Grape-associated yeasts as promising antagonists against fungal pathogens

Biocontrol, a practice for using living organisms to target plant pathogens, offers a promising, sustainable agricultural strategy. This study involves epiphytic yeasts isolated from Vitis vinifera ssp. sylvestris and ssp. vinifera as natural antagonists against Aspergillus carbonarius, Botrytis cinerea, and Penicillium expansum. Twenty-one of 37 yeasts were chosen based on the Pathology Intensity (PA) score during preliminary in vivo screening. Following identification, dual-culture assays, VOC production, copper tolerance, and commercial fungicide resistance were assessed. On YPD and GJ medium, Saccharomyces isolates were the strongest antagonists, whereas P. terricola UMY197 inhibited Penicillium and Aspergillus. H. uvarum UMY1473 was notably effective against B. cinerea. VOC analysis confirmed that S. cerevisiae UMY1430 was the most effective against Aspergillus, likely owing to its production of oxalic acid, while S. cerevisiae UMY1438 was a producer of various esters and phenylethyl alcohol. C. intermedia UMY189, M. pulcherrima UMY1472, H. uvarum UMY1473, and S. cerevisiae UMY1436 were the most copper-resistant. Yeast activity on chemical fungicide SWITCH (up to 1 g/L) depended on culture media usage; in fact, a higher viability on YPD than on GJ was observed, where only 4 yeasts were able to grow. Thus, since several yeasts exhibit promising inhibitory activity through various mechanisms and against different molds, the use of synthetic consortia could represent a powerful and essential tool in field trials to limit fungicide use while preventing the emergence of resistance.