Rice Blast disease, caused by the filamentous, ascomycete fungus Magnaporthe oryzae, can result in devastating losses to crops worldwide. It is a virulent pathogen, which can lead to complete crop loss when conditions are favorable. Magnaporthe oryzae is a major roadblock to increasing rice production and furthermore, infects other important crops such as barley, finger millet and more recently, wheat. We seek to address the plant-fungal interactions between two hosts, rice and barley, and M. oryzae that occur at the beginning of the infection cycle. Understanding these interactions could provide us the ability to better equip our hosts with a strengthened basal immunity and help protect the crop against the pathogen. While there is a substantial amount of research on rice as a host, our specific goal is to uncover the fungal genes that weaken the host's basal responses, specifically related to reactive oxygen species (ROS). Reactive oxygen species play an important role in the plant's basal defenses; during pathogen attack the plant produces ROS causing a toxic environment. Previous work in our lab generated a fungal strain containing an endogenous sensor (HyPer) of ROS, which was demonstrated to specifically detect hydrogen peroxide during these plant-fungal interactions. Our goal will be addressed through two objectives: first, through generation and screening of a random insertion mutational library in a HyPer M. oryzae line to identify ROS-related phenotypes, and second, through characterization of the mutant lines using live-cell imaging in planta.