Wild Australian Soybean Relatives Hold Genes for Nematode Resistance
Linda McGraw, ARS News Service, USDA, 309-681-6530, firstname.lastname@example.org
Future soybeans may have stronger resistance to a pest that has
long plagued Midwestern farmers, thanks to the diligence of Agricultural
Research Service (ARS) and University of Illinois scientists in
Urbana, Ill. The pest, the soybean cyst nematode (SCN), was first
found in North Carolina in 1954. It has consistently overcome
the best genetic resistance available in soybeans, and its presence
in most soybean-producing states can mean a 5 to 10 percent yield
loss annually. In Illinois alone--where 10 million acres of soybeans
are grown--this could mean millions of dollars in losses.
ARS plant pathologists Glen L. Hartman and Gregory R. Noel and
University of Illinois scientist Ted Hymowitz screened 328 accessions
of Glycine tomentella, the wild Australian relative of soybeans.
They found 50 percent of these germplasm accessions had high levels
of resistance to Race 3 nematodes, the most common type in the
Midwest. There are nine known SCN races in the United States.
In the greenhouse, the researchers inoculated the wild G. tomentella
with nematode eggs and cysts containing eggs. The outcome: no
reproduction of the nematodes on resistant plants. Hymowitz has
crossed G. tomentella and commercial soybeans without using biotechnology
methods. ARS scientists are testing the populations of these crosses
to determine if the resistance genes have been transferred. This
work represents just a portion of the untapped resources in wild
perennial relatives of soybeans that possess resistance to many
other soybean pathogens, according to Hartman.
Hartman and Noel are based at ARS's Soybean/Maize Germplasm,
Pathology and Genetics Research Unit in Urbana. (www.life.uiuc.edu/plantbio/ars/ppgru.html)
The germplasm is part of the USDA Soybean Germplasm Collection.
This work is being funded by ARS, the University of Illinois,
the Illinois Council for Food and Agricultural Research (C-FAR)
and the Illinois Soybean Promotion Operating Board (ISPOB).
Soybean Resistance to Phytophthora
Candace Pollock, Ohio State University, 330-202-3550, email@example.com
Scientist: Anne Dorrance, Ohio State University, 330-202-3560,
The Ohio State University researchers have identified new soybean
varieties that exhibit both partial and complete resistance to
Phytophthora sojae, a pathogen responsible for severe production
losses. But farmers may have to wait several years for a commercial
product if a resistant gene is found that could be introduced
into Ohio varieties, said Anne Dorrance, a plant pathologist at
the university's Ohio Agricultural Research and Development Center.
Dorrance and OSU plant pathologist Fritz Schmitthenner evaluated
1,015 soybean plant introductions (varieties found in other countries)
and found that 32 of them exhibited complete resistance to Phytophthora
and 130 exhibited high levels of partial resistance. All of the
varieties originated from South Korea and were obtained from the
U.S. Department of Agriculture Soybean Germplasm Collection in
Phytophthora sojae causes soybean root rot and is a major problem
in Midwest states that have heavy clay soils. Heavy rains saturate
the soil producing areas with standing water, which provides an
outlet for the pathogen to infect plant roots. The fungus grows
in the roots and into the plant stem, eventually killing the plant.
"The timing right now is perfect to find a new gene and
get it out in the market," said Dorrance, adding that Phytophthora
is slowly adapting to current soybean resistant genes. "We
are continuously putting pressure on those resistant genes. Eventually
they will no longer hold up to the pathogen." Dorrance said
the next step in research is to identify the gene in the South
Korean soybean varieties that are showing resistance to Phytophthora
and introduce it into current commercial varieties in the hopes
those varieties will carry the resistant gene. "If we do
find the gene, it may be five or six years before we can get out
a completely resistant variety, and four or five years before
we could release a partial-resistant variety," she said.
OSU horticulturists Steve St. Martin and Ron Fioritto are conducting
the genetic work.
Though a completely resistant variety is ideal, Dorrance said
varieties that show partial resistance are also exciting. "Partial
resistance basically means that the pathogen has little effect
on the plant once it has grown up and out of the ground,"
she said. "Partial resistance varieties can be very effective,
sometimes having a 30-percent difference in yields compared to
soybean plants that have no resistance to Phytophthora at all,
depending on the disease pressure."
Funding for the project is supported by the Ohio Soybean Council.
Some of the results from the research conducted by Dorrance and
Schmitthenner are available online at http://www.ars-grin.gov/npgs/.
The report is also discussed in OARDC research bulletin 1193 available
at the OARDC Department of Plant Pathology, 1680 Madison Ave.,
Wooster, OH 44691.
Red Clover Silage Boasts Benefits over Alfalfa Silage
Linda McGraw, ARS News Service, USDA, (309) 681-6530, firstname.lastname@example.org
Alfalfa is still the most important forage fed to U.S. dairy
cows, but red clover may be a superior alternative. Switching
cows from alfalfa to red clover silage could help reduce manure
nitrogen levels--a benefit to the environment, according to Glen
Broderick, an Agricultural Research Service dairy scientist in
Madison, Wis. That is because red clover has an enzyme called
polyphenol oxidase that reduces protein breakdown in the silo.
Typically, more than half the protein in alfalfa silage gets broken
down to nonprotein nitrogen (NPN) that is used inefficiently by
the cow. On average, red clover silage has only 60 percent of
the NPN of alfalfa. If not used to make milk, un-used NPN is excreted
by the animal.
Five feeding trials were conducted with cows at the ARS research
farm at Madison. In the latest two studies, cows produced the
same amount of milk on less feed: an average of 68 pounds of milk
a day on 54 pounds of alfalfa dry matter, compared with cows producing
69 pounds of milk a day on 49 pounds of red clover dry matter.
This means a 10 percent increase in feed efficiency and a 10 percent
greater energy value for cows fed red clover silage, according
to Broderick. Protein efficiency was 17 percent better on red
clover than alfalfa in these last two trials. Even if this improvement
applied only to the first half of lactation, when cows are fed
the most protein, nitrogen excretion would be reduced by about
1.5 tons per year on a 100-cow dairy farm.
Red clover will now be easier for farmers to grow, thanks to
new red clover varieties developed by ARS. In the summer of 2000,
ARS released newer red clover varieties that should persist 12
to 15 months longer than older red clover varieties. Seed will
be available to farmers in about two years. For information see: