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24 October 2007
The destruction in 2003 of Iraq’s Abu Gharib national genebank could have been a disaster for genetic resources conservation in an area where the ‘Fertile Crescent’ provided the cradle for domestication of cereal crops. The impact of this loss was, however, mitigated by the existence of a ‘black box’ collection at the International Center for Agricultural Research in the Dry Areas (ICARDA) in Aleppo, Syria, where seven years earlier Abu Gharib scientists had sent seeds of the 200 most valuable varieties for safe-keeping.
Nothing as dramatic is expected to occur to Bioversity’s International Musa Germplasm Collection held at the International Transit Centre (ITC) in Leuven, Belgium, but hoping for the best doesn’t preclude preparing for the worst. The ITC’s own black box collection will be housed at the French research institute for development, IRD, in Montpellier, where the first 96 accessions of bananas and plantains have recently arrived.
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Bart Panis (left) handing over the
96 accessions to Nicolas Roux. |
The samples had previously been ‘cryopreserved’ – that is put into a state of suspended animation in liquid nitrogen – by Bart Piette and Bart Panis, Belgian scientists at the Katholieke Universiteit Leuven (K.U.Leuven). Upon arrival at the IRD they were transferred to a 170-litre cryotank, in which the entire collection, some 1200 accessions, will eventually be duplicated. Unless something happens to the accessions in Belgium, the cryotank will remain closed except to check the level of liquid nitrogen. The advantage of cryopreserved plants is that they do not need regular care and, in principle, can be conserved for ever.
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IRD scientist Stephane Dussert, the caretaker of ITC’s black box collection. |
The IRD was chosen to house the black box collection because of the expertise of its scientists in cryopreservation. Developing protocols was one thing, deciding how many samples to cryopreserve was another, as IRD scientists realized when they started working on coffee. “At the time, there was no method to help genebank managers decide how many samples to cryopreserve”, recalls Stéphane Dussert, the IRD scientist who received the accessions from Bioversity’s Nicolas Roux.
Cryopreservation does not come with a guarantee that a thawed piece of tissue will regenerate into a fully viable plant. IRD scientists solved that problem by developing a method to calculate the number of samples needed to ensure a 95% probability that at least one of them will produce a plant. The method is based on the survival rate obtained for a given accession, the risk level set by the genebank manager and the interval, if any, at which the plants are scheduled to be regenerated.
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| Each cryotube contains 10-12 scalps or 10 meristems. |
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Having determined how many samples they needed to cryopreserve, the K.U.Leuven scientists repeated the process three times, at different times, to minimize the chance that all the samples are unknowingly contaminated. The plan is to put one of the repetitions of each accession in the black box collection in France and to keep the other two at the ITC in Belgium.
The 96 accessions sent to France fit in five 13 cm by 13 cm boxes that each contain 81 cryotubes. So far more than 500 accessions have been cryopreserved and are ready for transfer to the IRD. |
