New Rye Could Shed Light on Herbicide Resistance in Weeds

Two new ryegrass lines may bring scientists closer to understanding how grasses develop genetic resistance to weed-killing chemicals.

The new lines, developed by scientists at the Agricultural Research Service, have high tolerance to diclofop-methyl, known in the United States by the trade name Hoelon. This herbicide is registered to control grass weeds in broadleaf and cereal crops.

In western Oregon, ryegrass is not only a major turf and forage crop but also one of the worst weeds of winter wheat. Weedy wheat fields can produce 40 to 50 percent less grain than uninfested fields. The grass weeds can become almost completely resistant to diclofop in as little as three years.

Understanding the biological mechanism of resistance would help scientists develop better controls for this and other grass weeds. The ARS scientists have already showed that ryegrass’ chemical resistance is controlled by only one or two genes.

Studying how resistance developed has been difficult because researchers have lacked populations of resistant and susceptible plants that were otherwise identical. Researchers can now make comparisons using the new lines. ARS scientists developed them from selections from Gulf and Marshall ryegrass varieties.

Small quantities of seed of the new lines, ORARHR-G93 and ORARHR-M93, are available to researchers.

Scientific contact: Reed E. Barker, National Forage Seed Production Research Center, ARS-USDA, Corvallis, Ore., phone (541) 750-8722.