----,-~ .- 1
~ i~Ba~8;2~8iBI:\~ ~~9~~1
4~ 4 .
Keeping a Nice
Place To Live
No other place in America compares
with the Mississippi Delta region. The
people have an easy-going, friendly style
that sets them apart.
The land, too, is special. The combi-
nation of warm days and ample rainfall
makes it ideal for growing cotton, rice,
and soybeans. For deer and duck hunt-
ing, few if any regions surpass the Delta.
It's also a fisherman's paradise.
For many people, the Mississippi
Delta is the only place they would want
to call home. Just ask Floyd Anderson,
Jr., who you can read about in this issue
ofAgriculturalResearch. His family has
farmed here for generations. "Those who
won't respect the land," he says, "don't
farm very long."
His point is simple: If you want to
make money in farming, you'd better do
it in an environmentally sound manner.
It doesn't make sense to destroy the soil
that keeps your family fed. But there are
other reasons to care about farming and
Anderson isn't much of a duck hunt-
er, but like most people here, he enjoys
seeing large migrating flocktake flight.
He looks forward to the time when he
and his young son can go fishing at an
oxbow lake behind his home.
Anderson's concern for the land led
him to participate in a new USDA-
Agricultural Research Service project
to evaluate and improve conservation
farming practices. It involves other
agencies and researchers, as well. The
project is called the Mississippi Delta
Management Systems Evaluations
Area-or Mississippi Delta MSEA, for
Anderson says he's glad to learn that
many of MSEA's findings confirm his
belief that most farmers in the Delta are
good stewards of the land. For example,
research shows the groundwater is very
clean. Erosion may be problem, buteven
before MSEA, farmers were looking for
solutions. This project just gives them a
better chance to find the most effective
Farmers today have more options than
ever to protect the environment. Low-till
cotton and soybeans allow a farmer to
loosen the earth without damaging top-
soil. Cover crops can add nutrient-rich
organic matter, while protecting the soil
from erosion caused by rain and winter
runoff in areas where crops have been
We're learning how to use natural
buffers such as plants, grasses, or wood-
ed areas to trap sediment before it leaves
the field or enters a stream-and these
living barriers are already a part of many
ARS also cooperates in MSEA projects
in other parts of the country. What's dif-
ferent about the DeltaMSEA project is its
focus on the needs and concerns of Delta
growers. Farms around Greenwood, Mis-
sissippi, are notthe same as those in Green-
In the Delta, the fields are flat, the days
are warm, and there's more rainfall than
in the colder, drier Midwest.
And the soils are different, too. Many
Midwestern farmlands were created un-
der the force of glaciers, while the Delta's
farmland comes from soil deposited when
the Mississippi River flooded the entire
region. It makes sense that these soils
And it's not just the soils-farmers
don't grow the same crops. Cotton and
rice are signature crops of the Delta. Even
though farmers in both the Delta and the
Midwest grow corn, wheat, and soybeans,
the varieties they use are bred to fit the
If the climate, soils, and crops are all
different, it makes sense that the MSEA
projects should be specialized as well.
Another goal of this project is to find
effective erosion controls that will be
practiced by farmers. Methods that are
shown to work for the farmers in our
MSEA research are more likely to be
adopted by other growers.
One thing we've had great success with
is allowing fields to flood after harvest,
so that temporary duck ponds are creat-
ed. This provides for great hunting and
shields the soil from the erosive effect of
pelting winter rains.
The farmers have also been impressed
with our hooded sensor sprayer technol-
ogy out of Stoneville, which can save
them up to 70 percent on herbicide costs.
This is another case when environ-
mentally friendly farming can reduce
But the benefit to farmers is more than
Reducing sediment will make the
oxbow lakes clearer and more produc-
tive. This will make them better places to
fish. Thighman Lake, on Anderson's
property, is a prime example.
I am proud of the MSEA research staff.
But I think much credit is also due the
MSEA farmers. They're committed to
the future of their land. They've rightly
enhanced the reputation of all the area's
growers. Plus, they're giving their neigh-
bors excellent examples of what can be
done to preserve the environment eco-
Thomas J. Army
Agricultural Research Service
Mid South Area
Agricultural Research/June 1999
Vol. 47, No. 6
Agricultural Research is published monthly by
the Agricultural Research Service, U.S. Depart-
ment of Agriculture (USDA). The Secretary of
Agriculture has determined that this periodical is
necessary in the transaction of public business
required by law.
Dan Glickman, Secretary
U.S. Department of Agriculture
I. Miley Gonzalez, Under Secretary
Research, Educat.ion. ind Economics
Floyd P. Horn, Administrator
Agricultural Research Service
Sandy Miller Hays, Director
Editor: Lloyd McLaughlin
Assoc. Editor: Linda McElreath
Art Director: VW;llinm Johnon
Photo Editor: Anita Dank-I.
Staff Photographer Scot Bjuer
Information in this magazine is public property
and may be reprinted without permission. Non-
copyrighted photos are available to mass media
as color transparencies. Order by photo number
and date of magazine issue.
Agricultural Research magazine articles and pho-
tographs are posted on the WorldWide Web monthly
at htp ui ,~ ajr usJd gov/is/AR/.
Sub,. ripuon reques[i ,lilId be placed with New
Orders, Superintendent ofDucuments. P O Box
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cover for ordering information.
Complimentary 1-year subscriptions are available
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This niaeazine iiila report research i o ling pes-
ticides It does not cuntlin reconnmendatioins- for
their use. nor does ii ;nipl that usec discussed
herein have been registered. All uses of pesticides
must be registered by appropriate state and/or
federal agencies before they can be recommended.
Reiferenrce t: any commercial product or service
is made with the understanding that no discrimi-
nation is intended jnd no endorsement by USDA
The Li S Departmeni of. Agriculture prohibits
dis. mri nination in all ui priio rairt and .jCtl ilie'
on the bai of race. color. natlonrl origin.
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(Not all prohibited bases apply to all programs.)
Persons with disabilities who require alternative
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contact USDA's TARGET Center at (202) 720-
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To file a complaints I di.rmmairinai.[n. '. rue-
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call (202) 720-5964 (TDD). USDA is an equal
opportunity provider and employer.
Mississippi Delta MSEA 4
Beef Leanness Gene Pinpointed 9
Minimizing Microbes on Fresh-Cut Foods 10
Chicory Mops Up After Turkey Litter 1 3
Saving Grapes 14
Diagnosing Yield Barriers in West Africa 17
Fighting Fusarium 18
Science + Sucrose = New
Liquid Epoxies 22
Science Update 23
Cover: Agricultural Research Service ecologists Charlie Cooper (left) and Scott
Knight sample bottom sediments in Thighman Lake, Mississippi, for small
invertebrates that indicate ecosystem health. Photo by Scott Bauer. (K8463-1)
In the next issue!
(0t Bluetongue disease is an economic problem in both cattle and
sheep industries. ARS has formed the only team of scientists in the
United States studying all three components of the bluetongue prob-
lem: the insects that spread the disease, the animals that become ill,
and the makeup of the virus itself.
(f Remote sensing technology originally developed by Agricultural
Research Service scientists has an interesting spinoff-aerial spotting
of illegal waste disposal sites.
(0 Supposewe knew all the genes involved in cardiovascular health-
which ones contribute to risk, which contribute to protection, and how
much each contributes individually and in combination. It may sound
like a tall order, but that's exactly what researchers in the United States
and abroad are working toward.
Agricultural Research/June 1999
MISSISSIPPI DELTA MSEA
Grower-assisted research helps curb water pollution.
SCOTT BAUER (K8459-1)
F loyd Anderson, Jr., has a special
present for his young son, Will.
It will be perfect for father-son
Anderson, a farmer in the
Mississippi Delta region, has a 40-acre
oxbow lake stocked with bass and catfish
300 yards behind his house. Thighman
Lake is the boy's gift. Anderson is partic-
ipating in an Agricultural Research Serv-
ice program to improve water quality in
oxbow lakes. By doing so, he has helped
preserve Thighman Lake for his young-
"The biggest impairment to fish in
oxbow lakes is sediment-not farm chem-
icals," says ecologist Scott S. Knight, who
is with the ARS National Sedimentation
Laboratory in Oxford, Mississippi.
"That's why we need to find ways to keep
the soil in place on farms."
But Thighman is just one example.
Visibility in the water of nearby Deep
Hollow Lake has improved to a depth of
more than 15 inches, increasing the
amount of algae, fish, and even turtles.
Change at Thighman is less dramatic,
but it's made Anderson excited about the
possibility of fishing there.
Anderson, 45, grew up on the family
farm-the Anderson Planting Company.
