Control of postharvest decay of apple fruit with Candida saitoana and induction of defense responses

The ability of Candida saitoana to induce systemic resistance in apple fruit against Botrytis cinerea was investigated. To separate the antagonistic activity of C saitoana from its ability to induce resistance, the antagonist and the pathogen were applied in spatially separated wounds. In fresh apples, C. saitoana applied 0 or 24 h before inoculation with B. cinerea showed no effect on lesion development caused by B. cinerea. When applied 48 to 72 h preinoculation with B. cinerea, however, C saitoana reduced lesion diameter by more than 50 and 70%, respectively, compared with wounding. C saitoana had no effect on lesion development on stored apples, regardless of the lag period between yeast treatment and inoculation with B. cinerea. In addition to inducing systemic resistance, C. saitoana increased chitinase and beta-1,3-glucanase activities with a higher accumulation in fresh than in stored apples. In fresh apples, the onset of systemic resistance to B. cinerea coincided with the increase in chitinase and beta-1,3-glucanase activity in systemically protected tissue. These studies show that C saitoana is capable of inducing systemic resistance in apple fruit and indirectly suggest that antifungal hydrolases are involved in the observed systemic protection.