VARIATION OF ELECTROPHORETIC KARYOTYPES IN GENETICALLY DIFFERENT STRAINS OF SACCHAROMYCOPSIS-FIBULIGERA AND YARROWIA-LIPOLYTICA

Saccharomycopsis fibuligera is a dimorphic yeast, which is both saccharolytic and fermentative, that is used in the production of rice wine. It has a predominant diploid phase. When grown on solid agar S. fibuligera strains develop different morphological forms. In previous studies, intergeneric hybrids between S fibuligera and a related yeast, Yarrowia lipolytica, were obtained which were able to utilize starch and tributyrin. A putative haploid mitotic segregant, N14i60 met, was obtained from the intergeneric hybrid between S. fibuligera 193 met and Y. lipolytica A his1. Auxotrophic mutants were readily isolated following UV mutagenesis of N14i60 met. The auxotrophic mutants and N14i60 have a similar morphology. Protoplast fusants were produced between the auxotrophic mutant A6 met lys1 arg1 and Y. lipolytica 21501-4 B lys5 leu2 ade1 xpr2 and between specific pairs of the auxotrophic mutant strains. Differences and similarities in the DNA banding patterns of these genetically different strains of S. fibuligera and Y. lipolytica were demonstrated and it was established that four distinct types consistent with their specific positions in the pedigree chart could be clearly distinguished. Furthermore, by a study of the patterns of hybridization signals for specific genes of S. fibuligera for an intergeneric hybrid and its mitotic segregants, genetic segregants with different characteristics were obtained. The segregants from the intergeneric hybrid and the protoplast fusants probably arose by a process of chromosomal assortment at mitosis. The intergeneric hybrid, the protoplast fusants and their mitotic segregants showed a similar karyotype. Together these studies provide an explanation for the basis of phenotypic differences of some of the yeast strains studied.