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Heritability and Number of Genes Controlling Leaf Rust Resistance in Four Cultivars of Wheat. M. E. Bjarko, Former graduate student, Department of Plant Pathology, Washington State University, Pullman 99164-6430; R. F. Line, Plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Pullman 99164-6430. Phytopathology 78:457-461. Accepted for publication 19 October 1987. 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, 1988. DOI: 10.1094/Phyto-78-457.

Inheritance of leaf rust (Puccinia recondita) resistance in wheat (Triticum aestivum) was evaluated in two slow leaf-rusting cultivars (Borah and Wampum), a highly resistant cultivar (Wared), and a susceptible cultivar (Twin) using area under the disease progress curve as a measure of leaf rust resistance. Parental and F1, F2, and backcross populations of all possible single crosses between the four cultivars were evaluated in the field on a single plant basis in 1984, and 100 F3 lines and 4045 F5 lines per cross were evaluated along with the parents in 1986. No discrete phenotypic classes were observed in the segregating populations of any cross. Based on quantitative analyses, each resistant cultivar contained at least two to three genes for leaf rust resistance, and the genes in each cultivar were different from those in the other two cultivars. Heritability estimates for leaf rust resistance, using three methods, ranged from 0.74 to 0.92 for Wared, 0.42 to 0.70 for Wampum, and 0.33 to 0.55 for Borah, when crossed with Twin. The cross between Borah and Wampum resulted in the lowest heritability estimates.

Additional keywords: durable resistance, slow rusting.