Rust Resistance in Wheat: Gene Discovery and Development of Molecular Markers Using Diverse Genomic Resources

This investigation covered characterization of genetically diverse sources of resistance, identification of molecular markers linked with rust resistance genes and their validation across diverse backgrounds. Genetic analysis of leaf rust resistance using durum-specific pathotypes of the leaf rust pathogen revealed the presence of a single gene in Aus26579 and Aus26582. The resistance gene was mapped on chromosome 6BS. Markers sunKASP_60 and sun684 showed close associations with LrAW2. Lr61 was also mapped on chromosome 6BS and haplotype analysis using linked markers suggested that LrAW2 is likely to be Lr61. Aus26582 carried an additional leaf rust resistance gene that was effective against six Australian Pt pathotypes and was mapped on chromosome 3BL and the underlying locus was temporarily named LrAW3. Marker sun786 mapped 1.8 cM distal to LrAW3. As no other seedling leaf rust resistance gene was previously mapped on chromosome 3BL, LrAW3 was formally named Lr79. Markers sun711, sun712, sun725, sunKASP_109 and sun KASP_112 from chromosome 5AL co-segregated with Yr34. Yr48, also located on chromosome 5AL, was proved to be identical to Yr34 on the basis of allelism test, sequence information and haplotype analysis. Various genomic resources were utilized to identify a close genetic association between the marker sun180 and linked rust resistance genes Yr47 and Lr52 in a fine mapping study. The loci order of sun180-0.4 cM-Lr52-0.2 cM-Yr47 was deduced. Markers linked with LrAW2/Lr61 (sunKASP_60), Lr79 (sun786), Yr34/Yr48 (sun712) and linked resistance genes Yr47 and Lr52 (sun180) did not amplify resistance-linked alleles in any of the cultivars lacking these genes and thus demonstrated their robustness in marker-assisted pyramiding with other marker-tagged rust resistance genes to produce triple rust resistant cultivars