He grows soybeans, corn, rice, and some-
times cotton on his 4,300 acres. His lake
is part of a large-scale initiative to eval-
uate how environmentally friendly farm-
ing practices can benefit oxbow lakes. Its
official title is the Mississippi Delta
Management Systems Evaluations Area,
Seventeen farmers cooperate with
ARS, the U.S. Geological Survey, Mis-
sissippi Water Resources Research Insti-
tute, and others who are conducting sci-
entific experiments in the project.
Anderson says the project has given him
and other Mississippi farmers a lift: It has
restored their unfairly tarnished reputa-
"The public never sees all I do to pro-
tect the land," says Anderson. "Why
would I make 10 or 12 tilling trips across
Floyd Anderson, Jr., and his son, Will, check out possible fishing holes in Thighman Lake.
a field and erode my soil-and pay $6 an
acre each time to do it-when 3 or 4 trips
Delta Farmers Try Cover Crops
The 5-year, multimillion-dollar Mis-
sissippi Delta MSEA comprises about
7,320 acres of farmland around three
lakes: Thighman, Beasley, and Deep
Hollow, in Mississippi's Sunflower and
"The project has been an enormous
undertaking," says ecologist Charlie
Cooper. He heads Oxford's Water Qual-
ity and Ecological Processes Research
Unit at the sedimentation lab.
"Most farmers are naturally inclined
to experiment," he says. "We have to have
flexible research and build on what we
learn each season."
For example, cover crops like the wheat
and rye planted in Deep Hollow's water-
shed protect the soil from winter's pelt-
ing rains but need to be replanted every
year. ARS agronomist SethM. Dabney at
Oxford may have an alternative, and he's
trying it on Anderson's farm.
"Balansa clover adds about 75 pounds
of crop-feeding nitrogen per acre to the
soil every year it's used. It produces lots
of seeds, so farmers don't have to replant
annually," says Dabney."Anditdoes well
in the Southeast Cotton Belt."
In springtime, the clover's white flow-
Agricultural Research/June 1999
ers attract honey bees. After the plants
die, they add organic matter to the soil,
which can improve crop productivity.
Preserving Farmers' Reputations
Farming's all I've ever done, and it's
all I ever want to do," Anderson says. "To
learn that the groundwater was not pol-
luted and we're not leaking chemicals like
some people say-that has been worth
whatever I've done for the project, just to
find out that's not the case."
ARS chemist Sammie Smith, Jr.,
drilled wells in the watersheds surround-
ing the three test lakes to monitor for 18
different agricultural chemicals at 5-,
10-, and 15-foot depths.
That's about 100 MSEA wells. Over 3
years, only 5 of more than 600 well sam-
ples showed any pesticide traces. Even
then, the amounts were usually found
shortly after a field application and were
well within the limits allowed for drink-
Another groundwater concern is ni-
trate-nitrogen contamination. This is a spe-
cial risk for infants.
Soil scientistJonathonD. Schreiberhad
been checking wells for this potential
contaminant and he, too, found the water
was safe for drinking.
"We wanted sound science-not sound
bites-on farming and the environment,"
says Frank Gwin, a retired farmer who
serves as the MSEA project's liaison be-
tween researchers and farmers. "If the
news had been bad, we'd have wanted to
know. But it seems we have a clean bill of
Soil Microbes That Cut Pollution
Scientists from Stoneville, Mississip-
pi, are exploring how beneficial enzymes,
microbes, and algae are increased by con-
servation practices. These microbes may
help remove chemicals and enhance soil.
"We hope to better understand how
microbial populations improve water qual-
ity by degrading pesticides," says soil
scientist Martin A. Locke. He heads the
ARS Southern Weed Science Research
Unit in Stoneville. "This knowledge is es-
sential for developing management prac-
tices that maintain diverse aquatic micro-
bial populations that are effective in
who is in Locke's unit, teamed with Knight
to find that Deep Hollow-with the most
conservation practices in use of any of the
MSEA watersheds-had the least sedi-
ment and the highest algal population of
the three lakes. Algae are vital to the lakes'
health, forming the basis of the food chain,
for starters. But that's not all.
"Certain species of one-celled green
algae in the lake can metabolize specific
soil-applied herbicides, such as atrazine
yk-~-------- ~ e------- .. -- .
Oxbow lakes form when a
meandering river shifts to a
new, straight channel, leaving
a crescent-shaped section of
the old channel filled with
andfluometuron," says Zablotowicz. "We
also found a kind of bacteria called fluo-
rescent pseudomonads. These can also
degrade certain herbicides."
The right farming practices can boost
the soil's microbial pollution-stoppers.
Soil Quality's Another Key
"Soil quality means many things to
many people. The factors we are looking
at include increasing organic matter and
improving the balance of plant nutrients,
like nitrogen and phosphorus, that play a
role in soil productivity," says Locke.
Cover crops can improve the soil by
enhancing the food supply for living
things-insects, spiders, worms, and mi-
crobes-that help make the soil porous,
says Dabney. He is evaluating tilling
methods that won't disturb cover crops
but will break up hardened soil.
Some farmers believe reduced tillage
Agricultural Research/June 1999
and cover crops will open the door to dis-
eases, weeds, and reduced yields. If
MSEA demonstrates this doesn't have to
happen, more farmers will be willing to
try these practices.
"Limited information is available on
the effects of reduced tillage and cover
crops in cotton production systems," says
Locke. "Our initial goals were to charac-
terize the differences in the biological,
chemical, and physical soil properties in
theBeasley andDeep Hollow watersheds,
where differentcotton managementprac-
tices are used."
At Deep Hollow, Dabney is testing
gypsum, or calcium sulfate, as a way to
help with yields. "People have been us-
ing lime for centuries to reduce soil acid-
ity and build up calcium, an essential el-
ementforplants," he says. "ARS research
at West Lafayette, Indiana, has shown
that gypsum lets more rain soak into the
soil and reduces erosion."
Keeping Weeds in Check
Differences in soil properties can in-
fluence how agricultural chemicals re-
act. Knowledge of those differences and
of weed populations in the three water-
sheds will help determine proper herbi-
cide and fertilizer applications. The in-
formation will also allow the use of
computer-driven systems in weed con-
trol and other farm chores.
"Areas with soils with higher organic
matter content and clayey texture tend to
have more weeds and more herbicides
binding to the soil," Locke says. "With
reduced-tillage cotton and soybeans,
weed populations were higher than with
conventional tillage. Butmost weeds were
adequately controlled with post-
emergence applications using shielded
Deep Hollow grower Philip Barbour' s
farm was the test site for a hooded sensor
sprayer that helped him reduce herbicide
"That hooded sensor sprayer is some-
thing I'd like to try," says Anderson. "I
noticed it saved Philip a lot of money."
SCOTT BAUER (K8456-11
Microbiologist Robert Zablotowicz uses
thin-layer chromatography to study
metabolism of herbicides by lake bacteria
SCOTT BAUER (K8450-1)
Biological technician Terry Welch identifies
fish and measures their lengths and weights
to evaluate changes in fish communities
resulting from new watershed management
Agricultural engineer James E. Hanks
worked with Patchen, Inc., of Los Gatos,
California, to develop and test the eight-
row hooded sprayer. Hanks is in Stone-
ville' s Application Production and Tech-
nology Research Unit.
The sensor distinguishes differences
in light reflected from bare soil versus
weeds in the area between rows of plant-
ed crops. The sprayer applies herbicides
only where weeds are present. Hanks ran
the sprayer's Deep Hollow tests.
"We evaluated the weed sensor as a
way to cut herbicide use for cotton and
soybeans grown under conservation till-
age," says Hanks. "Herbicide savings
averaged 63 percent on 105 acres of cot-
ton and 49 percent on 115 acres of soy-
beans during a 3-year study.
"And the less herbicide used, the less
the potential for adverse environmental
Botanist Charles T. Bryson, who is in
Stoneville's Weed Science Unit, has been
recording levels and shifts in weed pop-
ulations in various cotton and soybean
fields at Deep Hollow watershed. The data
will be used to enhance the hooded sensor
"Weed species and populations in-
creased with fewer tillage operations,"
says Bryson. "But identifying which
weeds are present allows the farmer to
target a specific troublesome weed with
certain tillage practices or herbicides.
Mapping weed populations within fields
also allows for variable herbicide appli-
Bryson's research already shows that
the equipment is highly effective as it is.
"I have taken data on weed popula-
tions following the use of the hooded
sensor sprayer," says Bryson. "Most of
the weeds are controlled as effectively
with the sensor sprayer as with traditional
Nature's Living Filters
Low tillage and the hooded sensor
sprayer are exciting parts of MSEA, but
nature has its own method of protecting
Agricultural Research/June 1999
SCOTT BAUER (K8465-1)
the water. Both Deep Hollow and Beas-
ley have wooded areas near their banks
that serve as buffers between lake and
farm. Ecologists call these natural bank
barriers riparian zones.
