Arbuscular Mycorrhizal Fungi Communities In Roots Research Articles

Year-round dynamics of arbuscular mycorrhizal fungi communities in the roots and surrounding soils of Cryptomeria japonica

Arbuscular mycorrhizal fungi (AMF) live simultaneously inside and outside of host plant roots for a functional mycorrhizal symbiosis. Still, the year-round dynamics and relationships between soil properties and AMF communities of trees in forest ecosystems remain unclear. We collected paired root and soil samples of the same Cryptomeria japonica trees at two forest sites (five trees at each site) every 2 months over a year. Total DNA was extracted from roots and soil separately and soil physicochemical properties were measured. With Illumina’s next-generation amplicon sequencing targeting the small subunit of fungal ribosomal DNA, we clarified seasonal dynamics of soil properties and AMF communities. Soil pH and total phosphorus showed significant seasonality while total carbon, nitrogen, and C/N did not. Only pH was a good predictor of the composition and dynamics of the AMF community. The total AMF community (roots + soil) showed significant seasonality because of variation from May to September. Root and soil AMF communities were steady year-round, however, with similar species richness but contained significantly different AMF assemblages in any sampling month. Despite the weak seasonality in the communities, the top two dominant OTUs showed significant but different shifts between roots and soils across seasons with strong antagonistic relationships. In conclusion, few dominant AMF taxa are dynamically shifting between the roots and soils of C. japonica to respond to seasonal and phenological variations in their microhabitats. AMF inhabiting forest ecosystems may have high environmental plasticity to sustain a functional symbiosis regardless of seasonal variations that occur in the soil.

Transferred communities of arbuscular mycorrhizal fungal persist in novel climates and soils

Symbiotic mycorrhizal fungi strongly influence plant establishment and growth particularly in harsh environments, whereby sympatric, presumably co-adapted symbionts are considered particularly beneficial. However, the response of transferred sympatric mycorrhizal fungal communities to new environments remains largely ignored. We therefore studied the relative importance of initial inoculum, soil and climatic conditions on the composition, diversity and root colonization ability of arbuscular mycorrhizal fungal (AMF) communities. To do so, we analyzed the AMF communities in an extensive experiment with two ecotypes of Bouteloua gracilis planted in their sites of origin and in four new sites differing in climate and soil properties.After three seasons of growth, the sympatric AMF communities were little changed by the new abiotic conditions. The composition of the AMF communities in plant roots was most strongly determined by the initial inoculum, while the contribution of divergent soil and climatic conditions was an order of magnitude smaller. The levels of root colonization by AMF, in contrast, were significantly influenced by climatic and soil conditions and did not differ among communities of different origins. Their pattern indicates that mycorrhiza formation is facilitated in the plant's sympatric soil and climatic conditions, but also that transferred AMF communities adjust mycorrhiza formation to new abiotic conditions.

Arbuscular Mycorrhizae Fungi Diversity in the Root–Rhizosphere–Soil of Tetraena mongolica, Sarcozygium xanthoxylon, and Nitraria tangutorum Bobr in Western Ordos, China

Arbuscular mycorrhizal fungi (AMF) are considered to be an essential indicator of ecosystem biodiversity and can increase a plant’s ability to withstand arid conditions. Despite the obvious significance of AMF in the root and rhizosphere system, little is known about how the AMF variety varies between the soil and roots of endangered plants and how this varies depending on habitats in dry and semiarid regions. This study aimed to address this research gap by investigating the characteristics and diversity of AMF colonization in Zygophyllaceae. Using Illumina MiSeq high-throughput sequencing, indigenous AMF in the roots and rhizosphere soil of three endangered plants (Tetraena mongolica, Sarcozygium xanthoxylon, and Nitraria tangutorum Bobr) were investigated. The three threatened plants had different AMF populations in their root and rhizosphere soils, according to a hierarchical clustering analysis. AMF communities in rhizosphere soil were more sensitive to LDA than root AMF communities based on linear discriminant analysis effect size (LEfSe). Glomus, Septoglomus, and Rhizophagus were seen to function as dominant fungi as the soil and root AMF populations carried out their various tasks in the soil and roots as a cohesive collective. Distance-based redundancy analysis (db-RDA) showed that pH, total phosphorus, and accessible potassium were closely associated with AMF communities. The pH of the soil appears to be an important factor in determining AMF community stability. These findings can serve as a guide for the use of AM fungus in the rehabilitation of agricultural land in arid regions. In summary, our work contributed new knowledge for the scientific preservation of these endangered plant species and for the further investigation of the symbiotic link between AMF and endangered plant species.

