Potato is one of the most important crops in the world, and potato virus Y (PVY) is currently considered the most important viral pathogen of potato. In potato plants cv. Rywal, PVY induces a hypersensitive response (HR), which is an effective defense response determined by resistance (R) genes and manifests itself as the formation of necrotic lesions on infected leaves. The HR response involves the biosynthesis of salicylic acid (SA) in the cytosol, and the production of reactive oxygen species (ROS) in chloroplasts (chlROS) and apoplasts (apoROS). Using transgenic potato plants, we evaluated the influence of the listed components on the velocity of PVY spread and the occurrence of cell death. We found that altered levels of SA, chlROS and apoROS have different effects on virus spread. In addition to plants with decreased levels of SA, in the plants with decreased levels of chlROS, we also observed more virus at the edge and within the cell death zone, while this was not observed in plants with decreased levels of apoROS and plants with decreased levels of both apoROS and chlROS as well as altered spatial accumulation of SA. We observed that the largest viral foci prior lesion formation and the largest lesions also occur in plants with decreased levels of SA, while in the plants with decreased levels of apoROS, decreased levels of chlROS and altered spatial accumulation of SA we observed smaller viral foci and smaller lesions compared to control plants. In addition, smaller lesions compared to control plants also occur in plants with decreased levels of chlROS. These results indicate the differences in the spread of the virus immediately after infection, compared to after the cell death. In addition, we showed that altered concentrations of SA, chlROS and apoROS do not affect the systemic spread of the virus throughout the plant.
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