both major grain exporters. Cracks in a tentative peace accord between the two countries revived worries that unrest in the region could disrupt grain exports. Analysts said forecasts for cold weather in the central U.S. that could damage winter wheat crops due for harvest next spring also supported prices. "Trouble between Russia and Ukraine has come back to help out the wheat market, And we're getting reports about a cold [snap] in the Plains states and possible freeze damage,