|HIEBERT, COLIN - Agriculture And Agri-Food Canada|
|KASSA, MULUALEM - Agriculture And Agri-Food Canada|
|MCCARTNEY, CURT - Agriculture And Agri-Food Canada|
|YOU, FRANK - Agriculture And Agri-Food Canada|
|Rouse, Matthew - Matt|
|FOBERT, PIERRE - National Research Council - Canada|
|FETCH, TOM - Agriculture And Agri-Food Canada|
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2016
Publication Date: 8/9/2016
Citation: Hiebert, C.W., Kassa, M.T., McCartney, C.A., You, F.M., Rouse, M.N., Fobert, P., Fetch, T.G. 2016. Genetics and Mapping of Seedling Resistance to Ug99 Stem Rust in the Winter Wheat Cultivar Triumph 64 and Differentiation of SrTmp, SrCad, and Sr42. Theoretical and Applied Genetics. 129(11):2171-2177.
Interpretive Summary: Wheat stem rust is a devastating fungal disease of wheat. 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. Triumph 64 is a winter wheat cultivar that carries a gene, SrTmp, which confers resistance to Ug99. Genetic mapping with molecuar markers placed SrTmp on chromosome arm 6DS in a region similar to two other Ug99-effective resistance genes: SrCad and Sr42. Multi-race stem rust testing with lines from populations segregating for SrTmp, SrCad, and Sr42 demonstrated that these three genes have different spectra of resistance. The markers closely linked to SrTmp are suitable for marker-assisted selection in breeding and germplasm development programs. Markers linked to Ug99-effective resistance genes can be used by wheat breeding programs to select for Ug99 resistance to develop resistant wheat cultivars.
Technical Abstract: Stem rust, caused by the fungus Puccinia graminis f. sp. tritici Eriks. & E. Henn. (Pgt), is an important disease of wheat that can be controlled by deploying effective stem rust resistance (Sr) genes. The emergence of virulent Pgt races in Africa, namely Ug99 and its variants, has stimulated the search for new Sr genes and genetic characterization of known sources of resistance. Triumph 64 is a winter wheat cultivar that carries a gene, SrTmp, which confers resistance to Ug99. The goals of this study were to genetically map SrTmp and examine its relationship with other Sr genes occupying a similar chromosome location. A doubled haploid (DH) population from the cross LMPG-6S/Triumph 64 was inoculated with Ug99 (race TTKSK) at the seedling stage. A single gene conditioning resistance to Ug99 segregated in the population. Genetic mapping with SSR markers placed SrTmp on chromosome arm 6DS in a region similar to SrCad and Sr42. SNP markers developed for SrCad were used to further map SrTmp and were also added to a previously constructed genetic map of Sr42 using a DH population from the cross LMPG-6S/Norin 40. Three SNP markers that co-segregated with SrTmp also co-segregated with SrCad and Sr42. The SNP markers showed no difference in the map locations of SrTmp, SrCad, or Sr42. Multi-race testing with DH lines from the Triumph 64 and Norin 40 populations and a recombinant inbred-line population from the cross LMPG-6S/AC Cadillac showed that SrTmp, SrCad, and Sr42 have different spectra of resistance. The markers closely linked to SrTmp are suitable for marker-assisted selection in breeding and germplasm development programs.