Monsanto Co. says it won’t block competitors from creating generic versions of any of its gene- modified seeds as they lose patent protection, a decision that may help mute calls for a U.S. antitrust case against the world’s largest seedmaker. For the first time farmers will be allowed to save and replant Monsanto’s Roundup Ready soybeans after the patent expires in 2014. Rival companies will also be allowed to create their own generic versions of the seeds. Farmers criticized Monsanto in the 2008 documentary “Food Inc.” for its contracts that keep them from saving seeds after a harvest. Monsanto could have thwarted proposed generics by raising multiple patent claims or safety questions with regulators. Roundup Ready soybeans are engineered to withstand Monsanto’s Roundup, the world’s most popular weed-killer. Contracts protect its patents in part by prohibiting farmers from saving seeds from one year’s crop to plant in the next.