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K-State Research and Extension

Discovery could change the game in weed control

What we are doing:
glyphosatePalmer amaranth and common waterhemp are two of the most troublesome pigweeds in Kansas agricultural fields, as well as other parts of the United States.
Glyphosate – the herbicide widely used for controlling many weeds – is the key ingredient in products such as Roundup. But pigweeds and other pesky weeds are developing resistance to glyphosate.
Weeds rob agricultural crops of precious resources, such as water and nutrients, ultimately causing yield losses and costing farmers' money. Controlling weeds is a key part of managing a profitable farm business.
K-State researchers recently found that glyphosate-resistant Palmer amaranth plants carry the glyphosate target gene in hundreds of copies, which means that even if one applied an amount much higher than the recommended dose of glyphosate, the plants would not be killed.
Knowing how this process works could point to new ways to curb weed growth.

Our impact:

  • In studying glyphosate-resistant weeds, K-State researchers discovered that the glyphosate target gene, along with other genes actually escaped from the chromosomes and formed a separate, self-replicating circular DNA structure.
  • This structure is known as extra-chromosomal circular DNA (eccDNA). Each eccDNA has one copy of the gene that produces an enzyme that is the target for glyphosate.
  • Because hundreds of eccDNAs are present in each cell, the amount of the enzyme is also abundant. Therefore, the plant is not affected by glyphosate application, and the weed is resistant to the herbicide.
  • Armed with their new knowledge, the researchers can begin work on developing strategies to negate resistance in weeds.
  • It's been known that these circular DNA/chromosomal structures can be unstable. Among potential strategies, K-State researchers want to explore whether they can make the ring-structured chromosomes unstable by not applying glyphosate repeatedly or reducing the selection by glyphosate.

"Glyphosate has a lot of good characteristics as an herbicide molecule. The recommendations that K-State and many others are promoting is 'do not abuse glyphosate.' Use the recommended integrated weed management strategies so that we do not lose the option of using glyphosate for the sustainability of our agriculture."
— Mithila Jugulam, K-State weed scientist 

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