Aureobasidium pullulans as a biocontrol agent of postharvest pathogens of apples in Uruguay

Aureobasidium pullulans was the microorganism most frequently recovered from the surface of apple fruit (cv. Red Delicious) stored in commercial cold chambers for 6 months. In the present work, 10 isolates of Aureobasidium pullulans were assayed to determine if they could control blue and grey mold disease of apple during cold storage. Although nine of 10 isolates, significantly reduced the percentage of decayed wounds when compared to the control, one of them, designated isolate ApB, showed the highest levels of protection. ApB was able to grow in a wide range of temperatures lower than 35 degrees C, which is an important human health safety factor. ApB was resistant to thiabendazole, iprodione and imazalil, the most commonly commercially applied fungicides in postharvest treatment of apples in Uruguay. Regarding the mechanisms of action of the selected biocontrol agent, lytic enzymes did not seem to play a central role. ApB depleted iron from nutrient media, which may be an important aspect of its ability to inhibit Botrytis cinerea. Further experiments are needed, however, to determine if the depletion of iron is caused by the production of siderophores, by the immobilization of iron in an insoluble pigment, or a combination of both.