CITRUS is the general name for a group of species and hybrids that includes Lemons, Oranges, Mandarins, Grapefruit, Pummelos and many others. Citrus fruits are the most valuable fruit crop in international trade. All of the numerous Citrus varieties are cultivated in subtropical or tropical regions. Grape fruits are evergreen trees and are usually found at around 5–6 metres (16–20 ft) tall, although they can reach 13–15 metres (43–49 ft). The leaves are dark green, long (up to 150 mm, or 6 inches) and thin. It produces 5 cm (2 in) white four-petaled flowers.
The fruit is yellow-orange skinned and largely an oblate spheroid; it ranges in diameter from 10–15 cm. The flesh is segmented and acidic, varying in colour depending on the cultivars, which include white, pink and red pulps of varying sweetness. The 1929 US Ruby Red (of the Red blush variety) has the first grapefruit patent. The fruit has become popular since the late 19th century; before that it was only grown as an ornamental plant. Pakistan introduces grape fruit in research center in 1945. But Pakistan has emerged as one of the leading producer of citrus fruits in the world.
The citrus fruit types, varying from kinnow (mandarin), oranges, lemon, lime and grapefruit grows primarily in plains of Punjab province, including Sargodha, Sahiwal, Faisalabd, Toba Tek Singh and in some areas of KPK including Nowshera, Khanpur and Palai (Swat). Pakistani grape fruit has a great demand in international market but a higher number of seeds are one big constraint with an average 12.2 seeds per berry as compared to 11.2 in musambi, 9.5 in feutral and 8.8 in succari. Seedless cultivars are preferred by the international consumers. Seedless variety of Washington Naval Orange and Marsh variety of grapefruit is developed in the US and the Citrus Research Centre in the University of California, Riverside is engaged in developing seedless grape fruit variety which may not be costly to import but could challenge our variety.
The horticulture scientists should develop seedless fruit to meet the future challenges. Research has, however, revealed that Europeans consider that max seeds cause stomach disorder as every seed of grape fruit has a specific chemical material that sometimes disturbs the stomach. Pakistan could enhance its exports of fresh fruit. Currently, Pakistan has only 25 per cent packable yield of fruit which is lowest in the world considering pack able ratio. Till date private sector is independently endeavoring to boost the Pakistani fruit. There are three main groups of grapefruit varieties, white, pink and red. The white Marsh or Marsh Seedless. The Red blush or Ruby Red is a red or pink variety which was developed from the Marsh and is primarily grown in Texas.
In the past few years “super red” varieties such as the Star Ruby and Rio Red have become more popular. Other red varieties are the Ruby Sweet (also called a Henderson or Ray) which is seedless with very dark red flesh, and the Flame.
The Americans have shown a preference for sweet grapefruit over tart or bitter fruit, the less acidic Melogold, Chironja , Oroblanco varieties - both crosses between the pummelo and the grapefruit are becoming more popular. Each has yellow skin and white meat. Morrison’s Seedless, ‘Henderson’ and ‘Ray’ for commercial purposes. ‘Rio Red’ is marketed under the name Rio Star. Shambar is an old seedless pigmented variety of grapefruit. White or pale yellow varieties include: Duncan, Marsh, Oroblanco, Goldens, Wheeney, Sweetie and Melogold. Few hybrids are New Zealand, cook tail, Rex union, smooth Flat Seville.
Most species of citrus do not start out seedless. Instead, these fruit trees are carefully bred and selected by horticulturalists and gardeners for several properties, including a lower number of seeds. Through breeding only trees that feature few seeds, the result is eventually a seedless variety. Once that variety is grown, future genetic variation is limited by grafting seedless-citrus branches onto existing trees.
This allows these grafted branches to produce seedless citrus fruit that is genetically identical to the parent plant. While seedless citrus are more palatable than their seeded cousins, seedless citrus fruit makes reproducing citrus trees from seed difficult, if not impossible.
Instead, new seedless fruit is obtained by grafting buds from existing seedless trees onto young trees, and through laboratories that grow seedless plant matter in a growing solution until viable, then plant it in a growing medium until the plant is a small sapling and can be transplanted to a grove.
The country needs to pay head to a very important sector which has the potential of fetching precious foreign exchange. There is a great need to concentrate in the area of technological improvement like tissue culture technique and genetic engineering, to enhance the production of seedless grapefruit. Furthermore, our production and export of the fruit have been increased overtime only due to increase in acreage and not due to improvement in technology. Therefore, we should also develop high-yielding and disease-resistant varieties through technological improvement. The need of the hour is that we should adopt new technology to meet international requirements. We should produce seedless citrus varieties; adopt scientific techniques to perform various marketing activities and to reduce post harvest losses.
The writers are associated with the Institute of Horticultural Sciences, University of Agricultural Faisalabad.
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