Amaranth Genomes Reveal Secrets of Herbicide Resistance

A new study conducted by the University of Illinois Urbana-Champaign and collaborating institutions reveals the complete chromosome-level genomes for Palmer and two other Amaranthus species, smooth and redroot pigweed. The results of this study are a major leap in scientists' understanding of the weeds' biology, including their ability to detoxify common herbicides.

The study focused on Palmer amaranth, the most troublesome of the three species. The research team characterized Palmer's glyphosate resistance gene, which occurs in a large circular segment of DNA that exists outside of any chromosome. The researchers also honed in on sex determination genes in Palmer, to develop modified male plants containing a gene drive. They identified two genes that appear to control maleness on chromosome 3 in Palmer.

Aside from studying the genomes of Amaranthus species, the study also looked into important gene families, such as cytochrome P450s. These weeds have hundreds of similar P450 genes and it has been difficult to identify the ones responsible for non-target-site resistance by detoxifying herbicides before they can cause damage. Co-author Pat Tranel, professor in the Department of Crop Sciences, said the new catalog of P450 genes will help them systematically figure out which ones confer resistance to which herbicides. “That way we can determine which herbicides are detoxified by the same non-target-site resistance mechanism and avoid tank-mixing those products,” he added.

For more details, read the article in ACES News.