EUPHRESCO V-PCN: Virulence of Globodera pallida and G. rostochienis populations used for standardised testing of potato varieties to assess resistance

Growing resistant potato cultivars is currently the most effective control measure against the potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis. The EU Commission prescribes that (new) potato varieties must be assessed for their resistance to PCN (EU 2022/1192). The degree of resistance of (new) potato varieties is expressed in accordance with the standard scoring notation, the Relative Susceptibility (RS). By including standard reference populations of G. pallida and G. rostochiensis (Pa1: Scottish, Pa3: Chavornay, Ro1: Ecosse and Ro5: Harmerz) and a reference susceptible potato variety (‘Desirée’), it is possible to relate the potato variety to internationally recognized standard levels of resistance based on the nematode multiplication rate. Additionally, local (virulent) PCN populations may also be included in the resistance assays.
The question arises whether the standard reference PCN populations, used and maintained in various EU countries, are still virulent after many years of multiplying on susceptible potato varieties and whether these are still representative for the types of virulence present in current field populations within the different EU member states (and Canada). Therefore, the aim of this EUPRESCO project is to compare these reference populations with each other and with local virulent field populations. It was shown that such populations have developed due to the selection pressure imposed by the long-term use of resistant potato varieties within short crop rotation cycles. Furthermore, it is the intention to agree on a harmonized protocol for testing the virulence of PCN populations, as member states are obligated by EU legislation (EU 2022/1192) to monitor their presence.