Further investigation on A2 mating type of Phytophthora infestans in China

After the first report on occurrence of A2 mating type in China, further investigation had been conducted by authors about occurrence and distribution of A2 mating type of Phytohpthora infestans in main potato production provinces. Mating types of one hundred and forty two isolates were determined on white kidney bean media. These isolates were collected from Hebei, Inner Mongolia, Shangxi,Yunnan, Sichuan, Chongqing and Beijing during 1995—1998. The result showed that 28 isolates of A2 mating type covered 19 7% of all and great difference existed between the occurrence frequency of A2 mating type from different provinces. Especially, the rates of A2 mating type from Hebei, Shangxi and Inner Mongolia were much higher than those from Yunnan, Sichuan and Chongqing, and two self fertile isolates were found, covering 1 4% of all.