For years, scientists have tried to develop a corn plant that can fix its own nitrogen, a la legumes.
Now, researchers at Southern Illinois University have come up with the next-best thing: a gene that lets corn utilize nitrogen fertilizer more efficiently.
Biotechnologist David Lightfoot has isolated a gene from an enteric (having passed through an animal's digestive system) soil microorganism that equips a corn plant to process more nitrogen, and do it faster.
"When a corn plant first emerges, it is surrounded by a lot of nitrogen," Lightfoot explains. "But young plants cannot take up much N right away. With this gene, the plant is able to use more N in the early part of the growing season."
The gene, called glutamate dehydrogenase (GDH), has been inserted into corn tissue and is now being incorporated into breeding programs. Hybrids that contain the super-efficient gene could be on the market within four years.
That's potentially good news for corn growers, on three fronts.
One, it means a corn crop will use more of the nitrogen applied for it. The payoff - in the form of increased yields or lower fertilizer bills - could be significant.
Two, more fertilizer going into the plant means less is liable to run off. Reduced nitrogen runoff was a goal of corn growers who helped fund Lightfoot's research through the Illinois Corn Board.
"That's an important part of our work," agrees Lightfoot. "Depending on his soil type, if a corn grower does a reasonably good management job, he's still losing about 10 percent of the N he applies. We think we can cut that loss in half."
And, GDH may produce bigger plants and higher-quality grain.
"In 1997, we got 10 percent bigger corn plants all the way through - stalks, ears, everything," says Lightfoot. "This gene makes plants more metabolically efficient, although we still don't understand exactly why."
The GDH gene also produces grain with about 7% more protein than average corn.
"There are changes in amino acids, too," points out Lightfoot. "So far, we haven't grown enough of the corn to hold full-scale livestock feeding trials, but nutrient analysis and digestibility studies in the lab indicate the grain may have more feeding value."
In another year, researchers at the university should have enough of the transgenic corn to conduct feeding trials.
"This season, we're doing field tests at seven locations, with three rates of nitrogen fertilizer," says Lightfoot.
"We may have to modify some of the things around the gene to make it more acceptable to companies involved and to the European markets. We're collaborating with ICI/Garst and other companies now. Seed should be on the market by 2003."
Hybrids bearing the GDH gene likely will cost more than conventional hybrids. But bigger yields of higher-protein corn from less nitrogen fertilizer should offset the price premium, he says.