Assignment of a PCR-amplified chitinase sequence cloned from Trichoderma hamatum to resolved chromosomes of potential biocontrol species of Trichoderma.

A 1424 bp DNA sequence containing the genetic determinants of the chitinase enzyme was identified in Trichoderma humatum by PCR amplification. High levels of similarity were observed between this sequence, named Th-ch (T. hamatum chitinase), and the 42 kDa chitinase genes known from T. harzianum. Chromosome-sized DNAs of five potential biocontrol species of Trichoderma were separated by pulsed-field gel electrophoresis. The total number of chromosomes was six in all the species, with sizes ranging from 3.7 to 7.7 Mb; estimated genome sizes were between 30.5 and 35.8 Mb. When fractionated chromosomes of the five species were probed with radiolabelled Th-ch, strong hybridization signals developed in all cases, but the physical position of these signals varied among species indicating a polymorphic chromosomal location of the highly conserved 42 kDa chitinase gene within the genus Trichoderma.