Dr. M.S. Swaminathan (1983) reviewed the scientific aspects of conservation. He suggested that the first step in conservation should be defining the categories of materials (plants/genes) for preservation and the major methods preserving them. He suggested that the following categories should be usually regarded as important.
1. Cultivated varieties in current use.
2. Obsolete cultivars.
3. Primitive cultivars or land races.
4. Wild species and weedy species closely related to cultivated varieties.
5. Wild species of potential value to man.
6. Special genetic stock developed by man.
The principle of any technology designed for Germplasm conservation should be to preserve the maximum possible genetic diversity of a particular plant or genetic stock for future use.
Diversity in plants is at the level of species, varieties and individuals. Special genetic stocks may include the material (mutant or breed lines with identified gene or gene combination) developed and used in ongoing breeding programme.
It has been estimated that the survival of approximately 9,000 wild species of plants is some way threatened and that the majority of these are from tropical regions. This further highlights the need for a positive approach to conservation of endangered plants.
When new cultivars replace the primitive or conventionally used agricultural crops, it becomes especially important that the crop be properly documented and conserved.
According to Swaminathan (1983) conservation methodologies can take the following three forms:
1. Entire biomass
2. In situ preservation
3. Ex situ preservation
Many ways are being suggested for preserving biodiversity,
1. No undisturbed land use.
2. Catalogues of genetic resources and national biological inventories be prepared.
3. Measures should be taken to reduce emission of green house gases and ozone destroying compounds. Some of them include following:
4. Effective measures for the conservation of biodiversity be developed and strengthened in all countries.
The details of these conservation methods made a separate sub-discipline of biodiversity studies called conservation biology. These techniques of conservation of biodiversity include:
1. In situ conservation
2. Ex situ conservation
Conservation of biodiversity can be achieved in a number of complementary ways. These methods, all of them falling within the broader concepts of gene banks