"Riparian zones and wetlands are frag-
ile parts of the Delta ecosystem and serve
as living filters to protect oxbows from
agricultural chemicals and sediment,"
says Locke. "Restoring and preserving
them make sense if we want to enhance
soil and water quality."
ARS scientists from Oxford and
Stoneville, along with Mississippi State
University scientists, have been looking
at Beasley's riparian zones. They found
that because of forest litter, the soils have
the potential to rapidly bind pesticides
and break them down.
Farmers and others can create ad-
ditional natural barriers using a filter strip
of strong, tall grasses. ARS asked USDA's
Natural Resources Conservation Service
to plant filter strips around Beasley and
Stoneville ecologist William J. Stad-
don, who is also in Locke's unit, found
that the vegetative residue in the filter
strips enhance microbial life in the soil,
increasing its ability to break down the
herbicide metolachlor used in soybeans
The filter strips and other vegetative
barriers may even help manmade erosion
controls be more effective. One popular
practice is called an overall pipe. Farm-
ers build a small ridge around their field
and install apipe to carry water away from
the field without causing erosion.
Boards can be used to partially block
the inlet to these overall pipes during the
winter, creating shallow ponds. The ponds
protect the soil from winter's pelting rain
and give sediment a chance to settle out.
By releasing storm water slowly, down-
Cover crops prevent erosion and add
nitrogen to the soil. Here, technicians Earl
Gordon and Jennifer Tonos collect samples
so they can estimate the amount of plant
matter in a field near Thighman Lake.
Agricultural Research/June 1999
stream flooding is reduced.
When the boards are removed in the
spring and summer for planting crops,
however, the pipes alone don't trap
enough sediment to keep the lakes clear.
"Adding a tall grass barrier in front of
the pipe inlet will help keep soil from
leaving the field," says Dabney.
It seems the grasses do their job by
slowing the water just enough to allow
the sediment to settle, without flooding
When farmers hold water on the fields
in the winter, the ponds attract ducks. This
can mean extra farm income from hunt-
ing. Between the ducks and the flooding,
weeds in the field are reduced, so the
farmer needs less herbicides when the
temporary ponds are drained.
"That's the great thing about MSEA,"
adds Cooper. "We find things that benefit
people and nature-it's a winning com-
bination."-By Jill Lee and Tara Weav-
SCOTT BAUER (K8466-1)
Left to right: Project coordinator Frank Gwin, farmers T.A. Murtagh and David Walker,
and soil scientist Martin Locke review an aerial map of Mississippi Delta counties involved
in the Management Systems Evaluations Area project.
To determine nutrients in shallow ground-
water, chemist James Hill places water in
an autosampler of the flow-through
This research ispartofWater Quality
andManagement, anARSNational Pro-
gram described on the World Wide Web
Charles M. Cooper is in the USDA-
ARS Water Quality/Ecological Proces-
ses Research Unit, 598 McElroy Dr.,
Oxford, MS 38655-2117; phone (601)
232-2935, fax (601) 232-2915, e-mail
Martin A. Locke is in the USDA-ARS
Southern Weed Science Research Unit,
P.O. Box 350, Stoneville, MS 38776-
0225; phone (601) 686-5272, fax (601)
686-5422, e-mail firstname.lastname@example.org. *
Agricultural Research/June 1999
BEEF LEANNESS GENE
Superbly lean-but tender-beef rump roasts may reach
more tables when new technology helps cattle breeders
turn a possibly undesirable gene into a sure asset.
On a genetic map for cattle, Agricultural Research
Service scientists and their colleagues have pinpointed
a gene that codes for a form of protein called myostatin. In its
usual active form, myostatin puts the brakes on the number of
muscle fibers produced in a calf fetus. Another, less common
version of the gene produces inactive myostatin.
Researchers now know that two copies of the gene for inac-
tive myostatin are responsible
for double muscling-that is,
extreme muscularity in the hind KEITH WELLER (K8448-1)
quarters of cattle.
Double muscling is consid-
ered an undesirable trait from
production standpoint. Some-
times, birth of double-muscled
calves must be assisted by such
extraordinary means as Cesar-
Cattle with only one copy of
the gene for inactive myostatin
look normal, but their carcass-
es typically yield about 7 per-
cent more beef that has about
14 percent less overall carcass
fat than beef with active myo-
statin, says Timothy P. Smith.
He is a chemist at ARS' Ro-
man L. Hruska U.S. Meat An-
imal Research Center (MARC)
in Clay Center, Nebraska.
After several years of map-
ping research, MARC scien-
tists had nearly pinpointed the
location of the genetic defect
causing extremely large mus-
cles-or muscular hypertro-
phy-in double-muscled cat-
tle to a small segment of bovine
chromosome 2. Then, scientists
at the Johns Hopkins School of
Medicine in Baltimore, Mary-
land, discovered a gene they
muscularity in mice.
Putting the two findings to-
gether, MARC researchers This Piedmontese-Hereford cross
teamed up with scientists atthe muscling because it inherited a d
RuakuraAgriculturalResearch of its parents.
Centre in New Zealand and within months were able to show that
changes in the bovine myostatin gene cause double muscling.
Similar results were reported from a team of European labs. The
Johns Hopkins team has also found myostatin genes in pigs,
chickens, and turkeys.
Smith and his colleagues at MARC have since developed
DNA tests for slightly differing versions of the myostatin gene
that are often found in Belgian Blue and Piedmontese cattle
breeds. "We hope to see these tests become available for com-
mercial use in the near future," says Smith.
Cattle breeders could obtain
test results from blood, semen,
or a small sample of a cow's ear
to plan sure-bet mating strate-
gies for producing cattle with
just one copy of a gene that sig-
nals production of inactive or
Weakly active myostatin. Such
cattle would provide the kind of
beef today's consumer wants
without increasing the risks of
difficult calvings, Smith says.
The researchers found that
cattle with at least one gene for
inactive myostatin produce beef
that has less marbling, or intra-
muscular fat, as well as less ex-
Contrary to popular opinion,
Smith says, less marbling
doesn't always mean less ten-
der. The researchers expect to
pinpoint a number of genes that,
together, control tenderness.-
By Ben Hardin, ARS.
This research is part ofAni-
mal Germplasm Resources,
Conservation, and Develop-
ment, anARSNational Program
described on the World Wide
Web at http://www.nps.ars.
Timothy P. Smith is at the
USDA-ARS Roman L. Hruska
U.S. Meat Animal Research
Center, P.O. Box166, State Spur
18D, Clay Center, NE 68933;
phone (402) 762-4366,fax (402)
ed calf displays classic double 762-4390, e-mail
active myostatin gene from both email@example.com. *
Agricultural Research/June 1999
Left to right: Pathologist Ching-Hsing Liao, Vlasta Pilizota (visiting scientist from Croatia), and microbiologist Dike Ukuku work on
methods to improve microbiological quality and safety of fresh-cut cantaloupe.
on Fresh-Cut Foods
F ruits and vegetables are vital to
ourhealth and well-being, provid-
ing essential vitamins, minerals,
and fiber to our diet. But although
U.S. consumers have one of the
safest supplies of fresh produce in the
world, new outbreaks of food poisoning
linked to fruits and vegetables continue to
These outbreaks come from produce
grown both here at home and abroad. In
the pastfew years, outbreaks offoodborne
and Salmonella found on lettuce, canta-
loupe, and sprouts; Shigella on parsley
and lettuce; and Cyclospora on raspber-
"Concern about these outbreaks and
their implications led the current admin-
istration to propose a research strategy
that enhances the safety of fruits and vege-
tables," says James A. Lindsay. He is the
primary leader of the ARS national re-
search program directed toward the mi-
crobial safety of fruits and vegetables.
As part of his earlier National Food
Safety Initiative, on October 2, 1997,
President Clinton launched the Produce
and Imported Foods Safety Initiative.
Under this plan, USDA and other
government agencies were charged with
developing a research plan that would
help minimize risks posed by microbial
pathogens on fresh and minimally
processed fruits and vegetables.
Examples of minimally processed
produce are bagged salads, melon balls,
and many otherpeeled or sliced-but still
uncooked-fruits and vegetables.
"Working with the Food and Drug
Administration's (FDA) Center for Food
Safety and Applied Nutrition, our new
research plan focuses on reducing dis-
eases caused by foodborne pathogens,"
Lindsay says. "Our first official response
to the President's directive was to publish
guidelines for U.S. industry that provide
voluntary, science-based information for
improving the safety of fresh produce as
it moves from farm to table."
