Abstract
Potato is one of the main cash crops for the farmer and also contributes a considerable amount in Gross Domestic Product of Pakistan because it is cultivated as a garden vegetable and also on commercial scale. In high altitude valley, potatoes are grown as summer crop while in the plains and low valleys three consecutive crops can be grown per year. Potato crop provides 12-15 times more yield and calories production is also higher than wheat maize and rice while the average yield of potato crop in Pakistan is low as compared to other potato growing countries. Potato growers introduced high yielding foreign potato varieties which have significantly enhanced the yield of potato crop along with new viral problems and among these, Potato Virus A (PVA), Potato Virus M (PVM), Potato Virus S (PVS), Potato Virus X (PVX), Potato Virus Y (PVY), Potato Leaf Roll Virus (PLRV) and Potato Mop-top Virus (PMTV) have been reported in spring, summer and autumn potato crop along with 83% yield losses. In Pakistan, a large number of potato germ-plasms were certified through Enzyme Linked Immunosorbant Assay (ELISA) which is unable to detect the virus at initial stage of infection and new molecular tools like Polymerase Chain Reaction (PCR) assay were introduced for successful, sensitive and more reliable confirmation of viruses. Different percentage incidence of PVA and PVM was reported from main potato growing areas of Pakistan and no molecular optimization along with nucleotide evidence of these two viruses was reported from Pakistan. PCR assay were developed for molecular detection of PVX, PVY, PMTV, PVS and PLRV while no nucleotide evidence of PVS is still reported from Pakistani while coat protein (CP) gene sequence of PVX, PVY and PLRV from Pakistani isolates is available at the data bank of National Center for Biotechnology Information. The increasing incidence of PVY is getting an alarming position in potato crop of Pakistan and nucleotide sequence of CP gene reveals the presence of new strain in Pakistani potato while the nucleotide evidence of CP gene of PVX from a Pakistani isolate exhibiting the maxim homology with USSR isolate.
