APEX1 and infection: Almost all of them are related to the antioxidative system of the plant, such as higher amounts of H2O2, oxalic acid and/or ascorbic acid, induction of the genes for oxalate oxidase (G-OXO), germinal-type oxalate oxidase (Glp), and dehydroascorbate reductase (Dhar) [12,56], as well as higher activity of the APX enzyme [57,91] in resistant genotypes in the interval from 0 h to three days after infection with M. perniciosa.