Sexually-Driven Combinatorial Diversity in Native <i>Saccharomyces</i> Wine Yeasts

Abstract

Natural diversity represents an inexhaustible source of yeasts for the diversification of wines and the improvement of their properties. In this study, we analysed the genetic diversity of autochthonous Saccharomyces cerevisiae wine yeasts in the Aljarafe of Seville, one of the warmest winemaking regions of Spain. Through multiplex-PCR analysis of five microsatellite markers and RT-PCR determination of the killer genotype, we found 94 different patterns among 150 S. cerevisiae yeast strains isolated from spontaneous fermentation of grape must, thereby representing a highly diverse population. Remarkably, 92% of the isolated strains exhibited high sporulation capacity. Tetrad analysis of sporulating strains rendered a microsatellite marker’s combinatory that mimics patterns observed in the native population, suggesting that the high polymorphism of microsatellite markers found in these wild yeasts might result from sexual reproduction in their natural environment. The identification of unconventional M2/L-A-lus totivirus combinations conferring the killer phenotype also supports this suggestion. One idea behind this study is to determine to what extent the vineyards microbiota in areas with warm climates can provide useful natural yeasts to adapt fermentation processes to the needs imposed by global warming. Analysis of traits of oenological interest in regions potentially affected by global climate changes, such as growth tolerance to ethanol and to sugar stress in the analysed strains, indicated that this broad combinatorial diversity of natural S. cerevisiae yeasts provides a wide range of autochthonous strains with desirable profiles for quality winemaking in warm regions. This combinatorial diversity renders strains with diverse oenological performing abilities. Upon microvinification assays and organoleptic attests, a S. cerevisiae strain with interesting oenological properties has been identified. This result can be considered a successful outcome in industry–academia collaboration.

Keywords

• native yeast
• spontaneous fermentation
• combinatorial polymorphism
• Aljarafe winemaking region
• global climate change