Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 2007
Publication Date: September 1, 2007
Repository URL: http://hdl.handle.net/10113/13948
Citation: Kolmer, J.A., Ordonez, M.E. 2007. Genetic differentiation of Puccinia triticina populations in Central Asia and the Caucasus. Phytopathology. 97:1141-1149. Interpretive Summary: Leaf rust is a disease caused by the fungus Puccinia triticina. This disease is common on wheat in the U.S. and also world-wide. The fungus is highly variable for its ability to attack wheat plants that have different genes that give resistance to the fungus, and is also highly variable for variation that is detected using molecular biology techniques. In this study collections of the leaf rust fungus from the Central Asian countries of Kazakhstan, Uzbekistan, Tajikistan, Kyrgyzstan, and the Caucasus countries of Azerbaijan, Georgia, and Armenia, were compared with collections of leaf rust from the U.S. for virulence to different resistance genes in wheat and for molecular variation. The populations from the Caucasus, Uzbekistan, Tajikistan and Kyrgyzstan were highly similar for virulence and molecular variation, while the populations from Kazakhstan were significantly different from the other populations in Central Asia and the Caucasus. All populations from Central Asia and the Caucasus were highly different for both virulence and molecular variation compared to the leaf rust population in the U.S. The results indicated that populations of leaf rust from Central Asia and the Caucasus region do not migrate into the U.S. Wheat cultivars developed for the U.S. need to be resistant only to the leaf rust populations currently found in the U.S.
Technical Abstract: Isolates of Puccinia triticina collected from common wheat in the Central Asia countries of Kazakhstan, Uzbekistan, Tajikistan, Kyrgyzstan, and the Caucasus countries of Azerbaijan, Georgia, and Armenia were tested for virulence to 20 isolines of Thatcher wheat with different leaf rust resistance genes, and for molecular genotype at 23 simple sequence repeat (SSR) loci. After clone correction within each country, 99 isolates were analyzed for measures of population diversity, variation at single SSR loci, and for genetic differentiation of virulence phenotypes and SSR genotypes. Isolates from Central Asia and the Caucasus were also compared with 16 P. triticina isolates collected from common wheat in North America that were representative of the virulence and molecular variation in this region, and two isolates collected from durum wheat in France and the U.S. Populations from the Caucasus, Uzbekistan, Tajikistan and Kyrgyzstan, were not significantly (p > 0.05) differentiated for SSR variation with Fst and Rst statistics. Populations from the Caucasus, Uzbekistan, Tajikistan and Kyrgyzstan, were significantly (p < 0.05) differentiated from the populations in South and North Kazakhstan for SSR variation. All populations from Central Asia and the Caucasus were significantly differentiated from the North American and durum isolates for SSR variation and virulence phenotypes. There was a high correlation between virulence phenotype and SSR genotype at the population level and among individual isolates. Geographic barriers and differences in wheat cultivars may account for the differentiation of P. triticina populations in Central Asia and the Caucasus.