Monsanto declined to say how much it had spent developing Roundup Ready wheat. The company said it would focus on expanding sales of gene-altered corn, cotton, canola and soybeans, which have been widely accepted in North America and in many foreign countries.

"I wish it were complex, but it's really not," said Carl Casale, executive vice president of Monsanto, based in St. Louis. "It was just a pure economic analysis of this opportunity relative to others that we have."

For two years, Monsanto's biggest political problem in pushing Roundup Ready wheat had been not its enemies but its friends.

The most influential wheat growers' group, the National Association of Wheat Growers, officially supported the crop and wanted it approved. But the group, and other wheat organizations, also pressed Monsanto to commercialize the product only when certain conditions were met, including evidence that it would be accepted among overseas buyers.

Those conditions became nearly impossible to satisfy as foreign opposition hardened in the past two years. Japanese millers went so far as to tour the American and Canadian wheat belts to oppose the crop.

Roundup Ready soybeans and canola have been huge successes with North American farmers, and they have also embraced other Monsanto crops that have been genetically altered to resist insects. But none of the gene-altered crops widely adopted to date is a food crop with the symbolic significance of wheat.

Soybeans and canola are pressed for their oil, most of which is used in small quantities in processed food. Most corn is fed to animals, and cotton is used for clothing. Wheat would have been by far the most important food crop to "go biotech," in the phrase that farmers use.

Daren Coppock, chief executive of the National Association of Wheat Growers, in Washington, emphasized yesterday that efforts to use biotechnology to improve the wheat crop were not dead. But genetic alterations that benefit farmers alone might not be enough to overcome marketplace resistance, he said, adding that companies need to develop genetic alterations that could benefit millers and consumers.

Among farmers, "nobody has a scientific or technical or philosophical objection to using biotechnology in wheat," he said. "The resistance comes if the person at the very end of the food chain says, 'I'm not going to buy the product.' "

Monsanto has already filed for approval of Roundup Ready wheat in some countries, including the United States, and the company said yesterday it would consult with regulators on how to proceed. Monsanto left open the possibility of seeking approval now in some countries, so that commercialization might be easier if it decides to revive the crop in several years. But the company said it would seek to go to market only if farmer sentiment changes, perhaps after other companies have successfully commercialized biotech wheat varieties.

Monsanto's decision to continue pressing for regulatory approval led to some wariness yesterday among opponents of biotech wheat, who fear the company, perhaps under new management in the future, might break its pledges to farmers.

"We do have a hard time trusting Monsanto," said Gail Wiley, the North Dakota farmer. "If that [regulatory] process is still going forward, we'll be watching."