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Corn+Soybean Digest

Next Up: Bt Soybeans?

Imagine controlling many of the most damaging soybean insect pests without spraying an insecticide. It would be done with Bt soybeans.

That scenario is not only possible, but some scientists are betting it's highly probable — maybe within the next five years.

At least with the first Bt soybean candidates to be commercialized, there would be some years when economically damaging insects wouldn't be controlled. So some insecticide usage would still be needed.

“It might go farther in the longer term, but so far our trials suggest it would be a meaningful and valuable reduction in the use of pesticides, but not an elimination of them,” says Mark Buck-ingham, a Monsanto public affairs spokesperson.

Nevertheless, assuming the Bt genes presently being tested make it through all the hurdles, including USDA's, FDA's and EPA's regulatory requirements, the prospects are exciting.

Wayne Parrott, a biotech crop scientist at the University of Georgia working with soybean breeder Roger Boerma, developed a Bt soybean in 1995 using a cry1Ac gene from Mycogen. It produced essentially complete control of lesser cornstalk borer and velvetbean caterpillar in soybeans, both of which can be extremely damaging.

Then, by combining the Bt gene with genes from PIs (plant introductions) from Japan, they achieved excellent control of even more soybean pests. This gene-stacking approach may also help in developing insect-resistance strategies, the scientist points out.

“We don't have another Bt gene to utilize in stacking, so we're using genes from Japanese soybeans that show natural resistance or tolerance to some insects,” Parrott notes. “When you combine those with the Bt gene, you get something much better than either one alone.

“Based on our work this past summer, we found that a Bt soybean, combined with these other genes, can be a really effective strategy,” Parrott adds. “We're really quite excited about the benefits. And we are quite confident we can put a pretty effective package together.”

John All, University of Georgia entomologist who tests Bt beans for efficacy against insect targets, agrees. “The bottom line advantage of a Bt soybean is that it's as effective as any insecticide available for lesser corn stalk borer in soybeans. This insect has the capability of destroying 20% and even up to 100% of a soybean stand in a severe infestation.”

Monsanto, one of the major players in Bt technology, is testing its version of the cry1Ac gene in many states and in both Brazil and Argentina. By conducting tests in both North and South America, the company is essentially getting two years' worth of field trial testing in one year.

“The primary insect that we have targeted with this product is velvetbean caterpillar, says Monsanto entomologist Ted MacRae. “There is a broad range of other insect targets that we are interested in evaluating, but we still have a long way to go before we complete those evaluations.

“The early indications are, however, that this product performs very well against velvetbean caterpillar,” MacRae adds. “And we've seen good initial indications of efficacy against other target insects.”

Before evaluations are complete, university and company scientists will test these Bt soybeans to assure that problems won't occur with non-target insects. Also, strategies to avoid resistance would need to be developed to pass muster with EPA.

“With what we have seen to this point with Bt crop technology, there really appears to be minimal effects on non-target organisms,” MacRae says. “But we'll evaluate those possible effects in in-field situations to make sure.”

“We are optimistic that within the next five years we'll have a Bt soybean product on the market.”
— Ted MacRae

Public acceptance of this and other biotechnology in the U.S. and abroad could have a possible effect on the future of this technology as well, MacRae says. But he feels the tide is turning in favor of science on this front as more science-based information is made available.

Insecticide usage reduction would be a major benefit, MacRae says. It would reduce exposure risk to the farmer and the environment, reduce chances for potential residue problems on foodstuffs and reduce impact on beneficial insects, fish and other things that might be exposed to the pesticide stream.

There remain definite hurdles to negotiate before Bt soybeans reach the agricultural market. But Monsanto officials and university scientists like Parrott, All and MacRae are optimistic.

“Things are progressing well,” says MacRae. “We are optimistic that within the next five years we'll have a Bt soybean product on the market. And we think that technology has the potential to be a really important tool in the farmer's arsenal for crop production.”

Other companies are likely in the gene hunt for developing Bt soybeans, and we'll detail those and update Monsanto's progress as more information becomes available.

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