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Plant secrets, some 3,000 to 5,000 years old, may be the key to developing drought-resistant soybeans.

An archeological sleuth in the world of soybean research, Thomas “Tommy” Car-ter, has spent 25 years trying to figure out the mysteries of the soybean plant.

Carter is a research geneticist at the USDA-ARS Soybean and Nitrogen Fixation Research Lab in Raleigh, N.C.

He has turned to lines of soybeans cultivated over thousands of years in China, the native home of soybeans.

Some of those lines developed the ability to thrive despite reduced rainfall.

Carter's studies suggest these lines are slower to wilt under drought stress. These soybeans lines also yield 4 to 8 bushels per acre more than conventional varieties under drought conditions.

He and other soybean breeders have successfully crossed the drought tolerant lines with modern day soybean varieties.

“We are moving these drought genes into advanced backgrounds and companies are starting to cross into this material and get it into their varietal development programs,” said Carter.

The project has received ongoing support from the USDA-ARS and the United Soybean Board.

“Because of farmer support, I can report that good things are coming,” said Carter. “We are making progress.”

The soybean plant carries the complexities of its native China within its genes.

Chinese farmers domesticated the first soybean varieties from the wild soybean, Glycine soja, which still grows wild there.

Over several millennium, farmers produced as many as 20,000 diverse Asian landraces (local varieties) of the domesticated Glycine max, creating the foundation of modern soybean breeding.

The U.S. commercial soybean crop began by growing a sampling of these Chinese soybean landraces which were brought to the U.S. in the early 1900s. Modern U.S. varieties today are descended today from these initial soybean types.

Forward thinkers recognized that important soybean genetic diversity remained in China, despite the progress in U.S. soybean variety development.

In the past century, plant explorers have brought thousands of soybean types and lines to the United States.

The collection of soybean genetic material is kept at the USDA Soybean Germplasm Collection located on the University of Illinois campus at Urbana-Champaign.

This library includes more than 17,000 foreign plant introductions, germplasm of the wild soybean, genetic stocks and U.S. varieties totaling 20,700 items.

The collection is genetic treasure, a legacy of 3000 years of plant husbandry by ancient farmers in Asia.

Each year farmers discovered a few new soybean types growing in their fields (a result of natural mutations) and with a watchful eye, saved the best adapted types as seed stock for the next planting season.

These “keepers” identified by farmers eventually made their way into the modern USDA collection.

Today, this soybean treasure is the source of genes for resistance to rust, root rots, soybean cyst nematode, soybean aphids, a myriad of other diseases and conditions and also drought tolerance.

Carter began looking at the soybean collection almost 30 years ago. Searching for soybeans that tolerated drought, Carter found a handful that met the criteria he established.

Testing the lines at the Sandhills Research Station of North Carolina State University, Carter found that soybeans that wilted slowly tolerated drought better and produced better yields in drought conditions.

Scientists are not yet sure of the mechanisms that allow a soybean plant to tolerate drought.

Carter says that if understanding soybean drought tolerance was a football game, we'd only be at half time, or maybe the second quarter.

“We are spending a lot of time trying to figure out the mechanism,” Carter said. “We have a team with several different experts, including four plant physiologists, helping us figure out what the mechanism is.”

Scientists think slow-wilting soybean plants use water differently than conventional U.S. soybean plants.

“They are using less water early in the season. They may be growing a little slower,” Carter said. “They are saving more of that water to pull out of the ground when they are podding up.

“We know that's not the whole story. We are pretty sure that rooting is going to be the other part of that story.”

The slow wilting soybean also tends to stay greener under drought than the typical soybean types. Some of the slow wilting soybeans from China have very unusual-looking roots, he added.

Carter works with soybean researchers that call themselves “Team Drought.” The members include Jim Orf in Minnesota, Jim Specht in Nebraska, Pengyin Chen and Larry Purcell in Arkansas, Tom Rufty and Tom Sinclair at North Carolina, Roger Boerma in Georgia, and Felix Fritschi in Missouri.

Working across the country, the scientists are developing drought tolerant breeding lines for both northern and southern soybean maturity groups.

“Where we have been screening farmer landraces from southern China, and other parts of Asia in the southern U.S. states, Orf and Specht have been able to get landraces from north China,” said Carter.

Using a similar strategy as Carter, Orf tests exotic materials at the Sand Plains Research Farm near Becker, located between Minneapolis and St. Cloud, just north of I-94.

Orf has found a handful of slow-wilting soybean landraces too that he is crossing with modern soybean lines.

“The initial story was moving the southern discoveries north, but Orf has now reached the point where he has made some of his own discoveries,” said Carter. “We are crossing with some of his discoveries to move that technology south as well.”

Farmers and the soybean industry have benefited from high quality soybean varieties with good properties that yield well. Mother Nature always wins out, though, and without enough moisture in August, soybeans can't thrive.

Fortunately, there are scientists like Tommy Carter dedicated to studying the secrets of the native soybean plant with the goal of reducing drought risk.

(Note: Some information in this article came from the November/December issue of Agricultural Research from the Agricultural Research Service.)