In addition to the nine most important potato viruses described in the previous data sheets and to the South American quarantine viruses (16 species which are not covered in this guide), there is another group of potato viruses (14 species) of limited importance but occasionally present in Europe.
Natural infections of potato plants by some of these viruses sometimes only affect a single cultivar in just one country. Thus the Tomato mosaic virus (ToMV) has only been described in Hungary on the cultivar Astilla.
Other previously well distributed potato viruses are now rare: for example, the Potato aucuba mosaic virus (PAMV, photo 1), despite the fact that, like PVX, it is easily transmissible by contact. Internal and external necroses caused by PAMV on potato tubers are similar to those caused by AMV (Alfalfa mosaic virus), although usually they are only found in storage in unrefrigerated warehouses.
Most of the minor viruses are polyphagous viruses that occasionally infect the potato plant such as the Cucumber mosaic virus (CMV).
Other viruses deserve attention because they cause symptoms in potato tubers:
- Tobacco necrosis virus (TNV);
- Alfalfa mosaic virus (AMV);
- Tomato black ring virus (TBRV).
Mention should also be made of the Potato virus V (PVV), which is quite common in Europe and of the Pepino mosaic virus (PepMV), which is not included in the list of potato viruses but which can infect potato plants and is such a threat that it is useful to be aware of its symptoms.
Generally speaking, these viruses do not justify any particular control measures in Europe, where currently they are not common at all. Nevertheless, strict controls (quarantine procedure) need to be applied prior to the introduction of plant material, for prebasic and basic materials and for genetic resources.