Contents
Conserving the World's Plants
Collecting and freely sharing plants and seeds that grow around the world is
one of the U.S. Department of Agriculture's longest continuous
programs.
(K8191-21)
|
In 1898, experts were predicting food shortages and famine because
increasing population would overtake our ability to grow sufficient wheat by
1931. They may have been right--except 1898 was also the year U.S. Department
of Agriculture special agent Mark A. Carleton was sent on his first plant
exploration trip to Russia. He brought back new durum and hard red wheat
varieties to grow in the United States.
Five years after the introduction of wheat from Russia, wheat production in
the United States exploded from 60,000 to 20 million bushels a year. Not only
did the drought tolerance of these new varieties open up the Great Plains and
the Northwest for wheat growing, the durum wheat tasted better in pasta, and
the hard red wheat made better bread.
The USDA official who sent Carleton on his 1898 collecting trip would later
write, "We have forgotten how poor our bread was at the time of Carleton's
trip to Russia. In truth, we were eating an almost tasteless product, ignorant
of the fact that most of Europe had a better flavored bread with far higher
nutritive qualities than ours."
One hundred years later, USDA plant exploring and collecting, now under the
direction of the Agricultural Research
Service's National Germplasm Resources Laboratory, is still a critical
ingredient in maintaining and expanding agriculture's ability to feed an
ever-growing population.
So Many Plants, So Many Reasons
Plant exploring and collecting are essential for agriculture because crops
must be continually enhanced to overcome diseases and pests, expand drought and
temperature tolerance, adapt plants to new growing conditions, and make them
more productive, nutritious, durable, or simply better tasting. The plants that
collectors bring back often provide the genetic material for breeding improved
varieties.
Samples of seeds maintained at ARS' National Seed Storage Laboratory in Fort
Collins, Colorado.
(K8187-12)
|
"No one country or even one continent has all of the genetic resources
necessary to sustain crops at the level that is needed today," says Allan
K. Stoner, leader of the ARS germplasm laboratory. "Conditions and needs
continue to change, and collecting genetic diversity is how you have the
resources to deal with them."
This is true for most countries, because so much now being grown anywhere
either arrived there with immigrants who brought along their traditional crops
or was introduced to that country by plant explorers. Most of the United
States' major crops--fruits, vegetables, grains--originally evolved in Asia,
Europe, or South America.
Only 1 of the top 20 major world crops originated in North America: the
sunflower, which now ranks among the top 4 oilseed crops worldwide. Of course,
there are many plants indigenous to North America--including crops like
strawberries, blueberries, cranberries, forage grasses, pecans, grapes, and
tepary beans--that are collected by both U.S. and foreign plant explorers.
Interestingly, it was Russian researchers who used U.S. sunflower germplasm
to breed the varieties that started the sunflower oil industry.
"But our major crops came here from elsewhere," says Stoner.
"And when you are looking for genetic diversity, the most important places
to look are the centers of origin for crops--that is, the places where they
evolved and where people have been cultivating them the longest.
"The traditional varieties that farmers have been growing for centuries
may not be as highly productive as current varieties, but they can have genetic
traits that are exactly what we need to overcome a pest or disease
problem," he says.
The wheat that USDA plant explorer Jack R. Harlan and his Turkish colleague
Osman Tosun collected from a field in Fakiyan Semdinli, Turkey, in 1948 is a
perfect example.
At the time the sample was taken, the wheat looked terrible--it lodged, had
no winter hardiness, and was susceptible to leaf rust. By itself, "it was
a hopelessly useless wheat but was dutifully conserved," Harlan wrote of
the wheat that was listed simply as Plant Introduction 178383.
Glass tubes from a seed storage experiment. Each air-free tube carries the date
it is to be opened and its contents checked for germination in one of the
world's longest running experiments.
(K8188-8)
|
But 15 years later, when U.S. wheat breeders were looking for a way to breed
resistance to a stripe rust outbreak, PI 178383 was found to have resistance to
4 races of stripe rust, 35 races of common bunt, and 10 races of dwarf bunt--as
well as tolerance to flag smut and snow mold.
Today, PI 178383 appears in the pedigree of virtually all the wheat grown in
the Pacific Northwest.
Interestingly, it may turn out that PI 178383 did not actually originate in
southern Turkey. In 1986, ARS plant explorer Calvin R. Sperling returned to
Fakiyan Semdinli to collect more of PI 178383 and other possibly
disease-resistant wheat.
