Grapevine endophytic yeasts: biocontrol agents or white rot supporters?

Esca is one of the most damaging grapevine trunk diseases worldwide, and it is closely associated with wood decay processes. While fungi involved in esca have been extensively studied, the role of wood-inhabiting yeasts remains largely unknown. In this study, we investigated the diversity and potential functional role of endophytic yeasts isolated from asymptomatic, necrotic, and white rot tissues of Vitis vinifera cv. Cabernet-Sauvignon and Sauvignon blanc. A total of 31 yeast strains belonging to four species (Aureobasidium pullulans, Papiliotrema terrestris, Rhodotorula glutinis, and Hanseniaspora uvarum) were identified, with white rot representing the main source of isolation. In vitro assays were used to evaluate their antagonistic activity against Fomitiporia mediterranea by dual culture, volatile and non-volatile metabolite tests and enzymatic activity modulation. Results showed a strong strain-dependent inhibition of pathogen growth. Rhodotorula glutinis and P. terrestris were the most effective yeasts, with volatile compounds causing up to 83 % mycelial pathogen growth reduction. Non-volatile metabolites also significantly inhibited fungal growth, while co-cultivation altered ligninolytic enzyme activity in F. mediterranea. Overall, our findings highlight white rot as a selective niche for antagonistic yeasts and suggest that yeast-derived volatile compounds and metabolites may limit pathogen development, with potential applications in sustainable management of grapevine trunk diseases.