New Way to Detect Palmer Amaranth in Contaminated Seedlots

Last summer, farmers in the Midwest got an unwelcome surprise after planting native seed on Conservation Reserve Program acres – Palmer amaranth. Palmer amaranth is an aggressive and hard-to-kill weed. As a possible solution, some states declared Palmer a noxious weed, which prohibits its sale and transport.

The typical testing method involves growing a sample of seeds until the plants are large enough to be identified, but this is a slow and potentially unreliable process. Pat Tranel, molecular weed scientist at the University of Illinois, said growers are calling and telling him, their businesses are up in the air because of this.” Unless they have a way to certify their product is Palmer-free, they can’t sell it,” said Tranel. There is a company that tests individual seeds using DNA sequencing, but charges $100 per seed.

Tranel and graduate student Brent Murphy developed a way around these issues. Their low-cost method can identify Palmer amaranth DNA from within a mixed sample without having to grow the plants.

Once they developed the assay, they asked the University of Illinois Extension’s Plant Clinic to optimize the test for mixed seed samples. Diagnostic outreach Extension specialist Diane Plewa and Plant Clinic technician Elizabeth Phillippi began trying different methods to extract DNA from seed. The Plant Clinic has developed a protocol for commercial testing of seedlots and is now offering the service for $50 per sample. Visit the Plant Clinic website for more information. http://web.extension.illinois.edu/plantclinic/

A quantitative assay for Amaranthus palmeri identification was published in the June 2017 issue of Pest Management Science. The work was supported by a USDA National Institute of Food and Agriculture Hatch grant.

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