In talking with the region's farmers, Sperling discovered that they had
migrated to the area only in their grandfathers' time. They had come from
northern Iraq and brought their wheat along with them.
Wars and political instability have precluded plant exploration of the
farmers' earlier home, and no one knows if the wheat can still be found.
The Why of Plant Collecting
A sudden virulence in plant diseases or the arrival of new insect pests
illustrates another critical reason for having a standing germplasm collection
that reflects a crop's range of genetic diversity.
"It represents a crucial reservoir of breeding material that can be
turned to immediately for help when a crisis strikes," Stoner says.
When wilt and blight became unusually virulent and threatened to kill off
the Virginia spinach industry in 1920, the genes for resistance to these
diseases were found in a spinach that had been collected 20 years earlier in
Manchuria by a USDA plant explorer.
The genetic contributions of the Manchurian spinach have spread far beyond
the Virginia Savory cultivar developed to meet the original disease outbreak.
Today, the genes are present in almost every multidisease-resistant spinach
grown.
ARS botanist Karen Williams (center) and Paraguayan collaborators Pedro Juan
Cavallero (left), who is with the National Agronomic Institute, and
Fátima Mereles, with the National University of Asunción, search
for wild pepper specimens.
(K8152-2)
|
"It is impossible to judge now just what germplasm may be essential to
our future," Stoner points out. "All we can do is collect what seems
to represent the diversity of a crop and its relatives and preserve it until
that day in the future when a plant turns out to be the single most important
source of some critical trait."
Another reason for plant collecting--one that has become increasingly urgent
in recent years--is the need to preserve germplasm endangered by habitat
destruction or the loss of traditional crop varieties.
ARS plant geneticist Albert E. Percival has seen this disappearance of
germplasm while plant collecting in Mexico for traditional and wild varieties
of cotton.
"Ancestors of the fine upland cotton that is grown today in California
were originally collected in the Acala Valley of Mexico in 1906 and used in a
breeding program at the Agricultural Experiment Station in Texas," says
Percival.
But when he went to the Acala Valley in 1984 to re-collect the original
germplasm, he couldn't find any cotton at all.
"Local farmers told me that in the 1970s, a Mexican consortium decided
they were going to try to grow cotton for more than local use--as a commercial
crop. The first year they had a bumper harvest; the second year was not so
good; the third year, boll weevils destroyed the crop," explains Percival.
Growers decided to eradicate what was perceived as the source of the
infestation--the native cottons--which did not solve the problem. Growing
cotton in the region was abandoned.
"There wasn't much left to collect. It would have been nice to have
preserved those varieties for the future," says Percival. "There may
have been genes for lint quality or some other traits that we would like to
breed into today's cotton. Now they may be gone forever," he says.
Until collected during a USDA-supported plant expedition in Paraguay, this wild
pepper species, Capsicum schottianum, was unrepresented in germplasm
collections. The flowering stage is shown above.
Photo by Karen Williams.
|
Other times, it is the habitat as a whole that is in danger.
For example, Percival is concerned about an interesting race of cotton
relatives--one with twice the customary number of chromosomes--that exists only
in a 2- to 3-kilometer stretch along the coast of the Gulf of California in
Mexico and only 200 to 300 meters from the water's edge.
"But this is exactly the area that a booming tourist industry is
developing, building new hotels," says Percival. "Who knows if these
plants will survive or disappear? Yet they could well be the source of
resistance to insects."
High-Impact Acquisitions
Following is a tiny taste of the immense contributions made by USDA plant
explorers during one of the department's longest continuous programs. Corn,
dates, sorghum, soybeans, potatoes, berries, cereal grains, grapes, apples,
sugar beets, forages, carrots, onions, tomatoes, lemons, and apricots--even
camellias and lawn grasses--have all been introduced into the United States or
improved by USDA-collected germplasm.
And this germplasm has been shared with researchers, plant breeders, and
farmers in hundreds of other countries. Indeed, the descendants of collected
plants have literally changed the face of agriculture and gardening around the
world. A few examples:
· Avocados that created a California industry were brought back from
Mexico, also in 1898.
· Rice varieties collected in Japan in 1900 established the beginnings
of rice growing in Louisiana and Texas, two of the United States' major
rice-growing states today.
· A spinach collected in Manchuria in 1900 saved the Virginia spinach
industry from blight and disaster in 1920.
· Rootstock on which many U.S. peaches are now grown descends from
germplasm collected in the 1920s.
