Effect of dark septate endophytes on plant performance of Artemisia ordosica and associated soil microbial functional group abundance under salt stress

Abstract 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.