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The quantitative trait loci QYr.sun-3BS and QYr.sun-4DL were identified in the W195/BTSS recombinant inbred line (RIL) population in a previous study. QYr.sun-3BS explained 34 to 59% phenotypic variation in stripe rust response. We evaluated parental genotypes at different growth stages and temperature regimes to detect the critical stage for expression of QYr.sun-3BS. W195 expressed low infection type (IT) ;1C at the fourth leaf stage, when incubated at 21 ± 2°C and the alternate parent BTSS was susceptible (IT 3). Monogenic segregation for stripe rust response was observed among the RIL population at the fourth leaf stage and the underlying locus was temporarily named YrW195. YrW195 corresponded to QYr.sun-3BS. Since no previously designated stripe rust resistance genes that expresses at and after the fourth leaf stage was mapped in this region, YrW195 was formally named Yr58. Genotyping with Yr46-linked markers indicated the presence of Yr46 in W195, which corresponded to QYr.sun-4DL. The RILs carrying Yr58 and Yr46 singly produced IT 23C and IT 3, respectively, and those carrying both genes produced IT ;1C indicating the enhancement of Yr58 expression by Yr46. The absence of Yr58-linked alleles of markers sun533 and sun476 in 74 of the 76 wheat cultivars demonstrated their usefulness for marker-assisted selection.

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