Flor yeast strains from culture collection: Genetic diversity and physiological and biochemical properties

Sixteen flor yeast strains from the Magarach Collection of the Microorganisms for Winemaking (Yalta, Crimea), which are used for production of sherry, were analyzed for morphophysiological, cultural, and biochemical properties. Long-term storage did not affect their viability or the preservation of major properties, such as their flor- and aldehyde-forming abilities, and the ability to produce wines with typical sherry properties. Significant variation in the strains was observed mainly in the aldehyde-forming and flor-forming abilities and flor properties. Interdelta typing was shown to be the most informative technique to study the genetic diversity of flor yeast strains. Certain correlations between genetic polymorphisms and the enological properties of the strains were observed. The presence of a 24-bp long deletion in the ITS1 spacer of the ribosomal gene cluster, a typical feature of Spanish flor yeast strains, is correlated with a high level of production of aldehydes and acetales, efficient flor formation, and the ability to produce high quality sherry. The presence of a specific deletion in the promoter of the FLO11 gene appeared to be less informative, since the aldehyde and acetal production and flor formation abilities of such strains were variable. The studies of intraspecies genetic polymorphism by various molecular markers have revealed a high degree of phylogenetic closeness of some yeast flor strains from different geographic regions.