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Genetic Analysis of Resistance to Pyrenophora tritici-repentis Races 1 and 5 in Tetraploid and Hexaploid Wheat

First and second authors: Department of Plant Sciences, 166-Loftsgard Hall, North Dakota State University, Fargo 58105; third and fourth authors: Department of Plant Pathology, 306-Walster Hall, North Dakota State University, Fargo 58105; and fifth author: Department of Plant Sciences, 51-Campus Drive, University of Saskatchewan, Saskatoon, SK, S7N5A8, Canada.

Tan spot of wheat, caused by the fungus Pyrenophora tritici-repentis, is a destructive disease worldwide that can lead to serious losses in quality and quantity of wheat grain production. Resistance to multiple races of P. tritici-repentis was identified in a wide range of genetically diverse genotypes, including three different species Triticum aestivum (AABBDD), T. spelta (AABBDD), and T. turgidum (AABB). The major objectives of this study were to determine the genetic control of resistance to P. tritici-repentis races 1 and 5 in 12 newly identified sources of resistance. The parents, F₁, F₂, and F_2:3 or F_2:5 families of each cross were analyzed for the allelism tests and/or inheritance studies. Plants were inoculated at the two-leaf stage under controlled environmental conditions and disease reaction was assessed based on lesion-type rating scale. A single recessive gene controlled resistance to necrosis caused by P. tritici-repentis race 1 in both tetraploid and hexaploid resistant genotypes. The lack of segregation in the inter- and intra-specific crosses between the resistant tetraploid and hexaploid genotypes indicated that they possess the same genes for resistance to tan necrosis and chlorosis induced by P. tritici-repentis race 1. A single dominant gene for chlorosis in hexaploid wheat and a single recessive gene for necrosis in tetraploid wheat, controlled resistance to P. tritici-repentis race 5.

Additional keywords:host resistance, Triticum species.