Yr58: A New Stripe Rust Resistance Gene and Its Interaction with Yr46 for Enhanced Resistance.

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.