Molecular mapping and detection of the yellow rust resistance gene Yr26 in wheat transferred from Triticum turgidum L. using microsatellite markers

Yellow rust (stripe rust), caused by Puccinia striiformis Westend f. sp. tritici, is one of the most devastating diseases of wheat throughout the world. Wheat-Haynaldia villosa 6AL.6VS translocation lines R43, R55, R64 and R77, derived from the cross of three species, carry resistance to both yellow rust and powdery mildew. An F-2 population was established by crossing R55 with the susceptible cultivar Yumai 18. The yellow rust resistance in R55 was controlled by a single dominant gene, which segregated independently of the powdery mildew resistance gene Pm21 located in the chromosome 6VS segment, indicating that the yellow rust resistance gene and Pm21 are unlikely to be carried by the same alien segment. This yellow rust resistance gene was considered to be Yr26, originally thought to be also located in chromosome arm 6VS. Bulked Segregation Analysis and microsatellite primer screens of the population F-2 of Yumai 18 x R55 identified three chromosome 1B microsatellite locus markers, Xgwm11, Xgwm18 and Xgwm413, closely linked to Yr26. Yr26 was placed 1.9 cM distal of Xgwm11/Xgwml8, which in turn were 3.2 cM from Xgwm413. The respective LOD values were 21 and 36.5. Therefore, Yr26 was located in the short arm of chromosome 1B. The origin and distribution of Yr26 was investigated by pedigree, inheritance of resistance and molecular marker analysis. The results indicated that Yr26 came from Triticum turgidum L. Three other 6AL.6VS translocation lines, R43, R64 and R77, also carried Yr26. These PCR-based microsatellite markers were shown to be very effective for the detection of the Yr26 gene in segregating populations and therefore can be applied in wheat breeding.