Fayetteville, Arkansas
July 25, 2007
Two soybean breeding lines
developed by the University of
Arkansas Division of Agriculture offer improved yields under
drought conditions.
The high-yield, maturity group IV 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. |
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