Potato virus A (PVA) belongs to Potyviridae (genus Potyvirus), the largest virus family infecting plants and can cause yield losses of up to 40 %. It is widely distributed in the potato growing areas. Its natural occurrence and economic importance are mostly restricted to the cultivated potato. This virus is transmitted through infected tubers or by any of the vegetatively propagated planting material and by several species of aphids in non-persistent manner. The PVA genome is composed of single-stranded RNA of about 9.5 kb that is encapsulated by the virus-encoded coat protein (CP). The CP (269 aa) is produced from the C-terminal part of the polyprotein. The particles are elongated filamentous, normal of 730 nm in length and 15 nm in diameter. The symptoms of this virus include slight and transient mosaics that are particularly visible in cloudy weather. It can also induce mosaic faint mottling, slight crinkling of leaves and inter-veinal and veinal chlorosis. These symptoms can be reinforced by placing a sheet of white paper under the leaf. In case of mixed infection with Potato virus X or Potato virus Y it show crinkle symptoms.