The 21st century is called biotech century. There is a prospect for agriculture to use the biological tools to produce all the desired needs through plant biotechnology. Most major crops are now being genetically produced. Corn, wheat, rice, potato, soyabean, sunflower, oilseed rape, cotton and tomato. Plant tissue culture is a collective term for protoplast, cell, tissue and organ cultures raised under controlled environment on artificial nutrient medium. Micro-propagation or tissue culture multiplication has developed into a preferred method of cloning and bulking. Tissue culture techniques are being exploited to enhance crop production and to aid crop improvement efforts. Faster clonal multiplication is being exploited on commercial scale for many horticultural species e.g. oil palm, mentha, roses, carnation etc. Tissue cultured somatic tissues are now routinely being used for conservation of those species whose seeds are recalcitrant or ones which do not produce seed at all. The most popular and widely commercialized global application of Plant Biotechnology is Micropropagation. Demand for high quality planting stock of crops such as banana, sugarcane, cardamom etc. Micropopagatin is the most commercially exploited area of plant tissue culture. Currently several genera and species encompassing the gamut of horticultural important crops are being propagated in millions and commercialized. The extensively micro propagated plants include a large number of foliage ornamentals, cut flower planting stocks and fruit yielding and agro-forestry species. However, there are quite a few important tropical fruit and tree species such as mango, litchi, coconut etc., which have remained recalcitrant. Plants are regenerated mainly through a sequence of side branch (adventitious shoot) formation, using a variety of tissues as explants i.e., initiation plant piece or by enhancing axillary branching in culture shoot tips. Eventually the shoot lets in both instances are rooted either in the laboratory- in vitro or outs controlled environment greenhouses. Most rapid plant multiplication rates can be achieved through somatic cell embryogenesis. The use of bioreactors for developing somatic embryos on a large scale and subsequent germination promises to be a reality. Artificial Seeds and Somatic Embryogenesis Micropropagtion techniques can be especially useful in increasing propagates of a new sexual or somatic hybrid or a plant freed from pathogens or even in case of a genetically engineered plant. If the embryos formed by this means are enclosed in a skin like conventional seeds called 'encapsulation' in a suitable matrix would lead to the development of artificial seeds. Special delivery systems like fluid drilling will also need to be developed and perfected. Somatic embryogenesis or using vegetative plant part for plant propagation is useful in annual field crops and perennial trees. Seeds are formed by the fusion of the female ovule and the male pollen grains each containing half the genetic material. Each is said to be haploid while the seed is diploid. Triploid seeds have three haploid sets of genetic material. So the seeds of triploid plants are sterile and the plants must be propagated by other means like tissue culture. Triploid seeds is a common technique used by plants breeders and water melon has benefited greatly from this technique. Micropropagation technology on a commercial basis is available for the following crops. Asparagus, banana, bamboo, cardamom, coffee, ginger, grapes, jackfruit, neem, orchids, pineapple, rose, rhododendron, vanilla. The plants developed by using genetic engineering technology are known as transonic plants, now available in cotton, soybean, maize, tomato, etc. The biotechnological approaches are more successful in dictoy crops belonging to the genera Solanum Nicatiana, Petunia and Brassica rather than in monocotyledonous crops like wheat, rice, maize, etc. Some other successful results of gene transfer in dicot and monocot crop plants are now available in the foreign market for commercial cultivation are Bollguard cotton, New leaf potatoes with Bt gene, soybean with herbicidal resistance, savary tomatoes using antisense technique for polygalacturonase enzyme, Potato with high T.S.S, Bt corn resistant to European Corn borer, BT rice for stem borer resistance, and rice with chitinase gene for sheath blight resistance Today Genetically Modified (GM) products are available in seven countries: USA, Spain, France, Canada, Australia, Mexico and Argentina. In the US, which allowed transonic products just five years ago, they already accounted for 50% of all soyabean, corn and cotton acreage. |
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