Herbicide Tolerance in the Fields

I’ve had a chance to drive I-71 through southwestern Ohio a few times this fall, and I can’t help but notice the explosion of weeds in the soybean fields this year. I’m guessing almost all larger growers are using Roundup-Ready soybeans, a genetically-engineered cultivar that allows growers to control weeds with the potent herbicide, Roundup. This herbicide is actually an enzyme inhibitor which, when present, prohibits the plant from making aromatic amino acids, killing them. Roundup-Ready crops have a gene originating from bacteria that encodes the target enzyme. This variant of the enzyme is less inhibited by Roundup, allowing the crop to survive even in the presence of Roundup.

Because of its combination of specificity and relatively short half-life in the soil, Roundup has been considered a once-in-a-lifetime herbicide, not likely to be matched anytime soon. And now, because of misapplication and overuse, we are seeing the artificial selection of plants with tolerance for Roundup, rendering it an ineffective herbicide in certain locations. The implications of losing Roundup are huge, as it has been a key enabler for no-till agriculture practice, which helps improve soil structure and reduce soil erosion.

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