A REVIEW PAPER ON POTATO MOP-TOP VIRUS (PMTV): OCCURRENCE, PROPERTIES AND MANAGEMENT

Potato mop-top virus (PMTV) is a plant pathogenic virus that affects potatoes. The virus was initially reported from Germany but now it has spread throughout Europe, Asia, South America and North America. It is responsible for spraing symptoms (brown arcs/lines, blemishes, and rings) on potato tubers and yellow chevrons or mopping (Shortened internodes) in the leaves and stems of plants grown from infected potato tubers. PMTV causes huge economic losses due to poor tuber quality. It is an important disease in the potato growing areas of the world. PMTV is tubular rod shape and has a single stranded positive sense RNA (+ssRNA) tripartite genome. RNA 1 encodes RdRp (viral RNA-dependent RNA polymerase). Coat protein (20kDa) and a larger protein (91kDa) is encoded by RNA2. RNA2 encodes larger protein (91 kDa) by read through (RT) of the amber termination codon of the coat protein. There are three conserved moldular sets of genes known as triple gene block (TGB) which are coded by RNA3. These TGBs are involved in cell to cell or long distance movement of PMTV. In nature, PMTV is vectored and transmitted by a soil born pathogen (Plasmodiophorid (Spongospora subterranean f.sp. subterranean abbreviated as ‘Sss') that itself causes the powdery scab disease on tubers. The disease caused by PMTV and Sss are favored by cool and damp conditions. PMTV remain in spore balls of Sss for several years even if the potato is not grown in the field. There are no efficient means to manage the virus nor its vector in an infested field, therefore, preventive measures are essential. Since PMTV along with its vector is causing important disease of potato, so understanding its molecular, biological, physical properties and management strategies is very important.