Titled "Guide to Minimize Microbial
Food Safety Hazards for Fresh Fruit and
Vegetables," the publication-which is
Agricultural Research/June 1999
not a government regulation-addresses
microbial food safety hazards. It describes
good agricultural and management prac-
tices for growing, harvesting, washing,
sorting, packing, and transporting most
fruits and vegetables sold to consumers
in fresh or minimally processed form.
"Another focus of the Food Safety Ini-
tiative is to identify and support research
priorities that will fill gaps in food safety
knowledge," Lindsay notes. "We plan to
incorporate the information in a multi-
year research plan."
Since 1997, ARS has increased re-
search efforts to promote the safety of
fruits and vegetables.
"We're concentrating our research at
three different locations: Beltsville, Mary-
land; Wyndmoor, Pennsylvania; and Al-
bany, California," Lindsay says. "This
year alone, we allocated $6.6 million to
eight research projects devoted to en-
hancing the safety of fruits and vegeta-
bles and have requested an additional $2.1
million for fiscal year 2000."
In Beltsville, Maryland, staffing is
being increased, and positive research
results have already been achieved at the
ARS Horticultural Crops Quality Labo-
"We're adding a microbiological safe-
ty team to our research unit," says HCQL
leader Kenneth C. Gross. "It will include
a microbiologist, along with a plant pa-
thologist and a plant physiologist."
This team will help deal with a critical
aspect of food safety: the physiological
and biochemical factors involved in the
interaction among foodborne pathogens,
their fruit and vegetable hosts, and asso-
ciated beneficial microbes, Gross reports.
In the lab, plant pathologist William S.
Conway has already shown that the Lis-
teria monocytogenes bacterium can grow
on fresh-cut apple slices. And controlled-
atmosphere storage had no effect on this
"Most consumers usually eat an apple
whole," Gross says. "The apple peel
serves as a barrier to many foodborne
pathogens. But demand is growing for
fresh-cut produce, a form that is open to
potentially harmful microorganisms."
Cutting produce causes wounds that
pave the way for pathogens to attack.
Gross and col-
leagues arestudying SCOTT BAUER (K8440-1)
tween these patho-
gens and naturally
There is only so
for organisms to
exist on a given
piece of produce-
a case of survival of
the strongest organ-
gist Alley E. Wata-
da at the HCQL lab
found that spinach
pounds and benefi- Plant pathologists W
cial microorgan- Britta Leverentz san
isms that slow down determine survival a
the growth of Liste- borne pathogen List
ria. "It's important
that these helpful organisms not be re-
moved during sanitation treatments after
harvest," Gross says.
HCQL scientists are also looking at
the quality of fruits and vegetables.
"We're continuing our work on ensuring
that we start with the best quality possi-
ble," says Gross. This includes develop-
ing new lines of fruits and vegetables that
store longer and resist pathogens better.
Commodities being studied at HCQL
to bolster their microbial safety include
fresh-cut spinach, celery, carrots, apples,
bananas, sweetpeppers, tomatoes, squash,
strawberries, grapefruit, grapes, plums,
Fruit and vegetable contamination is a
primary concern of food safety research
at ARS' Eastern Regional Research Cen-
ter (ERRC) in Wyndmoor, Pennsylvania.
"Our first priority is to eliminate the
contamination, and we've been very suc-
cessful with irradiation," says Donald W.
Thayer, head of the Food Safety Research
Unit. "Next year, we expect to have a
commercial food ir-
radiator installed in
I food by irradiation
- significantly reduc-
Ses the numbers of
S harmful microor-
ganisms such as E.
S coli, Bacillus cere-
us, L. monocytoge-
aureus. Ionizing ra-
diation is a safe and
effective food pres-
"We used the
ed dose of irradia-
am Conway and tionforfreshfruiton
e fresh-cut apples to raspberries contam-
growth of the food- inated with Cyclo-
monocytogenes. spora," Thayer
says. "Not only did
we inactivate the parasite, we doubled
the berries' shelf life as well."
Thayer and colleagues Kathleen T.
Rajkowski and William F. Fett have
successfully used irradiation and chlor-
ine to kill E. coli 0157:H7 and Salmon-
ella on alfalfa seeds and sprouts.
Since 1995, raw alfalfa sprouts have
been recognized as a source of foodborne
illness in the United States, with several
outbreaks of both E. coli 0157:H7 and
Salmonella. As a result, the FDA and the
Centers for Disease Control and Pre-
vention have advised those at high risk,
namely children, the elderly, and persons
with compromised immune systems, to
avoid eating raw alfalfa sprouts.
Agricultural Research/June 1999
Because of their fragility, sprouts can-
not withstand abrasive physical washing.
So the focus has been on cleaning the
seeds, which are suspected as the source
of the pathogens. U.S. sprout growers are
looking for an effective, practical, and
cost-effective way to ensure that sprouts
are free of pathogenic organisms.
Microbiologists Rajkowski andThay-
er used irradiation to treat alfalfa seeds
and sprouts. "We used a dose approved
for irradiating meat and controlled both
Salmonella and E. coli 0157:H7. The
irradiation also extended the shelf life of
sprouts from about 5 days to more than a
week," Rajkowski reports.
BothE. coli and Salmonella were more
resistant on dry seeds than on sprouts
because of the lack of moisture in the
seeds, although a higher dose of irradia-
tion did kill both pathogens. According
to Thayer, the dose level that eliminated
E. coli had little effect on the germination
of the irradiation-treated seeds. This may
not be true for Salmonella, which needs
a higher dose.
A Chemical Sanitizer
To decontaminate sprouts, Fett, a mi-
crobiologistinERRC's Plant Science and
Technology Unit, has been investigating
an alternative treatment-chemical san-
He subjected alfalfa seeds to 2-per-
cent, 2.5-percent, and 3-percent weight-
per-volume concentrations of calcium
hypochlorite (achlorine source). A 3-per-
cent concentration means about 20,000
parts per million of available chlorine. At
a neutral pH of about 7, Fett got a 99.99-
percent reduction in E. coli 0157:H7 for
the 2.5 and 3 percent concentrations.
"ThepHis important because at a high-
erpH level, such as 10, the chlorine would
change to a form that would not be as
effective in killing bacteria," Fett says.
"And sprouts may be contaminated
internally, which would prevent a sur-
face disinfectant from working effective-
ly," Thayer adds. "Therefore, in practice,
the best way to eliminate pathogens might
be a combination of irradiation and san-
Food technologist Gerald M. Sapers,
also in the Plant Science and Technology
Research Unit, is working with colleagues
Ching-Hsing Liao, Dike Ukuku, and
Bassam Annous to study sanitizing ofpro-
Microbiologists Bill Fett and Kathleen
Rajkowski compare alfalfa sprouts grown
from seeds that have been irradiated to
reduce bacterial pathogens.
duce that has been contaminated with
human pathogens. These include E. coli
0157:H7, Salmonella, andListeria mono-
This team is looking at apple cider and
other fresh-apple products, as well as
fresh-cut fruits and vegetables including
melons and sprouts. Kevin B. Hicks, who
heads the unit, says that they are identify-
ing sources of contamination and exam-
ining the processes that limit the efficacy
of produce washing.
"From these results, we hope to devel-
op ways to prevent contamination, kill or
remove microbial contaminants, or sup-
press their growth on fruits and vegeta-
bles," Hicks says.
"In collaboration with Pennsylvania
State University, we're designing and
building a one-of-a-kind fruit and vege-
table processing research facility at
ERRC. This facility will allows to quick-
ly develop methods to kill or remove
bacteria from fresh fruits and vegetables
in surroundings more reflective of an
industrial setting," says Hicks.
"We feel this is very important, since
we've found that conventional process-
ing equipment and commercial sanitizers
don't seem to be very effective at remov-
ing bacteria from these commodities.
"We'll use commercial-scale convey-
ing, washing, and processing equipment
with our newly developed sanitizing treat-
ments," Hicks says. "Our aim is to help
meet the President's goal of developing
cost-effective ways to reduce the inci-
dence offoodborne illness associated with
fresh and processed produce."-By Doris
Stanley Lowe, ARS.
This research is part of Food Safety,
an ARS National Program described on
the World Wide Web at http://www.
nps. ars. usda. gov/programs/cppvs. htm.
James A. Lindsay is with the USDA-
ARS National Program Staff 5601 Sun-
nyside Ave., Beltsville, MD 20705-5138;
phone (301) 504-4674, fax (301) 504-
5467, e-mail firstname.lastname@example.org.
