In vitro Antagonistic Activity of Trichoderma harzianum against Rhizoctonia solani The Causative Agent of Potato Black Scurf and Stem Canker

IN EGYPT Potato (Solanum tuberosum L.) is considered one of the most important vegetable crops as well as many others countries in the world. It plays an important role in the Egyptian agricultural economy, not for local consumption but also for exportation especially to Europe, Russia and Arabic countries. However, potato crop suffer from more than 40 pests and diseases caused by insects, nematodes, viruses, bacteria and fungi, of which black scurf and stem canker induced by Rhizoctonia solani is probably the most serious disease. The world yield losses caused by R. solani were estimated to 5-15%. R. solani is an unspecialized parasite, survive in soil in the absence of host plant and make itself a very difficult pathogen to manage. Reduction or elimination of soil borne inoculum is the only effective solution to overcome the problem and this may be achieved through the application of various control measures of which fungal antagonists consider among the most important tactic. Although R. solaniis usually controlled through the application of chemicals, the serious ecological and financial toll of this fungus has prompted for research on biopesticides as a viable alternative. Trichoderma spp. were well-known fungi often used for the biological control of crop pests, whose anti-fungal mechanisms include competition for the substrate, antibiosis and/or mycoparasitism. Five isolates of Trichoderma harzianum were tested in vitro for their antagonistic potential against Rhizoctonia solani. Both Trichoderma harzianum and Rhizoctonia solani were identified by molecular and morphological methods. In dual culture of all isolates were found antagonistic to the growth of R. solani. The hyphal interaction studied using light microscopy revealed destructive mycoparasitism of R. solani by T. harzianum. The method of mycoparasitism was sparse to intense coiling of R. solani followed by disintegration, disorganization and death of R. solani mycelium.