Scientists have decoded the genome of corn. (Iowa State)

A team of American scientists has unravelled the complete genetic code of corn and is looking to alter the crop for greater food and energy yields.

The team of 150 researchers, led by Washington University in St. Louis, says the corn genome is a "hodgepodge" of about 32,000 genes squeezed into 10 chromosomes.

By comparison, humans have around 20,000 genes spread among 23 chromosomes. The corn genome is about two billion DNA base pairs long; the human genome has about 2.9 billion base pairs.

The project to sequence the genome of corn began in 2005 and cost $29.5 million, funded by the National Science Foundation and the U.S. departments of agriculture and energy.

The scientists say the genome information will contribute to efforts to create corn strains to meet the world's demand for food, livestock feed and biofuel.

"Seed companies and maize geneticists will pounce on this data to find their favorite genes," said senior author Richard Wilson, director of Washington University's genome centre.

"Now they'll know exactly where those genes are," he said.

"Having the complete genome in hand will make it easier to breed new varieties of corn that produce higher yields or are more tolerant to extreme heat, drought, or other conditions."

Corn is the third cereal crop to have its genome sequenced, after rice and sorghum, and it's the longest plant genome yet discovered.

The United States is the largest producer of corn, responsible for 44 per cent of the global crop, known as maize in much of the rest of the world.

"What's important about the maize project is that it provides a reference DNA sequence for the most important agricultural crop in the U.S., making it much easier for people to look at the many variants of different strains," said Richard McCombie, a professor at Cold Spring Harbor Laboratory.

The development is significant as "society is now faced with growing demands for food and fuel in the face of global climate change and the potential for increased disease pressure," Fusheng Wei and Jianwei Zhang of the University of Arizona observed in the summary of the research in the journal Public Library of Science Genetics.

The research was also published this week in the journals Science and Proceedings of the National Academy of Sciences.