Genetic characterization and confirmation of stem rust resistance (Sr) genes in Rusty‐derived durum monogenic lines

Improved genetic stocks carrying stem rust resistance ( Sr ) genes are important tools for combating stem rust (caused by Puccinia graminis Pers. f. sp. tritici Eriks and E. Henn) in durum wheat ( Triticum turgidum L. subsp. durum (Desf.) Husn). Tetraploid wheat lines Vernal, Khapli, CItr8155, and ST464 were important sources of Sr genes in durum cultivars in the mid‐20th century. Six Sr genes derived from these four lines were transferred to a near‐isogenic Rusty background. Our objective was to use race specificity tests, gene mapping, haplotyping, and sequencing to postulate and validate the genes in each line. Based on race specificity testing and haplotyping with IWB10588, we concluded that both Rusty‐8155B1 and Rusty‐ST464A1 carried Sr8155B1 . Gene sequencing was used to identify Sr9e haplotypes, and we determined that Rusty‐ST464A2 and Rusty‐VnB1 carried Sr9e_h1 and Sr9e_h2 , respectively. Gene mapping located the Sr gene in Rusty‐KLA to the distal region of 4AL, and we concluded Rusty‐KLA carries Sr7a . Gene mapping located the gene in Rusty‐KLD to chromosome 1B. Based on this location and race specificity testing, we concluded that the gene in Rusty‐KLD was Sr14 . Race specificity testing where the five identified Sr genes/alleles are incorporated into monogenic Rusty backgrounds will be useful as phenotyping checks. Because it carries adult plant resistance to TTKSK, Rusty‐KLD carrying Sr14 may be useful in breeding, but, the other genes are already widely present in durum, and their monogenic lines may have limited breeding value. Markers linked to Sr14 will be useful in subsequent studies including gene sequencing.