Pest categorisation of groups of viruses and viroids: the EFSA approach

The European Food Safety Authority (EFSA) has been requested by the European Commission to prepare the pest categorisation for two large groups of non-EU viruses and virus-like organisms, i) those infecting the genera Cydonia, Fragaria, Malus, Prunus, Pyrus, Ribes, Rubus and Vitis (fruit plants) and ii) those infecting potatoes. To accomplish these tasks, the EFSA Scientific Panel on Plant Health has established two Working Groups (WGs), which are respectively supported by two Framework Partnership Agreements, with the Institute for Sustainable Plant Protection-CNR, Italy (for the pest categorisation of viruses and viroids of fruit plants) and the Netherlands Food and Consumer Product Safety Authority (for the viruses and viroids of potatoes). The methodology adopted by both WGs to perform a pest categorization of these two large groups of pathogens includes the following steps: i) extensive literature searches to list the viruses and viroids infecting one or more of the host genera under consideration and to collect evidence on their geographic distribution; ii) identification of the viruses/viroids not known to occur in the European Union (EU) or occurring only in restricted areas of the EU (non-EU viruses) and of the viruses/viroids associated with inconclusive information to support their inclusion in the list of non-EU viruses (viruses with undetermined standing), iii) consultation with EU Member States to amend, if needed, the lists of viruses/viroids; iv) further categorization of viruses and viroids determined to be non-EU or with undetermined standing to evaluate whether they meet the requirements to potentially qualify as European Union quarantine pests. In the first step of this process, about 200 and 80 viruses/viroids infecting fruit plants and potatoes were identified, respectively. The lists of non-EU viruses/viroids and of viruses/viroids with undetermined standing for fruit plants and potatoes will be presented and an example for the pest categorisation of those of Cydonia, Malus and Pyrus will be discussed in more details. The most critical uncertainties in the pest categorization process regard information on distribution, host range, transmission, impact, and intraspecific diversity, particularly for those viruses recently discovered by high-throughput sequencing. The importance of these data for the pest categorization process will be discussed.