Genetic and Cytogenetic Studies of Stem Rust, Leaf Rust, and Powdery Mildew Resistances in Hope and Related Wheat Cultivars

Abstract

Three linked genes responsible for resistance respectively to stem rust, to leaf rust, and to powdery mildew are located on chromosome 7B of ''Hope'' wheat. The gene for stem rust resistance, operative in seedling and adult plant stages, is recessive and is designated sr17. The incompletely dominant gene for resistance to leaf rust, designated Lr 14, showed 18% recombination with srl7, while in 2 different crosses recombination estimates of 6.0 and 2.5%, respectively, were obtained for the recessive gene for mildew resistance and srl7. All 3 genes were present in a high proportion of "Hope" and H-44 derivatives. The gene sr17 is apparently ineffective in conferring resistance to North American and pre-1954 Australian stem rust strains. Its incorporation into several cultivars selected for resistance to these strains presumably resulted from gene interactions or linkage with genes for resistance to other diseases.