(Updates with comment from DuPont, details, share price)

 
   DOW JONES NEWSWIRES 
 

Monsanto Co. (MON) said Tuesday it filed a patent-infringement lawsuit Monday in federal court against DuPont Co. (DD) and its Pioneer Hi-Bred International Inc. unit to prevent what the world's largest seed supplier alleges is the illegal use of its Roundup Ready herbicide-tolerant technologies.

Monsanto and DuPont have become increasingly competitive in recent years as DuPont looks for growth from its agricultural segment.

Pioneer has the right to sell soybeans and corn with the Roundup Ready trait. Pioneer has publicly said for several years it would replace the trait with DuPont's Optimum GAT trait, but it recently said the Optimum GAT trait, when used alone, poses unacceptable risks to farmers, according to Monsanto.

Monsanto alleges Pioneer is using its Roundup Ready trait to mask problems with the other trait, violating its contract rights and patents.

The two companies have met in court before over patents; A court determined years ago that Pioneer breached its license and improperly used Monsanto's YieldGard corn borer trait. Both companies were named in similar lawsuits by Syngenta AG (SYT) in 2002.

In a statement, DuPont said it has attempted to work through the mediation process Monsanto requested and said it disagrees with Monsanto's position "that they can use their current trait monopoly to prevent the introduction of competitive seed products for U.S. growers."

DuPont added that the lawsuit was another example of Monsanto "trying to flex its anti-competitive muscle in the market."

Monsanto's shares were recently up 4 cents at $89.04 and DuPont's were down 0.6% at $29.23.

-By Kerry E. Grace, Dow Jones Newswires; 201-938-5089; kerry.grace@dowjones.com