NOVELTY - Improving a yeast strain of industrial interest, comprises: (a) transferring the yeast of a rich medium to a sporulation medium, (b) incubating the yeast in sporulation medium for a time sufficient to induce the formation of double-strand Spol 1-dependent breaks; (c) contacting the yeast with a source of carbon and nitrogen until the reductional segregation of chromosomes of a first meiotic division to obtain recombinant yeast; (d) recovering the recombinant yeast; and (e) screening or selecting the recombinant yeast to identify those having desired improvement.    USE - The method is useful for improving an yeast strain of industrial interest, preferably a sterile hybrid strain using RTG process to identify or locate a genetic information coding for a characteristic of interest, where: the yeast strain of industrial interest is useful for food industry, biofuel production, production of molecules of interest and degradation of the cellulose or lignocellulosic biomass; the yeast strain of industrial interest is a non-genetically modified organism, a hybrid yeast, a diploid yeast, preferably a diploid hybrid yeast, or a diploid hybrid sterile strain; the yeast strain of industrial interest is Saccharomyces cerevisiae; the characteristic of interest or desired improvement includes growth rate, thermotolerance, cryotolerance, pH sensitivity, fermentation capacity, fermentation speed, ethanol resistance, resistance to a particular compound present in the fermentation medium or excreted by cell culture, cell morphology, flocculating character, sensitivity to a particular molecule, sporulation efficiency, flavor profiles, nutritional requirements, resistance to drying, and the fermentation of a particular sugar (all claimed); the molecules of interest include vitamins, antibiotics, vaccines, enzymes and steroid hormones; and the yeast strain of industrial interest is useful as fermentation agent in baking, brewing and or wine distilling industries.    ADVANTAGE - The method is capable of economically improving the yeast strain of industrial interest without using the recombinant DNA techniques.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) use of return to growth (RTG) process of yeast for improving a yeast strain of industrial interest, where RTG process is induced by the steps (a)-(c);    (2) a method-1 for generating a library of recombinant yeast from the yeast, comprising the steps (a)-(c) as above per se, and recovering the recombinant yeast to form a bank of recombinant yeasts;    (3) a bank of recombinant yeast obtained by the process; and    (4) a method-2 to identify or locate a genetic information coding for a characteristic of interest, preferably a quantitative character of interest in yeast, comprising the steps (a)-(d) as above per se, and the analysis of genotypes and phenotypes of the recombined yeast to identify or locate the genetic information coding for the characteristic of interest.