Selection of Endophytic Antagonistic Bacteria for Control of Tobacco Bacterial Wilt

Tobacco bacterial wilt is a soil-borne bacterial disease caused by Ralstonia solanacearum, which is mainly harmful to the roots and stems of tobacco and seriously affects tobacco yield. Fifty-five endophytic bacterial strains were isolated from healthy tobacco planted in diseased soils. Among them, strains R-3, R-7 and R-9 had obvious antagonistic effects on R. solanacearum in plate antagonistic experiments. Based on gyrB gene sequence, R-3, R-7 and R-9 all belong to Bacillus velezensis. After heated at 115℃, the liquid fermentation of the 3 strains still had antibacterial activities, indicating that these strains produced heat resistant substances. Field experiments showed that R-3, R-7 and R-9 were all able to chronically colonize in the root and stem of tobacco, and their control efficiency against bacterial wilt were 55.72%, 48.34% and 50.71%, respectively.