New Corn May Improve Nutrition, Decrease Pollution

ABERDEEN, Idaho, Dec. 18--Corn kernels that hold less phytic acid, a natural compound, could mean more nutritious animal feed and less potential for water pollution from manure, a U.S. Department of Agriculture scientist said.

USDA's Agricultural Research Servicehas applied for patent protection on low-phytic-acid corn developed by ARS geneticist Victor Raboy. Under a cooperative research and development agreement with ARS, Pioneer Hi-Bred International Inc. has bred the trait into its own hybrids and is conducting tests. Commercial varieties may be only a few years away.

Without adequate phosphorus in the diet, people and one-stomached animals such as hogs and chickens can have a higher risk of stunted growth and broken bones, said Raboy, based at ARS' National Small Grains Germplasm Research Facility in Aberdeen, Idaho.

Corn, soybeans and other common feedstuffs have plenty of phosphorus. But "animals with one stomach--including swine, poultry, fish and people--can't absorb phosphorus from plant foods," he said. "That causes both a nutritional problem and an environmental problem, as the excreted, unused phosphorus can pollute lakes and streams." A story about Raboy's research appears in the December issue of ARS' Agricultural Research magazine.

Farmers apply animal waste to croplands as fertilizer--enough each year to fill railroad boxcars that would circle the earth according to University of Kentucky estimates. Rain and other runoff can carry phosphorus-containing soil to nearby lakes and streams. Algae thrive on the phosphorus, using up the water's oxygen and choking out other aquatic life.

Raboy's low-phytic-acid corn enables one-stomached animals to extract the grain's phosphorus--meeting their nutritional needs and thus excreting less of the nutrient. This could also reduce the need for producers to give their animals phosphorus supplements.

People rarely have a phosphorus deficiency, because meats, milk and nuts are rich in forms of the nutrient that people can use. But developing countries that depend on grain-based diets may find food applications for the research, Raboy said.

All the trouble seems to lie in the way plants store phosphorus. Instead of storing the mineral in its pure form, plants bind up phosphorus in the phytic acid compound. Animals with multiple stomachs, like cows and sheep, have enzymes that break down phytic acid into usable phosphorus. One-stomached animals lack the enzymes.

"We've isolated more than 20 mutations in corn, and others in rice and barley, that cause the plant to store phosphorus in its inorganic, usable form rather than as phytic acid," Raboy said.

"Some of the mutations reduce phytic acid by up to 95 percent, but at that level some seeds might not germinate or the plants may yield poorly," he said. "Our most promising mutant reduces phytic acid by two-thirds without reducing total phosphorus. So far we've found no problems with the seeds."

Preliminary tests by Pioneer indicate that the approach works.

"So far, the seeds seem to germinate well and in some cases have yielded as well as our original hybrid," said David Ertl, Pioneer's research manager.

In other tests at Pioneer, low-phytic-acid corn from experimental hybrids was fed to 300 chicks. Other chicks were fed normal commercial diets with a known amount of phosphorus supplementation.

"The experimental hybrid corn seems to be performing just as we hoped it would," Ertl said. Chicks fed the corn seemed to get adequate phosphorus for growth and development, and excreted less phosphorus in the manure, he noted.

Ertl estimates that a hybrid with the low-phytic-acid trait could be ready for commercial production in 2 to 3 years.

Scientific contact: Victor Raboy, USDA-ARS National Small Grains Germplasm Research Facility, P.O. Box 307, Aberdeen, Idaho 83210, phone (208) 397-4162; e-mail [email protected].