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Regional differences in genetic structure of Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen, in the U.S. revealed by SSR makers
A. WAN (1), M. Wang (1), X. Chen (2). (1) Washington State University, Pullman, WA, U.S.A.; (2) USDA ARS, Pullman, WA, U.S.A.

Understanding the population structure and genetic diversity in the <i>Puccinia striiformis</i> f. sp. <i>tritici</i> (<i>Pst</i>) population is important for developing large-scale stripe rust management strategies. A total of 322 isolates collected from various epidemiological regions throughout the U.S. in 2010 were characterized using 17 co-dominant simple sequence repeat (SSR) markers. The population in the western U.S. (regions 1- 6) has higher genetic differentiation (<i>FST</i> = 0.17) than the population in the eastern U.S. (regions 7-12) (<i>FST</i> = 0.04). The number of effective migrants, <i>Nm</i>, was 1.3 and 6.0 in the western regions and the eastern regions, respectively. The data suggest that the population in the west is more diverse than the population in the east, or the population in the east has more frequent inoculum exchange among subpopulations than the population in the west. Analysis of Nei’s genetic distances indicated that the subpopulations of regions 1, 2, 3, 4, and 6 were more related to each other, those of regions 7, 8, 9, 10, 11 and 12 formed another group, while the subpopulation of region 5 (northwestern Washington) was distinct from the other two groups. The results could be attributed to the differences in resistance genes, geographic landscapes, and climatic conditions. The information should be useful for deploying different stripe rust resistance genes in different regions.

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