Check of the grape pigment adsorption in three generations of yeasts

In order to check the Grape Pigment Adsorption (GPA) phenotype in wine yeasts, 23 strains of Saccharomyces cerevisiae - 3 wild types, 16 single-spore descendants and 4 hybrids obtained by crossing the descendants - have been utilized. The GPA trait was studied both on yeast biomass, using the chromogenic medium Grape-Skin Agar, and by microvinification trials. A computer-assisted assessment of the biomass colour of the yeasts grown on Grape-Skin Agar was performed. The wines produced by the microvinification trials have been analysed for absorbance at 420, 520, and 620 nm, colour intensity, and Folin-Ciocalteu index. Data have confirmed the possibility to improve wine yeast as regards the GPA trait. For example, considering the two wild types RC029 and RC039, the 12 single-spore descendants and the two hybrid RC029A-1D x RC039C-1C (4) and RC029B-1C x RC039C-1C (7) it is evident that there is a significant improvement of the GPA phenotype due to the evolution driven by the selection and the breeding programmes. Genetic analysis was performed on the 3 wild types. Genome sizes were estimated by flow cytometry. An aploid strain of the laboratory yeast BY 474i was used as the standard and assigned a relative fluorescence value of 1.0. A diploid strain Zymaflor F15 and an aneuploid strain Anchor NT50 (Bradbury et al., Antonie van Leeuwenhoek, 2006, 89, 27-37) were also used as control strains. All the strains had genome sizes consistent with their being diploid, so validating the observed results. This study would be very useful because demonstrates the possibility to improve wine yeast as regards the GPA trait.