Infection with plum pox virus (PPV) caused higher activity of peroxidase, ascorbate peroxidase, and dehydroascorbate reductase in a susceptible peach variety, and in the resistant variety higher activity of ascorbate peroxidase, monodehydroascorbate reductase, glutathione reductase, and SOD, whereas catalase activity was reduced in both varieties [50]. This evidence concerns the gene CAT and infection.