Biocontrol potential and mechanism of volatile organic compounds released by Bacillus velezensis GX0003742 against post-harvest banana anthracnose

Banana anthracnose, caused by Colletotrichum musae, is one of the most severe fungal diseases affecting banana production and has led to significant economic losses in the banana industry. In this study, Bacillus velezensis strain GX0003742 was found to release volatile organic compounds (VOCs) with strong antifungal activity, achieving up to 80 % control efficacy against post-harvest banana anthracnose. A total of multiple VOCs was identified via GC–MS analysis, among which ten exhibited inhibitory effects on C. musae. Notably, 2-nonanol and citronellol showed inhibition rates exceeding 50 %, with IC₅₀ values of 11.45 μL/L and 14.89 μL/L, and minimum inhibitory concentration (MIC) of 2.70 μL/L and 3.95 μL/L, respectively. Fluorescence staining revealed that both compounds significantly disrupted fungal cell wall integrity, altered membrane permeability, and induced abnormal accumulation of mitochondrial reactive oxygen species (ROS), ultimately leading to programmed cell death of the hyphae. Molecular docking analysis showed that both VOCs could bind to chitin synthase and potentially interfere with its function. In addition, 2-nonanol and citronellol effectively maintained banana fruit quality and triggered the accumulation of defense- and antioxidant-related enzymes, thereby activating defense responses and enhancing host resistance against pathogens. Overall, this study is the first to identify 2-nonanol and citronellol from B. velezensis GX0003742 and to elucidate their dual roles in direct antifungal activity and the induction of host resistance. These findings provide new theoretical insights and biological strategies for the eco-friendly management of banana anthracnose.