Potato Virus X (PVX)

PVX is a common RNA virus of potato and the type member of the genus Potexvirus. It spreads by contact and in seed tubers, and on its own usually causes only mild or no symptoms while still reducing yield.

Most often a faint leaf mosaic or mottling, sometimes mild crinkling or reduced vigour, and frequently nothing visible at all. Severe strains can cause necrosis in sensitive cultivars.

Mainly by mechanical contact, through infected sap on knives, equipment, machinery, hands and plant-to-plant touching, and through infected seed tubers, which carry it from season to season and over long distances.

Yes. An infected tuber grows into an infected plant, so seed is the main way PVX persists and travels. This is why certified, virus-tested seed is the core control.

No. PVX has no specific insect vector. There are scattered reports of non-specific transfer by biting insects, but no aphid is a recognised natural vector, which separates PVX from PVY and PLRV.

Yes, and this is its most important trait for seed growers. Many infections are symptomless or latent, so a healthy-looking plant can still be infected and pass the virus on.

Not reliably by eye, because symptoms are mild and shared with other problems. Suspect plants should be confirmed by a laboratory test such as ELISA or RT-PCR.

By ELISA for routine high-volume testing, by RT-PCR and RT-qPCR for greater sensitivity and quantification, and by high-throughput sequencing when unexpected or novel viruses need to be found.

No. There is no spray or treatment that cures an infected plant. Fungicides and insecticides do not work against it. Management is about prevention, clean seed and sanitation.

Plant certified virus-tested seed, rogue infected plants, disinfect cutting knives and equipment, control volunteers and weed hosts, and grow resistant cultivars suited to the region.

They act synergistically. A silencing suppressor from PVY lets PVX build up more, so the mild mosaic of single infection becomes the severe rugose-mosaic disease, with yield losses reported up to about 80%.

Yes. Single infection typically cuts tuber yield by roughly 10 to 40% depending on strain and cultivar, and much more in mixed infection. Mild strains may cause little measurable loss.

Yes. Many cultivars carry the hypersensitivity genes Nx or Nb, and some carry the extreme-resistance gene Rx. However, resistance-breaking isolates exist, so choose cultivars recommended for your region.