Fifty-nine isolates of Magnaporthe oryzae that collected in Hunan province were divided into 20 races based on the reactions to 10 monogenic differential cultivars from Japanese, IRRI and Chinese differential cultivars. Dominant races in the fungal population were H531.1, H511.1 and H501.1, which were virulent to rice cultivar with blast resistance genes Pi-CO39, Pita, Pi3, Pi12 and Pia. The composition of races and dominant races of blast pathogen in different rice cropping regions of Hunan were different....