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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.

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.