Effect ofTrichoderma harzianumon Sporulation ofCochliobolus sativuson Excised Wheat Seedling Leaves

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Abstract
Wheat seedlings were spray-inoculated with a conidial suspension of Cochliobolus sativus (3 .times. 105 condidia per milliliter), placed in a mist chamber for 24 hr, and transferred to a greenhouse bench for observation of lesion development. Seven days later, a conidial suspension of Trichoderma harzianum (5 .times. 107 conidia per milliliter) was spray-applicated to the infected wheat seedlings. After drying, individual lesions of C. sativa were excised, and the fungus was induced to sporulate in petri dishes lined with moist filter paper. Six days later, conidia from the lesions were counted. The sporulation capacity (number of conidia produced per 15 lesions) of C. sativus in lesions treated with T. harzianum was significantly less than in lesions treated with distilled water at 26 and 32 C but not at 21 C. Sporulation capacity of the fungus was reduced when treated with T. harzianum as compared with water controls in lesions on winter wheat cultivars Baca, Newton, Scout 66, and Vona but not on durum cultivars Calvin and Vic. Subsequent tests revealed a significant inverse correlation in the sporulation capacity of lesions of C. sativus on cultivar Scout 66 with application of various conidial suspension concentrations of T. harzianum.