Biological Control of a Novel Strain Bacillus Velezensis CMML21–47 Against Sweet Potato Wilt and Black Rot Diseases

A root bacterium identified as Bacillus velezensis CMML21–47 with strong biocontrol activity against two major sweet potato fungal diseases caused by Fusarium oxysporum and Ceratocystis fimbriata was isolated in this study. In vitro bioassays and field assays were conducted to test the biocontrol activity and confirmed its strong antagonistic activity. The complete genome of B. velezensis CMML21–47 was sequenced, and multiple gene clusters related to the synthesis of antibiotics by antiSMASH analysis were detected. The crude lipopeptide of CMML21-47 showed high inhibition rates (above 76.79% and 85.27%) against fungal pathogens of sweet potato and potato. Selective ultra–high performance liquid chromatography with quadrupole time–of–flight mass spectrometry (UPLC–Q–TOF–MS) was performed and detected lipopeptides, including fengycin, surfactin, and bacillomycin. Lipopeptide fractions were separated, tested against the pathogens, and showed strong growth inhibition. Accordingly, CMML21-47 is an attractive antifungal agent, with high potential to control the sweet potato pathogens causing wilt and black rot diseases.