Potato Grower

WWW.POTATOGROWER.COM 27 may not need to change its underlying genetic code. Instead, the team found that beetles respond by altering the regulation of their DNA, turning certain genes on or off in a process called "DNA methylation." These so-called epigenetic changes allow beetles to quickly ramp up biological defense mechanisms— perhaps putting into overdrive already- existing genes that allow the beetle to tolerate a broad range of toxins found in potato plants. A flush of enzymes or faster rate of excretion may let the insect stymie each new pesticide with the same ancient biochemical tools that it uses to overcome natural plant defenses—rather than relying on the ponderous evolutionary process of random mutations appearing in key genes, that would slowly cause a pesticide to become less effective. Most importantly, the new study shows that these changes—triggered by even small doses of the pesticide—can be passed on to descendants across at least two generations. "We found the same DNA methylation patterns in the grandkid generation. That was surprising because they were not exposed to the insecticide," says Chen. In several other insect species, exposure to pesticides has been shown to change DNA methylation. And some epigenetic changes have been observed to be passed on to future generations of species that reproduce asexually—such as the tiny crustacean Daphnia magna. "But it's long been assumed that epigenetics resets during sexual reproduction," says Kristian Brevik, the lead author on the new study who completed his doctoral degree working in Chen's lab. "That those changes could be transmitted, through multiple rounds of sexual reproduction, to future generations of insects—that's new." The study was published in the December 2020 edition of the journal Evolutionary Applications. OFF THE TREADMILL? Over the last half-century, agricultural researchers and chemical companies have spent millions developing innovative chemical compounds to try to kill off this beetle that causes hundreds of millions of dollars of damage—and almost all eventually fail. "Perhaps it's time to get off the pesticide treadmill of trying to introduce evear-more- toxic chemicals—and recognize that evolution happens, regardless of what we throw at them," says Yolanda Chen. "We could be more strategic in understanding how evolutionary processes work—and invest in more ecological approaches that would enable agriculture to be more sustainable." "Perhaps it's time to get off the pesticide treadmill of trying to introduce ever-more- toxic chemicals—and recognize that evolution happens, regardless of what we throw at them." —Yolanda Chen

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