Genetic mapping of resistance to Puccinia graminis race TTKSK in Triumph 64
The stem rust resistance gene SrTmp carried by Triumph 64 confers resistance to Pgt race TTKSK and other members of the Ug99 race group. While some previous studies have mapped resistance postulated to be SrTmp, none used Triumph 64 as a parent. The purpose of this study was to genetically map SrTmp with DNA markers using a DH population from LMPG/Triumph 64 and compare the map position of SrTmp to previously mapped Sr genes. The DH population was tested with Pgt race TTKSK at the seedling stage. A single gene conditioned resistance to TTKSK (n = 144; χ21:1 = 0.44, p = 0.50). SrTmp was mapped to the distal region of chromosome 6DS with SSR markers. The map location of SrTmp was similar to SrCad and Sr42, which likely represent the same gene. In a concurrent study SNP markers were developed to fine-map SrCad. SNP markers were identified and/or developed using a public SNP database (http://www.cerealsdb.uk.net) and sequence information from an Aegilops tauschii genome sequencing project. Further SNP markers were developed by using resistance gene analogs from chromosome 6D to BLAST exome capture sequences from a set of Canadian wheat cultivars followed by searching for unique SNPs found in SrCad carriers. These SNP markers were added to the map of SrTmp. The map positions of SrTmp and SrCad/Sr42 are very similar. While preliminary data show functional differences between SrTmp and SrCad/Sr42, further analysis is needed to determine whether these genes are allelic or closely linked.