Group Title: Agricultural research (Washington, D.C.)
Title: Agricultural research
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Title: Agricultural research
Uniform Title: Agricultural research (Washington, D.C.)
Physical Description: v. : ill. ; 25-28 cm.
Language: English
Creator: United States -- Science and Education Administration
United States -- Agricultural Research Administration
United States -- Agricultural Research Service
Publisher: Science and Education Administration, U.S. Dept. of Agriculture :
Science and Education Administration, U.S. Dept. of Agriculture :
Supt. of Docs., U.S. G.P.O., distributor
Place of Publication: Washington D.C
Publication Date: July 1998
Frequency: monthly[1989-]
bimonthly[ former jan./feb.-may/june 1953]
monthly[ former july 1953-198]
Subject: Agriculture -- Periodicals   ( lcsh )
Agriculture -- Research -- Periodicals   ( lcsh )
Agriculture -- Periodicals -- United States   ( lcsh )
Agriculture -- Research -- Periodicals -- United States   ( lcsh )
Genre: federal government publication   ( marcgt )
periodical   ( marcgt )
Statement of Responsibility: U.S. Department of Agriculture.
Dates or Sequential Designation: Began with vol. 1, no. 1 (Jan. 1953).
Issuing Body: Vols. for Jan./Feb.-Nov. 1953 issued by: Agricultural Research Administration; Dec. 1953-<Sept. 1976> by: Agricultural Research Service; <June 1979>-June 1981 by: the Science and Education Administration; July 1981- by: the Agricultural Research Service.
General Note: Description based on: Vol. 27, no. 7 (Jan. 1979).
General Note: Latest issue consulted: Vol. 46, no. 8 (Aug. 1998).
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Bibliographic ID: UF00074949
Volume ID: VID00018
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - ABP6986
oclc - 01478561
alephbibnum - 000271150
lccn - agr53000137
issn - 0002-161X

Full Text

i r' .F~





New Ways for an
Ancient Science
Long before the world knew of
science in the modern sense, there
was husbandry-the scientific control
and management of a specified
branch of farming-at least in the
production of livestock.
Remains of domesticated cattle
dating to 6,500 years B.C. have been
found in Turkey, but some experts
say domestication of cattle may reach
back 100 centuries. And wherever
there are domesticated livestock,
there is someone who's worrying and
thinking and planning to improve
those animals' reproduction.
That's because, for the livestock
producer, reproduction means pay-
days. Whether the end commodity is
meat or milk-or muscle power for
the farm-all the hard work and
tender care ultimately come to naught
if the herd doesn't reproduce.
For a function that animals have
long been doing naturally, breeding
can be remarkably fraught with
difficulties. Big bulls can mean big,
strapping calves-but that can also
translate to calving difficulty.
And though twin calves would
appear to be a double payoff, more
than a third of calvings involving
twins need human assistance for a
successful outcome, compared with
only 15 to 20 percent of single-calf
births. According to Agricultural
Research Service scientists at the
U.S. Meat Animal Research Center at
Clay Center, Nebraska, cows carrying
multiple calves may take longer to
rebreed under typical production
systems. That's because the fetuses
don't leave enough room in the cow's
body cavity for a full stomach of the
normal low-energy diet needed to
attain the physical condition to re-
breed quickly.
To improve the livestock breeding
odds for agricultural producers, ARS

scientists have been pushing the
edges of scientific knowledge for
One of their most remarkable
advances of recent times was devel-
opment of technology at Beltsville,
Maryland, that makes it possible to
sort livestock sperm based on their
chromosomal content-X versus Y.
Y-chromosome sperm result in male
offspring, while X-chromosome
sperm promote females.
Why would farmers care about
gender, as long as their herds get
For the dairy farmer, milk's the
thing-and a cow that delivers a male
calf has paid for her year of feed and
veterinary care with an animal that's
not going to contribute a drop to the
dairy's milk output. Beef farmers, on
the other hand, are more likely to
want male calves because, pound for
pound, males grow faster than
females on the same amount of feed.
Recently, ARS scientists at
Beltsville announced advances in the
cryopreservation of pig embryos-a
major step forward in making swine
with important genetic traits available
to breeders worldwide.
The meat industry has been
routinely cryopreserving embryos of
various livestock species-especially
cattle-since the mid-1980s. But
conventional freezing methods won't
work for pig embryos, which are
extremely sensitive to slow cooling
below temperatures around 590F. As
they cool, pig embryos undergo
physiological and structural changes
that leave them incapable of normal
So ARS scientists are using a rapid
cooling process called vitrification
that is thought to outrace the damag-
ing effects of slow cooling. They
have increased the cryopreserved pig
embryo survival rate to more than 80
percent in the laboratory. [See
"Vitrification Keeps Pig Embryos

Viable," Agricultural Research,
March 1998, pp. 19-20.]
Up-to-date information is crucial
for helping producers get the best
results from their livestock breeding
efforts. That's why ARS scientists at
Beltsville recently doubled the
frequency of their reports evaluating
dairy breeding animals. The reports
show which have outstanding milk
yield, milk composition, and other
valuable traits. That's vital news for
farmers as well as businesses special-
izing in artificial insemination and
embryo transfer. Thanks to this
increased reporting from ARS, dairy
farmers can now pinpoint the best
bulls and calves 3 months sooner.
At Clay Center, ARS scientists
have reported findings from a 4-year
study that indicate cattle producers
can pay particular attention to
birthing ease when selecting breeding
animals, without giving up larger
calves later on. In the study, calving
assistance was required 24 percent
less frequently among young cows
selected on the basis of ancestral
records for calving ease dating back
to 1978. One good indicator of
calving ease: lower birth weights of
calves. But while the average birth
weight of calves born to easy-calving
2-year-olds was 6.6 pounds lighter
than calves from unselected breeding
lines, yearling weight wasn't affect-
ed, the scientists report.
As the past year's headlines about
Dolly, the cloned Scottish sheep,
have proved, advances in reproduc-
tive technology are big news. ARS
scientists nationwide are working
hard to turn their reproductive
research advances into "news you
can use" for America's livestock

Caird E. Rexroad, Jr.
Associate Deputy Administrator
Animal Production, Product Value,
and Safety

Agricultural Research/July 1998

Jul\ 1,)9s
Vol 46, No 7
ISSN 0002-161X

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Agricultural Research

Spotting Top-Notch Toms 4

Tactics Simplify Wasp-Rearing 8

Setting the Stage To Screen Biocontrol Fungi 10

A Prize Pinto, a Better Bean 11

Cah Marker Gene Aids Plant Transformations 12

Watch Out, Soft-Bodied Pests! 14

Better Diets for Dairy Cows 1 6

Testing for Natural Aflatoxin Inhibitors 17

Toppling Tall Whitetop 18

Heads-Up for Soybean Rust 20

No Ants Allowed! 20

Induced Heat Resistance in E. Coli 21

Model Helps Time Pest Fumigation 21

Science Update 22

Cover: At the ARS Germplasm and Gamete Physiology Laboratory in
Beltsville, Maryland, researchers focus on improving turkey reproduction.
Here, poultry physiologist Ann Donoghue candles turkey eggs to identify
fertile ones. Photo by Keith Weller. (K8093-3)

In the next issue!

' Coming soon to a farm near you: Six- and eight-legged
creatures will arrive in flying saucers and fan out to devour or
otherwise kill their living prey. It's the Aerodynamic Transport
Body, a.k.a. Bugslinger.

(' A natural organism known to occur in the hives of healthy
bees may hold the key to protecting domesticated honey bees
from one of their worst enemies-chalkbrood.

(' Microwave ovens deserve their reputation for making food
preparation easier and faster. In the future, microwave technology
may play a taste-tester role for fresh fruits and vegetables as well.

Agricultural Research/July 1998

How Researchers Are Revolutionizing Turkey Production


Agricultural Research/July 1998

-: .t"r

'"~li:~ ~~*'




Lincoln first proclaimed the
last Thursday of November
an official day for giving
thanks, Thanksgiving has been
synonymous with turkeys.
In recent years, other things have
almost become icons of the day:
football games, family gatherings,
travel, and, of course, leftovers. But
while alterations to the Thanksgiving
menu have been relatively minor
through the years, how the traditional
main course-turkey-gets to our
tables has changed significantly.
The Pilgrims had to stalk their
entree through the wild. Today's
production is considerably more high
tech. It has to be, to supply the 4.7
billion pounds of turkey that U.S.
consumers eat every year-a rate of
nearly 18 pounds per person.
Researchers with the Agricultural
Research Service in Beltsville,
Maryland-birthplace of the historic
Beltsville Small White turkey-are
helping producers keep pace with this
demand and the challenges it poses.
At the ARS Germplasm and Gamete
Physiology Laboratory, the focus is
on improving the reproductive
efficiency of turkeys and reducing
the problems commercial producers
face with turkey fertility and egg
A major contributing factor to
turkey mating woes is that today's
commercial turkey doesn't look
much like its early American coun-
terpart, or even its World War II-era
ancestor. With advances in genetic
selection, adult turkey males, or
toms, can weigh up to 85 pounds,
whereas a hen weighs around 20
pounds when she begins to lay eggs.
This size difference makes natural
mating difficult.
The weight imbalance-plus low
fertility of heavy, broad-breasted
turkey lines-has prompted almost
complete integration of artificial

insemination into commercial
"Essentially 100 percent of the
nearly 300 million turkeys produced
annually in the United States for con-
sumption are the result of artificial
insemination," notes ARS poultry
physiologist Ann M. Donoghue, who
leads turkey reproductive studies at
the Beltsville lab.

