Parasexual hybridization of yeasts by electric field stimulated fusion of protoplasts.

Under the action of a high electric field pulse a pronounced stimulation of yeast protoplast fusion initiated by polyethylene glycol and Ca (2+) ions was found. The fusion rate was enhanced by a factor of 200 for different genetically marked strains of the yeast Saccharomyces cerevisiae as compared with fusion without electric field treatment. Genetic evidence for fusion has been obtained by isolating parasexually produced hybrids resulting from combination of the genomes of both mutants.Our method allows the production of a large number of parasexual hybrids for different purposes.