One by one, weed species are becoming resistant to popular herbicides. Unfortunately for farmers, agricultural chemical manufacturers say they don’t have any new products in the pipeline to replace those that are gradually outliving their usefulness.

That could change in the years ahead, however.

Researchers at Monsanto are working on technology that could allow farmers to spray weeds with a compound that turns off the weeds’ ability to resist such herbicides as glyphosate, the main ingredient in the company’s Roundup™.

The technology is called RNA interference, or just RNAi. It involves a biological process in which ribonucleic acid – RNA – molecules inhibit genes within cells from functioning in certain ways. RNAi can be applied not only in plants but also animals and humans.

Glyphosate-resistant marestail. Credit: Ohio State University

RNAi was discovered by plant scientists in the U.S. and the Netherlands in the 1990s. Researchers Craig Mello and Andrew Fire did additional research that led to the pair receiving the 2006 Nobel Prize in Physiology or Medicine.

Monsanto already has applied RNAi to develop improved oils in soybeans and new methods for protecting plants from pests that attack corn plant roots. With weeds, RNAi would prevent the plant’s genes from receiving messages to produce proteins that make the weeds invulnerable to herbicide modes of action.

In a recent Indiana Prairie Farmer magazine online post Monsanto’s Greg Heck, Weed Control Platform lead in the company’s Plant Biology Program, said research is leading to the day when a commercial RNAi product will be available. He envisions a product that would be tank-mixed with the herbicide at the time of application. Just how soon that product will be on the market, no one knows.

For now, Monsanto and other herbicide manufacturers recommend farmers use products with various modes of action to slow resistance development in weeds.

By Steve Leer

Google