Development of the Beltsville Poultry
Semen Extender allowed turkey semen to
remain viable for up to 24 hours after

Given the importance of artificial
insemination to turkey production, a
modern grower might be forgiven for
thinking such research achievements
overshadow even development of the
Beltsville Small White.

A Breakthrough Six Decades Ago
In the 1930s, Beltsville-based
researchers William Burrows and
Joseph Quinn reported groundbreak-
ing methods for semen collection and
artificial insemination for poultry.

Agricultural Research/July 1998

Those methods are still used today,
with a few modifications.
In another advance, in the 1970s,
physiologist Thomas J. Sexton
developed the Beltsville Poultry
Semen Extender-a solution that
dilutes and preserves the sperm
outside of the bird's body-that is
sold by commercial companies and
used worldwide. Sexton is now
director of the Beltsville Agricultural
Research Center's Livestock and
Poultry Sciences Institute.
Donoghue says artificial insemina-
tion of turkeys is considerably more
efficient than natural mating, given
the sheer number of hens that need to
be inseminated. Another plus: With
artificial insemination, fewer toms
are needed to keep hens producing
fertile eggs. Donoghue says the
necessary ratio of toms to hens
decreases from 1 to 10 with natural
mating to 1 to 30 with artificial
"Artificial insemination in the
turkey industry is a very well-
established practice," Donoghue
"Yet the potential for using this
method to select toms that can
produce offspring has not been
realized. As for managing fertility,
there is no test for evaluating semen
quickly that is practical for routine
use on commercial farms and corre-
lates reliably with fertility."
Unlike other production animal
systems-dairy cattle, for instance-
where artificial insemination is well
established, evaluation of individual
males in the turkey industry is
limited to visual checks of semen
color, volume, and concentration of
sperm-if evaluation is done at all.
The ability to accurately pinpoint sire
potential would have tremendous
benefits in improved breeding
efficiency of turkeys.
"We generally have anywhere
from 80,000 to 100,000 hens at our


hatchery that are artificially insemi-
nated," says Lynn Bagley, director of
technical services at the Tarhill
Turkey Hatchery in Raeford, North
Carolina. "We use thousands of toms
to inseminate the hens. We have a
few tests to tell whether or not the
semen collected is normal or
abnormal, but they're very labor

Good Tom or Bad?
How does one spot a highly fertile
tom? Donoghue hopes to find the
Most of her research focuses on
evaluating semen quality and sperm
function and on improving preserva-
tion once the semen is collected. She
and collaborators are using a tech-
nique that compares the swimming
ability of each tom's sperm.
"We've been trying to understand
how sperm quality differs between
individual males and how this may
affect them as potential sires," she

Large White turkey male.

Microscopic examination will enable
physiologist Laura King to see if a freshly
laid egg was fertilized. Any holes made by
sperm will show up in a section (stained for
viewing) taken from the surface layer
surrounding the yolk in the area just over
the germinal disc.

"The sperm motility test enables
us to objectively measure how well
sperm from each male can swim in a
solution at body temperature, possi-
bly mimicking the environment in
the hen's reproductive tract."
Animal physiologist David P.
Froman of Oregon State University
originally developed the test for
chickens and, with Donoghue, modi-
fied it for use in studying turkeys.

"The basis of this test isn't
anything new, but we used old ideas
in a new way to study the motility of
sperm cell populations," says
"Based on studies on turkeys, we
found the new information can be
used to identify males that are very
fertile-or not," she says.
"In the past, most-if not all-
semen evaluation tests have been

much more effective at picking losers
rather than winners. This test does
The test could improve the effi-
ciency of picking the best toms,
resulting in more fertile eggs with
fewer sires. Donoghue and col-
leagues, with the support of the U.S.
Egg and Poultry Association, are
planning to take the test to the field
for trials in cooperation with the
turkey industry.
Since artificial insemination
typically involves collecting semen
from all toms in a breeder flock, a
readily detectable sperm trait
strongly associated with fertility
could be incorporated into breeder
tom management fairly easily. The
new sperm motility test is inex-
pensive, quick, and objective. It
requires minimal knowledge or
training to perform and could easily
be adapted for commercial farm use,
according to Donoghue.
"Males with the trait for fast-
moving sperm carry that trait through
time," she points out. "If the tom is
good today, he'll be good tomorrow."
In addition to being able to classi-
fy toms as winners or losers, it is also
important to understand why and
how their sperm differ. By under-
standing which physiological charac-
teristics influence fertility, sperm

from toms classified as losers could
potentially be improved.

See How They Swim
Using a computer-assisted sperm
analysis system (CASA), Donoghue
and colleagues have expanded the
knowledge of motility characteristics
from different toms' sperm.
CASA tracks and records
information as the sperm move

Agricultural Research/July 1998

across a microscope field. Using a
computer to capture the data, several
hundred sperm tracks from an indi-
vidual tom can be analyzed.
Scientists in Donoghue's lab have
evaluated hundreds of toms using the
sperm motility test and CASA.
They found that sperm velocity
parameters were consistently higher
for toms ranked high by the motility
test than for toms ranked lower.
These parameters are a way of
measuring how fast and in what
direction the sperm are moving.
Studies are in progress to learn why
sperm differ in these characteristics.
The scientists are also trying to
determine if additives to sperm-
such as caffeine, which has been
shown to influence sperm motility in
other species-affect sperm from
turkeys classified as winners and
losers differently.
"Sperm from up to 10 to 15 males
are usually pooled for artificial in-
semination into hens," says Dono-
ghue. "It is generally assumed that
sperm from all toms are going to pro-
duce similar numbers of offspring,
but this is not always the case. Some
toms may produce offspring and
some may not. So from an economi-
cal and practical standpoint, knowing
which males' sperm can fertilize eggs
and produce offspring is important."

Donoghue, in collaboration with
Tuskegee University scientist Ed-
ward J. Smith in Alabama and ARS
poultry physiologist Murray R. Bakst
in Beltsville, inseminated hens with
semen from multiple toms and then
used DNA fingerprinting to deter-
mine the paternity of the offspring.
The results were surprising, Dono-
ghue reports.

Fertile turkey eggs produced at the ARS
Germplasm Physiology Laboratory in
Beltsville bear hen identification numbers
and the date when each was laid.

"When semen from 7 to 10 toms
was pooled, we found that only 1 or
2 males produced a majority of the
offspring," she notes.
Donoghue says it is possible that
sperm motility influences the number
of sperm that make it to the sperm
storage tubules in the hen and
subsequently fertilize the eggs.
"If our hypothesis proves correct,"
she adds, "the sperm motility test

could be adapted and used by the
turkey industry as a simple and
reproducible objective method for
evaluating the male component of
"The potential impact of sire
selection, based on a test that corre-
lates sperm motility with fertilizing
potential, could alter the way breeder
toms are managed throughout the
United States." she continues.

"Simply by sorting out males that are
not contributing to offspring produc-
tion, we estimate a savings of $5
million annually for turkey breeders."
"We generally inseminate each
hen with 200-300 million sperm a
week," notes Tarhill's Lynn Bageley.
"Most of the sperm are pooled from a
flock. If we could have a practical
way to sort good toms from bad
toms, that could mean very big
savings. We would be able to reduce
the semen dosages to the hens, and it
would ultimately cut down on the
number of toms we need to maintain
to keep our hens in production.
"We're looking forward to any
new improvements in the turkey
production process."-By Tara
Weaver, ARS.
Ann M. Donoghue is at the USDA-
ARS Germplasm and Gamete Physi-
ology Laboratory, Bldg. 2b2, 10300
Baltimore Ave., Beltsville, MD
20705-2350; phone (301) 504-8580,
fax (301) 504-8546, e-mail *

SCOTT BAUER (K7043-16)

Large White turkey female.

Agricultural Research/July 1998

Tactics Simplify Wasp-Rearing


"Agar keeps the fruit fly eggs
from drying out," says entomologist
John P. Spencer of the Honolulu
laboratory. "We put about 5,000 fruit
fly eggs on agar in a 3-3/4-inch-
square petri dish and give caged
female wasps about 22 hours to
insert their eggs into the fruit fly
eggs. After that, it's easy to move the
parasitized eggs from the agar block
to large trays that we use for the next
steps of production. Using agar has
probably boosted our production at
least fivefold compared to our
previous method."

