Seed Banks: A Resource for the Future
The preservation of plant germplasm in seedbanks, (or genebanks), is one the more useful techniques of ex situ conservation of wild plant species. Nature has installed a natural dormancy feature into seeds, which allows for their suspended preservation for long periods of time with little damage, provided the conditions are favorable. Banking dormant seeds enables us to keep genetically representative samples of rare and endangered plant species as a kind of "genetic insurance".
PRESERVING BIODIVERSITY: WHY STORE SEEDS?
The preservation of biodiversity and natural variation within species has become a global concern. Natural variation is essential to the evolutionary process and to long-term species survival. Genetic diversity ensures that no two members of a species or population are genetically identical, and that no individual carries all the possible trait variants in a particular species. The diversity within a species allows it to survive and adapt to new environments, new pests, and changing climates.
Genetic diversity among plant species has a significant impact on human life as well. For instance, many of our medicines have come from plants buried deep in the rain forests; we can only speculate as to what other useful plants may be out there. There are uncountable numbers of plant species that have yet to be identified, many of which could prove to benefit mankind in some way. The preservation of this remarkable diversity is therefore integral to human life. The plants must survive in order for their benefits to be discovered.
THE ROLE OF SEEDBANKING IN CONSERVATION
Though in situ conservation of plant species is the ultimate conservation strategy, its implimentation may not always be feasible. Habitat destruction of endangered and rare species requires ex situ conservation efforts to prevent extinction. Ex situ conservation can also provide a back-up measure to enhance in situ projects. Good conservation requires the establishment and maintenance of a balance between in situ and ex situ conservation.
Storing germplasm in seedbanks is both inexpensive and space efficient as an ex situ conservation method. It successfully allows for the preservation of large populations with minimal genetic erosion.
In addition to preserving endangered species, seed banks also offer good sources of plant material for research. Through seed banks, researchers can obtain access to rare and endangered species without disturbing or damaging natural populations
WHAT TYPES OF SEEDS CAN BE STORED?
When speaking about seedbank storage, it is important to distinguish between two types of seed.
Orthodox seeds are those seeds that can be dried to a low humidity and stored at low temperatures while remaining viable for many years. It is this type of seed that can be successfully stored in seedbanks.
Recalcitrant seeds are all seeds that cannot tolerate the low humidity and low temperature storage conditions required for seedbank storage. The development of alternative methods of seed preservation for this type of seed is needed to ensure that recalcitrant species are not excluded from long-term conservation efforts.
HOW ARE SEEDS STORED?
The techniques currently used for seedbanking wild plants were developed for the preservation of crop species by organizations such as the International Plant Genetic Resource Institute, and the Food and Agricultural Organization of the United Nations.
The general sequence for seed bank storage is as follows:
Collection
Seed preparation
Seed drying
Packaging
Storage
Periodic germination tests
Seed regeneration
Re-storage
The conditions for seed storage are specific to each species. In general, however, seeds are dried to a moisture content below 7%, sealed in a moisture proof container, and stored at a temperature of -18 degrees Celsius. The success of the preservation technique depends on the continual monitoring of viability and the regeneration and/or recollection when viability falls below an acceptable level. Research is currently under way to find new and improved techniques for seed preservation.
DOCUMENTATION
One of the challenges of seedbanking is the need for proper documentation at all stages. Many of the current genebanks around the world are not adequately documented. This gap in information means that the collections are not very useful to researchers and plant improvement/conservation programs.
The information required for proper documentation of banked plant accessions includes: taxonomic identity and status, the location and nature of the population from which the sample was taken, details of the collection procedure, and information on storage conditions and viability.
SEEDBANKS AROUND THE GLOBE
According to FAO World Information, there are approximately 6 million plant accessions in over 1300 genebanks around the world. Of the accessions stored, 60% are in long-term or medium -term facilities, 8% in short-term facilities, and the remainder are in field genebanks, or are stored via new techniques such as cryopreservation. Only 15% of all seedbanked plants are wild or weedy plants.
Link to Information about Kew Gardens' Millenium Seedbank Project
CHALLENGES FACING SEEDBANKS
Despite the success that seedbanks have had in preserving plant genetic resources, they currently face many challenges. The high number of recalcitrant species in the wild cannot be preserved in seedbanks by current methods, leaving conservation of these species a difficult task. Seedbanks also suffer from a lack of funding and resources. This often results in a backlog of species awaiting regeneration. The lack of comprehensive data and limited information accessibility results in uneven conservation among species; some are duplicated many times while others are not preserved at all. Seed banks need to improve on transfer of information and technology, as well as benefit sharing, in accordance with the Convention of Biological Diversity. The improvement of communication between seedbanking gardens and a more universal database of wild species seed banking would certainly be of benefit.
Link to Seedbank Reference List
The Natural Heritage Seed Bank Proposal
last revised: 7 December 1998
Author: Joanna Rieber
