Mutant Corn Calls for Rescue When Killers Attack

Brian Handwerk
for National Geographic News
August 3, 2009

Gotham City has the Bat-signal; the "I've fallen and I can't get up" lady has her Life Call pendant; and now, mutant corn has a chemical to call for a hero when villainous vermin attack.

By genetically supercharging natural defenses, scientists have engineered corn to send out the SOS when beetle larvae begin gnawing at the plant's nether regions, a new study says.

When under assault, the plants' damaged roots emit a gaseous chemical compound into the surrounding soil. Parasitic roundworms receive the distress signal loud and clear and begin doing what comes naturally—entering the beetle larvae and quickly killing the pests.

Created by inserting an oregano-plant gene for synthesizing the SOS chemical, the mutated corn could yield rich harvests with fewer pesticides, the researchers behind the study suggest.

(Also see "Plant Networks Can Send Warnings, Spread Viruses.")

Billion-Dollar Bug

Attacking annually, the western corn rootworm (actually a beetle) is considered the most destructive corn pest in the United States and plagues parts of Europe as well. Known as the billion-dollar bug, the rootworm is said to be responsible for crop damage and pest-control spending valued at more than nine figures.

In their bid to blunt the rootworm's assaults, scientists planted normal corn next to the genetically modified plants and then infested both types with the beetle larvae. The researchers then unleashed roundworms, also called nematodes, on the plots.

"As soon as the nematodes hit [the genetically modified plants]—within three days the larvae were killed," said study co-author Ted Turlings, a zoologist at the University of Neuchâtel in Switzerland.

When it was all over, the genetically modified corn had fared far better than the normal corn, showing much less root damage and 60 percent fewer adult beetles.

Back to the Future

Many plant species attract pest predators.

Acacia shrubs and trees, for example, invite ants to live on them by producing specialized food and shelter for the insects. In return the ants attack herbivores, insects, or even other plants that may threaten their host plant's growth. (Watch a video on acacia-ant relations.)

Likewise, studies have shown that other plants, including some tomato varieties, release chemicals when under attack to attract parasitic wasps, which lay their eggs inside the pests.

And as futuristic as genetic modification might sound, it might be argued that the new work is helping the plant return to a more natural state.

European varieties of the corn tested during the new study, for example, chemically summon nematodes with no genetic intervention. Turlings and colleagues suspect that pesticide use and selective breeding for more robust, faster-growing crops may have gradually neutered this natural defense in the U.S. plants.

Recharging that ability in U.S. corn may create a conundrum for some environmentalists who oppose genetic engineering, because of the possible consequences of messing with Mother Nature's gene pool.

"We used a controversial approach, with genetic engineering, to enhance a very much favored [among environmentalists] approach, which is biological control," Turlings said.

"This is probably the first study to demonstrate that the two are compatible."

Findings to be published tomorrow in the journal Proceedings of the National Academy of Sciences.

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