Abstract:In order to characterize population structure and its variation of Phytophthora infestans, the characteristics of mating type, metalaxyl sensitivity and physiological races of Phytophthora infestans isolates collected from tomato and potato in 11 different counties of Fujian Province during 2001-2007 were tested. Among 187 isolates tested, 181 isolates belonged to A1 mating type, 1 was A2 mating type, 1 was A1,A2 mating type, 1 was selffertil mating type, 3 isolates were unknown mating type. Among 187 isolates tested, the ratios of resistant, moderately resistant and sensitive isolates were 97.3%, 2.1% and 0.5%. Physiological races of 51 isolates of Phytophthora infestans were identified. The results showed all known eleven resistance genes, with different frequency from 3.3% to 100%, could be overcame. Thirty different physiological races were detected in the 51 isolates, and race 3.7 was the dominant race in Fujian population with the frequency of 13.7%, followed by 3.4.7 with frequency of 9.8%.