Genetic and phenotypic diversity of Saccharomyces sensu stricto strains isolated from Amarone wine - Diversity of Saccharomyces strains from Amarone wine

Individual yeast strains belonging to the Saccharomyces sensu stricto compl ex were isolated from Amarone wine produced in four cellars of the Valpolic ella area (Italy) and characterized by conventional physiological tests and by RAPD-PCR and mtDNA restriction assays. Thirteen out of 20 strains were classified as Saccharomyces cerevisiae (ex S. cerevisiae p.r. cerevisiae an d p.r. bayanus) and the remaining as Saccharomyces bayanus (ex S. cerevisia e p.r. uvarum). RAPD-PCR method proved to be a fast and reliable tool for i dentification of Saccharomyces sensu stricto strains and also gave intraspe cific differentiation. Restriction analysis of mtDNA permitted to distingui sh S. cerevisiae and S. bayanus species and to discern polymorphism among S . cerevisiae isolates. The assessment of the phenotypic diversity within th e isolates by gas-chromatographic analysis of secondary fermentation produc ts was explored. Small quantities of isobutanol were produced by most of th e strains and higher amounts by some S. cerevisiae strains with phenotypes Gal(-) and Mel(-) all S. bayanus strains produced low amounts of amilyc alc ohols. From this study it appears that each winery owns particular strains, with different genetic and biochemical characteristics, selected by specif ic environmental pressures during the Amarone winemaking process carried ou t at low temperature in presence of high sugar content.