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

* U.S. wheat has longest rally since July

* Corn edges higher, soybeans lower

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

(Updates U.S. market activity to close, adds new analyst quotes) CHICAGO, Nov 28 (Reuters) - U.S. wheat futures rose on Wednesday for the seventh straight session, the longest rally since July, as stronger U.S. export prospects and record-low crop conditions triggered a rebound from an early dip even as other commodity markets tumbled. Rising wheat prices helped lift corn futures to a narrow gain in the third day of gains, 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 in 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 a one-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. "Technically, this market is strong. Our dry situation is going to be a question mark all winter." 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 ending 3 cents higher at $8.76 per bushel, the highest in more than two weeks, 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 edged 1/4 cent higher to settle at $7.60-1/4 per bushel. "Corn traded both sides of unchanged with little news to point at, just a little chart buying offset by December long liquidation," ABN Amro analyst Charlie Sernatinger said in a note to clients. 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 trimmed losses and briefly turned positive before ending 3 cents lower at $14.46-1/4. Investment funds were said to have sold 1,000 soybean contracts and 3,000 corn contracts while buying 3,000 wheat contracts. 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 3:05 p.m. CST (2104 GMT)

LAST NET PCT YTD CHG CHG CHG CBOT corn 760.25 0.25 0.0% 17.6% CBOT soy 1446.25 -3.00 -0.2% 20.7% CBOT meal 439.90 0.60 0.1% 42.2% CBOT soyoil 50.11 -0.01 0.0% -3.8% CBOT wheat 876.00 3.00 0.3% 34.2% CBOT rice 1519.00 10.50 0.7% 4.0% EU wheat 276.25 3.00 1.1% 36.4%US crude 86.68 -0.50 -0.6% -12.3% Dow Jones 12,985 107 0.8% 6.3% Gold 1719.01 -23.01 -1.3% 9.9% Euro/dollar 1.2938 -0.0006 0.0% -0.1% Dollar Index 80.3180 -0.0880 -0.1% 0.2% Baltic Freight 1104 7 0.6% -36.5%

(Editing by David Gregorio and Bob Burgdorfer)