A novel method for hybridization of Saccharomyces species without genetic markers

Protoplasts of Saccharomyces cerevisiae were inactivated by treatment with different concentrations of antifungal compounds for various periods. Of th e 14 compounds tested, N-ethylmaleimide proved to be the most efficient. Th e inactivation effect was fully reproducible. The inactivated protoplasts c ould be reactivated and still function as fusion partners. They were fused with untreated protoplasts by polyethylene glycol treatment and produced vi able hybrid cells. Nuclear and extrachromosomal genetic analysis and chromo some separation of the fusion products from fusion experiments involving in activated and non-inactivated protoplasts revealed that N-ethylmaleimide di d not affect either of the genomes and hence it was perfectly suited for th e hybridization of any type yeast cells without genetic markers.