The world's largest grain trading house said on Monday that it will help collapsed Japanese food trader Toshoku Ltd. rehabilitate by turning it into a wholly owned subsidiary.Cargill Inc. of the United States, based in Minnesota, hopes to set up its own domestic food distribution system by using Toshoku's existing network and establish a critical foothold in Japan.Last December, Toshoku applied for court permission to rehabilitate under the Corporate Rehabilitation Law, receiving approval in March. Cargill then sent Toshoku its proposal in April, beginning a series of negotiations. The U.S. trading house will consult with Toshoku in submitting a rehabilitation plan to the Tokyo District Court by March, it said.