Abstract

The amylolytic yeast Saccharomycopsis fibuligera is the pre-dominant yeast in the starter product, nuruk, which is utilized for rice wine production in South Korea. Latest molecular studies explore a recently developed interspecific hybridiza-tion among stains of S. fibuligera with a unique genetic fea-ture. However, the origin of the natural hybridization occur-rence is still unclear. Thus, to respectively distinguish paren-tal and hybrid strains, specific primer sets were applied on 141 yeast strains isolated from different nuruk samples fer-mented in different provinces. Sixty-seven strains were de-fined accordingly as parental species with genome A while 8 strains were defined as hybrid strains. Unexpectedly, another parental species with genome B could not be found among the strain pools yet. Furthermore, it was observed that hybrid strains are phenotypically different from A genome strains; asci containing tetrad ascospores were observed in A genome strains more frequent than in hybrid strains. Nevertheless, hybrid strains were slightly more thermotolerant than A ge-nome strains. Interestingly, all hybrid strains were located only in Jeju province. Based on these sets of data, we specu-lated that the unique climate of Jeju province might play an evolutionary role in the interspecific hybridization between A genome strains, as well as the unculturable allopatric B ge-nome strains.

• Keywords: APL1; asci; Jeju; natural hybridization; nuruk; Sac-charomycopsis fibuligera; thermotolerant