Characterization of an incomplete leaf rust resistance gene on chromosome 1RS and development of KASP markers for Lr47 in wheat

Leaf rust, caused by Puccininia triticina (Pt), is one of the most common wheat diseases in the Great Plains of the USA. A population of recombinant inbred lines (RILs) from CI 17884 x Bainong 418 was evaluated for responses to leaf rust race Pt52-2 and genotyped using single nucleotide polymorphism (SNP) markers. Quantitative trait locus (QTL) analysis identified a minor gene for resistance to leaf rust, designated QLr.stars-1RS, on the 1BL.1RS translocation segment in Bainong 418, and another leaf rust resistance gene, Lr47, on chromosome 7A of CI 17884. Lr47, originally identified in CI 17884 and located in a wheat-T. speltoides translocation segment 7S#1S, remains one of only a few race-specific resistance genes still effective in the Great Plains. A set of 7A-specific simple sequence repeat (SSR) markers were developed and used to genotype CI 17884 and a pair of near-isogenic lines differing in the presence or absence of 7S#1S, PI 603918 and Pavon F76. Haplotype analysis indicated that the estimated length of 7S#1S was 157.23 to 174.42 Mb, accounting for about 23% of the 7A chromosome. Two SNPs on 7S#1S and 4 SNPs on the 1RS chromosome arm were converted to KASP markers, which were subsequently validated in a panel of cultivars and recently released elite breeding lines. Of these, one and two KASP markers are specific to the 1RS chromosome arm and 7S#1S, respectively, indicating that they can facilitate the introgression of Lr47 and QLr.stars-1BS into locally adapted wheat cultivars and breeding lines.