Biosteres arisanus wasps inject their eggs into oriental fruit fly eggs.

H helpful wasps that kill crop-
destroying fruit flies should
be easier to breed indoors,
thanks to ongoing work by scientists
with the Agricultural Research
Service in Hawaii.
Massive numbers of lab-reared
beneficial wasps can be deployed
outdoors to attack Mediterranean
fruit flies and other tropical and
subtropical fruit fly pests. The wasps,
harmless to humans, "may reduce
reliance on chemical insecticides,"
says ARS entomologist Ernest J.
Harris in Honolulu.
Harris is the first to establish a
thriving indoor colony of Biosteres
arisanus wasps. He says the insect,
less than a quarter inch long, "is one
of the most important wasp enemies
of medfly and oriental fruit fly, in
part because it outcompetes other
parasitic wasp species."
Medflies attack more than 400
crops worldwide; oriental fruit flies
pester more than 230.
ARS colleagues at Honolulu have
used the "Harris strain" of B. arisa-
nus, along with other species of
beneficial wasps, in experiments to
streamline mass-rearing. A key

discovery was that female B.
arisanus wasps readily lay their
eggs in fruit fly eggs that are
placed atop a gelatinous
substance called agar.
A w asp egg' ik about 4
limnei egg. notes Renato C. Bautista,
a researcher w ith the Lini-
\ersit\ of Hawaii \%ho
\works \% ith Harris.

Female wasps can
easily reach and
parasitize the fruit
fly eggs that ARS
entomologist John
Spencer places on
agar in laboratory
petri dishes.

Agricultural Research/July 1998

The lab procedures are the work of
a team led by Spencer. The tech-
niques have attracted interest from
scientists in other countries trying to
combat non-native fruit flies.
When a wasp egg hatches, the
insect grows inside the developing
fruit fly, eventually killing it. Wasps
that emerge from pupal cases-the
capsulelike chambers that housed the
immature flies-can then be put to
work outdoors.
Related experiments have shown
that a pneumatic air separator-a
device normally used for cleaning
seeds-simplifies sorting of parasit-
ized from unparasitized fruit flies.
The chore is best handled when the
fruit fly is a pupa; that is, just before
it becomes an adult.
These studies were led by ARS
food technologist Harvey T. Chan at
Hilo, Hawaii.
The separator swiftly and accurate-
ly sorts fruit fly pupae parasitized by
any of three wasps-Dia-
chasmimorpha longicaudata,
D. tryoni, and Psyttalia
i fletcheri. "Unparasitized pu-
pae," explains Chan, "are
heavier than their parasit-
ized counterparts. That cre-
ates a natural division of
floaters versus sinkers."
The approach, Chan
says, should be easy to
automate.-By Marcia
-Wood, ARS.
SHonolulu and Hilo
S researchers mentioned
in this article can be
contacted through the
S USDA-ARS Tropical Fruit,
Vegetable, and Ornamental
Crop Research Labora-
tory, P.O. Box 4459,
Hilo, HI 96720;
', phone (808) 959-
-4300, fax (808) 959-
4323, e-mail *


jnomologists rrnest j. narris (teit), wno itn mte Agriculturai Kesearcn service, ana
Renato C. Bautista, with the University of Hawaii, examine a papaya fruit trap with oriental
fruit fly eggs parasitized by Biosteres arisanus wasps.

Agricultural Research/July 1998

Setting the Stage To Screen Biocontrol Fungi

F or agricultural researchers, the
clock is ticking. They must
find a replacement for methyl
bromide, or leave America's growers
helpless against a horde of agricultur-
al pests and food pathogens. Methyl
bromide-now used to protect more
than 100 crops from an array of pests
and pathogens-will be phased out
by January 1, 2001.
A variety of new tools-both
chemical and nonchemical-will be
needed to find alternatives for methyl
bromide, now the only pesticide and
soil fumigant used to control several
pests. Biological agents will play an
important role.
ARS scientists in Beltsville,
Maryland, have discovered three new
species of beneficial fungi that may
have the potential to fill part of the
gap left by the phaseout of methyl
Mycologist Gary J. Samuels iden-
tified and described the new fungi.
Amy Y. Rossman, who leads the
ARS Systematic Botany and Mycolo-
gy Laboratory, says, "All three of
Samuels' new fungi belong to the
genus Hypomyces. That makes them
cousins of known beneficial fungi in
a related genus-Trichoderma.
"Since Trichoderma attacks other
fungi, these newly discovered
relatives also hold promise as biocon-
trol agents," says Rossman.
Samuels is a world expert on
Trichoderma. "The problem," he
says, "is that these newly described
fungi reproduce primarily asexually,
so they can't be readily improved by
sexual reproduction to fight crop
Samuels' job at the Beltsville lab
is to describe and catalog new species
of fungi. His systematic taxonomic
work lays the foundation for other
scientists seeking to develop biologi-
cal agents that combat crop-destroy-
ing fungi or produce useful second-

ary metabolites, such as chitinase
Samuels' work is cut out for him.
"Many organisms important to
agriculture are still undescribed or
relatively unknown," he says. "Many
are new species-previously un-
known to science."
Most mycologists agree that the
estimated number of fungal species is
around 1.5 million. Only about 10
percent have been scientifically
Samuels, working with Kadri
Poldmaa of the Institute of Botany
and Zoology at the University of
Tartu in Estonia, discovered one of
the new species of Hypomyces in
"It often happens that these fungi
occur in nature as the asexually
sporulating form, Cladobotryum, in
the absence of their sexual state,
Hypomyces. Both forms are given

In his Beltsville laboratory, microbiologist
Gary Samuels examines various species of
Trichoderma fungi collected from Belgium
and the United States.

Such is the case of the asexual
state of the new species, Hypomyces
viridigriseus," says Samuels. The
fungus' asexual form, C. viridigrise-
um, was first found in Ontario,
Canada, in 1988.
It was not seen again until
Samuels and Poldmaa were collect-
ing fungi in Illinois in 1996. There
they found C. viridigriseum grow-
ing on an old fungus in association
with the Hypomyces state that they
determined to be an undescribed
The other two newly described
species, H. favoli and H. puertori-
censis, were discovered on rotting
wood by USDA Forest Service sci-
entist D. Jean Lodge in 1992 while
conducting a biological survey of
the rainforest in Puerto Rico.
Samuels and Poldmaa were able
to take a sexually produced spore
from each of these fungi, grow them
in pure culture, and produce the
asexually sporulating state of each
new Hyplomyces.
But it is the sexually reproducing
forms of these new fungi that have
researchers excited about their
potential as biocontrol agents to
replace methyl bromide. "Discover-
ing a species of Hypomyces in its
sexual state is important, because
then the fungus can be genetically
manipulated and improved to fight
harmful fungi," says Rossman.
Several ARS laboratories are
searching for biological alternatives
to methyl bromide for controlling
fungal disease.-By Hank Becker,
Gary J. Samuels is at the USDA-
ARS Systematic Botany and Mycolo-
gy Laboratory, 10300 Baltimore
Ave., Beltsville, MD 20705-2350;
phone (301) 504-8279, fax (301)
504-5810, e-mail garys@nt.ars- *

Agricultural Research/July 1998

A closeup look at Burke, the latest pinto bean from ARS and university plant scientists. It resists a host of
harmful fungi and viruses that can otherwise cheat growers of a bountiful harvest.


hen it comes to survival,
Burke is a real scrapper.
The latest pinto bean cultivar from
Agricultural Research Service and
Washington State University (WSU)
scientists, Burke fends off several
harmful viruses and fungi that can fell
a lesser plant.
Scientists bred the cultivar with a
potent genetic package conferring
high levels of disease resistance. This
should give commercial growers add-
ed insurance against culprits like the
bean common mosaic virus and bean
common necrosis virus. Both can
cause yield losses of up to 60 percent.
A third menace, the curly top virus,
is "a regional problem-mainly in the
Pacific Northwest, where seed stock is
produced," says Phillip N. Miklas, a
geneticist in ARS' Vegetable and For-
age Crops Production Research Unit
at Prosser, Washington.
He is part of a bean-breeding team
that includes ARS plant pathologists
Matt J. Silbernagel and J. Rennie
Stavely and WSU colleague An N.
Hang. Their prized pinto debuts this
summer for production in western
states including Colorado, Idaho,
Washington, and Wyoming.
Besides viruses, the new cultivar
also resists U.S. forms of the rust fun-
gus, Uromyces appendiculatus. Un-
checked by chemical fungicide or oth-
er measures, Uromyces causes a rust-

colored blight on the leaves of sus-
ceptible bean plants. Severe outbreaks
may wipe out an entire crop. But with
Burke, the fungus never gains a firm
toehold in the rest of the plant, so it
doesn't cause serious disease.
The cultivar also withstands Pythi-
um and Fusarium fungi, soil-dwelling
microbes that can inflict costly root
"When conditions are ripe for root
rot, you can have 20 to 30 percent
yield losses," notes Miklas. "Burke
has a thriving network of roots that
allows it to survive damage caused by
the fungi."
Farmers planting the hardy cultivar
will get semi-upright plants that ma-
ture in 89 to 95 days. Burke produces
large, firm, tan-colored seeds that
cook and store nicely without turning
into a crumbly, unappealing mush.
That's important, considering how
fond American consumers are of pin-
to beans-eating more than 3 pounds
per person each year, according to
USDA's Economic Research Service.
While firm, high-quality seed is
important to a cultivar's success, so is
high yield. Burke seems to measure
up on both counts. In test plantings at
40 different locations in the Midwest
and Northwest from 1994 to 1996,
Burke outperformed 8 competing pin-
to lines in the National Dry Bean Co-
operative Nursery.

