Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2007
Publication Date: 9/1/2007
Citation: Bonman, J.M., Bockelman, H.E., Jin, Y., Hijmans, R.J., Gironella, A. 2007. Geographic Distribution of Stem Rust Resistance in Wheat Landraces. Crop Science. 47:1955-1963. Interpretive Summary: Stem rust disease is a threat to wheat production worldwide. Many US wheat cultivars are vulnerable to new races of the stem rust pathogen that have recently appeared in East Africa. Since the pathogen is airborne, it could spread to other areas of the globe. As part of an international effort to reduce the threat of the new races, the National Small Grains Collection (NGCG) is screening accessions against the new races in Kenya. To help choose which accessions to screen first, we analyzed the stem rust resistance data available in the USDA’s Germplasm Resources Information Network and identified the geographic origins of resistant accessions. We also developed a statistical model to help choose accessions for further testing. Cooperating scientists in this study included Dr. Yue Jin, USDA Cereal Disease Laboratory in St. Paul MN; Dr. Ann Gironella, Idaho State University in Pocatello, ID; and Dr. Robert Hijmans, the International Rice Research Institute, Philippines. Information from our study will help us better target NSGC accessions for stem rust testing and will eventually help wheat breeders develop new resistant cultivars for US wheat growers.
Technical Abstract: Wheat stem rust disease, caused by Puccinia graminis (Pers.) f. sp. tritici, is of renewed concern due to the emergence of new virulent races in East Africa. Landrace accessions of common wheat, Triticum aestivum L. subsp. aestivum, and durum wheat, T. turgidum L. subsp. durum, from the National Small Grains Collection (NSGC) could be sources of new stem rust resistance genes. In an effort to better target the screening of NSGC landrace accessions against the new races, data from the NSGC was analyzed for the geographic distribution of resistance. Using screening data from 5700 landrace accessions of common wheat, centers of concentration for stem rust resistance were found originating from Ethiopia, Chile, Turkey, Bosnia and Herzegovina and adjacent areas of the Former Yugoslavia. Resistance to multiple races at the seedling stage was most frequent in accessions from Ethiopia. Resistance in durum wheat was more frequent than resistance in common wheat based on data from 2719 landrace accessions. Centers of concentration for resistant durum landraces were similar to those for common landraces. A logistic regression model was generated using information on the geographic origin of 3607 common wheat accessions and NSGC descriptor data for 11 other traits. Based on this model and on the identification of centers of concentration for resistance, accessions will be prioritized for future screening against the new stem rust race.