Low-nitrogen input enriches Massilia bacteria in the phyllosphere to improve blast resistance in rice

Excessive nitrogen (N) fertilization exacerbates rice blast disease caused by Magnaporthe oryzae, yet the underlying microbiological mechanisms remain unclear. Through integrated field surveys and controlled experiments, we demonstrate that high-N application worsens disease severity by disrupting microbiome communities in the phyllosphere of rice (Oryza sativa) plants. We identified microorganisms in the phyllosphere through 16S rDNA sequencing. Low-N conditions were associated with a greater Massilia bacterial population, which was negatively correlated with pathogen abundance and disease index. In vitro and in vivo experiments indicated that Massilia enhances rice resistance to rice blast disease. We explored how Massilia confers resistance. Massilia strain z571 directly inhibited M. oryzae spore germination and hyphal invasion while also activating host immunity, including elevated levels of salicylic acid and jasmonic acid, enhanced expression of defense-related genes, and increased activity of antioxidant defense enzymes. Moreover, Massilia exhibited broad-spectrum antagonism against multiple pathogens. Our findings unveil a microbiome-mediated mechanism linking N fertilization to disease susceptibility and highlight Massilia as a potential biocontrol agent, offering a sustainable strategy for managing rice blast through optimized fertilization practices and microbial interventions.