M. Fahim Abbas

POTATO CULTIVATION was too old as 2000 years ago from South America Andes and the potato is from genus solanum while only 8 species are cultivated. The cultivated potato (Solanum tuberosum L) is a starchy, tuberous and dicotyledonous crop belongs to the family solanacea and potato is ranked as 4th staple food crop with production of 314 million metric tons annually in the world followed by wheat, rice and maize. It has fifth position among crops grown for human consumption while potato can also be used for animal feed and as a rich source of starch and alcohol. Potato crop provides 15 times more production and calories per unit area are also higher than wheat and rice and potato contains 77.8 per cent water, 2.0g protein, 13g calcium, 0.06g riboflavin, 25mg/100g vitamin C, 12mg ascorbic acid, 0.11mg mythiamin, 1.18mg niacin and per 100g energy of edible protein is 85 calories.

In Pakistan, potato is one of the main cash crops for the farmer and three consecutive potato crops grow annually which plays a vital role in GDP of the country. Pakistan can be separated into eight agro ecological zones for the production of potato crop which are different in altitude, longitude, latitude, topography, climate, soil and irrigation infrastructure while northern Pakistan is the key for seed tuber producing which supplies the tubers to the rest of the country.

Potato is cultivated over an area of 127.7 thousand hectares and annual production is 3726.5 thousand tons in Pakistan, which is very low as compared to other potato growing countries. Bacteria, nematode, fungus, viruses and a biotic factor reduce the yield of potato crop in Pakistan and viral diseases are much more difficult to control.

High yielding foreign potato varieties have been obtained by the potato growers of Pakistan without any certification which has certainly enhanced the yield but at the same time new problems including certain viruses have been reported in potato crop. Among the potato viral diseases, Potato Virus PVY (Y), Potato Virus X (X), Potato Leaf Roll Virus (PLRV), Potato Virus A (PVA), Potato Virus S (PVS), Potato Mop Top Virus (PMTV) and Potato Virus M (PVM) have been reported in Pakistan with 58-83 per cent yield losses.

Potato germplasms screen through Enzyme Linked Immunosorbant Assay (ELISA) because a large number of samples can be certified with in short period of time but ELISA is not a reliable method at initial stage of viral infection. Viral genome multiplied into billion of copies within few days or week and dispersed from viral infected potato plants to healthy plants by mean of insect vector along with infected tools because farmers do not use precaution measures for the insect vector and infected tools.

Certifications of potato germplasms require a sufficient, sensitive and reliable detection method to confirm one viral infected potato sample in all healthy samples. New molecular methods like Polymerase Chain Reaction (PCR) assay were introduced in the world for successful, reliable and sensitive detection of potato viruses, which reduced the dispersal of viruses and enhanced the yield of potato crop significantly.

Molecular tools, resistance potato varieties against viruses, insect and weeds control and tissue culture along with chemotherapy and thermotherapy treatments are more effective to control viral diseases in potato crop and may enhanced the income of the potato growers.

The writer is PhD scholar at Department of Plant Pathology, Pir Mehr Ali Shah Arid Agriculture University Rawalpindi, Pakistan.

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