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Identification of Stripe Rust Resistance Genes in Wheat Genotypes Used to Differentiate North American Races of Puccinia striiformis. Xianming Chen, Research associate, Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430; Roland F. Line, plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Pullman, WA 99164-6430. Phytopathology 82:1428-1434. Accepted for publication 10 August 1992. 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, 1992. DOI: 10.1094/Phyto-82-1428.

Crosses were made among wheat (Triticum aestivum) cultivars used to differentiate North American races of Puccinia striiformis and between those cultivars and other cultivars with known resistance genes. Seedlings of the parents and F1, F2, and backcross progeny from some crosses were evaluated for stripe rust resistance; eight North American races of P. striiformis were used. According to the data, Chinese 166, Heines VII, Fielder, Lee, Riebesel 47/51, and Moro have stripe rust resistance genes Yr1, Yr2, Yr6, Yr7, Yr9, and Yr10, respectively; and a gene in Lemhi, a gene in Tyee, and one of two genes each in Heines VII, Moro, Druchamp, Stephens, Lee, and Fielder is different from named Yr genes and other previously described genes. The gene in Lemhi may be allelic or closely linked to a gene in Riebesel 47/51 and one of the genes in Druchamp and Stephens. A gene in Heines VII may be allelic or closely linked with genes in Cappelle Desprez, Nord Desprez, and Stephens. Druchamp, Stephens, and Yamhill have either Yr3a or Yr4a. Druchamp has a common gene with Stephens, but not with Yamhill. Yamhill (Heines VII/Alba) has Yr2 from Heines VII and two genes from Alba. One of two genes of Lee, which is not Yr7, may be the same as or closely linked to a gene in Paha. Yr1, Yr7, Yr9, Yr10, the gene in Lemhi, and one gene in Paha were dominant. The second gene in Lee and a gene in Paha, which may be alleles, were recessive. Yr2, Yr6, Yr3a, or Yr4a, the gene in Tyee, and one of the two genes each in Stephens, Druchamp, and Fielder were dominant or recessive depending on the race and parent (genetic background) in the cross. Yr1 in Chinese 166, Yr9 in Riebesel 47/51, the gene in Lemhi, and the gene in Tyee were independent (i.e., they showed no interactions with other resistance genes). The remaining resistance genes in the North American differential cultivars showed various interactions with other resistance genes. Expression of epistasis also varied depending on race and genetic background.

Additional keywords: specific resistance, virulence, yellow rust of wheat.