Paired Root-Soil Samples and Metabarcoding Reveal Taxon-Based Colonization Strategies in Arbuscular Mycorrhizal Fungi Communities in Japanese Cedar and Cypress Stands.

Arbuscular mycorrhizal fungi (AMF) in the roots and soil surrounding their hosts are typically independently investigated and little is known of the relationships between the communities of the two compartments. We simultaneously collected root and surrounding soil samples from Cryptomeria japonica (Cj) and Chamaecyparis obtusa (Co) at three environmentally different sites. Based on molecular and morphological analyses, we characterized their associated AMF communities. Cj was more densely colonized than Co and that root colonization intensity was significantly correlated with soil AMF diversity. The communities comprised 15 AMF genera dominated by Glomus and Paraglomus and 1443 operational taxonomic units (OTUs) of which 1067 and 1170 were in roots and soil, respectively. AMF communities were significantly different among sites, and the root AMF communities were significantly different from those of soil at each site. The root and soil AMF communities responded differently to soil pH. At the genus level, Glomus and Acaulospora were abundant in roots while Paraglomus and Redeckera were abundant in soil. Our findings suggest that AMF colonizing roots are protected from environmental stresses in soil. However, the root-soil-abundant taxa have adapted to both environments and represent a model AMF symbiont. This evidence of strategic exploitation of the rhizosphere by AMF supports prior hypotheses and provides insights into community ecology.

Changes of root AMF community structure and colonization levels under distribution pattern of geographical substitute for four Stipa species in arid steppe

The establishment of symbiotic relationship between arbuscular mycorrhizal fungi (AMF) and roots is a mutually beneficial process and plays an important role in plant succession in ecosystems. However, there is less understanding of information about the AMF community in roots under vegetation succession on a large regional scale, especially the spatial variation in the AMF community and its potential ecological functions. Here, we elucidated the spatial variations in root AMF community structure and root colonization along a distribution pattern of four zonal Stipa species in arid and semiarid grassland systems and explored key factors regulating AMF structure and mycorrhizal symbiotic interactions. Four Stipa species established a symbiosis with AMF, and annual mean temperature (MAT) and soil fertility were the main positive and negative driving factors of AM colonization, respectively. The Chao richness and Shannon diversity of AMF community in the root system of Stipa species tended to increase firstly from S. baicalensis to S. grandis and then decreased from S. grandis to S. breviflora. While evenness of root AMF and root colonization showed a trend of increasing from S. baicalensis to S. breviflora, and biodiversity was principally affected by soil total phosphorus (TP), organic phosphorus (Po) and MAT. It is emphasized that Stipa species have certain dependence on AMF, especially in a warming environment, and the root AMF community structure among the four Stipa taxa was different. Additionally, the composition and spatial distribution of root AMF in host plants varied with MAT, annual mean precipitation (MAP), TP and host plant species. These results will broaden our understanding of the relationship between plant and AMF communities and their ecological role, and provide basic information for the application of AMF in the conservation and rehabilitation of forage plants in degraded semiarid grasslands.

Effects of pavements on diversity and activity of mycorrhizal symbionts associated with urban trees

This study investigated the impact of different types of soil sealing on the communities of a group of beneficial plant symbionts, arbuscular mycorrhizal fungi (AMF), colonizing the roots of two shade trees, Celtis australis and Fraxinus ornus, frequently grown in urbanized sites. Such plants were grown in an experimental site, in northern Italy, established in November 2011 and subjected to four different pavement treatments: impermeable monolithic asphalt, permeable pavers, permeable concrete and unpaved soil. The diversity and composition of root AMF communities were assessed by PCR denaturating gradient gel electrophoresis of partial 18S rRNA gene, AMF taxa were identified by amplicon sequencing and mycorrhizal colonization was evaluated after root clearing and staining. For the first time, our molecular work revealed that impermeable pavements induced shifts in the composition of AMF communities associated to the roots of C. australis and F. ornus and impacted on the percentage of mycorrhizal root length. When the root-zone was covered with permeable pavements, a similar AMF community as that observed in the unpaved soil was detected, providing novel information to be utilised for reducing the disturbance caused by specific types of soil sealing on AMF symbionts, which play a key role in plant nutrition and health. A total of 45 AMF sequence types were detected, with Sclerocystis and Septoglomus as the most abundant phylotypes, accounting for 84% of the sequences. The predominance of Sclerocystis species in the roots of both tree species under impermeable pavements indicated their high and unforeseen tolerance towards harsh environmental conditions. Such species could be utilized as AMF inocula specifically selected for their proven resilience in paved sites, in order to exploit their ability to boost biogeochemical processes fundamental for energy fluxes and plant nutrition and health.

