Commodities : Friday, Sept. 27, 1985. Prices as of 12:45 p.m. : Wheat Futures Prices Rally

Wheat futures prices were higher and corn and soybeans were lower Friday as rumors that the Soviet Union would buy more wheat swept the floor of the Chicago Board of Trade.

Wheat prices were supported by buying that was coming from exporters, a development that led to speculation that the Soviet Union will fulfill the terms of its grain trading agreement with the United States, said Bob Lekberg, a grain analyst with Shearson Lehman Bros.

The Soviets still have to buy 1.1 million tons in the current marketing year to fulfill the terms of their agreement, a step that the Soviets recently said they would take. The current marketing year ends Monday.

Wheat was under pressure earlier in response to reports that the Common Market was undercutting U.S. wheat prices on export markets, analysts said.

Lekberg said corn and soybeans were under pressure from the forecast for clear and dry weather over the weekend, which will provide good conditions for field work.

Trading was quiet, however, partly because financial markets in New York, which usually influence the grain markets, were closed because of Hurricane Gloria.