Abstract
We investigated the occurrence of Trichoderma in the Oueslatia forest located in the centre-west of Tunisia, which represents a good example for studying a distribution of Trichoderma between different soil horizons of a forest with Mediterranean bioclimate. One hundred-five isolates obtained were identified at the genus level by analysis of morphological characters. The diversity of Trichoderma between soil horizons was evaluated by analysis of the internal transcribed spacer (ITS) of the rDNA region using restriction fragment length polymorphism (RFLP). The ITS region was first amplified by polymerase chain reaction (PCR) with specific primers and then cleaved with two restriction enzymes. Amplification products showed extensive length polymorphism and RFLP analysis generated bands ranging from 100 to 620 bp. The restriction profiles of the PCR products showed that HaeIII enzyme has more discriminatory power than RsaI A high degree of polymorphism was detected in rhizosphere rather than soil. Thus the RFLP analysis produced different DNA profiles on the gels denoting significant intraspecific genetic variation. Our data confirm the potential of ITS region PCR-RFLP for the study of polymorphism among Trichoderma population from different soil layers.