Effects of partial substitution of chemical fertilizer with organic fertilizer on arbuscular mycorrhizal fungal community of Mangifera indica

Nutrient enrichment caused by fertilization would reduce the diversity of arbuscular mycorrhizal fungi (AMF). To explore whether partial substitution of chemical fertilizer with organic fertilizer would alleviate the negative effects of nutrient enrichment on AMF, we conducted a two-year mango (Mangifera indica) field experiment to examine the effects of different fertilization regimes on AMF communities in roots and rhizospheric soils by using high-throughput sequencing. The treatments included chemical-only fertilization (control), and two kinds of organic fertilizer (commercial organic fertilizer and bio-organic fertilizer) with replacing 12% (low) and 38% (high) chemical fertilizer. The results showed that under equivalent nutrient input, partial substitution of chemical fertilizer with organic fertilizer had positive effects on the yield and quality of mango. The application of organic fertilizer could effectively increase AMF richness. AMF diversity was significantly positively correlated with some indices of fruit quality. Compared with chemical-only fertilization, high replacement ratio of organic fertilizer could significantly change root AMF community, but did not affect AMF community in the rhizospheric soil. Bio-organic fertilizer could enrich more AMF species and form a more complex AMF co-occurrence network than commercial organic fertilizer. In all, replacing chemical fertilizer with a high proportion of organic fertilizer could improve the yield and quality of mango while maintain AMF richness. The changes of AMF community caused by organic fertilizer substitution pre-ferably occurred in roots rather than soils.

Multidimensional analysis reveals environmental factors that affect community dynamics of arbuscular mycorrhizal fungi in poplar roots.

Poplar is a tree species with important production and application value. The symbiotic relationship between poplar and arbuscular mycorrhizal fungi (AMF) has a key role in ecosystem functioning. However, there remain questions concerning the seasonal dynamics of the AMF community in poplar roots, the relationship between AMF and the soil environment, and its ecological function. Poplar roots and rhizosphere soil were sampled at the end of April and the end of October. The responses of AMF communities to season, host age, and host species were investigated; the soil environmental factors driving community changes were analyzed. The diversity and species composition of the AMF community were higher in autumn than in spring. Season, host age, host species, and soil environmental factors affected the formation of the symbiotic mycorrhizal system and the AMF community. Differences in the communities could be explained by soil pH, total nitrogen, total phosphorus, total potassium, available potassium, and glomalin content. The AMF community was sensitive to changes in soil physicochemical properties caused by seasonal dynamics, particularly total potassium. The change in the mycorrhizal symbiotic system was closely related to the growth and development of poplar trees.

Effect ofElymus nutans on the assemblage of arbuscular mycorrhizal fungal communities enhanced by soil available nitrogen in the restoration succession of revegetated grassland on theQinghai‐TibetanPlateau

AbstractThe succession of arbuscular mycorrhizal fungi (AMF) communities during ecosystem development has received widespread attention, but the ecological mechanism that drives the succession of AMF communities during the restoration process in alpine meadow ecosystems remains unclear. Here, we treated ‘Black Beach’ (severely degraded alpine meadow) as the baseline for restoration (0 year), and selected the revegetated grassland ofElymus nutanswith different planting times (3, 7, 10, and 14 years) to analyze the species composition of the AMF community in mixed roots (at the whole‐plant‐community scale) and inE. nutansroots (at the single‐plant‐species scale). A total of 46 AMF phylotypes (mixed roots: 44;E. nutansroots: 46) were identified in both root systems, predominantly belonging to Glomeraceae. AMF species richness showed a single‐peak curve change across the restoration time and reached its peak at 3 years in both root systems. In mixed roots, the soil available nitrogen not only directly changed the AMF species composition but also indirectly changed the AMF species composition through plant richness. In theE. nutansroots, only the soil available nitrogen drove changes in AMF species composition through changes in plant richness. Our results indicate thatE. nutans, a key species in the restoration process of revegetated grassland, can enhance its regulation to assemble the AMF community through soil available nitrogen at the two research scales, suggesting that the scientific management of soil nitrogen availability during restoration succession could strengthen the mutual symbiosis of ‘plant‐AMF,’ thereby retarding the occurrence of secondary degradation of revegetated grassland.