· A wild oat found in Israel in the 1960s had genes that helped
breeders develop one of the world's most disease-resistant oat varieties.
Until collected during a USDA-supported plant expedition in Paraguay, this wild
pepper species, Capsicum schottianum, was unrepresented in germplasm
collections. The fruiting stage is shown above.
Photo by Karen Williams.
|
An International Affair
Plant exploration by its very nature has always been an international
activity. But now, worldwide political developments are complicating free and
open access to genetic resources.
USDA plant explorers have always obtained permission from a host country for
collecting. Today, it is not uncommon for permission to be refused. Some
germplasm donor countries feel that they have not received a fair share of the
benefits derived from the plant resources originating in their countries.
To help change this perception and to keep the pathways of germplasm
exchange open, ARS has expanded collaborative activities associated with plant
exploration, explains ARS botanist Karen A. Williams. She coordinates the ARS
plant exploration program.
For example, Williams recently negotiated terms with Paraguayan officials
for a joint exploration trip looking for wild relatives and traditional
varieties of peppers, a popular U.S. crop that is under-represented in ARS
germplasm collections. During the exploration, Paraguayan scientists got
hands-on experience in germplasm collection.
Because Paraguay currently lacks modern facilities to maintain the collected
germplasm, ARS will provide long-term storage on Paraguay's behalf. Whenever
requested, samples of the germplasm will be sent back, ensuring that unique
germplasm will remain available to Paraguayans--no matter what habitat or
agricultural changes take place there.
In addition, ARS is helping train a Paraguayan scientist in germplasm
utilization. And to conserve wild peppers and other crop relatives in their
natural habitats, a study of the distribution of these plants is being
conducted using information from previous germplasm and botanical samples.
Working with Paraguayan institutions, ARS scientists will provide
recommendations for creation of protected areas for these plants.
"Both the United States and Paraguay are benefiting from collaboration
on the pepper exploration and associated activities," Williams says.
ARS botanist Karen Williams and Pedro Juan Cavallero record data on a wild
pepper found near a Toba tribal settlement in Paraguay.
(K8152-3)
|
Germplasm collected on USDA-supported explorations is deposited into the
National Plant Germplasm System, where it is freely available to breeders and
other researchers. Agriculture around the world, including in the United
States, has benefited enormously from the extensive amount of germplasm that
has been made available since the beginning of the USDA program in 1898,
Williams says.
In the Beginning
The formal USDA collection program began with a single Congressional
appropriation of $20,000 in 1898 and the hiring of David Fairchild as chief, a
position he held until 1928.
What Fairchild's plant explorers brought back during this period profoundly
affected agriculture in the United States.
In addition to Carleton's Russian wheat, avocados, navel oranges, and other
tropical fruit varieties collected by Wilson Popenoe in South and Central
America created new U.S. industries. The rice brought back by Seaton A. Knapp
from Japan not only opened up rice-growing in Louisiana and Texas, it turned
the United States into an exporter of rice instead of an importer. Fairchild
himself brought back dates, pima cotton, pistachios, gooseberries, olives,
walnuts, and many other specialties.
And then there was Frank N. Meyer. Considered the dean of USDA's
agricultural explorers, from 1905 to 1918 he introduced thousands of plants.
Although he is not well known to the public today, consumers benefit from the
bounty he brought back every time they shop for groceries.
Collecting mostly in Asia and Russia, Meyer sent back new crops--from
alfalfa sprouts to zoysia grass. Apples, barley, chestnuts, bean sprouts,
Chinese celery-cabbage, and the Meyer lemon, which is an important source of
frozen lemon juice and is grown commercially in Texas, South Africa, and New
Zealand--these just scratch the surface of what Meyer collected.
At the Plant Genetic Resources Conservation Unit in Geneva, New York,
horticulturist Philip Forsline examines hybrid grapes developed in a USDA
breeding program.
(K5338-7)
|
He also brought back landscape plants and ornamentals: Bradford pears, dwarf
lilacs, Amur cherry, gingko trees, and a rose that provided the rootstock on
which millions of roses still bloom in the United States each year.
Most widely used of all the drought-resistant trees that Meyer collected
were Siberian and Chinese elms. When the drought of the 1930s began to turn the
prairie states into the Dust Bowl, Meyer's elms formed a large part of the
17,000 miles of shelterbelts that were created to reduce wind erosion. These
tree-lined windbreaks planted between 1935 and 1942 helped conserve millions of
tons of soil.
