The use of a monoclonal antibody for the detection of fungal parasite, Pythium sp, the causative organism of red rot disease, in seawater from Porphyra cultivation farms

A monoclonal antibody was prepared against specific strains of the fungal parasite, Pythium sp., the causative organism of red rot disease of Porphyra, and its effectiveness in the early detection of the fungal pathogen was assessed. The antibody recognized germ-tubes of zoospores from Aichi, Saga and Miyagi Prefectures but failed to identify non-germinating zoospores. The isotype of the antibody was IgG(1). Based on chemical and enzymatic treatments, the antigenic determinant was thought to involve glycoproteins of the germ-tube cell wall. For the enumeration of zoospores in seawater from Porphyra cultivation farms, seawater was pre-filtrated by 40 mu m nylon mesh and zoospores were concentrated on 3 mu m membrane filters and incubated in glucose-glutamate medium for 8 h at 20 degrees C. Germinating zoospores were detected by epifluorescence microscopy using the indirect fluorescent antibody technique. During the Porphyra cultivation season in Tsu, Mie Prefecture, germinating zoospores were detected from a farm employing a pole cultivation system. Between January 7 and February 13, 1995, numbers ranged from 11 germinating zoospores/l (the detection limit) to 4695 zoospores/l on January 25. No germinating zoospores were detected in seawater from a cultivation farm using a floating-net system despite the fact that diseased Porphyra thalli were observed in this farm.