There has been a lot of publicity in recent years about growers battling glyphosate-resistant pigweed in soybean and cotton crops. But pigweed isn't the only weed resistant to glyphosate. New research published in the journal Weed Science shows certain populations of junglerice (Echinochloa colona) are now among a growing number of weeds resistant to the herbicide.
Junglerice is a weedy grass that grows in rice, corn and vegetable crops, in gardens, on roadsides and along waterways -- primarily on the U.S. West Coast and in the South. Populations of junglerice resistant to multiple herbicides have previously been found in Arkansas, California and Mississippi, but glyphosate wasn't among them. Now, though, new glyphosate-resistant populations have emerged in Mississippi and Tennessee.
A research team set out to determine the magnitude of junglerice's resistance to glyphosate and to identify the specific mechanisms of resistance. Their study showed a glyphosate-resistant population of junglerice discovered in Mississippi was four times more resistant to the herbicide than susceptible populations, while a population in Tennessee was seven times more resistant.
Researchers identified two separate mechanisms of resistance. In one population, resistance was attributed in part to a target-site mutation in an EPSPS gene. In a second population, resistance was conferred by the reduced translocation of glyphosate.
"Our research shows that integrated management strategies are fundamental to the effective control of junglerice," says Vijay Nandula, a plant physiologist with the USDA's Agricultural Research Service in Stoneville, Mississippi. "It is imperative that growers use a wide range of chemical, cultural and mechanical tools."