Dominance of arbuscular mycorrhizal fungi is key for Mongolian steppe management under livestock grazing, as indicated by ecosystem multifunctionality

Livestock grazing of drylands supports millions of livelihoods worldwide; however, overgrazing causes severe biodiversity loss and degrades ecosystem functions. Understanding the effects of grazing intensity, aridity, and soil microbes is required for sustainable management. Here, we focused on arbuscular mycorrhizal (AM) fungi in soils and roots and examined their relationship with ecosystem multifunctionality under livestock grazing of Mongolian grasslands with different aridity levels. Above- and below-ground plant biomass were used to measure ecosystem-service multifunctionality, excluding annual plants that are unfavorable for ecosystem function and rangeland management. In both mountain forest steppe (mean annual precipitation = 207.7 mm) and steppe–desert steppe transition zone (mean annual precipitation = 128.4 mm), ecosystem multifunctionality was decreased by livestock grazing, as indicated by palatable plant shoot biomass. In line with the multifunctionality, the dominant plant species, Stipa krylovii, and AM plant biomass were decreased by livestock grazing. The Berger–Parker dominance index of soil AM fungi and Simpson’s diversity had a positive and negative relationship with multifunctionality, respectively, indicating that dominant AM fungi rather than AM fungal diversity in soil are key for maintaining multifunctionality. Root and soil AM fungal communities were significantly different with dominance of Rhizophagus operational taxonomic units (OTUs) in roots and Claroideoglomus OTUs in soil. However, the similarity between soil and root AM fungal communities increased with livestock grazing. Correlation analysis between palatable plant biomass and relative abundance of dominant AM fungal OTUs identified indicator virtual taxa that decreased (VTX00325 in roots, and VTX00165, VTX00214, and VTX00222 in soil) or increased (VTX00100, VTX00130, and VTX00295 in soil) with grazing intensity. The OTUs that were increased by grazing may be r-selected, grazing-tolerant AM fungi that accept a low C supply and supply few nutrients to plants. Our results suggest that grassland management focusing on ecosystem-service multifunctionality via control of AM plants, including S. krylovii and their co-dominant dominant AM fungi, in ungrazed grasslands are key for sustainable rangeland management in Mongolia.

Effect of arbuscular mycorrhizal fungi in roots on antioxidant enzyme activity in leaves of Robinia pseudoacacia L. seedlings under elevated CO2 and Cd exposure

Arbuscular mycorrhizal fungi (AMF) are easily influenced by increasing atmospheric CO2 concentration and heavy metals including cadmium (Cd), which can regulate antioxidant enzyme in host plants. Although the effect of AMF under individual conditions such as elevated CO2 (ECO2) and Cd on antioxidant enzyme in host plants has been reported widely, the effect of AMF under ECO2 + Cd receives little attention. In this study, a pot experiment was conducted to study the effect of AMF community in roots on superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities in leaves of 135-d Robinia pseudoacacia L. seedlings under ECO2 + Cd. The activities of SOD and CAT increased and POD activity and the richness and diversity of AMF community decreased under ECO2 + Cd relative to Cd alone. The richness and diversity of AMF were negatively related to Cd content in roots and leaves. The richness and OTUs of AMF community positively and AMF gene abundance negatively affected POD activity under the combined treatments. Superoxide dismutase and POD activities were negatively and positively related to Archaeospora and Scutellospora, respectively, under ECO2 + Cd. Cadmium in roots and leaves was negatively and significantly related to Glomus, Scutellospora, and Claroideoglomus abundance under ECO2 + Cd. Overall, AMF diversity and Archaeospora and Scutellospora in roots significantly influenced SOD, POD, and CAT activities. The response of AM symbiosis to ECO2 might regulate antioxidant capacity in host plants upon Cd exposure. Glomus, Scutellospora, and Claroideoglomus might be applied to phytoremediation of Cd-contaminated soils.

