ROME — The Food and Agriculture Organization forecast world wheat production to reach 653 million tonnes in 2010-11, down 4% from 682 million tonnes in 2009-10, and compared with 685 million tonnes in 2008-09 and 611 million tonnes in 2007-08. “Winter wheat plantings in the northern hemisphere are tentatively estimated up marginally from the previous year, but crop conditions are mixed in some main producing areas,” the F.A.O. said in its Crop Prospects and Food Situation quarterly report released Dec. 21. “Overall, wheat production in 2011 will depend on the weather in the coming months. The bulk of the coarse grains and paddy crops are not due to be planted for several months.” Overall, the F.A.O. projected world cereal production in 2010-11 at 2,229.4 million tonnes, up from its previous forecast in November but still down 1.4% from 2,260.5 million tonnes in 2009-10.