Mycoparasitism test
Microscopic inspection of the interaction zone in the slide cultures clearly showed that at an early state (two days after inoculation), 93% of the Trichoderma isolates established close contact with the pathogen by coiling around its mycelium. The coils were usually very dense and appeared to tightly encircle the hyphae of the pathogen. However at this stage the host cell surface was still mostly intact. When Trichoderma made contact with the host hyphae, it usually formed appressorium-like structures or hook-shaped contact branches. After contact with the host was established, several types of interactions occurred. In one of these, Trichoderma frequently grew parallel to the host and in contact with it. In another common type of interaction, Trichoderma coiled around the host. This coiling was either condensed or loose. Pronounced collapse of R. solani and loss of turgor were typical alteration about 10 days after inoculation. Breakdown of the cell wall of R. solani and hyphal disintegration were also occasionally seen. Later, the hyphae showed extreme shrinkage and shriveling. T. virens AS16-22 was the isolate that most strongly disintegrated the host hyphae. There was however no correlation between the intensity of Trichoderma coiling and hyphal disintegration.