TECHNOLOGY AND PROSPECTS OF CRYOPRESERVATION OF GERMPLASM

Entire plants have recently been regenerated from frozen cultures of protoplasts, cells, tissues and organs and stored at super-low temperatures for various lengths of time. This suggests the possibility of utilizing cryogenic methods for the conservation of important and rare germplasm, especially of the vegetatively propagated plants, which at present do not have any satisfactory method for their preservation. In addition, the freeze preservation offers a number of significant uses and prospects; (i) tissue cultures often show chromosomal variations, nuclear and ploidy changes, and mutations. Such genetic variables and cell lines which do not occur in nature can be picked out, banked and used in response to research needs; (ii) to maintain a cell line, it has to be transferred to a fresh medium periodically; the freeze storage would suppress cell division and thus the need for subculturing is avoided; (iii) at super-low temperatures the cells are in a non-metabolic state, which delays or virtually stops the 'ageing' process, and thus the morphogenetic potential of cultures is retained; (iv) pathogen-free stocks could be frozen, revived and propagated when desired, this would be ideal for the international exchange of such materials; and (v) the freezing of pollen would solve some of the problems encountered with the incompatibility and pollen longevity. Ever increasing population pressures demand improving and evolving new cultivars. However, with this enthusiastic search for obtaining new plants, and rapid increase in their number, it is not only becoming difficult but at times impossible to maintain or preserve some of the stocks which at present, are not needed for breeding purposes. Thus, some of the germplasm which may not seem to be of importance today, but might be needed in future, is ignored or completely lost. Therefore it is for the purpose of preservation of materials which are threatened with extinction that 'Germplasm Banks' need to be established. It is envisaged that freeze storage and tissue cultures would be a meaningful tool in experimental biology and agricultural research for the preservation and international exchange of important and pathogen-free germplasm. © 1979 H. Veenman En Zonen B.V.