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Effect of Trichoderma harzianum on Sporulation of Cochliobolus sativus on Excised Wheat Seedling Leaves. C. L. Biles, Graduate student, Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523, Present address: Department of Plant Pathology and Microbiology, Texas A & M University, College Station 77843; J. P. Hill, Associate professor, Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523. Phytopathology 78:656-659. Accepted for publication 13 November 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-656.

Wheat seedlings were spray-inoculated with a conidial suspension of Cochliobolus sativus (3 105 conidia 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 (5 107 conidia per milliliter) was spray-applicated to the infected wheat seedlings. After drying, individual lesions of C. sativus 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.

Additional keywords: biocontrol, common dryland root rot.