Biological control of crown rot disease of canola by isolates of Trichoderma in vitro and under greenhouse conditions

 Crown rot disease caused by Sclerotinia sclerotiorum, is one of the major diseases of canola worldwide. Biological control is a control method in agriculture for living organisms, especially fungi and bacteria, and is used in order to control plant damages caused by harmful factors. In this research, we evaluated the effect of seventy one isolates of Trichoderma spp. against S. sclerotiorum using various in vitro methods including dual culture and slide culture methods. Based on the obtained results of in vitro studies, six Trichoderma isolates and Tebuconazole fungicide were selected in order to study their potentials for controlling the crown rot disease in greenhouse. For this purpose, rapeseed petals were inoculated with S. sclerotiorum and inoculation of suspensions of Trichoderma isolates was done after inoculation of pathogen and also before and after its inoculation and then the severity of the disease was determined in the studied treatments. Based on obtained results, in dual culture, ARCTr281 (T. harzianum) was the most effective isolate for inhibition of mycelial growth. In hyperparasitism test, all isolates of T. harzianum hade successful performance in controlling the pathogenand coiling of Trichoderma was observed around the hyphae of S. sclerotiorum. Lowest disease incidence and severity of disease was observed in the negative control (without Sclerotinia and Trichoderma). Inoculated fungi in two stages, effectively were able to reduce the incidence and severity of disease in leaves and stems that ARCTr281 (T. harzianum) was the most effective fungus under greenhouse conditions. Also, the use of Trichoderma isolates in two stages in presence of pathogen caused an increase in height, fresh and dry weight of the shoot and root under greenhouse conditions. Analysis of variance and comparing the average characters by Least Significant Difference (LSD), Duncan and nonparametric method showed significant difference between used fungi in dual culture and greenhouse studies. According to the results of biocontrol studies under laboratory and greenhouse conditions, ARCTr281 and ARCTr272 fungal isolates belonging to T. harzianum were the most effective antagonists for control of canola's crown rot disease. The results of this study indicated that different isolates of Trichoderma can be considered as potential antagonists for the management of canola's crown rot disease.