Kenneth C. Gross is at the USDA-ARS
Horticultural Crops Quality Laborato-
ry, Bldg. 002, 10300 Baltimore Ave.,
Beltsville, MD 20705-2350; phone (301)
504-6128, fax (301) 504-5107, e-mail
Donald W. Thayer is in the USDA-ARS
Food Safety Research Unit, Eastern Re-
gional Research Center, 600 East Mer-
maidLane, Wyndmoor, PA 19038;phone
(215) 233-6582, fax (215) 233-6406, e-
Kevin B. Hicks is in the USDA-ARS
PlantScience and Technology Unit, East-
ern Regional Research Center, 600 East
Mermaid Lane, Wyndmoor, PA 19038;
phone (215) 233-6580, fax (215) 233-
6406, e-mail email@example.com. *
Agricultural Research/June 1999
Chicory Mops Up After Turkey Litter
C hicory may bejust the plant to clean up nutrients leached
from turkey litter compost used to fertilize pastures.
"Turkey litter is the nitrogen- and phosphorus-rich
manure cleaned from turkey houses along with the
wood shavings used as bedding," says agronomist
David P. Belesky. "When spread at high rates, it looks like
chipboard on the ground."
Sometimes, however, there are more nutrients in that litter
than plants can use, and this may pose problems for water qual-
"We're finding that chicory could be biological sponge that
soaks up the excess nitrogen and other nutrients from the soil,"
says Belesky, who is based at ARS' Appalachian Farming
Systems Research Center in Beaver, West Virginia.
For the past 4 years, Belesky and colleagues have been test-
ing three varieties of chicory-Grasslands Puna, Forage Feast,
and Lacerta-on Appalachian pastures. They want to see whether
the chicory can boost cattle and sheep production, as well as
catch excess nutrients and improve marginal soil.
"Chicory has a big taproot, like a parsnip or carrot. This
taproot could break up soil layers that block other roots," says
The taproot may also help the plant go deep for water, which
would explain in part why chicory "stayed green andleafy when
most other pasture plants stopped growing during last year's
hot, dry summer."
Belesky found the chicory could keep soaking up nitrogen
and respond to commercial nitrogen fertilizer application rates
as high as 424 pounds an acre. Now he is testing composted
turkey litter as fertilizer.
The tests are part of a project involving many of the lab's
scientists-with specialties ranging from plant nutrition to
groundwater quality-as well as British United Turkey of
America, a turkey-production firm with breeding operations in
southern West Virginia.
Farmers often stockpile the litter in the fall and apply it to their
fields in spring. Recommended rates are under 3 tons an acre.
The only major problem with chicory grown in mixture with
other pasture plants, Belesky says, is that lambs choose the other
plants before eating chicory.
Lab tests by ARS animal scientist Kenneth E. Turner led him
to speculate that the high amounts of nitrogen mopped up by the
plants might cause a buildup of compounds that temporarily
retard digestive microbes in the lambs' rumens. This concept
hasn't been tested on cattle yet.
ARS chemist Joyce G. Foster is studying the chemical make-
up of the chicory plants to see whether they hold something
objectionable to the lambs.
Since scientists in New Zealand have had success with Puna
chicory grazedby sheep as well as cattle, Belesky suspects climate
plays a role, along with fertilizer and management practices.
ARS hydrologist Douglas G. Boyer is analyzing soil water to
be sure that chicory isn't allowing significant amounts of nitrate
The scientists are also working with USDA's Natural
Resources Conservation Service to test chicory in the Southern
West Virginia Grazinglands Program. They see potential in
chicory to provide forage in summer and increased protein to
improve per-acre production of beef and lamb.-By Don Comis,
This research is part of Grazinglands Management, an ARS
National Program described on the World Wide Web at http://
www.nps.ars. usda.gov/programs/nrsas. htm.
David P. Belesky, Kenneth E. Turner, Joyce G. Foster, and
Douglas G. Boyer are at the USDA-ARS Appalachian Farming
Systems Research Center, 1224AirportRd., Beaver, WV25813-
9423; phone (304) 256-2858, fax (304) 256-2921, e-mail
Agricultural Research/June 1999
. -, - k-'-)ao-l
f you ask Warren Lamboy to send
you Pinot Blanc budwood for plant
breeding or other research, you can
be sure you won't get a Melon in-
stead-a grape called Melon, that is.
As curator of the Agricultural Research
Service's cold-hardy grape collection in
Geneva, New York, Lamboy cleared up
a case of mistaken identity between the
two grape cultivars. And he convinced
himself that DNA fingerprinting will
ensure accurate identification of the 1,300
accessions at Geneva and of a larger ARS
collection of tender, non-cold-hardy
grapes at Davis, California.
"Worldwide, there are some 14,000
grape cultivars and wild types and more
than 50,000 names for these grapes,"
explains Lamboy. "The same grape may
have three or four names. It takes an ex-
pert with at least 10 years of training in
identifying grape cultivars to be able to
tell them apart visually and by measure-
The ARS accessions, Lamboy adds,
are a combination of disparate collections
from U.S. and foreign breeders who've
called the same grapesby differentnames.
"Accurate identification of all these
accessions is essential if the two collec-
tions are to be reliable sources of grape
germplasm," he wrote last year in an ar-
ticle recommending a fingerprinting
method-called Simple Sequence Re-
peats, or SSRs-in theAmerican Journal
ofHorticulturalScience. Most of the SSRs
were originally identified by researchers
at the University of California at Davis.
Lamboy, a geneticist in the Plant Ge-
netic Resources Unit, didn't start off con-
vinced that differences at specific areas
on grape chromosomes would pinpoint
each accession. "I'm a skeptic," he says.
This Concord grape plant was success-
fully regenerated from a bud that had
been cryopreserved in liquid nitrogen
for several months.
KEITH WELLER (K8445-1)
14 Agricultural Research/June 1999
DEEP FREEZE-a Really Big Chill
So Lamboy selected 45 known grape
cultivars from the ARS collection and
from colleagues at the Cornell Expeli l-
ment Station in Geneva, where the ARS
unit is located. He also asked former
Cornell extension agent Dave Peters.-.n
to select several dozen random cultivar\,
from commercial vineyards in the area
but to identify them by number only.
Lamboy says 32 of Peterson's -4-
unknowns found matches among his -45
known cultivars. Twelve didn't
match. Eleven of them, itturned out,
weren't in the original 45; but the
twelfth-a Pinot Blanc-should
"This made us question the Pi-
not Blanc standard," which came
from the collection of Cornell viti-
culturist Bob Pool, Lamboy says.
Pool then told Lamboy that some .'I
experts had identified the standard
as Melon. So Lamboy fingerprint-
ed a known Melon sample from
Pool's collection and got a perfect
"Then I was convinced that DNA
fingerprinting really works," he
It works, Lamboy explains, be-
cause DNA sequences at specific
areas, called loci, along the chro-
mosomes repeat themselves. And
the number of repeats varies by
cultivar. Depending on the locus,
Lamboy has found between 16 and
38 differences in the number of re-
peats. This variation among the
cultivars over five loci yields a very
large number of possible combina-
tions. In fact, the combined statis-
tical powerof all loci allows for only
2 chances in 100 million that any
two accessions would not be distin-
guishable, he says. And that includes w Id
species and hybrids, as well as cultivated
"We can sort out the confusion .of
duplicate names and avoid duplicating
accessions," he says.
Cryopreservation specialist Susan Sheffer at Geneva, New York, is helping to de-
velop a protocol for deep-freezing and recovering grape germplasm in case diseases.
insects, deer, violent weather, or vandals kill the vines growing in the laboratory's
"'Two years ago," says Sheffer, "we lost 400 apple trees to fire blight. Luckily. ever'
one of them was backed up in a liquid nitrogen tank."
Cryopreservation of grapes is more challenging, says Sheffer. who gets guidance
from hercoworkersand from experts at ARS' National Seed Storage Laboratory in Fort
To survive freezing, most of the moisture must be removed from the grape bud-
otherwise, ice crystals form and rupture the cells.
"The cold-hardy grapes are one story."
EmITH VELLER Iba'" II Sheffer says. "They survive dehydration
quite well. But the wine grapes aren't as
tolerant, and a third group can't take de-
hydration at all."
French viticulturists get around this
problem by tissue-culturing the buds both
before and after freezing-a long and la-
bor-intensive process. Sheffer and Lam-
boy want to bypass the first culture.
So far, Sheffer has had good success
dehydrating cold-hardy grapes to about
20-percent moisture. She hopes to find the
secret for dehydrating buds of the tender
wine grapes, most of which are kept at the
Davis, California. germplasm collection.
Recovering the buds after a deep freeze
is another challenge. With apples. much
r : more of the budwood survives dehydra-
tion,explains Lamboy. soitcanbecut and
budded onto rootstock. With grapes, only
.. the li ny growing tip of the bud stays viable
Sheffer uses an outdated dental spoon
donated by her dentist to scoop out the
Apple, grape. and tart cherry buds are tiny, green growing tip from the other ise
cryogenically stored in the vapor phase or dead bud after it has been defrosted and
liquid nitrogen at -185"C (-301F). Here, rehydrated. Most of the buds from thecold-
cryopreservation specialist Susan Sheffer hardy grapes she has %\ worked \\ ith thrive
removes grape buds rrom storage ror in glass jars under gro
regeneration. in glass jars under grow lights.
