EFFECT OF SOIL SATURATION DURATION AND SOIL-WATER CONTENT ON ROOT-ROTOF MAIZE CAUSED BY PYTHIUM ARRHENOMANES

Three aggressive isolates of P. arrhenomanes (201-25, 7E, and 5E) were used to evaluate the effect of soil saturation duration and soil wate r content on maize root rot. Maize seedlings grown in infested and non infested soil:sand mixtures were subjected to saturation durations of 0, 6, 12, 24, or 40 h. Four silty-clay loam soil:sand mixtures (100:0, 80:20, 50:50, and 0:100) were used to evaluate the effect of soil wat er content on disease development. Matric water potential was maintain ed at -1 J/kg during the experiment except for the saturation period. Multiple regression analysis was used to evaluate the effect of satura tion duration and soil water content on root and shoot dry weight. Neg ative slope values were obtained for increasing saturation duration an d reduced water content (increased proportion of sand to soil). Interc epts of regression lines for shoot and root dry weights were lower for the infested soil:sand treatments than the noninfested treatments. Th ese results indicated that growth of maize plants was negatively affec ted by increased flooding duration, lower soil water content, and pres ence of the pathogen. Growth of maize was significantly (P = 0.05) les s in the presence of the pathogen than in non-inoculated control treat ments at each soil water content and flooding duration.