CONSERVATION OF PLANT SPECIES IN SEED BANKS

Professor C Kameswara RaoFoundation for Biotechnology Awareness and Education
Bangalore 560 004, India pbtkrao@gmail.com.

There is a pressing need is for the conservation of crop genetic resources, but it is largely impractical to conserve the very large number of crop species and their wild relatives in their natural habitats.  A viable alternative is to conserve whole seed in Seed Banks.  The seeds are germinated to raise plants from them for use in crop improvement. 

The important role seed banks play in the conservation of crop genetic resources is now globally recognized.

Various techniques have been developed for preserving seed, retaining their viability for longer periods.  As temperature and humidity are very critical factors, cleaned seeds are stored at around -20o C, often using silica gel in the seed containers to reduce humidity.  Seeds may also be stored over liquid nitrogen around -186oC (cryopreservation), which maintains retains seed viability for very long periods. 

Seeds in the seed banks need to be protected from pests and pathogens while in storage, but the risk from seed borne pests and pathogens persists.

THE INTERNATIONAL SEED TREATY (IST)

The International Treaty on Plant Genetic Resources for Food and Agriculture of the United Nations (the International Seed Treaty, IST), in force since June 2004, is a comprehensive international agreement in harmony with Convention on Biological Diversity. IST aims at guaranteeing food security through the conservation, exchange and sustainable use of the world's plant genetic resources for food and agriculture.  It also ensures a fair and equitable benefit sharing arising from such use. Further, it recognizes Farmers’ Rights to a) free access to genetic resources, unrestricted by intellectual property rights; b) to be involved in relevant policy discussions and decision making; and c) to use, save, sell and exchange seeds, subject to national laws.

SEED BANKS

Seed banks can provide controlled plant material of high quality and genetic diversity for research, eliminating the need for expensive expeditions. 

There are several seed banks in different countries, at the national, regional and local levels.  Some of the best seed banks in the world are in Peru, Colombia, Syria, India, Ethiopia, and the Philippines. Most botanical gardens also have seed collections.

A number of other seed banks, some of them called ‘community seed banks’ have been operating for decades with high decibel propaganda.  These have been amassing seed collections in a haphazard manner and without any semblance of science in matters of collection, characterization, identification and preservation.  With the evaporation of the initial enthusiasm or motivating factors, the collections are forgotten.  Such hodgepodge attempts are resources for lobbyists and hobbyists to gain political mileage, rather than tools to promote conservation. 

To be of any use serving the objectives of conservation, seed banks with state of the art storage facilities should be established at the national and international levels  and all such banks should be networked so that material, knowledge and expertise on  particular crops is available on a global scale. 

The following are among the important international seed banking facilities:

a) The National Bureau of Plant Genetic Resources  (NBGPR), New Delhi, India: NBGPR has over 3.43 lakh samples of 2.47 lakh varieties of 1,256 species, which include about 28,000 accessions of wild relatives of various crops.

b) Seed Banks of Global Network of Agricultural Research Institutions:
Ten international agricultural research institutions, co-ordinated by the Consultative Group on International Agricultural Research (CGIAR), Washington, are focused on crops and have extensive seed collections for such crops as rice, maize, wheat, barley, millets, pulses, oil seeds, tuber crops, banana, tropical forage and fruits.  The collections in these seed banks are well documented and the institutions are networked among themselves and with several other institutions. 

c) The Millennium Seed Bank Project:
The Millennium Seed Bank Project (MSBP) at the Royal Botanic Garden, Kew, England, is one of the largest conservation projects.  MSBP’s 47 partner organizations in 17 countries intend to store 25 per cent of the world's plant species by 2020. The Seed Information Database (SID) at Kew is an ongoing compilation of seed characteristics and traits world wide, targeted at >24,000 species. 

d) The Svalbard Global Seed Vault:
0n February 26, 2008, the Svalbard Global Seed Vault (SGSV) opened near Longyearbyen (Norway), 600 miles from the North Pole.  SGSV is designed to hold 4.5 billion batches of seeds of the world’s main crops.

The SGSV is a glazed cave-like structure, drilled 500 ft below permafrost, in the middle of a frozen Arctic mountain topped with snow, with the goal to store and protect samples from every seed collection in the world, which will stay frozen.   An automated digital monitoring system controls temperature and humidity and provides high security. 

The SGSV is an insurance against natural disasters such as earthquakes and tsunamis, or deliberate attacks like bomb blasts or human errors such as nuclear disasters or failure of refrigeration that may erase the seeds of any important species in the other seed banks or in the wild, in the other countries.  Such seed can be re-established using seeds from SGSV.  

LONGEVITY OF SEED IN SEED BANKS

Any seed can imbibe water and swell, which is a mere physical process.  It may even germinate, and produce a short root, but longevity, the potential to develop into a plant is the most crucial factor in seed banking. 

The claims that 10,000 year old seed of sacred lotus, arctic lupine and date palm germinated and produced plants were challenged.  Systematic scientific dating of seed and production of plants from them has shown that the germinated date palm seed is about 2,000 yr old and the lotus is 1,200 yr old.  The other authenticated reports on seed longevity are Canna (600 yr), and species of Liparia, Leucospermum and Acacia (200 yr).   Samples of 110 yr old cereal and weed seeds, stored in sealed glass vials in Vienna, germinated.  These are very exceptional examples of long seed viability.   

Contemporary data indicate that willow seeds are viable for only a week.  The seeds of tropical rain forest trees have low viability.  Seeds of sugarcane, tea, and coco palm, have a life-span of up to a year. Rush seed was viable for seven years.

Data gathered from 13 worldwide seed-storage stations indicate that seeds of crops such as barley, corn, oats, potato, rice, soybean, and wheat, have half-lives between 3–13 yr, which means that in the period specific for each crop, seed viability comes down by 50 per cent.  Seeds with hard seed coats such as beans and soybean would be viable much longer than the cereals.  .

Seed banks should periodically check for pests and pathogens and test for seed viability, collect fresh samples from the plants obtained by germinating the old deteriorating samples.  Seed longevity can be maximized only in scientifically managed seed banks.  If the seed loses its longevity, seed banks become seed musea, though the DNA from the seed can be used in genetic engineering of crops. 

November 11, 2008

RELATED ARTICLES:
CONSERVATION OF PLANT GENETIC RESOURCES
CONSERVATION OF PLANT SPECIES IN GERMPLASM BANKS
CONSERVATION OF PLANT SPECIES IN DNA BANKS