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Last Updated: Wednesday, 10 August 2005, 17:44 GMT 18:44 UK
Scientists complete rice genome
Paddy field, PA
The research will also help scientists understand other vital food crops
Scientists have unscrambled the genetic code of rice, a development that could help end hunger around the world, Nature magazine reports this week.

The blueprint will speed up the hunt for genes that improve productivity and guard against disease and pests.

In order to avoid shortages, rice yields must increase by 30% over the next 20 years, researchers say.

Scientists from 10 countries cooperated to work out how the 400 million "letters" of rice DNA are arranged.

By sequencing rice we sequenced all the other cereals to a certain extent
Rod Wing, University of Arizona

"Rice is a critically important crop, and this finished sequence represents a major milestone," said Robin Buell of The Institute for Genomic Research (TIGR). "We know the scientific community can use these data to develop new varieties of rice that deliver increased yields and grow in harsher conditions."

The publicly funded research will also help scientists understand other vital food crops. Rice is genetically similar to maize, wheat, barley, rye, sorghum and sugarcane. So understanding the genomes of these plants is now a small step away.

Increasing demand

"Rice is the Rosetta Stone for crop genomes," said Dr Buell. "We can use the rice genome as a base for genomic studies of cereals."

According to the United Nations, rice currently provides 20% of the world's dietary energy supply, while wheat supplies 19% and maize 5%.

Although rice represents 30% of global cereal production today, and production levels have doubled over the past 30 years, much more of the cereal will be needed in the future.

Current consumption trends suggest that about 4.6 billion people will be reliant on rice by the 2025. In addition, global warming may mean that rice is required to be more robust in the face of droughts.

Japan led the International Rice Genome Sequencing Project (IRGSP), which included teams from the US, the UK, China, India, Thailand, Brazil and France.

Disease control

The rice variety sequenced was the temperate subspecies Oryza sativa subspecies japonica, which is cultivated mainly in Japan, Korea, and the US.

It took seven years to complete the work and the results are already accelerating discovery. Scientists have used the sequence to identify genes that control fundamental processes, such as flowering.

Professor Rod Wing, PA
Professor Rod Wing helped unscramble the rice genome
Rice's similarity to barley has also helped researchers identify genes responsible for resistance to barley powdery mildew and stem rust, two major crop diseases.

"Now that we know where all the genes are, we try to associate them with certain traits," said Rod Wing of the University of Arizona. "The accurate, map-based sequence has already led to the identification of genes that confer important traits such as yield and demand for light during growth."

The researchers compared rice to the only other fully sequenced plant genome, Arabidopsis thaliana, or thale cress, a weed that is commonly used in laboratories.

They found that while 90% of thale cress proteins also occur in rice, only 71% of rice proteins also occur in thale cress. This suggests rice has many genes specific to itself, or cereals.

"By sequencing rice we sequenced all the other cereals to a certain extent," said Professor Wing.

"Many of the shared genes are in similar positions on the respective chromosomes, so when we assign a function to a given gene in rice, it is very likely that the corresponding gene in another cereal has the same or a similar function."

Separate projects run by private companies have previously announced sequences of rice DNA. The IRGSP describes its data as more complete and fully available in public databases.

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