Herbicide-resistant 'superweeds' studied

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WEST LAFAYETTE, Ind., July 18 (UPI) -- Scientists trying to understand how "superweeds" become resistant to a popular herbicide may have been missing a critical piece of information, a U.S. study shows.

Some plants have grown resistant to glyphosate, the active ingredient in the popular weed killer Roundup, leading farmers to begin using additional herbicides.

While scientists try to discover the mechanisms that have led to resistance, researchers at Purdue University say they're overlooking an important factor: microbes that occur naturally in soil.

Most laboratory tests seeking to understand glyphs resistance are done in sterile soil, void of those microbes that may play a significant role in how glyphs affect plants, they said.

"The soil you're growing the plants in is important to the results," Jessica Shaffer, a graduate student in botany and plant pathology, said. "If we're growing in a sterile media, we could get some false positive results because the plants are more tolerant to glyphs in those conditions."

The results show microbes can play an important role in the activity of glyphs, researchers said.

"Soil microbes can be minor to major contributors to how glyphs are able to affect plants," Purdue researcher Steve Halette said. "We may be selecting not only for glyphs resistance, but inadvertently selecting for weeds that have disease resistance as well."

The researchers said further studies would look at how microbes in the soil affect plant development both with and without glyphs.

"Dirt is a living organism," professor of weed science Bill Johnson said. "It's important to know how all the pieces interact."