A recent Food and Drug Ad­­ministration (FDA) ruling has im­­proved the prospects for quick Congressional passage of a bill that would block mandatory labeling of foods made with biotech crops, stop state-by-state labeling measures and instead create a nationwide voluntary labeling standard, supporters of the bill said last week.

"We are optimistic about a bill passing in the Senate by the end of this year," said Claire Parker, a spokesperson for the Coalition for Safe and Affordable Food, an organization of farm and food groups that was formed to promote the science and safety of genetically modified organisms (GMOs) and...