Motility and Chemotaxis in Zoospores of Phytophthora palmivora (Butl.) Butl.

Zoospores of Phytophthora palmivora were motile for 84 h in distilled water at the optimum temperature, 17 °C. Motility time was markedly reduced by high zoospore density, by CaCl2, MgSO4.7H2O, glutamine, glucose, by buffer solutions and by frequent contact of zoospores with solid surfaces. The zoospores encysted instantly and disintegrated at pH 2.2–5.0 and in 1.0 mM CuSO4 and FeCl2 and 1.0 per cent (w/v) peptone solutions. Velocity of movement increased as the temperature rose from 8 to 33 °C. The zoospores responded chemotactically to an extract of cocoa pod but not to the exudate. Amino acids of the extract as well as other amino acids and sugars individually attracted the zoospores. Attracted zoospores quickly encysted and germinated; the germ tubes were uniformly directed towards source of stimulus.