Production and Degradation of Reactive Oxygen in the Interaction between Rice and Rice Blast Fungus

Abstract

Higher plants produce reactive oxygen species (ROS) in the defense responses, which acts as a second signal leading to the later responses. We analyzed the interaction between rice and rice blast fungus by monitoring the level of H₂O₂. Spore suspension from different field isolate of the fungus showed different activity to induce ROS accumulation in the media, partially ascribed to the different activities of catalase-like activity in the spore suspension. When spores of an isolate, INA68-137, were washed with water and inoculated on the leaf sheath of a compatible rice cv, Nipponbare, a significant delay in the growth of hyphae was observed in parallel with the increase in the number of cells positive in DAB-staining. These results strongly indicate that the post-spore fraction of INA68-137 includes factors which positively regulate the growth of invading hyphae.