Rhizosphere Fungal Communities Research Articles

Elevations change fungal communities of the bulk soil, rhizosphere and root of Rhododendron delavayi Franch (Ericaceae) by affecting soil properties in a karst area, southwest China

ABSTRACT Rhododendron delavayi is a natural shrub with importance in preventing rocky desertification in the karst regions of Bijie city of China. The structure of fungal communities in bulk soil, rhizosphere and roots of R. delavayi at three elevations was analyzed by ITS2 amplicon sequencing. The results showed that the soil pH was highest at 1448 m, while the content of available phosphorus, total nitrogen and total phosphorus was lowest at 1821 m. The Shannon of fungal communities in bulk soil was higher than roots at 1448 m. Ascomycota and Basidiomycota were the most dominant phyla present in bulk soil, rhizosphere and root endophyte. The pH was positively related to Chytridiomycota and Glomeromycota in bulk soil at 1643 m. Ammonium-nitrogen significantly influenced the fungal communities in bulk soil, while the elevations impacted the diversity of fungal communities by affecting available phosphorus content in bulk soil and roots. In summary, elevation significantly affected the diversity and structure of fungal communities by affecting soil pH and nutrient levels, and the fungal communities helped R. delavayi in adaptating to different elevations.

Plant Performance and Soil Fungal Community Impacts of Enhancing Dioscorea opposita with Spraying Foliar Fertilizer with Different Nutrient Element Combinations

Foliar fertilization, an effective method to regulate plant nutrition has attracted much attention. In this study, the effects of different foliar fertilizers (F1: NPK formulation, F2: NPK+Fe-Mn-Zn formulation, F3: Fe-Mn-Zn formulation, and CK: deionized water) on plant growth, chemical composition, rhizosphere soil properties, and fungal community of Dioscorea opposita Thunb. were assessed by a field plot experiment. Rhizosphere fungal community was examined via Illumina MiSeq sequencing of ITS2 rRNA genes. Spraying foliar fertilizer directly affected the growth and chemical content of the plant, which depends on different foliar fertilizers. Ascomycota and Moraxella were the dominant fungal phyla. Nutrient elements were the main factors affecting fungal composition, and soil microelements positively influenced soil fungi, while soil macroelements negatively influenced soil fungi. Macroelement foliar fertilizer affected soil fungi by directly affecting the growth parameters and macroelement content of the plant or by directly affecting soil properties, while microelement foliar fertilizer affected soil fungi by directly affecting the microelement content of the plant or by directly affecting the soil pH and organic matter content. These factors were involved in the formation of a “leaf-root-soil microbe” conduction system similar to the “brain-gut-microbe” axis. Our results provide a basis for the application of foliar fertilizer in the cultivation of medicinal plants.

Analysis of microbial diversity and community structure of rhizosphere soil of Cistanche salsa from different host plants.

Host plants influence rhizosphere microorganism composition through root secretions, and rhizosphere associated microorganisms influence Cistanche seeds germination. At present, little is known about effects of different host plants on soil bacteria and fungi in the rhizosphere of Cistanche salsa. High-throughput sequencing was used here to reveal the similarities and differences in the structural composition of the soil microbial community of C. salsa from six host plants (i.e., Halocnemum strobilaceum, Atriplex patens, Kalidium foliatum, Caroxylon passerinum, Anabasis aphylla, Krascheninnikovia ceratoides). We discovered that Krascheninnikovia ceratoides-parasitizing C. salsa (YRCR6) had the highest diversity of rhizosphere bacterial communities, and Anabasis aphylla -parasitizing C. salsa (YRCR5) had the highest diversity of rhizosphere fungal communities. Fungal communities were more influenced by the host plant than bacterial communities. In addition, we discovered certain rhizosphere microorganisms that may be associated with Cistanche seeds germination, including Mortierella, Aspergillus alliaceus, and Cladosporium, which are account for a relatively high proportion in Halocnemum strobilaceum, Atriplex patens and Anabasis aphylla -parasitizing C. salsa. Redundancy analysis results also revealed that AP, HCO3–, pH, Ca2+, SO42–, and K+ had a highly significant impact on the bacterial community structure (P < 0.01), while pH and SO42– had a significant impact on the fungal community structure (P < 0.05). Conclusively, differences were noted in the structure of rhizosphere bacterial and fungal communities of C. salsa parasitizing different plants in the same habit and the difference may be related to the host plant. This result can provide a new ideas for the selection of host plants and the cultivation of C. salsa.

