Effective growth restriction of Botrytis cinerea and Colletotrichum fioriniae by wine grape-associated native non- Saccharomyces yeasts

AIMS: Fungal biological control agents (BCAs) have been widely researched as alternatives to conventional fungicides. As the wine grape industry relies on intensive sprays, bio-based solutions, especially those that may also enhance wine fermentations, may hold potential for reducing chemical inputs while improving wine quality. This study aimed to isolate and identify yeast strains from vineyards to evaluate their biocontrol efficacy against major fruit rot pathogens and additional value as fermentation starters. METHODS AND RESULTS: Wild yeasts were isolated from vineyards in Maryland. Recovered isolates (n=234) were characterized with ITS and 26S sequencing analysis and processed in a series of experiments to determine potential antagonistic activity against Botrytis cinerea and Colletotrichum fioriniae. Capabilities for micro-fermentation of grape juice was also evaluated for selected biocontrol candidates. Five yeasts belonging to Aureobasidium (JB951), Pichia (JB524, JB543, and JB767), and Zygoascus (JB624) showed significant antagonism, each restricting the mycelial growth of both pathogens in vitro. Among these yeasts, Pichia JB767 and Aureobasidium JB951 significantly inhibited pathogen spore germination in vivo as well. While some of the yeasts only performed well either as BCAs or fermenters, Pichia JB524 and JB767, and Zygoascus JB624 tested demonstrated dual functions. CONCLUSIONS: This study suggests that these yeasts may not only be valuable in disease control but could also serve as effective fermentation starters, warranting further validation in a more practical setting.