Corn futures equalled a record high on Wednesday, bolstered by the worst floods in 15 years in the key US Midwest growing region, while soybeans and wheat prices also advanced.

The rise in prices has, however, sparked concern that demand from both the ethanol and feed sectors may be curtailed.

"You are going to start seeing ethanol production come down and more feed wheat use if it (corn) goes high enough. The market is beginning to get a little bit overdone," said Geneva-based analyst James Dunsterville.

July corn futures on the Chicago Board of Trade had risen 5 cents to $7.47-1/4 a bushel by 1000 GMT while both the May 2009  and July 2009 contracts equalled the current record high of $8.07 first set on Monday.

One European dealer said, however, any setback is likely to be shortlived.

"If you look at the potential damage in the US it is likely that corn and soybean prices are going to be up in the longer term. The danger is we will have technical profit-taking from time to time," another trader said.

The rising Mississippi River could flow over the top of as many as 33 levees, threatening hundreds of thousands of acres of farmland if sandbagging efforts fail, according to a map released by the US Army Corp of Engineers.

The United States is by far the world's largest producer of corn and the Mississippi River runs through the two main corn growing states, Iowa and Illinois.

DTN Meteorlogix indicated further rains are likely in the Midwest, calling for scattered to widely scattered showers on Thursday and more showers on Friday through Sunday.

Soybeans are grown in the same regions of the US Midwest as corn and prices also rose on Wednesday.

CBOT July soybeans were up 5-1/2 cents at $15.63-1/2 a bushel despite less the possibly that a prolonged dispute in key exporter Argentina may be resolved.

Argentine President Cristina Fernandez moved to defuse a prolonged political conflict on Tuesday, asking Congress to ratify a tax hike on soy exports that farmers criticized as authoritarian.

Argentina is the world's third-largest exporter of soybeans after Brazil and the United States and is the largest exporter of soymeal and soyoil.

Wheat prices also rose, boosted by gains in corn and soybeans as well as diminished crop prospects in Australia and Argentina due to dry weather.

CBOT July wheat rose 4-1/4 cents a bushel to $9.02-1/2 while November milling wheat futures in Paris climbed 1.75 euros to 213.50 euros a tonne.

Rice prices were also swept up in the bullish mood with July  up 48 cents at $20.78 per hundredweight. -Reuters