Electrophoretic karyotyping, mitochondrial DNA restriction fragment length polymorphism analysis, and PCR amplification of interspersed repeats were used to study the variability, phylogenetic affinities, and biogeographic distribution of wild Saccharomyces cerevisiae enological yeasts. The survey concentrated on 42 individual wine cellars in the Charentes area (Cognac region, France). A limited number (35) of predominant S. cerevisiae strains responsible for the fermentation process have been identified by the above molecular methods of differentiation. One strain (ACI) was found to be distributed over the entire area surveyed. There seemed to be little correlation between geographic location and genetic affinity.

Fifteen indigenous strains of Saccharomyces cerevisiae, differentiated by their genetic polymorphism, were compared in standard conditions for their respective ability to produce volatile compounds during the alcoholic fermentation of grape must. The results were processed using analysis of variance and of principal components. They exhibited significant differences between strains, in particular for the higher alcohols, fatty acid esters, acetates or acetaldehyde. On the basis of their analytical profile, five strains were selected and compared on the pilot scale. Overall, the pilot results confirmed laboratory findings. As the strain effect appears to be determinant on the aromatic composition of wine spirits, a programme of selection based on both intraspecific molecular characterisation and chromatographic analysis is carried out to obtain specific yeast strains for high-quality spirits.

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