The work, by scientists at the Beijing Institute of Genomics, builds on breakthrough research by teams from the same institute and the University of Washington Genome Center, that in 2002 mapped the rice genome in 2002. The first complete genome sequencing of a crop plant.
Rice is the staple food for over half of the world's population. Projections from the UN-backed Food and Agriculture Organisation (FAO) show that by 2030, total demand for rice will be 38 per cent higher than the annual amounts produced between 1997 and 1999.
In order to meet future demand, new methodologies and production technologies will be necessary as land and water resources become increasingly under threat.
Scientists are hopeful that an improved understanding of the genome could significantly contribute to nutritional and supply problems.
Researchers, led by the Beijing Institute of Genomics, claim this week to have published a 'much improved', near-complete genome analysis of the indica, the most common type of rice grown in China, and japonica subspecies of Oryza sativa, which are eaten in India and China, and Japan, respectively.
"Now the challenge is to use the rice sequences as a basis for detailed genetic analyses of additional cereal crops and for the development of improved strains of not only rice, but wheat, maize, and other important food crops" they write this week at PLoS Biology. The analysis team, led by Gane Ka-Shu Wong, believe their findings provide important insights into the evolution of rice.
The key to the improvement in the genome sequence analysis is that the researchers have used the combined DNA sequence data from the two subspecies to facilitate the sequence assembly.
The result is a nearly 1,000-fold increase in contiguity for the two genome sequences relative to the existing sequence data, write the researchers.
They used the improved genome sequence to investigate the evolutionary history of rice. Wong and colleagues report that there is evidence in the rice DNA sequences for a whole-genome duplication event just before the grasses diverged from other flowering plants, about 55-70 million years ago.
This genome duplication may have played a role in the origin of the grasses, which then spread rapidly across the world to provide important sources of food that, among other things, possibly influenced human evolution, they claim.
Analysis of the rice genomes also indicates that there is massive ongoing duplication of individual genes.
"These individual gene duplications provide a continuous source of raw material for gene genesis and very likely contribute to the differences between members of the grass family," state the gene sequencers.
The US department of agriculture predicts global production of rice to reach 401.8 million tons (milled basis) in 2004/05, up 10.8 million tons from 2003/04.