Potato virus S (PVS) is one of the damaging and limiting agents affecting potato cultivation in Mazandaran Province, in north Iran. This virus belongs to the genus Carlavirus, characterized by an isometric particle morphology, a single-stranded RNA genome, and a relatively narrow host range. PVS typically exhibits an additive effect and is often found in co-infection with other potato viruses. Considering the observed symptoms of the spread and damage caused by this virus in potato fields of Mazandaran Province, this study was conducted to carry out molecular identification and determine the distribution areas of the virus within the province. A total of 94 plant samples were collected from potato fields in three regions; Savadkuh, Galugah, and Parkuh, in Mazandaran Province during 2023–2024. Total viral RNA was extracted from samples displaying severe disease symptoms, and the coat protein gene region of the virus was amplified using RT-PCR. A band of 1,118 base pairs was detected. One positive sample from each region was selected and sent to Macrogen Inc. (South Korea) for sequencing. After sequencing, the similarity of the obtained sequences to the corresponding gene region of other isolates of this virus was determined using phylogenetic software. The results showed that Iranian isolates of this virus fall into two groups; Group I: includes isolates from Iran, Syria, South Korea, China, and Germany, while Group II contains only two Iranian isolates. The molecular identification of isolates of this virus in this province, their distribution areas, and their genetic similarity to isolates from other countries are reported for the first time.
