Corn, soybean and wheat futures posted their biggest gains in more than a year on signs that a plunge in prices last month is increasing demand for supplies from the U.S., the world’s largest exporter of the crops.

Mexico, the biggest corn importer after Japan, bought 261,200 metric tons from U.S. exporters, the government said today. Soybeans inspected for export more than doubled to 23.4 million bushels in the week ended Oct. 6, with two-thirds destined for China, the U.S. Department of Agriculture said. Russia said today it may impose export duties on grain just three months after lifting a ban on shipments.