Sheffer tells visiting schoolchildren,
"When you put apple or grape buds into
liquid nitrogen. it's just like hitting the
"pause' button on the VCR: it puts them into suspended animation. Then. when .ou
bring them up out of the tank. it's like hitting the 'play' button." Her research is geared
to making those transitions successful and efficient.-By Judy McBride, ARS.
Susan M. Sheffer is in the USDA-ARS Plant Genetic Resources Unit. Collier Dr.,
Cornell Universitv, Geneva, NY 14456-0462; phone (315) 787-2359, .far (315) 787-
2339, e-nmail firstname.lastname@example.org. *
Agricultural Research/June 1999
KEITH WELLER (K8443-1)
-4" ', a 1 7..... _\ I -\ I 1 .-' :. ._
Clonal farm manager Bill Srmack prunes grapevines to ensure production of healthy new
canes during the next growing season.
Knowing What's at the Core
Since Lamboy's evaluation of SSRs 3
years ago, he and colleagues have finger-
printed about one-third of the Geneva
grape collection. All 120 accessions of
the core collection, which represents the
genetic breadth of the whole collection,
have been positively identified. "It is one
of the most extensively DNA-fingerprint-
ed collections in the National Plant Germ-
plasm System," Lamboy says.
But he didn't stop there. He expanded
DNA analysis to show how closely relat-
ed the various grape accessions are. Un-
der a cooperative research and develop-
ment agreement with Ernest and Julio
Gallo Winery in Modesto, California,
Lamboy and Gallo researchers adapted
the methods to use Amplified Fragment
Length Polymorphisms, or AFLPs, in
While SSRs positively identify a cul-
tivar from as few as five sites on the grape
chromosomes, AFLPs look at many more
sites-about 300-and show which and
how many sites the cultivars have in com-
He says Gallo will use the method in
its search for grapes that possess resis-
tance to diseases or tolerance to environ-
mental stresses. ARS will use it to man-
age the living grape collections. It will
help Lamboy evaluate the quality of the
current accessions and identify cultivars
that would be useful additions to round
out missing characteristics.
For example, nine different cold-har-
dy grape cultivars have been reported from
the Baltic Republics, says Lamboy.
"AFLPs may help in determining wheth-
er these cultivars carry genes that are not
already present in domestic grapes and so
would be worthwhile additions to the col-
lection."-By Judy McBride, ARS.
This research is part of Plant Micro-
bial and Insect Germplasm, Conserva-
tion and Development, an ARS National
Program described on the World Wide
Web athttp://www.nps. ars. usda. gov/pro-
Warren F. Lamboy is in the USDA-
ARS Plant Genetic Resources Unit, Col-
lier Dr., Cornell University, Geneva, NY
14456-0462; phone (315) 787-2359, fax
(315) 787-2339, e-mail
KEITH WELLER (K8446-1)
To achieve accurate identification of grape cultivars, geneticist Warren Lamboy examines a
computer image of DNA fingerprints from 36 different cold-hardy grape cultivars grown
commercially in the Finger Lakes region of New York.
Agricultural Research/June 1999
in West Africa
In the Cinzanaregion of Mali, West Africa, farm families live
in villages surrounded by their land. Farming is still nonmech-
anized. Animals help till the soil, and manure is the main source
An Agricultural Research Service scientist recently traveled
to West Africa's Sahelian region to learn more about the farming
methods and share his insights on increasing food production.
Plant physiologist Dan Israel, who is in the ARS Soybean and
Nitrogen Fixation Unit at Raleigh, North Carolina, says he
enjoyed visiting farmer Saouti Toure near the Cinzana Research
Station and seeing research being done on his farm in cooper-
ation with a Malian scientist.
"Rock phosphate mined in Mali was being composted with
manure to make the phosphorus more available to millet and
sorghum crops when applied to the soil," he says. "Test plots on
Toure's farm showed this composted mixture increased plant
growth as compared to unfertilized plots."
Improved soil fertility can help crop production, which not
only feeds farm families, but also lets growers sell food to nearby
villages and larger cities such as Bamako and Segou.
Israel's visit was part of a multi-institutional program of the
U.S. Agency for International Development. The 5-year, $5
million project will evaluate soil management and productivity
in many countries.
"The goal of this particular project is to develop computer
software using data from years of soil fertility and plant nutrition
research," says project leader Jot Smyth, who is with North
Carolina State University. "We want to design it so Malian
extension agents and farmers can diagnose barriers to crop yields."
Israel's area of expertise is soybean production. In particular,
he studies how nodules on soybeans convert nitrogen from the
air to a form that the plants can use for growth in the process of
Cowpeas, the principle protein-source crop in the Cinzana
region, also fix nitrogen in this way. During his visit, Israel
evaluated the effect of phosphorus deficiency and soil acidity on
nodule health. A pink to reddish-brown nodule interior means
good nitrogen fixation, for example.
"The fields in Mali could yield more with extra fertilizer, but
water availability will set the limit on how much yield improve-
ment can be realized from the fertilizer," says Israel. "We want
to develop a software program adaptable to a range of environ-
ments and yield potentials."
In the final stages of this project, sociologist Frank Smith,
who is with North Carolina State, will evaluate its impact by
surveying Cinzana extension agents and farmers about what
they found most useful about the software program.-By Jill
This research is part of Improving Plant Biological and
Molecular Processes, an ARS National Program described on
the World Wide Web athttp://www.nps.ars. usda.gov/programs/
Daniel W. Israel is in the USDA-ARS Soybean and Nitrogen
Fixation Research Unit, 4114 Williams Hall, North Carolina
State University, Raleigh, NC 27695-7620; phone (919) 513-
3031, fax (919) 515-2167, e-mail email@example.com.*
Plant physiologist Dan Israel (left) and Cinzana Research Station
staff in Mali, West Africa, collect cowpea root samples to see the
effects of phosphorus fertilization and lime applications on the
number and size of nitrogen-fixing root nodules.
Agricultural Research/June 1999
head scab wreaks havoc some-
where in America.
Scab now ranks as the worst
plant disease to hit the United
States since the stem rust of the 1950s. In
the past decade, outbreaks in Illinois,
Indiana, Michigan, Minnesota, North
Dakota, Ohio, and South Dakota have led
to more than $1 billion in crop losses.
Caused by a fungus known as Fusar-
ium graminearum, scab gets its name from
the whitish-gray lesions that form on the
kernel-bearing portion, orhead, of infect-
ed wheat or barley plants. The Fusarium
microbe can also cause root, stalk, and
ear rots in corn.
Infected wheat kernels often shrivel
and become discolored, and they may
harbor compounds called mycotoxins that
are manufactured by the fungus. Most
notable of these natural compounds is
deoxynivalenol, which can make wheat
unsuitable for flour or cereals and too toxic
for sale as animal feed.
Today, Agricultural Research Service
scientists at a half-dozen laboratories
around the United States are exploring an
array of tactics to thwart the fungus.
Deactivating the Toxin
One defensive strategy relies on ex-
ploiting the mechanism apparently used
by F. sporotrichioides, a relative of F.
graminearum, to protect itself from its
own toxin, known as T-2.
"Because both of these Fusarium
species produce toxins the same way,"
explains ARS microbiologist Nancy J.
Alexander, "the process they use to
deactivate those toxins may also be
Alexander and colleagues with ARS
at Peoria, Illinois, found-in F. sporotri-
chioides-a T-2 resistance gene that they
"This gene," says Alexander, "cues the
fungus to make an enzyme that alters the
structure of the toxin. The enzyme does
this by placing a protective chemical
group on the toxin. The altered toxin
apparently can't harm the fungus.
"Equipping wheat and barley plants
with a gene to deactivate the toxin made
by the scab fungus, F. graminearum,
might give the plants a new and powerful
form of protection."
Expelling the Toxin
Another organism in nature-the Sac-
charomyces cerevisiae yeast used in
breadmaking-has a gene called PDR5
that can pump toxins out of its cells.
Alexander and co-researchers borrowed
.IAfK VKINrA IKt A7.-1n
Geneticist Ann Blechl looks at root growth
on genetically engineered wheat plants that
may carry new genes for resistance to
PDR5 from scientists at The Catholic
University of America in Washington,
D.C. They rebuilt it to work in plants.
