A multidisciplinary team from the University of Nebraska-Lincoln has quantified the pollen-driven spread of a gene that makes the state’s most problematic weed resistant to a popular herbicide known as glyphosate.
Following the commercialization of glyphosate-resistant crops in 1996, glyphosate gradually became the most widely used agricultural herbicide in the world. But glyphosate-resistant common waterhemp is now the most damaging weed in eastern Nebraska, infesting more than 1.5 million acres of corn and soybean fields. As of 2016, it has been confirmed in 18 states throughout the midwestern and southern United States.
A study led by Nebraska’s Amit Jhala and Debalin Sarangi found that the herbicide-resistant gene spread to between 38 and 54 percent of the herbicide-susceptible waterhemp that resided within 10 centimeters of a resistant weed. The gene also flowed to between five and nine percent of susceptible weeds residing 50 meters away, according to experiments the researchers conducted at the South Central Agricultural Laboratory near Clay Center, Nebraska.
The study also pinpointed the amplification of a specific gene as the mechanism that induced glyphosate resistance in the susceptible waterhemp population, confirming that the gene amplification is heritable and transferred via pollen-driven gene flow.
“The results of this study are important to explain the rapid dissemination of glyphosate-resistant common waterhemp in Nebraska corn and soybean fields, and in several other states,” said Jhala, assistant professor of agronomy and horticulture.
According to Jhala, weed management strategies adopted by growers have focused mostly on preventing or delaying weed resistance evolution over a small area, rather than preventing the large-scale spread of herbicide-resistance traits. But he said the evidence of long-distance pollen dispersal in common waterhemp should now be considered, noting that the modeling approach considered in the team’s study could be applied in future risk assessment of commercial crops.
The researchers reported their findings in the journal Scientific Reports. Jhala and Sarangi, a postdoctoral research in agronomy and horticulture, authored the study with Drew Tyre, professor of natural resources; Suat Irmak, the Harold W. Eberhard Distinguished Professor of biological systems engineering; Stevan Knezevic, associate professor of agronomy and horticulture; John Linquist, professor of agronomy and horticulture; along with Todd Gaines and Eric Patterson of Colorado State University.
The team received support, in part, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.