Isolation of uracil auxotrophic mutants of Trichoderma harzianum and their transformation with heterologous vectors

Nine uracil auxotrophic mutants were isolated from a mycoparasitic strain of Trichoderma harzianum. One of these could be transformed with the pKIM7 cosmid, which contained the pyr‐4 gene of Neurospora crassa. Another uracil‐requiring mutant was transformed with heterologous vectors containing the orotate pyrophosphoribosyl transferase genes of Podospora anserina and Trichoderma reesei. The transformation frequencies varied between 150 and 1000 μg−1 plasmid DNA. Hybridization analysis of the transformants revealed distinct locations of integrated vectors in the genomes, but in some transformants freely replicating plasmids could also be detected.