Botanist Diane Pavek (center, foreground) examines rock grapes growing at a
proposed conservation site within Great Falls National Park in Maryland.
Why In Situ?
Last year, Diane Pavek spent the summer exploring more than 12,000 miles
across states from Pennsylvania to Texas. She was searching for rock grape,
Vitis rupestris, one of 15 species of wild native American grapes.
Her mission: preserving populations of native rock grape plants in situ, on
site in their native habitat, as part of an ecological preserve. It's an
ongoing activity of the National Plant Germplasm System. The system stores,
catalog, preserves, and enhances germplasm of individual plants or plant
populations with unique genetic makeup for breeding new plant varieties.
Most of the seeds and plant tissues that are in the germplasm system have
come from foreign countries, since few major food or fiber crops are native to
the United States.
But the United States has some native plants that are related to valuable
cultivated plant species. These include wild relatives of grapes, sunflowers,
Jerusalem artichokes, potatoes, onions, garlic, and several species of nuts,
small fruits, and forage grasses.
Botanist Diane Pavek says preserving rock grapes in their native U.S. habitat
will help ensure that their unique genes will be available for long-term use in
breeding new, hardy grape varieties.
"Wild ancestors and relatives of cultivated plants are the key to
genetic diversity that gives us the sustained ability to develop new plant
varieties that can resist pests, diseases, and environmental stresses,"
says Pavek, an Agricultural Research
Service botanist in the Plant Exchange Office of the National Germplasm
Resources Laboratory. The laboratory is located at ARS' Beltsville (Maryland)
Agricultural Research Center.
"As the habitat where plants grow wild continues to shrink, many
valuable plant species and varieties are disappearing forever," Pavek
says. Rock grape, in fact, is listed by The Nature Conservancy--a nonprofit
plant, animal, and habitat conservation organization--as vulnerable to
extinction because of habitat loss.
"But we may not need to put all the wild relatives of a crop into a
gene bank. It may be more practical to preserve these native plant species in
place," says Pavek.
Grapes, onions, and potatoes are among the many crops that may benefit from
Natives With Proven Genetic Value
Preserving rock grape germplasm isn't just insurance for the future--it has
already proved its importance.
Rock grapes rootstock is important to the U.S. grape industry, since it is
resistant to one of the world's most destructive grape
"Rock grape is prized as rootstock and breeding material because of its
excellent disease and insect resistance and adaptability to harsh environmental
conditions," Pavek says.
In the late 1800s, rock grape was one of two native American grape species
that saved European vineyards from phylloxera, an insect pest that threatened
to wipe out European viticulture and is still a threat to grape crops
Back then, nearly all European grapes were grown on their own rootstock.
"Today," says Bruce Reisch, a Cornell University grape breeder,
"all European grapes are grafted onto rock grape rootstock or rock grape
After exhaustively researching regional and local U.S. herbarium collections
for specimens, Pavek went looking for rock grape across 10 states. The sites
she looked at were gravel bars or rocky areas along rivers and large creeks,
the only settings where rock grape grows. Flooding easily uproots and
redeposits the plants along the waterways.
At each site, Pavek took leaf samples for DNA screening and made
measurements of the plants.
"Characterizing genetic diversity and its distribution throughout the
species' range enhances our understanding of adaptation and survival of wild
species. It also ensures that genetic resources are available for study or use
in breeding programs," she says.
Back at the lab, Pavek analyzed the physical structure of 238 plants growing
along 19 waterways. Such analyses emphasized different aspects of the plant for
choosing populations for in situ preserves. She found significant differences
in physical structure--called morphology--among and within these populations
for all the variables she measured.
"These analyses suggest that in situ preserves may be necessary in the
western, central, and eastern parts of the rock grape's range," says
Pavek. She has proposed seven populations in four states as in situ preserves.
She also sent samples from 113 plants to Warren F. Lamboy, grape germplasm
curator with the USDA-ARS Plant Genetic Resources Unit at Cornell University in
Geneva, New York. He evaluated plant populations for their genetic diversity
using DNA markers.
Wild Allium belonging to the onion, garlic, and leek family bloom on the
Turnbull National Wildlife Refuge in eastern Washington.
"Certain populations were more diverse than others," he says.
"And some displayed unique DNA charac teristics that make them more worth
"What's most alarming," Pavek says of her exploration experience,
"is the loss of places where the grapes were previously reported as
growing. Of the 60 sites in 10 states originally described in U.S. herbarium
collections, we discovered just 24 populations of rock grapes growing in only 9
"Such losses are proof that ARS in situ preservation efforts are well
warranted," Pavek continues. "Setting up preserves for most major
wild relatives of crops could save these national treasures for future
Pavek hopes her experience with rock grapes as a pilot project will be used
to create other in situ preserves throughout the United States.
Investigating Wild Onions
Like rock grapes, native onion plants grow in rocky, wild places with thin,
"When we tried to grow out our native onion species to get more seeds,
they often didn't survive or produce many," says ARS curator Barbara C.
Hellier. She takes care of germplasm for the wild species of the genus
Allium, which includes onions, garlic, and leeks, at the ARS Western
Regional Plant Introduction Station in Pullman, Washington.
