“We believe we have every right through our existing Monsanto license agreement to ‘stack’ our Optimum GAT trait with Pioneer soybean genetics already containing a Roundup Ready trait,” said DuPont Group vice president James Borel.

In late summer, the Obama administration said it would look at U.S. agriculture as part of an increased emphasis on antitrust enforcement. U.S. Attorney General Eric Holder and Agriculture Secretary Tom Vilsack also announced plans to meet with farmers to hear their concerns about possible antitrust concerns.

Philip Weiser, a deputy assistant attorney general in the Justice Department, told a farmers advocacy conference in August that federal antitrust regulators are “committed to examining” competition in agribusiness, including the sale of genetically modified seed. He did not single out any companies, but, perhaps tellingly, the conference of the Organization for Competitive Markets, a Monsanto critic, was held in St. Louis.

Less than a week later, Grant called for a probe into what he described as DuPont’s “deceitful attacks” against Monsanto, including what he said was DuPont’s promotion of the conference.

“Your lobbying and communications that paint your company as a victim of limiting technology licenses is dishonest, disingenuous, and downright deceitful,” Grant wrote in a letter to Charles Holliday Jr., chairman of E.I. du Pont de Nemours and Co., DuPont’s formal name.

Monsanto announced earlier this month that though it had been informally questioned by the Justice Department about its marketing in the biotech seed industry, it had not received a subpoena or formal notice of investigation. The Justice Department also had contacted DuPont and Swiss-based Syngenta, another competitor.

Greaney, at Saint Louis University, said the Justice Department often waits until private litigation, like that between Monsanto and DuPont, is resolved. Full-blown antitrust cases are complex and take a long time, he said. “The government certainly wants to have their ducks in a row.”

Monsanto is a veteran of patent and antitrust battles. Diana Moss, a vice president and senior fellow at the American Antitrust Institute, noted in a paper published October 23 that of all patent infringement and antitrust cases involving agricultural biotechnology in federal district and appeals courts from 2000 to 2009, Monsanto was the plaintiff in 55 percent of them and the defendant in 20 percent.

Monsanto’s $1.5 billion acquisition of cottonseed giant Delta & Pine Land Co., which held more than 50 percent of the cottonseed market, was given the green light in 2007 despite political and competitive opposition. As part of the deal, Monsanto agreed to divest its Memphis-based Stoneville Pedigreed Seed Co.and NexGen cottonseed brand.

Monsanto shares got off to a rocky start this week, trading in the low-$70 range, after Goldman Sachs said the company may have discounted seeds to customers by 4 percent to 12 percent to defend market share. In the last 52 weeks, Monsanto shares traded at a high of $94.95 on November 4, 2008, and a low of $63.47 on November 21, 2008.

Since Grant took over the company in 2003, Monsanto has focused on developing better seeds and increasing its market share. It has spent large amounts on research and development—more than $2 million every day—to produce seeds that give farmers greater yields per acre, even under adverse conditions.

Farmers, in turn, have been willing to pay more money for each bag of seed because they get the higher yields and more convenience. The seeds provide better weed control, kill more crop-destroying bugs, and reduce the use of costly pesticides.