Abstract: Rice leaves were treated with photodynamic dyes or 2-mercaptopyridine N-oxide, which are light-dependent sources of reactive oxygen species (ROS). As a result, disease severity was reduced on blast-challenged upper leaves. The effect was diminished by one-day darkening of treated plants or by co-treatments with antioxidants. The light-activated compounds increased superoxide production and ROS-dependent fungitoxicity in diffusates of systemically protected leaves. It is suggested that light-driven formation of ROS in treated leaves induced systemic acquired resistance, which also was realized involving ROS.