Fingerprinting reveals gamma-ray induced mutations in fungal DNA: implications for identification of patent strains of Trichoderma harzianum.

We have analyzed different patent strains and gamma-ray induced mutants of Trichoderma harzianum by DNA fingerprinting and PCR fingerprinting (RAPD). Applying wild-type phage M13 DNA, with the oligonucleotides (CT)8 and (GTG)5 as probes for hybridization, as well as the oligonucleotides GGCATCGGCC, (GTG)5, (CAC)5 and the M13 sequence GAGGGTGGCGGTTCT as primers in PCR, we were able to obtain different and discriminative fingerprint patterns for all strains and mutants investigated. Irradiation of fungi led to mutations which resulted in new fingerprint patterns. Consequently, irradiation-induced mutants can be clearly distinguished from the original wild-type isolates by genomic fingerprinting which is of importance for the patent protection of fungal strains. Sequencing of the ITS-1 and ITS-2 regions of the rDNA gene complex revealed the same sequence for all mutant strains and the original wild-type strain.