Two heavyweights in the seed trait business are at odds on how Roundup Ready (RR) technology is being used in new herbicide-resistant soybeans.

In regulatory filings earlier this month, Monsanto accuses DuPont’s Pioneer Hi-Bred of unauthorized use the company’s RR trait. Monsanto claims that Pioneer is stacking the RR trait with Pioneer’s Optimum GAT trait in soybean varieties. “Monsanto has not authorized stacking our first-generation Roundup Ready technology with other glyphosate-tolerant traits,” says Mimi Ricketts, a Monsanto company spokesperson.

Pioneer has said that Optimum GAT trait would be available for commercial sale in 2011. “This approach will combine Pioneer’s proprietary Optimum GAT trait with the Roundup Ready trait in elite Pioneer soybean genetics, demonstrating high yield results and efficacy,” says Jerry Harrington, a spokesman for Pioneer.

Monsanto has requested that Pioneer stop its use of the stacked glyphosate-tolerant trait in soybeans. Pioneer would not comment, citing the confidential nature of the company’s business agreements.

DuPont announced its Optimum GAT technology – billed as its new proprietary glyphosate, ALS-tolerant trait – in March of 2006, and anticipated commercialization as early as 2009.

It is unclear if Monsanto’s filings will delay Pioneer’s release of Optimum GAT soybeans, but Harrington says the company is confident Pioneer brand soybeans with the Optimum GAT trait will be introduced in 2011.