The isolation, identification and efficacy of Bacillus velezensis XF-8 in tomato bacterial wilt control

Tomato bacterial wilt is an important disease caused by Ralstonia solanacearum, which is harmful to the development of tomato industry and seriously affects the yield and quality of tomato. In this study, the strain XF-8 with antagonism against R. solanacearum was isolated from soil and identified as Bacillus velezensis, and its control effect on tomato bacterial wilt was better than that of kasugamycin. The disease index of tomato plants treated with XF-8 was significantly reduced (P < 0.05) in the pot experiment, and the control effect was 74.25 %, which was higher than 45.11 % of kasugamycin treatment group. The antibacterial activity of lipopeptide extract from the fermentation supernatant of strain XF-8 was further verified, and then the inhibitory rate of the substance at the concentration of 1 mg/mL was as high as 96.20 %. The microscopic investigations indicated that the surface of R. solanacearum was wrinkled and deformed after treating with lipopeptide extract, and most of the bacteria were dead and rupture of the cell membrane, which leading to the cell death. Meanwhile, the active oxygen was produced and the lipopeptide extract could also significantly induced DNA injuries of R. solanacearum. All these results confirmed that the isolated strain B. velezensis exhibited excellent effect of preventing and controlling the tomato bacterial wilt. Moreover, XF-8 strain has high inhibitory effect on 10 types of pathogenic fungi, which shows broad-spectrum bacteriostasis. This study provides a theoretical basis and strain resources for the development and application of biopesticides, and broadened the potential biocontrol value of B. velezensis.