Abstract: In order to explore the effect and possible modes of action of Candida oleophila on controlling Penicillium expansum in apples, plate confrontation tests of the yeast against the pathogen were carried out and the bacteriostatic effect of volatile compounds produced by the yeast on the pathogen was investigated; furthermore, the strains were inoculated separately or together into wounds of apple fruits to observe yeast growth and the activities of enzymes related to postharvest disease resistance. The results showed that C. oleophila treated fruits had lower disease incidence and lesion diameters than the control (P < 0.05). C. oleophila could not produce antifungal secondary metabolites, and its volatile substance had no significant inhibitory effect on the growth of P. expansum (P > 0.05). C. oleophila could colonize and amplify quickly in apple peel, and inhibit the increase of disease incidence and lesion diameter in fruits. C. oleophila also could effectively enhance the activities of peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonialyase (PAL) (P < 0.05). Based on the above analysis, the inhibitory mechanisms of C. oleophila against P. expansum in apples are through inducing disease resistance and competing for space and nutrition.

Key words: apple, Penicillium expansum, Candida oleophila, blue mold