Characterization of an Incomplete Leaf Rust Resistance Gene on Chromosome 1RS and Development of KASP Markers for in Wheat.

Leaf rust, caused by , is one of the most common wheat () diseases in the Great Plains of the United States. A population of recombinant inbred lines from CI 17884 × 'Bainong 418' was evaluated for responses to leaf rust race - and genotyped using single nucleotide polymorphism (SNP) markers. Quantitative trait locus analysis identified a minor gene for resistance to leaf rust, designated .-, on the 1BL.1RS translocation segment in 'Bainong 418', and another leaf rust resistance gene, , on chromosome 7A of CI 17884. , originally identified in CI 17884 and located in a wheat-. 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 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 Megabases, accounting for ∼23% of the 7A chromosome. Two SNPs on 7S#1S and four SNPs on the 1RS chromosome arm were converted to Kompetitive allele-specific PCR (KASP) markers, which were subsequently validated in a panel of cultivars and elite breeding lines released within the last decade. 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 and .- into locally adapted wheat cultivars and breeding lines.