Rice panicles were collected from U. virens infected plants at day 3 after infection, the panicles were immers- ed in a solution of 3, 3’-diaminobenzidine tetrahydrochloride (DAB-HCl) for 3 hours at room temperature, after destained in ethanol:chloroform solution, rice flower organs were observed under microscope to exam- ine ROS accumulation. DAB forms a brown polymerization product in the presence of ROS