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

Abstract

This study aims at the characterization of the fermentative yeasts flora of the vineyards from the Azores archipelago, for biodiversity preservation and the constitution of a Saccharomyces cerevisiae strain collection. During the harvests of 2009 and 2010, 163 (88 and 75) 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. Ninety five spontaneous fermentations (49 and 46 in 2009 and 2010, respectively) were achieved. In 2009, 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. In 2010 those values were 62%, 67% and 47% respectively. From the initial phase of the fermentation, 4890 isolates were obtained (2640 and 2250 in 2009 and 2010, respectively), belonging to more than 20 species, being Hanseniaspora uvarum, Issatchenkia terricola, Candida zemplinina, Metschnikowia pulcherrima, Zygoascus meyerae, Hanseniaspora opuntiae the most representative ones. Some differences were apparent between grape varieties, regions and islands regarding the most representative species. From the final phase of the fermentations, a total of 2850 isolates was obtained (1470 and 1380 in 2009 and 2010, respectively). The identification was performed by restriction fragment length polymorphism analysis (RFLP) and sequencing of ITS regions. The S. cerevisiae strains were differentiated by the comparison of polymorphic patterns that were obtained from interdelta sequences amplification by PCR. From the samples collected in 2009, 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.