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Gene Conservation Banks OR Preservation of Plant Genetic Resources -

The need for a program for the conservation of plant genetic resources arises from the rapid changes occurring in modern agricultural practice. Primitive cultivars and wild relatives of crop plants constitute a pool of genetic diversity which is invaluable for future breeding programs. These have already led to replacement by new cultivars which encompass a much narrower range of genetic diversity.

As a result, there is a very real danger of future breeding being impeded by the shrinking genetic bases of some crops. Hence, storage of this sort of irreplaceable breeding material or germplasm (gene combina­tions available for breeding) and establishment of a centralized gene bank are the practical ways to solve these problems. Conventionally, germplasms are stored in the form of seeds because they occupy a relatively small space and can be stored for many years. But there are a number of important species, in particular root and tuber crops, which are normally propagated vegetatively.

These include potato, sweet potato, yam and cassava. So the conventional preservation method is not applicable to vegetatively propa­gated plants. On the other hand, the cost of maintaining a large proportion of the available genotype of these plants in nurseries or fields is very high and risk of plant loss due to disease or environmental hazards very real.It is now possible with modern tissue culture techniques to provide a germplasm storage procedure which uniquely combines the possibilities of disease elimination and rapid clonal multiplication.

In addition, the possibility of using liquid nitrogen freeze-storage techniques for the preservation of cell, tissue and apical meristem is under study. The advantages of this technique are that cell division and normal cellular reactions are totally arrested at the very low temperature of liquid nitrogen (-196° C), which means that there should be a high level of genetic stability and that the chemical reaction responsible for cellular damage will not occur. The plant materials can be stored in liquid nitrogen for the period desired. This technique could be particularly valuable for storage of any germplasm, which needs to be maintained in a clonal form.

This technique is known as cryopreservation or freeze preservation of the tissue or cell. It has already been shown to be successful with a range of cell cultures, e.g. carrot cell and sycamore suspension cells and meristem tips from a number of crop plants, including asparagus, tomato and potato. Plant tissue and meristems of such plants have been successfully recovered from liquid nitrogen and grown into normal, mature fertile plants.