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Chinese Scientists Discover New Yield-Boosting Rice Gene - 2003-04-10


Chinese scientists have discovered a gene in rice that they hope could increase each plant's yield, if manipulated in the right way. Boosting yield means many more grains per plant at the same cost for a rice-hungry world.

Rice-breeders are constantly seeking ways to increase the output of a cereal grain that feeds more than half the world's population. The gene discovery by researchers at the Chinese Academy of Sciences in Beijing holds the promise of doing that.

Genes are molecules in cells that determine the structure of living things. They produce proteins that carry out basic biological functions.

The gene the Chinese scientists have found controls the number of a rice plant's branches, called tillers, where the grain buds grow. Their research shows that it also regulates the formation of the buds themselves. Plant geneticist Li Jiayang says the gene is therefore important to the number of grains per plant.

Mr. Li says the number of branches a rice plant has controls its yield. He points out that understanding the biological mechanism regulating such branching will help breeders develop new high-yield rice varieties.

Mr. Li and his colleagues report in the journal Nature that an abnormal version of the gene results in a rice plant stem without branches or buds. When the scientists grew several varieties with the normal gene, the ones that had the most protein from the gene produced two to three times more grain-bearing branches than their wild cousins. They were also shorter, meaning that the plants put more energy into growing more branches and less into growing stem.

An American rice geneticist, Susan McCouch of Cornell University, calls the discovery critical to boosting rice yields.

"Sometimes, rice plants produce more leaf and stem tissue than is needed to carry the grain that we ultimately call yield," she said. "So what we would really like to do is figure out genetically how to adjust the way a rice plant allocates its resources, and to produce more grains, not necessarily on a per plant basis, but certainly on a per hectare basis."

But boosting rice yield is not merely a matter of increasing the number of branches a plant has. Mr. Li says that a plant with the most branches does not necessarily produce the most grains.

The Chinese researcher says the important thing is to produce just the right number of branches per plant. Only some optimum number can give the highest rice yield.

It is too early to tell whether this gene discovery will be as important to rice yield as the development of a dwarf variety in the 1960s, which, in addition to a new dwarf wheat, helped launch the so-called Green Revolution in grain production.

Researchers have a lot of work ahead of them to determine what other genes this one controls, what proteins they produce, and how to make them produce the optimum number of branches. But Mr. Li says the finding opens a window onto the process.

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