THE genetic code of rice has been mapped in its entirety by an international team of scientists, paving the way for critical improvements in the crop that feeds more than half the world’s population.

The completed genome sequence was hailed yesterday as a “Rosetta Stone” for understanding rice and developing much-needed new varieties. It will also shed important light on the biology of other key cereals such as wheat, corn and millet. Full details of the 37,544 genes that make up the genome of the world’s most important food crop — compared with a human being’s 25,000 — will transform scientists’ ability to increase its yield and improve resistance against drought, pests and disease.

Rice is the staple foodstuff of more than three billion people, who rely on it for as much as 80 per cent of their diet. Agricultural researchers estimate that world production will have to rise by 30 per cent over the next two decades to feed the world’s growing population.

Armed with rice’s full genetic sequence, scientists will now be able to identify beneficial genes much more quickly and accurately, and develop strains with the most advantageous combinations. Genetic modification and traditional plant breeding will gain from the advance because each technique can be improved by the precision that comes with more complete understanding of a plant’s genome.

“This is a breakthrough of inestimable significance, not only for science and agriculture, but also for all those people who depend on rice as their primary dietary staple — more than half the world’s population,” said Joachim Messing of Rutgers University, in New Jersey, one of the consortium leaders. Rice is also closely related to all the world’s major cereal crops, which are all descended from a common, grass-like ancestor. Breeding and GM programmes for wheat, corn, barley, rye, sorghum, millet and sugar cane stand to benefit.

“The rice genome is the Rosetta Stone of all the bigger grass genomes,” Dr Messing said. “Knowing its sequence will provide instantaneous access to the same genes in the same relative physical position in other grasses, and accelerate plant gene discovery in many important crops.”

Claire Fraser, the president of the Institute of Genome Research, in Rockville, Maryland, said: “Much as the Human Genome Project has revolutionised biology, the rice genome promises to inspire new cereal crop research. This is a major step forward for agriculture.”

The completed genome sequence, which is published today in Nature, covers both the main strains of rice: the japonica and indica subspecies of the plant Oryza sativa. It builds on draft sequences of both strains, two of which were donated to the project by the biotechnology companies Syngenta and Monsanto. When Syngenta first published its draft of the japonica genome in 2002, it triggered protests from leading scientists by initially restricting access to its full data. All its information, however, is now in the public domain.

The International Rice Genome Sequencing Project brought together scientists from thirty-two institutions in ten countries, including a group at the John Innes Centre, in Norwich. The project has been completed three years ahead of schedule.

The finished sequence has already been used to identify genes that control fundamental processes, such as flowering. And the similarity of rice to barley has helped scientists to identify genes that protect the latter crop against two of its major diseases, barley powdery mildew and stem rust.

MAKING A MEAL

Consumption trends suggest that 4.6 billion people will be reliant on rice by 2025 compared with about 3 billion now. Production must rise by 20 per cent to meet demand

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