The use of active dry yeasts is of particular interest to the wine industry, since the sensory properties of the final product vary considerably from one year to another depending of the microbial flora present on the grapes (Querol et al. 1990). It is generally assumed that indigenous yeasts are suppressed by the starter; however, different studies show that indigenous yeasts can still participate in the fermentation (Schiitz and Gafner 1993; Querol et al. 1992a), although an implantation of only 50% was observed when fermentations were conducted by some commercial strains (Esteve-Zarzoso et al. 2000). For these reasons, rapid and simple methods for the routine verification of yeast strain present in fermentations would be useful to check the implantation of the starter.
Classical taxonomy is based predominantly on phenotypic characteristics, such as metabolic and/or cell morphology (Kurtzman and Fell 1998). However, nutritional characteristics have been shown to be highly variable as well as mutable, and genetic crosses have linked the characteristics to one or only a few genes (Petersen et al. 2000), which in some
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