Bacillus cereus AR156 Induces Defense Responses in Rice Against Sheath Blight Caused by Rhizoctonia solani

Rice sheath blight, caused by Rhizoctonia solani, is a major constraint on rice production, and its management still relies mainly on chemical fungicides. We evaluated the biocontrol agent Bacillus cereus AR156 against the disease and examined the transcriptional and biochemical changes in rice that accompany protection. AR156 achieved a biocontrol efficacy of 71.81% at 6 days after inoculation. RNA sequencing compared AR156-treated and control plants with and without pathogen challenge, and we identified 4554 and 2740 differentially expressed genes at 24 and 48 h after inoculation, respectively. AR156-responsive genes were enriched in secondary metabolism, plant-pathogen interaction, hormone signaling, phosphoinositide signaling, and membrane transport. Of the defense-associated DEGs, 97 TF/TRs and 86 predicted PRGs were shared between 24 and 48 h, most of which reversed their direction of change over time. Prominent TF/TR families included SNF2, bHLH, MYB, MYB-related, FAR1, PHD and WRKY, with KIN and RLK prominent among the predicted PRG classes. Quantitative RT-PCR and enzyme assays showed higher expression of several pathogenesis-related and hormone-associated markers, together with increased superoxide dismutase, peroxidase, and catalase activity after challenge. Together, these results indicate that AR156 suppresses rice sheath blight by temporally reshaping coordinated transcriptional and biochemical defenses rather than a single pathway.