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Effect of Wheat Genotype, Leaf Position, Growth Stage, Fungal Isolate, and Wet Period on Tan Spot Lesions. R. M. Hosford, Jr., Professor, Department of Plant Pathology, North Dakota State University, Fargo 58105. J. G. Jordahl, and J. J. Hammond. Research Specialist II, Department of Plant Pathology, and Professor, Department of Crop and Weed Science, North Dakota State University, Fargo 58105. Plant Dis. 74:385-390. Accepted for publication 21 December 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/PD-74-0385.

Resistance was related to wheat genotype, with 11 of 59 Chinese wheats more resistant to Pyrenophora tritici-repentis than resistant genotype BH1146, as expressed by lesion length rating. Resistance decreased with aging of the leaf. These findings were generally consistent for three highly aggressive fungal isolates. Increasing postinoculation foliage wet period related to increasing lesion size, with resistant genotypes acting similarly but further separating for degree of resistance.

Keyword(s): CIMMYT, Drechslera tritici-repentis, Helminthosporium tritici-repentis, Pyrenophora trichostoma, yellow leaf spot.