Secret of high-yield crop gene identified

SCIENTISTS IN Britain have identified and isolated the key plant gene that was at the heart of the "green revolution" in agriculture which has enabled many developing countries to feed themselves over the past 30 years.

The researchers have found the gene responsible for dwarfism in wheat, which enables the plant to divert its energy into improving grain yield at the expense of height.

Experiments have demonstrated that it is possible to transfer the gene to other species of plants, such as rice.

Nick Harberd, the research scientist who led the investigation at the John Innes Centre in Norwich, said it is well documented that dwarf varieties of rice and wheat produced by conventional breeding have higher yields than taller varieties. Shorter varieties of crops are also more weather resistant. "Isolating a single gene that controls plant height means we can now convert any locally adapted, low-yielding variety into a dwarf form and potentially increase its yield," Dr Harberd said.

During the Sixties and Seventies, improvements in agriculture in the developing world led to a dramatic increase in crop yields. Dwarf varieties played a major role in the doubling of the world wheat crop during that period.

The John Innes team identified the dwarfism genes in astudy on a species of weed called Arabidopsis, or thale cress, which is commonly used by plant scientists in laboratory experiments.

Research published in the journal Nature showed that the dwarfism gene is responsible for controlling the sensitivity of Arabidopsis to a plant growth hormone called gibberellin, and that a similar version of the gene is responsible for dwarfism in wheat.

Certain versions of the gene make the naturally produced gibberellin of the plant less effective, resulting in significantly shortened stems - enabling the plant's energy to be diverted into producing seeds, or grains in the case of wheat.

Although the scientists were able to prove they can transfer the same genes from Arabidopsis into rice plants to confer dwarfism, they have not been able to show whether the dwarf rice produces a higher yield.

The scientists believe there will be few risks attached to the transfer of the dwarfism gene between crops because the mutations have already been exploited by conventional plant breeders for many decades. "This gene has been tried and tested for more than 30 years and people have eaten bread made from this wheat without ill effects," Dr Harberd said.

However, this is unlikely to satisfy the sceptics. The Norfolk Genetic Information Network has already condemned the plans to use the gene for engineering new varieties of crops.

"There are substantial ways of increasing yields without the risk of crossing over the species barrier and the uncertainties over health and the environment," a spokesman said yesterday. "While large firms and multi-nationals, many of which will be exporting the crops, will be able to afford to utilise this technology, it will hit small farmers and push them further into poverty."