Résumé
During alcoholic fermentation, Saccharomyces cerevisiae requires S-containing amino acids, that it produces through the sulfur assimilation pathway (SAP). In this pathway, S. cerevisiae reduces sulfate into sulfur dioxide (SO2) and sulphide (H2S) whose overproduction is a major issue in winemaking due to its negative impact on wine aroma. The amount of H2S produced is very strain-specific and depends as well on the SO2 concentration, which is often added in winemaking. First we set up a quantitative method to measure the H2S produced during alcoholic fermentation, and evaluated this production for 34 strains isolated from wine, flor or oak in a must devoid of SO2. Large differences between strains were detected, and strains carrying a specific allele of SKP2 (SKP2JN10) (Noble, et al. 2015) were identified as low producers. However, when exposed to SO2, several strains carrying the SKP2 allele produce H2S again. In order to decipher the genetic bases of the H2S production in the presence of SO2, we used a QTL mapping strategy. We produced a population of segregants, crossing IR08 carrying SKP2JN10 allele with a 59A, that did not produce H2S in the presence of SO2. The production of H2S in the presence of SO2 will be evaluated for the progeny, and a QTL analysis will be performed from the comparison of bulks containing low and high H2S producers. This approach will enable us to identify the genetic basis of the differences of H2S production among wine strains and could provide novel targets for improving wine yeast strains.