Production of Bacteriophage L522 for Management of Bacterial Leaf Blight on Rice in Field Trial

Rice cultivation, particularly in tropical Asian countries, has faced a serious challenge from bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae (Xoo). Bacteriophage biocontrol provides a potential solution for sustainable BLB management, offering enhanced safety and environmental sustainability compared to antibiotics. The first objective of this study was to investigate suitable culture media and incubation temperature for enhancing the growth rate of the host Xanthomonas oryzae pv. oryzae LA1+. The optimal time for adding phage into the bacterial culture and the sufficient infection time were also identified. Tryptone Soya Broth was selected as the nutrient medium for phage propagation. Six hours post-bacterial inoculation into fresh medium, bacteriophage L522 was added, and then the mixture was shaken at 150 rpm under the temperature of 28 – 30 °C for 6 h. These conditions resulted in the highest final phage titer of 9.5 log10 PFU/mL (p < 0.001). The second objective was to evaluate the efficacy of L522 to manage BLB in a field trial. Phage treatment showed the same effectiveness as the popular pesticide Starner 20WP in controlling BLB in the rice field (p = 0.391). This study presented a strategy for producing phage L522 and indicated the promising efficacy of phage biocontrol of BLB in the prevalence of antibiotic-resistant Xoo in rice.