At the Root of Civilization: Crop
Staff at the National Seed Storage Laboratory in Fort Collins, Colorado,
preserve more than 1 million samples of plant germplasm. Here, technician Jim
Bruce retrives a seed sample from the -18 ºC storage vault for testing.
Busy times are ahead in the new millennium for the
Agricultural Research Service, chief
scientific arm of the U.S. Department of Agriculture. Its job in the decades
ahead will be to help sustain agriculture's ability to meet humanity's growing
demand for food, fiber, and other needs. A world population expected to reach 8
to 10 billion individuals by 2050 demands as much.
While America's domestic crop yields have generally increased by 1 percent
annually, the new millennium will require that science push the technological
envelope much further. In the United States, it's worth noting that the actual
task of producing food and fiber now rests with less than 2 percent of our
nation's population: farmers. They're also the ones who put into practice what
agricultural scientists at ARS, universities, and elsewhere explore in the
At the heart of all this, though, are the plants cultivated as our crops.
Since humankind's agricultural beginnings thousands of years ago, we've placed
on plants the burden of sustaining human populations. In the process, we've
removed many plants from their natural habitats and imposed on them a new set
of variables under which they're expected to flourish.
With the label of "crop," for example, have come new conditions
that concentrate the plants into defined areas, often arranged in uniform rows,
and within easier grasp of insect pests or pathogenic organisms that cause
So as we demand more of crop plants, it becomes even more critical to
preserve, protect, and improve these leafy green cornerstones of civilization.
In this article, you'll read about a few of the many research projects of ARS
scientists working to further these three basic goals. As part of a national
research priority called Crop Production, Product Value, and Safety, their work
is helping ARS be of service to both the agricultural community and its myriad
20th Century Achievements Set the Stage
For plant physiologist Donald R. Ort and colleagues at ARS' Photosynthesis
Research Laboratory (PRL), in Urbana, Illinois, the effort begins with studies
on the biochemical machinery by which plants make their food (carbohydrates)
and, ultimately, our own.
Nature has endowed plants with the amazing ability to energize their food
production machinery with sunlight. They're also quite adept at using other
resources from the natural environment around them. Yet, despite the
magnificence of nature's design, photosynthesis is often incapable of operating
at its full potential, says Ort.
Plant pathologist Robert Goth and geneticist Kathleen Haynes examine tuber
characteristics of late-blight-resistent potato selections.
But modern agriculture suggests the opportunity for improvement.
At Urbana, PRL researchers like Archie R. Portis, Jr., are focusing
attention on rubisco. It is a key enzyme in photosynthesis that captures carbon
dioxide (CO2), a basic building block of carbohydrates. In keeping
with its fundamental importance to life on Earth, says Ort, rubisco is an
extraordinarily ancient enzyme that evolved when the planet's atmosphere lacked
"Because of this, rubisco never learned how to distinguish
CO2from oxygen," he explains. "The outcome of this
evolutionary error in today's atmosphere is that, in plants like soybean,
rubisco captures oxygen instead of CO2 about 20 percent of the
To tackle the problem, Portis, Ort, and colleagues are trying to genetically
replace the rubisco of soybean plants with an enzyme from green algae that
captures CO2 more quickly. "Soybean plants engineered in this
way will be particularly beneficial at the higher atmospheric CO2
concentrations that the next century will usher in," predicts Ort.
The challenge in the next century, he adds, will be to maintain crop
productivity in the face of greater temperature extremes, water shortages, and
an increasing need to cultivate on marginal land. "Improving the
photosynthetic performance of crop plants for these environments holds
important promise for U.S. agriculture as it enters the new millennium,"
Elsewhere in Illinoisat ARS' National Center for Agricultural
Utilization Research (NCAUR) in Peoriascientists are working to convert
starch, protein, oils, and other raw materials gleaned from corn, soybeans, and
oilseed crops into value-added products.
NCAUR accomplishments include refining early techniques for mass-producing
penicillin, creating the widely used absorbent starch-based material called
Super Slurper, and making printing ink from soybean oil.
A more recent achievement from Peoria scientists is Fantesk. It's a
composite product prepared from mixtures of cornstarch and oil by a
high-temperature, high-pressure cooking process, says chemist and co-inventor
George F. Fanta. He and Kenneth Eskins (now deceased) developed and patented
the technology, along with colleagues in NCAUR's Plant Polymer and Biomaterials
Processing Research Units.
Fanteskin its liquid, powder, flake, or gel formoffers a slew of
promising industrial, agricultural, and consumer uses. Fanta reports the
technology has already been licensed by the private sector for seed-coating
applications. Other applications now under development with commercial partners
include cosmetics, water-based lubricants, new drug delivery systems, and fat
replacers for use in baked goods, ice cream, and ground meat like hamburger, he
Keeping an Eye on Some Fungi
If you were to charter a boat down the Mississippi River south to Louisiana,
you'd end up in New Orleans, home of ARS' Southern Regional Research Center.
