A multifunctional Streptomyces murinus bioinoculant integrates immune priming and microbiome restructuring for sustainable control of Sclerotinia minor in Brassica rapa

BACKGROUND: Harnessing beneficial soil microbes provides an eco-friendly alternative to pesticides for sustainable crop protection. Members of the genus Streptomyces combine broad antagonistic activity with plant immune priming and growth promotion, yet their ecological roles and field reliability remain insufficiently understood. We investigated the soil actinobacterium Streptomyces murinus JS029 in the Brassica rapa-Sclerotinia minor pathosystem to elucidate its mechanisms of pathogen suppression, plant immune activation and rhizosphere microbiome modulation, and to develop a field-deployable formulation. RESULTS: Streptomyces murinus JS029 secreted chitinase, cellulase and protease and produced the polyene macrolides pentamycin and filipin I, which are known to disrupt fungal cell walls and plasma membranes. Plants exposed to Streptomyces murinus JS029 exhibited strong activation of salicylic acid, jasmonic acid and ethylene signalling pathways and were associated with enhanced biomass and strong protection against Sclerotinia minor. A barley-based solid formulation ensured reproducible field efficacy, reducing disease by approximately 70-80%. Rhizosphere sequencing revealed increased fungal richness and distinct bacterial-fungal compositional shifts, indicating functional reassembly of the soil microbiome. Genome analysis and ultraviolet (UV) mutagenesis linked antifungal activity to a polyene biosynthetic gene cluster. CONCLUSION: Streptomyces murinus JS029 integrates direct antagonism, immune priming and microbiome restructuring to support disease-suppressive soils. These findings provide mechanistic insights and a practical framework for deploying multifunctional Streptomyces bioinoculants as sustainable alternatives to chemical fungicides in integrated pest management systems. © 2026 Society of Chemical Industry.