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Phytopathology. 2015 Jul;105(7):872-84. doi: 10.1094/PHYTO-01-15-0030-FI. Epub 2015 Jun 29.

Emergence and Spread of New Races of Wheat Stem Rust Fungus: Continued Threat to Food Security and Prospects of Genetic Control.

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First, eleventh, and twelfth authors: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal, 6-641, 06600, Mexico, D.F.; second author: CIMMYT, Addis Ababa, Ethiopia; third, seventh, and ninth authors: United States Department of Agriculture-Agricultural Research Service, Cereal Disease Laboratory, University of Minnesota, St. Paul 55108; fourth and fifth authors: Commonwealth Scientific and Industrial Research Organisation (CSIRO) Plant Industry, Agriculture Flagship, GPO Box 1600, Canberra, ACT, 2601, Australia; sixth author: CIMMYT, ICRAF House, United Nations Avenue, Gigiri, Village Market-00621, Nairobi, Kenya; eighth author: University of the Free State, Bloemfontein 9300, South Africa; tenth author: Campo Experimental Valle de México INIFAP, Apdo. Postal 10, 56230, Chapingo, Edo de México, México; and thirteenth author: Department of Agroecology, Aarhus University, Forsøgsvej 1, DK-4200, Slagelse, Denmark.


Race Ug99 (TTKSK) of Puccinia graminis f. sp. tritici, detected in Uganda in 1998, has been recognized as a serious threat to food security because it possesses combined virulence to a large number of resistance genes found in current widely grown wheat (Triticum aestivum) varieties and germplasm, leading to its potential for rapid spread and evolution. Since its initial detection, variants of the Ug99 lineage of stem rust have been discovered in Eastern and Southern African countries, Yemen, Iran, and Egypt. To date, eight races belonging to the Ug99 lineage are known. Increased pathogen monitoring activities have led to the identification of other races in Africa and Asia with additional virulence to commercially important resistance genes. This has led to localized but severe stem rust epidemics becoming common once again in East Africa due to the breakdown of race-specific resistance gene SrTmp, which was deployed recently in the 'Digalu' and 'Robin' varieties in Ethiopia and Kenya, respectively. Enhanced research in the last decade under the umbrella of the Borlaug Global Rust Initiative has identified various race-specific resistance genes that can be utilized, preferably in combinations, to develop resistant varieties. Research and development of improved wheat germplasm with complex adult plant resistance (APR) based on multiple slow-rusting genes has also progressed. Once only the Sr2 gene was known to confer slow rusting APR; now, four more genes-Sr55, Sr56, Sr57, and Sr58-have been characterized and additional quantitative trait loci identified. Cloning of some rust resistance genes opens new perspectives on rust control in the future through the development of multiple resistance gene cassettes. However, at present, disease-surveillance-based chemical control, large-scale deployment of new varieties with multiple race-specific genes or adequate levels of APR, and reducing the cultivation of susceptible varieties in rust hot-spot areas remains the best stem rust management strategy.


black rust

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