Structure of culturable indigenous yeast population and genetic diversity of Saccharomyces cerevisiae and non-Saccharomyces yeasts during spontaneous fermentation of Etna vineyards grapes

The microbial diversity of indigenous yeasts plays a fundamental role in the spontaneous fermentation of wines, contributing to the concept of microbial terroir and potentially influencing the sensory profile of the final product. This study explores the yeast ecology and genetic diversity of Saccharomyces cerevisiae and non-Saccharomyces yeasts in four wineries located on two different sides of Mount Etna, a region of unique viticultural significance due to its volcanic soils and diverse microclimatic conditions. A total of 454 yeast isolates were obtained from spontaneous fermentations of different grape varieties, and identified as belonging to 18 distinct species. The spontaneous fermentation was characterized by an initial dominance of non-Saccharomyces yeasts, especially Hanseniaspora uvarum and Metschnikowia pulcherrima, followed by a gradual dominance of S. cerevisiae at later stages. Microsatellite genotyping revealed significant genetic diversity among S. cerevisiae strains, with some distinct genetic patterns associated with Italian winery environments. Additionally, H. uvarum exhibited significant genetic variation but lacked clear geographic clustering, suggesting complex ecological and enological interactions. Statistical analyses of microbial diversity indices indicated that vineyard-specific factors, including altitude, soil composition, and agronomic practices, may influence yeast community structure among the four wineries. These findings provide new insights into the microbial ecology of Etna wines and highlight the potential of indigenous yeast populations for maintaining and enhancing regional wine identity.