Plant Tissue Culture

                                      Introduction 

The conventional breeding methods are the most widely used for crop improvement. But in certain situations, these methods have to be supplemented with plant tissue culture techniques either to increase their efficiency or to be able to achieve the objective, which is not possible through the conventional methods. One example of each situation would illustrate the point. Production of pure lines or inbred involves six to seven generations of selling. Production of haploids through distant crosses or using pollen, anther or ovary culture, followed by chromosome doubling, reduces this time to two generations. This represents a saving of 4-6 years. The other example is the transfer of a useful bacterial gene say, cry (crystal protein) gene from Bacillus thuringiensis, into a plant cell and, ultimately, regeneration of whole plants containing and expressing this gene (transgenic plants). 

                                                                              

                                                                   

This can be achieved only by a combination of tissue culture and genetic engineering; none of the conventional breeding approaches can ever produce such a plant. The term tissue culture is commonly used in a very wide sense to include in vitro culture of plant cells, tissues as well as organs. But in a strict sense, tissue culture denotes the in vitro cultivation of plant cells in an unorganized mass, e.g., callus cultures. Another term, cell culture is used for in vitro culture of single or relatively small groups of plant cells, e.g., suspension cultures. But, in general, the term tissue culture is applied to both callus and suspension cultures, and cell culture is often used for callus culture as well. When organized structures like root tips, shoot tips, embryos, etc. are cultured in vitro to obtain their development as organized structures, it is called organ culture. In this book, plant tissue culture is used in its broad sense to denote aseptic in vitro culture of plant cells. tissues and organs.

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