Genetic Analysis Reveals Relationships Among Populations of f. sp. from the Longnan, Longdong, and Central Shaanxi Regions of China.

Wheat stripe rust, caused by f. sp. , is one of the most important diseases of wheat worldwide. In China, Longnan (LN) and Longdong (LD) in the south and east of Gansu province, respectively, are important f. sp. oversummering areas and are a source of f. sp. inoculum for the major wheat-growing regions in eastern China. Central Shaanxi (CS) is a wheat-growing region that acts as an important bridge zone for stripe rust epidemic development between LN and LD in the west and the Huanghuai wheat-growing region in the east, and thus, it plays an essential role in f. sp. epidemics in China. To study the relationships among f. sp. populations in the three regions (LN, LD, and CS), we sampled 284 isolates from different geographic locations. Based on 10 simple sequence repeat markers, the results demonstrated high genetic diversity in all three regions, although diversity did vary among regions, with LN > LD > CS. Genetic differentiation was lower, with more extensive gene flow between LD and CS. f. sp. populations in the CS region were genetically closer to those from LD than those from LN, which may be a result of geographical proximity and topography. A positive and significant correlation existed between linearized fixation index () and the log of geographical distances among all subpopulations. Linkage disequilibrium analysis showed that subpopulations of f. sp. from Qinzhou, Qincheng, Beidao, and Maiji from LN and Qianyang and Longxian from CS were in equilibrium ( > 0.05), suggesting that somatic hybridization and/or sexual reproduction may exist in these subpopulations.