At a towering 16' tall, corn native to Oaxaca, Mexico, grows up to 10 aerial roots (compared with two in a typical plant) that secrete gel to protect nitrogen-fixing bacteria. If scientists find a way to express the gene that makes the gel in modern hybrids, it could be a game-changer for corn.
The corn has been tested in Mexico, California and Wisconsin. The gel secreted by aerial roots allows corn to fix nitrogen by excluding oxygen and providing sugars to the right bacteria, according to research at the University of Wisconsin.
“It took us eight years of work to convince ourselves this was not an artifact,” says Jean-Michel Ané, professor of bacteriology and agronomy at University of Wisconsin-Madison and coauthor of the study. “Technique after technique, they’re all giving the same result showing high levels of nitrogen fixation in this corn. What I think is cool about this project is it completely turns upside down the way we think about engineering nitrogen fixation.”
Corn with this capability can acquire 30% to 80% of the nitrogen it needs through fixation, according to the study. Humidity and rain control just how much or little nitrogen the plant gains.
Ironically, this trait was likely bred out of ancient teosinte because the gel was undesirable and thought to be a disease. However, the indigenous people of Mexico recognized the value of the gel secretion and kept the trait alive. Now researchers are trying to find a way to incorporate it into today’s hybrids.
“The corn can be simply crossed to modern hybrids,” Ané says. “We’re using molecular markers to help speed up breeding.”
Speedy as their breeding techniques might be, don’t expect nitrogen-fixing corn in the next couple of years. Ané says it’ll take five to 10 years of additional breeding and research before any kind of a commercial launch is even possible.
“Currently breeding is being performed by academia, but we’re in contact with industry,” he says. “In the short term what we’re doing in the next year or so won’t change the way growers grow their corn. But I hope it will in the next 10 years.”
Found in the Sierra Mixe region of southern Mexico, the gel-secreting corn grows in nitrogen-depleted soil that requires little to no fertilizer. These conditions have selected for corn’s ability to acquire nitrogen. Researchers used five different techniques to confirm the gel is in fact fixing nitrogen from the air that the corn can incorporate into its own tissue.
“This corn showed us that nature can find solutions to some problems far beyond what scientists could ever imagine,” Ané says. “The scientific community probably underestimated nitrogen fixation in other crops because of its obsession with root nodules [such as those in soybeans].”
This research is a collaboration among University of Wisconsin-Madison, University of California–Davis and Mars Inc.
There is more research to be conducted on corn’s ability to fix nitrogen. This gel trait marks a big step, but it’s still less efficient than nodulation found in legumes.
“It’s going to be very difficult to beat the efficiency of the soybean nodule,” Ané says. “We have projects that are trying to engineer nodules into non-legumes like cereals, but these are very long-term projects because it’s a complicated system to recreate. It will take 20-plus years.”