There, scientists are focusing attention on exploiting not only corn, but
cotton, rice, peanuts, and other southern crops as well.
At the center's Food and Feed Safety Research Unit, for example, you'll find
researchers like Peter J. Cotty on the cutting edge of technologies to
eliminate aflatoxin, a potential food safety threat. Aflatoxin is a natural
carcinogen produced by certain species of Aspergillus fungi that can
grow on cottonseed, peanuts, corn kernels, and other grains. Even small
concentrations of aflatoxin can render these crops unfit for human or animal
consumption, says Cotty.
Technician Jolene Hansen examines seeds preserved in a vat of liquid nitrogen
that can hold 5,000 containers of up to 2,000 seeds. The longevity of
cryopreserved seeds is projected to be hundreds of years, but scientist
periodically remove them to assess their viability and vigor.
One product of New Orleans' anti-aflatoxin research is a biological
pesticide for treating cotton crops. Spores of benign, or atoxigenic,
Aspergillus fungi constitute the biopesticide's main ingredient. In
treated field plots, the helpful Aspergillus reduced
aflatoxin-producing strains by over 90 percent through a natural phenomenon
called competitive exclusion.
Developed by Cotty, New Orleans colleagues, and cotton trade groups, the
biopesticide is now being registered with the U.S. Environmental Protection
Because of its arid climate, Arizona is one of the states hit hardest by
aflatoxin, says Cotty. Severe outbreaks have cost its cotton industry $3 to $8
million annually in losses. About 10,000 acres have already been treated with
the biopesticide under an EPA experimental use permit for Arizona's statewide
aflatoxin elimination program, which began earlier this May.
"Preliminary test results from earlier years were promising," says
Cotty, a plant pathologist. "They showed that applications of atoxigenic
strains can have both long-term and areawide influences on the
In the mid-Atlantic region, at ARS' Beltsville (Maryland) Agricultural
Research Center's Vegetable Laboratory, scientists Autar K. Mattoo, Kenneth L.
Deahl, Kathleen G. Haynes, Robert W. Goth, and Richard W. Jones are battling a
fungal menace of another kind: Phytophthora infestans. It causes
potato late blight, the disease that triggered the Irish potato famine in the
Today, new fungicide-resistant races of late blight have surfaced and are
the focus of breeding efforts to arm growers with new potato varieties that can
withstand the disease. Late blight's renewed virulence has cost U.S. potato
growers hundreds of millions of dollars and inflicted heavy losses in Peru,
where many new sources of germplasm are found. For this reason, the Vegetable
Laboratory's work is closely tied to that of Peruvian researchers and
university collaborators in New York, Washington, Oregon, Michigan, and other
In addition to disease resistance, another focus of Mattoo's lab is
improving the marketability and nutritional offerings of tomatoes, potatoes,
peppers, eggplants, and other vegetables. Geneticist John R. Stommel, for
example, has bred new lines of processing tomatoes that yield orange-colored
fruit high in beta carotene. That's an important precursor of vitamin A, which
aids human bone growth and improves eyesight.
Mattoo, meanwhile, has used molecular bioengineering to produce processing
tomatoes with longer shelf life and increased lycopene, a potent antioxidant.
Molecular genetics, he says, will figure more prominently in tomorrow's crop
nutrition research, as well as in explorations of ways to regulate plant aging,
or senescence. The discipline will also help in deciphering the roles of plant
growth regulators, such as polyamines and ethylene, in tomatoes and other
Packing More Nutrition Into Tomatoes
In research to improve tomato varieties, geneticist John Stommel uses
protoplast fusion to construct a somatic hybrid that combines the wild species
Solanum ochranthum and a tomato.
Similar work is under way in Betty K. Ishida's laboratory. She is a
biologist in ARS' Western Regional Research Center's Processing Chemistry and
Engineering Research Unit at Albany, California. There, Ishida has devised a
lab technique for growing cherry tomato fruit from a tissue culture of calyx
Normally, these cells are programmed to develop into the tiny green stem and
leaflets that crown the tomato's top. But in the lab, Ishida's technique coaxes
them into becoming more like the tomato's fruiting tissue instead. Her
procedure also boosts the tissue's lycopene content tenfold. Epidemiological
studies suggest that lycopene can reduce the risk of prostate, lung, and other
cancers and prevent cell damage caused by harmful substances called free
radicals in the body.
Eventually, Ishida's work may benefit consumers by giving rise to new,
high-lycopene tomato varieties. The key, she says, is finding a biochemical
signal that will activate lycopene-encoding genes and proper ripening under
field or greenhouse conditions. The scientist has already identified one
important gene, called agamous.
"It's one of the genes that function early in the flower's development
and are important in determining which part of meristem tissue will become a
petal and which the fruit," Ishida explains. "I also need to know how
these things are being triggered."
