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Resistance

Inheritance of Resistance to Pseudocercosporella herpotrichoides in Three Cultivars of Winter Wheat. C. A. Strausbaugh, Graduate research assistant, Department of Plant Pathology, Washington State University, Pullman 99164-6430; T. D. Murray, assistant professor, Department of Plant Pathology, Washington State University, Pullman 99164-6430. Phytopathology 79:1048-1053. Accepted for publication 10 May 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1048.

Inheritance of foot rot resistance was studied in parental, F1, F2, and backcross populations of all possible crosses between the cultivars Daws (susceptible), Cappelle-Desprez (resistant), and VPM-1 (highly resistant) by using epidermal cell responses to determine the percent successful penetrations in the first-leaf sheath. One semidominant gene for resistance with a narrow-sense heritability (Hn) = 0.34 segregated in the Cappelle Daws cross; one dominant gene for resistance with Hn = 0.35 segregated in the VPM-1 Daws cross; and two genes for resistance exhibiting overdominance with Hn = 0.77 segregated for resistance in the VPM-1 Cappelle cross. Based on quantitative estimates, VPM-1 contains one gene for hypersensitivity not found in Cappelle-Desprez. Maternal effects were not evident in any of the crosses. The gene action of the resistance genes in the Cappelle Daws and VPM-1 Daws crosses fit an additive-dominance model, while the VPM-1 Cappelle cross was best fit by a model that included a digenic interaction. The rating system that resulted in the highest heritabilities was based on penetrations stopped by papillae or within epidermal cells in both hypersensitive and nonhypersensitive cells. Ratings derived from these epidermal cell responses are correlated with field resistance of parents, genetically associated with resistance in segregating progeny, and may be useful for screening potential cultivars.