Temperature-sensitive wheat stem rust resistance gene Sr15 is effective against Puccinia graminis f. sp. tritici race TTKSK

Authors: GAO, LIANGLIANG - University Of Minnesota; Babiker, Ebrahiem; NAVA, ITAMAR - University Of Minnesota; NIRMALA, JAYAVEERAMUTHU - University Of Minnesota; BEDO, ZOLTAN - Hungarian Academy Of Sciences; LANG, LASZLO - Hungarian Academy Of Sciences; Chao, Shiaoman; Gale, Sam; Jin, Yue; ANDERSON,, JAMES - University Of Minnesota; BANSAL, URMIL - University Of Sydney; PARK, ROBERT - University Of Sydney; Rouse, Matthew; Bonman, John; BARIANA, HARBANS - University Of Sydney

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2018
Publication Date: 8/13/2018
Citation: Gao, L., Babiker, E.M., Nava, I.C., Nirmala, J., Bedo, Z., Lang, L., Chao, S., Gale, S.W., Jin, Y., Anderson, J.A., Bansal, U., Park, R.F., Rouse, M.N., Bonman, J.M., Bariana, H. 2018. Temperature-sensitive wheat stem rust resistance gene Sr15 is effective against Puccinia graminis f. sp. tritici race TTKSK. Plant Pathology. http://doi.org/10.1111/ppa.12928.
DOI: https://doi.org/10.1111/ppa.12928

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 discovered that wheat stem rust resistance gene Sr15 confers resistance to Ug99 at low temperatures. We detected the presence of Sr15 in two wheat lines that possessed resistance to Ug99: MV Zelma and PI 374670. We validated the predictive ability of three molecular markers linked to Sr15. Finally, we derived germplasm with both Sr15 and Ug99-resistant Sr22 combined on the same chromosome arm. The discovery of Sr15 as effective to Ug99 will facilitate the improvement of Ug99 resistance in United States wheat varieties. Ug99 resistant wheat varieties would protect United States wheat production from yield loss if a Ug99 epidemic were to occur in the United States.

Technical Abstract: The wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt), race TTKSK poses a serious threat to world wheat production. Knowing the effectiveness of wheat stem rust resistance (Sr) genes against Pgt race TTKSK is fundamental for mitigation of this threat through genetic resistance. Sr15 was previously identified as being ineffective against Pgt race TTKSK. Here we present disease phenotyping evidence and molecular marker assay results to support the conclusion that Sr15 is effective against Pgt race TTKSK under low temperatures (15-18 C). Among sixty-one lines tested, 31 accessions with Sr15 displayed resistance phenotypes against race TTKSK. The resistance effect was lost under high temperatures (22-25 C), consistent with previous reports that the effect of Sr15 is temperature-sensitive. The identification of Sr15 as effective against Pgt race TTKSK under certain environmental conditions has important implications on R gene deployment. Markers STS638, wri4, and KASP_IWB30995 were found to be predictive for the presence of Sr15, suggesting the utility of these assays for marker-assisted selection of Sr15. We derived germplasm with Sr15 and Sr22, both effective to race TTKSK, in coupling on chromosome arm 7AL. Utilization of combinations of multiple R genes effective to race TTKSK may result in durable resistance.