Limited effect of thermal pruning on wild blueberry crop and its root-associated microbiota.

Thermal pruning was a common pruning method in the past but has progressively been replaced by mechanical pruning for economic reasons. Both practices are known to enhance and maintain high yields; however, thermal pruning was documented to have an additional sanitation effect by reducing weeds and fungal diseases outbreaks. Nevertheless, there is no clear consensus on the optimal fire intensity required to observe these outcomes. Furthermore, fire is known to alter the soil microbiome as it impacts the soil organic layer and chemistry. Thus far, no study has investigated into the effect of thermal pruning intensity on the wild blueberry microbiome in agricultural settings. This project aimed to document the effects of four gradual thermal pruning intensities on the wild blueberry performance, weeds, diseases, as well as the rhizosphere fungal and bacterial communities. A field trial was conducted using a block design where agronomic variables were documented throughout the 2-year growing period. MiSeq amplicon sequencing was used to determine the diversity as well as the structure of the bacterial and fungal communities. Overall, yield, fruit ripeness, and several other agronomical variables were not significantly impacted by the burning treatments. Soil phosphorus was the only parameter with a significant albeit temporary change (1 month after thermal pruning) for soil chemistry. Our results also showed that bacterial and fungal communities did not significantly change between burning treatments. The fungal community was dominated by ericoid mycorrhizal fungi, while the bacterial community was mainly composed of Acidobacteriales, Isosphaerales, Frankiales, and Rhizobiales. However, burning at high intensities temporarily reduced Septoria leaf spot disease in the season following thermal pruning. According to our study, thermal pruning has a limited short-term influence on the wild blueberry ecosystem but may have a potential impact on pests (notably Septoria infection), which should be explored in future studies to determine the burning frequency necessary to control this disease.

Changes in phosphorus mobilization and community assembly of bacterial and fungal communities in rice rhizosphere under phosphate deficiency.

Rhizosphere microorganisms are closely associated with phosphorus (P) uptake in plants and are considered potential agents to mitigate P shortage. However, the mechanisms of rhizospheric microbial community assembly under P deficiency have yet to be elucidated. In this study, bacterial and fungal communities in rice rhizosphere and their P mobilization potential under high (+P) and low (−P) concentrations of P were investigated. Bacterial and fungal community structures were significantly different between −P and +P treatments. And both bacterial and fungal P-mobilizing taxa were enriched in-P treatment; however, the proportion of P-mobilizing agents in the fungal community was markedly greater than that in the bacterial community. A culture experiment confirmed that microbial phosphate solubilizing capacity was significantly higher in −P treatment compared with that in +P treatment. −P treatment lowered bacterial diversity in rice rhizosphere but increased fungal diversity. Further analysis demonstrated that the contribution of deterministic processes in governing bacterial community assembly was strengthened under P deficiency but was largely weakened in shaping the fungal community. These results highlighted that enriching P-mobilizing microbes in the rhizosphere is a vital way for rice to cope with P deficiency, and that fungi contribute considerably to P mobilization in rice rhizosphere. Findings from the study provide novel insights into the assembly of the rhizosphere microbiome under P deficiency and this will facilitate the development of rhizosphere microbial regulation strategies to increase nutrient uptake in plants.

