CLEMSON PUBLIC SERVICE AND AGRICULTURE
A team of researchers, including Clemson University geneticist Chris Saski, has determined how pigweed changed its DNA to resist glyphosate herbicide.
Unlocking Pigweed Have plant geneticists found the key to Palmer amaranth’s glyphosate resistance?
J
ust hearing “pigweed” can cause fear in row-crop farmers, but Clemson University geneticist Chris Saski and other researchers believe they have discovered the armor this dreaded weed uses to protect itself against glyphosate herbicide. According to researchers, a specific genetic feature — the extrachromosomal circular DNA (eccDNA) replicon — gives pigweed, or more specifically glyphosate-resistant Palmer amaranth, its resistance to the often-used herbicide, making this weed difficult to control. The discovery could help refine herbicide treatment strategies and combat the rise of resistant weeds, says Saski. “The DNA structure of the eccDNA replicon is sophisticated,” says Saski, who is an associate professor of systems genomics in Clemson’s Plant and Environmental Sciences Department. “This circular molecule contains functional genes intermixed 14 /
THE PEANUT GROWER • JUNE 2020
among complicated repetitive DNA that seems to have originated from different chromosomes to form the circle.” He says the difficult sequencing was only possible with advanced single-molecule technology provided by Pacific Biosciences, a biotechnology company based in Menlo Park, California. This discovery provides an explanation of how weeds evolve and adjust to become resistant to herbicides. A DNA Change In Pigweed Glyphosate was introduced in the 1970s and became the most widely used herbicide on many food and non-food field crops as well as non-crop areas where total vegetation control is desired. Then in 1996, Roundup Ready crops were introduced. Being able to plant a Roundup Ready crop and then spray the whole PEANUTGROWER.COM
