Endophytic Bacillus toyonensis D-6 via producing antifungal volatile organic compounds effectively controls green grape postharvest diseases

Grapes are susceptible to fungal infections before, during transport, or after harvest, causing significant economic losses. Traditional methods have high equipment costs and are prone to the development of drug resistance. The antifungal potential of volatile organic compounds (VOCs) produced by endophytic bacteria is beginning to be understood. VOCs are ideal for post-harvest disease control in fruits and vegetables, as they can work without direct contact with the fruit. In this study, we isolated pathogenic fungi ( Penicillium crustosum G-4, Alternaria alternata G-5, Arthrinium phaeospermum G-8) from post-harvest rotting green grape and used G-8 as a test organism, screened the endophytic bacterium Bacillus toyonensis D-6 from Typhonium giganteum Engl. that could produce strong antagonistic active VOCs, analyzed the components of its VOCs and screened for the highly effective inhibitory compound 3-methylvaleric acid (3-MA). The inhibitory activities and mechanisms of action of the VOCs and antifungal compounds were investigated. The results showed that the VOCs and 3-MA produced by D-6 inhibited the growth and reproduction of the pathogenic fungi, which mainly exerted antagonistic effects by destroying the normal morphological structure of mycelium and spores and damaging the integrity of cell membranes. In addition, appropriate concentrations of VOCs and 3-MA inhibited the spread of pathogenic fungi on green grapes and effectively delayed the decline in fruit quality. This opens up new possibilities for post-harvest preservation of green grapes and provides a theoretical basis for related applications.