INHERITANCE OF STRIPE RUST RESISTANCE IN WHEAT CULTIVARS USED TO DIFFERENTIATE RACES OF PUCCINIA-STRIIFORMIS IN NORTH-AMERICA

Inheritance of stripe rust resistance in 13 wheat (Triticum aestivum) cultivars used to differentiate races of Puccinia striiformis in North America was determined using nine North American races of the pathogen. The differential cultivars, which were resistant to specific races, were crossed with cultivars susceptible to the specific races. We found that Lemhi, Chinese 166, Riebesel 47/51, and Tyee each have a single resistance gene; Heines VII, Moro, Druchamp, Produra, Stephens, Lee, and Fielder each have two resistance genes; and Paha and Yamhill each have three resistance genes. Of the 24 resistance genes, each differential cultivar has at least one gene that is different from the genes in the other differential cultivars. Some of the cultivars may also have common genes. The genes in Lemhi, Chinese 166, Heines VII, Moro, and Riebesel 47/51, and one of the genes in Paha and in Lee were dominant. The two genes in Produra, one of the genes in Lee, and at least one of the genes in Paha were recessive. The single gene in Tyee and both genes in Druchamp, Fielder, and Stephens were dominant or recessive depending on the race, parent in the cross (genetic background), interaction of race and parent, and duration of infection. Various epistatic interactions were observed. This information should be useful in evaluating germ plasm for resistance, monitoring races of the pathogen, determining the relationships of races to one another, and developing new cultivars with more effective stripe rust resistance.