Abstract
Genetic variation of the fungal parasite Pythium porphyrae, causative organism of red rot disease of Porphyra, isolated from Asan, Mokpo, Pusan and Wando in Korea, and from Aichi, Fukuoka and Miyagi in Japan was investigated by random amplified polymorphic DNA (RAPD) cluster analysis. The total 67 RAPD markers were generated from 38 isolates by RAPD-polymerase chain reaction (PCR) using arbitrary primers consisting of 10 nucleotide sequences and 33 of them indicated polymorphisms. The dissimilarity coefficients calculated from the RAPD banding patterns ranged from 0.0010 to 0.6983. The dendrogram generated by the unweighted pair-group method using arithmetic averages showed that the 38 isolates were classified into three clusters (Groups 1, 2 and 3). Group 1 consisting of two isolates from Miyagi was separated from all other isolates by a genetic distance of 0.6983. Groups 2 and 3 containing the majority of the isolates were branchedon genetic distance of 0.3957. These two clusters subdivided into four and three subclusters, respectively, which were apparently associated with geographic origins of the isolates. Interestingly, the isolates from Asan of Korea were close to Japanese isolatesrather than Korean isolates on genetic diversity. In addition, thegenetic distances of intra-isolates from Japan were higher than those from Korea.
