Amaranth seeds on a white background.

MN Impact: New DNA test helps identify Palmer amaranth seeds

June 17, 2020

Issue

Palmer amaranth is a major threat to row-crop agriculture in Minnesota. A single Palmer amaranth plant can produce half a million seeds, grow 2-4 inches in a day, and cause severe loss of crop yield. While it hasn’t yet taken widespread hold in Minnesota, in other areas of the country Palmer populations have already developed resistance to five major herbicide classes. The most common resistances in Palmer are also some of the most widely used herbicides: ALS-inhibitors, PPO-inhibitors, and glyphosate.

What has been done

Palmer amaranth was first detected in Minnesota in 2016, but even before it hit the state, University of Minnesota researchers and Extension specialists mobilized to help state agencies and landowners develop a plan to eradicate infestations before spread to new areas. To date, growers across the state have played a key role in Palmer control by reporting Palmer amaranth to U of M Extension and the Minnesota Department of Agriculture (MDA). The MDA has added Palmer amaranth to the list of prohibited weed seeds, allowing them to prohibit selling seed contaminated with Palmer under the seed regulatory program. However, the similarities between Palmer amaranth and native pigweeds and waterhemp—particularly in its seed state—make identification of Palmer amaranth from other pigweed species difficult. The best way to resolve this identification challenge has been through the use of genetic testing.

Results

This project brought together weed science experts from the University of Minnesota, Colorado State University, Michigan State University, Kansas State University, and the MDA to address these challenges and improve detection technologies, both for seed and for individual pigweed plants. The team assembled a collection of Palmer amaranth populations from across the globe, including plants from Africa, South America, the U.S. and Mexico. They successfully pinpointed genetic markers common to all of these populations and used these targets to develop genetic tests for Amaranth species identification. 

The resulting tests can identify Palmer amaranth from other pigweeds with up to three markers, each of which has over 99.7 percent accuracy. They can also identify the presence of a single Palmer amaranth seed in a sample of 200 visually identical waterhemp seeds.  

This technology offers a cost-effective; easy-to-use and highly accurate DNA test for Palmer amaranth seed identification. Such a tool will be instrumental in helping seed inspectors keep Palmer amaranth out of the state and out of farmer’s fields. Development has been completed and this technology will be ready for deployment in 2020.