Scientists suppress gene that limits rice grain size

PUBLISHED : Thursday, 12 April, 2007, 12:00am
UPDATED : Thursday, 12 April, 2007, 12:00am

Mainland scientists have successfully identified and suppressed a rice gene, thereby boosting the weight of hybrid rice grains by half.

Researchers at the National Laboratory of Plant Molecular Genetics identified a previously unknown gene responsible for limiting a grain's size and weight and, with the help of conventional crossbreeding, reduced the gene's dominance to increase grain weight by 49.8 per cent. Research team leader Lin Hongxuan said the method was not transgenic, and therefore was safe for consumption.

Professor Lin said the gene, known as GW2, could be altered or even eliminated using existing genetic engineering tools, but this would result in a new species that could take years to be approved.

China has not endorsed commercialised production of any transgenic plants since 1999 and few of the crops in mainland fields today have undergone genetic re-engineering.

'We singled out the gene from existing large-grain species and cloned it into lesser ones,' Professor Lin said.

'We crossbred the cloned species several times to obtain new varieties with grains larger than the original. The method is called hybridisation. It is natural. It does not create a genetically altered species.'

He said that although the technique resulted in heavier grains, each plant's total yield only increased by about 20 per cent.

'While the grain becomes larger and heavier, their quantity simultaneously decreases. Therefore, the total output of a plant does not increase by as much as the grain size.'

The professor said the grain's quantity was controlled by another gene, which they had also identified.

'We are also working on that gene. It is possible that we can bring both quantity and quality under control and produce species with higher yields.'

He said increasing rice output in the field was a complex and systematic project, and this work was only the first step.

He said the team could not predict whether output in the field would reflect the higher smaller-scale yields.

'Water, air and nutrition also contribute significantly to rice output. We cannot take care of hectares of rice paddies as we are taking care of the 25 plants we have in our laboratory. We need further experiments to confirm the actual application's result,' Professor Lin said.

The research is to be published in the next issue of top international journal Nature Genetics. A member of the journal's review panel said the Shanghai-based scientists' work had epoch-making significance.

Food for all

China's annual rice output in millions of tonnes, according to the Food and Agriculture Organisation: 185