Comparison of the morphological and physiological features of the red rot disease fungus Pythium sp isolated from Porphyra yezoensis from Korea and Japan

The morphological and physiological characteristics of Pythium sp. isolated from Wando, Korea, were compared by the general mycological characteristics, behaviors to environmental conditions (e.g. temperature, pH, and salinity) and nutritional requirements for growth with those isolated from Fukuoka, Miyagi and Aichi, Japan. The number of hyphal swelling per visual field (31 mm(2)) of the isolate from Wando was significantly higher (P<0.05) than those of the Japanese isolates. The other morphological characteristics of the four isolates differed slightly. The four isolates grew at between 5 and 30 degrees C, and at between pH5 and 8.5. The optimal seawater concentration for growth of the isolates from Wando and Fukuoka was 80%, while those from Miyagi and Aichi was 50%. Growth responses of mycelium were high on bovine serum and laver extract in the isolates from Wando and Fukuoka, and on bovine serum and yeast extract in the isolates from Miyagi and Aichi. Growth responses for the carbon and nitrogen source of mycelium were the highest on starch and DL-methionine in the isolate from Wando, and on D-glucose and L-aspartate in the isolates from Fukuoka and Aichi, and on D-glucose and DL-methionine in the isolate from Miyagi, respectively. It is apparent that nutritional requirements of the four isolates differed slightly. Since the morphological and physiological characteristics of four isolates resemble each other well, the isolate from Wando seems to be Pythium porphyrae.