From Fridge to Field

January 31, 2009 01:41 PM
 


Say "sour milk" and most of us turn up our noses. Turns out that foul-smelling stuff that causes you to cautiously sniff the milk carton each morning has a sweet side. It's the secret behind a new Bacillus thuringiensis (Bt) technology coming soon to your corn field.

It's called the Agrisure Viptera trait, and it is the first of many traits being developed from an entirely new class of vegetative insecticidal proteins (Vip) by Syngenta. Upon full regulatory approval, the Agrisure Viptera trait will be integrated into commercial corn hybrids to provide aboveground control of lepidopteran corn pests such as corn earworm, Western bean cutworm, black cutworm, fall army-worm, common stalk borer and sugarcane borer.

Bt is the most extensively used biopesticide in the world and is currently the sole source of toxin genes for the development of insect-resistant plants. You're already familiar with YieldGard and Herculex products that offer in-seed protection from similar pests. Corn hybrids containing these traits are also derived from Bt, but all of the current technology is based on "Cry proteins."

Cotton to This Trait

Cotton pests may get the first taste of the new Vip protein. Novel transgenic cotton plants that express a vegetative insecticidal protein (Vip) are also being developed by Syngenta.

Cotton growers have been waiting for the new trait since it was developed in 2003. The technology is trademarked VipCot and includes cotton lines that express both Vip3A and Cry1Ab proteins.

Syngenta has received Environmental Protection Agency approval for VipCot, but is awaiting final USDA deregulation. The company is planning a controlled release of VipCot/Roundup Ready Flex for seed increase in elite germplasm in 2009 and full commercial release by 2010.

Louisiana State University AgCenter entomologist Rogers Leonard says VipCot offers a similar pest spectrum to Bollgard II and WideStrike, with excellent activity on bollworm, budworm, loopers and beet armyworm. "Based upon the results of our tests with VipCot in advanced germplasm, it appears to be as good, if not better, than WideStrike on fall armyworm," Leonard says.



The new Vip protein works differently than its Cry protein counterparts, says Tracy Mader, Agrisure traits marketing manager for Syngenta.

Both Vip and Cry-bound proteins cause formation of pores in the gut of susceptible insects, and this pore formation results in insect death. "In layman's terms, they give the insect an ulcer," Mader says. "However, Vip proteins bind to a different receptor protein on the lining of theinsect's mid-gut than Cry proteins."

So what's spoilt milk got to do with it? Wayne Fithian, business lead project manager for Syngenta, explains that Bt is a soil-inhabiting bacteria, but it also spends time in lots of other places.

"We knew Cry proteins had good activity against many pests, and we were pursuing other variations of Cry proteins within Bt," he says.

"Saying Bt is like saying Homo sapiens—just as there are a lot of variations of humans, there are also many kinds of Bt bacteria," he says. "We asked the company's science group to go out and find bacteria from all sorts of environments for us to analyze. Think of it as supersleuthing for the next insecticidal trait."

Scavenger hunt pays off. Among the dust bunnies and garage gunk was a sample of soured milk that ultimately yielded the Agrisure Viptera trait. Similar technology under development in cotton has been trademarked VipCot.

"Who knows how soil bacteria [Bt] got into the milk sample? Perhaps from a dirty hand, or one of the kids took a slug of milk straight from the jug," Fithian notes.
Syngenta claims the Agrisure Viptera trait is unique in its ability to provide improved control of specific pests plus a broad spectrum of insect control. The lepidopteran corn pest complex is difficult to control because the caterpillar (larval) stage of these insects are voracious feeders and, as a group, active all season long.

Syngenta agronomist Bruce Battles says corn plants with the Agrisure Viptera trait in company trials physically look like any other corn plant until insects show up to dine. "It depends on the insect pressure, but growers will likely notice a drastic reduction in feeding damage," Battles says. "What really stands out is the high level of black cutworm control early in the season.

"Corn earworm is another place the technology shines," he says. "Corn earworm is not easily controlled, and growers have become resigned to several rows of ear tip feeding, which opens the ear up to disease and molds associated with reduced grain quality. By contrast, the addition of this trait yields nearly perfect ears at harvest."

The Agrisure Viptera trait has received Environmental Protection Agency approval but is not currently registered for sale. Pending receipt of remaining regulatory and key import market approvals, Syngenta anticipates hybrids with the Agrisure Viptera trait to be sold through Garst, Golden Harvest and NK Seeds brands for 2010 planting. The Agrisure Viptera trait will be stacked only with the Agrisure 3000GT trait stack or the Agrisure GT/CB/LL stack. The company has also signed an agreement to grant Pioneer Hi-Bred International, Inc., access to the trait.

The stack is where it's at. By stacking Vip and Cry proteins together in one hybrid, there's less chance wily worms can become resistant to the technology. Therefore, the trait has the potential to extend the life of both Cry and Vip technologies. There's also a good chance that two proteins in one hybrid will result in reduced refuges.

"This opens up a whole new class of proteins. We now know that there are several out there," Fithian says. "It's also likely additional Vip proteins will be discovered."
What's in your fridge?



You can e-mail Pam Smith at psmith@farmjournal.com.

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