Isolation of Triploid Saccharomyces cerevisiæ

Abstract

THE production of tetraploids in a brewery yeast has been reported by Subramaniam and Krishna Murthy¹ and Mitra and Subramaniam², following treatment with acenaphthene and chrysene. These authors did not present genetic evidence to support their claim, which was based mainly on colony and other gross observations. Cytological evidence has recently been presented for a tetraploid with four chromosomes, derived from a “diploid two chromosome… strain”³. Tobias⁴ studied a yeast isolated after acenaphthene treatment in terms of survival after X-irradiation, and concluded that the isolate was tetraploid. DeLong and Lindegren⁵ have characterized certain strains of Saccharomyces cerevisiæ as triploid and tetraploid, based on the shapes of survival curves after ultra-violet irradiation. A paper by Lindegren and Lindegren⁶ has recently appeared, describing the production of tetraploid yeast by crosses of diploids homozygous for complementary mating types. We wish to give a preliminary report on a procedure for the isolation of pure triploid clones of S. cerevisiæ.