About 15 years ago, the St. Louis-based Monsanto corporation developed "Roundup Ready," genetically modified soybean seeds that are resistant to herbicides also produced by the company. In other words, Monsanto made herbicides to kill weeds, then made soy-bean plants that are resistant to the herbicide. Its competitor, Pioneer Seeds, a Des Moines company owned by DuPont and Company, licensed the Roundup Ready formula but also attempted to create genetically modified seeds that could compete with it. Pioneer developed a seed called "Optimum GAT" that combined the Roundup Ready trait with another trait. Mosanto sued DuPont for violating the licensing agreement and for patent infringement, while DuPont claimed that the patent should be considered unenforceable.