A strain of Trichoderma viride pathogenic to germinating seedlings of cucumber, pepper and tomato

An isolate of Trichoderma viride from the surface of an apparently healthy tomato root was found to be pathogenic to seedlings of cucumber, pepper and tomato in laboratory and greenhouse experiments. In laboratory experiments, when seeds of each host species were inoculated with conidia of the pathogen, the subsequent growth of seedlings was decreased and they developed light‐brown water‐soaked lesions on their roots and crowns. The pathogen could be re‐isolated from lesions on the seedlings, and microscopic examination of inoculated seedlings demonstrated that the fungus invaded the vascular tissues of the young seedlings. Culture filtrates of T. viride were found to contain a heat‐stable factor that caused a decrease in the growth of the roots of young cucumber, pepper and tomato seedlings. In greenhouse experiments, the fungus did not affect germination or seedling fresh weight of young cucumber seedlings in soil‐ peat‐ or rockwool‐based germinating media, but 10% of seedlings germinated in rockwool showed signs of infection. This is the first report of T. viride being pathogenic on pepper and tomato.