Abstract
The ability of Saccharomyces cerevisiae yeasts to ferment in the presence of a low level of nitrogen is an important trait for the conduct of alcoholic fermentations. Yeast strains show differences in ability that are still poorly understood. We have developed a quantitative genetic approach to identify genes and alleles involved in contrasting abilities to ferment in a nitrogen-deficient environment. QTLs (Quantitative Trait Loci) and regions of the genome of the strains have been identified to modulate this trait. However, functional analyses of candidate genes have not demonstrated their role, suggesting that the trait is under complex genetic control. This project also aimed at developing conditions for measuring the nitrogen requirement of yeasts under simplified conditions in order to facilitate the evaluations and selection of strains. A simplified synthetic medium and measurement protocols have been developed to conduct evaluations under technological conditions.