April 2003
Genetic Resource Center personnel inspect shelves of rice germplasm in a genebank. Photo: International Rice Research Institute.
They sit, on shelves, in drawers, stacked in massive walk-in refrigerators. In paper bags, metal canisters, and aluminum foil pouches. Some live brief lives in glass test tubes under artificial lights. Others are all but immortal, bathed in liquid nitrogen at 196 degrees below freezing. A few take their chances in wide-open spaces.
They are the deposits in the world’s plant genebanks, living samples of the plants that humanity depends on, as precious as life itself. The simple word genebank covers many possibilities, from massive collections stored in elaborate buildings to a simple field of a few labeled plants. Genebanks are ex situ collections. That is, they comprise samples stored off site, away from the environments in which they naturally grow. The primary purpose of all genebanks is the safe conservation of plant diversity. For example:
- It may be the diversity of a single species and its wild relatives, for example the 100,000 or more samples of rice and its relatives, gathered from around the world and maintained by the International Rice Research Institute in the Philippines.
- Or it could be a small collection of a few locally important fruit trees, like those being assembled by schoolchildren in Sarawalk, Borneo.
It is impossible to say exactly when the world’s plant genetic resources collections began: people have been collecting and conserving plants in botanical gardens for many hundreds of years. The greatest pioneer of the modern era was the Russian Academician Nikolai Ivanovich Vavilov (1887-1943). In a series of extraordinary and intrepid expeditions, mainly between 1916 and 1933, Vavilov and his many disciples collected more than 250,000 plant accessions from around the world. Vavilov fell foul of Stalin’s regime but his name has long been properly honored in the N. I. Vavilov Institute of Plant Industry (VIR) in St Petersburg, which houses one of the world’s most important genebanks.
Today, the Food and Agriculture Organization of the United Nations’ (FAO) World Information and Early Warning System on Plant Genetic Resources (WIEWS) lists about
- 1,460 genebanks worldwide
- including 465 in Europe, 468 in the Americas, and 298 in Asia
Between them, the world’s genebanks maintain more than 5.4 million samples — although many are duplicates, so the total of genuinely distinct accessions is considerably lower.
How genebanks work
Our most valuable food crops — wheat, rice, and maize, which together provide all humanity with half the calories needed — produce seeds that are easy to store. So do many other prized crops. For genebanking,
- the seeds are merely cleaned, dried, and placed in a sealed jar or packet
- for medium term storage (20 to 30 years), the seeds are maintained at the modest temperature of 5°C
- for long-term storage (up to 100 years) they are kept at -18 to -20°C
Cool, dry seed should remain viable (capable of germination) for many years, and in some cases for decades or even centuries. But viability does decline over time, so the seed must be planted and grown out every few years to provide a fresh stock. The plants need to be cultivated carefully, and isolated so that they do not pick up pollen from any surrounding plants and so become genetically ‘polluted.’ All this is technically straightforward but, of course, adds to the expense of conservation.
With some plants, however, including some of the crops most important to people in developing countries, the technical problems are not so easy to solve.
- Many vital crops — among them potatoes, yams and cassava — are not generally propagated by seeds. Instead, farmers grow them from tubers or rhizomes or other storage organs. Potatoes, yams, cassava and others can reproduce sexually, as well, to produce true seed; but when they do, they shuffle their genes so that the potatoes or yams that grow from true seed are not genetically identical to the plants that produced them. The particular qualities of a particular variety are lost unless the tubers themselves are stored. Nature designed tubers to be storage organs, and although it is not technically difficult to keep them, albeit for the short term, tubers take up much more space than true seed and must, in general, be regenerated (replanted) much more often.
- Other plants raise even greater difficulties. Many cultivated bananas and plantains produce no seed at all — they are sexually sterile. And they do not produce natural storage organs either. They are propagated by some form of cutting or offshoot. Traditionally, farmers simply keep their preferred varieties of bananas and plantains in the field by propagating them year after year. Varieties can also be conserved as whole plants in field genebanks. But, if only for safety’s sake, keeping them ex situ is desirable, too. Although it is clearly a challenge to store plants that produce neither seed nor natural storage organs, the technical problems have largely been solved. Since the 1960s, it has been possible to keep plants in an in vitro genebank: cells are grown on a gel and fed with suitable nutrients and hormones to give rise to entire plants. In addition, it is becoming more and more possible to store cells for long periods by cryopreservation, a specialized form of freezing in liquid nitrogen at -196°C.
- Finally, a wide range of plants and particularly tropical trees produce seeds that are in various ways ‘recalcitrant.’ For example, the seeds of some tropical trees germinate while still on the parent: the ‘seed’ that drops to the ground is already a seedling. Recalcitrant seeds cannot be stored simply by drying and cooling. Indeed, they regard such treatments as a severe insult and quickly die. They require more sophisticated methods, which to a large extent must be tailored individually to their needs. The special problems associated with conserving these species adds to the expense.
Why are genebanks so important?
