Identification of new chromosomes of Saccharomyces bayanus using gene probes from S. cerevisiae

Molecular genetic study of introgression betweenSaccharomyces bayanus andS. cerevisiae

The genomic constitution of different S. bayanus strains and natural interspecific Saccharomyces hybrids has been studied by genetic and molecular methods. Unlike S. bayanus var. uvarum, some S. bayanus var. bayanus strains (the type culture CBS 380, CBS 378, CBS 425, CBS 1548) harbour a number of S. cerevisiae subtelomeric sequences: Y', pEL50, SUC, RTM and MAL. The two varieties, having 86-100% nDNA-nDNA reassociation, are partly genetically isolated from one another but completely isolated from S. cerevisiae. Genetic and molecular data support the maintaining of var. bayanus and var. uvarum strains in the species S. bayanus. Using Southern hybridization with species-specific molecular markers, RFLP of the MET2 gene and flow cytometry analysis, we showed that the non-S. cerevisiae parents are different in lager brewing yeasts and in wine hybrid strains. Our results suggest that S. pastorianus is a hybrid between S. cerevisiae and S. bayanus var. bayanus, while S. bayanus var. uvarum contributed to the formation of the wine hybrids S6U and CID1. According to the partial sequence of ACT1 gene and flow cytometry analysis, strain CID1 is a triple hybrid between S. cerevisiae, S. kudriavzevii and S. bayanus var. uvarum.

Natural polyploidization of some cultured yeast Saccharomyces sensu stricto: auto- and allotetraploidy

Using genetic and flow cytometric analyses, we showed that wine strain S6U is an allotetraploid of S. cerevisiae x S. bayanus. Hybrid constitution of the strain and its meiotic segregants was confirmed by Southern hybridization analysis of their chromosomal DNAs using four S. cerevisiae cloned genes: LYS2 (chr. II), TRK1 (chr. X), ARG4 (chr. VIII), ACT1 (chr. VI) and PCR/RFLP analysis of the MET2 gene (chr. XIV). Monosporic progeny of strain S6U was highly viable in first generation but completely nonviable in the second one. According to the genetic analysis, sherry strain S. cerevisiae SBY 2592 was found to be an autotetraploid heterozygous for homo-heterothallism.

Genetic reidentification of Saccharomyces strains associated with black knot disease of trees in Ontario and Drosophila species in California

Using genetic hybridization analysis, electrophoretic karyotyping, and Southern hybridization with the ADC1 promoter probe, three biological sibling species, Saccharomyces cerevisiae, Saccharomyces paradoxus, and Saccharomyces bayanus, have been identified in Ontario and California. Saccharomyces kluyveri strains were revealed by karyotyping.Key words: genetical taxonomy, sibling species, Saccharomyces complex, electrophoretic karyotyping.