In Colorado test plots, Burke's
yields were up to 12 percent higher
than the industry standards, Othello
and Sierra.
One likely reason: Burke is a cross
between these two venerable culti-
vars, so it possesses many of the de-
sirable features of both, says Silberna-
gel. Now retired, he and Hang did the
original breeding work that led to
"Othello is one of the most widely
grown pinto beans because it per-
forms well under many different
growing conditions," says Miklas,
who is Silbernagel's successor. "An
advantage of Burke over Othello is
better disease resistance."
The new pinto line also earned
higher ratings for canning quality in
tests conducted by ARS' George Hos-
field at Michigan State University.
Encouraged by test results, Miklas'
group applied for plant variety protec-
tion on Burke. This will help ensure
the cultivar's genetic purity and lon-
gevity as it goes into commercial pro-
duction.-By Jan Suszkiw, ARS.
Phillip N. Miklas and Matt J. Sil-
bernagel (retired) can be reached at
the USDA-ARS Vegetable and Forage
Crops Production Research Unit,
24106 North Bunn Rd., Prosser, WA
99350; phone (509) 786-9258, fax
(509) 786-9277, e-mail 4

Agricultural Research/July 1998

Cah Marker Gene Aids

Plant Transformations

Scientists aiming to genetically
engineer crop plants are
always on the lookout for
genes they can use as markers in their
experiments. Now, a gene known as
cah may prove a useful addition to
today's limited array of choices.
That's according to Agricultural
Research Service geneticist J. Troy
Weeks at Lincoln, Nebraska.
Weeks and other biotechnologists
pair a marker with an experimental
gene intended to give a plant some
prized trait, such as increased resis-
tance to its worst insect or disease
The marker clearly flags, for
researchers, plant cells that have the
new, useful gene. Other plant tissue
can then be discarded so scientists
can focus their efforts on the poten-
tially useful tissue. They nurture it
into laboratory plantlets and later into
greenhouse plants.
The marker gene that Weeks and
colleagues are testing enables plants
to tolerate a chemical called cyana-
mide. This versatile compound has
some seemingly contradictory uses. It
is an environmentally friendly ferti-
lizer that, in specific situations, can
also act as a herbicide or fungicide.
Weeks' laboratory use of cyana-
mide exploits the first two of these
uses. His cah marker gene enables
callus-clumps of plant tissue-
grown in petri dishes to convert
cyanamide into urea fertilizer.
Normally, plants cannot do this.
In petri dishes, cah-equipped cells
soon appear as greenish sections
against the yellow-white callus tissue.
In later stages, this callus may
develop healthy shoots and roots.
Cells not containing the cah gene
may appear brownish. The few short
roots that may develop from this
tissue usually won't survive. But the
cah-containing cells, nourished by
the cyanamide fertilizer, will thrive.

In addition to these readily appar-
ent differences in callus, scientists
can check for the cah gene with a
fast, simple, and inexpensive assay.
Unlike tests used to detect some other
marker genes, the assay for cah does
not require hazardous chemicals.

Where It's From, What It Does
The cah gene comes from a fungus
found naturally in soils. Weeks saw
the gene's biotech potential because
he knew two things: The fungi-

because of this gene-play an
essential role in converting cyana-
mide into a useful fertilizer for
plants; and without the fungi, cyana-
mide may kill plants instead of
feeding them.
When used as a fertilizer, cyana-
mide must be applied before plants
emerge. Soil microorganisms break it
down into urea that plants can use.
The microorganisms that do this job
include the fungus Myrothecium
verrucaria. The cah gene was
borrowed from the fungus.

The gene cues the fungus-or in
this case, the genetically engineered
plant cells containing the cah gene-
to create an enzyme called cyana-
mide hydratase. The enzyme enables
the fungus or cah-equipped plant cell
to add the water molecule necessary
to convert the fertilizer form of
cyanamide, called calcium cyana-
mide, into urea. Normally, if the
calcium cyanamide fertilizer were
mistakenly applied to plants, they
might turn yellow and die-or at
least produce lower yields.

Geneticist Troy Weeks has produced more than 100

healthy wheat plants with the cah gene inside.

In the laboratory, Weeks moved
the cah gene into wheat cells using a
bioblaster, or gene gun. The gun
shoots microscopic gold particles-
coated with experimental genes-
into plant tissue in petri dishes. Then
he grew the cells on a gelatinous bed
of nutrients spiked with cyanamide.
Cells with the cah gene working
inside could then convert cyanamide
into urea fertilizer and grow shoots
and roots that were the start of new
plants. So far, Weeks has produced
more than 100 healthy wheat plants
with the cah gene inside. He is
seeking a patent for his work.
Weeks collaborated with Olin D.
Anderson of the ARS Western
Regional Research Center in Albany,
California; Kelly Y. Koshiyama of
the University of California at
Berkeley; Tony Schiieffner of Lud-
wig-Maximilians University in
Munich; and Ursula Maier-Greiner,
formerly at the Munich university.
Maier-Greiner was part of a German
team that was the first to discover
and copy the cah gene.
The gene is a potential alternative
to marker genes based on resistance
to antibiotic drugs or to widely used
commercial herbicides.
In lab experiments using an
antibiotic-resistance marker, plant
cells exposed to the antibiotic kana-
mycin-for example-won't thrive
unless they take up this marker.
Some critics fear that when people
eat foods derived from such plants,
their intestinal microflora might
become resistant to the pharmaceuti-
cal. Biotechnologists see that as
highly unlikely.

Marker genes that rely on resis-
tance to widely used commercial
herbicides have also drawn criticism,
in part because of concern that the
herbicide-resistance trait might
escape if crop plants were to breed
with weedy relatives nearby, perhaps
creating super-resistant weeds.
Because calcium cyanamide is not
widely used as a herbicide, Weeks
sees this risk as nil.

A Benign Alternative?
In new experiments, Weeks wants
to determine if outfitting plants with
the cah gene would open the door for
growers to use calcium cyanamide
fertilizer more conveniently; that is,
not just on bare soil, but also when
plants emerge-or perhaps anytime
thereafter-without harming the
"Cyanamide fertilizer apparently
poses less risk of nitrate pollution to
groundwater than do the popular
urea-based or ammonium-nitrate-
based fertilizers," Weeks says. Also
known as lime nitrogen, calcium
cyanamide fertilizer dates back to the
early 1900s. It's made from heating
lime and coal.-By Marcia Wood,
For more information on U.S.
patent application number 08/
873,001, "Transformation of Wheat
with the Cyanamide Hydratase
Gene," contact J. Troy Weeks,
USDA-ARS Wheat, Sorghum, and
Forage Research Unit, 344 Keim
Hall, University of Nebraska, Lin-
coln, NE 68583; phone (402) 472-
9640, fax (402) 472-4020, e-mail *

Geneticist Troy Weeks examines wheat cells after bombardment in the gene gun enclosure.

