Rice varietal intercropping mediates resistance to rice blast (Magnaporthe Oryzae) through core root exudates.

BACKGROUND: Rice blast (caused by Magnaporthe oryzae) severely limits rice production worldwide and poses an ongoing threat to food security. Intercropping of rice varieties shows effective rice blast control but the role of root interactions in mediating resistance remains unclear. RESULTS: Here we show that intercropping a susceptible and a resistant variety enhances disease resistance in both varieties under field and greenhouse conditions through root-secreted metabolites that activate defense pathways. Transcriptome analysis further showed that intercropping triggered a broad immune response. Metabolome profiling identified systemic changes in root exudate composition, including enrichment of flavonoid/phenylpropanoid biosynthesis pathways and antifungal metabolites. Correlation analysis linked these metabolites to resistance-regulating genes, leading to the identification of four core compounds: azelaic acid (AzA), sebacic acid (SA), betaine (Bet), and phenyl acetate (PhAc). Functional validation confirms AzA and SA significantly inhibited the mycelial growth of M. oryzae, and exogenous application of all four compounds before inoculated with M. oryzae significantly reduced the rice blast disease incidence under greenhouse conditions. CONCLUSION: These findings indicate that intercropping can induce resistance in susceptible varieties through the key root exudates, providing insights into the mechanisms by which rice root metabolites mediate resistance to rice blast in intercropping systems.