due to their cornpfex genetic background, industrial strains are typícally unsuitable for genetic engineering (12)-Instead, traditíonal breeding techniques other tftan genetic engineering. SUCH as na EurcrJ and chemica+ 1lphysical mutation. protoplast fusion. Genome shuMing. And mating. Are cornmonly used for improvement of indutrial sEra · ins. Acfditioin. Techniques other than genetic engineerng are tisuaMy much more efïecEive at improving traits for which tfre gerJefic meehan, isms are still unclear, such as acidfo-JeraËnce and thermo-tolerance. In this udy, acfd-and thermo-tolerance of the diploid strain WW, which is descended from the flocculating industrial strain KFwere improved by evolution through continuous fermentation foMowed by haploidization and mating Continuous fermentation under acidic or high-tiemperature conditions was carried out to obtain mutants with improved acid-or thermotolerance. Håploids of these diploid mutants were then obtained Ehrouglt tetrad Split Eo permit mating with each other for further improvement in both acid-and thermo-tolerance and for genetic analyses to identify responsible genes and mutations involved in the phenotype of acïid-tolerance and thermo-tolerance in industrial rains.