Yahoo News 5 May 08;
Researchers in China have pinpointed an elusive gene that plays a linchpin role in determining the harvest potential of rice, according to a study released on Sunday by the journal Nature Genetics.
The productivity of a rice plant is determined by several traits -- the number and size of its grains; the height of the plant; and its flowering time, which reflects its response to the prevailing climate.
Years of previous work in rice research have helped scientists close in on the plant's Chromosome 7 for a gene that appears to affect all three characteristics -- and this appears to be the magic sequence.
The gene was identified by a team led by Qifa Zhang of Huangzhong Agricultural University in Wuhan, in an arduous exploit of field research.
The team planted 30,000 rice plants in a bid to track down the gene.
This was winnowed down to 1,082 plants that had a tell-tale low yield, as they had fewer and smaller grains, were short and flowered earlier. The culprit was found to be the lack of a gene called Ghd7.
When Ghd7 was slotted into these lagging plants, the yield traits were transformed. The time taken to flowering doubled, and the plants became almost two-thirds taller.
The investigators then took a snapshot of how Ghd7 functioned in 19 different strains of rice that originate from around Asia, ranging from Japan in the north to the Philippines, Myanmar and India in the south.
They found five different mutations, or versions, of the key gene.
Less active, or inactive, versions of Ghd7 were found in rice grown in cooler regions.
These mutations encouraged the plant to flower earlier, thus enabling it to be cultivated in areas where there is a short growing season and a temperate climate.
In contrast, highly active versions of the gene were present in regions that have long growing seasons, with day-long warmth and exposure to light. These versions delayed flowering and increased yield.
The findings "have fundamental implications" for improving yields of rice, the staple food in Asia and an important dietary component in the rest of the world, says the study.
Rice technologists can help farmers by tweaking the Ghd7 gene and matching specific variants of it to the climate where the plants are to be grown, it says.
Boosting rice harvests is essential, given the rise in Earth's population from around 6.5 billion today to more than nine billion by mid-century.
The price of rice and other cereals has surged in the past year in response to drought in the United States and Australia, and to incentives to grow biofuels rather than food crops.
China experts identify gene for yield, height in rice
Yahoo News 4 May 08;
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)
