The effect of added nitrate on the growth ofOphiobolus graminis

Summary The effect of nitrate amendment at several concentrations was compared for four isolates ofOphiobolus graminis with reference to both the saprophytic ability and pathogenicity of each isolate. Maximum saprophytic growth occurred on straws impregnated with a solution of 1.0 and 1.5% sodium nitrate. Minimum saprophytic growth occurred with 0 and 2.0% nitrate. Addition of nitrate increased the pathogenicity of virulent isolates ofO. graminis more than it stimulated root production by the host; so that the highest percentage of plants killed and severely diseased occurred when the inoculum of infected straws was impregnated with 1.5% sodium nitrate.