Research Aims To Give A Legume A Leg Up

Brummer, an Iowa State University agronomist, is working to breed higher-yielding alfalfa, a legume most commonly used as animal feed. One focus of his group's research is heterosis--a hybrid plant's ability to outperform its parents.

"The mechanism of heterosis is unknown," Brummer said. "We're working on pinning down what's causing heterosis from a genetic standpoint and how that affects the plant's morphology and physiology."

Brummer is a professor of agronomy and a researcher affiliated with the Raymond F. Baker Center for Plant Breeding, a center of Iowa State's Plant Sciences Institute. He and a colleague at Purdue University are sharing a $550,000, three-year grant from the U.S. Department of Agriculture to study the mechanics of winter hardiness.

"We've shown you can get heterosis for yield up to 20 percent higher than the better parent in crosses between individual plants," Brummer said.

Now his group is going a step further by crossing populations of plants.

The hybrid seed corn industry was founded on the quest for heterosis, but little work has been done on using it to improve alfalfa yields. Although researchers have enhanced alfalfa's ability to grow late in the season or its ability to survive winter, they've never selected for all three, which is what Brummer is doing.

If he succeeds, it would help reverse years of stagnant or falling alfalfa yields. Lower yields make alfalfa less able to compete with other animal feed, like corn silage. Silage is a good feed, Brummer said, but it leaves the land barren over the winter, increasing the possibility of erosion.

"I'm not proposing an all-alfalfa farm," Brummer said. "It's a part of the whole puzzle in trying to create an agriculture that doesn't cause a lot of undue harm to the environment."

Brummer's work on heterosis combines new molecular techniques with traditional breeding methods. His group is learning what degree of heterosis can be produced by various germplasm, for example.

They're also identifying genes associated with yield and, indirectly, with heterosis.

The information garnered from those activities is being applied to breeding programs using molecular markers to track gene expression.

"We're doing a lot of genetic mapping to dissect these traits," Brummer said.

Brummer is using two alfalfa subspecies: sativa and falcata. Tests show they produce heterosis when crossed, but falcata goes dormant in early fall, resulting in lower yield late in the growing season.

Nondormant sativa varieties also can express heterosis, but they often aren't hardy enough to survive winter. Brummer is adapting the nondormant alfalfa to Midwest winters. They have made huge gains in winter survival over three cycles of selection in four plant populations, he said.

Brummer believes alfalfa can be more profitable for farmers than corn or soybeans. He says the traditional crops lose money without government payments, while alfalfa can bring in as much as $78 an acre.

"My goals really are to reduce farmers' out-of-pocket expenses and increase their return," he said. "If you can plant alfalfa and be sure it won't die, and if you can increase yield, those goals are within reach."

The Plant Sciences Institute at Iowa State University is dedicated to becoming one of the world's leading plant science research institutes. More than 200 faculty from the College of Agriculture, the College of Liberal Arts and Sciences, the College of Family and Consumer Sciences and the College of Engineering conduct research in nine centers of the institute. They seek fundamental knowledge about plant systems to help feed the growing world population, strengthen human health and nutrition, improve crop quality and yield, foster environmental sustainability and expand the uses of plants for biobased products and bioenergy. The institute is supported through public and private funding.