When soil is acidic, more aluminum becomes chemically available just below topsoil. Roots are unable to penetrate such soil and generally wheat dies. Aluminum impairs plant growth on nearly 2.5 billion of the world's 8 billion acres of cropland, including about 86 million acres in the United States. One way to increase yields is to make the soil less acidic by adding lime, but lime is expensive to transport over long distances.

"We're going rapidly from 6 billion to 9 billion people in 40 years, according to U.N. projections. Can we or can't we feed them?" said lead researcher Perry Gustafson, a geneticist at the U.S. Agricultural Research Service's Plant Genetics Research Unit in Columbia, Miss. "We'll have to depend increasingly on acidic, high-aluminum soils. If there's any way some of that soil can be made useful without damaging the environment, then we should have the biotechnology to do so."

"I'm not aware of anything that likes aluminum unless it holds their beer," Gustafson said in an interview with United Press International. "Unfortunately, aluminum's one of the most abundant metals in the world, so we have to find ways of growing wheat in aluminum."

The researchers believe that aluminum tolerance genes borrowed from rye may prove wheat's best hope for adapting to acidic soils. Some varieties of rye can tolerate seven times the level of aluminum that wheat can.

The scientists are using genetic analysis techniques to find molecular tags closely linked to the rye gene. The geneticists will then use conventional cross-pollination techniques to impart the aluminum tolerance trait to wheat-rye hybrids.

The tags help the researchers greatly hasten the 15-year period it normally takes to develop a new grain variety simply by helping them make sure the right gene made it through the transfer. Marker-assisted breeding, as the method is called, sidesteps the genetic modification debate.

"We're confident we can get the gene into wheat within the next year," Gustafson said.

If the gene fails to work but is identifiably present because of the tags, the geneticists will then know there are suppression genes lurking somewhere in the wheat that turn off the aluminum tolerance. The scientists hope the gene will work, however, and find applications in the developing world.

"The varieties that are going to feed people in the next 15 years have to be made today, so it's a big gamble," Gustafson told UPI.

The scientists are collaborating with researchers in Brazil and Poland, both nations with especially acidic soil. A better look at the gene may also help scientists figure out how it works, which remains uncertain.

"The progress in Dr. Gustafson's work so far is very promising," said Andrzej Aniol at the Plant Breeding and Acclimatization Institute in Blonie, Poland. "I would like to stress the importance of Dr. Gustafson's work for food production in tropical and subtropical regions of the world, where the largest areas of cultivated land has acidic and aluminum-toxic soils are and, at the same time, where the bulk of human population increase will took place in the near future. According to recent projections from the Food and Agriculture Organization of the U.N., over 90 percent of the population increase until 2020 will be in this region."

(Reported by Charles Choi in New York)