At the Foundation: Genetic Diversity
Agriculture is like a building in that it, too, relies on a solid
foundation. In terms of crops around which modern-day agriculture operates,
that foundation is genetic diversity, often manifested as plant germplasm. This
includes seed, pollen, cuttings, buds, and other plant material. From it,
breeders can acquire novel genes and incorporate them into new cultivars of
crops to impart traits like better disease resistance, improved yield, or
USDA has long recognized the importance of genetic diversity to America's
crops. In 1898, 55 years before it created ARS, the department commissioned its
first official plant explorer, Mark A. Carleton, on a wheat-collecting
expedition to Russia. The durum and hard red winter wheat specimens he returned
with not only expanded the grain crop's U.S. production area, but also
subsequently improved the quality of domestic flour used for bread and other
baked goods (see "Conserving the
World's Plants,"'Agricultural Research, September 1998, p.
Collecting, as well as preserving and regenerating plant material, is still
a top priority. Through international germplasm exchange agreements and
generations of plant explorers since Carleton's time, some 450,000 collected
specimenscalled accessionsare now kept at about two dozen
ARS-operated repositories located across the country. Each is part of a larger
network, namely the U.S. National Plant Germplasm System (NPGS). Its many
dedicated curators readily make the material available for research purposes
and plant breeding.
One such curator is Loren E. Wiesner, a plant physiologist who leads Seed
Storage and Viability Research, a unit at ARS' National Seed Storage Laboratory
in Fort Collins, Colorado. Established in 1958, the lab is the backup
repository for 327,236 germplasm accessions and home to the latest technologies
for preserving them.
"To date, we have 81 percent of the seed accessions and 6 percent of
the clonal accessions backed up at NSSL," reports Wiesner.
At Fort Collins, scientists place new samples collected from around the
world in sturdy, climate-controlled vaults capable of withstanding natural
disasters such as floods and tornadoes. Placement into the vault is done only
after scientists have first screened new specimens under quarantine for exotic
Botanist Diane Pavek says preserving rock grapes in their native U.S. habitat
will help ensure that their unique genes are available for long-term use in
breeding new, hardy grape varieties.
Some specimens are placed in the vapor of liquid nitrogen at -160 °C.
The technique, called cryopreservation, has become a staple of modern germplasm
research because of its ability to extend a seed's life span for hundreds of
years. And soon, gene marker technology could help in deciphering a germplasm
specimen's DNA code, revealing new information about its lineage, storage, or
use in plant breeding efforts.
But why the need for such elaborate accommodations and high technology?
"Genetic resources are needed to maintain productivity of our food,
feed, and fiber crops because new strains of disease develop, new insects
invade our country, and requirements for food quality change," says
Take the Russian wheat aphid (RWA) for example. Six years after this exotic
insect's detection in Texas in 1986, the aphid had spread to 50 percent of the
western United States' irrigated winter wheat, 14 percent of spring wheat, and
33 percent of barley.
"When it was determined that RWA was a threat to our wheat crop, many
plant breeders in the western states obtained various wheat accessions from the
NPGS," says Wiesner. "Once resistant accessions were identified,
plant breeders began to use them in their breeding programs. One of the first
resistant cultivars, a winter wheat called Halt, was released by Colorado State
Collecting, preserving, and describing plant germplasm become increasingly
important as more of the natural habitats of crop plants' wild relatives are
lost to human sprawl, pollution, and natural disasters.
Cooperation among nations is particularly vital in that regard, says Henry
L. Shands, the ARS assistant administrator for genetic resources.
"The obstacles to collecting today are many," says Shands, who is
now on detail at the World Bank Group's Rural Development Department in
Washington, D.C. "Most notable are the access issues from political and
bureaucratic arenas. There are also numerous security issues for collectors.
And, physically, the world is not all paved roads and easy
For these reasons, "exchange programs aren't important just to the
United States, but also to those countries unable to collect and protect their
own resources," says Shands.
Wiesner adds, "International cooperation is vital in that it's
impossible for any one country to store and maintain all of the genetic
resources needed to improve or maintain its agricultural production."
Only in this environment, Wiesner and Shands both agree, can the seeds of
agriculture's future take root and flourish.By
Jan Suszkiw, Agricultural
Research Service Information Staff.
To learn more about ARS' vision for plant research into the next
century, see the agency's World Wide Web page for Crop Production, Product
Value, and Safety at http://www.nps.ars.usda.gov/programs/cppvs.htm.
For information about scientists in this article, contact
Jan Suszkiw, USDA-ARS
Information Staff, 5601 Sunnyside
Ave., Beltsville, MD 20705-5129; phone (301) 504-1630, fax (301) 504-1641.
"At the Root of Civilization: Crop Plants" was published in
1999 issue of Agricultural Research magazine.