Ecological stoichiometry and fungal community turnover reveal variation among mycorrhizal partners in their responses to warming and drought.

Symbiotic fungi mediate important energy and nutrient transfers in terrestrial ecosystems. Environmental change can lead to shifts in communities of symbiotic fungi, but the consequences of these shifts for nutrient dynamics among symbiotic partners are poorly understood. Here, we assessed variation in carbon (C), nitrogen (N) and phosphorus (P) in tissues of arbuscular mycorrhizal (AM) fungi and a host plant (Medicago sativa) in response to experimental warming and drought. We linked compositional shifts in AM fungal communities in roots and soil to variation in hyphal chemistry by using high-throughput DNA sequencing and joint species distribution modelling. Compared to plants, AM hyphae was 43% lower in (C) and 24% lower in (N) but more than nine times higher in (P), with significantly lower C:N, C:P and N:P ratios. Warming and drought resulted in increases in (P) and reduced C:P and N:P ratios in all tissues, indicating fungal P accumulation was exacerbated by climate-associated stress. Warming and drought modified the composition of AM fungal communities, and many of the AM fungal genera that were linked to shifts in mycelial chemistry were also negatively impacted by climate variation. Our study offers a unified framework to link climate change, fungal community composition, and community-level functional traits. Thus, our study provides insight into how environmental change can alter ecosystem functions via the promotion or reduction of fungal taxa with different stoichiometric characteristics and responses.

Responses of Arbuscular Mycorrhizal Fungi Diversity and Community to 41-Year Rotation Fertilization in Brown Soil Region of Northeast China.

Arbuscular mycorrhizal fungi (AMF) play vital roles in the growth and development of plants, ecosystem sustainability, and stability in agroecosystem, such as transporting nutrients to host plants, improving soil physical structure, and enhancing the stress resistance of host plants. However, the effects of fertilization on AMF diversity and community in brown soil areas are still unclear. The purpose of this study is to explore changes in AMF diversity and community structures and finding out the factors that influenced the changes after 41 years of fertilization in brown soil. Samples were collected from five treatments of the long-term fertilization experiment in June 2019, including CK (no fertilizer), N (mineral nitrogen fertilizer), NP (mineral nitrogen and phosphate fertilizer), M (pig manure), and MNP (pig manure, mineral nitrogen, and phosphate fertilizer). Illumina HiSeq sequencing was used to determine AMF diversity and community structure. The relationship between AMF communities in soil and roots and environmental factors was analyzed by redundancy analysis. The results showed that the soil nutrient content of manure treatments was generally higher than that of chemical fertilizer treatments and no fertilizer treatment. Long-term fertilization increased AMF spore density, which increased with the increase of soil fertility. The moderate content of soil available phosphorus was beneficial to the colonization of AMF. AMF diversity in soil decreased with soil fertility, but AMF diversity in roots was influenced only by soil nitrate–nitrogen and pH. Glomus was the dominant genus in both soil and root samples. AMF community structure in soil and roots had a different response to long-term fertilization. Application of manure had a greater impact on AMF community structure in soil, whereas application of exogenous phosphate fertilizer had a greater impact on that in roots. Soil ammonium nitrogen, nitrate–nitrogen, total nitrogen, organic carbon, total potassium, and available potassium were the most important factors that influenced taxa of AMF in soil, whereas soil ammonium nitrogen, nitrate–nitrogen, total nitrogen, organic carbon, total potassium, available potassium, available phosphorus, and plant phosphorus and potassium content were the most important factors influencing taxa of AMF in maize roots under long-term fertilization in brown soil.

