Necrosis in Solanum tuberosum stems infected with potato virus Y by grafting

This work examined the distribution of necrosis on stems of two cultivars of potato (Ania, Glada) with different levels of resistance to PVY infection. Potato virus Y particles and/or cytoplasmic (CI) and amorphous inclusions (AI) were identified in insert and offshoot potato cells of susceptible cv. Glada. Cytoplasmic inclusions were not observed in insert and offshoot stems of resistant cv. Ania, although there were numerous deformations, degeneration and tissue necrosis. It was found that (1) necrotic reactions were the form of plant cell response for both the PVY-resistant and susceptible cultivars, (2) development of necrosis in vascular tissue did not prevent the pathogen from spreading outside the necrotic region in the less resistant cultivar (Glada), and (3) extreme resistance to PVY in potato plants, determined by the Rysto gene, was manifested in the absence of virus particles and cytoplasmic inclusions in infected plant cells.