Scientific relevance. Plant viruses cause a significant economic loss to potato production, especially if plants are infected at early growth stages and infections are mixed. Viral diseases reduce both yield and quality of harvested crops. Detection and identification of plant viruses are key important to prevent their spreading and to achieve potential yield predetermined by characteristics of varieties.Research methods. Seven potato varieties, bred in Russia and overseas, were used in the field experiment: Smak, Avgustin, Yantar, Laperla, Labella, Red Lady, Sante, Belmonda. Viral infection rate was measured by the percent of plants with symptoms to the total number of plants. In addition to infection frequency, a disease rate was described after visual estimation. Total RNA was isolated from the collected leaves according to Bekesiova I. et al. 1999 [13]. Qualitative and quantitative estimation of plant viruses in the samples were conducted by single-step real-time RT-PCR with fluorescent detection with the Applied Biosystems QuantStudio 5 and commercial kits “Potato Virus X, Y, M, L, S, A, PSTVd-RT” (Syntol Company) according to the official protocol of the kits.Results. As a result of our research, symptoms of mixed viral infection were described for potato varieties depending on concentrations and proportions of these viruses in a plant. Mixed viral infection in the potato field in Primorsky Krai comprised PVY, PVX, PVA, PVS, PVM, also PLRV and PSTVd.