Evaluation of Two Native Isolates of Trichoderma harzianum and Trichoderma atroviride against Plenodomus lingam, the Causal Evaluation of Two Native Isolates of Trichoderma harzianum and Trichoderma atroviride against Plenodomus lingam, the Causal Agent of Rapeseed Blackleg

In this research, the effect of Trichoderma harzianum and T. atroviride against P. lingam was investigated in the laboratory and greenhouse conditions. Laboratory tests were followed as dual cultures and testing of the fungal volatile compounds. In the greenhouse, the antagonistic effects of the isolates were tested through treating rapeseed seeds and rapeseed above-ground parts with the spore suspension of the isolates in 106 spore per ml. The experiments were conducted in complete randomized design with four replications. Percent of plant mortality and disease severity were assessed. Both isolates showed antagonistic activities against the fungal phytopathogen. The two isolates T. harzianum and T. atroviride could inhibit the growth of the pathogen by 58.6 and 71.4 respectively in dual culture. In volatile compound phase, percent of growth inhibition were 15-21% and 31-39% in 120 and 240 hours after culture. In greenhouse experiments, antagonistic species could significantly (P<0.01) reduce disease severity compared to control. The greenhouse results revealed that in the seed treatment experiment, Trichoderma isolates decreased the rapeseed blackleg to 42.5 and 47.5℅, respectively after two weeks. Treating the above-ground parts with isolates T. harzianum and T. atroviride were significantly decreased the disease rate to 63.13 and 78.79℅, respectively. So both Trichoderma species can biologically inhibit canola black leg, but T. atroviride was for the first time more effective than another one.