From Arboretums to
A red rose, symbol of love
and tasty treat for spider
mites. This issue of the
magazine looks at several
ARS efforts to keep valuable
floral and nursery crops
like roses and woody
ornamentals safe from the
many pests that plague them.
|For almost 75 years, the U.S.
National Arboretum's Floral and Nursery Plants Research Unit (FNPRU) has been a
leader in the development of new and improved floral and nursery products. The
446-acre arboretum's advances in genetic improvement and disease control of
landscape plants and major cut flowers have, in no small part, contributed to
the rapid growth of the floriculture crop sector of American
agriculturewhich had a $3.5 billion wholesale value in 1998. (See
"Floral Gems," Agricultural Research, September 1997, pp.
FNPRU's research activities have helped spur the burgeoning floral and nursery
crops industries in myriad ways. From their germplasm improvement, taxonomy
studies, and development of virus- or pest-resistant plants to the creation of
plant pathogen detection methods and genetic transformation technologies, the
research unit's scientists continue to engage some of the horticulture
industry's most enduring challenges.
Technician Brandy Jones
examines a rose plant
that began as cells
grown in a tissue culture.
|"A 1996 horticulture research
initiative spearheaded by ARS
Administrator Floyd P. Horn has been tremendously beneficial to the
industry," says Mary Ashby Pamplin. She previously directed horticultural
research for the American Nursery and Landscape Association.
"Through labs like the FNPRU, ARS does something that we as an industry
cannot; that is, conduct the long-term, high-risk, and costly basic research
that forms the building blocks for the industry's own research programs,"
Pamplin says. "ARS is in a perfect position to coordinate research across
disciplines at a very high level and to effectively communicate its
This cooperation with industry informs much of what ARS scientists accomplish
at FNPRU and at the more than 100 ARS laboratories across the country and
abroad and provides researchers with an incentive to find solutions to
New Chinese redbud cultivar named
Don Egolf, released by Margaret
Pooler of the U.S. National Arboretum.
| Over the last 10 years, the FNPRU
has been engaged in detecting, identifying, and characterizing several viruses
affecting ornamental crops. Among the tools scientists use are antibodies,
electron microscopy, and nucleic acid hybridization. These approaches include
developing control procedures to prevent or minimize virus transmission,
finding reagents to quickly detect and screen viruses, and quarantine
interception and epidemiology.
Following are some research programs that highlight the depth and breadth of
Roses at the Secrest Arboretum in
|Using Genetics To Plum the Depths
of Plant Diseases
The plum pox virus (PPV) research program, led by plant pathologist John
Hammond, has yielded sensitive detection techniques that not only confirm the
presence of PPVa disease that affects stone fruits like plums, peaches,
and their ornamental relativesbut also distinguish between severe and
less virulent strains of the disease and help determine their origins and modes
of transmission. (See related story on p. 9.) To the $1.3 billion annual U.S.
stone fruit industry, this kind of research is critical.
Hammond uses a technique called the polymerase chain reaction (PCR), which
multiplies the number of target molecules in a sample's nucleic acid. Having
enough copies helps researchers detect any particular strain of PPV.
"We've been able to develop PCR primers that initiate this process,"
says Hammond. "The process allows us to more readily detect all PPV
strains." If scientists can detect different strains, it may help them
find a correlation between a particular strain and its ability to infect a
specific type of host plant.
Technicians Brandy Jones (left)
and Siobhan OConnor examine
rose cultivars regenerated
from somatic embryos in tissue
culture. This technique will be
used to genetically engineer
roses for disease resistance.
|New Redbuds and Lilacs Grace
FNPRU's Margaret R. Pooler has released a new Chinese redbud cultivar named Don
Egolf, a variety of Cercis chinensis whose profusion of rosy-purple
flowers, compact structure, ease of propagation, seedlessness, and apparent
high tolerance to Botryosphaeria dothidia canker have made it a welcome
newcomer to nurseries across the country. Since 1994, cooperating nurseries
throughout the eastern, southern, and midwestern United States have evaluated
Don Egolf with high acclaim. Its ease of propagation by rooted cuttings is an
especially valuable trait, because redbud cultivars are notoriously difficult
to propagate. Because the cultivar is seed-sterile, it produces no
fruitenhancing the shrub's winter appearance.
In addition, Pooler's release of a new Syringa cultivar named Betsy Ross
has provided the industry with a new lilac acclaimed for its fragrant white
flowers, lush green foliage, compact growth habit, disease tolerance, and
adaptation to warmer climates. One significant advance has been the new lilac's
tolerance to powdery mildewthe biggest disease problem for lilacs in the
Washington, D.C., area. The new shrub thrives under full sun and can be used as
a background planting in a shrub border or as a specimen plant or hedge. It can
be planted throughout USDA hardiness zones 5 to 7.
