In vitro conservation including rare and endangered plants, heritage plants and important agricultural plants

Abstract

Plant germplasm collection and its conservation are an integral part of ensuring the availability of plant genetic materials for present and future breeding programs of important horticultural and agricultural plant crops; preservation of rare and endangered species, and of heritage plants. This paper reviews current technologies and their implications for future research. The most efficient and economical means of germplasm preservation under normal circumstances is in the form of seeds. However, this kind of storage is not always feasible because: i) some plants do not produce seeds, therefore, they have to be propagated vegetatively ii) seeds remain viable only for a limited duration or are recalcitrant iii) seeds are heterozygous and, therefore, not suitable for maintaining true to type genotypes iv) seeds of certain species deteriorate rapidly due to seed born pathogens. To improve germplasm preservation of endangered species, elite genotypes which are multiplied on a large scale in production laboratories, and plant materials with special attributes, eg metabolite producing cell lines and genetically engineered material, various strategies have been investigated. They include slow growth techniques or medium-term conservation; simple freezing techniques for differentiated materials such as apices and embryos; and long-term conservation (liquid nitrogen, -196OC). This last technology allows us to store plant material without modification or alternation, protects it from contamination, and requires limited maintenance. There are a number of cryopreservation technologies: freezing, ultra rapid freezing, vitrification, encapsulation/dehydration and encapsulation/vitrification. Additional research is needed to investigate existing cryopreservation techniques on a large scale in a genebank context and to develop protocols for additional species. In this paper, all of the above issues are considered and future approaches discussed.