Complementation in Nonconidiating Mutants of Trichoderma

Nonconidiating (Con(-)) mutants were isolated from wild-type and color mutants of the fungus Trichoderma viride Pers. ex Fries. Heterokaryons were easily produced and maintained, and the complementation relationships among the Con(-) mutants were established. Most Con(-) mutants could complement one or more of the other Con(-) mutants. When marked Con(-) mutants were mixed with marked Con(+) testers, conidiating heterokaryons were formed. The conidia thus obtained produced only the parental type colonies after replating, indicating that nonconidiation is a nuclear characteristic. Allowing two Con(-) colonies to meet and produce a heterokaryon, it was found that the migration of nuclei reached a rate of 5 mm per hr, which is several times greater than the rate of hyphal elongation; it was also found that heterokaryosis of a mycelial region preceded its ability to conidiate.