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 hybridizati on 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/R FLP analysis of the MET2 gene (chr. XIV). Monosporic progeny of strain S6U was highly viable in first generation but completely nonviable in the secon d one. According to the genetic analysis, sherry strain S. cerevisiae SBY 2 592 was found to be an autotetraploid heterozygous for homo-heterothallism.