Unlocking the Genetic Secrets of Maize

Two papers published in this week's Science report major discoveries in maize genetics that could revolutionize maize breeding. Researchers from the United States Department of Agriculture (USDA) and several US universities, found that there are no ‘big genes' or gene regions that control complex traits in maize. Instead, they established that the genetic variation in the crop is a product of "genes working together, each with a small effect that could be manipulated by breeders."

Ed Buckler and colleagues developed and assessed more than 1 million maize plants to identify the genes involved in flowering time. "We looked as hard as we could for big genes and big effects, but they don't exist," Buckler said. "Instead, there are lots of smaller genes around the genome that contribute to flowering time." The team identified 29-56 quantitative trait loci (QTLs) affecting flowering time.

Studying the more than 1,100 marker genes that characterize genetic inheritance, the researchers found that generally, for the vast majority of the genome, each parent contributed about half. But they also observed subtle differences, "indicating that many genes had small effects on reproductive success."

In another paper, the researchers reported that they have uncovered for the first time an important pattern in gene recombination, where large parts of the genome fail to recombine near the center of a hybrid maize's chromosome. This pattern is said to contribute to hybrid vigor.

The articles published by Science are available to subscribers at http://dx.doi.org/10.1126/science.1174320 and http://dx.doi.org/10.1126/science.1174276 For more information, read http://www.ars.usda.gov/is/pr/2009/090806.2.htm and http://www.news.cornell.edu/stories/Aug09/maizeGenetics.html