Volatile organic compounds produced by Aureobasidium pullulans inhibit the growth of Botrytis cinerea and Alternaria alternata

Botrytis cinerea and Alternaria alternata are two necrotrophic fungal pathogens causing grey and black mould, respectively on horticultural crops, leading to preharvest and postharvest losses worldwide. Aureobasidium pullulans is a yeast-like saprophytic fungus which naturally inhabits plant and fruit surfaces and is a potential biocontrol agent against a wide range of pathogenic fungi. Production of antifungal volatile organic compounds (VOC) has been postulated as one of the biocontrol mechanisms of A. pullulans. In this study the efficacy of antifungal VOCs from four A. pullulans isolates were tested in vitro against the mycelium growth and spore germination of B. cinerea and A. alternata. Exposure to the headspace of four A. pullulans isolates caused a 43-74% reduction of colony diameter of B. cinerea and 35-47% for A. alternata compared to non-fumigated controls after three days of incubation at 25°C. A. pullulans VOCs also reduced spore germination of both pathogens, resulting in 15-70% germination for B. cinerea and 22-60% of germination for A. alternata. Non-fumigated controls resulted in 90 and 85% of spore germination for B. cinerea and A. alternate, respectively. Morphological deformations were also observed in fumigated spores and growing germ tubes of the two pathogens when exposed to the headspace of the A. pullulans culture. Further investigations are in progress to identify A. pullulans VOCs responsible for these inhibitory activities.