Biocontrol Potential of Bacillus subtilis SV108 Against Aspergillus carbonarius and Botrytis cinerea of Grapevine

The increasing restriction of chemical fungicides has intensified the search for environmentally sustainable alternatives for grapevine disease management. In this study, we evaluated the biocontrol potential of Bacillus subtilis SV108, an endophytic strain isolated from grape berries, against major grapevine fungal pathogens. The antifungal activity of SV108 cell-free supernatant (CFS) was assessed in vitro against a panel of phytopathogenic fungi, revealing strong and concentration-dependent inhibition, particularly against Botrytis cinerea and Aspergillus carbonarius . These pathogens were further evaluated using a detached grape berry assay, where SV108 treatment significantly reduced lesion development compared with untreated controls, confirming efficacy under fruit-based conditions. To elucidate the mechanisms underlying antifungal activity, volatile organic compounds (VOCs) produced by SV108 during pathogen interaction were analyzed using SPME-GC-MS. SV108 emitted a complex blend of bioactive VOCs, including alcohols, aldehydes, ketones, organic acids, phenols, and pyrazines, many of which are known for their antimicrobial properties. Principal component analysis demonstrated distinct VOC profiles between bacterial strains and fungal pathogens, with SV108 showing similarities to the established biocontrol strain Bacillus amyloliquefaciens AG1. Qualitative proteomic analysis of the active antifungal fraction identified peptides homologous to non-ribosomal peptide synthetases associated with iturin and mycosubtilin biosynthetic pathways, as well as proteins linked to siderophore production and secondary metabolite biosynthesis. The results indicate that B. subtilis SV108 suppresses fungal growth through a multi-modal mechanism involving both soluble antifungal metabolites and volatile emissions. These findings support the potential application of SV108 as a sustainable biocontrol agent for grapevine disease management, particularly in postharvest and integrated disease control strategies.