One reason to conserve crop diversity in genebanks is that crops are under threat elsewhere. Habitats continue to be destroyed by unsustainable human activity, and along with the habitats go the plants. One of the threats to diversity is advanced agriculture. As new varieties become available, and are taken up by farmers because they offer genuine benefits, they may displace the diversity that was there before. This is especially ironic because all advanced breeding is built on existing diversity, which makes it imperative that this diversity be conserved and remains available somewhere.
There are many, many instances of breeders finding the solution to some problem besetting agriculture in a genebank. One example: the Hessian fly is an insect pest that can devastate wheat crops worldwide. Estimates of the cost of damage vary widely.
- In one year, wheat farmers in the United States lost an estimated $100 million.
- In Morocco, a hotspot for Hessian fly attacks, damage costs total more than $300 million a year, which the country can ill afford.
Resistant varieties can reduce the damage to less than 1%. To create them, breeders in the U.S. and Syria explored samples of wheat and its relatives held in genebanks. They found 15 new sources of resistance, and used them to generate new resistant varieties of wheat that help farmers in Morocco, the U.S., and everywhere else that the Hessian fly is a problem.
Meeting the needs of breeders is thus one important function of genebanks. But increasingly genebanks are fulfilling additional roles. In the aftermath of disaster, natural and human, they are a repository not only of the seeds farmers need, but also of essential skills and knowledge. Take the case of Rwanda:
Seeds of Hope was a coalition of 16 international and 9 national research centres, which moved in to help restore agriculture after the end of the genocide in Rwanda. At one point in 1994, when the war escalated, 800,000 people were killed and another 2,000,000 displaced in just two months.
Agriculture, the occupation of more than 90% of the Rwandan people, was acutely affected, with the disruptions peaking at the height of the growing season. The world worried about the loss of the harvest, estimated at 60%, and the hunger that would follow.
But concern also focused on the risk to one of Rwanda’s unique national treasures: the diversity of its beans. Rwandans grew the greatest range of varieties anywhere in the world: at least 600 different types in a country no larger than Switzerland. In their genebanks, some members of the Seeds of Hope consortium held collections of Rwandan bean varieties. Among many other activities, Seeds of Hope prepared to restore crop varieties to the farmers from whom it had been collected in the first place. The consortium multiplied 1.5 tons of seed of more than 275 different varieties.
The experiences in Rwanda have guided more recent efforts to restore agriculture, for example in Afghanistan. After war and the worst drought in 40 years, a new consortium was established to supply seeds and know-how. Much of the seed came from genebanks holding varieties collected in Afghanistan. Genebanks are now an important component of the response to wars, hurricanes, drought, and disaster.
Genebanks are also finding a role in improving the livelihoods of poor farmers directly. Diversity is one of farmers’ great strategies for survival. Farmers who grow a diversity of species buffer themselves against a disaster that destroys one species. And a diversity of varieties of a single species makes better use of different environmental conditions. Having sometimes lost their local varieties, for example after adopting new and improved crops, farmers can turn to genebanks for new material to try. This has been a factor in the spread of better varieties of taro, a starchy root crop that is also grown for its leaves, across the many small island states of the Pacific. Genebanks have organized diversity fairs at which farmers gather to exchange varieties and the know-how associated with them.
All is not well
On the face of it, the state of the world’s collection of crop plant genes seems encouraging. Growth has been rapid over the past two decades (there were only about 54 genebanks worldwide at the end of the 1970s) and the total number of accessions under conservation, which runs into millions, seems impressive. But there are major gaps in the present collections, particularly among crops that need to be stored as tubers, such as cassava. Furthermore, many existing genebanks fall short of world standards for genebank management.
Ideally, genebanks should meet three criteria — they should be able to:
- store accessions over the long term
- duplicate and regenerate the material as required
- have the capacity to document and store information about the plant material in the collections
However, in 1998:
- 75 countries said they had facilities to store seed in the medium or long term — but fewer than half (35) of these were able to meet agreed-upon international management standards.
- The rest reported a lack of facilities for drying seeds, problems in maintaining equipment, and unreliable power supplies.
- Another 56 countries said that their facilities were suitable only for short to medium-term storage.
In short, the world’s most important agricultural asset is nowhere as secure as it should be. The work needed to conserve plant diversity must be given assured and unassailable financial underpinning forever. Unfortunately, this has proven politically difficult. Support for long-term caretaker activities can be precarious and difficult to justify, especially from a narrow-minded and short-term economic standpoint. Yet when it comes to rebuilding a shattered country’s economic base, or when a single sample among 50,000 contains exactly the traits that farmers need, the value of genebanks is almost literally impossible to calculate. From that point of view, genebanks are like an insurance policy for the future of agriculture, and that is part of the problem. When times are hard, skimping on insurance can seem a good idea. Indeed, some people choose not to insure their possessions at all. That may be fine if their possessions are easily replaced and their children have no expectations. But crop diversity, once lost, is impossible to replace.
Fortunately, countries have come together under the Food and Agriculture Organization of the United Nations (FAO) to endorse a plan to create an endowment, the Global Conservation Trust, which provides a permanent source of funding support for the precious deposits of diversity held in genebanks. Funding for the endowment is still needed, but the Trust has at least made a start at protecting the genebanks that protect our future.
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