Because of the impact on the quality and quantity of the crop, tobacco viral diseases are very important. Potato virus Y (PVY) is one of the most important tobacco viruses and has a worldwide distribution. Studying the reaction of tobacco cultivars to PVY and identifying the possible sources of resistance is important and aimed at achieving resistant cultivars. Therefore the reaction of 31 tobacco cultivars was assessed in a completely randomized design with 10 replicates under greenhouse conditions. Seeds were planted in pots containing sterile soil and seedlings were transferred to individual pots. Seedlings were mechanically inoculated at four-leaf stage with a PVY isolate. The development of symptoms was recorded for one month by a grade from 0 (no symptoms) to 11 (for necrotic stem). The means were compared using Duncan’s test. The cultivars with means above or below the total mean were selected as susceptible or tolerant cultivars, respectively. The final test on 7 selected tolerant cultivars were performed in the same way. Several samples were tested by ELISA to confirm the presence of infection. The results showed that in the preliminary experiment with comparison of the severity of symptoms and the concentration of virus, the cultivars Tr. 27, Tr.1, H.Tr.1, Samsoun katezini, Tr.23 and Tyk Kula were identified as tolerant cultivars
