Bacillus thuringiensis G-5 efficiently suppresses Codonopsis pilosula postharvest diseases by generating antifungal volatile organic compounds

Inappropriate storage conditions make Codonopsis pilosula more susceptible to infection by harmful fungi because of moisture, which reduces the plant's therapeutic effectiveness. The volatile organic compounds (VOCs) of plant endophytes have shown great promise in recent years for managing postharvest plant diseases. This study investigates the inhibitory effects of VOCs released by Bacillus thuringiensis G-5 on two postharvest pathogenic fungi of C. pilosula: Fusarium oxysporum F-3 and Penicillium oxalicum F-5. The results revealed that the mycelial growth inhibition rates of these fungi induced by the VOCs from G-5 were 94.01% and 95.37%, respectively. Scanning electron microscopy observations and Propidium Iodide staining experiments further confirmed that these VOCs could markedly alter the morphology and structure of mycelia and spores and compromise the integrity of the cell membrane. Headspace gas chromatography-ion mobility spectrometry analysis identified 21 high-concentration volatile substances released by G-5, with 3-hepten-2-one identified as the primary antifungal component. The minimum inhibitory concentrations of 3-hepten-2-one against F-3 and F-5 were determined to be 40 μL/L and 20 μL/L, respectively. Further research indicated that 3-hepten-2-one disrupts the structural and functional integrity of the cell membrane. In vivo experiments demonstrated that 3-hepten-2-one exhibited superior efficacy in preventing and controlling C. pilosula infections compared to the VOCs produced by G-5. This study not only provides a promising new antifungal agent for managing postharvest diseases of C. pilosula but also enhances our understanding of the role of VOCs produced by G-5 in biological control.