Discovery may hasten better corn

ST. LOUIS – In one hand, plant geneticist Michael McMullen holds black kernels of teosinte, the seed scientists say is the ancestor of corn.

In the other, he holds needlenose pliers – definitely needed to crack the tough hulls into a few starchy bits.

The weedy teosinte plant, with its miserly portfolio of kernels, barely resembles its bountiful descendant. McMullen and his colleagues have pegged the genes responsible for the dramatic transformation. They think wild teosinte, with its high genetic diversity, has a lot to offer corn, while inbreeding eventually could confound the search for higher-yielding hybrids.

The work, a joint project among the University of Missouri, the University of California at Irvine and the University of Wisconsin at Madison, was published Friday in the journal Science.

Teosinte is a hardy grass of Mexico and Central America with ears of eight kernels protected in a stony casing. The seeds can be dispersed after passing through animal digestive systems.

Scientists say ancient breeders tried to tame teosinte. Thousands of years later, Native Americans had corn.

The problem is inbreeding. Most corn genes have retained 57 percent of the diversity of teosinte genes, the researchers found. But for at least 1,200 of corn’s 50,000 genes – the genes Native Americans were winnowing – there’s almost no diversity at all. That makes it difficult for modern breeders to stumble on outstanding traits that would make for better strains of corn.

In the paper, the researchers offered a list of 30 genes with high probability of controlling some important corn characteristic. They aren’t sure what all the genes do. Some control the nutrition content of a kernel. Others might control kernel size. But instead of cooking with a 50,000-ingredient recipe, plant scientists can begin experimenting with 30.