Development of Robust Molecular Markers for Marker-Assisted Selection of Leaf Rust Resistance Gene Lr23 in Common and Durum Wheat Breeding Programs

Leaf rust, caused by Puccinia triticina (Pt), is one of the most important fungal diseases of wheat worldwide. The common wheat genotype BT-Schomburgk selection (BTSS) and the durum wheat cultivar Tamaroi carry Lr23, which is effective against predominant Pt pathotypes in Australia. BTSS and Tamaroi were crossed with the seedling susceptible genotypes W195 and Bansi, respectively, and recombinant inbred line (RIL) F-5:7 populations W195/BTSS (88 RILs) and Tamaroi/Bansi (85 RILs) were developed. These populations were screened against Pt pathotype 104-1,(2), 3,(6),(7), 11,13 at the seedling stage and monogenic segregation at the Lr23 locus was observed. A combination of DNA marker technologies and genomic resources were used to fine map the chromosome 2B region carrying Lr23 in both RIL populations to develop closely linked markers for its marker-assisted selection in common and durum wheat breeding. Three single-marker SNP assays (sunKASP_16, sunKASP_47, and sunKASP_48) were developed and validated for selecting Lr23 in common wheat and one single-marker SNP assay (KASP_69462) was validated for durum wheat. None of the SNP markers worked across both common wheat and durum wheat backgrounds. The SSR marker sun471 showed close linkage with Lr23 across both ploidy levels. Overall, robust markers linked with Lr23 for use across different socio-economic geographic regions of the world were developed.