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Corn+Soybean Digest

Super Gene Expedition

For the past three years, two researchers at the University of Illinois have been on a genetic expedition that has led them to a treasure house of some very valuable genes — ones they've coined “NitroGenes.”

Their search helps write a new chapter on corn breeding since these NitroGenes have the potential to produce corn hybrids that use much less nitrogen (N) to grow. Those hybrids won't sacrifice yields or the insect and herbicide resistance already present in today's commercial hybrids.

Early indications are that corn hybrids incorporating these NitroGenes could be developed to help producers cut N use by 25%.

Rising N costs and concerns about the impact on water quality have encouraged this search along with a growing interest among seed companies in making such hybrids a reality.

Stephen Moose, assistant professor of maize functional genomics, and Fred Below, professor of crop physiology at the University of Illinois — Champaign/Urbana, have been screening numerous parent materials from the U.S. and tropical areas of the world, including about 30 germplasm lines from Brazil, that may contain these special NitroGenes and exhibit traits linked to what they call “nitrogen use efficiency” (NUE). These lines include nearly 300 corn germplasm lines collected by crop scientists from North Carolina State University.

“The concept of NUE has been around awhile, but several years ago it was difficult to measure because the process involved hundreds of genes; the genetic interplay was complex,” says Moose. “However, with today's advances in biotechnology and other tools, we can scout and screen hundreds of germplasm materials and zero in on those showing the most promise.”

The interesting thing about much of the corn germplasm from the tropics is that many of these lines have grown and yielded well under conditions involving low amounts of fertilizer, Below says.

In basic terms, NUE is the ratio of grain yield to N supplied (both from the soil and fertilizer). The two principal components of NUE are N uptake efficiency, which is the percentage of fertilizer-applied N found in the plant at maturity, and utilization efficiency, the ratio of grain yield to plant N.

According to Moose and Below, today's commercial hybrids have been optimized for yield and NUE at high application rates of N, and they have primarily been selected for only one component of NUE — namely N uptake.

In contrast, Moose and Below want to capture and incorporate those NitroGenes that enhance the efficiency of corn to utilize lower levels of N, but without sacrificing yields and other feed quality characteristics or insect and disease resistance.

Searching for such genes has also prompted the researchers to dip into germplasm dating as far back as 1896. That's the year when the University of Illinois first began to select and maintain two basic groups of corn known as the Illinois High Protein (IHP) and the Illinois Low Protein (ILP) strains.

Examining the germplasm from these two groups has offered the researchers some insight about the relationship between high and low protein levels and their influence on NUE.

Field trials on the most promising lines have already been conducted at the University of Illinois, according to Moose. In the fall, separate parts of the plant including the kernel, cob, stalk, leaves and roots, are analyzed for N content.

“Accurately measuring the phenotypes of corn under real field conditions can be a challenge, and it takes time,” he says. “This is perhaps one of the reasons why progress in this area didn't move as swiftly over the years as one would like.”

In addition to NUE, the research with NitroGenes shows positive results in enhancing feed and protein quality, as well as starch concentration. “If feed, protein and other qualities can be enhanced by utilizing these genes, then it's likely the door will open more to niche market possibilities for producers as well as processors,” says Moose.

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