One of the issues that most concerns to both winemakers and producers of active dry yeasts is the stuck and sluggish fermentations of grape musts with high levels of sugar, reflecting the inability of inoculated yeast strain to complete the fermentation process. It is difficult to obtain a wine strain that possesses both adequate oenological and technological properties; thus, the correct approach to solving these problems is the application of breeding programs primarily focused on both properties. The first step toward this process is to characterize the phenotypic diversity between potential parental strains. In the present study, we have analyzed the fermentative behavior of 26 Saccharomyces cerevisiae wine strains in high-sugar conditions at 20 degrees C, using a range of tests, such as sporulation ability, spore viability, and tetrad analysis to determine the tolerance of these yeasts to several stress conditions. Most tested strains were homothallic and heterozygous for more than one character. Two auxotrophic derivatives with defects in amino acid or nucleic acid metabolism were obtained, and these strains could potentially be used for the development of hybridization techniques without using laboratory strains.