Prevalence and molecular characterization of important potato viruses in the Tokat province of Turkey

Background: It is believed that viruses affect potato yield more than any other pathogens worldwide. Method and Results: We report here on a survey of the four most common potato viruses in the Tokat Province of northern Turkey. Leaf samples were collected from potato plants showing signs of viral diseases in five districts of the province. Over 400 leaf samples were tested using RT-PCR with virus-specific primers. Among the one or more viruses detected in 218 (52%) leaf samples, Potato virus Y (PVY) was the most common (47.1%), followed by potato virus S (PVS; 16.7%), potato virus X (PVX; 6.0%) and potato leaf roll virus (PLRV; 5.3%). The most common mixed infections were PVY + PVS (6.9%). A phylogenetic analysis of the gene sequences showed all Turkish PVS isolates to be clustered with the PVS group, two PVY isolates with the PVY group and one isolate with the PVY group. Turkish PVX isolates are in the Type X group of the two major PVX isolate groups. The Turkish PLRV isolates were separated into two major groups depending on the results of the phylogenetic analysis, with six cases in Group 1 and one in Group 2. Conclusions: PVY, PVX, PVS and PLRV were detected in potato production areas in Tokat. A phylogenetic comparison of the gene sequences revealed all Turkish isolates to be immigrant members of the world populations of these viruses. Our results emphasize the importance of the strict quarantine control of plant materials entering Turkey.