Physics meets biology in a project to breed better strains of rice.
物理学与生物学的碰撞--优质大米培植。
THOSE who turn their noses up at "genetically modified" food seldom seem to consider that allcrops are genetically modified. The difference between a wild plant and one that serves somehuman end is a lot of selective breeding-the picking and combining over the years of mutations thatresult in bigger seeds, tastier fruit or whatever else is required.
Nor, these days, are those mutations there by accident. They are, rather, deliberately induced,usually by exposing seeds to radiation. And that is exactly what Tomoko Abe and her colleagues atthe Riken Nishina Centre for Accelerator-Based Science in Saitama, outside Tokyo, are doing withrice. The difference is that Dr Abe is not using namby-pamby X-rays and gamma rays to mutate hercrop, as is the way in most other countries. Instead she is sticking them in a particle accelerator andbombarding them with heavy ions-large atoms that have been stripped down to their nuclei by theremoval of their electrons. This produces between ten and 100 times as many mutations as thetraditional method, and thus increases the chances of blundering across some useful ones.
Dr Abe's plan is to use these mutations to create salt-tolerant rice. She has tried to do that severaltimes in the past, but the result did not taste very nice. Her latest effort was stimulated by theflooding with seawater of almost 24,000 hectares of farmland by the tsunami which followed anearthquake in March last year. Salt-tolerant rice would, though, be of much wider use than justrestoring the paddies of Miyagi prefecture and its neighbours, the worst-affected part of thecountry, to full productivity. About a third of the world's rice paddies have salt problems, and yieldsin such briny fields may be half what they would be if the water in them were fresh.
To induce the mutations, Dr Abe bombarded germinating seeds with carbon ions for 30 seconds.She then planted them in fields in Miyagi. Of 600 seeds that have undergone this treatment, 250thrived and themselves produced healthy seeds.
The next stage of the project, to be carried out this month, is to take 50 grains from each of thesuccessful plants and repeat the process with them. The resulting specimens will then be sorted andthe best (ie, those that have flourished in the saline soils of Miyagi's paddies) selected forcrossbreeding, in order to concentrate desirable mutations into reproducible lines of plants.
The result, Dr Abe hopes, will be a viable salt-tolerant strain that is ready for market within fouryears. With luck, this time, it will be a tasty one as well.