Changes in Fungal and Oomycete Community Composition Following Irrigation Reductions Aimed at Increasing Water Use Efficiency in a Containerized Nursery Crop

Ornamental production in the United States spans an estimated 267,000 ha and uses approximately 169,000 m3 of water yearly. Ornamental growers, particularly those with air-closed systems, are interested in implementing reduced irrigation technologies such as sensor-controlled irrigation systems to improve water use efficiency in response to water scarcity. To evaluate phytobiome impacts, we utilized an Illumina metabarcoding approach to characterize changes in fungal and oomycete rhizosphere communities of commercially grown poinsettia, complementing previous studies of single-pathogen impacts. Minor reductions (from 54 to 50% volumetric water content [VWC]) did not have large effects on rhizosphere fungal community structure but shifts in plant health status (symptomatic to asymptomatic) correlated with shifts in fungal diversity and evenness, with an increased abundance of several taxa, including Plectosphaerella cucumerina and Fusarium spp., in symptomatic plants. Further reductions in irrigation (45, 35, and 25% VWC) did not affect overall fungal community composition but the lowest VWC increased the abundance of potential root rot pathogens such as Phoma multirostrata and Plectosphaerella cucumerina. Reduced irrigation volumes decreased oomycete diversity and abundance of several known pathogens in the Phytophthora genus. Addition of a bacterial product (Companion) with putative pathogen-suppressive and drought-tolerance enhancing effects had no influence on fungal community composition or abundance but did increase abundance of some oomycete species at 45% VWC. This study shows that adoption of reduced irrigation may have greater effects on fungal versus oomycete taxa in the system, with consistent patterns of fungal enhancement, including putative fungal pathogens and beneficial organisms, and oomycete suppression.

Compartment and Plant Identity Shape Tree Mycobiome in a Subtropical Forest.

ABSTRACTDeciphering the relationships between microbes and their host plants is critical for a better understanding of microbial diversity maintenance and community stability. Here, we investigated fungal diversity and community assembly in the phyllosphere and rhizosphere of 13 tree species in a subtropical common-garden experiment. The results showed that fungal community structures significantly differed across compartments (leaf, root, and soil) and different tree species. Higher α-diversity was observed in the phyllosphere than in the roots and rhizospheric soil. Fungal community composition (β-diversity) was significantly affected by both compartment and species identity. The fungal community compositions were significantly correlated with soil pH in the roots and the soils as well as with soil nitrate and leaf total phosphorus in the leaves. We found that fungal community assemblies were mainly driven by deterministic processes, regardless of compartments. Moreover, host preference analyses indicated that stronger plant/fungus preferences occurred in leaves than in roots and soils. Our results highlight the differences in tree mycobiome between aboveground and belowground compartments and have important implications for the promotion of biodiversity conservation and management sustainability for the subtropical forest.IMPORTANCE Subtropical mountain forests are widely distributed in Southern China and are characterized by high biodiversity. The interactions between plants and fungi play pivotal roles in biodiversity maintenance and community stability. Nevertheless, knowledge of fungal diversity and of the community assembly patterns of woody plants is scarce. Here, we investigated fungal diversity and community assembly in the phyllosphere and rhizosphere of 13 tree species in a common-garden experiment. We found that both compartment and plant identity influenced fungal diversity, community, and guild compositions, while deterministic processes mainly governed the fungal community assembly, especially in the rhizospheric fungal communities. Our results demonstrate that tree leaves represent stronger host/fungi preferences than do roots and soils. Together, our findings enhance the understanding of the roles of compartment and plant identity in structuring fungal communities as well as promote fungal diversity maintenance in subtropical mountain forest ecosystems.

Contrasting Responses of Rhizosphere Fungi of Scutellaria tsinyunensis, an Endangered Plant in Southwestern China.