Molecular diversity of arbuscular mycorrhizal fungi associated with two alpine plant species in the Tibetan Plateau

Alpine ecosystem in the Tibetan Plateau has a special ecological environment, which may harbor a high richness of arbuscular mycorrhizal fungi (AMF) communities. To explore the molecular diversity of AMF community associated with plants in alpine grasslands, root and rhizosphere soil of two dominant plant species, Kobresia sp. and Leontopodium pusillum in Qinghai province, were studied by molecular biotechnology (clone library and sequencing) at five sites for each plant species. A total of 30 operational taxonomic units (OTUs) were identified, including seven families of Glomeromycota. Glomeraceae and Glo1 and Glo2 were most abundant at family and OUT level in roots respectively, while both Glomeraceae and Diversisporaceae were frequently present and Glo1 and Div1 were the most dominant OTUs in the soil. The AMF community was different in the roots and soil. Nineteen OTUs were identified in the roots of Kobresia sp., and 21 OTUs were identified in the rhizosphere soil. As to L. pusillum, fourteen OTUs were identified in roots and 17 OTUs in the soil. Specifically, three OTUs were only found in L. pusillum, and eight OTUs were only found in Kobresia sp. The root biomass and soil C/N ratio were the main factors affecting the AMF community in roots, whereas in soil, the important factors were root carbon content and shoot nitrogen content. These results showed a high diversity of AMF associated with the typical alpine plants, and distinct AMF community exist in roots and soil. Our results confirmed the importance of plant and soil factors in driving AMF assemblages in the fragile ecosystem of Tibetan Plateau.

Plant invasion alters community structure and decreases diversity of arbuscular mycorrhizal fungal communities

Invasive plants often pose serious threats to the natural biodiversity of invaded ecosystems and in this way are likely to alter ecosystem services. This applies to arbuscular mycorrhizal (AM) fungi, in which the invaders have been reported to modify community structure, which facilitates their further intrusion. Information as to the impact of such invasion on AM fungal communities is insufficient and therefore needed. In particular, little is known about how AM fungal communities shift in response to individual invasive species. To ascertain whether invasion changes the structure of indigenous AM fungal communities, we examined changes in AM fungal community composition and diversity in soil and in roots of native neighboring plants in response to incursion of five invasive plant species from the family Asteraceae: Conyza canadensis, Erigeron annuus, Echinops sphaerocephalus, Solidago canadensis, and Symphyotrichum novi-belgii. We found that invasions of tested invasive plant species altered composition of the AM fungal community and reduced the diversity of AM fungi in soil and in the roots of some native plants. Statistical significance of the invasions' effects depended on composition of AM fungal communities in roots of the native plant species and/or site and was not connected with changes in soil parameters. Our results confirm the notable influence of plant invasion on indigenous AM fungal biodiversity and the need for further study in various environmental conditions.

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

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

Effects of elevated CO2 on arbuscular mycorrhizal fungi associated with Robinia pseudoacacia L. grown in cadmium-contaminated soils

As symbionts capable of reciprocal rewards, arbuscular mycorrhizal fungi (AMF) can alleviate heavy metal toxicity to host plants and are easily influenced by elevated CO2 (ECO2). Although the individual effects of ECO2 and cadmium (Cd) on AMF have been widely reported, the response of AMF to ECO2 + Cd receives little attention. We evaluated the combined effects of ECO2 and Cd on AMF in the rhizosphere soil and roots of Robinia pseudoacacia L. seedlings. Under ECO2 + Cd relative to Cd, AMF gene copies and richness in rhizosphere soils increased (p < 0.05) and the diversity reduced (p < 0.05) at 4.5 mg Cd kg−1 dry soil; whereas root AMF abundance at 4.5 mg Cd kg−1 dry soil and the diversity and richness reduced (p < 0.05). Elevated CO2 caused obvious differences in the dominant genera abundance between rhizosphere soils and roots upon Cd exposure. Responses of C, water-soluble organic nitrogen (WSON), pH, and diethylene triamine penta-acetic acid (DTPA)-Cd in rhizosphere soils and root N to ECO2 shaped dominant genera in Cd-polluted rhizosphere soils. Levels of DTPA-Cd, WSON, C and pH in rhizosphere soils and C/N ratio, N, and Cd in roots to ECO2 affected (p < 0.05) dominant genera in roots under Cd exposure. AMF richness and diversity were lower in roots than in rhizosphere soils. Elevated CO2 altered AMF communities in rhizosphere soils and roots of R. pseudoacacia seedlings exposed to Cd. AMF associated with R. pseudoacacia may be useful/interesting to be used for improving the phytoremediation of Cd under ECO2.

