Tomorrow's coffee, straight from the freezer
Economic and technical arguments are winning over sceptics in the battle to use cryopreservation to safeguard the world's coffee diversity.
- Coffee beans germinating successfully after being frozen to -196 °C. Credit: Stéphane Dussert/IRD
There exists a curious irony in the world of coffee. To a coffee grower, farming for example in the highlands of Ethiopia, the lack of diversity among her coffee bushes must be set against the mind-boggling range of coffee and coffee products available to affluent consumers in developed countries. The endless menu of lattes, cappuccinos, frappes, espressos, Americanos and mochas is barely on the same planet as the coffee grower.
Globally then, coffee is big business. It is now the world's most valuable traded agricultural commodity, with an annual export value in excess of US$6.2 billion. Most coffee-producing countries are in the developing world, where coffee is grown predominantly by small-scale, often poor, farmers, to whom the coffee trade is vital for their livelihoods.
Of course, the success of the crop—and of the whole coffee industry built upon it—depends on the availability of diversity to enhance the genetic base of coffee. This is needed to provide resistance to pests and diseases such as coffee berry disease, coffee rust, fusarium wilt, bacterial blight, nematodes and major insect pests, as well as adaptation to abiotic stresses such as climate change and drought. And on top of all that, there is the drive to enhance the aroma and flavour.
In 1998 The State of the World's Plant Genetic Resources for Food and Agriculture, published by FAO, noted 21 000 accessions of coffee, and all this diversity has traditionally been conserved in field genebanks, which present real challenges in conservation and security. A single cyclone in Madagascar, for example, could destroy the unique field collections of Mascarocoffea species that are so important for delivering traits of low or zero caffeine. And that's not just speculation; a cyclone did destroy the coffee collection at Ilaka Est. Fortunately the collection was duplicated at another site on the island, Kianjavato, and only a few accessions were lost.
Across the world many field genebanks, not just coffee, are thought to be equally vulnerable as a result of environmental and economic factors, such as pests and diseases, weather, fire, vandalism, lack of funds and policy changes. For real security and future diversity, a new approach is needed.
Step forward cryopreservation. With this 'super-freezing' technique, living tissues are conserved at -196 °C in liquid nitrogen, to arrest the cells' metabolic activity. Carried out with the help of precise protocols, cryopreservation allows plant material to be stored without alteration or modification for a theoretically unlimited period of time.
Enthusiasts for the method point to the fact that cryopreserved plant cultures are stored in small spaces, are protected from contamination and require very little maintenance. While some species, such as banana, are increasingly well catered for in cryopreservation, until now there have been doubts about the practical delivery of coffee cryopreservation and about whether the economics of this approach stack up.
For the past 15 years or so, Bioversity and many of its partners have invested in the development and adoption of cryopreservation by researching, testing and documenting protocols; by training technicians and scientists; and by supporting the acquisition of equipment for cryopreservation. As part of this effort, a survey of genebank managers and cryopreservation specialists was carried out in 2006 to assess the obstacles. One fascinating result identified by the survey is a general belief that cryopreservation is expensive, even though very few studies have analyzed the actual costs and effectiveness of cryopreservation and even fewer have gone further to compare the costs with those of maintaining field genebanks.
A new study led by Ehsan Dulloo, a Bioversity scientist, focused on a comparison of costs in maintaining one of the world's largest field collections of coffee with those of establishing a coffee cryocollection at the Centro Agronómico Tropical de Investigación y Enseñ'anza (CATIE) in Costa Rica. Bottom line: cryopreservation costs less (in perpetuity per accession) than conservation in field genebanks. A comparative analysis of the costs of both methods showed that the more accessions there are in cryopreservation storage, the lower the per-accession cost.
The team's calculations show the initial cost for the establishment for a cryocollection with 2000 accessions (US$110 055 or US$55 per accession) is less than that of a field collection of some 1992 accessions (US$138 681 or US$69.62 per accession). These figures are in the same cost range (US$50–75) as that reported by others—such as the USDA for the establishment of a cryopreserved temperate fruit collection at Corvallis on the US west coast.
A vital partner in the work was the Institut de recherche pour la développement in France, Dulloo noted. The cryopreservation technique was developed by IRD in the framework of joint projects with Bioversity and CATIE, and the beauty of the protocol is that it allows the cryopreservation of whole seeds. "Most cryopreservation conserves parts of the plant, like cells or just the growing tip, and these then need to be grown into whole plants to regenerate the collection. Cryopreservation of whole seed makes regeneration very easy and much less expensive," Dulloo explained. IRD's experience also enabled the detailed cost calculations of the project.
To keep those costs to a minimum in future, the solution may well be a regional or global cryopreserved collection for coffee germplasm (as demonstrated by other crops such as Musa). This would allow the costs of cryopreservation and the benefits derived from germplasm conservation to be shared amongst partner countries.
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