PLOIDY IN THE ASPOROGENOUS YEAST CANDIDA MALTOSA, ISOLATION OF ITS AUXOTROPHIC MUTANTS AND THEIR CELL FUSION

Abstract

Auxotrophic mutants of an asporogenous yeast strain, Candida maltosa IAM12247, were selected after mutagenesis. In spite of our efforts to generate an array of auxotrophic mutants, only two groups of adenine. auxotrophs, histidine auxotrophs and leucine auxotrophs, were obtained. The nuclear DNA content of this species was measured by fluorescent microscope photometry. By this criterion and UV light irradiation inactivation experiments, C. maltosa was found to contain the same ploidy level as diploid strains of Saccharomyces cerevisiae. Unstable intraspecific and intergeneric prototrophic hybrids were obtained by the fusion between auxotrophic mutants of C. maltosa or between auxotrophic mutants of C. maltosa and S. cerevisiae. The stability and relative DNA content of these prototrophic hybrids are compared.