As the first major cereal crop to be sequenced, the rice genome will also provide data to be used to improve a variety of grains with similar gene sequences, such as corn and wheat.

A genome is the collection of all genetic material, and a genome sequence is akin to a map.

"The publicly available, high-quality draft sequence of the rice genome is expected to trigger rapid progress in determining the function of genes in cereals," Japanese Prime Minister Junichiro Koizumi said at a ceremony celebrating the achievement.

"I am convinced that genome research will make far-reaching contributions to solving the constraints in sustainable food production and environmental problems," he said.

The consortium, the International Rice Genome Sequencing Project (IRGSP), is composed of scientists from 10 countries - Japan, the United States, China, Taiwan, South Korea, India, Thailand, France, the United Kingdom and Brazil.

Japan's National Institute of Agrobiological Sciences (NIAS) led the consortium and played a major role in the project, sequencing nearly 60 percent of the genome of japonica rice.

The United States sequenced about 18 percent of the genome, while China decoded about 10 percent.

Rice is the staple food for half the world's population and accounts for about 30 percent of the world's cereal production.

It has 46,000-55,000 genes, more than the estimated 30,000 genes in the human genome.

MORE ACCURATE DATA

The announcement came eight months after a Swiss company and Chinese scientists published a draft sequence of the rice genome.

In April, a team of researchers at the Beijing Genomics Institute in China and the University of Washington in Seattle cooperated with a team at Swiss agrochemical company Syngenta AG to release the two draft sequences.

Scientists at the Chinese institute sequenced the genome of indica, a strain of rice grown in tropical climates, while Syngenta sequenced japonica, grown in the cooler climates.

Japanese officials said the achievement by the private company had spurred discussions over whether the international consortium should continue the genome project.

But eventually they decided to keep going, as they were confident that their data were more accurate than the draft sequencing of rice genome declared by other groups.

Syngenta and the Chinese institute used a method called whole-genome shotgun sequencing. Under this method, a genome is fragmented into millions of tiny pieces, sequenced, then put back together by computers. The strategy is tricky but can save time.

The consortium adopted the hierarchical shotgun sequencing approach, under which rice genomic DNA was cut into small fragments consisting of 100,000-150,000 nucleotide base pairs and then cloned. The method led to 99.99 percent of accuracy.

Masaki Iwabuchi, the president of Japan's NIAS, said the rice genome sequence would serve as the basis for world scientists to discover new gene functions to improve crop yield and quality.

"It is very important to determine the functions of genes related to desirable traits, such as resistance to disease, low temperatures or unfavourable weather conditions," he said.

Traditionally, scientists cultivate crops of better quality by choosing plants with desirable traits and breeding them with one another, which takes many years to complete.

Identifying the responsible genes means the desirable traits can be bred in much more quickly.