The Introduction of Flocculation into a Homothallic Wine Yeast. A Practical Example of the Modification of Winemaking Properties by the Use of Genetic Techniques

Abstract

The property of flocculation was introduced into a powdery wine yeast strain MD26 by mating spores of MD26 with haploid vegetative cells of laboratory yeast strain TE90 which carried a dominant gene for flocculation. Spore-vegetative cell mating was performed by micromanipulation and flocculent diploid hybrid strains were isolated. The fermentation performance of three hybrid strains was evaluated in small scale winemaking trials. Flocculent haploid strains were isolated from two of the hybrid strains and mated with MD26 spores. Five flocculent diploid hybrid strains were isolated from these matings and their winemaking properties evaluated. Three hybrid strains had similar fermentation patterns and produced similar wines to those of the original strain MD26. A scheme which demonstrates how undesirable genetic information is eliminated from the hybrid strains by back breeding is given. This investigation demonstrates how winemaking properties of a yeast may be modified by selective hybridization and back breeding.