Genetic diversity revealed by RAPD analysis among isolates of Phytophthora infestans from different locations in China.

Random amplified polymorphic DNA(RAPD) analysis was used to detect the genetic variation in populations of Phytophthora infestans from major potato production regions in China.Among 180 primers screened,ten that generated consistent polymorphic bands with DNA of 5 tested isolates were applied to amplify the genomic DNA of 82 isolates collected in China during the period from 1997 to 2001 and three isolates from Japan.In total,79 RAPD markers were obtained and 75 of them,occupying 95%,showed polymorphism.The genetic distances between isolates were calculated from the data set of RAPD analysis using UPGMA(Unweighted Pair-Group Method with Arithmetic Average) cluster analysis.The maximum linkage distance among these isolates was 0.5,which indicated the existence of a considerable level of diversity in P.infestans population in China.At linkage distance of 0.30,85 isolates were divided into 10 RAPD groups.A larger variation was detected among A1 isolates from different locations than that between A1 and A2 populations.There was no correlation between RAPD group and the geographic origin,or between RAPD groups and mating type of the isolates.The response of isolates to the chemical metalaxyl did not correlate with RAPD group,either.Results of this study suggested that some isolates from Yunnan,Sichuan and Chongqing,the southwestern regions of China were closely related to some isolates from Gansu,Inner Mongolia,Heilongjiang and Jilin,the north of China.Migration of the late blight fungus along with potato tubes might be a cause of this situation.