5 April 2002
Could GM rice feed the world?
With the production of rice failing to keep up with population growth,
the mapping of the rice
The publication today of the full genetic recipe for the world's most
important food crop
Half of the people alive today rely on rice to provide them with 80 per
cent of their dietary
However, something happened in the 1990s to cast new doubts over this assumption. Scientists first began to detect the decline in rice production in Thailand and India, and then confirmed it by long-term field trials in the Philippines. The problem seemed complex. Intensive rice cropping damaged the delicate soils of the rice paddies; overwatering boosted production but led to a rise in salinity levels; and some new rice varieties simply reached their highest possible yields.
The rate of increase in rice production fell to less than half of what
it was in the previous
It was a straightforward, almost Malthusian problem. Unless rice production could be boosted, we were heading for a global famine on a scale that no-one could predict. "We'll need to increase current rice production from nearly 600 million tons annually to almost 800 million tons by the year 2025," says Nguu Nguyen, an agricultural officer at the FAO. And just to make things more difficult, it will have to be done using less land, labour, water and pesticides, or the increased yield will be unsustainable, says Nguyen.
If this sounds like mission-near-impossible, you'd be right. Past experience
Donald Kennedy, the editor of the journal Science,
which publishes the genome studies
The sentiment is matched by Gane Ka-Shu Wong, senior research scientist at the University of Washington's Genome Center, and a lead author on the Science study. "Rice is considered the model genome for all the cereal crops, such as maize, oats, wheat and barley. If you put all these cereal crops together, something like 80 per cent of all the calories consumed in the world come from genomes that are very similar to rice," explains Dr Wong.
Steven Briggs, from the Swiss-based agrochemicals firm Syngenta, agrees: "The genome map of rice is directly related to corn, wheat and barley and provides commercial opportunities for the improvement of all cereal crops the foundation for the world's food supply."
Dr Briggs was part of the Syngenta team that sequenced the japonica variety of rice, whereas Dr Wong worked alongside the Chinese scientists who decoded the DNA sequence of the indica strain. Combining the results of the two studies suggests that the rice plant possesses between 45,000 and 56,000 genes perhaps more than the estimated 30,000-40,000 human genes.
The apparent dearth of genes in the human genome belies its hidden complexity. Whereas most rice genes appear to be involved in producing a single protein, many human genes appear to be able to produce more than one by a genetic trick known as "alternate splicing".
"What is interesting about rice and other plants is that there is relatively little alternate splicing," says Dr Wong. "In the case of humans, it's like each gene is a Swiss army knife and you can do a lot of things with one knife. If you do not use a Swiss army knife, you have to carry a separate tool for everything."
A direct comparison between the human and rice genomes has resulted in another finding. "We have compared the genome map of rice to that of humans, and despite having eaten plants for millions of years, there is no evidence that dietary DNA from plants can be taken up into the DNA of humans. So a crop gene produced by biotechnology is unlikely to be acquired by livestock or humans," says Dr Briggs.
Comparing the rice genome with that of arabidopsis, a weed-like plant
that has become a
More interestingly, rice appears to share much in common with the other cereal crops, which had a common ancestor some 50 to 70 million years ago. Dr Briggs says that this is why Syngenta spent about $30m (£21m) decoding the rice genome. "We are working to improve mainly our varieties of maize and wheat using the rice genome," Dr Briggs says. "Because the organisation of the rice genome and the sequence of its genes is directly related to that of the other cereals, we are using it primarily for the purpose of improving those other cereals. We expect to see improvements both in yield and in quality of the grain produced by the application of the rice genome."
By decoding the genes of rice and other staple crops, scientists hope
to find new ways of
The "high-tech" solution to global food shortages is not,
however, universally accepted.
"In this sense, arguments as to whether different forms of agriculture
can 'feed the world' are