Abstract
In hydroponics, the damping-off of spinach seedling by Pythium butleri was remarkably suppressed by highly concertrated nutrient solution (2-fold or 3-fold of standard solution). Zoospores of P. butleri encysted within a few minutes in highly concentrated nutrient solution, and they could not attach to the root surface of spinach. The zoospore encystment also occurred in the solutions of 0.02M each of calcium nitrate and calcium chloride, 0.05M of magnesium sulphate. and 0.2M each of mannitol, glucose and sucrose. These results indicated that the suppression of the damping-off in high concentration of nutrient solution was due to zoospore encystment induced by osmotic pressure of the nutrient solution.
