Diversity and geographical distribution of indigenous Saccharomyces cerevisiae strains from the Comahue winegrowing region (Argentinean North Patagonia).

LOPES C.A.; ZAJONSKOVSKY I.; BARBAGELATA R.; RODRÍGUEZ M.E; LAVALLE L.; SANGORRÍN M.; CABALLERO A.

Rosario

Congreso; V Congreso Argentino de Microbiología General-SAMIGE; 2008

One of the most significant technological advances in winemaking has been the control of the microbiological process by grape must inoculation with selected Saccharomyces cerevisiae strains. Today, the use of indigenous wine yeasts selected from each winegrowing area is a widespread enological practice. These local yeasts are presumed to be more competitive than commercial yeasts because they are better adapted to the ecological and technological features of their own area. Comahue region is one of the most Southern winegrowing regions in the world. In this region, located in Argentinean Patagonia, spontaneous and conducted grape juice fermentations are carried out to produce mostly dry red wines. The aim of this work was to characterize the indigenous wine Saccharomyces cerevisiae diversity within Comahue region in order to develop regional starters. Six cellars located in four different winegrowing areas, Colorado (RC) and Negro (HC) River Upper Valleys, in Rio Negro Province, and El Chañar (Ch) and Añelo (Ñ) in Neuquen province, were selected and 19 spontaneous and conduced red wine fermentations carried out in them during 2002 to 2006 vintages were sampled at different stages. Yeasts were isolated onto YEPD agar plates and 523 isolates assigned to S. cerevisiae species using ITS1-5.8S-ITS2 PCR-RFLP method were characterized at the strain level using combined mtDNA-RFLP and killer behaviour against K2 type toxin patterns. Twenty three commercial starters often used in the cellars were also characterized at strain level. Ninety six different combined patterns, i.e. 96 strains, were discriminated among the isolates analyzed, eight from which corresponded to commercial strains (233 isolates, 45% of the total biomass) evidencing some commercial S. cerevisiae strains are capable to remain in the environmental winery over a large period of time. On the other hand, the results reveal a great diversity of enological indigenous strains (88 different patterns among 290 isolates, R=3,29) and a higher variability within the S. cerevisiae population associated with CR area (R=2.08) than the ones associated with HC (R=3,53), Ch (R=3,84) and Ñ (R=7,00). Additionally, all spontaneous fermentations were carried out and completed by a few dominating strains (two to three) associated with a variable number of secondary strains. Some of these dominant indigenous strains remained in the environmental cellar over the period of time studied and they were also identified in conduced fermentations. Finally, the evaluation of the relatedness among strains using Principal Coordinates Analysis from combined molecular and killer data allowed the clustering of the indigenous S. cerevisiae strains into four populations significantly related to their origin areas. This finding suggests the need to select specific strains from each particular area within Comahue region.