Identification of grape berry indigenous epiphytic yeasts with in vitro and in vivo antagonistic activity towards pathogenic fungi

During their lifespan, grapes are exposed to conditions that can endanger plant health, including fluctuating climate and infection by pests and insects. In particular, attacks by filamentous fungi represent huge annual losses for grape farmers. Present concerns about rising antimicrobial resistance, fungicide prohibitions and shifting consumer tastes are driving the search for less harmful ways of preventing damage to grapevine by pathogenic fungi. In this study, the antagonist activity of yeasts isolated from grape berry surface microbiota was assessed by in vitro and in vivo assays on an assortment of grapevine fungal pathogens, including Botrytis cinerea and Aspergillus niger. The results show that W. anomalus, A. pullulans, C. intermedia, R. glutinis, Z. meyerae and H. takashimae were able to inhibit by 75 to 100 % mycelia growth and sporulation of the filamentous fungi in vitro. Strains of M. pulcherrima and S. bacillaris also showed 50 to 75 % efficacy in reducing mould growth. The strains were further assessed on incised leaves of 2-month-old grapevines for their ability to reduce disease incidence by the filamentous fungi. W. anomalus, A. pullulans, M. pulcherrima, C. intermedia and R. glutinis significantly reduced infection symptoms in the leaves, indicating their potential as effective biocontrol yeasts in the vineyard.