Seed potatoes certification is a control process aimed at ensuring the production of high-quality seed potatoes and to limit the spread of diseases. Among these pathogens, viruses can easily transmit through the vascular system, from one generation to the next and are subject to post-harvest testing and in particular, Potato virus Y (PVY) and Potato leafroll virus (PLRV). Dupuis et al. (2024) estimated the average yield loss of 223 kg/ha for 1% PVY infection that comes with economic impacts of about an estimated at 187 M EUR in the European Union for the whole potato sector. Numerous species of aphids transmit these viruses respectively in a nonpersistent (PVY) and persistent manner (PLRV). In Switzerland, to rigorously monitor the sanitary status of the lots, each multiplication plot is inspected two to three times during the growing season. Since 2016, the prevalence of PVY and PLRV has been monitored annually in the laboratory through molecular analysis as part of the seed potato certification process. 220,000 tubers were collected per year out of 1,000 lots, with an average of 200 tubers per lot. Then, 10,000 RT-qPCR were performed on tuber samples to detect PVY and PLRV (Schumpp et al., 2021). These data allowed us to assess the evolution of the prevalence of these viruses in Switzerland over the last nine years. Each year, the seed potato lots are mostly infected by PVY, but the infection rate of PLRV and of infections by both PVY and PLRV tend to increase. We note that from 2019 to 2023, 12 to 21% of the lots were infected by both PVY and PLRV, although 2% to 5% of the lots were infected by both PVY and PLRV from 2016 to 2018 and in 2024 (Figure 1). Some varieties are more susceptible to these viral infections, as reported by Dupuis et al. (2019). The data indicate that, the rejected areas tend to increase in Switzerland since 2016, not only due to virus infection but also because of blackleg (Pectobacterium spp. and Dickeya spp.) and late blight (Phytophthora infestans), depending on the weather conditions. Given the increase of rejected areas, which could rise further in the context of climate change, improved protection and new control strategies must be developed to limit pathogen infections.
