BACILLUS AMYLOLIQUEFACIENS L x -11, A POTENTIAL BIOCONTROL AGENT AGAINST RICE BACTERIAL LEAF STREAK

A strain of Bacillus amyloliquefaciens denoted Lx-11 was found to possess biocontrol activity against rice bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola. Lx-11 secreted three kinds of lipopeptides including surfactin, bacillomycin D and fengycin, which exhibted antibacterial activity against X. oryzae pv. oryzicola. The antibacterial activity could be associated with surfactin-lipopeptides, and was practically abolished in surfacin-deficient mutants. In addition, the defense-related genes PR-1a, PR-1b, NPR1 and PAL were concurrently expressed in the leaves of rice after treatment with Lx-11. Results suggest that Lx-11 triggers a systemic immunization activity. Lx-11 significantly reduced the incidence of BLS, control efficacy ranging from 60.2% to 70.6%, i.e. better than that afforded by bismerthlazol in field experiments. We conclude that B. amyloliquefaciens Lx-11 might be a promising biocontrol agent and should be further studied.