Cellular and Molecular Mechanisms Involved in the Interaction between Trichoderma harzianum and Pythium ultimum.

The interaction between Trichoderma harzianum and the soilborne plant pathogen Pythium ultimum was studied by electron microscopy and further investigated by gold cytochemistry. Early contact between the two fungi was accompanied by the abnormal deposition of a cellulose-enriched material at sites of potential antagonist penetration. The antagonist displayed the ability to penetrate this barrier, indicating that cellulolytic enzymes were produced. However, the presence of cellulose in the walls of severely damaged Pythium hyphae indicated that cellulolytic enzymes were not the only critical traits involved in the antagonistic process. The marked alteration of the (beta)-1,3-glucan component of the Pythium cell wall suggested that (beta)-1,3-glucanases played a key role in the process.