Inhibitory and growth-promoting effects of antimicrobial lipopeptides-producing strain B5 on of potato black scurf pathogen

Bacillus velezensis（strain B5）was used to explore strains effective in inhibiting potato black scurf, elucidate antibacterial characteristics and growth-promoting effects of antagonistic bacterium bacteria, and lay a foundation for development and utilization of biocontrol bacteria against potato black scurf．Growth-promoting effect was determined through pot experiments．Two treatments were designed: infected soil（CK treatment）and infected soil+strain B5 fermentation broth（T₁ treatment）．Dynamic monitoring was conducted throughout potato entire growth period, measuring potato plants' agronomic traits and contents of available potassium, alkali-hydrolyzable nitrogen, and available phosphorus in rhizosphere soil at different stages．Secondary metabolites prediction and gene functional annotation were performed for strain B5．Qualitative analysis of lipopeptide antibiotics produced by strain B5 was conducted using LC-MS technology．Research showed that metabolites produced by strain B5 directly inhibit black scurf pathogen growth, causing wrinkles and depressions in Rhizoctonia solani hyphae．Genome of strain B5 contained 12 secondary metabolite biosynthesis gene clusters．Strain B5 secreted two lipopeptide antibiotics, Surfactin and Iturin．Throughout entire potato growth period, T₁ treatment consistently exhibited significantly higher available potassium content than that CK treatment, reaching 205.33, 124.22, and 292.33 mg/kg during seedling stage, tuber formation stage, and starch formation stage, respectively．Alkali-hydrolyzable nitrogen content in T₁ treatment was only 101.77 mg/kg during starch formation stage, representing a 49.38% reduction compared to CK treatment．Available phosphorus content in T₁ treatment showed the most significant difference during starch accumulation stage, with 159.61 mg/kg．Results indicated that strain B5 could secrete antimicrobial lipopeptides to destroy hyphal structure of pathogen and inhibit its growth．Simultaneously, it enhanced nutrient content in rhizosphere soil and promotes plant growth．