Inter- and intra-species crosses between Candida albicans and Candida guilliermondii

Hybridization was shown to occur both between strains of the imperfect diploid yeast Candida albicans and between C. albicans and the distantly related haploid yeast Candida (Pichia) guilliermondii. Prototrophic hybrids were selected from crosses of multiply marked auxotrophic mutants of the two species. In most cases, mild ultraviolet irradiation of the C. albicans partner was required. Examination of auxotrophic markers in segregants from the hybrids indicated that recombination, rather than heterokaryon formation, had occurred in these crosses. The DNA content of the hybrids varied from diploid or aneuploid (for crosses between C. albicans and C. guilliermondii) to triploid (for C. albicans x C. albicans). It seems possible that genetic exchange analogous to this may occur in nature.