Grape pigment adsorption is an inheritable QTL of yeasts.

The purpose of this work was the validation of the assumption, formulated in a previous study (Caridi et al., Journal of Applied Microbiology, 2007, 103, 735-742), that Grape Pigment Adsorption (GPA) phenotype is a Quantitative Trait Loci (QTL) in yeasts. The oenological trait GPA was studied in 153 wine yeasts - 17 wild type strains of Saccharomyces cerevisiae and 136 single-spore descendants - 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 pH, total acidity, absorbance at 420, 520, and 620 nm, colour intensity, and Folin-Ciocalteu index. Data have confirmed that the oenological trait GPA is inheritable and polygenic; effectively, for each related parameter - both concerning biomass colour and wine analysis - there are a congruous number of single-spore descendants significantly different from parents. Genetic analysis was performed on the 10 wild types having single-spore descendants showing superior fermentation properties. 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 initial assumption. This validation would be very useful because allows the possibility to improve wine yeast as regards the GPA trait.