Tuesday, 12 May 2015

Natural Resistance against Yellow Dwarf Virus In Wheat

By: Muhammad Mahran Aslam- Department of Plant Breeding and Genetics, University of Agriculture Faisalabad

Common wheat (Triticum aestivum L.) is placed at the number one position among the staple foods of the world and it is the main source of calories, protein, certain vitamins and minerals. Pakistan has been divided into number of production zones and being staple diet of inhabitants, wheat occupies a central position in the agricultural of great agro-ecological areas where wheat is grown. The zoning is mainly based on cropping pattern, disease prevalence and climatological factors. Wheat cultivation encompasses a major production area of 8.33 million hectares engaging 33 per cent of the cultivated area of the country each year and exhibits production around 21 million tons. The same is not sufficient to meet with the country’s ever-increasing population growth rate of 2.6 per cent annually. Wheat occupies 70 per cent of Rabi season (winter season) and 33 per cent of total cropped area of Pakistan. Wheat is subjected to number of diseases caused by fungi, bacteria and viruses. Among viral diseases, the major problem becoming aggravated by day in Pakistan is Barley Yellow Dwarf Disease (BYDD) caused by Barley Yellow Dwarf Virus (BYDV). BYDV has serious impact on grain production and considered to be an important limiting factor for yield wherever cereals are grown and average yield losses due to natural BYDV infection can range between 11 and 33 per cent. BYDV is neither mechanically transmissible, nor through the seed, but are transmitted by insect vector (aphids) in a persistent, circulative but non-propagative manner. Environmental factors play several important roles in the BYDD cycle. High light intensity and relatively cool temperatures ranging 15-18(C generally favor expression of symptoms development, such as leaf discoloration, which may attract aphid to virus-infected plantsDominant gene, Bdv1and Bdv2confers tolerance to BYDV in some wheat varieties that induces slow yellowing. In Pakistan, total nucleic acid (TNA) of growing wheat varieties should be evaluated through polymerase chain reaction (PCR) assay using Bdv1andBdv2gene sense and antisense primers to check the presence or absence of resistance against BYDV. The 1% increase in BYDD incidence reduced the yield from 20 to 50 kg/ha in wheat crop and BYDV can be controlled mainly by the use of plant lines that are tolerant or resistant to certain BYDV isolates. The resistance or tolerant wheat varieties and insect vector management will enhance the yield of wheat crop in Pakistan and. High yield will improve the farmer’s income and it can play a significant role in the GDP of the country.

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