Characterization of Bacillus velezensis YTQ3 as a potential biocontrol agent against Botrytis cinerea

Gray mold is a fungal disease with high incidence and great economic loss caused by Botrytis cinerea. Here, it was found that the cell-free supernatant (CFS) derived from Bacillus velezensis YTQ3 reduced the mycelial growth and spore germination of the B. cinerea in a dose-dependent manner. Further examination using scanning electron microscopy disclosed the deformation and collapse of the B. cinerea mycelial structure. CFS could also effectively control gray mold of three kinds of fruit. It is worth pointing out that the application of CFS did not adversely affect fruit quality. Moreover, the CFS was resistant to extreme temperatures, acidic and alkaline conditions, ultraviolet light, and proteases. To gain further insights into the potential secondary metabolites produced by B. velezensis YTQ3, the complete genome of the YTQ3 strain was sequenced. Genome analysis revealed 14 biosynthetic secondary metabolite gene clusters responsible for polypeptides, polyketides, bacteriocin, and terpenes. Notably, the lipopeptide compound extracted from CFS significantly restrained the B. cinerea growth, and the main inhibitory substance was identified as surfactin and fengycin by liquid chromatography-mass spectrometry (LC-MS). These findings suggest that strain YTQ3 holds promise as a prospective agricultural biocontrol agent and a resource for further developing antifungal compounds.