Defense responses of cotton seedling to Trichoderma elicitors

Seedling damping-off is a major disease of cotton in various areas of Iran that damages to cotton fieldsevery year.Recently,Trichoderma spp. areconsidered as one of the biological agents forseedling damping-off controll.Induction of plant defensive system is the most important mechanism to biocontrol ofTrichoderma spp. In this study, extra-cellular flouids derived from culture filtrates of two isolatesof Trichoderma virensaseffective biocontrol on cotton seedling damping-offcausedby Rhozoctonia solaniisolate A224 andnoneffective biocontrolisolateA442 were studied. The characteristics of elicitation activity were assayed by peroxidase and gossypol level of rootlet extracts and were evaluated by colorimetric methods and spectrophotometer. Biochemical and physical aspects of elicitore compounds of culture filtrates were measured too.The results showed that culture filtrates from effective biocontrol isolate A224 of Trichoderma virens was found to stimulate elicitore compounds (peroxidase and gossypol) in cotton radicle than noneffective biocontrolisolateA442 of T.virens.The results confirmedthese elicitors were found to be heat stable, insoluble in chloroformand sensitive to treatment by proteinase K. The elicitors are most likely proteins or glycoproteins.