The new lilac cultivar named Betsy
Ross, released by Margaret Pooler
of the U.S. National Arboretum, has
fragrant white flowers and tolerates
|A Rose Is a Rose Is a Rose
Researchers at FNPRU have also developed a new technique to enable
transformation of genetically diverse varieties of rosesthe number-one
cut flower in the United States. One of the principal obstacles to the genetic
engineering of roses has been an inability to develop a whole plant from
genetically engineered cells. "This technique has already been applied to
three rose varieties with great success," says Kathryn K. Kamo, a plant
physiologist. The new method can potentially be used to genetically introduce
traits such as resistance to black spot, along with quality traits, like scent,
color, and heat tolerance.
Nightmare on Elm Street Is Over
The tree-breeding program at FNPRU has successfully bred red maples with both
good fall color and leafhopper resistance; elms with tolerance to Dutch elm
disease and elm yellows; superior alder and hackberry; and hemlock with wooly
adelgid resistance. New hemlock hybrids are being verified with the use of
A picturesque scene at the
|Over the past 20 years, plant
geneticist Denny Townsend has worked to develop the first commercially
available elm varieties that are tolerant to Dutch elm disease. After their
long-awaited arrival in wholesale nurseries in 1997 and retail nurseries in
1999, the American elm is well on its way to gracing our boulevards and
backyards once again.
Novel Approaches to Plant Breeding
Plant geneticist Robert J. Griesbach, with FNPRU, has been developing five new
Ornithogalum hybrids. The best-known species of this bulbous plant is
the Star-of-Bethlehem. These new hybridsfor which patent applications
have been filedintroduce new colors and growth habits through
interspecific breeding and embryo rescue techniques. The introduction of
disease resistance is projected in the future through genetic engineering.
According to Griesbach, he and colleagues have been able to develop whole
plants from rescued embryos that have been germinated from immature seeds.
"Under normal circumstances these embryos would die," he says.
"The resulting plants have larger, fuller flowers and stronger, longer
As part of the IR-4
program to test pesticides
for use on minor crops,
technician Betsy Anderson
sprays a chemical on
| Minor Crops Make Major Impact
Recognizing the economic importance of the $32-billion-a-year U.S.
"minor" crop industry, the FNPRU is a major participant in an
ornamental minor-use pesticide (IR-4) program. The IR-4 program's role is to
conduct the research necessary to receive Environmental Protection Agency (EPA)
approval of pesticides for use on minor cropsthose grown on 300,000 or
fewer acres in the United States. Large agricultural chemical producers
normally play this role for products geared to large-scale crops, like corn and
wheat, that will allow them to recoup their investment in research and testing.
Minor crops do not provide such an incentive. That's where the IR-4 program
FNPRU plant pathologist James C. Locke conducts pathology and entomology
studies in support of the IR-4 program. "Another of our projects involves
development of nonpesticidal approaches to control soilborne and foliar fungal
pathogens using biological control agents and natural plant products,"
says Locke. He plans to further develop one such producta clove oil
formulationwith the help of industry cooperators.
The ornamental minor-use pesticide program relies on another arboretumthe
Ohio State University's (OSU) 85-acre Secrest Arboretum, in Wooster, Ohio. ARS
pesticide-application scientists there have a decided advantage, with their
laboratory and offices on OSU's 2,400-acre Ohio Agricultural Research and
Development Center, which also has nurseries, greenhouses, and adjoining
"When we want to do field tests for IR-4, we have the arboretum available
as well as the nurseries and greenhouses," says Charles R. Krause, who
heads the ARS Application Technology Research Unit. This unit conducts basic
research to reduce pesticide use while improving disease and pest control and
enhancing profitability for growers. Several other ARS units as well as OSU and
other land grant universities nationwide participate in the IR-4 program.
The Wooster arboretum has one of the oldest and best collections of Japanese
yew trees in the world and one of the largest collections of crabapple trees in
the country. Its landscape is beautiful year-round, but puts on its best show
for Mother's Day, with numerous red and white and pink azaleas and
rhododendrons blooming along with the pink crabapple flowers. It's not hard to
see the economic value of all this beauty to customers of commercial nurseries
and greenhouses. One acre of the red maples on the arboretum's grounds would
bring several thousand dollars in sales to commercial operations.
