Phosphorus availability enriches Massilia in the root microbiome to enhance resistance against Sclerotinia sclerotiorum in rapeseed

Phosphorus is an essential macronutrient for plant growth and development, especially in P-sensitive crops such as rapeseed ( Brassica napus ). However, the mechanism by which P availability modulates plant disease resistance by shaping the root‑associated microbiome remains poorly understood. Here, we investigated how P homeostasis regulates rapeseed resistance to Sclerotinia sclerotiorum through modulation of the root-associated microbiome. P deficiency significantly inhibited plant growth and increased susceptibility to S. sclerotiorum in multiple rapeseed ecotypes, including spring, semi‑winter, and winter types. Microbiome profiling revealed that Massilia was a key P-responsive biomarker genus significantly enriched under P-sufficient conditions. Both foliar application and root inoculation with Massilia effectively suppressed S. sclerotiorum infection in rapeseed. Mechanistically, Massilia colonization strongly activated the expression of pathogenesis‑related (PR) genes, antioxidant genes, and jasmonic acid (JA) signaling genes. Overall, this study establishes a P-mediated tripartite interaction linking root microbiota assembly and plant immunity. These results highlight that optimizing P supply to enrich beneficial microbes such as Massilia can enhance rapeseed resistance to S. sclerotiorum , providing a sustainable strategy for disease management.