ABSTRACTScutellaria tsinyunensis is an endangered species in southwest China, distributed sporadically in mountainous areas at an elevation of approximately 200 to 900 m. Rhizosphere soil properties and fungal communities play critical roles in plant survival and expansion. Nevertheless, understanding of soil properties and fungal communities in the S. tsinyunensis distribution areas is extremely limited. The present study examined soil properties and fungal communities in nearly all extant S. tsinyunensis populations at two altitudinal gradients (low and high groups). Our findings indicated that soil characteristics (i.e., soil pH, water content, and available phosphorus) were affected distinctively by altitudes (P < 0.05). In addition, the low altitude group harbored higher fungal richness and diversity than the high altitude. Co-occurrence network analysis identified six key genera that proved densely connected interactions with many genera. Further analysis represented that the low altitude group harbored three beneficial genera belonging to Ascomycota (Archaeorhizomyces, Dactylella, and Helotiales), whereas the high altitude showed more pathogenic fungi (Apiosporaceae, Colletotrichum, and Fusarium). Correlation analysis found that soil water content was highly correlated with Hydnodontaceae and Lophiostoma. Besides, plants’ canopy density was negatively correlated with four pathogenic fungi, indicating that the high abundance of the pathogen at high altitudes probably inhibited the survival of S. tsinyunensis. To sum up, this comprehensive analysis generates novel insights to explore the contrasting responses of S. tsinyunensis rhizosphere fungal communities and provides profound references for S. tsinyunensis habitat restoration and species conservation.IMPORTANCE Our study highlighted the importance of rhizosphere fungal communities in an endangered plant, S. tsinyunensis. Comparative analysis of soil samples in nearly all extant S. tsinyunensis populations identified that soil properties, especially soil water content, might play essential roles in the survival and expansion of S. tsinyunensis. Our findings proved that a series of fungal communities (e.g., Archaeorhizomyces, Dactylella, and Helotiales) could be essential indicators for S. tsinyunensis habitat restoration and protection for the first time. In addition, further functional and correlation analyses revealed that pathogenic fungi might limit the plant expansion into high altitudes. Collectively, our findings displayed a holistic picture of the rhizosphere microbiome and environmental factors associated with S. tsinyunensis.

Molecular characterization of Deciphering Fungal Community structure in Zea mays L. and Triticum Aestivum L

Rhizosphere fungi are strongly associated with plant growth and health by providing nutrients and antagonizing pathogens. Commercially, fungus has multipurpose applications in several sectors including beverages, food items and in medicines. Current study aimed to reveal the core fungal community structure of the two leading cereal crops that are Zea mays L. and Triticum aestivum L. The rhizosphere fungal community was explored via morphology, biochemistry and internal transcribe spacer (ITS) metagenomics. On the basis of morphology, the retrieved fungal strains were imprecisely classified into Ascomycota and Zygomycota. The species including Yeast, Botyritis californica, Rhizopus stolonifer, Alternaria tenuissima, Aspergillus terreus, Aspergillus flavus, Aspergillus nidulans, Aspergillus niger and Microsporum canis were identified on the basis of macroscopy and microscope. Moreover, the biochemical characterization depicted the role of fungi in promotion of plant growth. Majority of the isolates depicted catalase activity, indole production, phosphate solubilization, ammonia production, nitrogenase activity and urease activity. Metagenomics using amplicon sequencing of ITS region revealed the presence of 805 Operational Taxonomic Units (OTUs) with 647 OTUs in Zea mays and 620 OTUs in Triticum aestivum. The fungal phyla found in the rhizosphere of Zea mays L. and Triticum aestivum L. were Ascomycota, Basidiomycota, Zygomycota, Chytridiomycota, Incertae sedis fungi. Ascomycota accounted for 93% and 95% of classified fungi in rhizosphere of Zea mays L. and Triticum aestivum L. respectively. The dominant species found in the rhizosphere soil of Zea mays were Gibberella intricans, Curvularia lunata, Lepidosphaeria nicotiae, Edenia gomezpompae and Myrothecium verrucaria.

Optimal NPK Fertilizer Combination Increases Panax ginseng Yield and Quality and Affects Diversity and Structure of Rhizosphere Fungal Communities.

