In the 1970s 116000 hectares [448 square miles] of East Asian rice paddies were afflicted by grassy stunt virus, which destroyed the food crop. Scientists knew that they were facing a potential disaster, so they began to research to find a rice strain immune to the virus. Eventually they found one rice species, Oryza nivara, that was immune, and they began a long endeavour to cross the various strains of cultivated rice with Oryza. Eventually, they succeeded and the world's rice crop was saved. This shows the importance of identifying and preserving the wild relatives of food plants.
The problem at the moment is that the world gets eighty per cent of its calories from just twelve crops, and these have been selectively bred to such a degree that the gene pool has seriously narrowed. Over-reliance on a narrow gene pool is very dangerous,for if a major virus wipes out one of these twelve, mass starvation would result. Here is where wild relatives become important. Out there in nature, quite often in isolated places, live species with unique genetic signatures,maybe possessing immunity to dangerous plant diseases or to the kind of conditions that we will increasingly face with global warming. Unlike the cultivated varieties, which have been grown in the narrow context of the laboratory and the farm, wild relatives have evolved to meet a wide range of conditions and have thus developed genetic mutations that may be useful to growers. Science is driven now by an urgent need to identify and genetically sequence these plants.
Take the case of the carrot.Many people do not realise that the orange carrot is just one group of varieties and that there are white, red, black, purple and yellow carrots. But this is without taking into account that there are several carrot species, each of which has some genetic variation in its genome. Scientists realised that with global warming, impending water shortages and the increasing salinification of certain lands, carrot crops may well be under threat, so they searched for the wild relatives and found several species that are resistant to water shortage and saline conditions. Seeds were collected and then the next stage of scientific work began .
The Millennium Seed Bank [MSB] was working with scientists from Pakistan and Bangla Desh, countries likely to be afflicted by destruction of carrot crops. Together they worked to map the location of these desirable species and then the MSB sequenced the entire carrot genome to identify the genes that made for resistance to drought and salinity. They are now in the stage of propagating the seeds and cross-breeding them with other varieties. The resulting carrots were also tested for palatability, important in a food crop. A database was then developed and made available to scientists. This pre-testing is prior to the seeds being returned to Bangla Desh and Pakistan for testing in the field, which allows scientists to ascertain whether there are any unforeseen problems.
The seedbank contains 2.2 billion seeds from 38000 species received from 190 countries. But despite these impressive numbers there is still work to do, especially with food crops, which have yet to be fully mapped and sequenced.