Reshaping root-associated microbiota to enhance medicinal quality: Application of optimized functional microbial inoculants in Salvia miltiorrhiza cultivation.

The application of functional microbial preparations is an effective means to improve medicinal plants quality. In this study, the preparation processes of various functional microbial inoculants had been optimized, and the effects of these inoculants on the quality and root-associated microecology of Salvia miltiorrhiza had been evaluated. By regulating the moisture content and particle size of fungal freeze-dried powder, the optimal process parameters for Trichoderma longibrachiatum (Tl), Alternaria tellustris (At), and Paraphoma radicina (Pr) were determined, and fungal inoculants with high storage activity at both normal and low temperature were produced. Microcapsules of Bacillus licheniformis (Bl) and Bacillus subtilis (Bs) were prepared by sodium alginate-CaCl2 dripping method. Two microcapsules showed encapsulation efficiencies above 90 % and maintained high viability after 6 months of storage. Pot experiments showed that five microbial inoculants boosted the quality of S. miltiorrhiza with the dose-dependent effects. Among them, T1 and At improved biomass and contents of tanshinone I, tanshinone IIA, and cryptotanshinone at low to medium application rates (0.15-0.3 g/1.5 Kg soil). Bs microcapsule also had a better effect. Variation partitioning, mantel tests, and structural equation modeling showed that the inoculants boosted the quality of S. miltiorrhiza by adjusting soil pH, enhancing soil nutrients and enzyme activities, and reshaping root-associated microbial community. These inoculants enriched taxa, including Trichoderma, Funneliformis, Sphingomonas, and Actinoplanes, and suppressed pathogenic fungi. These findings demonstrated that rationally designed microbial inoculants sustainably improve yield and bioactive components through targeted modulation of root-associated microbial networks, offering an eco-friendly strategy for high-quality medicinal plant cultivation.