Efficacy of Bacillus atrophaeus strain RS36 and Priestia megaterium strain RS91 with Partially Reduced Fertilization for Bacterial Leaf Blight Suppression in Rice Seedlings

Four plant growth-promoting rhizobacteria (PGPR) strains; Bacillus atrophaeus strain RS36, Priestia koreensis strain RS86, Priestia megaterium strain RS91 and B. macauensis strain RS100, were previously reported for their growth enhancement and anthracnose disease reduction in peppers. RS36 and RS86 do not produce siderophore, while RS91 and RS100 do. There is little evidence of using PGPR-mediated induced systemic resistance with reduced fertilization to control bacterial leaf blight (BLB) in rice seedlings. This study aimed to investigate the efficacy of those four individual PGPR strains and their co-inoculation with 75% recommended chemical fertilizer rate (RFR) against BLB disease in rice seedlings. Non-siderophore-producing PGPR strains experiment and siderophore-producing PGPR strains experiment were tested separately. Each experiment was conducted twice and contained a single strain and their mixtures with 75%RFR. Nonbacterized treatment with 100%RFR served as a control in each experiment. A completely randomized design was set up with 4 replications per treatment. Results demonstrated that rice seedlings treated with a single PGPR strain and their mixtures with 75% RFR generally had a lower percentage of disease severity than rice seedlings in the control treatment. Nevertheless, only rice seedlings treated with a single strain of RS36 in the non-siderophore PGPR experiment and a single strain of RS91 in the siderophore-producing PGPR experiment provided a significantly lower percentage of disease severity (P£0.05) than the control of each experiment. No synergistic effect of disease suppression occurred when using PGPR mixtures. In conclusion, certain individual PGPR strains together with reduced fertilizer amount significantly suppressed BLB disease in rice seedlings.