Genetic evidence of local adaption and long distance migration in Blumeria graminis f. sp hordei populations from China

Barley powdery mildew, caused by the obligate biotrophic fungus Blumeria graminis f. sp. hordei (Bgh), is one of the most devastating diseases in the winter barley-growing regions of China. Genetic diversity of this fungus was assessed by analyzing 75 Bgh isolates belonging to 12 pathotypes using seven primer combinations of amplified fragment length polymorphism (AFLP) markers. The six sampling locations were 300 km to 2200 km apart. The highest gene diversity indices were observed within Baoshan (H = 0.21) in Yunnan Province and Putian (H = 0.21) in Fujian Province. Higher gene flow values were found between Baoshan and other populations (Nm = 2.010-5.765) except Yancheng in Jiangsu Province and Jiaxing in Zhejiang Province and between Putian and other populations (Nm = 2.110-5.423) except Jiaxing though a long geographical distance among some locations. Between each Bgh population pair, the genetic groups and origins of the Bgh isolates were closely correlated, and the populations were significantly differentiated (P < 0.005 or P < 0.001). These results suggested that, in spite of local adaptation of Bgh populations to hosts, frequent long distance gene flow existed among these populations in China as shown in the previous study based on virulence assessment, and the centers of genetic diversity and primary inoculum origins of Bgh were probably located in those barley-growing areas in southwestern Yunnan Province and southeastern Fujian Province.