Soil microorganisms affect crop rhizospheres via the transformation and transport of nutrients, which has important influences on soil fertility, carbon sequestration, and plant yield and health in agroecosystems. There are few reports on the effects of fertilizer application on the growth of Panax ginseng (C. A. Mey.) or the structure of its rhizosphere microbial communities. In this study, an orthogonal experimental design was used to explore the effects of nine different combinations of nitrogen (N), phosphorus (P), and potassium (K) fertilizers with different amounts and proportions on ginseng growth and accumulation of ginsenosides and the structure of rhizosphere soil fungal communities. Soil without fertilization was the control. With the combined application of NPK, ginseng growth and development increased. The fertilization scheme N3P1K3, with N fertilizer at 50 g·m−2, P fertilizer at 15 g·m−2, and K fertilizer at 60 g·m−2, had the most comprehensive benefit and significantly increased ginseng rhizome biomass and ginsenoside contents (Rg1, Re, Rf, Rg2, Rb1, Ro, Rc, Rb2, Rb3, and Rd). Amplicon sequencing showed that NPK application increased the diversity of fungal communities in ginseng rhizospheres, whereas richness was bidirectionally regulated by proportions and amounts of NPK. Ascomycota was the dominant fungal phylum in ginseng rhizosphere soil, and relative abundances decreased with combined NPK application. Combined NPK application increased the relative abundance of potential beneficial fungi, such as Mortierella, but decreased that of potentially pathogenic fungi, such as Fusarium. Correlation analysis showed that potential beneficial fungi were significantly positively correlated with ginseng rhizome yield and ginsenoside contents, whereas the opposite relation was observed with potential pathogenic fungi. Thus, in addition to directly increasing crop growth, precise NPK application can also increase crop adaptability to the environment by shaping specific microbial communities. The results of this study suggest that the combined effects of biotic and abiotic processes on agricultural production determine crop yield and quality.

High-throughput sequencing reveals rhizosphere fungal community composition and diversity at different growth stages of Populus euphratica in the lower reaches of the Tarim River.

BackgroundPopulus euphratica is one of the most ancient and primitive tree species of Populus spp and plays an important role in maintaining the ecological balance in desert areas. To decipher the diversity, community structure, and relationship between rhizosphere fungi and environmental factors at different growth stages of P. euphratica demands an in-depth investigation.MethodsIn this study, P. euphratica at different growth stages (young, medium, overripe, and decline periods) was selected as the research object, based on the determination of the physicochemical properties of its rhizosphere soil, the fungal community structure and diversity of P. euphratica and their correlation with soil physicochemical properties were comprehensively analyzed through high-throughput sequencing technology (internal transcribed spacer (ITS)) and bioinformatics analysis methods.ResultsAccording to the analysis of OTU annotation results, the rhizosphere soil fungal communities identified in Populus euphratica were categorized into10 phyla, 36 classes, 77 orders, 165 families, 275 genera and 353 species. The alpha diversity analysis showed that there was no obvious change between the different growth stages, while beta diversity analysis showed that there were significantly differences in the composition of rhizosphere soil fungal communities between mature and overripe trees (R2 = 0.31, P = 0.001), mature and deadwood (R2 = 0.28, P = 0.001). Ascomycota and Basidiomycota were dominant phyla in the rhizosphere fungal community and the dominant genera were Geopora, Chondrostereum and unidentified_Sordariales_sp. The relative abundance of the top ten fungi at each classification level differed greatly in different stages. Canonical correspondence analysis (CCA) and Spearman’s correlation analysis showed that conductivity (EC) was the main soil factor affecting the composition of Populus euphratica rhizosphere soil fungal community (P < 0.01), followed by total dissolvable salts (TDS) and available potassium (AK) (P < 0.05).ConclusionsOur data revealed that the rhizosphere fungal communities at the different growth stages of P. euphratica have differences, conductivity (EC) was the key factor driving rhizosphere fungi diversity and community structure, followed by total dissolvable salts (TDS) and available potassium (AK).

