Defying Drought
Soybean breeding lines offer genetic advantage for yieldsJuly 25, 2007
Contact Information:
Dr. Larry Purcell, Department of Crop, Soil and Environmental Sciences
479-575-3983 / lpurcell@uark.edu
Dr. Pengyin Chen, Department of Crop, Soil and Environmental Sciences
479-575-7564 / pchen@uark.edu
By Fred Miller, University of Arkansas Division of Agriculture
479-575-5647 / fmiller@uark.edu
FAYETTEVILLE, Ark. — Two soybean breeding lines developed by the University of Arkansas Division of Agriculture offer improved yields under drought conditions.
The high-yield, maturity group V breeding lines, R01-416F and R01-581F, are being released as germplasm that is available to public and private soybean breeding programs for use in developing improved varieties.
"Quite a few public and private breeders have already requested seed for crossing in their own breeding programs," said Pengyin Chen, leader of the division's soybean breeding program.
"By sharing germplasm with other breeders, you get it back into the farmers' hands quicker and in many different forms suitable for a variety of growing conditions," said Larry Purcell, Altheimer Chair for Soybean Research.
Purcell said the drought tolerance in these lines is based on nitrogen fixation, a physiological function that allows soybeans to convert atmospheric nitrogen into a form that can be used by the plants. Nitrogen is very important for yields because protein development is dependent on it and soybean seed is about 40 percent protein.
But fixation is very sensitive to drought, Purcell said. "In most soybean cultivars, nitrogen fixation decreases very early under drought conditions, before other functions like photosynthesis and leaf expansion."
Thomas Sinclair of the University of Florida, who collaborated on the research to develop the new germplasm lines, first identified the link between drought stress and cessation of nitrogen fixation.
After that initial discovery, a research team from several states was assembled by the United Soybean Board to use it for increasing drought tolerance, Purcell said.
In 1993, Arkansas researchers crossed "Jackson," a variety with drought-tolerant nitrogen fixation, and KS4895, a high-yielding maturity group IV variety. The cross resulted in lines in which nitrogen fixation is prolonged about as long as photosynthesis and other plant activities during drought.
Since the cross was made, the resulting lines were screened for yield at locations in Arkansas, North Carolina, Florida and Georgia. The best of these were evaluated for nitrogen fixation in drought conditions.
Purcell said R01-416F and R01-581F also have yields comparable to commercial varieties in the same maturity group that were used as check cultivars.
The best Group IV varieties have yields as high as 60 to 65 bushels per acre, Purcell said. Chen said R01-416F and R01-581F produce yields that are 90 percent of those top commercial varieties.
"During moderate drought, these genotypes have a distinct advantage for yields, even under irrigated conditions," Purcell said.
"The drought tolerance and nitrogen fixation ability are unique," Chen said. "In addition, these two germplasm lines are well adapted to southern growing conditions and cultivation practices. Breeders can make a very quick incorporation of the drought tolerant nitrogen fixation trait into their elite lines."
Chen is using R01-416F and R01-581F in the Division of Agriculture breeding program, crossing them with breeding lines that have slow-wilting traits to improve drought tolerance even more. He is also working to improve the yields.