Biocontrol Potential of Beneficial Fungus <i>Aureobasidium pullulans</i> Against <i>Botrytis cinerea</i> and <i>Colletotrichum acutatum</i>

Abstract

Biological control is a promising approach to reduce plant diseases caused by fungal pathogens and ensure high productivity in horticultural production. In the present study, we evaluated the biocontrol potential and underlying mechanisms of the beneficial fungus <i>Aureobasidium pullulans</i> against <i>Botrytis cinerea</i> and <i>Colletotrichum acutatum</i>, casual agents of gray mold and anthracnose diseases in strawberry. Notably, this is the first time that <i>A. pullulans</i> has been tested against <i>C. acutatum</i> in strawberry. <i>A. pullulans</i> strains (AP-30044, AP-30273, AP-53383, and AP-SLU6) showed significant variation in terms of growth and conidia production. An inverse relationship was found between the growth and conidiation rate, suggesting a trade-off between resource allocation for growth and conidial production. Dual plate co-culturing assays showed that mycelial growth of <i>B. cinerea</i> and <i>C. acutatum</i> was reduced by up to 35 and 18%, respectively, when challenged with <i>A. pullulans</i> compared with control treatments. Likewise, culture filtrates of <i>A. pullulans</i> showed varying levels of antifungal activity against <i>B. cinerea</i> and <i>C. acutatum</i>, reducing the mycelial biomass by up to 90 and 72%, respectively. Furthermore, milk powder plate assays showed that <i>A. pullulans</i> produced substantial amounts of extracellular proteases, which are known to degrade fungal cuticle. Ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) analyses revealed that <i>A. pullulans</i> produced exophilins, liamocins, and free fatty acids known to have antifungal properties. <i>A. pullulans</i> shows high potential for successful biological control of strawberry diseases and discuss opportunities for further optimization of this beneficial fungus.