Effect of soil saturation duration and soil water content on root rot of 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 water content on maize root rot. Maize seedlings grown in infested and noninfested 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 water content on disease development. Matric water potential was maintained at -1 J/kg during the experiment except for the saturation period. Multiple regression analysis was used to evaluate the effect of saturation duration and soil water content on root and shoot dry weight. Negative slope values were obtained for increasing saturation duration and reduced water content (increased proportion of sand to soil). Intercepts of regression lines for shoot and root dry weights were lower for the infested soil:sand treatments than the noninfested treatments. These results indicated that growth of maize plants was negatively affected by increased flooding duration, lower soil water content, and presence of the pathogen. Growth of maize was significantly (P = 0.05) less in the presence of the pathogen than in non-inoculated control treatments at each soil water content and flooding duration