www.czu.cz ; www.raupp.info

Farmers across the Midwest could soon have high-yielding commercial
varieties with effective resistance to soybean aphids as the result of a
major breakthrough at the University of Illinois (USA), August 2004 .


After nearly three years of effort, a team of researchers at the U of I
has identified a single-gene source of aphid resistance that can be easily
crossed into elite commercial varieties.

The lead scientists in this effort are Glen Hartman, plant pathologist with
the USDA's Agricultural Research Service at the U of I, Senior Research
Associate Curtis Hill, and soybean breeder Brian Diers from the U of I's
Department of Crops Sciences. Funding for this research has been provided by
the Illinois Soybean Checkoff Board.

"This gene has been tested in both the greenhouse and the field and has
consistently prevented colonization by soybean aphids," Hartman said.
"Because it is a single dominant gene with identified DNA markers, it can be
readily introduced into susceptible commercial soybean varieties by
backcrossing using marker-assisted selection."

The methods for breeding plants with the aphid-resistance gene will be
licensed for use in both public and private breeding programs.

"Growers could have resistant varieties fairly quickly, especially if
industry adopts this technology," Hartman said. "I think three to four years
would be a reasonable time frame for that to happen."

The aphids were first discovered in large numbers in fields near the end of
the 2000 growing season. After careful scientific investigation, they were
identified as Aphis glycines, which had previously been reported only in
Asia, Australia, and some Pacific islands. By 2003, this pest had emerged as
a major problem for growers throughout the Midwest.

"When the aphids infest a field, the most common means of control is to
spray the field with an insecticide that can cost as much as 20 to 25
dollars per acre," Hartman said. "In 2003 alone, more than one million acres
were sprayed in Illinois and more than three million acres in both Iowa and
Minnesota. Once resistant commercial varieties are available, the savings to
growers will be substantial."

As part of their initial screening process, the team evaluated the various
commercial soybean varieties that had been submitted to the yield trials at
U of I for resistance to the aphids.

"After screening more than 700 varieties, we found that all of them were
basically susceptible to this pest," Hartman said. "We also determined that
there had not been any reported resistance from the germplasm screened in
the part of the world where the aphids originated, which is China."

In the next step, they began screening about 100 cultivars that had been
identified as the major genetic contributors to modern soybean varieties.
Those ancestral lines account for more than 90 percent of the genetic
variation in our current soybeans.

"Luckily we found resistance in two different cultivars," Hill said." One is
called Jackson, which is an old southern cultivar. Another was Dowling,
which also is an old variety grown in the south."

As part of the experimental design, the resistant cultivars were tested in a
specially designed field cage with several commercial varieties and were
treated with an insecticide or left untreated.

"Even with a large numbers of aphids present, we found virtually no
difference in yield and agronomic traits whether these resistant lines were
treated with an insecticide or not," Hartman said. "At the same time, the
commercial varieties were severely damaged when they were not treated with
an insecticide, with many of the plants actually dying."

The researchers followed that up with a series of laboratory and fields
studies that identified the single dominant gene that carried resistance to
the aphids. They also developed methods for identifying and breeding
resistant plants using marker-assisted selection.

"We were able to identify the specific region of the chromosome where the
gene is located using genetic markers," Diers said. "Our team also confirmed
that the resistance is conferred by a single major gene. We are now using
that marker information to breed the resistance gene into adapted soybean
varieties and testing whether there is any associated yield or agronomic
drag associated with the gene. We hope to have resistant varieties available
to farmers by 2008."

With assistance from the Office of Technology Management at the U of I, they
have also applied for a patent and will soon be licensing this new
technology to both university and industry breeders.

"The idea of licensing is to make it a fair playing field for everyone,"
Hartman said. "Otherwise an individual company could take this research and
patent the gene for itself. By licensing the technology to a large number of
companies and public breeders, we can ensure that the benefits will reach
growers across the Midwest as quickly and cheaply as possible."

Additional details on this technology are available on the Internet at
[www.otm.uiuc.edu]

------------------------------------------
Posted to Phorum via PhorumMail