GRAINS-Wheat up 7th day on drought, poor crop conditions

* U.S. wheat turns positive on commercial buying

* Corn, soy off lows at open of Chicago pit trading

* U.S. drought, South American crop concerns limit declines

(Updates prices, recasts, adds analyst quotes, changes byline, dateline, previously HAMBURG/SYDNEY) CHICAGO, Nov 28 (Reuters) - U.S. wheat futures rose for the seventh straight session on Wednesday, as commercial buying at the opening of pit trading in Chicago triggered a rebound from an early dip even as other commodity markets tumbled. Soybean futures eased the first time in four sessions and corn the first time in three sessions, as traders locked in profits the day after contracts posted the biggest gains in a month. The price drops for soy and corn were not as steep as those seen by other commodities such as gold and crude oil. The Thomson Reuters Jefferies CRB index of 19 commodities falling to nearly a two-week low on fears of a looming debt crisis in the United States. "We're really positive considering the outside market pressure," said Don Roose, president of grain brokerage U.S. Commodities in West Des Moines, Iowa. Drought conditions in the southern U.S. Plains hard red winter wheat belt propped up wheat futures, with benchmark Chicago Board of Trade December wheat rising 3-3/4 cents to $8.76-3/4 per bushel, a more than two-week high after earlier hitting a low of $8.64-3/4. The crop is in the worst condition in history as it enters winter dormancy, the U.S. Agriculture Department said this week. On Tuesday, wheat futures rose about 3 percent, the largest daily gain since September. "Technically, this market is strong. Our dry situation is going to be a question mark all winter," Roose said. Corn for December delivery was a 1/2 cent lower at $7.59-1/2 per bushel as of 10:08 a.m. CST (1607 GMT) after trading as low as $7.54-3/4. January soybeans were 3-1/4 cents lower at $14.46. "We are seeing some profit-taking on wheat and soybeans today following strong performances in the previous session but the fundamental firm price picture has not changed," said Rabobank analyst Erin FitzPatrick. "Corn is seeing continued support today from concerns about South American crops, especially rain in Argentina." Soybeans were also underpinned by concerns of smaller-than-expected South American production while top global soy buyer China on Wednesday bought 290,000 tonnes of U.S. soybeans, USDA said. Rains are forecast for Brazil's soybean center-west plains this week, meteorologists said, but southern growing regions are set to remain dry, leaving two of the largest producing areas drier than normal in November.

Prices at 10:08 a.m. CST (1607 GMT)

LAST NET PCT YTD CHG CHG CHG CBOT corn 759.50 -0.50 -0.1% 17.5% CBOT soy 1446.00 -3.25 -0.2% 20.7% CBOT meal 440.40 1.10 0.3% 42.3% CBOT soyoil 49.99 -0.13 -0.3% -4.0% CBOT wheat 876.75 3.75 0.4% 34.3% CBOT rice 1509.50 1.00 0.1% 3.4% EU wheat 275.50 2.25 0.8% 36.0%US crude 86.31 -0.87 -1.0% -12.7% Dow Jones 12,871 -7 -0.1% 5.3% Gold 1712.74 -28.91 -1.7% 9.5% Euro/dollar 1.2911 -0.0033 -0.3% -0.3% Dollar Index 80.4370 0.0350 0.0% 0.3% Baltic Freight 1104 7 0.6% -36.5%

(Additional reporting by Michael Hogan in Hamburg and Colin Packham in Sydney; Editing by Alison Birrane and David Gregorio)