mycobiota composition displayed differences between sites from phylum to genus levels. However, the predictive trophic modes (pathotrophs, saprotrophs, and symbionts) were equivalent in the two sites. All roots of plants assessed had AMF colonization, and AMF spore densities were similar. While many fungal taxa were present at both sites, the spatial connectivity between both sites was insufficient for equivalence of fungal community structure and composition. Differences in chemical and physical soil characteristics may have shaped the fungal communities. This study highlights the need to comprehend the fungal community from mining environments, considering concepts of landscape connectivity.

The costs and benefits of symbiotic interactions: variable effects of rhizobia and arbuscular mycorrhizae on Vigna radiata accessions

BackgroundThe symbiosis among plants, rhizobia, and arbuscular mycorrhizal fungi (AMF) is one of the most well-known symbiotic relationships in nature. However, it is still unclear how bilateral/tripartite symbiosis works under resource-limited conditions and the diverse genetic backgrounds of the host.ResultsUsing a full factorial design, we manipulated mungbean accessions/subspecies, rhizobia, and AMF to test their effects on each other. Rhizobia functions as a typical facilitator by increasing plant nitrogen content, plant weight, chlorophyll content, and AMF colonization. In contrast, AMF resulted in a tradeoff in plants (reducing biomass for phosphorus acquisition) and behaved as a competitor in reducing rhizobia fitness (nodule weight). Plant genotype did not have a significant effect on AMF fitness, but different mungbean accessions had distinct rhizobia affinities. In contrast to previous studies, the positive relationship between plant and rhizobia fitness was attenuated in the presence of AMF, with wild mungbean being more responsive to the beneficial effect of rhizobia and attenuation by AMF.ConclusionsWe showed that this complex tripartite relationship does not unconditionally benefit all parties. Moreover, rhizobia species and host genetic background affect the symbiotic relationship significantly. This study provides a new opportunity to re-evaluate the relationships between legume plants and their symbiotic partners.

Effects of grassland degradation on diversity of arbuscular mycorrhizal fungi of a pioneer plant.

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts that engage in crucial interactions with plants, playing a vital role in grassland ecology. Our study focuses on the pioneer plant Agropyron cristatum, and we collected soil samples from four degraded grasslands in Yudaokou to investigate the response of community composition to the succession of degraded grasslands. We measured the vegetation status, soil physical and chemical properties, AMF colonization, and spore density in different degraded grasslands. High-throughput sequencing was employed to analyze AMF in soil samples. Correlations among community composition, soil characteristics, and plant factors were studied using principal component and regression analyses. The distribution of AMF in grasslands exhibited variation with different degrees of degradation, with Glomus, Scutellospora, and Diversispora being the dominant genera. The abundance of dominant genera in AMF also varied, showing a gradual increase in the relative abundance of the genus Diversispora with higher degradation levels. AMF diversity decreased from 27.7% to 12.4% throughout the degradation process. Among 180 samples of Agropyron cristatum plants, AMF hyphae and vesicles displayed the highest infection status in non-degraded grasslands and the lowest in severely degraded ones. Peak AMF spore production occurred in August, with maximum values in the 0-10-cm soil layer, and the highest spore densities were found in lightly degraded grasslands. Apart from pH, soil factors exhibited a positive correlation with AMF infection during grassland degradation. Furthermore, changes in AMF community composition were jointly driven by vegetation and soil characteristics, with vegetation coverage and soil organic carbon significantly impacting AMF distribution. Significant differences in AMF variables (spore number and diversity index) were also observed at different soil depths. Grassland successional degradation significantly influences AMF community structure and composition. Our future focus will be on understanding response mechanisms and implementing improvement methods for AMF during grassland degradation and subsequent restoration efforts.

The Use of Compost and Arbuscular Mycorrhizal Fungi and Their Combination to Improve Tomato Tolerance to Salt Stress.

