Genetic investigation of yeast biodiversity from Georgia, the first grapevine domestication center

Archaeological and palaeobotanical findings point Georgia, in the Caucasus region, as the area where the grapevine domestication (Vitis vinifera L.) took place and where the earlies examples of winemaking have been found (McGovern, 2003). These considerations, coupled with the local custom to avoid the usage of starter cultures for must fermentation, make Georgian yeast biodiversity particularly interesting to be investigated under the genetic point of view. In this study we performed genetic characterization of yeast strains isolated from grapes, musts and wines in six different Georgian regions. One hundred and seventy-six isolates were identified as belonging to 14 different species. Saccharomyces cerevisiae was the most prevalent (37%). Genetic profiles of S. cerevisiae isolates were compared with commercial starters by capillary electrophoresis and amplification of interdelta regions. Interdelta analysis highlighted a high level of biodiversity resulting in a clear discrimination between Georgian and commercial starter strains. Strains showing the highest level of variability (59) were submitted to whole-genome sequencing for more thorough comparative genomic analysis with publicly available genomes of wine and non-wine yeasts. Phylo-geneomics and population structure analyses based on complete genomic sequences consistently grouped the Georgian strains in a cluster along with wine yeasts. Gene duplication events attested in the Georgian strains, included genes related to ion/molecules transport, detoxification and response to metal ions. These results provide a resource for further selection of new starter strains to meet the demand of new wine styles and innovative ways of managing fermentations.