Control of postharvest blue and gray mold in kiwifruit by Wickerhamomyces anomalus and its mechanism of antifungal activity

The primary postharvest diseases of kiwifruit are blue and gray mold which are caused by Penicillium expansum and Botrytis cinerea, respectively, and result in serious economic losses. Biological control has been shown to be an effective approach for the management of postharvest diseases. Previous studies reported that the antagonistic yeast, Wickerhamomyces anomalus, exhibited strong biocontrol activity against postharvest diseases of kiwifruit. Investigating the mechanisms responsible for its biocontrol activity will provide a theoretical basis for improving the biocontrol efficiency and application of this yeast antagonist. Results of this study indicated that the antifungal properties of W. anomalus are due to the combined effect of several mechanisms. These include the inhibition of growth of fungal pathogens on PDA or PDB, rapid colonization of the surface and wounds of kiwifruit, attachment to the surface of fungal mycelia, strong ability to form a biofilm, and produce volatile organic compounds (VOCs) with antifungal activity. The VOCs produced in YPD medium exhibited more inhibitory effects than VOCs produced in NYDA medium. A total of 12 VOCs were identified. The main VOCs produced were 2-phenethyl acetate and 1-butanol, 3-methyl-. Individually, these VOCs each exhibited a excellent level of antifungal activity.