Efficacy of bacteria isolated from asymptomatic rice leaves as biological control agent for bacterial leaf blight of rice / Ku Asmah Ku Sulong

Biological controls have been considered among the promising disease management strategies for sustainable agriculture as it could reduce the reliance on synthetic pesticides, overcome the problem of pesticide resistance, minimize the negative impact on the environment and non-target organisms and improve workers safety, whereas at the same time maintaining the economic viability of crop production. This study was conducted to isolate beneficial bacteria from asymptomatic rice plants and to screen it potential via in vitro and in vivo conditions for controlling bacterial leaf blight (BLB) disease. The current study found that Bacillus subtilis isolated from asymptomatic rice plants has exhibited high potential as a biological control agent (BCA) to manage bacterial leaf blight disease in rice caused by Xanthomonas oryzae pv. oryzae (Xoo). The finding revealed that the isolated bacterium was identified as Bacillus subtilis. Rice plants treated with this bacterium prior to BLB pathogen inoculation exhibited less severe symptoms of BLB disease as shown by disease severity index (DSI) 3.4 compared to 8.4 for rice plants treated only with the pathogen. Further evaluation under in vivo conditions showed the B. subtilis isolate capable to reduce severity of BLB disease symptoms on the treated rice plants either by preventive or curative approaches. The beneficial bacterium also has the capability to promote plant growth. Utilization of B. subtilis as a biological control agent to overcome BLB disease in rice plants could provide a greented approaches for rice farmers in Malaysia. The effective and economic development of a reliable formulation and delivery techniques of B. subtilis for applications in the rice fields are targets of future research to gear up the use of B. subtilis as a biological control product for BLB disease management.