Population Genetic Structure of Puccinia striiformis in Northwestern China.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most important fungal diseases of wheat in China. Xinjiang, Qinghai, and Gansu Provinces, located in the northwest of China, are the key regions for interregional epidemics of wheat stripe rust due to their geographic as well as crop-planting features, in relation to pathogen's life cycle, reproduction, and population genetics. To study the population genetic structures of the pathogen in these areas, 217 isolates of P. striiformis f. sp. tritici were collected from different geographic locations at various elevations in the three provinces. The amplified fragment length polymorphism (AFLP) genotypes and virulence phenotypes were analyzed for Xinjiang, Qinghai, and Gansu populations. Frequent genotypic exchanges between Xinjiang and Qinghai and between Qinghai and Gansu populations were detected, demonstrating that the populations of Xinjiang and Gansu may not be completely isolated. Genotypic diversity in Gansu Province was much higher than that in Xinjiang or Qinghai Province. The Xinjiang population was genetically closer to the Qinghai population than to the Gansu population. The race dynamic patterns in Qinghai were consistent with those in Gansu but the similar component pattern of the race dynamics in Xinjiang appeared late, following those in Gansu and other interior epidemic regions of China. No significant correlation between the AFLP genetic distance and the virulence distance in the Xinjiang, Qinghai, and Gansu populations was determined. A possible recombination signature of the pathogen population was detected in Gansu population and some subpopulations in Qinghai but not in Xinjiang population.