Molecular identification of wine yeasts at species or strain level: a casestudy with strains from two vine-growing areas of Greece

The composition of wine yeast populations, present during spontaneous ferme ntation of musts from two wine-producing areas of Greece (Amyndeon and Sant orini) and followed for two consecutive years, were studied using a range o f molecular techniques. Internal Transcribed Spacer (ITS) ribotyping was co nvincingly applied for yeast species identification, proving its usefulness as a reliable tool for the rapid characterization of species composition i n yeast population studies. Restriction Fragment Length Polymorphism (RFLP) of mitochondrial DNA (mtDNA) was shown to be a convenient criterion for th e detection of intraspecies genetic diversity of both Saccharomyces and non -Saccharomyces isolate populations. Similarly, polymorphism of amplified de lta interspersed element sequences provided an additional criterion for S. cerevisiae strain differentiation. Comparative analysis of S. cerevisiae ge netic diversity, using mtDNA restriction patterns and delta-amplification p rofiles, showed a similar discriminative power of the two techniques. Howev er, by combining these approaches it was possible to distinguish/characteri ze strains of the same species and draw useful conclusions about yeast dive rsity during alcoholic fermentation. The most significant findings in popul ation dynamics of yeasts in the spontaneous fermentations were (i) almost c omplete absence of non-S.cerevisiae species from fermentations of must orig inating from the island Santorini, (ii) a well recorded strain polymorphism in populations of non-Saccharomyces species originating from Amyndeon and (iii) an unexpected polymorphism concerning S. cerevisiae populations, much greater than ever reported before in similar studies with wine yeasts of o ther geographical regions.