Use of biotechnologies for the conservation of plant biodiversity

In vitro techniques are very useful for conserving plant biodiversity, including (a) genetic resources of recalcitrant seed and vegetatively propagated species, (b) rare and endangered plant species and (c) biotechnology products such as elite genotypes and genetically engineered material. Explants from recalcitrant seed and vegetatively propagated species can be efficiently collected under field conditions using in vitro techniques. In vitro culture techniques ensure the production and rapid multiplication of disease-free material. Medium-term conservation is achieved by reducing growth of plant material, thus increasing intervals between subcultures. For long-term conservation, cryopreservation (liquid nitrogen, -196 degrees C) allows storing plant material without modification or alteration for extended periods, protected from contaminations and with limited maintenance. Slow growth storage protocols are routinely employed for a large number of species, including numerous endangered plants, from temperate and tropical origin. Cryopreservation is well advanced for vegetatively propagated species, and techniques are ready for large-scale experimentation in an increasing number of cases. Research is much less advanced for recalcitrant species due to their seed characteristics, viz., very high sensitivity to desiccation, structural complexity and heterogeneity in terms of developmental stage and water content at maturity. However, various technical approaches should be explored to develop cryopreservation techniques for a larger number of recalcitrant seed species. A range of analytical techniques are available, which allow understanding physical and biological processes taking place in explants during cryopreservation. These techniques are extremely useful to assist in the development of cryopreservation protocols. In comparison with crop species, only limited research has been performed on cryopreservation of rare and endangered species. Even though routine use of cryopreservation is still limited, an increasing number of examples where cryopreservation is used on a large scale can be found both in genebanks for crops and in botanical gardens for endangered species.