The biogeography of fermentative yeast populations from the vineyards of the Azores Archipelago

This study aims at the characterization of the fermentative yeasts flora of the vineyards from Azores, for biodiversity preservation and the constitution of a Saccharomyces cerevisiae strain collection. During the harvest of 2009, 88 grape samples were collected from eight islands of the archipelago, that belonged to traditional (Arinto, Verdelho and Terrantez) and hybrid grape varieties. The sampling plan covered 36 locations, including vineyards in appellations of origin and abandoned vineyards. Forty nine spontaneous fermentations were achieved. About 83% of the musts obtained from traditional varieties finished fermentation, while this value was 47% and 33% for musts from hybrid varieties in non-abandoned and abandoned vineyards, respectively. From the final phase of the fermentations, a total of 1470 isolates was obtained. The identification was performed by restriction fragment length polymorphism analysis (RFLP) of ITS sequences. The S. cerevisiae strains were differentiated by the comparison of polymorphic patterns that were obtained from interdelta sequences amplification by PCR. We obtained 660 isolates of non-Saccharomyces species and 810 isolates of S. cerevisiae, classified in 168 strains. Surprisingly, the percentage of S. cerevisiae in fermentations performed with grapes from abandoned vineyards was significantly higher (75%) compared to the values determined for non-abandoned vineyards (56%, for both traditional and hybrid varieties). Contrarily, the number of S. cerevisiae strains per fermentation was lower (3-11) in samples from abandoned vineyards compared to non-abandoned vineyards (1-23). The relative proportion of S. cerevisiae and non-Saccharomyces species was not associated with the grape variety, but rather the type of vineyard. The highest number of S. cerevisiae strains per fermentation was observed in samples collected from the Graciosa Island. Our results show that Azorean vineyards have a high genetic diversity of S. cerevisiae, even in locations where no human intervention occurs