Salinity poses a significant challenge to tomato plant development and metabolism. This study explores the use of biostimulants as eco-friendly strategies to enhance tomato plant tolerance to salinity. Conducted in a greenhouse, the research focuses on the Solanum lycopersicum L. behavior under saline conditions. Tomato seeds were treated with arbuscular mycorrhizal fungi (AMF), compost, and their combination under both non-saline and saline conditions (0 and 150 mM NaCl). Plant height, number of flowers and fruits, shoot fresh weight, and root dry weight were negatively impacted by salt stress. The supplementation with compost affected the colonization of AMF, but the application of stress had no effect on this trait. However, the use of compost and AMF separately or in combination showed positive effects on the measured parameters. At the physiological level, compost played a beneficial role in increasing photosynthetic efficiency, whether or not plants were subjected to salinity. In addition, the application of these biostimulants led to an increase in nitrogen content in the plants, irrespective of the stress conditions. AMF and compost, applied alone or in combination, showed positive effects on photosynthetic pigment concentrations and protein content. Under salt stress, characterized by an increase in lipid peroxidation and H2O2 content, the application of these biostimulants succeeded in reducing both these parameters in affected plants through exhibiting an increase in antioxidant enzyme activity. In conclusion, incorporating compost, AMF, or their combined application emerges as a promising approach to alleviate the detrimental impacts of salt stress on both plant performances. These findings indicate optimistic possibilities for advancing sustainable and resilient agricultural practices.

Arbuscular mycorrhizal fungi enhance drought resistance in Bombax ceiba by regulating SOD family genes.

The physiological activity facilitated by arbuscular mycorrhizal fungi (AMF) contributes to plants' ability to tolerate drought. Nevertheless, it is unclear if AMF colonization affects the expression of genes in the host plant that encode antioxidant enzymes in the superoxide dismutase (SOD) family, which help alleviate drought stress in plants. Here, we conducted a pot trial to determine whether colonization by the AMF Rhizophagus irregularis improves drought resistance in Bombax ceiba. We comprehensively analyzed the SOD gene family and evaluated genome-wide expression patterns of SODs and SOD activity in AMF-colonized and non-mycorrhizal plants under simulated drought. We identified a total of 13 SODs in the genome of B. ceiba, including three FeSODs (BcFSDs), three MnSODs (BcMSDs), and seven Cu/ZnSODs (BcCSDs). Phylogenetic analysis based on binding domain revealed that SOD genes from B. ceiba and various other plant species can be divided into three separate groups, showing significant bootstrap values. Our examination of gene composition and patterns suggests that most BcSOD genes in these three subgroups are significantly conserved. Additionally, it was noted that hormones and stress-responsive cis-regulatory elements were found in all BcSOD promoters. Expression profiling by qRT-PCR demonstrated that AMF increased relative expression levels of Cu/Zn-SODs in both roots and shoots under drought stress, except for BcCSD3 in roots. Furthermore, AMF colonization increased the relative expression of BcMSD1a and BcMSD1b in roots, augmenting SOD activities and increasing ROS scavenging during drought. In general, this work offers molecular evidence in support of the beneficial effect of AMF colonization on drought tolerance in B. ceiba. It also elucidates the expression patterns of SOD genes, which will support efforts to optimize mycorrhizal seedling cultivation under stressful conditions.

Iron Nanostructure Primes Arbuscular Mycorrhizal Fungi Symbiosis Tightly Connecting Maize Leaf Photosynthesis via a Nanofilm Effect.

It is crucial to clarify how the iron nanostructure activates plant growth, particularly in combination with arbuscular mycorrhizal fungi (AMF). We first identified 1.0 g·kg-1 of nanoscale zerovalent iron (nZVI) as appropriate dosage to maximize maize growth by 12.7-19.7% in non-AMF and 18.9-26.4% in AMF, respectively. Yet, excessive nZVI at 2.0 g·kg-1 exerted inhibitory effects while FeSO4 showed slight effects (p > 0.05). Under an appropriate dose, a nano core-shell structure was formed and the transfer and diffusion of electrons between PS II and PS I were facilitated, significantly promoting the reduction of ferricyanide and NADP (p < 0.05). SEM images showed that excessive nZVI particles can form stacked layers on the surface of roots and hyphae, inhibiting water and nutrient uptake. TEM observations showed that excessive nanoparticles can penetrate into root cortical cells, disrupt cellular homeostasis, and substantially elevate Fe content in roots (p < 0.05). This exacerbated membrane lipid peroxidation and osmotic regulation, accordingly restricting photosynthetic capacity and AMF colonization. Yet, appropriate nZVI can be adhered to a mycelium surface, forming a uniform nanofilm structure. The strength of the mycelium network was evidently enhanced, under an increased root colonization rate and an extramatrical hyphal length (p < 0.05). Enhanced mycorrhizal infection was tightly associated with higher gas exchange and Rubisco and Rubisco enzyme activities. This enabled more photosynthetic carbon to input into AMF symbiont. There existed a positive feedback loop connecting downward transfer of photosynthate and upward transport of water/nutrients. FeSO4 only slightly affected mycorrhizal development. Thus, it was the Fe nanostructure but not its inorganic salt state that primed AMF symbionts for better growth.