A Novel Method for Breeding Polyploid Cells by Heat-induced Endomitotic Diploidization in Saccharomyces cerevisiae

Endomitotic diploidization occurred as a result of heat treatment of spores during germination of the industrial yeast S. cerevisiae. Polyploid cells were obtained in both heterothallic and homothallic strains. In the heterothallic strains, the resultant diploid cells, with the ability to mate, were used to construct tetraploids. In the homothallic strains, tetraploid cells were obtained directly after a mating-type switch. In each strain, the highest frequency (approximately 10% of viable cells) of diploidization was obtained when spores were cultured for 30 min in liquid medium to initiate germination followed by subsequent heat treatment at 55°C for 10min.