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BIOTECHNOLGICAL APPROACHES IN PLANT BREEDING Biotechnology is the age-old technology of using biological tools for the th improvement of human life. The 20 century witnessed tremendous advancements in different areas of biotechnology like microbial technology, genetic engineering and in vitro culture technology. In vitro culture technology, molecular genetics and genetic engineering have contributed new and unique tools and techniques to plant breeding. APPLICATIONS OF IN VITRO CULTURE TECHNOLOGY IN PLANT BREEDING • In vitro culture is the culturing of cells, tissues and organs under aseptic laboratory conditions in culture media. The culture medium generally contains the macronutrients and other supplementary materials like micronutrients necessary for plant growth and materials like vitamins, amino acids, carbohydrates and growth regulators. • Plant parts known as explants are cultured in the nutrient medium. Explants may be roots, cotyledons, leaves, shoots apices, nodal segments, anthers, embryos etc. The explants are surface sterilized with disinfectants like sodium hypochlorite or mercuric chloride, washed with sterile water and cultured in the nutrient media at 25 ± 10℃. • Usually depending upon the nature of the explant, the nutrient medium and the hormonal combination, development of callus (an undifferentiated mass of tissue) or direct plantlets from the explant takes place within 3-4 weeks. APPLICATIONS OF IN VITRO CULTURE TECHNOLOGY IN PLANT BREEDING The callus is subcultured after every 3-4 weeks. The subcultured callus is made to differentiate and produce the shoot system and root system, by altering the composition of the culture medium. Somatic embryogenesis can also be attempted in callus culture. It is the development of embryo- like structures from cell culture. Such somatic embryos can be encapsulated in a suitable matrix like sodium alginate and synthetic seeds can be produced. Synthetic seeds can be stored for several years and used as natural seeds. The major applications of in vitro culture technology include micropropagation, somatic embryogenesis, exploitation of somaclonal variation, meristem culture, anther culture, pollen culture, embryo culture, protoplast culture, cryopreservation of germplasm, secondary metabolite production and in vitro mutagenesis from plant cell culture. MICROPROPAGATION This is the bulk production of clonal plants for rapid propagation. It is an important application of tissue culture technology in plant breeding. It is independent of seasonal and regional constraints. The plants produced in this way are true to type, i.e., they resemble parent plants. Rapid multiplication of planting materials of unique plants with disease resistance and good quality can be carried out by this technique. Uniform behavior of the clonal crop is highly advantageous in terms of agronomic and harvest practices. But the chances of susceptibility to new strains of pathogens and adverse environmental conditions are always associated with such genetically uniform crop populations.
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