Potato is placed at third position among the staple food crops and fifth for human consumption. Potato cultivation is too old as 2000 years ago from South America. Potato is from genus solanum and only 8 species of it are cultivated. The edible potato (Solanum tuberosum L.) has achieved a significant importance among non-cereals food crops and it can also provide 15 times more yield as compared to cereals.
Potato has a great adaptability to wide range of temperatures (tropical, subtropical and temperate regions) and soils (light sands to heavy clay loam) but it is sensitive to drainage and aeration. Potato is small (30-100 cm) vegetative propagated crop and tuber’s bud (eyes) sprout grows into mature plants. Tubers formation starts at flowering stage and cease at fruit stage while the size of tuber depends upon the cultivar and age of plants.
A significantly high number of pests and pathogens can be carried over from one generation to the next by propagated vegetative material. Among them, at least 37 viruses can naturally infect potato crops. Potato production occurs from three crops during a year; autumn, spring and summer crops in the plains and the hilly areas of Pakistan. In Pakistan, potato is cultivated over an area of 127.7 thousand hectares with an annual production of 3726.5 thousand tons which is very low as compared to other potato growing countries of the world. High yielding foreign potato varieties significantly increased the yield of potato crop in Pakistan but at the same time, it resulted new viral problems like Potato virus X (PVX), Potato virus Y (PVY), Potato virus S (PVS), Potato leaf roll virus (PLRV), Potato virus A (PVA) and Potato virus M (PVM) which were reported in spring, summer and autumn potato crops of Pakistan and caused up to 83% yield losses.
Potato virus Y was first time reported in Pakistan by Mirza (1978) and it was among the mainly important diseases of potato in the plains of Punjab. This virus is scattered almost throughout the country with a frequency of 2-25% and losses caused by PVY in Pakistan were projected 58-83%. Natural hosts of PVY in Pakistan are tobacco, tomato and chili. During the year 1995, the percentage disease incidence of PVY was 52.77% in Toba Tek Singh, 28.20% in Jhang, 27.83% in Sialkot, 18.72% in Chiniot, 14.37% in Gujranwala, 12.72% in Okara and 6.81%in Sahiwal. The incidence of PVY was increased 48% (2010-11) and 52 % (2011-12) in Sahiwal and this might be due to the continuous introduction of viruses through imported seeds.
Chemicals are not available for directly controlling viral diseases of plants in the field. In Pakistan, Enzyme Linked Immunosorbant Assay (ELISA) is used for diagnostic of PVY. ELISA is unable to detect the virus at initial stage of infection (low titer). Few viron of PVY (theoretically one) in infected plants multiplied into billions of copies with in few days or weeks and it disperse to healthy potato plant through insect vector and agricultural tools. The increasing incidence of potato virus Y in the main potato growing areas of Pakistan is getting an alarming position and it should be tackled immediately. New sensitive tools (polymerase chain reaction) should be introduced in the diagnostic laboratories for sensitive and reliable detection (low titer) of PVY. Resistant or tolerant potato varieties against PVY, meristem culture, treatment with chemotherapy and thermotherapy, application of new molecular tools and insect pests along with weeds control may play a pivotal role in reducing yield losses in potato crop. Molecular identification of these viruses will also be helpful in developing an integrated control strategy and resistance source against potato virus diseases. The high yield of crop will improve farmer’s income and it can also play a significant role in the GDP of the country.
About author: Muhammad Fahim Abbas is a Ph.D scholar at Department of Plant Pathology PMAS Arid Agriculture University Rawalpindi, Pakistan.