|BRIGGS, JORDAN - University Of Minnesota|
|CHEN, SHISHENG - University Of California|
|ZHANG, WENJUN - University Of California|
|NELSON, SARAH - University Of Minnesota|
|DUBCOVSKY, JORGE - University Of California|
|Rouse, Matthew - Matt|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2015
Publication Date: 4/6/2015
Citation: Briggs, J., Chen, S., Zhang, W., Nelson, S., Dubcovsky, J., Rouse, M.N. 2015. Mapping of SrTm4, a recessive stem rust resistance gene from diploid wheat effective to Ug99. Phytopathology. 105:1347-1354.
Interpretive Summary: Wheat stem rust is a fungal disease of wheat that decreases yield. A strain of the wheat stem rust fungus known as Ug99 emerged in Uganda in 1999 and threatens global wheat production because it is able to infect nearly all wheat varieties. We characterized a fourth stem rust resistance gene from a wheat relative species called Einkorn wheat, that provides resistance to Ug99 and all other tested races of the stem rust pathogen. We identified the location of this gene, that we call SrTm4, within a specific wheat chromosome arm. The molecular markers that we identified as linked to this gene can be used to aid introgression of SrTm4 into bread wheat to select for resistance to Ug99 and other races of the stem rust pathogen. The identification these molecular markers will facilitate the improvement of resistance of United States wheat cultivars to the dangerous Ug99. Ug99 resistant wheat cultivars will protect United States wheat production from yield loss if a Ug99 epidemic were to occur in the United States.
Technical Abstract: Race TTKSK (or Ug99) of Puccinia graminis f. sp. tritici (Pgt), the causal agent of wheat stem rust, is a serious threat to wheat production worldwide. The best approach to reduce this threat is to identify and deploy new stem rust resistance genes. Diploid wheat, Triticum monococcum (genome Am), has wild and cultivated forms, that have been utilized previously for the introgression of stem rust resistance genes Sr21, Sr22, and Sr35. Multi-pathotype seedling tests of biparental populations demonstrated that T. monococcum accession PI 306540 from Romania, contains a different recessive resistance gene effective to all Pgt races screened so far (including race TTKSK), which we will refer to as SrTm4 (fourth stem rust resistance gene characterized from T. monococcum). Using two mapping populations derived from crosses of PI 272557 × PI 306540 and G3116 × PI 306540, we mapped SrTm4 on chromosome arm 2AmL within a 2.1 cM interval flanked by sequence-tagged markers BQ461276 and DR732348, which corresponds to a 240-kb region in Brachypodium chromosome 5. The eight microsatellite and nine sequence-tagged markers linked to SrTm4 will facilitate the introgression of this resistance gene into hexaploid wheat and accelerate the deployment of SrTm4-mediated Ug99 resistance in common wheat breeding programs.