Closely Linked Markers for Stem Rust Resistance Gene Sr48 in Wheat.

The stem rust resistance gene Sr48 identified in winter wheat cultivar Arina imparts resistance against Ug99. Sr48 was located in the long arm of chromosome 2A and was loosely linked with marker fba00a8. The present study used an Arina/Cezanne F₆ recombinant inbred line (RIL) mapping population comprising of 178 lines to identify markers closely linked with Sr48. Various genomic resources were used to identify close marker-gene association and unfortunately none of the chromosome 2AL markers showed linkage with Sr48. Using the DArTseq markers, Sr48 was flanked by markers located in 2AL and 2DS in a Arina/Cezanne RIL population. STS/SSR markers were designed from both 2AL (3 markers) and 2DS (11 markers) DArTSeq linked markers. All three chromosome 2AL markers were monomorphic, whereas two 2DS (sun590 and sun592) markers were polymorphic. When genotyped on the RIL population, sun590 flanked Sr48 proximally at 2.1 cM and sun592 distally at 1.7cM. Of other markers that were previously mapped on chromosome 2DS, xib59 and xib58 showed polymorphism between parents and were mapped 4.1 cM and 11.9 cM distal to Sr48, respectively. Together, the genetic distance of sun590, sun592, xib59, and xib58 covered a total length of 19.9 cM on 2DS. Comparison of DArTseq markers indicated a translocation involving chromosomes 2AL and 2DS. The linked markers were validated for their specificity to Sr48 on a set of 84 Australian and 92 Nordic wheat genotypes.