Plant health status effects on arbuscular mycorrhizal fungi associated with Lavandula angustifolia and Lavandula intermedia infected by Phytoplasma in France

We investigated root communities of arbuscular mycorrhizal fungi (AMF) in relation to lavender (Lavandula angustifolia) and lavandin (Lavandula intermedia) health status from organic and conventional fields affected by Phytoplasma infection. The intensity of root mycorrhizal colonization was significantly different between diseased and healthy plants and was higher in the latter regardless of agricultural practice. This difference was more pronounced in lavender. The root AMF diversity was influenced by the plant health status solely in lavender and only under the conventional practice resulting in an increase in the AMF abundance and richness. The plant health status did not influence the distribution of root AMF communities in lavandin unlike its strong impact in lavender in both agricultural practices. Finally, among the most abundant molecular operational taxonomic units (MOTUs), four different MOTUs for each plant species were significantly abundant in the roots of healthy lavender and lavandin in either agricultural practice. Our study demonstrated that the plant health status influences root colonization and can influence the diversity and distribution of root AMF communities. Its effects vary according to plant species, can be modified by agricultural practices and allow plants to establish symbiosis with specific AMF species.

Changes in the mycorrhizal fungal community in host roots over five host generations under low and high phosphorus conditions

We tested whether arbuscular mycorrhizal fungal (AMF) community might shift as host plant generations advance under a low phosphorus (P) soil. Two greenhouse experiments were conducted using Medicago truncatula as the host plant, six AMF species, and two soil P levels. Experiment 1 assessed changes in AMF composition in roots and soil during five generations of host plant grown in low-P (5.7 mg kg−1) and high-P soil (24.0 mg kg−1). Experiment 2 tested the effects of single AMF species on host plant growth in low-P and high-P soil. Experiment 1 showed that AMF species composition at the OTU level in roots and soil significantly changed as host generations advanced, and that the pattern of change differed in low-P vs. high-P soil. In low-P soil, the dominant OTU in both roots and soil shifted from OTU-50 (Glomus tortuosum) to OTU-49 (Funneliformis geosporum) as host generations advanced. In high-P soil, the AMF community in roots and soil was dominated by OTU-50 in first two generations but OTU-49 and OTU-50 were co-dominant in the last three generations. Experiment 2 showed that mycorrhizal dependency indices based on plant biomass and P content in plant biomass, and spore numbers were higher in host plants with F. geosporum than other AMF fungal treatments in low-P soil. As the host M. truncatula grew in a low-P soil over five generations, AMF community in root and soil shifted to a composition with F. geosporum as dominant species who was effective in foraging for P.

Response of the arbuscular mycorrhizal fungi diversity and community in maize and soybean rhizosphere soil and roots to intercropping systems with different nitrogen application rates

Maize (Zea mays L.)/soybean (Glycine max L.) intercropping has been widely practiced in China, because of its effectiveness in improving crop yield and nitrogen utilization efficiency. However, the responses of indigenous arbuscular mycorrhizal fungal (AMF) diversity and communities in rhizosphere soil and roots to intercropping systems with different nitrogen application rates remain unclear. In this study, a field experiment was conducted with split-plot design, and AMF communities in crop rhizosphere soil and roots in monoculture and intercropping systems treated with different levels of nitrogen fertilization were investigated using Illumina MiSeq sequencing. Nitrogen fertilization significantly decreased the AMF alpha-diversity in maize rhizosphere soil, and no significant differences were observed between monocultured and intercropped maize. The Shannon index of soybean rhizosphere soil was significantly higher in intercropping treatments than in monoculture treatments for the corresponding nitrogen levels. The AMF diversity in the roots of maize showed different trends to those in the soil. The dominant genera in the present study were Glomus_f_Glomeraceae, Paraglomus, and Gigaspora, which occupied 55.52%, 9.18%, and 8.20% of the rhizosphere soil and 65.35%, 5.32%, and 17.16% of the roots, respectively. Our study showed that the abundance of the dominant genus, Glomus_f_Glomeraceae in maize soil and roots significantly increased in intercropping treatments compared with monoculture treatments, and it also increased with the increase in nitrogen application levels. In soybean soil and roots, the abundance of Glomus_f_Glomeraceae decreased with the increase in nitrogen application levels. The results of the redundancy and correlations analyses indicated that the changes in the AMF diversity and community in intercropping areas were significantly associated with alterations of the soil total nitrogen and alkali-hydrolysable nitrogen due to the interactions between maize and soybeans in intercropping systems with different nitrogen fertilizer application rates.