Zoospore chemotaxis of two mangrove strains of Halophytophthora vesicula from Mai Po, Hong Kong

Chemotactic response of zoospores of two mangrove strains of Halophytophtho ra vesicula (isolates LEM-031 and LEM-036) was evaluated using a capillary root model for chemotaxis assay. Different compounds were tested as attract ants, including amino acids, carbohydrates, lectins, ethanol and plant mate rial and extracts. Zoospores of the two strains were found to be chemotacti cally attracted to all the plant material and extracts tested. Among amino acids, glutamic acid elicited strong chemotactic activity on zoopores of bo th strains while asparagine on zoopores of isolate LEM-031 only. Ethanol an d the polysaccharide pectin also induced a strong chemotactic response on z oospores of both strains. True chemotaxis of zoospores was observed among s ubstances which elicited positive chemotactic response, except for glutamic acid which resulted in are-attraction response on zoospores. Trapping of a ccumulated zoospores was observed in pectin, ethanol, glucose, fructose and glutamic acid which resulted in encystment and subsequent germination. A n egative chemotactic response was observed in lectins and the amino acids ar ginine, methionine and histidine, for both strains.