RNA technology may offer resistance help

Weed resistance tool | Technique could spray weeds to make them susceptible again

Monsanto is field testing what Robb Fraley, the company’s chief technology officer, considers one of the most exciting agricultural innovations he has seen.

BioDirect technology is a way to create biological pesticides by topically applying double-stranded ribonucleic acid (RNA) to organisms to control gene expression in plants or pathogens.

The double-stranded RNA attacks messenger RNA to prevent them from creating certain proteins.

Monsanto hopes to use the technology to make herbicide resistant weeds susceptible to herbicides again.

“BioDirect technology has the potential to be one of the most exciting advancements for agriculture that I’ve seen in my career,” Fraley said in a news release unveiling the new technology.

That was two years ago, when the product was in the discovery phase of development. Today, it is in the proof of concept phase.

The company is working on four BioDirect projects, and results look promising, said Jim Tobin, Monsanto’s vice-president of industry affairs.

“We’re testing material in the field,” he said in an interview at the 2014 Oilseed & Grain Trade Summit in New Orleans.

“We’re not close enough that I can say we’d be selling it soon, but the tests look good.”

Hugh Beckie, Agriculture Canada’s weed resistance expert, said it would be a valuable new tool in the growing fight against weed resistance.

He estimates 38 million acres of farmland in Western Canada is infected by resistant weeds, costing farmers $1.1 to $1.5 billion per year in increased herbicide use and decreased yields.

Those costs are going to increase, partly because of a lack of new investment in herbicides. Monsanto’s BioDirect product could be the first new mode of action since the 1982 introduction of HPPD inhibitors.

“(BioDirect) is very promising, but whether it’s a silver bullet, time will tell,” said Beckie.

He thinks there could be challenges bringing the technology to market because it is new territory for government regulators.

“It is nonetheless a glimmer of hope in terms of resistance management,” said Beckie.

Zoe McKiness, Monsanto’s director of strategy and operations for chemistry technology, said RNA interference is an elegant technology that results in a biological product rather than a synthetic chemical.

“Every time you eat an apple you’re eating RNA. Even when you drink water, there’s going to be RNA in there from the bacteria that just happen to be in our drinking water,” she said.

“So you’re exposed to nucleic acid constantly, and there has never been a report of an adverse effect from that exposure.”

The gene alteration caused by the RNA is sequence specific, so there is no danger that the spray will affect non-target organisms such as honeybees or monarch butterflies.

The herbicide resistance project is focusing on glyphosate resistant Palmer amaranth and waterhemp, two weeds that have become a major headache for growers in the southern United States.

“They’re huge. You literally have to use a machete or something to get them out and they will take over your fields,” said McKiness.

In the case of Palmer amaranth, the resistance is due to the over-expression of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) protein.

“Instead of having the typical couple of copies, the resistant Palmer has like a hundred copies,” she said.

The goal is for the RNA to knock out the right base pairs along a gene sequence to get the desired response, which is a vastly reduced expression of the EPSPS protein.

Some resistant weeds could be more difficult to work with, depending on the mechanism of resistance.

“Not all plants are readily susceptible to RNA being applied to them topically. Some plants it seems to work on better than others,” said McKiness.

Other applications of the BioDirect technology include managing tospovirus in tomatoes and peppers, controlling the Colorado potato beetle and combatting the varroa mite and viruses in bee colonies.

McKiness expects it will take far less time to get a BioDirect product to market than the 10 years for a genetically modified crop.

For one thing, there will be less research and development time.

“The beauty of this approach is you can make a trigger and test it and understand immediately whether or not it’s going to work as opposed to having to wait, say, two to three years for a biotechnology type application,” she said.

McKiness also anticipates a shorter regulatory approval process. The U.S. Environmental Protection Agency has a separate category for biological pesticides, which requires a less onerous data package than synthetic chemicals.

“It’s not an easier regulatory path, it’s just that you spend less time up front developing the data package,” said McKiness.

She has no idea when the first BioDirect products will reach growers because Monsanto has never commercialized a product like this.

“We’re really excited to take these to market. I think they’re going to add a lot of value to growers,” said McKiness.

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