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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #302280

Research Project: CEREAL RUST FUNGI: GENETICS, POPULATION BIOLOGY, AND HOST-PATHOGEN INTERACTIONS

Location: Cereal Disease Lab

Title: Characterization of Sr9h, a Ug99-resistant allele of wheat stem rust resistance gene Sr9, and coupling to Sr28 on chromosome arm 2BL

Author
item Rouse, Matthew - Matt
item Nirmala, Jayaveeramut
item Jin, Yue
item Chao, Shiaoman
item FETCH, THOMAS - Agriculture And Agri-Food Canada
item PRETORIUS, ZACHARIAS - University Of The Free State
item HIEBERT, COLIN - Agriculture And Agri-Food Canada

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2014
Publication Date: 6/10/2014
Citation: Rouse, M.N., Nirmala, J.H., Jin, Y., Chao, S., Fetch, T.G., Pretorius, Z., Hiebert, C. 2014. Characterization of Sr9h, a Ug99-resistant allele of wheat stem rust resistance gene Sr9, and coupling to Sr28 on chromosome arm 2BL. Journal of Theoretical and Applied Genetics. 127:1681-1688.

Interpretive Summary: Race Ug99 of the wheat stem rust pathogen threatens global wheat production due to its broad virulence on current wheat varieties. We determined that a previously mapped Ug99 resistance gene from wheat cultivar Webster is also present in the resistant cultivar Gabo 56 through genetic mapping and segregation of resistance. Further studies allowed us to name this resistance gene Sr9h: a Ug99-resistant allele of stem rust resistance gene Sr9. Webster and Gabo 56 were susceptible to a Ug99-related race from South Africa. This South African race possesses unique virulence to uncharacterized Ug99 resistance in the cultivar Matlabas. This result validated that resistance to Ug99 in Webster and Gabo 56 is conferred by the same gene, Sr9h. The emergence of pathogen virulence to several resistance genes that were effective to the original Ug99 suggests that resistance genes should be used in combinations in order to increase resistance durability. We derived a wheat line with both Sr9h and Ug99-effective gene Sr28 on the same chromosome arm for utilization. Linkage between Sr9h and Sr28 increases the recovery of this combination in wheat breeding for development of more resistant cultivars.

Technical Abstract: Race TTKSK (Ug99) of Puccinia graminis f. sp. tritici, the causal fungus of stem rust, threatens global wheat production because of its broad virulence to current wheat cultivars. A recently identified Ug99 resistance gene from cultivar Webster, temporarily designated as SrWeb, mapped near the stem rust resistance gene locus Sr9. We determined that SrWeb is also present in Ug99 resistant cultivar Gabo 56 by comparative mapping and an allelism test. Analysis of resistance in a population segregating for both Sr9e and SrWeb demonstrated that SrWeb is an allele at the Sr9 locus that we designated as Sr9h. Webster and Gabo 56 were susceptible to the Ug99-related race TTKSF+ from South Africa. Race TTSKF+ possesses unique virulence to uncharacterized Ug99 resistance in cultivar Matlabas. This result validated that resistance to Ug99 in Webster and Gabo 56 is conferred by the same gene: Sr9h. The emergence of pathogen virulence to several resistance genes that were effective to the original Ug99 race TTKSK suggests that resistance genes should be used in combinations in order to increase resistance durability. We derived a wheat line with both Sr9h and Sr28 on chromosome arm 2BL for utilization of both genes for Ug99 resistance in coupling. Linkage between Sr9h and Sr28 will increase the recovery of this resistance gene combination after chromosomal recombination in wheat breeding.