Anheuser-Busch Cos., the nation's No. 1 buyer of rice as well as its largest brewer, says it won't buy rice from Missouri if genetically modified, drug-making crops are allowed to be grown in the state. Last month, Arkansas-based Riceland Foods Inc., the world's largest rice miller and marketer, asked federal regulators to deny a permit for Ventria's project, saying its customers don't want to risk buying genetically modified rice. Anheuser-Busch is believed to be the first major company to threaten a boycott over the issue, according to comments filed last month with the Agriculture Department.