Study of the possibility of biological control of Phytophthora drechsleri damping factor in cucumbers by the isolates of Trichoderma spp. in greenhouse

Cucumber (Cucumis sativus) is one of the important commercial products in Iran and the world rich in fiber and vitamin with high nutritional value. It is continuously attacked by soil-borne pathogens that are not only cause significant economic damage to crop yield, but also reduce quality and marketable of product. One of the most important and destructive soil-borne diseases of cucumber, damping off and root rot and crown caused by Phytophthora drechsleri Tuker. In this study, isolates of three species of biocontrol fungus Trichoderma were evaluated in laboratory and greenhouse conditions. The antagonistic isolates of three species were including Trichoderma harzianum (isolates Th3, Th5, Th6, Th7, Th9), T. longibrachiatum (isolate Tl2) and T. atroviride (isolates Ta1 ,Ta4, Ta8, Ta10) respectively. Dual culture tests were carried out in a completely randomized design with 11 treatments in three replications. Th6 Isolate, with 89.3% in dual culture showed the highest inhibitory effect on the. Hyphae twisting of different isolates of Trichoderma spp. were not observed in contact with Phytophthora but Trichoderma hyphae grown in parallel with Phytophthora hyphae and form Appresorium and Haustarium. Based on the results of this research, the most successful isolates for antagonist activity against P. drechsleri Tuker were Th6, Th5, Th3 and Ta1. These four isolates were selected for greenhouse studies. In greenhouse, tests of soil treatment and seed contaminated with the spore suspension of Trichoderma isolates for evaluating the biocontrol isolates in a completely randomized design with 10 treatments and three replications were conducted. Results showed that the isolates were able to control the disease in different levels. In seed treatment, Th6 and Ta1 isolates with 91.75 and 83.5 percent and afterwards, Th3 and Th5 isolates were more effective in reducing disease in first taking notes after soil treatment respectively. In seed treatment, Th6 and Ta1 isolates were more successful than other isolates and in inoculated treatments with the isolates and Phytophthora, seed germination percentage were recorded as 83.34 and 100 % respectively. In general, the seed treatment was more effective in reducing disease in comparison with soil treatment. Isolates were also effective in increasing plant growth and however, Ta1 and Th6 isolates significantly increased plant weight and height.