A&M cotton research could open new front in war on weeds

Alex Whitebrook/ July 5, 2018/ News/ 0 comments

Scientists at Texas A&M University are hopeful they’ve developed the Kryptonite for what’s been a losing battle against herbicide-resistant weeds now choking cotton fields across the southern U.S.

If it works as well in the San Angelo test field as it has in a campus greenhouse, the technology could prove revolutionary to a crop that in some regions has become vulnerable to weeds that have developed resistance to three generations of pesticides.

Through a painstaking process, the A&M scientists successfully introduced a genetic trait that allows cotton to thrive in soil that has been enriched with phosphite, which has one less oxygen atom than the phosphate used in traditional fertilizers. Because the weeds don’t have the same trait, they are essentially starved of nutrients.

For decades, the magic formula was to spray fields full of cotton genetically engineered to resist herbicides, such as Roundup, and then watch the weeds dutifully die. But nature started mutating the weeds so they, too, resisted the chemicals.

The result has farmers spending some $9 billion a year in a desperate search for the right mix of older and newer weed killers. In the Mississippi Delta, 60 to 70 percent of the weed populations have developed three-way resistance. Farmers are struggling to keep up.

“If this technology had come along 20 years ago people would say, ‘Why bother? You’ve got Roundup,’” said Kater Hake, vice president of agricultural & environmental research for the industry group Cotton Inc. “Yeah, well, Roundup doesn’t work now.”

Hake referred to the new technology as the “Superman” of weed control, a mighty successor to Monsanto’s glyphosate-based Roundup and others.

“We have not had a new herbicide mode of action since the early ’80s,” Hake said. “We got a new mode of action approximately every year for about 30 years and since then it’s just been flatlined.”

In Texas, the nation’s leading cotton-producing state, the commodity contributes an estimated $24 billion a year to the economy. In addition, Hake said, cotton is seeing a resurgence in demand as both a natural fiber and one that’s better for the environment than petroleum-based polyester.

The ptxD gene that allows absorption of phosphite was first isolated by William Metcalf of the University of Illinois. A Mexican research team then patented the concept of introducing the gene into plants to make them more competitive against weeds in the field.

An A&M team led by Keerti Rathore has been taking the technology to cotton plants. Unlike easily modified “plant mice” such as tobacco or arabdioxis, cotton is a slow-growing, complex plant and notoriously hard to genetically transform.

During a recent tour of the temperature-controlled lab, Rathore showed petri dishes full of cells that take an average about 10 months to produce a plantlet. From the plantlet, it can take another year to grow a plant with a root system strong enough to survive in the greenhouse and produce seeds.

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