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Despite the abundance of studies on the interactions between dark septate endophytes (DSEs) and host plants, little is known about the effects elicited by different DSE species and inoculum levels, especially in desert plants. Here, we examined the colonization status and species composition of DSEs in roots of Hedysarum scoparium, a xerophyte plant endemic to arid desert, northwest China. Subsequently, we assessed the performance of host plants inoculated with Paraphoma chlamydocopiosa and Alternaria doliconidium under different inoculum levels. DSE colonization was characterized by spatial and interannual variability, and hyphal colonization was dominant (17.2%–76.7%). Alternaria doliconidium, Edenia gomezpompae, Paraphoma pye, Subramaniula flavipila and Herpotrichia striatispora are reported here in desert ecosystems for the first time. Both P. chlamydocopiosa and A. doliconidium established positive symbiosis with H. scoparium, however, the growth-promoting effects differed significantly depending on the DSE species and inoculum level (P

Despite desert ecosystem being crucial to our understanding of natural geography, species evolution and global climate change, there is limited information on the dynamics of their composition and the diversity of endophytic fungi communities driven by plant identity and organ differentiation. Here, an extensive investigation of endophytic fungal microbiome in root, stem, and leaf organs associated with five xerophyte shrubs in an extremely arid desert, Northwest China, were examined. The fungal community dominated by Dothideomycetes and Pleosporales. Shrub species strongly drive the niche-based processes of endophytic fungi across the root, stem and leaf compartments. The diversity and composition of endophytic fungi in stem showed higher variability among plant species than leaf and root. The fungal communities in root libraries were more diverse and exhibited a remarkable differentiation of community composition. We further demonstrated the significant host preferences and tissue specificity of desert endophytic fungi, and unique specific taxa were also observed. The co-occurrence network revealed the coexistence of fungal endophytes in arid desert, and the root fungal network harbored the highest interspecies connectivity. Members of Pleosporales were the most common keystone species in the root fungal network. This is the first report of mycobiota in both plant species and organ differentiation in an extremely arid desert ecosystem.

Background: Desert shrubs represent high productivity and play essential roles in maintaining the biodiversity and stability of ecosystem functioning in arid desert ecosystems. These xerophytic plants provide specific biotic and abiotic conditions for the resident specialist microorganisms. However, a robust understanding of the structural composition of the fungal microbiome associated with desert plants and especially the relationship between above- and belowground communities is currently lacking. In this study, we examined the endophytic fungal communities associated with the root, stem, and leaf tissues of five desert shrubs using Illumina MiSeq sequencing of internal transcribed spacer 2 (ITS2) sequences.Results: A total of 337 operational taxonomic units (OTUs) of endophytic fungi were identified at a 97% sequence similarity level. Pleosporales were dominant and played an irreplaceable role as keystone species in maintaining the connectivity and complexity of the fungal networks. Desert shrub identity significantly affected the community composition of the endophytic fungi in different tissues. Compared with the fungi in the aboveground tissues, root-associated fungi represented the most abundant reservoir of biodiversity in the desert habitat and displayed significantly high tissue specificity. Interestingly, the aboveground stems and leaves showed higher taxonomic overlap with underground root tissues than with each other. The root fungal network revealed the highest connectivity, and the interspecies relationships between desert fungal OTUs revealed a high percentage of co-presence rather than mutual exclusion. In addition, members of Hypocreales played a central role in connecting the above- and belowground fungal networks.Conclusions: This study represents the first example of research revealing plant-fungus endophytic associations in an extremely arid desert ecosystem with the simultaneous consideration and comparison of above- and belowground niches. Understanding the complex host-microbe interactions associated with desert plants could provide a basis for the exploitation of plant-fungus associations in the manipulation of the shrub microbiome for ecological restoration purposes.