Now, ARS colleagues in Fargo, North
Dakota, are moving PDR5 and TRI-R into
barley, while co-workers in Albany, Cal-
ifornia, are transferring the genes into
ARS geneticist Lynn S. Dahleen at
Fargo has some healthy plants with the
TRI-R gene working inside and others that
boast the PDR5 gene. "Now our goal,"
says Dahleen, "is to get both genes up and
running in the same barley plant-pref-
erably one that's either a commercial
variety or at least similar to a commercial
One target of Dahleen's experiments:
MNBrite, a commercial barley from the
University of Minnesota. The North Da-
kota Barley Council is financing some of
A handful of wheat plants nurtured in
an Albany lab and greenhouse are also
now outfitted with either the PDR5 or
TRI-R gene. Ann E. Blechl and Patricia
A. Okubara at Albany used a gene gun, or
bioblaster, to propel gold particles coated
with these genes into wheat cells. Fusar-
ium-resistance testing will follow. The
North American Millers Association is
funding part of this research.
Proteins To Knock Fusarium Out
Blechl and Okubara are also examin-
ing wheat genes that may knock out the
In tests elsewhere, proteins produced
on command by these genes hindered still
another F. graminearum relative, F. oxy-
sporum. A scientist at the University of
Zurich provided one of these experimen-
tal genes. It tells plants to make what's
known as a thaumatin-like protein. A
second gene, isolated by Kent F. McCue
at the Albany center, directs plants to
produce a protein called purothionin.
Another protein in the thionin fami-
ly-hordothionin-is a target of research
by ARS scientists and their colleagues in
ARS molecular biologist Ronald W.
Skadsen says, "We think hordothionin
and another protein, permatin, may play
a role in keeping Fusarium from gaining
a foothold in barley kernels." Skadsen
and colleagues cloned two genes that
barley plants use to make the proteins.
"In barley," Skadsen says, "these pro-
teins are found only inside the kernel.
We're hoping to rebuild the genes so that
Agricultural Research/June 1999
Lighler. diwcolored harle) heads are
intected ti ili fi'unrrarm head cauh fungi.
Agricultural Research/June 1999
plants will produce the proteins on leaf-
like structures that surround the kernel,
where Fusarium can begin its attack."
The American Malting Barley Asso-
ciation and the North American Barley
Genome Mapping Project help fund the
Help From a Wild Relative
A wheat cousin called wild emmer has
resistance genes thatmightbe moved into
domesticated wheat. Emmer is a relative
of durum wheat, which is used to make
flour for pasta and for pizza doughs.
North Dakota State University re-
searchers, along with ARS plant pathol-
ogist James D. Miller and ARS geneti-
cists Leonard R. Joppa and Norman D.
Williams at Fargo, are crossing emmer
with domesticated durum wheats. The
work gets some support from grants from
the Agricultural Production and Utiliza-
tion Committee of North Dakota, North
Dakota Wheat Commission, and U.S.Du-
rum Growers Association.
In other experiments, they are cross-
ing wild emmer with special wheats called
"Aneuploids are invaluable to us," says
Williams, "because they take up individ-
ual emmer chromosomes intact. That
makes it easier to find which emmer chro-
mosome contains a resistance gene. Once
we locate that chromosome, we may be
able to pinpoint the location of the resis-
tance gene on it-or at least that of an
associated marker gene."
Markers Tell Us Where It's At
A marker gene is a sequence of DNA
that acts somewhat like a signpost to in-
dicate the presence of a gene of interest.
"When we find wheat-emmer hybrids that
have a resistance gene or marker," Wil-
liams says, "we can select the best of these
plants for further breeding."
"The more scab-resistance markers
scientists can identify," says geneticist
James A. Anderson, "the closer we should
all come to locating the actual resistance
genes that we're seeking." Anderson,
formerly with ARS at Pullman, Washing-
ton, and now with the University of Min-
nesota at St. Paul, is among the first to find
a scab-resistance marker in wheat.
He did the work with researchers at
North Dakota State University. The re-
Geneticist Robert Busch examines a newly
developed, high-yielding, scab-tolerant
spring wheat variety.
search was funded by a USDA National
Research Initiative Grant, the North
American Millers Association, and the
North Dakota State University Research
In all, the team discovered five mark-
ers. They crossed a scab-resistant wheat
from China, called Sumai 3, with a mod-
erately susceptible variety, called Stoa,
from North Dakota. Then they examined
"We chose a Chinese variety as one of
the parents," says Anderson, "because
some Chinese wheats appear to have the
best natural resistance."
The researchers located markers for
two genes that, Anderson says, "seem to
have significant impact on scab resis-
tance. The three other markers indicate
genes that make minor contributions."
Other promising markers have been
discovered by scientists with the Univer-
sity of Illinois at Urbana, working with
ARS molecular biologists Guihua Bai-
now at Peoria-and Leslie L. Domier at
Urbana. They crossed Ning 7840, a scab-
resistant Chinese wheat, with Clark, a
susceptible variety developed in Indiana.
"One marker," says Bai, "is linked to
a gene that may account for up to 50 per-
cent of the scab resistance. Several other
markers are for two minor genes that may
account for another 20 percent of the re-
Further research may reveal other new
markers linked to different resistance
genes. "Resistance from different genetic
sources," says Bai, "is the best option,
because it will give breeders a larger pool
from which to develop new varieties for
Screening for Resistance
The best-performing plants from these
and other experiments may make their
way to the Uniform Regional Scab Nurs-
ery, rigorous program of scab-resistance
screening of new wheats for the upper
Midwest. ARS plant geneticist Robert H.
Busch, who is at St. Paul, coordinates the
nursery, helping breeders field-test can-
Previously, Busch helped oversee dis-
tribution of USDA funds for scab-resis-
tance research at ARS labs and universi-
Agricultural Research/June 1999
ties nationwide. This year those funds to-
taled $3.5 million.
In his own breeding research, Busch
develops scab-tolerant wheats for the
upper Midwest, including one he is re-
leasing this year. "Through both conven-
He links a gene he is testing for scab
resistance to another gene that cues plants
to make anthocyanin, a natural pigment
that gives fall leaves theirred colors. After
the genes are shot into plant tissue, cells
with the anthocyanin gene turn red. This
Plant physiologist William Bushnell and technician Tessa Goff examine a computerized
image of red barley cells expressing antifungal genes shot into barley tissues.
tional breeding and biotechnology,"
Busch says, "we expect to be able to offer
high-yielding wheats with even more scab
resistance in the future."
Some of the other new wheats and
barleys for the upper Midwest might con-
tain genes discovered or rebuilt by
Busch's ARS colleagues at St. Paul.
William R. Bushnell, for example, is
developing a faster, less expensive test to
determine if experimental scab-resistance
genes can help cells foil Fusarium.
means they have likely taken up the gene
for possible scab resistance, as well.
When the tissue is inoculated with
Fusarium and monitored under a micro-
scope, the distinctive color makes it fast-
er and easier to pinpoint these key cells.
In addition to giving plants new, more
powerful genes to boost scab resistance,
scientists are scrutinizing about 700 mi-
crobes for their potential to serve as bio-
hih-ildngweas ih ve ioe cb essane
Agricultural Research/June 1999
logical controls of the fungus.
ARS plant pathologist David A.
Schisler at Peoria and colleagues at Ohio
State University are testing the microbes
for their ability to gobble up two com-
pounds naturally present on wheat heads
when Fusarium strikes. The compounds
are choline and betaine. They nourish the
fungus as it grows from the male organs
of wheat flowers-where it sometimes
lands-to where it can infect the devel-
oping kernel deeper inside the flower.
Says Schisler, "We are also perfecting
a liquid fermentation medium to econom-
ically produce the most effective mi-
crobes." The medium could be sprayed
on wheat during flowering.
Other new tactics for outflanking the
Fusarium fungi might come from sleuth-
ing the microbe's development. To stalk
the fungus, former Peoria microbiologist
Thomas M. Hohn borrowed a gene from
a bioluminescent jellyfish, Aequorea
victoria, and hooked it to the fungus.
Thejellyfish gene causes the fungus to
glow a telltale green when fungal-infected
tissues are exposed to fluorescent light.
Though the idea ofusing thejellyfish gene
in lab experiments isn't new, Hohn was
apparently the first to use it for spying on
"This innovative pairing of jellyfish
and Fusarium," says molecular biologist
Skadsen, "should shed new light on the
biology of this destructive fungus."-By
Marcia Wood, Don Comis, Ben Hardin,
Linda McGraw, and Kathryn Barry
This research is part of Plant Diseas-
es, an ARS National Program described
on the World Wide Web at http://
Contact scientists mentioned in this
Marcia Wood, phone (510) 559-6070,
fax (510) 559-5882, e-mail
Don Comis, phone (301) 504-1625,fax
(301) 504-1641, e-mail
Se + Su rose
Ne Liui Epoxies
ugar is still a favorite sweetener
for drinks, desserts, and other
foods, but artificial sweeteners
are nibbling on its piece of the
If the nation's sugar producers are
dismayed by such prospects, they may
find solace in a new advance in polymer
science. By changing sugar's molecular
structure, scientists have created power-
ful liquid epoxies that bind concrete,
wood, metals, plastics, and other ma-
"Once these epoxies set, they become
a clear, glassy or rubbery material, de-
pending on the type used," says chemist
Navzer D. Sachinvala of USDA's Agri-
cultural Research Service.
