Genetic Diversity Improves Potential Of Soybean Gene Pool: January 1999 Soybeans Today

Soybeans Today January 1999

Genetic Diversity Improves Potential Of Soybean Gene Pool

By Howell Medders

With farmers and other users of groundwater having to drill deeper and deeper into the Sparta Aquifer in many areas, developing technology to reduce reliance on irrigation should be a national priority, St. Francis County farmer Bill Wilkie said at an August field day at the University of Arkansas' Cotton Branch Station near Marianna.

Wilkie was visiting with U of A Agricultural Experiment Station soybean breeder and geneticist Clay Sneller about a research project to increase drought tolerance of soybean varieties. The work is supported by producer checkoff funds from the Arkansas Soybean Promotion Board and the national United Soybean Board.

Wilkie said he has 600 acres of dryland soybeans that typically produce about half the yield of his 600 acres of irrigated beans. An estimated 60 percent of the state's soybeans are grown without irrigation.

Preliminary field tests indicate that new genes identified in a project led by U of A plant physiologist Larry Purcell may make plants more tolerant of drought. These and other valuable new genes are being made available to soybean breeders through Sneller's efforts to widen and deepen the genetic pool used by breeders.

Nearly half of the southern elite lines used by most breeders of soybean varieties adapted to the South have only two parents, Sneller says. That and other statistics define a genetic base that he says is much too narrow and inbred for significant yield improvement or progress on other traits.

The U of A breeder is increasing diversity by crossing southern and northern elite lines and by crossing southern elite lines with selected plant introductions from the USDA germplasm collection.

The strategy is working, Sneller reports. Crosses are producing new lines that yield more than their southern elite parents, plus they are loaded with new genes.

"We yield-tested 246 lines derived from crosses of southern elite varieties by northern varieties. We also tested 90 lines derived from crosses of southern elites by plant introductions.

"In both populations, over 7 percent of the lines had yields that matched or exceeded the yield of their elite parents. Over 40 percent of the lines had yields that were within 5 bushels per acre of their elite parent," Sneller reports.

The program includes DNA fingerprinting of the parents of superior lines. "These results provide a road map in our search for useful diversity," he says.

"We have started DNA fingerprinting of the superior lines. Coupled with the yield data, we will be able to select high-yielding strains that are also diverse from the elite parent."

These lines are being tested again in 1998. The best strains will be released as germplasm, available to all breeders, to maximize the benefit to Arkansas growers. Several of the lines that Sneller considers most promising are already being used in the U of A variety development program.

Soybeans Today January 1999
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For additional information about any board-related activity contact:

Arkansas Soybean Promotion Board
ATTN: Brandy Carroll
P.O. Box 31
Little Rock, AR 72203-0031
Phone: 501-228-1268

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