Agricultural Research/July 1998 Agricultural Research/July 1998

Watch Out, Soft-Bodied Pests!

ew weapons from the
Agricultural Research
Service could spell better
control over silverleaf whiteflies and
other soft-bodied insect pests, such as
When silverleaf whiteflies, Bemi-
sia argentifolii, infest a plant, they
look like tiny specks of ash covering
leaves and stems. The pests suck sap
from more than 600 kinds of plants
including many fruit, vegetable,
fiber, and ornamental crops. Their
saliva can also transmit destructive
plant viruses and disorders. Every
year, whiteflies cause multimillion-
dollar crop losses in the United
But ARS scientists are adding to
the limited arsenal against this pest.
They recently came up with a new
way to apply insecticides that white-
flies can't readily escape. They also
ranked wild species of tobacco plants
for their commercial potential as
sources of a natural insecticide
known as sugar esters. And they
devised lookalike synthetic versions
of the natural compounds that were
the forerunner of a commercial
version soon to be a registered
Conventional insecticide sprayers
have had only limited success against
this whitefly.
"That's because a high percentage
of the adult and immature stages of
B. argentifolii feeds and breeds on
the lower surface of plant leaves,"
says ARS entomologist Alvin M.
Simmons. "Most sprayers do not
deliver insecticides effectively to the
underside of plant leaves."
For this and other reasons-
including insecticide cost and effec-
tiveness and ecological, health, and
aesthetic concerns-Simmons and
his colleague, entomologist D.
Michael Jackson, have been explor-
ing alternative technologies to reduce

the amounts of insecticide used and
to better target them on fruits and

All Fogged In
Under a cooperative research and
development agreement with Strauch
and Sons, Inc., of Bethesda, Mary-
land, the scientists tested and evaluat-
ed an ultrasonic fogging device.
Originally, the fogger was de-
signed as a humidifier and fungicide
applicator for produce in storage. The
scientists wanted to see if it could
effectively deliver low dosages of
contact insecticides to whitefly-
infested plants growing in a
Greenhouse whitefly control is
crucial-not only because seedlings
can be severely damaged, but also
because this is where field outbreaks
can get their start. Safe from winter
and the weather, whiteflies can spend
all year breeding and feeding on
greenhouse plants. Then, when
infested seedlings are transplanted
outdoors, so are the whiteflies.
The scientists conducted fogger
tests on whitefly-infested collard
plants in greenhouses.
"The fogger dispenses about 4
gallons of water per hour, producing
droplets of about 5 microns in
diameter," Simmons says. "The
droplets are so small, they act much
like a gas."
The scientists showed that the
fogger could successfully apply two
whitefly-killing sprays in a mix with
water that reached and coated the
lower leaf surface.
One of the sprays used imidaclo-
prid-one of the newest commercial-
ly available whitefly insecticides.
The other spray was an experimental
natural, or "biorational," insecticide
consisting of sugar esters extracted
from a species of wild tobacco plant
known as Nicotiana glutinosa.

"Sugar esters break down the
insects' outer coating, causing the
pests to shrivel as they lose water,"
says Simmons. "The esters are
relatively nontoxic to hard-bodied
beneficial insect predators like lady
beetles and to other beneficials"
With the fogger, similar amounts
of the sprays coated both the top and
bottom of infested leaves.
"In just 6 minutes, the fogger
delivered less than half as much

A wild tobacco plant, Nicotiana glutinosa, is
a source of sugar esters used as an experi-
mental natural insecticide.

imidacloprid as the label recommend-
ed for control," Simmons says. But
the result was a 100-percent whitefly
The scientists say the new fogger
could work in commercial green-
houses as an automated method of
controlling whiteflies.

Agricultural Research/July 1998

il*l*,J [MMnU

"It would be ideal for controlling
whiteflies and other target pests on
high-value crops like poinsettias that
have low damage thresholds and on
greenhouse-grown vegetable crops
for which low levels of contact
insecticides are preferred," Simmons
Simmons and Jackson believe the
fogger could also be adapted for field
use, but the fog would need to be
housed to protect it from the wind

until it could reach the plants. The
fogger is available commercially
from Shira Aeroponics, Ltd., of
Rehovot, Israel.
While the fogger applies sugar
esters in an effective manner, "cur-
rent processing and production
practices have been too expensive to
make growing plants for their esters

feasible commercially," says Jack-
son. "For the amounts of sugar esters
that have been produced per acre,
relative to the cost of extraction, it
has been too expensive."
One problem has been not know-
ing which, of all the natural esters
available from Nicotiana, would have
the best commercial potential. To
find out, Jackson and Simmons
worked with other ARS scientists to
grow and screen 21 wild Nicotiana
species in field tests.
Cooperators included chemist
Orestes T. Chortyk, who is retired
from the former ARS Phytochemical
Research Unit in Athens, Georgia;
ARS agronomist Michael G.
Stephenson at Tifton, Georgia;
entomologist Chris D. Harlow and
geneticist Vernon A. Sisson from the
North Carolina State University in
Oxford; and entomologist Albert W.
Johnson at Clemson University in
Florence, South Carolina.
"We selected eight candidate
species, including N. glutinosa, for
further study to determine which
were the best sources of sugar
esters," Jackson says.
In 1995, the scientists grew plants
of all eight species in field plots at
Florence and Charleston, South
Carolina, and at Tifton. Three times
during the season at each location,
they cut the aboveground portion of
the plants, weighed them, and
extracted chemicals from the leaves.
"We believe the best commercial
candidate overall is N. trigonophylla.
Its esters are the least complex, very
concentrated, and comparatively easy
to extract," says Jackson.

Toward a Suitable Synthetic
At another ARS laboratory, in
Kearneysville, West Virginia, ARS
entomologist Gary Puterka focuses
on a different soft-bodied insect
pest-the pear psylla, Cacopsylla

pyricola. This yellowish-green insect
may be the primary reason the East
Coast pear industry has disappeared.
Sugar esters have been among the
most successful biorational com-
pounds Puterka has used against these
pests in tests at ARS' Appalachian
Fruit Research Station. When he
sprayed esters mixed with water on
pear leaves, the compounds killed
both nymphs and adults.
Searching for an easier and cheaper
way to mass-produce the esters,
Puterka worked with Ava Chemical
Ventures of Portsmouth, New Hamp-
shire. Recently, the firm produced a
lookalike synthetic version of the
active ingredient in natural sugar
Working with Ava Chemical, he
identified a form of synthetic sugar
ester that is readily water soluble, yet
remains active in controlling insects.
Says Puterka, "The major problem
with earlier versions of synthetic
sugar esters was their inability to
dissolve in water."
Puterka is conducting further
studies under a cooperative research
and development agreement with the
New Hampshire company. He be-
lieves the synthetic esters will soon be
fully registered and could be commer-
cially available in the United States
by 1999.-By Hank Becker, ARS.
Alvin M. Simmons and D. Michael
Jackson are at the USDA-ARS U.S.
Vegetable Laboratory, 2875 Savan-
nah Hwy., Charleston, SC 29414;
phone (843) 556-0840, fax (843) 763-
7013, e-mail
mjackson @
Gary J. Puterka is at the USDA-
ARS Appalachian Fruit Research
Station, 45 Wiltshire Rd., Kear-
neysville, WV 25430; phone (304)
728-3451, ext. 361, fax (304) 728-
2340, e-mail *

Agricultural Research/July 1998

Better Diets for Dairy Cows

D airy cows have known it for
some time: They make more
milk or get fatter when their diet in-
cludes high-moisture, finely ground
corn instead of dry, rolled corn. Now,
Agricultural Research Service studies
have shown this scientifically.
"If you change harvesting and pro-
cessing methods, you can increase
corn's energy value," says animal sci-
entist Barbara Glenn.
Earlier studies at ARS' U.S. Dairy
Forage Research Center in Madison,
Wisconsin, found that high-moisture,
finely ground corn ferments rapidly.
Feeds that are rapidly fermented in
the rumen and fully digested in the in-
testines provide more energy for the
cow to use to produce milk.
But how much more, asked Glenn
and former colleague Vic Wilkerson
at the ARS Nutrient Conservation and
Metabolism Laboratory in Beltsville,
Maryland? Wilkerson is now with
Land O' Lakes' Western Feed Divi-
sion in Portland, Oregon.
At the Beltsville lab three decades
ago, ARS scientists first measured the
energy value of feedstuffs for milk

production-known as net energy of
lactation (NEL). Today the lab is still
one of a handful worldwide equipped
with calorimetry chambers for net en-
ergy measurements.
"Any time we get NEL data, it's
very valuable. There's very little data
published because of the cost of doing
the studies," says Bill Weiss, associate
professor of animal science at Ohio
State University. Weiss is a member
of a National Research Council
subcommittee that is revising the
nutrient requirements of dairy cattle,
including energy values of feeds.
Feed consultants and dairy farmers
rely on NRC's published values to
formulate animal rations. But mea-
sured NEL values for new corn sourc-
es and types are rare; most values are
Dry corn might have been good
enough in the past, but not for today's
top milk producers. With many corn
hybrids and storage and processing
methods to pick from, says Glenn,
"corn isn't just corn anymore."
Wilkerson and Glenn measured the
energy value of diets containing high-

moisture corn compared with dry
corn. Glenn says high-moisture
corn-cut early, while still moist, and
then ensiled-is popular with dairy
farmers in the North Central and
Northeast regions.
The researchers also compared the
effect of grinding corn versus rolling
it. Small ground particles are report-
edly more digestible and thus able to
provide more energy, she says. The
different corns were mixed with alfal-
fa, soybean meal, and a powdered
mineral supplement.
Wilkerson calculated each corn's
contribution to the energy value of
whole diets. He wasn't surprised to
find high-moisture corn provided 14
percent more energy than dry corn,
instead of the 4 percent difference
stated in the NRC handbook.
"Dairy farmers were getting fat
cows when they substituted high-
moisture corn for dry corn," he notes.
"That suggested there was more ener-
gy available than what's shown in the
But farmers don't want fat cows
any more than they want overly thin

Agricultural Research/July 1998

ones, especially when they stop mak-
ing milk. "If a cow's too fat or lean,
she won't breed," says Wilkerson.
Farmers also don't want cows get-
ting more nutrients than they need for
optimum milk production. It inflates
the feed bill. And excess nutrients ei-
ther add body fat or exit the cow as
potential pollutants.
But dairy farmers do want more
milk. In the ARS study, cows pro-
duced 4-plus pounds more milk daily
with high-moisture corn than dry
corn-in the alfalfa-based diet. Pro-
cessing also made a difference. Finely
ground corn provided 5 percent more
energy than the big chunks of rolled
corn, increasing milk production by
about 5 pounds a day, says Wilkerson.
Weiss says his committee will con-
sider the data in revising the energy
values for dairy feedstuffs, noting that
the values may be higher than the
committee will agree on. "All net en-
ergy values we use now are estimated
on very old numbers."-By Judy
McBride, ARS.
Barbara P. Glenn is at the USDA-
ARS Nutrient Conservation and Me-
tabolism Laboratory, Bldg. 200,
10300 Baltimore Ave., Beltsville, MD
20705-2350; phone (301) 504-8315,
fax (301) 504-8162, e-mail *

Testing for Natural Aflatoxin Inhibitors

In the United States, corn with more than 20 parts per billion (ppb) of
aflatoxin-which is the equivalent of just 1 ounce in 3,125 tons-is not consid-
ered fit for feeding to animals that produce meat or milk for humans.
A known carcinogen, aflatoxin is the metabolic byproduct of Aspergillus
flavus fungi. Grain with more than 5 ppb gets thumbs down for making food-
grade corn products. And in the South and in areas where occasional drought
stresses corn and increases A. flavus levels, farmers may lose opportunities to
produce corn valued for export markets.
Finding natural compounds in corn that affect the toxin-producing machin-
ery of A. flavus is a first step toward identifying corn genes that might be
modified to make the microbe less harmful. The strategy could be joined with
efforts to breed corn that discourages growth of the fungus.
Now, a faster, cheaper test is helping researchers detect genetically regulated
compounds in corn that inhibit or promote the ability ofA. flavus fungi to
produce aflatoxin. ARS chemist Robert A. Norton developed the new proce-
dure at the National Center for Agricultural Utilization Research in Peoria,
"We can now realistically test a much wider range of compounds for toxin-
producing activity-including lipids-using 1 milligram [thousandth of a
gram] or less of the test compound," he says.
Norton purchases the compounds for testing, some of which cost up to
hundreds of dollars per milligram, though most cost less. Despite the expense,
Norton says that it's cheaper to buy the compounds than to tediously extract
them from corn.
"And with the new testing method, we don't have to use as much of them,"
he says.
His procedure involves placing the test compound, along with about 29
microliters [millionths of a liter] of a nutrient medium and A. flavus spores, on
a small disk. The disk is hung by a pin from a Teflon cap inside a bottle con-
taining a small amount of water. After 5 days, researchers measure fungal
growth on the disk. They use a small amount of solvent to extract aflatoxin
from the fungus; high-performance liquid chromatography measures the
amount. The method saves time, nutrient medium, and solvent.
Norton currently tests up to 200 samples per week. So far, he has pinpointed
several aflatoxin-synthesis inhibitors, including carotenoids that impart yellow
color to modern corn hybrids and a colorless benzoxazolinone compound. He
also plans to test colorless anthocyanin-related compounds that could be bred
into yellow cor.-By Ben Hardin, ARS.
Robert A. Norton is in the USDA-ARS Bioactive Agents Research Unit,
National Center for Agricultural Utilization Research, 1815 N. University St.,
Peoria, IL 61604; phone (309) 681-6251, fax (309) 681-6693, e-mail
nortonra @ *

Unshelled feed corn.

Agricultural Research/July 1998

-n I .-I. K.-c


Lush stand of tall whitetop, a weed that is crowding out native plants in parts of several western states.

C would hungry goats serve as
natural lawnmowers for tall
whitetop, a weed crowding
out native plants in western states?
In a preliminary summer grazing
test with 13 young goats, the animals
ate the white-flowered pest with no
ill effects. That's important, because
scientists aren't completely certain
whether the plant is poisonous to
A combination of tactics-
grazing, herbicides, mowing, and

seeding with aggressive annual
plants-might be needed to quell the
weed, says range scientist James A.
Young. He is with the Agricultural
Research Service in Reno, Nevada.
Right now, ranchers and other land
managers have no fast, easy way to
keep tall whitetop at bay. Cattle and
sheep, Young says, will graze it when
it grows amid other plants, but they
won't tackle pure, dense stands of
this weed. The plant is also known as
perennial pepperweed.

Young and colleagues fenced the
goats in an infested meadow on a
floodplain of the Truckee River in
Nevada. The animals grazed thick
stands of tall whitetop, along with
regrowth from those stands and from
mowed stands. They preferred the
young, tender, more digestible re-
growth, eating about 75 percent of it-
compared to about half of the vegeta-
tion in older stands. On older plants,
they ignored the semi-woody stems and
nibbled only leaves and soft tips.

Agricultural Research/July 1998

Native to southern Europe and southwestern Asia, tall whitetop, Lepidium

latifolium, has cropped up in nearly every western state and is also well-

established in New England. It thrives along streams, rivers, ditches, irriga-

tion canals, and salty marshes, and it spreads easily to adjacent meadows.

Young leads the Ecology of Tem-
perate Desert Rangelands Research
Unit at Reno. He and technician
Charles D. Clements, also of the
Reno team, conducted the test along
with Lynn F. James, director of ARS'
Poisonous Plant Research Laboratory
in Logan, Utah. The Logan lab pro-
vided the goats.
Native to southern Europe and
southwestern Asia, tall whitetop has
cropped up in nearly every western
state. It's also well-established in
New England. It thrives along
streams, rivers, ditches, irrigation
canals, and salty marshes, and it
spreads easily to adjacent meadows.
Tall whitetop typically grows 1 to 3
feet tall, but can reach 8 feet in wet
Tall whitetop is an unlikely
candidate for control by beneficial
weed-eating insects. That's because,
as a member of the mustard family, it
is related to several crops, including
broccoli, cabbage, and horseradish.
"Our lab," says Young, has
smelled like horseradish ever since
we started studying tall whitetop in
1990. The odor is overpowering."
This year, researchers in Logan
plan toxicity tests using sheep. Reno-
based scientists will launch a new
goat experiment with perhaps 30
In late summer, after the grazing
portion of the study, the Reno
scientists intend to test candidate

Unfortunately, the chemicals
don't travel to the weed's deep roots
or to its rhizomes-rootlike exten-
sions dotted with sprouts. So Young
is pursuing greenhouse and outdoor
tests to see what tactics might
forestall roots and rhizomes.
Another alternative has emerged
from greenhouse studies at Reno.
These tests suggest dense stands of
the weed may so greatly deplete soil
nutrients that plant species with root
systems better suited for searching
out nutrients might outcompete it.
Soil scientist Robert R. Blank
conducted the tests, pitting whitetop
against cheatgrass, an aggressive

"If the same effect holds in outdoor
tests," he says, "we might be able to
use a similarly aggressive, densely
rooted native grass."-By Marcia
Wood, ARS.
James A. Young, Robert R. Blank,
and Charles D. Clements are in the
USDA-ARS Ecology of Temperate
Desert Rangelands Research Unit,
920 Valley Rd., Reno, NV 89512;
phone (702) 784-6057, fax (702) 784-
1712, e-mail
Lynn F. James is at the USDA-ARS
Poisonous Plant Research Laborato-
ry, 1150 E. 14 N., Logan, UT 84341;
phone (435) 752-2941, fax (435) 753-
5681, e-mail *


Tall whitetop in the foreground has been grazed by goats.

