Control of postharvest decay of apple fruit by Aureobasidium pullulans and induction of defense responses

The biocontrol activity of Aureobasidium pullulans on decay of apple fruit caused by Botrytis cinerea and Penicillium expansum, and its ability to induce biochemical defense responses in apple tissue, were investigated. In apple wounds, A. pullulans multiplied rapidly and controlled decay caused by either B. cinerea or P. expansum. At the end of the storage period, A. pullulans reduced the incidence of gray and blue mold of apple by 89 and 67%, respectively, compared to the water-treated control. In addition to controlling decay, A. pullulans caused a transient increase in β-1,3-glucanase, chitinase, and peroxidase activities starting 24 h after treatment and reaching maximum levels 48 and 96 h after treatment. An increase in β-1,3-glucanase, chitinase, and peroxidase activity was also triggered by wounding, although, the level of increase was markedly lower than that detected in treated fruit. The ability of A. pullulans to increase activities of β-1,3-glucanase, chitinase, and peroxidase in addition to its known capacity to out-compete pathogen for nutrients and space, may be the basis of its biocontrol activity.