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Ashika Jaimangal
Genebank Curator & Researcher
Plant Breeding Division
ARC-Vegetable & Ornamental Plants
Private Bag X293, Pretoria, 0001
Tel: +27 (0)12 808 8000
(Internal: 068322)
Email:
jaimangala@arc.agric.za | | Over recent decades, the need for conservation of plant genetic resources has become increasingly urgent due to the rapid depletion in the total naturally occurring genetic diversity on Earth. Some of the factors contributing to the rapid rate of biodiversity loss include pollution; wildfires; overgrazing; spread of invasive alien species; over-exploitation and unsustainable harvesting of natural resources for food and medicine; poor land management and conversion of land for agriculture; industrialisation and other consequences of economic growth; and global climate change. These losses in biodiversity ultimately pose a severe threat to food security in the long term. In attempts to curb further biodiversity loss, many countries and institutions, including ARC-Roodeplaat, have established genebanks for conservation of their precious plant genetic resources. | |
ARC-VOP Genebank collections are categorised as follows: |
The core purpose of genebanks is conservation and management of genes or plant genotypes, from wild and cultivated species outside of their natural habitat, for current or future use. Although the germplasm of all species (that we can multiply) can theoretically be conserved in genebanks, traditionally genebanks have served as a repository for the germplasm of endangered species facing the threat of possible extinction, and for those forming the basis of human sustenance as a food source and for agricultural purposes. Nowadays, genebanks accommodate a range of materials including varieties from traditional agriculture i.e. landraces, primitive cultivars and species that are harvested for use in sacred rituals as part of certain cultural practises, superior cultivars, advanced lines, mutants and synthetic materials emerging from scientific improvement programmes, and even genetic fragments, cloned genes, marker genes and transgenic plants resulting from biotechnology and genetic engineering initiatives. Regardless of the type of material however, genebank curators generally follow a similar sequence of events beginning with acquisition of the germplasm, to preliminary multiplication of the acquired germplasm, to storage of specimens and finally, management of conserved germplasm.
Presently, seeds represent the easiest and most convenient means of storing genetic diversity and most national genebanks are largely dependent on cold storage facilities for maintenance of seed germplasm, generally at low temperature and moisture levels. The alternative i.e. storage of seeds in liquid nitrogen, or cryopreservation, is gathering growing interest from genebanks around the world for various reasons. Since optimum seed storage conditions in genebanks involve low temperatures and drying of seed material down to very low moisture levels, this method displays obvious shortcomings when dealing with seeds of numerous crop species, particularly tropical shrubs and trees for example many citrus species, rubber, oak, oil palm, cocoa, mango and coffee. The seeds of these species are referred to as "recalcitrant" since they cannot tolerate being dried down to any meaningful moisture level that would facilitate seed storage, and some are even chilling-sensitive (i.e. cannot survive low temperature storage). Germplasm storage for these recalcitrant-seeded species as well as for species that do not produce seed, is achieved by maintenance of so-called field genebanks (i.e. collections of living plants planted either in open fields or in glasshouses) or via in vitro conservation methods. The latter involves maintenance of explants in a sterile micro-environment, the conditions of which can be manipulated depending on whether short or medium-term storage of the germplasm is desirable. For long-term storage of genetic resources, cryopreservation still remains the only viable option.
ARC-VOP currently maintains ten genebanks consisting of germplasm collections of selected indigenous vegetables, commercial vegetables, indigenous flower bulbs, medicinal plants and cactus pear. The collection also includes gene- and gene constructs and mutant seeds as well as a collection of pests and diseases that are predominantly associated with crops of interest. Banked germplasms continue to be utilised by industry, private clients and to service the needs of researchers and breeders both internally and externally. In fact, the genebanks are the actual starting point of ninety percent of ARC-VOP research outputs. Although the role of genebanks in facilitating research is unquestionable, their role in primarily securing and maintaining the germplasm of a variety of plant, insect, fungi and bacteria species, as well as DNA and gene constructs related to vegetables, medicinal and ornamental plant species is invaluable.
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