Top Crop Manager

Features Herbicides Seed & Chemical
Resistance management, maximizing yield, glyphosate-tolerance, all in one

A true two-pronged attack on weeds is just around the corner for corn and soybean growers. Soon the same program could become an even more robust three-mode-of-action menace to weeds.

April 20, 2009  By Top Crop Manager

 With Optimum GAT technology, growers will have more options with their herbicide programs, including the ability to use a soybean product on corn.


A true two-pronged attack on weeds is just around the corner for corn and soybean growers. Soon the same program could become an even more robust three-mode-of-action menace to weeds.

Optimum GAT is a new herbicide tolerance trait for corn and soybean growers. It was developed by DuPont and is in the final stages of testing. It features tolerance to both glyphosate and to the ALS (Acetolactase Synthase) class of Group 2 herbicides. The first corn seed with the new trait could be on the market as early as 2010. Soybeans are expected by 2011.


Optimum GAT is based on tolerance to both glyphosate and ALS chemistries. By combining Group 9 and Group 2 chemistries, Optimum GAT will give growers the capability of combining the contact weed-killing potency of glyphosate with the ALS family’s residual weed control. It will give soybean and corn producers a better way to control weeds such as wild buckwheat, lamb’s quarters, yellow nutsedge, sow thistle, ragweed and marestail, weeds that are hard to kill with glyphosate alone.

Growers are asking for herbicides that deliver residual control to reduce the need for follow-up sprays. Producers are also craving products that deliver multiple modes of action within glyphosate-tolerant systems to combat shifting weed patterns and resistance. “In the future we intend to go further and add a third mode of action to the mix” says Larry Dumaine, sales and marketing manager for corn and soybean herbicides at DuPont. “We feel the combination of glyphosate and ALS tolerance addresses current resistance problems to both classes of chemistry. And other chemistries that allow you to combine three herbicide groups will give you outstanding weed control plus be a very effective tool to prevent resistance from developing.”

The ALS family of herbicides is a broad category of products that includes the sulfonylureas (SU) herbicides. The SU group itself includes a wide range of products designed for use on crops as diverse as cereals, canola, soybeans and corn. Not all, though, can be used on every crop. For example, producers have not been able to use a soybean product on corn. “Optimum GAT technology broadens the evolved tolerance that corn and soybeans already have to products in this family,” says Dumaine.

This technology will let producers spray chlorimuron ethyl, the active ingredient in Classic, or other ALS herbicides not previously used on corn. “They will be able to use new products specifically designed for use on corn and soybeans that they otherwise wouldn’t be able to use,” says Dumaine.

Scientists did not just tweak current glyphosate resistance technology; they started from scratch. In the old technology, a new target protein that is not inhibited by glyphosate is introduced to function when the native plant is inhibited, making the plant tolerant to applied herbicide. The DuPont trait was developed from a new enzyme produced by a different bacterial gene. It helps plants convert glyphosate into a non-toxic form. The original enzyme was not strong enough to provide true herbicide tolerance so researchers used a new process, called gene shuffling, to improve it.

In basic plant breeding, breeders select two parents with desirable traits and then check the offspring for improvements. Gene shuffling does the same thing but it happens in a test tube rather than in the greenhouse. Traditional breeding allows breeders to screen a few variations at a time. Shuffling technology allows more than two parents to be used and millions of variations to be screened concurrently. Work that would normally take hundreds of plant generations can be condensed into a very short timeframe. “Historically, chemistries were discovered that had more or less tolerance to the crop,” says Dumaine. “In this case we’re developing products specifically for hybrids and varieties containing the Optimum GAT trait. The degree of crop safety is unparalleled.”

 Optimum GAT is the first product DuPont and Pioneer Hi-Bred have had with their gene shuffling technology. Dumaine says it will not be the last. Now that the technology has been successfully integrated into their crop development program it will rapidly bring new hybrids and varieties to market. It is currently being used to improve insect and disease resistance, herbicide resistance, nutritional properties and, of course, yield.


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