P-070 - Seed Endophytic Bacteria Protects Rice Against Seedling Blight Pathogens

Seedling blight is an important disease in rice, particularly in the southern U.S., where dry-seeded rice is the predominant production method. Although several fungal pathogens can cause seedling blight, Rhizoctonia solani is the primary pathogen. While fungicide seed treatments are available for conventional rice farming, effective options for organic production remain lacking. Microbial communities within seeds play an essential role in promoting germination and increasing resilience to both biotic and abiotic stresses. This study aimed at identifying potential biocontrol agents against seedling blight pathogens, with a focus on naturally occurring endophytic bacteria within rice seeds. Endophytic bacteria were isolated from rice seeds, and in vitro assays were conducted to determine the antagonistic effects of selected bacterial isolates against seedling blight pathogens. A total of 85 endophytic bacteria were isolated, which were classified into 10 genera and 31 unique “species” based on 16S rRNA analysis. Among them, three bacterial isolates exhibited strong in-vitro antagonistic activities against seedling blight pathogen. In subsequent greenhouse and field trials, seed treatments with two bacterial isolates, Bacillus sp. ST24 and Pantoea sp. ST25, effectively reduced stand loss caused by seedling blight pathogens. These results highlight the potential of utilizing naturally occurring seed endophytic bacteria as biocontrol agents for managing seedling blight pathogens in rice.