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NMSU's Genetically Improved Potatoes Stop Beetles in their Tracks

LAS CRUCES -- Colorado potato beetles living in test plots in Michigan don't know they're eating potato plants genetically engineered in the Mesilla Valley. All they know is they don't like them.

That's just the way scientists with New Mexico State University's Plant Genetic Engineering Laboratory (PGEL) want it. "We've inserted a synthetic bacterial gene into the potatoes that produces a protein, which is harmless to humans and animals but toxic to certain beetles," said John Kemp, PGEL director.

By planting such genetically altered potatoes, farmers in northern New Mexico and Midwestern states like Idaho, Wisconsin and Michigan may someday be spared the expense of spraying for the Colorado potato beetle, a serious pest that defoliates the plants, he said.

In a field trial last summer at Michigan State University's Potato Research Farm, Colorado potato beetles didn't damage NMSU's transgenic potato plants, while ordinary potato plants were heavily infested.

"The beetles probably get a bellyache and move on," Kemp said. "Adult beetles only stayed on the transgenic plants for a few minutes and did not attach egg masses to the leaves. This is very encouraging."

Beetles that do stay long enough to nibble on the potato plants end up dead, Kemp said.

Researchers also ran a field trial at NMSU's Agricultural Science Center at Farmington. Both the center and the state's major potato-growing area are located in the Navajo Nation.

Because there isn't a major potato beetle problem in the Farmington area, this field trial only considered crop characteristics, Kemp explained.

"Yields for the transgenic and the regular potatoes were about the same," said Dennis Sutton, laboratory manager at PGEL. "The transgenic potatoes were somewhat irregular in shape -- not quite as smooth as the other potatoes."

Sutton said, however, that the irregular shape is not related to the protein the potato produces but rather to how the gene is put into the plant. "We're hopeful this will work itself out, as we select the best of our genetically altered plants," Sutton said. Testing will continue this summer. Several years ago, Sutton and Kemp tested the gene that produces the potato beetle toxin, which is isolated from a acteria called Bacillus thuringiensis (Bt). They found that the natural gene doesn't function properly to produce sufficient amounts of the toxin in plants.

"That's because plants and bacteria have different systems for reading DNA messages," Sutton said. DNA (deoxyribonucleic acid) is the material that makes up the genes found in the cells of most living organisms.

Sutton next spent about 18 months making a more plant-like Bt gene by joining 3,600 genetic bits in a precise order. This was the second Bt gene that scientists have synthesized. The first was completed by Monsanto Corp. just months before PGEL.

Technicians at PGEL first inserted the synthesized gene into tobacco plants for testing. When that proved effective, the gene was inserted into the potato plants by Suman Bagga, a plant molecular biologist at PGEL.

Bt sprays have actually been used for decades as effective, environmentally safe insecticides, Kemp said. Different Bt varieties produce highly specific proteins, some of which target particular insects.

When PGEL researchers started their Bt research project about seven years ago, the gene for the Colorado potato beetle toxin was the one scientists knew the most about, Kemp said. "That's why we picked this gene to synthesize with our changes that allow the Bt protein to be expressed in plants," he said. "Our research shows that all this gene jockeying works -- the technology is successful." Now, the researchers are hoping that the protein toxin their synthetic Bt gene produces also will kill beetles that feast on chile, alfalfa and other crops important to the Southwest.

In a collaborative effort with Rutgers University, the gene has made eggplant resistant to beetles. PGEL's part in this effort is headed by Patti Havstad, PGEL's coordinator of business and a research technician.

"More and more Bt genes are being discovered," Kemp said. "We're beginning to look at others we could adapt in our research to genetically improve crops for the Southwest."