Tourist season peaks in spring, but locals enjoy the arboretum year-round,
taking self-guided tours or walking and jogging the paths.
Krause's unit partially supports the arboretum with equipment and services and
in turn uses the arboretum's research facilities for testing new pesticides and
the best and safest ways to apply them. For example, the crabapple collection
serves the unit well during its current focus on apple scab, a fungus that
attacks the trees. Krause or his colleagues can drive less than a mile from
their lab to the arboretum, take a crabapple leaf sample suspected to have
apple scab fungus, and examine it with one of ARS' new scanning electron
microscopes in a matter of minutes.
Using apple scab as a hypothetical example of how IR-4 works, Krausewho
has been with the program since the ornamental component was added in
1977describes the process: "Nursery or greenhouse people go to their
county extension agents and tell them that the pesticides they're using are no
longer doing the job. They've heard that a newer fungicide works better, but
it's not labeled to control apple scab fungus, so they can't legally use it on
crabapple trees. The agent would start a long, careful process in which the
IR-4 headquarters at Rutgers University would first contact the
registrantthe company that makes the newer fungicideand ask them if
they agree with the request. If they don't, the whole process stops right
there." Efficacy, marketing, and patent liability are some reasons why the
registrant might reject label expansion.
If, on the other hand, they say yes, then committees of experts at annual
workshops study the request to check its feasibility. If the request passes
through several layers of approval, the project is assigned to an appropriate
lab, such as Krause's, to see how the newer fungicide works on crabapple trees.
If everything works out, the company uses the research data to apply for EPA
permission to add crabapple trees to the legal uses on the fungicide's label.
The fungicide could be a synthetic chemical formulation or it could be a
If the new label request is for potted plants, Krause would buy about 20 of the
plants in pots or containers and test the newer pesticide on them in the
arboretum. He would see if the pesticide damaged the appearance of the plant,
was effective against the problem pests, and was safe for the environment,
wildlife, pets, and peopleincluding people who would live or work near
the plants and children who might sample the plants. Also, if the plant were to
be widely used inside office buildings, it would be important that the
pesticide not have a strong odor.
Krause says he sees IR-4started to keep pesticides available and safe for
food cropsas a model for cooperation among state and federal agencies,
private companies, environmentalists, and consumers. The IR-4 program, which
stands for Interregional Research Program No. 4, was established in the early
1960s and gained momentum after the Federal Insecticide, Fungicide, and
Rodenticide Act was amended in 1988.
IR-4 ensures that the United States has the safest food and ornamental plant
products in the world because of its system of checks and balances, including
regulation by EPA, says Krause. There are many regulations protecting food and
ornamental plants, such as the Food Quality Protection Act of 1996. He says he
is proud to be a pioneer member of the diverse team of researchers who ensure
this and is grateful for the great outdoor lab the Secrest Arboretum offers.
People increasingly come to greenhouses, garden shops, or nurseries to buy
landscape plants for beauty, shade, privacy, wildlife benefits, or noise
abatement. Krause and others work to ensure that ornamentals shipped to garden
centers across the United States are in beautiful shape and have no levels of
pesticides that could harm the elderly or children, and no offensive odors.
The IR-4 work is a good fit with Krause' group, since their basic charge is to
find the best and safest ways to apply pesticides to food plants and
"We have to get the pesticide to the target for it to work," Krause
says. "It doesn't matter how good the pesticide is if you can't reach the
pest with it."
While they are testing a newer pesticide for a broader application labeling,
they will change the labeled application procedures to include safer and more
efficient application methods that result from their testing.By Jesús
Agricultural Research Service Information Staff.
The National Arboretum research is part of Plant, Microbial, and Insect
Genetic Resources, Genomics, and Genetic Improvement (#301), Plant Biological
and Molecular Processes (#302), and Plant Diseases (#303). The Wooster, Ohio,
research is part of Plant Diseases (#303) and Crop Protection and Quarantine
(#304). These four ARS National Programs are described on the World Wide Web at
Margaret R. Pooler,
Kathryn K. Kamo,
Alden M. Townsend,
Robert J. Griesbach, and
James C. Locke are in the USDA-ARS
Floral and Nursery Plants Research Unit, BARC-West, Beltsville, MD 20705-2350;
phone (301) 504-6570, fax (301) 504-5096, (301) 344-3441 [Townsend's fax].
Charles R. Krause
is in the USDA-ARS Application
Technology Research Unit, 1680 Madison Ave., Wooster, OH 44691; phone (330)
263-3672, fax (330) 263-3841.
"From Arboretums to Your Garden" was
published in the September 2001
issue of Agricultural Research magazine.