Background: Fungal endophytes can improve plant tolerance to abiotic stress, however, the role of these plant–fungal interactions in desert species ecology and their management implications remain unclear. This study aimed to assess whether dark septate endophytes (DSE) can shift the performance of Artemisia ordosica and associated soil microbial community under salt stress.Methods: We investigated the effects of three DSE (Alternaria chlamydosporigena [AC], Paraphoma chrysanthemicola [PC] and Bipolaris sorokiniana [BS]) isolated from desert habitats on plant morphology, physiology and rhizosphere soil microhabitat of Artemisia ordosica seedlings under different NaCl concentrations (0 %, 0.1 %, 0.2 %, and 0.3 %) in a growth chamber. Results: Three DSE strains could colonize the roots of A. ordosica, and the symbiotic response with host plants depended on DSE species and NaCl concentration. The greatest benefits associated with DSE occurred under 0.1 % NaCl. Specifically, AC improved root morphology, and increased total biomass and superoxide dismutase (SOD) activity; PC increased root morphology, root biomass, and glutathione (GSH) and indoleacetic acid (IAA) contents; and BS promoted SOD activity and GSH and IAA contents. DSE reduced the root Na+ content. Interestingly, BS promoted gram-positive (G +) and gram-negative (G −) bacteria under 0.1 % NaCl and the abundance of AM fungi under 0.2 % and 0.3 % NaCl. PC positively affected fungi, AM fungi, G − bacteria and actinomycetes under 0.2 % and 0.3 % NaCl, while AC increased the abundance of all examined microbes under 0.3 % NaCl. A structural equation modeling (SEM) demonstrated that DSE not only positively affects A. ordosica performance but also directly or indirectly impacts soil microbes by regulating the soil organic carbon (SOC), available phosphorus (AP), and alkaline nitrogen (AN) content.Conclusions: DSE isolated from A. ordosica enhanced the root development of host plants and altered the soil nutrient content and soil microbiota under different NaCl concentrations, possibly contributing to plant growth and ecological adaptability under saline environment. These results contribute to the understanding of the ecological function of DSE in desert ecosystems and may be used to promote vegetation restoration in salinized desert areas.

Dark septate endophytes (DSE) are diverse facultative biotrophic ascomycetes that ubiquitously colonise plant roots and may facilitate plant growth and productivity. However, the relationship between DSE resources and medicinal plants is still unclear. Here, we investigated DSE colonisation and species composition associated with roots of 25 medicinal plants collected from Anguo Medicine Planting Site in the farmland habitat, northern China in May 2017 using morphological characteristics and ITS sequencing. Typical DSE colonisation structures were observed in the roots of 25 medicinal plants. Total DSE colonisation was in the range of 2.22–100% and was significantly and positively correlated with soil organic matter, urease, and phosphatase. Host species purely explained 80.8%, 74.0%, and 79.0% of the observed variation in hyphal, microsclerotial, and total DSE colonisation, respectively. Of the 14 DSE taxa isolated from all 25 medicinal plant roots, six species were reported here for the first time in medicinal plants. Nonmetric multidimensional scaling analysis revealed that DSE colonisation and species composition significantly differed between different plant species. The DSE colonisation and species composition were predominately affected by plant identity than by soil factors. We conclude that the dynamics of DSE in the roots of medicinal plants exhibited a highly correlated plant species pattern, which further correlated with soil nutrient availability and enzymatic activity. This research provides a basis for further understanding of the ecological functions of DSE and their roles in the promotion of yield and quality of medicinal plants in the farmland ecosystems.

Fungal endophytes can improve plant tolerance to abiotic stress, however, the role of these plant–fungal interactions in desert species ecology and their management implications remain unclear. This study aimed to assess the effects of dark septate endophytes (DSE) on the performance of Artemisia ordosica and associated soil factors and microbial functional group abundance under salt stress. We investigated the effects of three DSE (Alternaria chlamydosporigena [AC], Paraphoma chrysanthemicola [PC] and Bipolaris sorokiniana [BS]) isolated from desert habitats on plant morphology, physiology and rhizosphere soil microhabitat of A. ordosica seedlings under different NaCl concentrations (0, 1, 2, 3 g NaCl/kg soil) in a growth chamber. The three DSE strains could colonize the roots of A. ordosica, and the symbiotic response with host plants depended on DSE species and NaCl concentration. The greatest benefits associated with DSE occurred under 1 g NaCl/kg soil. Specifically, AC promoted the accumulation of total biomass and enhanced superoxide dismutase (SOD) activity; PC promoted the accumulation of root biomass and increased indoleacetic acid (IAA) contents; and BS enhanced SOD activity and glutathione (GSH) and IAA contents. DSE reduced the root Na+ content. Interestingly, BS promoted gram-positive (G +) under 1 g NaCl/kg soil and the abundance of arbuscular mycorrhizal (AM) fungi under 3 g NaCl/kg soil. PC positively affected fungi, AM fungi, gram-negative (G −) bacteria and actinomycetes under 2 g NaCl/kg soil, and increased AM fungi and G – bacteria under 3 g NaCl/kg soil, while AC increased the abundance of all examined microbes under 3 g NaCl/kg soil. Structural equation modeling (SEM) demonstrated that DSE inoculation significantly influenced the relationship between the growth of A. ordosica, soil factors and rhizospheric microbial functional groups under NaCl stress treatments. DSE enhanced the root development of host plants and altered the soil nutrient content and microbiota under different NaCl concentrations, possibly contributing to plant growth and ecological adaptability under saline environment. These results contribute to the understanding of ecological function of DSE inoculation in improving the adaptability of plants to salt stress and may be used to promote vegetation restoration in salinized desert areas.