Agricultural Research/July 1998

Heads Up for Soybean Rust

Four years ago, it was found lurking on soybeans
growing on the Hawaiian island of Oahu. And some U.S.
plant pathologists believe it's only a matter of time before
this devastating fungus gets to the continental United
States-hitchhiking on a traveler's clothing or in cargo or
blown on the wind.
It's the Asian species of soybean rust, known formally
as Phakopsora pachyrhizi. And its potential for damage is
At a 1995 workshop convened to propose a plan for
controlling a possible invasion of P. pachyrhizi, U.S.
experts estimated that the fungus could cut soybean yields
by more than 10 percent anywhere in the country. In the
warm, moist Southeast, it could cause losses of up to 50
percent. In addition to soybeans, P. pachyrhizi naturally
infects 31 legume species in 17 different genera. One of
those plants is kudzu-a common weed pest in the
Southeast-which might serve as a continual source of
"All you need is one spore," says ARS plant patholo-
gist Morris R. Bonde. Under the right environmental
conditions, it could produce trillions of spores within
weeks." Bonde was one of the experts at the workshop
sponsored by the University of Illinois' National Soybean
Research Laboratory.
Bonde is also one of the first U.S. scientists to study
soybean rust, starting in 1974 when he joined ARS'
Foreign Disease/Weed Science Research Unit in Freder-
ick, Maryland. He says it was one of three foreign diseas-
es the agency deemed necessary to prepare for.
He worked with the late Edgar E. Hartwig, an ARS
soybean breeder in Stoneville, Mississippi, who developed
some breeding lines with resistance to soybean rust. But
as time passed and the virulent Asian species remained on
the other side of the globe, interest waned.
Now Bonde and molecular biologist Reid D. Frederick
and biologist Gary L. Peterson are gearing up this re-
search. Bonde says there's a need for more germplasm
with strong resistance to soybean rust. So he's searching
for a laboratory method to rapidly evaluate wild germ-
plasm and breeding lines that accurately reflects how the
plants would react to the fungus in the field.-By Judy
McBride, ARS.
Morris R. Bonde, Reid D. Frederick, and Gary L.
Peterson are in the USDA-ARS Foreign Disease/Weed
Science Research Unit, 1301 Ditto Ave., Fort Detrick,
Frederick, MD 21702-5023; fax (301) 619-2880, [Bonde]
phone (301) 619-2860, e-mail bondem@ftdetrck-, [Frederick] phone (301) 619-7386, e-
mail [Peterson] phone (301] 619-
7313, e-mailpeterson@ncifcrf gov *

No Ants Allowed!

Two kinds of ants are surprisingly troublesome and
costly invaders of our homes, yards, and parks.
Fire ants infiltrate traffic signals, electrical switch and
telephone boxes, and air conditioners, creating a need for
costly replacements, while pharaoh ants are more likely
to migrate into warm buildings. Fire ants alone have
caused over half a billion dollars in damage costs and
control efforts since they entered the United States at the
turn of the century.
Now, after studying the ants' behavior, Agricultural
Research Service chemist Robert Vander Meer has found
a nontoxic way to stop their invasive habits. He discov-
ered and patented several noninsecticidal ant repel-
lents-the first of their kind.
Vander Meer is in ARS' Center for Medical, Agricul-
tural, and Veterinary Entomology's Imported Fire Ant
and Household Insects Research Unit at Gainesville,
The repellents are volatile chemicals with a high
vapor pressure that evaporate rapidly into the air. Labo-
ratory tests show that combining the repellents with a
slow-release material, such as powdered corn starch, will
extend the repellent's active life in the field up to a year.
"The repellents are ideal alternatives to insecticides,
especially in state or national parks and other areas
where their use is limited-or even prohibited-because
of possible human contact," says Vander Meer. "The
repellents are a way to keep the ants at bay, so to speak.
When applied, they inhibit foraging and keep ants
Fire ants infest an estimated 278 million acres in 11
southern states and Puerto Rico. Known for their burning
sting, they bother about 30 percent of the population
within infested areas each year.
Pharaoh ants, on the other hand, are urban dwellers
and cause most trouble indoors. They are a worldwide
pest, occurring in temperate and tropical climates.
During cold winter months, in northern states, the
pharaoh ants take up residence in buildings and homes.
Vander Meer says the next appropriate step would be
to test the repellents' effects on other ant species. "We
are currently studying their effects on the Argentine ant,
which is also a pest worldwide," he
says.-By Tara Weaver, ARS.
Robert K. Vander Meer is in the
USDA-ARS Imported Fire Ant and
Household Insects Research Unit, 1600
SW 23'd Dr., Gainesville, FL 32604; phone (352) 374-
5918, fax (352) 374-5818, e-mail *

Agricultural Research/July 1998


Induced Heat Resistance in E. Coli

Escherichia coli 0157:H7 bacteria that get only a
sublethal dose of heat can become more heat resistant
than bacteria that are not so exposed, report Agricultural
Research Service scientists in Wyndmoor, Pennsylvania.
The microbiologists at the ARS Eastern Regional
Research Center (ERRC) say the finding reiterates the
continuing need to adequately cook food to kill E. coli
0157:H7 and other food-poisoning microorganisms, or
pathogens. Cooking remains the primary means to kill
these organisms in foods.
"Our increasing understanding of the wide range of
factors that can affect pathogens' thermal resistance
indicates the need for a standard way to measure that
resistance," says Vijay K. Juneja, who conducted the
study in ERRC's Food Safety Research Unit.
Juneja and colleagues subjected beef gravy samples
containing E. coli 0157:H7 to 114.80F for 15 to 30
minutes, heat-shocking the bacteria at a temperature not
quite sufficient to kill them. Then they cooked the gravy
to a final internal temperature of 1400F.
The results: The pre-heated E. coli survived longer (a
1.5-fold increase in heat resistance) than other E. coli not
subjected to the sublethal heat. The increased thermotol-
erance lasted for at least 48 hours.
Therefore, says Juneja, food processors should realize
that bacteria will not be killed in foods that are heated
slowly to the final cooking temperatures normally used.
Heat-shocking conditions may occur in minimally
processed, refrigerated, cook-in-bag foods such as filled
pasta products (ravioli, tortellini, canneloni, etc.), mous-
saka, lasagna, and chili con came. The slow heating rate
and low heating temperatures used in preparing these
foods expose potential pathogens to conditions similar to
heat shock-which could make them more heat-resistant.
This induced heat-resistance could also be a concern
in meat products kept on warming trays before final
heating or reheating, or when equipment failure inter-
rupts the cooking cycle during processing.
Juneja says that traditional research methods to deter-
mine if heat kills pathogens are cumbersome because of
lengthy sample preparation times and nonuniform
heating. He and colleagues used a submerged stainless-
steel coil-heating apparatus that allows quick temperature
control by a thermostat, eliminating the customary
problems.-By Doris Stanley, ARS.
Vijay K. Juneja is in the USDA-ARS Food Safety
Research Unit, Eastern Regional Research Center, 600
East Mermaid Lane, Wyndmoor, PA 19038; phone (215)
233-6500, fax (215) 233-6406, e-mail *

Model Helps Time Stored Pest Fumigation

Most U.S. warehouses fumigate three or four times a
year to control moths and other stored product insect
pests. Fumigation-costing about $20,000 each time-is
initiated even when only two or three moths are sighted
in the warehouse.
"Fumigating when there are so few insects is a costly
waste," says Agricultural Research Service entomologist
James E. Throne. He works at the U.S. Grain Marketing
Production and Research Center in Manhattan, Kansas.
"Better timing can be achieved by having an accurate
count of how many insects are present and knowing
their stage of development. With this information,
warehouse managers can keep costs down and reduce
the amount of insecticide used."
Throne and entomologist David W. Hagstrum have
developed a computer model for tracking development
of the almond moth, a major pest of grain and other
stored products throughout the world.
In 1996, using data gathered by Polish entomologist
Jan Nawrot, ARS scientists developed a computer
model that simulates the life cycle of almond moths on
stored peanuts. Shortly after, they modified the model to
simulate the moth's life on stored corn and dried citrus
pulp. The basic data blocks of the model show how
temperature and moisture conditions affect the number
of adult moths, how many eggs each adult can lay, and
how long it takes for immature moths to complete
"Our predictions can help warehouse managers
decide when to use alternatives to insecticides. For
instance, we know that cooler temperatures can reduce
or stop moth reproduction and slow development of
immature moths," says Throne. "It may take only a
slight temperature drop, say from 750F to 650F, to
curtail moth activity."
Turning on fans to cool down the warehouse is much
less expensive-and more environmentally safe-than
Now the researchers are adapting the computer model
for predicting Indianmeal moth development in corn and
other stored products that can harbor the pest. These
moths are responsible for large expenditures by the
multibillion-dollar food industry for sanitation and
insecticidal treatments.-By Linda McGraw, ARS.
James E. Throne and David W. Hagstrum are in the
USDA-ARS Biological Research Unit, U.S. Grain
Marketing and Production Research Center, 1515
College Ave., Manhattan, KS 66502; phone (785) 776-
2796, fax (785) 776-2792, e-mail
throne *

