"Scientists now will be able to accurately and efficiently probe the corn genome to find ways to improve breeding and subsequently increase crop yields and resistance to drought and disease," said project leader Richard Wilson, of Washington University in St. Louis, in a statement.
Corn -- also called maize -- is one of the most important plant species on the planet, Wilson said. In 2007, U.S. farmers grew 13.1 billion bushels of corn for human food, livestock feed and feedstock for biofuel, according to the U.S. Department of Agriculture.
On Thursday, Wilson and his colleagues announced they had finished mapping 95 percent of the genome. The map is a result of a $29.5 million, three-year project begun in 2005 and funded by the USDA, the National Science Foundation and the U.S. Department of Energy.
Corn is only the second crop plant to have its genome sequenced. The rice genome map was finished in 2005.
Sequencing the corn genome was a particularly complex task. The genome includes about 2.5 billion DNA base pairs, compared to only about 430 million in the rice genome.
In corn, those units are arranged into more than 50,000 genes. That's more than twice as many genes as humans have -- although, cautioned project scientist Doreen Ware of Cold Spring Harbor National Laboratory, genes in humans do not behave precisely like genes in plants, and so comparing the two is a little bit like comparing apples and oranges.
The researchers will devote the final year of the project to filling in the remaining small gaps in the sequence, Wilson said -- but the "rough draft" map is already being used by other researchers.
"During the past few months, we've heard from numerous members of the maize research community as to how the sequence is making a difference in their work," Wilson said.
The team has made the information available to other scientists via GenBank, a free online DNA database run by the National Institutes of Health.
Nathan Springer, a plant geneticist at the University of Minnesota, says the corn genome information has already been valuable in his work. He studies which genes lead to specific characteristics in corn.
"I have a mutation that turns B73 [a variety of corn] into an albino, and I want to find the mutation," he says. "In the past that used to take 15 years, now it might take six months [...] These are topics breeders have worked on for decades, the fun of it is that we get to go back to old questions with new tools."
