The Infection Mechanisms And Toxins Of Exserohilum Monoceras On Echinochloa Crus-galli

Seventeen strains of Exserohilum monoceras isolated from the diseased leaves of Echinochloa curs-galli occurring in thirteen different places were gained. The objects of this study were to determine its infection process, pathological characters and toxins. We observed the infection process and lesions on leaves of E. crus-galli damaged by filtrate of E. monoceras, and concluded it may produce toxins; we compared the bioassay methods to select the strains 32, X27 and MC9 which could produce vast toxins; We determined conditions of toxins production of strain 32.The infection process showed that E. monoceras had high pathological action on E. crus-galli. The hypha began to form from the base point of the conidia 8 hours after inoculation. Penetration into E. crus-galli leaves by the hypha occurred through the stomata or randomized places 13 hours after inoculation. The whole infection process finished within 48 to 72 hours.We compared the different bioassay methods and found that the root and shoot growth control experiment was most optional. Strain 32, MC9, X27 had the highest control rate.For toxin production, the optimal conditions were: PGB liquid media, initial pH 5.5-6.0, initial inoculation 104 conidia/ml, temperature 28癈, 200rpm, seven days. The toxin productions was related to the conditions of mycelium growth.