Application of endophytic bacterium Bacillus velezensis BTR11 to control bacterial leaf blight disease and promote rice growth

Abstract Background Bacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive pathogens responsible for severe yield losses in rice. Application of bacterial biocontrol agent (BCA) with plant growth promotion (PGP) abilities is a promising method that alternates current conventional practices to manage BLB disease and increase crop yield. Hence, this study aimed to isolate and identify BCA with PGP abilities from internal plant tissues and rhizosphere soil of healthy and Xoo-infected rice and evaluate their antagonistic and PGP properties under greenhouse and field conditions. Results A total of 14 bacterial isolates were isolated and presented in vitro antagonistic ability against the Xoo. The rice endophytic bacterium strain Bacillius velezensis (BTR11) had the highest antagonistic activity against the Xoo, produced indole acetic acid (IAA), and mineralized nutrients (K and P). The greenhouse experiment revealed that culture broth of strain BTR11 had a high protective effect (72.1%) against the BLB when applied at the protective-fighting mode, i.e., before and after the Xoo infection. Preliminary results of the field experiment showed that a protective effect against the bacterial blight disease was obtained as high as 75–85%, if the strain was used as an additive to the soil for the seedlings in combination with spraying when the disease began in the field. In addition, using the strain BTR11 also increased the rice yield to about 12% more than the un-treatment control. Conclusions The study showed a significant potential for the application of endophytic bacteria in controlling BLB disease, while stimulating plant growth, thus reducing the use of agrochemicals in rice cultivation