Cryopreservation and Germplasm Storage

Cryopreservation is defined as the viable freezing of biological material and their subsequent storage at ultra-low temperatures, preferably at that of liquid nitrogen. The development of cryopreservation strategy for plant cells and organs has followed the advances made with mammalian systems, albeit several decades later. Even for mammalian systems, the discovery of chemicals with cryoprotective properties was a significant step towards the development and refinement of cryopreservation technology. A major breakthrough in this context was the finding that glycerol was capable of protecting avian spermatozoa from freezing injury (Polge et al., 1949). This generated widespread enthusiasm and renewed interest among people interested in low temperature preservation in such fields as biology and medicine. Since the early 1950’s a number of low molecular weight neutral solutes have been identified as potential cryoprotectants, the most commonly recognized ones being dimethylsulfoxide (DMSO or Me2SO) and glycerol. Dimethylsulfox-ide, originally used to prevent freezing damage to human and bovine red blood cells and bull spermatozoa (Lovelock and Bishop, 1959), has become a universal cryoprotectant. In recent years, considerable progress has been made in the low temperature preservation of red cells and platelets, leucocytes, bone marrow cells, protozoa, and helminth parasites of man and animals, insects and their cells and microorganisms (Ashwood-Smith and Farrant, 1980). Despite all these advances, unlike plants, most attempts to preserve animal organs at ultra-low temperature have met with limited success.