Abstract
Wine biological aging is a wine making process used to produce specific beverages in several countries in Europe, including Spain, Italy, France, and Hungary. This process involves the formation of a velum at the surface of the wine. Here, we present the first large scale comparison of all European flor strains involved in this process. We inferred the population structure of these European flor strains from their microsatellite genotype diversity and analyzed their ploidy. We show that almost all of these flor strains belong to the same cluster and are diploid, except for a few Spanish strains. Comparison of the array hybridization profile of six flor strains originating from these four countries, with that of three wine strains did not reveal any large segmental amplification. Nonetheless, some genes, including YKL221W/MCH2 and YKL222C, were amplified in the genome of four out of six flor strains. Finally, we correlated ICR1 ncRNA and FLO11 polymorphisms with flor yeast population structure, and associate the presence of wild type ICR1 and a long Flo11p with thin velum formation in a cluster of Jura strains. These results provide new insight into the diversity of flor yeast and show that combinations of different adaptive changes can lead to an increase of hydrophobicity and affect velum formation.
Highlights
IntroductionIn addition to alcoholic fermentation, some beverages are obtained through a specific aging process called flor wine aging
Numerous fermented beverages have been developed all over the world during history
Subclusters formed inside the main group of flor strains according to geographical origin: three clusters of Jura strains, two clusters of sherry wine strains (Jerez 1 and 2), and one main cluster of Sardinian strains
Summary
In addition to alcoholic fermentation, some beverages are obtained through a specific aging process called flor wine aging During this process, which takes place only after the completion of alcoholic fermentation, a biofilm called velum is formed by yeast at the surface of the wine leading to the progressive oxidation of alcohol and remaining carbohydrates. Flor yeast belong to the species Saccharomyces cerevisiae [5], and the population of flor yeast isolated from the velum of Sherry wines differs from the population of strains that perform alcoholic fermentation [5,6] These two populations are genetically isolated [7], as shown by the ITS1 region in Spanish and Jura flor strains, which have specific alleles of ITS1 caused by a 24 bp deletion [5] and a G insertion [8], respectively. Various molecular techniques used to explore the diversity of flor yeast populations in several countries suggest a large genetic diversity [8,9,10,11]
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