Until 10 years ago, cryopreservation protocols for plant tissues were mainly based on slow freezing in the presence of cryoprotective mixtures containing DMSO (dimthyl slphoxide), sugars, glycerol and/ or proline. Slow freezing results in a freeze-dehydration, leaving less water in the cells to form lethal ice crystals upon exposure to extreme low temperatures.
The germ plasm of numerous plant species, especially those of forest trees, some agricultural crops, and medicinal plants, is endangered and threatened with extinction. This depletion of germplasm pools and the shrinkage of naturally occurring genetic resources have caused international concern. Conventionally, the germplasm of plants is conserved through seeds, tubers, roots, corms, rhizomes, bulbs, cuttings, etc. However, the germ plasm of a number of trees and plantation crops (such as coconut, cocao, coffee, oil palm, rubber, mango, horse chestnut, etc. ) cannot be preserved since their seed are short-lived (recalcitrant). Likewise, germplasm of vegetatively propagated crops (such as potato and cassava) cannot be stored on a long term basis and has to be grown and multiplied periodically in nurseries and fields. The plants are thus exposed to unpredictable weather conditions and diseases, with the result that instances are known where entire genetic stocks are lost. Therefore, unconventional methods are being developed for the storage and international exchange of germplasm. For this purpose in vitro cultures have been employed, but they can only enable short-to medium term preservation; moreover, cell cultures upon repeated subculture undergo genetic erosion. In view of the recent developments in the in vitro induction of genetic variability through somaclonal variation, somatic hybridization, recombinant DNA technology, etc. , new methods need to be employed for the storage of desirable cultures. In this regard freeze preservation of cells in liquid nitrogen (-196 0q, like that of semen, enables long-term storage, theoretically, for an indefinite period of time.
Cryopreservation has proven to be an important tool for the storage and conservation of plant genetic resources. This book is a unique resource for plant scientists, providing more than 100 ready-to-use cryopreservation protocols for plant types from algae and bryophytes to a range of flowering plants. It includes techniques for diverse plant parts such as dormant buds, pollen, and apical meristems and for cell types such as suspension and callus cultures.
This anchor volume to the series Managing Global Genetic Resources examines the structure that underlies efforts to preserve genetic material, including the worldwide network of genetic collections; the role of biotechnology; and a host of issues that surround management and use. Among the topics explored are in situ versus ex situ conservation, management of very large collections of genetic material, problems of quarantine, the controversy over ownership or copyright of genetic material, and more.
Development of cryopreservation techniques. Importance of cryopreservation for the conservation of plant genetic resources. Fundamental aspects of cryopreservation. Cryopreservation techniques. Ongoing cryopreservation projects -- Research and its application. Current status of cryopreservation research and future perspectives of its application in national programmes.
Ex situ preservation of germplasm for higher plant species has been accom plished using either seeds or clones, but storage of these under typical condi tions does not provide the extreme longevities that are needed to minimize risk of loss. Costs of maintenance and regeneration of stocks are also high. Systems that provide virtually indefinite storage should supplement existing methods and it is within this context that cryopreservation is presented. The use of low temperature preservation was initially more a concern of medicine and animal breeding, and was expanded to plants in the 1970s. Sur vival after cryogenic exposure has now been demonstrated for diverse plant groups including algae, bryophytes, fungi and higher plants. If survival is com monplace, then the eventual application is a cryopreservation system, whereby cells, tissues and organs are held indefinitely for use, often in the unforeseen future. The increasing interest and capabilities for application could not have occurred at a more opportune time since expanding human populations have placed unprecedented pressures on plant diversity. This book emphasizes cry opreservation of higher plants and was initially driven by the concern for loss of diversity in crops and the recognized need that this diversity would be essential for continued improvement of the many plants used by society for food, health and shelter. The interest in cryopreservation has been expanded by conservationists and their concerns for retaining, as much as possible, the diversity of natural populations. The need for cryopreservation, thus, is well established.
This publication provides an approach by which conservationists can determine whether or not long-term seed storage is feasible for a particular species, i.e. whether or not that species shows orthodox seed storage behaviour, and provides advice on the implementation of the protocol, examples of ways in which the results from seed storage studies could be misinterpreted due to confounding factors, as well as several alternative approaches for estimating seed storage behaviour prior to carryng out actual investigations with the seeds. In particular, the latter section introduces the concept of a multicriteria approach for estimating seed storage behaviour.
