Monsanto Co. is opening its next chapter in genetic technology -- and may face tougher competition.The St. Louis company is investing in gene editing in an effort to keep an edge over rival suppliers of high-tech crop seeds. Monsanto has signed a string of licensing deals to add new gene-editing capabilities to its established methods of genetically modifying seeds, or creating GMOs. But startups and established competitors like DuPont Co. and Dow Chemical Co. are also working on gene-edited plants, which can advance through regulatory reviews faster than seeds developed with earlier biotechnology techniques. Gene editing is different from the genetic modifications that Monsanto and other companies pioneered in the 1980s.