Genetic maps of stem rust resistance gene Sr35 in diploid and hexaploid wheat

Authors: ZHANG, W - University Of California; OLSON, E - Kansas State University; SAINTENAC, CYRILLE - Kansas State University; ROUSE, M - University Of Minnesota; ABATE, Z - University Of California; Jin, Yue; AKHUNOV, EDUARD - Kansas State University; PUMPHREY, M - Washington State University; DUBCOVSKY, J - University Of California

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2010
Publication Date: 11/1/2010
Citation: Zhang, W., Olson, E., Saintenac, C., Rouse, M., Abate, Z., Jin, Y., Akhunov, E., Pumphrey, M., Dubcovsky, J. 2010. Genetic maps of stem rust resistance gene Sr35 in diploid and hexaploid wheat. Crop Science. 50(6):2464-2474.

Interpretive Summary: Wheat stem rust is an important disease and the control of stem rust in wheat relies on the use of genetic resistance. A new race designated TTKSK (also known as Ug99) has recently spread through East Africa, Yemen and on to Iran. TTKSK and its variants (TTKST and TTTSK) are virulent to most of the stem rust resistance genes currently deployed in wheat cultivars worldwide. Therefore, identification, mapping and deployment of effective resistance genes are critical components of integrated global efforts to mitigate this threat. Resistance gene Sr35 is known to be effective against TTKSK races and another broadly virulent race from Yemen, TRTTF. Three genetic maps of resistance gene Sr35 are presented in diploid (Triticum monococcum) and hexaploid wheat (Triticum aestivum). Srs35 was mapped within a 5.1 cM interval in diploid wheat on the long arm of chromosome 3Am between EST derived markers BF483299 and CJ656351. This 5.1 cM interval corresponds to a 174 kb region in Brachypodium that includes 16 annotated genes. The Sr35 map location was confirmed in two backcross-derived hexaploid populations segregating for Sr35. Recombination between diploid and hexaploid chromosomes was 10-fold lower than between homologous chromosomes, but was sufficient to reduce the diploid segment previously introgressed into hexaploid wheat. These maps provide markers closely linked to Sr35 that will be useful to accelerate its deployment and pyramiding of Sr35 with other resistance genes.

Technical Abstract: Puccinia graminis f. sp. tritici is the causal agent of stem rust of wheat. A new race designated TTKSK (also known as Ug99) has recently spread through East Africa, Yemen and on to Iran. TTKSK and its variants (TTKST and TTTSK) are virulent to most of the stem rust resistance genes currently deployed in wheat cultivars worldwide. Therefore, identification, mapping and deployment of effective resistance genes are critical components of integrated global efforts to mitigate this threat. Three genetic maps of resistance gene Sr35 are presented in diploid (Triticum monococcum) and hexaploid wheat (Triticum aestivum). Multi-pathotype seedling tests demonstrated that Sr35 is effective against the three TTKS variants and another broadly virulent race from Yemen, TRTTF. They also indicated that one of parents of the diploid mapping population carries Sr21 and the other one Sr21 and Sr35. The Sr35 resistance to TRTTF and RKQQC races was mapped within a 5.1 cM interval in diploid wheat on the long arm of chromosome 3Am between EST derived markers BF483299 and CJ656351. This 5.1 cM interval corresponds to a 174 kb region in Brachypodium that includes 16 annotated genes. The Sr35 map location was confirmed in two backcross-derived hexaploid populations segregating for Sr35. Recombination between diploid and hexaploid chromosomes was 10-fold lower than between homologous chromosomes, but was sufficient to reduce the diploid segment previously introgressed into hexaploid wheat. These maps provide markers closely linked to Sr35 that will be useful to accelerate its deployment and pyramiding of Sr35 with other resistance genes.