BOONE, Iowa - The holy grail of seed companies - drought-tolerant corn - will reach farmers in the next few months, offering hope should record hot, dry summers return.

The new seed lines were popular attractions at the DuPont Pioneer, Monsanto and Syngenta exhibits early last week at the Farm Progress Show in Boone. The show displays the latest technology in agriculture.

Drought tolerance will be the latest gee-whiz addition to seed offerings, going beyond the pest and weed resistance made commonplace by the genetic biotech revolution. Iowa yields have increased around 35% to 40% since the late 1980s, helping satisfy a greater demand for corn for food, feed and fuel.

The new seeds won't completely erase the impact of drought. The companies limit their claim to yield increases of 5% to 15% above what non-drought tolerant corn would yield in the kind of heat Iowa endured this summer.

The Professional Farmers of America predicts that Iowa's 2012 yield will be 139 bushels per acre. The drought-tolerant corn would have pushed up average yields to anywhere from 145 bushels per acre to as much as 159 bushels per acre.

The extra bushels would have been welcome - especially at corn prices higher than $8 per bushel - but would still leave Iowa below its 173 bushels per acre yield average for corn from 2009-11.

Seed companies have long been developing drought-tolerant corn.

"Drought tolerance is more complicated. You can't just find a gene that will defeat drought like a bug or weed," said Brent Wilson, agronomist and technical services manager for DuPont Pioneer.

Doubt has also existed about the marketability of drought-tolerant corn in Iowa, where most years produce sufficient rainfall without mechanical irrigation. Agronomists and meteorologists consider the drought this summer the first major one in 24 years.

Even farmers who have hopes of escaping the worst effects of the 2012 drought say they're interested in drought-tolerant seeds.

Vern Smith, who farms near West Liberty, said his farm benefited from some strategically aimed rain this summer.

"My neighbors were estimated at 185 bushels per acre by Pro Farmer, and I think I'll be around that," Smith said. He examined the display for Syngenta's Artesian drought-tolerant line and said, "I'll be interested in buying some for the next season."

The seed companies are too polite to exult in the marketing opportunities afforded by the 2012 drought, but they don't miss its implications.

"This is exciting technology," Monsanto vice president Robert Fraley said as he examined a stand of the company's Droughtgard corn planted in May on the Farm Progress Show grounds.

"The drought this year has reminded farmers in Iowa that it can happen here, too," Fraley said.

Wilson said Pioneer expects its Aquamax seed to be a major product for the company in future years. "It's nice to have a product to roll out after the epic drought we've been through."

But just as they are careful not to cheer the drought, the seed companies are taking care not to over-promise.

Wilson said Aquamax "still requires water to grow."

Fraley said Monsanto is delaying its roll-out until next year, until results of field tests of Droughtgard are completed on about 10,000 dry-land acres in western Texas, Oklahoma and Kansas.

"We're not making a specific claim on yields yet for Droughtgard, but we've seen increases of 5% to 10% above normal in dry areas where its been planted," said Fraley, whose company will sell Droughtgard next year through its DeKalb, Kruger, Fontantelle and other subsidiaries.

Troy Greiss, agronomy service representative for Syngenta, said the company is saying that Artesian can raise yields as much as 15% above non-drought tolerant seeds. But it also tells farmers to be cautious.

"We tell farmers to not overreact," said Greiss. Syngenta owns the Garst, NK and Golden Harvest seed lines.

The Midwest drought caught the seed companies off guard. The product has been designed primarily for the western, and driest, part of the corn belt that encompasses the Texas Panhandle and the western halves of Oklahoma, Kansas, Nebraska and the Dakotas.

"We will need to adjust the genetics as we move the product east into Iowa," said Monsanto's Fraley.

Monsanto, which led the move by seed companies into biotechnology beginning in the mid-1990s, is modifying genetic material to create Droughtgard.

By contrast, DuPont Pioneer and Syngenta are bypassing biotechnology and relying on old-school germplasm breeding in Aquamax and Artesian.

That has made the regulatory approvals needed for biotech unnecessary and enabled them to get to the market this year.

Monsanto has approval from the U.S. government for Droughtgard, but to sell it worldwide the company still needs regulatory approval from several foreign governments.

"You can't launch a new biotech seed line without approval from all the major users," Fraley said. "We expect to have all the approvals within the next few months."