The tuber necrotic strain of Potato Virus Y (PVYNTN) is considered the most aggressive strain of PVY. Effects of PVYNTN on some metabolic activities and cytological characteristics of three potato cultivars Lady Rosetta, Mondial and Santana were investigated. Virus concentration, infection percentage and disease severity were also estimated. Potato cultivars differed in their susceptibilities to PVYNTN infection, whereas various levels of apical necrosis with different disease severity 30, 60 and 100% were recorded for Mondial, Santana and Lady Rosetta cultivars respectively. The lowest amount of leaf pigments was found in PVYNTN-infected potato cv. Santana. Total phenolic and total soluble sugars contents were highly accumulated in PVYNTN-infected leaves compared to healthy ones. A noticeable increased level of sodium cation was detected in PVYNTN-infected leaves of potato cv. Lady Rosetta. Electron microscopy analysis showed changes in nuclei, mitochondria, cell walls, and chloroplasts in PVYNTN-infected cells of potato cultivars compared with healthy. Genetic variations among potato cultivars under PVYNTN infection were detected by Inter Simple Sequence Repeat-Polymerase Chain Reaction (ISSR-PCR) analysis. The ISSR primers amplified 57 bands, and 52 showed polymorphism (91.23%). According to our results, potato cvs. Lady Rosetta and Santana were highly susceptible to PVYNTN infection while, Mondial was moderately resistant.
Key words: PVYNTN, disease severity, physiology, cytology, ISSR-PCR, potato cultivars.