2023-11-102023-11-102081-2787https://bc.iung.pl/handle/123456789/479Potato virus Y (PVY) is one of the most importantpathogens affecting tobacco. Some cultivars, such as VAM andWiślica, carry va type of resistance which can be broken by morevirulent strains of PVY. Here, we compare effects of inoculationof resistant (VAM, Wiślica) and susceptible (Samsun H, Burley21) cultivars using three PVY isolates differing with their virulence.We recorded symptoms of PVY infection two, three and fourweeks after inoculation and confirmed the presence of the virusin the leaves using DAS-ELISA tests done four weeks after inoculation.We observed one-week delay in the development of thefirst disease symptoms on resistant cultivars compared to susceptibleones. However, four weeks after inoculation, DAS-ELISAtests confirmed the presence of the virus in the tissues with visiblesymptoms. At this time, disease symptoms were observed on alltested cultivars inoculated with two isolates (named IUNG 16 andIUNG 13). The least virulent isolate (IUNG 5) broke the resistanceof Wiślica but not VAM, what contradicts results of previous inoculationstests using this isolate. Previously, IUNG 5 was unable tobreak the resistance of Wiślica. The observed change of virulenceof isolate IUNG 5 was confirmed in subsequent inoculation tests:PVY from the infected Wiślica broke resistance of VAM.application/pdfPotato virus YPVY resistanceNicotiana tabacum