Location: Cereal Crops ResearchTitle: Development and characterization of wheat lines carrying stem rust resistance gene Sr43 derived from Thinopyrum ponticum) Author
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/13/2014
Publication Date: 2/7/2014
Publication URL: handle.nal.usda.gov/10113/58663
Citation: Niu, Z., Klindworth, D.L., Yu, G., Friesen, T.L., Chao, S., Jin, Y., Cai, X., Ohm, J.-B., Rasmussen, J.B., Xu, S.S. 2014. Development and characterization of wheat lines carrying stem rust resistance gene Sr43 derived from Thinopyrum ponticum. Theoretical and Applied Genetics. 127:969-980. Interpretive Summary: Stem rust Ug99 races are considered a major threat to world wheat production because most of the stem rust resistance genes in modern wheat cultivars are ineffective against Ug99 races. Stem rust resistance gene Sr43, originally transferred into wheat from tall wheatgrass, is an effective gene against stem rust Ug99 races. However, this gene has not been used in wheat breeding because it is located on a large wheatgrass chromosome segment, which also harbors genes for undesirable traits, in the original wheat-wheatgrass chromosome translocation (interchanged) line KS10-2. The objective of this study was to eliminate excessive wheatgrass chromatin surrounding Sr43 to thereby make the gene usable in wheat breeding. By using chromosome engineering in conjunction with molecular marker analysis, we developed two new wheat lines, which were designated as RWG33 and RWG34, respectively, carrying Sr43 on shortened wheatgrass chromosome segments. Compared to the original line KS10-2 in which the large wheatgrass chromosome segment was calculated as 83.3% of the interchanged chromosome, RWG33 and RWG34 were calculated as 17.5% and 13.7% of the chromosomes, respectively. Therefore, about 79.0% and 83.6% of wheatgrass chromatin surrounding Sr43 were removed in the two new wheat lines. In addition, we developed two molecular markers linked to Sr43 based on the physical location of Sr43 in the wheat genome. The two new wheat lines and molecular markers developed in this study provide wheat breeding resources for controlling Ug99 and other stem rust races.
Technical Abstract: Stem rust resistance gene Sr43, transferred into common wheat (Triticum aestivum) from tall wheatgrass (Thinopyrum ponticum), is an effective gene against stem rust Ug99 races. However, this gene has not been used in wheat breeding because it is located on a large Th. ponticum 7el2 chromosome segment, which also harbors genes for undesirable traits. The objective of this study was to eliminate excessive Th. ponticum chromatin surrounding Sr43 in order to make it usable in wheat breeding. The two original translocation lines KS10-2 and KS24-1 carrying Sr43 were first analyzed using simple sequence repeat (SSR) markers and florescent genomic in situ hybridization. Six SSR markers previously mapped to the long arm of wheat chromosome 7D were associated with the Th. ponticum chromatin in KS10-2 and KS24-1. The results confirmed that KS24-1 is a 7DS.7el2L Robertsonian translocation as previously reported. However, KS10-2, which was previously designated as a 7el2S.7el2L-7DL translocation, was identified as a 7DS-7el2S.7el2L translocation. To reduce the Th. ponticum chromatin carrying Sr43, a BC2F1 population (Chinese Spring//Chinese Spring ph1bph1b*2/KS10-2) containing ph1b-induced homoeologous recombinants was developed, tested with stem rust, and genotyped with the six SSR markers identified above. Two new wheat lines (RWG33 and RWG34) carrying Sr43 on shortened alien chromosome segments (about 17.5% and 13.7% of the translocation chromosomes, respectively) were obtained, and two molecular markers linked to Sr43 in these lines were identified. The new wheat lines with Sr43 and the closely-linked markers provide new resources for improving resistance to Ug99 and other races of stem rust in wheat.