Jessica Noble,* Valentin Tilloy, Frédéric Bigey, Jean-Luc Legras, Anne Julien, and Sylvie Dequin  
*INRA UMR Sciences Pour l’Oenologie, 2 place Viala, 34060 Montpellier, France (noble@supagro.inra.fr)

Over the past decades, global warming and its effect on grape ripening, combined with evolution of consumer preferences toward low-alcohol, but full bodied and well-structured, wines has raised a major concern for the wine industry. Producing wines with lower alcohol content became one of the highest challenges. However the conversion rate of sugars into ethanol is very stable among Saccharomyces cerevisiae strains. To overcome those physiological limitations, we implemented a combination of evolutionary engineering approaches and classical breeding. Our approach resulted in a strain with decreased ethanol production linked to enhanced production of glycerol but also an increase of acidity, conferring more balance and freshness to wines. Metabolomic, transcriptomic, and genetic studies showed that these modifications are not due to deregulation or mutation of genes directly involved in the glycerol synthesis pathway, but to major changes in carbon, energy, and redox metabolism that are probably under multigenic control. To identify the molecular basis of these new phenotypes, QTL mapping was implemented using bulk segregant analysis (BSA) and combined with whole-genome sequencing of the evolved strains. Regions of the genome linked to the phenotypes have been highlighted and candidate genes are under functional validation.

Funding Support: Institut National de la Recherche Agronomique