Isolation and evaluation of candidate plant-protecting bacteria from rice seedlings asymptomatic to Burkholderia glumae infection

Burkholderia glumae is a major causal agent of bacterial panicle blight (BPB) in rice, which is characterized by seedling and grain rot. Therefore, the aim of this study was to isolate potential biocontrol bacteria from rice and investigate their efficacies against B. glumae. Potential biocontrol bacteria were isolated from rice seedlings asymptomatic to B. glumae infection using the in planta evaluation screening (IPES) method. In vitro experiments were performed to examine the biocontrol activities of the bacterial isolates. Cultivation of rice seeds in soil (Bonsol No. 2) inoculated with these bacteria and B. glumae suppressed the pathogenicity of B. glumae. Isolates L5 and L6 showed 99.78% and 99.60% identity with Paenibacillus hunanensis, respectively, and isolate R2 was identified as Sphingomonas aquatilis. In vitro evaluation showed that R2 did not exhibit any biocontrol activity. Although the isolates showed inhibitory effects against B. glumae in rice seedlings grown in Bonsol No. 2, they did not show biocontrol activities in Naemidori soil. Notably, inoculation with L5, L6, and R2 bacterial mixture inhibited B. glumae pathogenicity in Naemidori. Conclusively, this study provides a strategy for the effective screening of biocontrol organisms for the sustainable prevention of B. glumae infection in rice.