U.S. scientists have identified a naturally mutated gene that enhances the provitamin A content of maize and could select the parent stock for breeding corn with the highest provitamin A content, media reported Friday.

Choosing varieties that have this mutated gene can provide on average three-fold higher levels of provitamin A, the researchers said.

There are thousands of different corn varieties, and they differ greatly in provitamin A levels, the scientists said. White corn does not have provitamin A, but yellow varieties have it in varying levels.

"We've come up with a way to detect varieties that will produce high levels of provitamin A inexpensively," said one of the researchers, geneticist Edward Buckler of the U.S. Department of Agriculture and Cornell University in Ithaca, New York.

"Vitamin A deficiency is a big problem throughout the world, and it causes a lot of childhood blindness and a lot of immune deficiencies," Buckler said.

Experts say vitamin A plays a key role in vision, bone growth, regulating the immune system and other functions.

"In parts of Africa, they eat maize three meals a day. And so if you can bio-fortify what they're eating a lot of, even just a small amount, it adds up," said Torbert Rocheford, a professor of plant genetics at the University of Illinois.

(Xinhua News Agency January 18, 2008)