نگهداری بذر برای آینده‌ای نامطمئن

AFarmers and plant breeders depend on variety. An old type of wheat that produces little grain may still carry resistance to a disease or tolerance of drought, and such traits can be bred into modern crops. To keep these options open, institutions around the world run genebanks, where seeds of crops and their wild relatives are stored. Yet genebanks are vulnerable too. A flood, a fire, a war or a broken freezer can destroy a collection that took decades to build, so a safety copy kept somewhere far away is valuable.

BThe best-known safety store is the Svalbard Global Seed Vault, which opened in 2008 on a remote Arctic archipelago roughly halfway between mainland Norway and the North Pole. Seeds arrive sealed in foil packages and are stored in chambers cut more than a hundred metres into a mountain. The vault is kept at minus eighteen degrees Celsius, and the surrounding permafrost would help to keep the seeds cold if the cooling equipment ever failed. Norway owns the building, but not the seeds. Under a "black box" arrangement, each genebank that sends samples keeps ownership of them, and only that genebank may take them out.

CThis system proved its value during the war in Syria. The International Center for Agricultural Research in the Dry Areas, known as ICARDA, had run an important genebank in the country, but the conflict forced it to close. Between 2015 and 2019, the centre withdrew its duplicate seeds from Svalbard and grew them again at new sites in Lebanon and Morocco. The episode showed that seeds held in cold storage as a backup can return to active use when the original collection can no longer be reached.

DSeed banks cannot protect every plant, however. Most seeds survive being dried and then frozen, the standard method used at the Millennium Seed Bank run by the Royal Botanic Gardens, Kew. Some species, though, produce seeds that die when they lose water, and botanists describe these as recalcitrant. Researchers at Kew have estimated that over a third of critically endangered plant species produce seeds of this kind. For such plants, scientists are testing cryopreservation, in which the embryo is removed from the seed and frozen in liquid nitrogen at far lower temperatures than those in conventional seed storage.