April 4, 2002. Copyright 2002. Graphic News. All rights reserved.

Embargoed: Not for release until 14:00 U.S. ET (19:00GMT) Thursday, 04 April 4, 2002

Rice genome may help fight world hunger 

LONDON, April 4, Graphic News: Every day, 24,000 people die from hunger and related causes and about 800 million people worldwide do not have access to sufficient food to meet their daily nutritional needs. As the human population expands and farmland shrinks, food shortages -- brought on by war, drought, political unrest and poverty -- are expected to become increasingly acute.

Now, in an achievement that may help make new inroads on global hunger, researchers have announced in the journal Science that they have sequenced the genomes of two rice varieties. Indica and japonica are the major rice varieties planted around the world, and are a staple food for more than half the worldÕs population. 

Rice, the worldÕs number one food crop -- known scientifically as Oryza sativa -- provides 25 to 80 percent of the calories in the daily diet of some 2.7 billion Asians, or 45 percent of the worldÕs population.

The rice strain, indica, sequenced by Jun Yu of the Beijing Genomics Institute and the University of Washington Genome Center, with colleagues at 11 Chinese institutions, is a major subspecies in China and other Asian-Pacific regions. Crossing the indica strain with another variety produces a super-hybrid with a 20- to 30-percent higher yield per hectare than other rice crops. 

A second team, led by Stephen Goff and colleagues at the private Swiss-based Syngenta, studied the japonica, or Nipponbare subspecies, prevalent in more arid regions. Rice with higher vitamin content may result from the Syngenta research, said Goff. ÒThe japonica genome should reveal the gene responsible for Beta-carotene, which is converted in the walls of the intestine to Vitamin A. Genetic information about rice may also set the stage for hardier, more pest-resistant crops, and help improve the cerealÕs usefulness for brick construction, water filtration and various other uses,Ó he added.

Both teams used the Òwhole-genome shotgunÓ sequencing method (previously used to sequence the fruit fly genome, and by private researchers sequencing the human genome). Previously, the genomes of man and other animals, plants and fungi, known as eukaryotes, have been analysed using a laborious approach that sequences each chromosome a bit at a time. This is a lengthy affair, which helps to explain why only two other eukaryotes (yeast, and a small worm called C. elegans) have had their genomes fully sequenced. 

Whole-genome shotgunning, by contrast, involves shredding an organismÕs genetic material by chopping it up with enzymes, and then sequencing the pieces without knowing where they came from. If this is repeated five or six times then the DNA fragments, which break at randon, will overlap with one another. All you need then is a powerful computer program to match up the overlaps and reconstruct the original order of the base pairs.

The indica and japonica strains diverged from one another two to three million years ago. Rice was first cultivated in Asia around 7,000 years ago: more recently than Central American corn (9,000 years ago) and wheat in the Middle East (10,000 years ago). It was not until the 1960s with the so-called Green Revolution that pioneering work by plant breeders resulted in high-yield varieties of the three main cereal crops: corn, wheat and rice. Between 1967 and 1992 the world rice harvest doubled to more than 500 million tonnes per year.

Now to keep pace with AsiaÕs rising population, rice production must increase by an estimated 60 percent by 2020. The current dwarf varieties have 20 to 25 stalks, but only 15 yield pannicles -- the heavy tips of the stalks which each produce about 100 grains of rice.

The genome may help develop stronger, thicker stalks, all capable of producing pannicles with twice as many grains, and reduce the breeding time of conventional crossbreeding. The two draft sequences Òwill speed improvements in nutritional quality, crop yield and sustainable agriculture to meet the worldÕs growing needs,Ó said Donald Kennedy, editor-in-chief of Science.
/ENDS

Sources: Science, Amersham Biosciences, University of Michigan