One of Meyer's most significant contributions was soybeans. Before he went
to China in 1905, only eight varieties of soybeans were grown in the United
States, and these were for animal forage. Between 1905 and 1908, Meyer added 42
new soybeans, which have parented thousands of varieties over the years.
Among the soybeans that he collected was the one that gave rise to soybean
oil production, an industry worth billions of dollars today.
One contribution of his did not quite take: Meyer was ahead of his time in
the early 1900s, when he advocated that the United States should pick up on an
Asian soybean industry and begin producing a food called tofu.
It is hard to track the impact of what Meyer and other USDA explorers
brought back, because it can be decades before selections from a collected
plant can be further developed into a new variety. For example, the zoysia
grass that Meyer collected in the early years of the century did not evolve
into a commercial variety until 1951.
Fairchild established the plant inventory system that remains in operation
today. Each accession that enters the germplasm system, whether it is collected
by a plant explorer or the result of a breeding program, is given a plant
introduction number.
The first, PI 1, was a cabbage accession from Moscow, Russia. Collected in
1898, it was said to mature a little earlier than the Jersey Wakefield but to
form heads too small for market.
Recently, PI 600,000 was awarded to a pollinator sunflower with
shorter-than-normal height. It promotes high yield in hybrids and was developed
in an ARS breeding program.
Plant Introduction Stations
New accessions today receive PI numbers only after an evaluation is done to
determine that a plant represents new germplasm for the collections. Germplasm
is often sent to one of four Regional Plant Introduction Stations managed by
ARS at state agricultural experiment stations (SAES) at Ames, Iowa; Geneva, New
York; Griffin, Georgia; and Pullman, Washington. These sites were originally
chosen to represent the main agricultural environments in the United States.
The plant introduction station system created in 1948 by USDA and the SAES
to maintain the collections of different crops is celebrating its 50th
anniversary this year.
ARS also set aside some locations for specialized germplasm collections and
in the 1980s, again with the SAES, established repositories for clonally
propagated fruit and nut crops.
All of these sites concentrate today on maintaining, characterizing, and
distributing the active collections for particular crops.
Apples in the ARS germplasm collection at Geneva, New York, vary widely in
size, shape, and color.
(K5339-3)
|
"Because the collections have gotten so large and resources are always
limited, we focus on a core collection--about 10 percent of the main
collection--that reflects the basic genetic diversity of a crop that a
researcher would need to screen to find a source for a particular trait,"
explains Philip L. Forsline, who is curator of the ARS apple collection at
Geneva. It keeps cool-season grapes, Brassica (broccoli, cauliflower,
mustard, turnip), tomatoes, and some minor crops, as well as the apples
in which Forsline specializes.
"In the apple collection alone, we have more than 2,000 named
varieties. However, most of them, whether they are French cider apples or
domestic varieties from North America, New Zealand, or South Africa, come from
a very narrow genetic base," Forsline says. "That is why we have made
four trips since 1989 to collect wild varieties in Kazakhstan, the center of
origin for apples."
Whether breeders are trying to create a new flavor or respond to an outbreak
of apple scab, they turn to the collection at Geneva as the definitive
reservoir of apple genes.
On the other hand, long-term storage of the entire germplasm collection is
the job of ARS' National Seed Storage Laboratory (NSSL) in Fort Collins,
Colorado.
"We provide the backup to the active collections," says Steve A.
Eberhart, who heads the lab. "We are sort of the Fort Knox for
plants."
If a tornado, fire, or other disaster ever hit one of the plant introduction
stations or other ARS germplasm banks, NSSL could replace lost varieties,
Eberhart explains.
As one of the most advanced plant and seed storage facilities in the world,
NSSL has been asked by some countries and international agricultural research
centers to keep samples of their valuable collections. For example, the
International Rice Research Institute in the Philippines has asked NSSL to keep
a secure backup of its rice germplasm because of concern that a typhoon could
destroy parts of the collection.
So far, IRRI has not had losses from a natural disaster, but NSSL was able
to replace a few varieties that had been lost in the normal course of growing.
"The seeds we keep secure here," says Eberhart, "are truly
the world's treasure."--By J.
Kim Kaplan, Agricultural Research Service Information Staff.
The scientists in this article can be contacted through Kim Kaplan.
"Conserving the World's Plants" was published in the
September 1998 issue of Agricultural Research magazine. Click here
to see this issue's table of contents.
[Top]
|