Inhibition ofHelminthosporium oryzae andAlternaria solani byStreptomyces longisporus (Krasil'nikov) Waksman

Summary Streptomyces longisporus, isolated from field soil in association with wheat stubble, showed antagonism againstHelminthosporium oryzae andAlternaria solani in vitro as well as in soil (autoclaved). The organism or its filtrate showed formation of a distinct zone of inhibition in culture against the pathogens. Infected potato seed pieces or rice grains dipped in the culture filtrate prevented or reduced disease incidence to different degrees depending on the period of treatment. Infestation of soil (autoclaved) withS. longisporus and the pathogens in various combinations also reduced disease incidence. Among such combinations, infestation withS. longisporus followed by the pathogens proved to be the most efficient.