Functionally complementary bacterial inoculant coordinates arbuscular mycorrhizal fungi to improve Angelica sinensis...

Radix Angelica sinensis (RAS) is a high-value medicinal herb whose productivity and medicinal quality are often constrained by soil-borne diseases and suboptimal rhizosphere conditions. Plant growth-promoting rhizobacteria (PGPR) offer a sustainable alternative to chemical inputs, yet the efficacy of different microbial combinations and their functional mechanisms remains unclear. Here, we tested three PGPRs (one Pseudomonas isolate and two Bacillus strains) to A. sinensis rhizospheres. We showed that the three-member composite microbial agent (CMA) exhibited the most pronounced effects on promoting growth, increasing yield, suppressing disease, and boosting the accumulation of bioactive compounds. We further observed that treatments containing Bacillus-based inoculants enhanced the colonization of arbuscular mycorrhizal fungi (AMF) in RAS at harvest. These AMF likely utilize root-secreted and rhizosphere-enriched lipid compounds (palmitic acid, linoleic acid, and sphingolipids) both as carbon source and as symbiosis signals, thereby promoting root growth and helping protect against pathogens. Interestingly, a single Pseudomonas-based formulation performed on par with the three-strain consortium across multiple functional traits but showed limited effects on the accumulation of medicinal metabolites. This unique effect is likely linked to its capacity to enrich nitrogen in the rhizosphere soil, a change that is closely tied to fungal and nematode disease suppression. Furthermore, the CMA consortium improved the quality of RAS by enhancing its phenylpropanoid pathways. Taken together, our findings highlight functionally complementary microbial inoculants as an attractive and sustainable strategy to enhance the value of medicinal plants by simultaneously increasing yield and improving agronomic quality.