First report of Andean strain of potato virus S in Estonia
Potato virus S (Carlavirus sigmasolani, PVS) can be subdivided into three strains, the ordinary strain (PVS-O) which has worldwide distribution including in the EU, and the Andean strains (PVS-A and PVS-RVC) which are considered to be absent from the EU. Non-European isolates of PVS are EU Quarantine pests (under Regulation (EU) 2019/2072 Annex II A).
In Estonia, PVS-O was previously reported at low incidence in potato seed lots tested for certification between 2007 to 2022 (van der Sman et al., 2025). In September 2025, seed lots from 34 potato fields were analysed by high-throughput sequencing (HTS). The Andean strain of potato virus S (PVS-A) was reported from neighbouring fields in Viljandi county where seed potatoes had been grown from seed tubers originating from Germany. The PVS-A isolate showed the highest nucleotide identity with an isolate from Kazakhstan. The identity of the pathogen was later confirmed by RT-PCR testing. van der Sman et al. (2026) suggests imported seed material as a possible introduction pathway of PVS-A.
The situation of potato virus S-Andean strain PVS-A in Estonia can be described as: Present, not widely distributed and under official control.
Sources
van Der Sman P, Pata P, Järvekülg L, Sõmera (2026) Long-term monitoring of six potato viruses in Estonian seed potatoes and an assessment of susceptibility of potato varieties to PVY. Potato Research 68(3), 3123-3145. https://doi.org/10.1007/s11540-025-09862-0
van der Sman P, Stražev A, Sõmera M (2026) First report of Potato Virus S Andean isolates infecting potato in Estonia. Plant Disease (early view) https://doi.org/10.1094/PDIS-05-26-0980-PDN