Heritability and Number of Genes Controlling Leaf Rust Resistance in Four Cultivars of Wheat

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Abstract
Inheritance of leaf rust (Puccinia recondia) 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 population 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 40-45 F5 lines per cross were evaluated along 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.