Phosphate mining activities affect crop rhizosphere fungal communities

Phosphate mining releases heavy metals into the surrounding environment. In this study, the effects of phosphate mining on rhizosphere soil fungi in surrounding crops, including Lactuca sativa var. angustata, Glycine max (L.) Merr., and Triticum aestivum L., were assessed. Phosphate mining significantly reduced the crop rhizosphere fungal diversity (P < 0.05). The relative abundances of Fusarium and Epicoccum increased in mining rhizosphere soil compared with the baseline. Beta diversity analysis indicated that phosphate mining led to the differentiation of fungal community structure in plant rhizospheres. Guild analysis indicated that different plant rhizosphere fungi developed various guilds in response to phosphate mining stress. Nine fungi were isolated from soil samples, with solubilization index values ranging from 1.1 to 2.5. Two efficient phosphate solubilizers, Epicoccum nigrum and Fusarium verticillioides, were enriched in phosphate mining rhizosphere soil samples. The dissolution kinetics of inorganic phosphorus and alkaline phosphatase activity assay showed strong phosphorus dissolution ability of the isolated fungi. Penicillium aculeatum, Trichoderma harzianum, Chaetomium globosum, and F. verticillioides showed strong tolerance to multiple heavy metals. This study furthers our understanding of how rhizosphere fungal ecology is affected by phosphate mining and provides important resources for the remediation of phosphate mining soil pollution.

Bacterial but Not Fungal Rhizosphere Community Composition Differ among Perennial Grass Ecotypes under Abiotic Environmental Stress.

ABSTRACTEnvironmental change, especially frequent droughts, is predicted to detrimentally impact the North American perennial grasslands. Consistent dry spells will affect plant communities as well as their associated rhizobiomes, possibly altering the plant host performance under environmental stress. Therefore, there is a need to understand the impact of drought on the rhizobiome, and how the rhizobiome may modulate host performance and ameliorate its response to drought stress. In this study, we analyzed bacterial and fungal communities in the rhizospheres of three ecotypes (dry, mesic, and wet) of dominant prairie grass, Andropogon gerardii. The ecotypes were established in 2010 in a common garden design and grown for a decade under persistent dry conditions at the arid margin of the species’ range in Colby, Kansas. The experiment aimed to answer whether and to what extent do the different ecotypes maintain or recruit distinct rhizobiomes after 10 years in an arid climate. In order to answer this question, we screened the bacterial and fungal rhizobiome profiles of the ecotypes under the arid conditions of western Kansas as a surrogate for future climate environmental stress using 16S rRNA and ITS2 metabarcoding sequencing. Under these conditions, bacterial communities differed compositionally among the A. gerardii ecotypes, whereas the fungal communities did not. The ecotypes were instrumental in driving the differences among bacterial rhizobiomes, as the ecotypes maintained distinct bacterial rhizobiomes even after 10 years at the edge of the host species range. This study will aid us to optimize plant productivity through the use of different ecotypes under future abiotic environmental stress, especially drought.IMPORTANCE In this study, we used a 10-year long reciprocal garden system, and reports that different ecotypes (dry, mesic, and wet) of dominant prairie grass, Andropogon gerardii can maintain or recruit distinct bacterial but not fungal rhizobiomes after 10 years in an arid environment. We used both 16S rRNA and ITS2 amplicons to analyze the bacterial and fungal communities in the rhizospheres of the respective ecotypes. We showed that A. gerardii might regulate the bacterial community to adapt to the arid environment, in which some ecotypes were not adapted to. Our study also suggested a possible tradeoff between the generalist and the specialist bacterial communities in specific environments, which could benefit the plant host. Our study will provide insights into the plant host regulation of the rhizosphere bacterial and fungal communities, especially during frequent drought conditions anticipated in the future.

Effects of Meloidogyne incognita on the fungal community in tobacco rhizosphere

The often widespread and serious Root-Knot Nematode (RKN) disease is an important soil-borne disease affecting tobacco production. This study aimed to understand micro-ecological changes caused by RKN disease and interactions between disease and rhizosphere soil fungal communities. The 18S rRNA gene sequencing was used to study changes in rhizosphere fungal community of tobacco plants having RKN disease. In June 2018, a paired comparison was performed between rhizosphere fungal community structures of healthy tobacco plants and those with RKN disease [...]

