Collaboratrices et collaborateurs

Safe exchange of plant material relies on accurate diagnostic tools and up-to-date lists of regulated pathogens. However, some of these lists include obscure diseases, often reported only once in non-peer-reviewed publications such as conference proceedings. In a global effort to remove such agents from all regulatory lists, a recent publication identified over 120 agents/diseases for which essential information was lacking (Tzanetakis et al. 2024). These included agents associated with symptomatic plants, presumed to be of viral nature but for which no plant material was available and for which no sequence information was accessible. They were designated as phantoms. The initial list of these agents included the cherry rosette virus (CRV), which was first described as a nepovirus in cherry trees in Switzerland in 1994. In their study, Brown et al. described a novel nematode, Longidorus arthensis, as the vector of CRV. However, no isolate or sequences of this virus was available until today. Following an analysis of the collection held at Agroscope, a CRV isolate, designated #858, was identified. Isolated in 1997 on cherry trees in central Switzerland, it was then successfully inoculated on various herbaceous plants in the greenhouse. Infected Nicotiana clevelandii stored in the freezer for more than 20 years was successfully re-inoculated in 2024. The genome obtained confirmed that CRV is a nepovirus, and clusters with grapevine Tunisian ringspot virus (only RNA2 available), Paris mosaic virus 1 (Actinidia nepovirus A), Sichuan green pepper virus and Nitraria roborowskii nepovirus. Full characterisation of the viruses is underway and key results will be presented. With isolates and sequences now available, this virus has been removed from the list of phantom agents.