CHINA - KABUL, May 5 (Reuters) - Scientists in China have identified a single gene that appears to control rice yield, as well as its height and flowering time, taking what may be a crucial step in global efforts to increase crop productivity.

In an article published in Nature Genetics, the researchers said they were able to pinpoint a single gene, Ghd7, which appears to determine all three traits.

Previous studies identified a region on chromosome 7 which seemed to be responsible, but they were not able to zero in on any specific gene.

"Our study shows that a single gene can control several traits with major effects. It can double the yield, determine flowering time and plant height," said Zhang Qifa of the Huazhong Agricultural University in Wuhan province in China.

"Previously, we thought we needed to change many genes to change rice yield, now we just need to manipulate a single gene to increase productivity," he told Reuters by telephone.

Zhang and his colleagues studied 19 rice varieties in Asia and found that plants that were shorter, had fewer grains per cluster of flowers, and flowered earlier were lacking in the gene Ghd7.

When the gene was restored, the scientists saw sharp changes of increased yields, a doubling of the time to flowering and a 67 percent increase in height.

The scientists also found five different versions of Ghd7.

"The most highly active versions were present in warmer regions, allowing rice plants to fully exploit light and temperature by delaying flowering and increasing yield. Less active or inactive versions were found in cooler regions, enabling rice to be cultivated in areas where the growing season is shorter," they wrote. (Reporting by Tan Ee Lyn; Editing by John Chalmers)