Agricultural Research/July 1998

Diatomaceous Earth Wrecks
Insects' Internal Water Balance
What's a natural way to kill in-
sects in food processing plants? The
answer has been around for 20 mil-
lion years: diatomaceous earth (DE).
But DE isn't earth-or even dirt. It's
the broken-up shells of tiny plants,
called diatoms, that lived in the sea
roughly 20 million years ago. Today,
these fossilized skeletons are being
combined with heat treatment as an
alternative to methyl bromide for
controlling insects in flour mills and
other food processing plants.
"Turning up the heat creates one
big oven for the insect pests. The
heat breaks down the waxy layers of
their exoskeletons, and the DE ab-
sorbs the layers, disrupting their in-
ternal water balance. Without this
delicate balance of water, insects
can't survive," says Agricultural Re-
search Service entomologist Alan K.
Dowdy. He's at the agency's U.S.
Grain Marketing and Production Re-
search Center in Manhattan, Kansas.
In 1996 lab studies, Dowdy found
that 98 percent of red flour beetles
were killed when exposed to 1220F
and DE. This insect is noted for tol-
erating heat under normal condi-
tions. The study then became the
springboard for a 1997 joint U.S.-
Canadian field research project at
Quaker Oats of Ontario, Canada. For
the field test, the researchers placed
confused flour beetles-one of the
industry's worst insect invaders-in
the processing facility. One hundred
percent of the beetles died within a
day after exposure to a temperature
of 1150F and DE. The payoff for the
food industry: Cost of heat treatment
may be lower, and insect control is
better using DE and heat, compared
to using heat alone. Both Canadian
and U.S. food processing plants have
used heat treatments, but a few pro-
cessors are concerned about expen-
sive installation of new heating sys-

Rrcwnc Vpdate

teams in older buildings. The re-
searchers showed that lower temper-
atures could be used with DE and
still control insects. Alan K. Dowdy,
USDA-ARS U.S. Grain Marketing
and Production Research Center,
Manhattan, Kansas; phone (785)
776-2719, e-mail

"Seeing-Eye" Sprayer for Weeds
A new sprayer uses a light reflec-
tance sensor to scan the ground for
weeds, then kills them with less herbi-
cide than conventional sprayers use.
The eight-row hooded sprayer uses its
sensor to distinguish differences in
the light reflected from bare soil and
from weeds between crop rows. If it
"sees" a weed, it sprays it. The spray-
er was developed for row crops
through a cooperative research and
development agreement with Patchen,
Inc., of Los Gatos, California, and
ARS scientists in Mississippi. Re-
searchers tested the sprayer as part of
the Mississippi Delta Management
Systems Evaluation Area project.
The project studies how farm pro-
duction practices affect the water
quality of three Mississippi lakes. In
1996 and 1997, the savings on herbi-
cide spraying averaged 78 percent on
cotton plots and 51 percent on soy-
bean plots. Both crops were grown
with conservation tillage systems that
held plowing to a minimum and re-
lied on crop residue to control ero-
sion. [For earlier story and photo, see
"Smart Sprayer Selects Weeds for
Elimination," Agricultural Research,
April 1996, p.15.] James E. Hanks,
USDA-ARS Application and Produc-
tion Technology Research Unit,
Stoneville, Mississippi; phone (601)

Making Foods More Healthful
Could Add Taste, Too
Taste buds as well as nutrition
could benefit from future research to
increase the health-enhancing com-
pounds in plant foods. The com-
pounds are known as phytonutrients.
It appears that many phytonutrients
are produced as fruits and vegetables
ripen to their delectable peaks of fla-
vor. The dilemma: how to let ripen-
ing promote phytonutrients and yet
retard postharvest softening that
threatens quality. This question is
one of the research areas suggested
by nutrition, health, plant, and post-
harvest scientists from ARS, univer-
sities, and industry attending a recent
ARS-sponsored workshop on "Food,
Phytonutrients and Health."
News about potential phytonutri-
ent benefits of broccoli, garlic, tea,
soybeans, tomatoes, and other foods
has raised public awareness. But nu-
trition researchers need to determine
which phytonutrients would make
good targets for plant and postharvest
scientists to increase and preserve.
First, however, they need more sensi-
tive tests to indicate small changes in
risk for cardiovascular disease, can-
cer, or other maladies. Roger Law-
son, ARS National Program Leader
for Horticulture and Sugar, Belts-
ville, Maryland; phone (301) 504-
5912, re-mail

Giving Insects a KISS
An ARS entomologist got the idea
one day while blowing leaves in his
yard at home: Why not turn the leaf
blower into an insect collector? The
result is the keep-it-simple sampler
(KISS). An ARS engineer designed
and assembled it to ease the long
hours farmers and crop consultants
spend counting insects in cotton, soy-
beans, and other row-crop fields, so
they can estimate population trends
of pest and beneficial insects. Usual-

Agricultural Research/July 1998

ly they sample manually with nets or
by looking at individual plants. But
the KISS generates 150-mph winds
that blow insects off plants into a net
attached to the nozzle. ARS field
tests showed KISS-ing is 10 times
more efficient than hand-collecting
boll weevils. It has been used to col-
lect a variety of insects including
pepper weevils, corn rootworm
adults, and cotton fleahoppers. Most
insects collected with the KISS are
undamaged. Researchers believe it
could be used by home gardeners to
collect beneficial insects from wild
host plants and transfer them to their
gardens. Kenneth R. Beerwinkle,
USDA-ARS Areawide Pest Manage-
ment Research Unit, College Station,
Texas; phone (409) 260-9519, e-mail
k-beerwinkle @ tamu. edu

Milk Fever Gel Is Licensed
ARS has granted an exclusive li-
cense to Kemin Industries, Inc., of
Des Moines, Iowa, for an ARS-pat-
ented gel that may cut milk fever in
dairy cows by about 50 percent. Each
year, about 500,000 U.S. dairy cows
develop severe milk fever-usually
within a day after giving birth. The
disorder costs producers $150 mil-
lion a year. According to ARS re-
searchers, the gel may be given oral-
ly to cows when they give birth and
for the first 2 days of lactation. Other
oral formulations contain calcium
chloride, which can irritate the cow's
mucous membranes and the skin of
the person administering the treat-
ment. The ARS-formulated gel deliv-
ers calcium propionate, a less irritat-
ing form of calcium. Another advan-
tage of calcium propionate is that
cows can use it to make glucose for
energy. All lactating dairy cows are
energy deficient, because they use
much glucose to make milk, and they
can't eat enough immediately after
calving to meet their energy needs.

In ARS field trials with an Iowa Jer-
sey dairy herd, the gel reduced milk
fever from 50 percent in untreated
cows to 29 percent in treated cows.
Jesse P. Goff, ARS-USDA National
Animal Disease Center, Ames, Iowa;
phone (515) 239-8547, e-mail

Veterinary medical officer Jesse Goff
demonstrates the applicator for an ARS-
patented gel that may cut milk fever in
dairy cows by about 50 percent.

Corn-Based Heavy Metal
Heavy metals-lead, copper, zinc,
and others-in wastewater are a
weighty problem for U.S. industries.
Stringent environmental regulations
require treatment of wastewater to
remove heavy metals and other
contaminants before it can be dis-
charged into public waterways. This
is expensive and time consuming for
companies, and it drives up the cost
of consumer goods. To alleviate this
problem, Robert E. Wing and David
J. Sessa, a team of chemists at the
U.S. Department of Agriculture's
National Center for Agricultural
Utilization Research at Peoria,
Illinois, found a way to use corn
derivatives to remove the heavy
By chemically combining citric
acid-a product of fermented corn-
starch-with corn fiber, they formed

a new compound that readily com-
bines with heavy metals such as those
found in industrial wastewater. The
scientists hit on the citric acid
derivative while investigating new
ways to use corn gluten meal and
distillers' dried grains, two co-
products of ethanol processing that
are now used in foods and livestock
"Industry currently uses petro-
leum-based ion-exchange resins to
remove toxic heavy metals from
contaminated wastewater," says
Wing. "With changes in environ-
mental regulations, there is a need for
biodegradable, renewable, and cost-
effective products to treat this
The heat-modified citric acid
contains fewer hydrogens in its basic
chemical structure, making it more
reactive. This causes it to bind with
starch and protein in the corn prod-
ucts. Then, heavy metals that are
attracted to the compound that forms
can be easily filtered out of the
wastewater. Sessa says that biode-
gradable ion-exchange agents like
corn-based citric acid derivatives are
a value-added market for dried
distillers' grains and other corn
processing co-products and represent
a market niche waiting to be filled.
"Corn-based citric acid derivatives
are potentially less expensive for
industry to use than nonrenewable
petroleum-based products. They also
create another market for corn
growers," says Sessa. The Agricultur-
al Research Service is seeking a
licensing partner in industry to
manufacture citric acid modified for
industrial use. Robert E. Wing and
David J. Sessa, USDA-ARS National
Center for Agricultural Utilization
Research, Peoria, Illinois; phone
(309) 681-6353 or (309) 681-6351, e-
mail wingre @ mail. ncaur. usda. gov
sessadj @ mail.ncaur.

Agricultural Research/July 1998

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