Abstract

Plant genetic resources are essential for agri-food security in the world and conservation of genetic diversity. Cryopreservation is an in vitro culture technique used for long-term plant conservation, by freezing the tissue at low temperatures usually with liquid nitrogen (-196ºC). During cryopreservation, cell division and metabolic activity of the explants are quiescent. There are different cryopreservation techniques used for many species and recently it has been observed that the use of aluminum cryoplates or foils increase plant survival and regeneration. The explants are exposed to a lot of stress in the different stages of cryopreservation, especially during chemical or physical dehydration and during thawing. Cryopreserved plants are exposed to physical, chemical and physiological cell damage and oxidative stress. The principal cause of plant cell mortality is membrane rupture due to ice crystal formation. The cryoprotective substances prevent ice formation and optimal dehydration is necessary for plant survival and regeneration. Different cryopreservation stages could alter genetic stability, especially during plant regeneration by the use of plant growth regulators. DNA alteration during in vitro culture depends on different factors, mainly cryopreservation technique and plant species. Molecular markers are used to detect variations in the DNA of cryopreserved plants. A successful cryopreservation protocol depends on survival, regeneration and genetic stability of plant materials.

Key words: Cryopreservation, plant genetic resources, cryogenic damage, plant regeneration, genetic stability.