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

Saccharomycopsis fibuligera is a dimorphic yeast, which is both saccha rolytic and fermentative, that is used in the production of rice wine. It has a predominant diploid phase. When grown on solid agar S. fibul igera strains develop different morphological forms. In previous studi es, intergeneric hybrids between S fibuligera and a related yeast, Yar rowia lipolytica, were obtained which were able to utilize starch and tributyrin. A putative haploid mitotic segregant, N14i60 met, was obta ined from the intergeneric hybrid between S. fibuligera 193 met and Y. lipolytica A his1. Auxotrophic mutants were readily isolated followin g UV mutagenesis of N14i60 met. The auxotrophic mutants and N14i60 hav e a similar morphology. Protoplast fusants were produced between the a uxotrophic mutant A6 met lys1 arg1 and Y. lipolytica 21501-4 B lys5 le u2 ade1 xpr2 and between specific pairs of the auxotrophic mutant stra ins. 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 consiste nt with their specific positions in the pedigree chart could be clearl y distinguished. Furthermore, by a study of the patterns of hybridizat ion signals for specific genes of S. fibuligera for an intergeneric hy brid and its mitotic segregants, genetic segregants with different cha racteristics were obtained. The segregants from the intergeneric hybri d and the protoplast fusants probably arose by a process of chromosoma l assortment at mitosis. The intergeneric hybrid, the protoplast fusan ts and their mitotic segregants showed a similar karyotype. Together t hese studies provide an explanation for the basis of phenotypic differ ences of some of the yeast strains studied.