Volatile Organic Compounds Produced by Bacillus velezensis CT32 Attenuate Botrytis cinerea Pathogenicity by Impairing Autophagy

Gray mold, caused by Botrytis cinerea, is the predominant fungal disease responsible for postharvest losses in strawberries. Here, we show that volatile organic compounds (VOCs) released by Bacillus velezensis CT32 significantly inhibited B. cinerea mycelial growth and attenuated its pathogenicity on strawberry fruit, reducing gray mold incidence by 51.35%. An optimized headspace solid−phase microextraction−gas chromatography−mass spectrometry method was developed to profile CT32 VOCs, identifying 30 compounds, predominantly aldehydes, alcohols, and ketones. Scanning electron microscopy revealed that CT32 VOCs severely disrupted hyphal surface structure, as evidenced by deformation, collapse, peeling, and breakage. Comparative transcriptomic analysis further revealed that exposure to CT32 VOCs significantly downregulated pathogenicity−associated genes and pathways involved in fructose and mannose metabolism, arginine and proline metabolism, proteasome, and autophagy in B. cinerea. This transcriptional signature was corroborated by fluorescent labeling and ultrastructural observations, which indicated that CT32 VOCs impaired autophagy in B. cinerea. Collectively, strain CT32 VOCs exert antifungal activity through a multi−component, multi−target mode of action that compromises hyphal integrity, perturbs carbohydrate and amino acid metabolism, and disrupts intracellular homeostasis in B. cinerea, with autophagy impairment further restricting nutrient recycling and cellular damage clearance and hindering homeostatic recovery, thereby suppressing fungal growth and pathogenicity.