SummaryTwo wild‐type strains and three benomyl‐resistant mutants of the antagonistic ascomyceteTalaromyces flavuswere crossed in six combinations, two of which yielded hybrid cleistothecia. Parental strains and their ascospore progenies varied in several traits considered to play an important role in the capacity to control soilborne fungal pathogens: extracellular activities of glucose oxidase and cell‐wall degrading enzymes, antibiosis towardsVerticillium dahliae, and parasitism and biocontrol ofSclerotium rolfsii.A non‐Mendelian quantitative mode of inheritance was found for β‐1, 3‐glucanase and chitinase activities but only the latter exhibited a normal frequency distribution. Some of the progenies exhibited higher glucanase and chitinase activities than those found in the parental strains. Progeny analysis for chitinase, glucanase, cellulase, and glucose oxidase activities revealed no genetic association between any two of these enzymes. Antibiosis was correlated with glucose‐oxidase activity in one cross, but not in the other. The ability to reduce bean root rot caused byS. rolfsiiwas correlated with mycoparasitic activity againstS. rolfsiisclerotia in one cross, but not in the other. One out of the 20 progenies tested was able to reduce bean root rot more effectively than its parent strains, thus demonstrating the feasibility of improving a biocontrol agent by convent