Dynamics of Rhizosphere Microbial Communities and Bioactive Compound Accumulation in Wild-Simulated Astragalus mongholicus Across Different Cultivation Years

Knowledge regarding the structure and distribution patterns of rhizosphere microbial communities of Astragalus mongholicus (A. mongholicus) under wild-simulated cultivation remains limited. This study investigated how cultivation duration affects soil properties, microbial communities, and bioactive compound accumulation, as well as the relationships among these factors. High-throughput sequencing of the 16S rRNA and ITS regions was performed to profile bacterial and fungal communities in rhizocompartments of 1–4-year-old A. mongholicus. Meanwhile, soil physicochemical properties and bioactive compounds were quantified. Fungal community diversity in the rhizosphere of A. mongholicus varied across cultivation years, whereas bacterial community diversity showed a comparatively weaker response. The relative abundances of the potentially beneficial taxa Mortierellomycota and Mortierella in rhizosphere soil gradually declined with increasing cultivation age. Soil nutrient-related variables (OM, OC, P, and NH4+-N) were the main drivers shaping microbial community composition. Bioactive compound contents also fluctuated across cultivation years. Microbial genera including Mortierella, Pseudomonas, Bacillus, and the Allorhizobium–Neorhizobium–Pararhizobium–Rhizobium clade may be closely associated with the accumulation of bioactive compounds in A. mongholicus. These findings suggest that cultivation duration reshaped rhizosphere communities and bioactive compound accumulation in A. mongholicus. Soil nutrient availability and beneficial microbes were closely associated with these changes, providing insights for microbiome-informed quality improvement.