May 5 (Bloomberg) -- A rice gene capable of doubling crop yields may give plant researchers a breakthrough in their search for more productive varieties of the cereal that's a staple for at least half the world.

Varieties of rice with a particular gene grow taller, flower later and produce twice the number of grains as plants that lack the gene, given the same sunny conditions, researchers from Huazhong Agricultural University in Wuhan, China, said in a study published online in the journal Nature Genetics.

Governments are seeking higher-yielding rice varieties to secure supplies as prices jump to a record. Global demand for rice has increased 1.16 percent a year over the past decade, compared with production gains averaging 1.14 percent, according to U.S. Department of Agriculture statistics.

``This has really big implications for crop improvement,'' said Qifa Zhang, who participated in the study at the university's National Key Laboratory of Crop Genetic Improvement. Zhang and colleagues plan ``to see whether this gene could do anything to increase productivity of other crops,'' he said by phone yesterday.

Under conditions where rice plants with the so-called Ghd7 gene receive at least 14 hours of sunlight a day, such as tropical and sub-tropical regions, the gene delays flowering by as much as one month, allowing the plant to grow twice the number of grains, Zhang said. In more temperate areas where delayed flowering isn't desirable, such as northern China, plants adapt by switching off the gene, he said.

Handful of Genes

The research suggests a handful of genes may have a significant effect on traits including yield, height and the date of flowering, Zhang said. Scientists previously thought these factors were controlled by myriad genes, each playing a small part.

Zhang is part of the International Rice Functional Genomics Consortium, which aims to pinpoint the role of every rice gene. He's been working for more than nine years to develop a so-called green super-rice strain to help insulate low-income countries against shortfalls in rice production.

The price of rice on the Chicago Board of Trade has climbed 90 percent in the past year as farmers grew less of the cereal than is being consumed, and countries including India, China and Vietnam cut exports to safeguard local stockpiles and cool inflation. The price touched a record on April 24.

To contact the reporter on this story: Simeon Bennett in Singapore at sbennett9@bloomberg.net

Last Updated: May 4, 2008 23:44 EDT