| Summary: | 碩士 === 國立臺灣大學 === 植物病理與微生物學系 === 92 === Pythium aphanidermatum is a destructive pathogen in hydroponical systems. Because it can discharge zoospores, hydroponical systems favor their discharge and dispersal. The purpose of my master thesis is to solve hydroponic Chinese cabbage root rot diseases by means of combining mycoparasitic Pythium spp. and the material which can inhibit zoospore discharge of zoosporic pathogens.
For bating mycoparasitic Pythium spp., Botrytis cinerea was a better bating-fungus than Phytophthora parasitica、Rhizoctonia solani (AG1)、Sclerotinia sclerotiorum and Sclerotium rolfsii. When using Botrytis cinerea as a bating-fungus, more mycoparasitic Pythium spp. could be isolated from soil. More mycoparasitic Pythium spp. were isolated from cultivated soil samples than from non-cultivated soil samples. The more fresh cultivated soil samples were, the more mycoparasitic Pythium spp. could be isolated. Totally, 199 isolates of mycoparasitic Pythium were isolated. Among them, 54 isolates of P. acanthicum、7 isolates of P. acanthophoron、112 isolates of P. oligandrum、24 isolates of P. periplocum were identified, and 2 isolates of SWO (smooth walled oogonium) mycoparasitic Pythium spp. were unidentified. P. acanthophoron is a new record for Taiwan. These mycoparasitic Pythium isolates were tested for their rhizosphere competence. It was found that 8 isolates of P. oligandrum had better rhizosphere competence.
Both de-oil seeds of oiltea and the soapberry are nature surfactants. 200ppm of de-oil seeds of oiltea lyzed vesicles of Pythium aphanidermatum and cytoplasma of discharging sporangia of Phytophthora parasitica. 400ppm of de-oil seeds of oiltea made zoospores of Pythium aphanidermatum and Phytophthora parasitica stop swimming. 100ppm of soapberry liquid extracts lyzed vesicles of Pythium aphanidermatum and cytoplasma of discharging sporangia of Phytophthora parasitica. 250ppm of soapberry liquid extracts lyzed zoospores of Pythium aphanidermatum and Phytophthora parasitica. 2.5ppm of sodium hypochlorite lyzed vesicles of Pythium aphanidermatum and cytoplasma of discharging sporangia of Phytophthora parasitica. 5ppm of sodium hypochlorite lyzed zoospores of Pythium aphanidermatum and Phytophthora parasitica. All de-oil seeds of oiltea , soapberry liquid extracts and sodium hypochlorite controlled the spread of the zoospores. When either de-oil seeds of oiltea had been used at 400ppm or soapberry liquid extracts had been used at 250ppm in cultivate solution, phytotoxic symptoms were observed in Chinese cabbage seedlings. But when sodium hypochlorite had been used at 20ppm in cultivate solution, no phytotoxic symptoms were observed in Chinese cabbage seedlings.
Combining MP4 Pythium oligandrum and 20ppm of sodium hypochlorite controlled hydroponic Chinese cabbage seedling diseases caused by Pythium aphanidermatum.
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