New Hybrids betweenSaccharomycesSensu Stricto Yeast Species Found among Wine and Cider Production Strains

Abstract

Two yeast isolates, a wine-making yeast first identified as a Mel+ strain (ex. S. uvarum) and a cider-making yeast, were characterized for their nuclear and mitochondrial genomes. Electrophoretic karyotyping analyses, restriction fragment length polymorphism maps of PCR-amplified MET2 gene fragments, and the sequence analysis of a part of the two MET2 gene alleles found support the notion that these two strains constitute hybrids between Saccharomyces cerevisiae andSaccharomyces bayanus. The two hybrid strains had completely different restriction patterns of mitochondrial DNA as well as different sequences of the OLI1 gene. The sequence of the OLI1 gene from the wine hybrid strain appeared to be the same as that of the S. cerevisiae gene, whereas theOLI1 gene of the cider hybrid strain is equally divergent from both putative parents, S. bayanus and S. cerevisiae. Some fermentative properties were also examined, and one phenotype was found to reflect the hybrid nature of these two strains. The origin and nature of such hybridization events are discussed.

Evidence for multiple interspecific hybridization in sensu stricto species

“…The AFLP results also con¢rm that CID1 and S6U contain DNA from both S. cerevisiae and S. bayanus strains [12], but their genome structure appears quite different. CID1 has a signi¢cant amount of DNA that is distinct from the S. cerevisiae and S. bayanus genomes.…”

“…Saccharomyces pastorianus strains were originally derived from a hybridization between S. cerevisiae with either a Saccharomyces bayanus strain or another related species [6^10]. More recently, wine yeast S6U, cider yeast CID1, and the type strain of S. bayanus CBS 380 T have been described as possessing nuclear genomes from both a S. cerevisiae and a S. bayanus-like yeast [11,12].…”

Evolutionary relationships between the former species and the hybrids and ; reinstatement of (Beijerinck) as a distinct species

“…MCYC 623 and 623-6c have been used in three sequencing projects from which sequences were labelled S. bayanus [16][17][18]. Natural hybrids CID1 [19] and S6U [20] were from Piškur, and constructed hybrid (S. uvarum/S. cerevisiae) H1 was from Rainieri and co-workers [21].…”

Characterization of natural hybrids ofSaccharomyces cerevisiaeandSaccharomyces bayanusvar.uvarum

“…uvarum. Indeed, these two species have very different karyotypes (Naumov et al, 1993;Vaughan-Martini et al, 1993;Kishimoto et al, 1994;Rainieri et al, 1999), and different restriction patterns of the MET2 alleles (Hansen & Kielland-Brandt, 1994;Masneuf et al, 1998); also, Ty1 transposons are specific to the S. cerevisiae genome but not present in S. bayanus var. uvarum (Neuvéglise et al, 2002).…”