Improved wine yeasts by direct mating and selection under stressful fermentative conditions

Hybridization of yeasts allows whole-genome modifications that can be exploited to obtain global improvements in industrial traits, such as those involved in the winemaking industry. In our work we applied direct mating to achieve the construction of hybrids and we subsequently applied these hybrids in fermentation trials under stressful conditions, in order to select hybrid strains with improved technological traits. Five hybrids, obtained from six parental strains by direct spore conjugation, were validated through PCR amplification of highly variable minisatellite-containing genes; the validation phase also revealed three meiotic derivative strains, characterized by contracted number of repeats. Analysis of the mating-type locus in the homozygous spore progeny of parental strains provided useful insights into the understanding of hybridization yields and unveiled some irregularities in yeast autodiploidization mechanism. The fermentative trials were followed by chemical analysis; afterwards principal component analysis allowed the metabolic footprinting of wine yeasts and the selection of the two best industrial candidates, which display superior phenotypes in fermentative fitness and secondary metabolite production, respectively.