GRAINS-Wheat up for seventh day as drought hurts young U.S. crop

* U.S. wheat turns positive, on track for longest rally since July

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

* U.S. drought, South American crop concerns underpin prices

(Updates prices, adds analyst quotes) CHICAGO, Nov 28 (Reuters) - U.S. wheat futures were on pace for their longest rally since July on Wednesday as growing export prospects and record-low crop conditions in the United States triggered a rebound from an early dip even as other commodity markets tumbled. Corn futures also turned higher, following gains in wheat, while soybean futures eased the first time in four sessions as traders locked in profits the day after contracts posted the biggest gains in a month. The price drops for soy 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 fell 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. Wheat futures were on pace for the seventh straight session of gains in the longest such streak since mid-July. 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 5-1/4 cents to $8.78-1/4 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. "You have a crop that is subject to deterioration because the stands are so small and the ground isn't covered," said Joe Christopher, a grain merchandiser at Crossroads Co-Op in Sidney, Nebraska. "You get a lot of dirt blowing around and, of course, that is not a good thing," he said. Still, importers may turn to the United States for wheat as rival supplies in Russia and the Black Sea region shrink, traders said on Wednesday. Corn for December delivery was up 1 cent at $7.61 per bushel as of 12:07 p.m. CST (1806 GMT) after trading as low as $7.54-3/4. Gains in corn were capped by weak demand. U.S. ethanol production, which accounts for nearly 40 percent of domestic corn use, declined 1 percent last week in the third straight week of declines. January soybeans also trimmed losses, shedding 2-3/4 cents to $14.46-3/4 after earlier trading at $14.40. Soybeans were also underpinned by concerns of smaller-than-expected South American production. 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. Top global soy buyer China on Wednesday bought 290,000 tonnes of U.S. soybeans, USDA said. The purchase was an indication to bullish traders that historically high prices have not slowed or rationed demand for the oilseed.

Prices at 12:07 p.m. CST (1806 GMT)

LAST NET PCT YTD CHG CHG CHG CBOT corn 761.00 1.00 0.1% 17.7% CBOT soy 1446.75 -2.75 -0.2% 20.7% CBOT meal 441.00 1.70 0.4% 42.5% CBOT soyoil 50.06 -0.06 -0.1% -3.9% CBOT wheat 878.25 5.25 0.6% 34.5% CBOT rice 1510.50 2.00 0.1% 3.4% EU wheat 276.25 3.00 1.1% 36.4%US crude 86.24 -0.94 -1.1% -12.7% Dow Jones 12,936 57 0.5% 5.9% Gold 1718.59 -23.06 -1.3% 9.9% Euro/dollar 1.2934 -0.0010 -0.1% -0.1% Dollar Index 80.3220 -0.0800 -0.1% 0.2% Baltic Freight 1104 7 0.6% -36.5%

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