Mineral and Organic Fertilizers Distinctly Affect Fungal Communities in the Crop Rhizosphere

Fungi represent a diverse group of organisms that play an essential role in maintaining soil health and ecosystem functioning. Plant root exudates form nutrient-rich niches that harbor specific fungal communities, or so-called rhizosphere mycobiomes. The long-term application of fertilizers supplies the soil with nutrients that may override the plant-related effects on rhizosphere fungal communities. Here, we assessed the effect of contrasting fertilization regimes on the composition, diversity, and abundance of bulk soil and rhizosphere mycobiomes of potato, white mustard, and maize under NPK (mineral fertilizers) or fresh cattle manure (organic fertilizers). Mineral and organic fertilizers led to distinct fungal communities in the rhizospheres of all studied crops, and the plant-related effects on the mycobiome were overridden by the effect of fertilization. The abundances of Ascomycota and Olpidiomycota were higher under manure, while the abundances of Basidiomycota and Monoblepharomycota increased under NPK. Manure input strongly increased fungal abundance but decreased fungal diversity and the total number of species. NPK had a slight effect on fungal diversity, but significantly increased the relative abundances of fungal phytopathogens, such as Alternaria and Fusarium. Our study shows that that potential plant species effects on the abundance and diversity of the rhizosphere mycobiomes are governed by long-term fertilization. Fertilization management could therefore be used to manipulate rhizosphere fungal communities and soilborne pathogen suppressiveness.

Diversity and spatiotemporal dynamics of fungal communities in the rhizosphere soil of Lycium barbarum L.: a new insight into the mechanism of geoherb formation

Lycium barbarum L. is a well-known traditional geoherb in Ningxia, China. The fruits of L. barbarum contain several dietary constituents, and thus, they exert many beneficial effects on human health. However, a few studies have been conducted on the geoherb L. barbarum and its rhizosphere soil fungal community. In this study, we determined the physicochemical properties and fungal community structure of rhizosphere soil of L. barbarum from three regions of China, namely Ningxia (NX), Qinghai (QH), and Xinjiang (XJ), during three development stages of L. barbarum. Soil pH varied between 7.56 and 8.60 across the three regions, indicating that alkaline soil is conducive to the growth of L. barbarum. The majority of soil properties in NX, an authentic geoherb-producing area, were substantially inferior to those in XJ and QH during all three developmental stages. Total sugar, polysaccharide (LBP), and flavonoid contents were the highest in wolfberry fruits from NX. High-throughput sequencing showed that the abundance of the soil fungal population in NX was higher than that in QH and XJ during the flowering and fruiting stage and summer dormant stage. Moreover, the soil fungal diversity increased with the development of wolfberry. Ascomycota and Mortierellomycota were the predominant phyla in the rhizosphere fungal communities in all samples. Redundancy analysis showed a significant correlation of the soil-available phosphorus and LBP of wolfberry fruits with the fungal community composition. The characteristics of rhizosphere fungal communities determined in the present study provide insights into the mechanism of geoherb formation in NX wolfberry.

Impacts of continuous and rotational cropping practices on soil chemical properties and microbial communities during peanut cultivation

Long-term monocultures have severely inhibited the cultivation of Chinese peanut (Arachis hypogaea L.). In this study, the effects of continuous cropping on soil chemical properties and microbial communities were investigated in peanut fields that had been in crop rotation for 10 years and in monoculture for 10 years. The results found that long-term monoculture increased the activities of available potassium, available phosphorus, available nitrogen, soil organic matter, urease, acid phosphatase and catalase; while decreasing the activity of catalase. The diversity and abundance of soil bacteria and fungi is higher under continuous peanut cultivation. At the genus level, the relative abundance of potentially beneficial microflora genera was higher in the rhizosphere soil of rotational cropping than in continuous cropping, while the opposite was true for the relative abundance of potentially pathogenic fungal genera. Principal coordinates and cluster analysis indicated that continuous cropping altered the structure of the microbial community. The results of the functional predictions showed significant differences in the functioning of the rhizosphere microbial community between continuous and rotational cropping. In conclusion, long-term continuous cropping changed the chemical properties of the soil, altered the structure and function of the soil bacterial and fungal communities in peanut rhizosphere, which to some extent reduced the relative abundance of potentially beneficial microbial genera and increased the relative abundance of potentially pathogenic fungal genera, thus increasing the potential risk of soil-borne diseases and reducing the yield and quality of peanut. Therefore, in the actual production process, attention should be paid not only to the application of chemical fertilizers, but also to crop rotation and the application of microbial fertilizers.