Hedysarum scoparium, a species characterized by rapid growth and high drought resistance, has been used widely for vegetative restoration of arid regions in Northwest China that are prone to desertification. Desert soil is typically deficient in available water and the alleviation of drought stress to host plants by endophytes could be an efficient strategy to increase the success of desert restoration. With the objective to seek more beneficial symbionts that can be used in the revegetation strategies, we addressed the question whether H. scoparium can benefit from inoculation by dark septate endophytes (DSEs) isolated from other desert plants. We investigated the influences of four non-host DSE strains (Phialophora sp., Knufia sp., Leptosphaeria sp., and Embellisia chlamydospora) isolated from other desert plants on the performance of H. scoparium under different soil water conditions. Differences in plant performance, such as plant growth, antioxidant enzyme activities, carbon, nitrogen, and phosphorous concentration under all the treatments, were examined. Four DSE strains could colonize the roots of H. scoparium successfully, and they established a positive symbiosis with the host plants depending on DSE species and water availability. The greatest benefits of DSE inoculation occurred in water stress treatment. Specifically, Phialophora sp. and Leptosphaeria sp. improved the root biomass, total biomass, nutrient concentration, and antioxidant enzyme activities of host plants under water deficit conditions. These data contribute to the understanding of the ecological function of DSE fungi in drylands.

The soil microbial community and edaphic factors in the rhizosphere and bulk soils of Hedysarum scoparium were investigated at seven arid desert locations in northwest China in July 2016. Plant and edaphic factors had significant effects on the community composition and functional diversity of soil microbes. Bacteria (ranging from 2.57 to 4.23 nmol g−1) contributed the most to the microbial community composition, followed by actinomycetes, followed by fungi. Carbohydrates, polymers, and carboxylic acids were the main carbon sources for soil microorganisms. Principal component analysis showed that the carbon source catabolism of soil microorganisms was higher in the rhizosphere than in bulk soils. Spearman correlation analyses revealed that the content of Gram-negative bacteria was significantly negatively correlated with the amino acids and that the content of AM fungi was significantly positively correlated with the carbohydrates and amines. Soil organic carbon, pH, and ammoniacal-N were significant predictors of microbial community composition, whereas soil organic carbon, phosphatase activity, and soil moisture were closely correlated with microbial carbon catabolism. This study indicated that soil microbial community composition and functional diversity are influenced by plants, nutrient availability, and enzymatic activity in the arid desert and serve as useful indicators for evaluating the soil quality and function of the desert ecosystem based on their relationships with the microbial community and soil nutrient distribution.

Although the spatial patterns of soil microbial community composition are well studied, little is known about the main factors driving microbial distributions in desert ecosystems. Therefore, the objective of this study was to examine the comprehensive effect of spatial scale, plant cover and environmental properties on soil microorganisms under Ammopiptanthus mongolicus canopies at 5 desert locations in Northwest China. Sampling site significantly influenced the soil microbial community structure and metabolic functions under A. mongolicus canopies. Variation of soil microbial communities was mostly attributed to the simultaneous effects of plant cover and soil factors, while purely plant cover explained more variation in catabolic function than did the principle coordinates of neighbour matrices (PCNM) and soil factors. Soil microbial structure and catabolic metabolism were both significantly affected by phosphatase, glomalin and soil organic carbon. Bacterial and actinomycete phospholipid fatty acids (PLFAs) were positively correlated with ammonium nitrogen (N), and the utilization of carbohydrates, carboxylic acids and amino acids was positively correlated with Olsen phosphorus (P). Bacteria (1.43–4.79 nmol∙g−1) were most common in the microbial community, followed by actinomycetes (0.54–1.89 nmol∙g−1) and fungi (0.29–0.48 nmol∙g−1). Carbohydrates (12%–85%) and amino acids (5%–59%) were the main carbon sources for soil microbes. Soil microbial community abundance and catabolic utilization were significantly higher in the rhizosphere of A. mongolicus than in the bulk soils, and principal component analyses (PCAs) significantly separated the rhizospheric soil microbes from those of infertile bulk soils. The results of this study support the conclusion that soil microbial composition and catabolic functional diversity in desert soils are spatially predictable and determined more by specific soil properties and plant cover than by large-scale distance. This research provides a basis for evaluating the management of soil resources and microbial function in desert environments.