The influence of temperature on the exudation of nutrients from cotton seeds and on preemergence damping-off byRhizoctonia solani

摘要

Evidence is presented suggesting that increased seed exudation is a major factor contributing to increased preemergence damping-off of cotton seedlings byRhizoctonia solaniat low temperatures.About seven and three times as much total amino acids and sugars were exuded at 18 and 24 deg;C, respectively, as at 30 deg;C, by germinating cotton seeds of equivalent physiological age. Sixteen amino acids and five sugars were exuded. Seed exudation is not related to rate of germination or to respiration.Accumulation of seed exudate at low temperatures was related to increased pathogenesis in vitro and in soil. This appeared to be becauseR. solanicompetitively used this exudate to increase its inoculum potential near the germinating seed, thereby becoming more virulent on the susceptible juvenile tissues of the seedling.