High nitrogen-induced changes in rhizosphere microbial community structure can modulate disease susceptibility to the rice blast

BACKGROUND: Nitrogen-induced susceptibility (NIS) in rice, where excess nitrogen (N) enhances vulnerability to Magnaporthe oryzae, has been observed but remains mechanistically unclear. Here, we demonstrate that the rhizosphere microbiome plays a central role in mediating NIS. RESULTS: Using an experimental system that separates nitrogen effects from plant growth changes, we found that high N levels significantly reshape bacterial and fungal community composition, and suppressed defense-associated genes, including OsPAL06 and OsPR10b. Predicted functional profiling indicated enrichment of salicylate-degradation and secretion-related signatures under highN. Our findings revealed that both nitrogen treatment and pathogen infection significantly influence rhizosphere community composition, with a strong interaction between the two factors. Network analysis further revealed reduced microbial connectivity and loss of keystone taxa under high-N and infection conditions. Rhizosphere microbiome transplantation from high-N, infected donors to standard-N recipients reproduced the NIS phenotype and suppressed defense gene expression, supporting a microbiome legacy effect. CONCLUSIONS: These findings suggest that excess N promotes rhizosphere microbiome configurations with immune-modulatory potential that can persist beyond the immediate nutrient regime. Our results position the rhizosphere microbiome as a determinant of NIS and support microbiome-informed, nutrient-aware disease management strategies.