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Reactive Oxygen Species (ROS) generated during plant-pathogen interactions are antimicrobial compounds that can either directly kill the pathogens or slow the infection process. ROS can activate defense responses to ameliorate the amount of disease, and affect the expression of genes in ROS-generation and detoxification pathways. We observe an increase in ROS levels during a short post-inoculation period in barley. ROS halos are formed directly beneath appressorium of <i>Magnaporthe oryzae</i>, accompanied by cell wall appositions. A successful pathogen will likely have ROS regulating mechanisms to tolerate such inhospitable situations. MoHyr1 and MoAp1 have been found to be involved in regulating oxidative stress in <i>M. oryzae</i>. <i>MoHYR1</i> has a glutathione peroxidase domain and in <i>Saccharomyces cerevisiae</i>, its homolog specifically detoxifies phospholipid peroxides by forming an inter-molecular disulfide bond with yAP1. We generated fungal mutants lacking this gene and noted their decreased ability to tolerate ROS <i>in vitro</i> and <i>in planta</i>. Moreover, deletion of this gene caused a virulence defect in <i>M. oryzae</i>. We further discovered that MoHyr1p and MoyAp1p appear to not interact with each other based on co-localization and yeast two hybrid assays, which is contrary to findings in <i>S. cerevisiae</i>. We also discovered that over-expressing MoyAp1p partially rescues the <i>Mohyr1</i> mutant phenotype. These results, along with several ROS generation pattern studies, will be presented.<p><p>Keywords: Fungus, Cereals-Grains, Rice