Biocontrol of Bacterial Seedling Rot in Rice Plants Using Bacillus velezensis JBCS608 and Its Formulated Products

Burkholderia glumae, the causal agent of bacterial panicle blight and seedling rot (BSR), is a growing threat to rice production, yet effective and sustainable control measures remain limited. In this study, we evaluated Bacillus velezensis JBCS608 (JBCS608) as a promising biocontrol agent for the management of BSR in rice plants. Treatment with JBCS608 at an optimal concentration of 1 × 10⁸ CFU/mL significantly reduced disease severity, achieving a control efficacy of up to 68.9%. The strain exhibited broad-spectrum antagonistic activity, inhibiting the growth of multiple seed-borne bacterial pathogens, including B. glumae, Burkholderia gladioli, and Burkholderia plantarii, as well as fungal pathogens such as Fusarium moniliforme. In addition to disease suppression, JBCS608 promoted rice seedling growth, likely through the production of indole-3-acetic acid and siderophores, and phosphate-solubilizing activity. For practical applications, we developed both talc-based wettable powder and molasses humic acid liquid formulations using JBCS608 endospores. Both formulations exhibited biocontrol efficacy comparable to that of fresh bacterial cells and maintained high cell viability for over 6 months under cold storage conditions. Collectively, our results indicate that JBCS608 is a potent and eco-friendly biocontrol and plant growth-promoting agent with strong potential for commercial use in the integrated management of BSR in rice.