Bacillus velezensis G-1 lipopeptides and genomics reveal biocontrol and probiotic traits against postharvest rot caused by Alternaria solani and Alternaria alternata

Postharvest fungal infections significantly reduce the quality and shelf life of fruits and vegetables, with Alternaria species causing major losses in crops such as tomatoes, pears, and jujubes. This study investigated the antifungal potential of Bacillus velezensis G-1 and its secondary metabolites against Alternaria solani and Alternaria alternata. In vitro assays showed that B. velezensis G-1 inhibited fungal mycelial growth by over 80 %, with lipopeptides forming inhibition zones greater than 25 mm. In vivo tests at 0 and 4 °C confirmed strong antifungal activity. In addition, B. velezensis G-1 and its metabolites suppressed the production of four fungal toxins: alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN), and tenuazonic acid (TeA), with inhibition rates exceeding 60.61 %, particularly against AME and TEN. LC-ESI-MS analysis identified fengycin as the primary antifungal compound. Genomic analysis confirmed B. velezensis G-1 as a distinct strain, revealing 73 key genes and two gene clusters involved in lipopeptide biosynthesis. A comparative analysis with B. velezensis FZB42 identified 15 genetic differences among 73 key genes involved in lipopeptide biosynthesis. Quorum sensing and polyketide biosynthesis were identified as the key regulatory pathways. These findings highlight B. velezensis G-1 as a promising biocontrol agent for managing postharvest fungal diseases in economically important crops.