Plant gene may reduce need for fertilizer

NORWICH, England, June 26 (UPI) -- Rice, wheat and other key crops someday may be able to produce maximum yields without the aid of fertilizer, thanks to a newly discovered gene that normally helps cultivate friendly bacteria in legumes, British and Hungarian researchers report.

The researchers said releasing crops from their dependence on nitrogen-laden fertilizers could not only help fight world hunger but also make farming cheaper and less chemically damaging to the environment.


"Nitrogen is currently produced in an extremely energy demanding process, and the price of nitrogen fertilizer is developing proportionally with the price of oil," Martin Parniske, a geneticist at the Sainsbury Laboratory in Norwich, England, told United Press International. "The use of chemical nitrogen fertilizer is not only a pollution problem but also eats into our limited fossil fuel reserves and generates more greenhouse gases."

Parniske's team, plus another group, led by Gabriella Endre of the Institute of Genetics at the Hungarian Academy of Sciences, in Budapest, independently discovered a gene that allows legume plants such as peas and soy to breed helpful "nitrogen-fixing" bacteria. These organisms transform atmospheric nitrogen into a biologically workable form for use in DNA and proteins.


Most plants deplete nitrogen from the soil. Crop rotation patterns that require planting legumes every few years to replenish the soil are often necessary.

"Over the past 40 or so years, the huge increase in the application of nitrogen and phosphorus-containing fertilizers has increased crop production, but fertilizer runoff has also been responsible (for) the contamination of drinking water supplies worldwide," explained plant biologist Maria Harrison of the Noble Foundation in Ardmore, Okla.

Ever since plants emerged on land roughly 460 million years ago, they have maintained symbiotic relationships with fungi to help plants acquire phosphorus and other nutrients from the soil, Parniske explained. Endre's and Parniske's teams found the legumes' relatively new nitrogen-fixing legume-germ partnership -- only about 160 million years old -- is tied to an enzyme somehow genetically derived from the older symbiotic relationship.

Although nitrogen-fixing symbiosis is restricted to the few plants that make up the legume group, the ancient phosphate symbiosis is found in nearly every species in the plant kingdom. This suggests "relatively few genetic changes might be necessary to enable symbiosis with nitrogen-fixing bacteria on important crop plants," Parniske explained.

The two teams' share a goal of developing crops with nitrogen-fixing capabilities. "It's quite a long-term aim yet, but with collecting more and more information about the molecular background of the process and identifying the key genes we can get closer and closer," Endre said.


Geneticist Sharon Long, dean of humanities and sciences at Stanford University in Palo Alto, Calif., cautioned there are at least four or five other genes tied to symbiosis that remain to be discovered. "The gene identified here is necessary, but it is not sufficient. We do not yet know enough to say whether any one of the genes is more important than the others," she explained.

Endre's and Parniske's groups both described their research in the June 27 issue of the journal Nature.

(Reported by Charles Choi, UPI Science News, in New York.)

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