Spatial genetic diversity and interregional spread of Puccinia striiformis f. sp. tritici in Northwest China Ninghai Lu & Jianfeng Wang & Xianming Chen & Gangming Zhan & Changqing Chen & Lili Huang & Zhensheng Kang Accepted: 21 July 2011 /Published online: 3 August 2011 # KNPV 2011 Abstract In China, wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most destructive diseases of wheat. The Longnan and Linxia regions in Gansu Province and Qinghai Province are the major over-summering regions for the pathogen and key epidemiological zones in Northwest China. Population genetic diversity and interregional long- distance spread of the wheat stripe rust pathogen in Northwest China were studied using SSR markers. The genetic diversity in the Longnan population was much higher than those in the Linxia and Qinghai popula- tions. Therefore, the molecular data confirmed that the Longnan region is a center of genetic diversity for P. striiformis f. sp. tritici in Northwest China. The low genetic differentiation (Gst =0.15) and the extensive gene flow (Nm=1.37) were found among the three regions in Northwest China. The most important conclusion of this study is that the stripe rust inoculum in Qinghai can come from both Longnan and Linxia, but mainly from Longnan directly in the spring. Keywords Gene flow . Genetic differentiation . Puccinia striiformis f. sp. tritici . Spread of pathogen . Stripe rust . Triticum aestivum Introduction Stripe rust of wheat, caused by Puccinia striiformis Westend. f. sp. tritici Eriks., is one of the most damaging diseases of wheat in many areas around the world (Stubbs 1985; Chen 2005). In terms of the area that can be affected by the disease, China is the largest epidemic region for stripe rust of wheat in the world (Wan et al. 2007). The epidemics of 1950, 1964, 1990 and 2002 caused yield losses up to 6.0, 3.0, 1.8 and 1.3 million metric tons, respectively (Wan et al. 2004, 2007). Northwest China, including Gansu and Qinghai provinces, is one of the largest and the most important over-summering areas for the wheat stripe rust pathogen in China. The region provides inoculum to the major wheat-growing regions to the east. Almost all Chinese races of P. striiformis f. sp. tritici were first detected in the Longnan region of Gansu (Li and Zeng 2000 ). In the Longnan region (about 42,892 km 2 ), both winter and spring wheats are grown in valleys and mountains ranging from 1,000 to 2,000 m above sea level (a.s.l.). Winter wheat is Eur J Plant Pathol (2011) 131:685–693 DOI 10.1007/s10658-011-9842-y N. Lu : J. Wang : G. Zhan : C. Chen : L. Huang : Z. Kang (*) State Key Laboratory of Crop Stress Biology for Aried Areas and College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, People’ s Republic of China e-mail: kangzs@nwsuaf.edu.cn X. Chen USDA-ARS and Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430, USA N. Lu Henan Institute of Science and Technology, Xinxiang, Henan 453003, People’ s Republic of China