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Well Rooted for Future Growth

Research into new ways to improve nutrient and water uptake in maize has the potential to increase crop yields and reduce world hunger.

Roots

Selective breeding of maize over the last century to create hybrids with desirable shoot characteristics and increased yield may have contributed indirectly to the evolution of root systems that are more efficient at acquiring nutrients, such as nitrogen, from the soil, according to researchers in the college.

The team’s results suggest that future breeding efforts that directly select for positive root traits could lead to yield gains needed to help feed a growing world population while reducing pollution from excess nitrogen and lowering farmers’ fertilizer costs.

“Creating more nitrogen- and water-efficient crops is a major goal in a world that will see its population reach 10 billion people within 50 years.”

“We all know roots are responsible for the uptake of water and nutrients,” said Larry York, a postdoctoral research fellow at the University of Nottingham, U.K., who conducted the study while earning his doctorate in ecology at Penn State. “However, relatively little is known about how roots do that. If we understand how roots have evolved and which specific root traits increase the plant’s efficiency, then we can take the next step in breeding that can help decrease pollution, save farmers money, and make more yield.”

Finding new ways to improve plant nutrient uptake has global implications, according to Jonathan Lynch, professor of plant nutrition. “Maize is the largest crop in the United States and around the world,” he said. “By the same token, nitrogen is the biggest environmental, economic, and energy cost of maize production. Not only can crop varieties with improved root systems increase yields and reduce hunger in impoverished regions of the world with nutrient-poor soils, they also can decrease excess nitrogen where water quality is a critical issue, such as in the Chesapeake Bay watershed.”

The researchers hypothesized that during a century of corn breeding aimed at increasing yields, root systems were indirectly selected for architecture and anatomy that are more efficient for nitrogen acquisition. To test this, they collaborated with dupont Pioneer, which supplied 16 varieties from the company’s collection representing maize grown commercially in the United States from the early 1900s to the present.

The researchers grew all 16 varieties in both high- and low-nitrogen plots at three different densities, representing both historical and modern growing environments. They measured shoot mass and yield and used a technique known as “shovelomics” to dig up the top portion of the roots so they could measure root quantity, angles, diameters, degree of lateral branching, and length.

The researchers found that the newest commercial varieties performed better in every agronomic environment. These varieties also had root characteristics known to make plants more efficient at acquiring nitrogen from the soil, including fewer nodal roots, longer lateral roots, and larger cortical cells. They published their results online in the Journal of Experimental Botany.

“Creating more nitrogen- and water-efficient crops is a major goal in a world that will see its population reach 10 billion people within 50 years, requiring a 50 percent increase in food production without using more land,” said York. “We believe roots will be central to meeting this challenge.”

—Chuck Gill