Preliminary studies suggest a range of
potential applications-from primers,
base coatings, and adhesives to compos-
ite materials like particle board and boat
It's too soon to say how epoxy resins
might fare versus petroleum-based prod-
ucts. But epoxies have some compelling
selling points, such as a tenacious grip on
different materials and a range of curing
And unlike today's petroleum prod-
ucts, the sucrose epoxies don't contain
ingredients like bisphenol-A. Some sci-
entists worry that this chemical may dis-
ruptthe endocrine systems of animals such
as mice-and possibly humans-notes
Morton Litt, a Case Western Reserve Uni-
versity professor in Cleveland, Ohio.
Sucrose also proffers a handy, domes-
tic source of raw material, compliments
of sugarcane industries in Florida, Loui-
siana, Texas, and Hawaii. Together they
produce about 3.8 million tons of sugar
annually. Only about 2 percent is used for
"It's the purest, most versatile organic
compound you can find, and yet it has
SCOTT RAUFR (K84f7-1n
lak ImW AI
By changing the molecular structure of
sugar, scientists can make it into a power-
ful liquid epoxy that binds concrete, wood,
metals, plastics, and other materials.
Chemist Navzer Sachinvala demonstrates
some of the raw materials and the sucrose-
based epoxies used.
only one major commercial use: food,"
He first began exploring its industrial
potential in 1988, along withLittand other
colleagues at what is now the Hawaii Ag-
ricultural Research Center on Oahu.
Initially, they tried developing nylons,
polyesters, andpolyethers, but"they were
difficult and expensive to make from
sucrose," says Sachinvala. Then they tried
making the epoxies from what are called
allyl- and crotyl-substituted sucroses.
Despite difficulties, success finally came
with the use of common reagents, like
oxygenated vinegar, and a reliable meth-
od of controlling a critical step called ep-
In October 1998, they published re-
search results in the Journal of Polymer
Science comparing crotyl and allyl su-
crose epoxies with the petroleum product
diglycidyl ether of bisphenol-A, or DGE-
BA. The bonding strength of the crotyls
proved superior to both the allyl and
DGEBA epoxies-the latter by 30 per-
cent. In fact, in tests, it took over 1,000
pounds of force to separate two small,
aluminum plates (4" x 1" x 0.044") coat-
ed with the crotyl material.
Since publishing, the scientists have
refined the epoxy-making process, im-
proving its efficiency and environmental
friendliness. What's left over are byprod-
ucts like salt and vinegar.
Under a cooperative agreement, the
scientists are transferring the sucrose tech-
nology to Cajun Materials Group, Inc.
(CMGI), a business consortium in New
The aim is to produce large amounts of
epoxy material so its commercial poten-
tial can be determined in a market dom-
inated by petroleum-based products.
Acadia Board Co., aCMGI affiliate, hopes
to use the epoxies and crushed plant fibers
to create composite material for home
Such collaboration, Sachinvala says,
will help gauge commercial factors of
price, performance, and advantage over
existing materials. All could foretell
whether big things come from the Bayou
country-and whether sugar rises above
its sweetener status.-By Jan Suszkiw,
This research is part of New Uses,
Quality, and Marketabilty ofPlant Prod-
ucts, anARSNationalProgram described
on the World Wide Web at http://
Navzer D. Sachinvala is at the USDA-
ARS Southern Regional Research Cen-
ter, 1100 Robert E. Lee Blvd., New Or-
leans, LA 70124; phone (504) 286-4324,
fax (504) 286-4271, e-mail
Agricultural Research/June 1999
New Corn Highly Resistant
A new corn line from ARS is the best
yet at naturally fending off aflatoxin, a
fungal toxin that can be a threat to food
and feed safety. Commercial corn hybrids
with strong aflatoxin resistance are not
now available. But as an important step
toward this goal, ARS released the new
line, named Mp715, to seed companies
and public research institutions. In field
tests, Mp715 had lower levels of both
fungal infection and aflatoxin contami-
nation. Both qualities likely represent the
most efficient and reliable way to reduce
aflatoxin in corn grain.
The ARS researchers are attempting
to identify the genes responsible. Under
cooperative research and development
agreements, ARS scientists plan to eval-
uate 75 to 100 hybrids from the breeding
programs of two seed companies this
summer. Some companies have already
incorporated in their breeding programs
toxin-resistant germplasm that ARS re-
Aflatoxin is produced by certain spe-
cies of Aspergillus fungi. Last year, corn
aflatoxinlevels soared in parts of the South
because of record heat and drought. Grow-
ers in Texas, Louisiana, and Mississippi
experienced losses estimated at $85 mil-
lion to $100 million. W. Paul Williams,
USDA-ARS Corn Host Plant Resistance
Research Unit, Mississippi State, Missis-
sippi; phone (601) 325-2735, e-mail
pwilliams @ dorman.msstate. edu.
Genetic Test Readied for Pig
A faster, more reliable test may be on
the way for a pig disease that costs U.S.
pork producers $17 million in lost weight
and delays to market. Two toxin-produc-
ing bacteria, Bordetella bronchiseptica
and Pasteurella multocida, are the cul-
prits in atrophic rhinitis. Current diag-
nostic methods take 5 to 7 days and aren't
always reliable. The new testtakes 3 days.
Since the disease spreads quickly in swine
confinement houses, detecting the bacte-
ria sooner could cut losses.
The new test uses probes made from
genetic material of the two bacteria. The
probes target genes found only in one or
the other of the two microbes in samples
taken from swine. For the test, bacteria
cultured from nasal or tonsil swabs from
a live pig are placed on a thin nylon sheet,
which is subsequently treated with the
probes. If B. bronchiseptica is present, a
pink color will appear; if P. multocida,
purple. Karen B. Register, USDA-ARS
National Animal Disease Center, Ames,
Iowa; phone (515) 239-8275, e-mail
Enzyme Discovery May Help
Plants and People
In plants and people, porphyrins are
crucial natural pigments-but trouble-
some if present in excess. In plants, por-
phyrins are precursors of chlorophylls
important to photosynthesis. In animals,
including humans, porphyrins carry ox-
ygen through the blood. Recently, re-
searchers with ARS andDartmouth Med-
ical School found out how some plants
may regulate porphyrins. They also dis-
covered a natural plant enzyme that deac-
tivates these molecules. The findings
could someday lead to protection for
people as well as crops.
In plants, chlorophylls convert the
sun's light into food. Some herbicides kill
weeds by disrupting the manufacture of
chlorophyll. Porphyrins then accumulate
to high levels, making the weeds fatally
hypersensitive to light. But such herbi-
cides may also damage crops in the same
field. A potential solution: develop crops
with high levels of the deactivating en-
The discovery may also lead to new
ways to treat porphyria. In people with
this genetic disease, cells don't properly
turn porphyrins into heme, the deep-red,
iron-rich component of hemoglobin.
Adverse effects can include weakness,
nausea, skin rash, and hypersensitivity to
light. Franck E. Dayan, USDA-ARS Nat-
ural Products Utilization Research Unit,
Oxford, Mississippi; phone (601) 232-
on Peanuts-for Goats
A recent study done for USDA's Ag-
ricultural Marketing Service shows goat
meat stands to pick up in the marketplace
because of the United States' increasing
cultural diversity. Now, scientists have
found that forage peanuts could make a
nutritious fall pasture for goats in many
areas of the Gulf Coast region. For goats,
the plants aren't grown for their nuts, but
fornutrients in theirleaves. Scientists with
ARS and Georgia's Fort Valley State
University used near infrared spectrom-
etry to show that forage peanut plants are
about equal to alfalfa-the usual goat
forage-in nutritional value. In fact, goats
may actually prefer peanut plants to al-
falfa during the fall breeding season. The
results suggest that setting aside some
peanuts for pasture might be a profitable
option. Fort Valley State operates a com-
prehensive program to develop profitable
year-round goat grazing systems. William
R. Windham, USDA-ARS Richard B.
Russell Agricultural Research Center,
Athens, Georgia; phone (706) 546-3513,
Tom Terrill, Fort Valley State Univer-
sity, Fort Valley, Georgia; phone (912)
Agricultural Research/June 1999
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