Plastic mulch film residues in agriculture: impact on soil suppressiveness, plant growth, and microbial communities.

Plastic mulch film residues have been accumulating in agricultural soils for decades, but so far, little is known about its consequences on soil microbial communities and functions. Here, we tested the effects of plastic residues of low-density polyethylene and biodegradable mulch films on soil suppressiveness and microbial community composition. We investigated how plastic residues in a Fusarium culmorum suppressive soil affect the level of disease suppressiveness, plant biomass, nutrient status, and microbial communities in rhizosphere using a controlled pot experiment. The addition of 1% plastic residues to the suppressive soil did not affect the level of suppression and the disease symptoms index. However, we did find that plant biomasses decreased, and that plant nutrient status changed in the presence of plastic residues. No significant changes in bacterial and fungal rhizosphere communities were observed. Nonetheless, bacterial and fungal communities closely attached to the plastisphere were very different from the rhizosphere communities with overrepresentation of potential plant pathogens. The plastisphere revealed a high abundance of specific bacterial phyla (Actinobacteria, Bacteroidetes, and Proteobacteria) and fungal genera (Rhizoctonia and Arthrobotrys). Our work revealed new insights and raises emerging questions for further studies on the impact of microplastics on the agroecosystems.

Impacts of Continuous Cropping on Fungal Communities in the Rhizosphere Soil of Tibetan Barley.

Microbial community structures and keystone species play critical roles in soil ecological processes; however, their responses to the continuous cropping of plants are virtually unknown. Here, we investigated the community dynamics and keystone species of fungal communities in the rhizosphere soils of continuously cropped Tibetan barley (a principal cereal cultivated on the Qinghai–Tibetan Plateau). We found that the Chao1 and Phylogenetic Diversity (PD) indices decreased with increased cropping years. The relative abundance of the genera Cystofilobasidium, Mucor, and Ustilago increased with the extension of continuous cropping years, whereas Fusarium showed the opposite pattern. Furthermore, long-term monocropped Tibetan barley simplified the complexity of the co-occurrence networks. Keystone operational taxonomic units (OTUs) changed with continuous cropping, and most of the keystone OTUs belonged to the phylum Ascomycota, suggesting their important roles in rhizosphere soil. Overall, this study revealed that the continuous cropping of Tibetan barley impacted both on the richness, phylogenetic diversity, and co-occurrence network of fungal community in the rhizosphere. These findings enhance our understanding of how rhizosphere fungal communities respond to monocropped Tibetan barley.

Soil Fungal Community Composition and Diversity of Culturable Endophytic Fungi from Plant Roots in the Reclaimed Area of the Eastern Coast of China.

As an important resource for screening microbial strains capable of conferring stress tolerance in plants, the fungal community associated with the plants grown in stressful environments has received great attention. In this study, high-throughput sequencing was employed to study the rhizosphere fungal community in the reclaimed area (i.e., sites F, H, and T) of the eastern coast of China. Moreover, endophytic fungi from the root of six plant species colonizing the investigated sites were isolated and identified. The differences in soil physicochemical parameters, fungal diversity, and community structure were detected among the sampling sites and between the seasons. Ectomycorrhizal (ECM) fungi (e.g., genera Tuber and Geopora) were dominant at site F, which was characterized by high soil total carbon (SC) and total nitrogen (SN) contents and low soil electrical conductivity (EC) value. Arbuscular mycorrhizal (AM) fungi, including genera Glomus, Rhizophagus, and Entrophospora were dominant at sites H (winter), H (summer), and T (summer), respectively. The positive relationship between the EC value and the abundance of genus Glomus indicated the ability of this AM fungus to protect plants against the salt stress. Endophytic fungi at sites F (Aspergillus and Tetracladium), H (Nigrospora), and T (Nigrospora, Coniochaeta and Zopfiella) were recognized as the biomarkers or keystone taxa, among which only genus Aspergillus was isolated from the plant roots. The aforementioned AM fungi and endophytic fungi could contribute to the promotion of plant growth in the newly reclaimed land.