Tassel (top photo) and ears of teosinte (Zea mays L. ssp. parviglumis Iltis and Doebley). (Images courtesy Hugh Iltis, University of Wisconsin.)

Picking the Perfect Ear of Corn—for More than 6,000 Years

By Erin Peabody
May 26, 2005

Those ears of sweet, crisp corn that are such a familiar part of summertime picnics haven't always looked or tasted that way. Rather, this staple veggie—and its genes—have been tweaked over time by thousands of generations of humans hoping to harvest a better crop.

Now, an Agricultural Research Service geneticist and his colleagues from across the country have discovered what impact all those years of preferential planting have had on corn's genetic makeup.

Latin American maize having kernels of unusual color or shape.

In this week's issue of the journal Science, the scientists report their discoveries on which genes play a role in making corn the important food and animal feed source we know today. Michael McMullen, a geneticist in ARS' Plant Genetics Research Unit at Columbia, Mo., worked with lead author Brandon Gaut of the University of California, Irvine, and scientists from the University of Missouri and the University of Wisconsin.

It's generally believed that corn was domesticated from its wild relative, teosinte, some 6,000 to 9,000 years ago in Mexico. A wild grass, teosinte doesn't look much like corn; it even lacks the "ears" that make corn plants so recognizable.

The researchers discovered that humans, starting with ancient Americans to present-day growers, have impacted about 2 to 4 percent of corn's genes in their quest for a better-tasting and more cultivatable corn crop. The scientists believe the affected genes are most likely linked to qualities like growth and yield.

Their work has many implications, including establishing an approach for studying the genetics of domestication of other crops and animals.

The research also indicates that while a large amount of genetic diversity still remains for the vast majority of corn's genes—enabling future corn improvement by plant breeders—knowing the 2 to 4 percent currently lacking genetic variation will help plant geneticists use wild and exotic corn varieties to continually improve this important crop.

This collaborative research was funded by the National Science Foundation's Plant Genome Research Program.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.