The reason for the poor growth, she says, is likely that the researchers
were trying to grow the plants in the rich soils of eastern Washington, rather
than on the rocky mountainsides where the plants normally thrive.
Wild Allium seeds often need very specific conditions to germinate that can't
be reproduced easily at germplasm repositories. This Douglas' onion thrives on
the Turnbull National Wildlife Refuge west of Spokane, Washington.
"Wild Allium seeds may need very specific conditions to
germinate that we can't reproduce easily at the lab," Hellier says.
"So we decided to see if we could maintain the collections in situ."
If it works, the scientists will be able to conserve many more native
Allium species. The station currently houses 87 of the world's 500
total--but only 6 of the more than 60 American natives. In the United States,
cultivated onion and garlic crops are worth more than $900 million annually.
As a pilot test, they're looking at three species of wild onion in
Washington: Douglas' onion (Allium columbianum) and Geyer's onion (A.
geyeri) at the Turnbull National Wildlife Refuge west of Spokane and
fringed onion (A. fibrillum) in the Umatilla National Forest outside of
Dayton. "The advantage to these locations is that they have a large
population of plants, and the areas are not likely to have a lot of
disturbance," Hellier says.
She's found two additional sites where each of the three species grows. To
ensure that sufficient genetic diversity is preserved, Hellier will take
samples of each species from all four sites and screen them for genetic
The in situ sites will serve as sources for seed that would be stored in
Pullman. At the same time, scientists will be monitoring the status of the wild
"If there's a threat to a certain population, we can recommend that
action be taken," she says.
Project Confirms Germplasm Protection Is Needed
In situ preservation can also help scientists evaluate the existing genebank
program for crops that have been cultivated and stored throughout history--like
Around A.D. 400, the Incas of Peru not only relied on the potato as a major
food source, they actually measured time by how long it took to cook one. Today
we have wristwatches and clocks to tell time, but the cultivated potato,
Solanum tuberosum, still holds a place of high esteem in our society. In
fact, the nutritious and versatile potato is eaten more than any other
vegetable in the United States and is the world's fourth most important food
crop after rice, wheat, and corn.
USDA's Economic Research Service estimates U.S. potato production at nearly
48 billion pounds a year, while over 620 billion pounds are grown worldwide
Project gardener Charles Fernandez demonstrates pollination techniques used to
propagate seed of wild potatoes maintained at the U.S. Potato Genebank in
Sturgeon Bay, Wisconsin.
"But in spite of its virtues, the potato needs improvement," says
John B. Bamberg, ARS potato geneticist and project leader for the U.S. Potato
Genebank in Sturgeon Bay, Wisconsin.
Potatoes are susceptible to a wide range of diseases and pests. Fortunately,
the potato has about 250 close relatives growing in the wild. These
"cousins" carry resistance genes that have helped them survive for
centuries. The Sturgeon Bay genebank holds nearly 5,000 samples of over 150
potato species in the national collection.
Where are these wild species?
Bamberg doesn't have to climb the Andes to find two important wild
species--Solanum jamesii and S. fendleri. Researchers are
preserving the genetic diversity of this pair of wild potatoes in two ways: ex
situ--in the artificial environment of genebanks; and in situ--where nature
placed them. Bamberg and others have found them growing on public lands in the
southwestern United States.
S. fendleri grows in the mountains of west Texas and in the southern
half of New Mexico and Arizona. S. jamesii has been found in the same
places and northward into Utah and Colorado, often near archeological
Although small tubers are typical of wild potato species, geneticist John
Bamberg says genes for desirable characteristics may also be present.
"Wild tubers found in the Southwest are similar to common potatoes,
except they're small--about the size of marbles," says Bamberg. "But
they represent a veritable treasure chest of genetic diversity for potentially
useful traits that may someday be bred into new varieties."
Bamberg began exploring these areas in 1992 to help address the concerns of
the Association of Potato Intergenebank Collaborators (APIC). Genebank managers
needed to scientifically evaluate their methods of preserving genebank
diversity. So Bamberg recollected both S. fendleri and S. jamesii
from the original geographic sites where earlier plants had been collected in
1958 and 1978 and stored in the genebank.
Alfonso del Rio, a University of Wisconsin graduate student working with
Bamberg, has used these two potatoes as models to determine the effectiveness
of conservation methods used in the genebank.
With random amplified polymorphic DNA (RAPD) analysis, del Rio compared the
genetic fingerprints of the seedlots of S. fendleri and S.
jamesii produced in the genebank with those of the parent populations from
which they originated. In each case, the comparison showed that propagation in
the genebank did not greatly change the genetic composition of populations.
"These results confirm that our ex situ methods of increasing seed in
genebanks are sufficiently thorough and that we are not losing much genetic
diversity," says Bamberg.
"An astonishing fact, however, is that the recent collections from the
wild were very different from the original samples collected from exactly the
same site decades earlier," Bamberg says. "That knowledge is an
important clue that these re-collections from in situ populations may be a
source of unique new germplasm for world genebanks.
"Thus, these wild populations should not be viewed as just duplicate
backups of populations preserved in genebanks," he says.
Data specialist Jesse Schartner (left) and
geneticist John Bamberg examine wild potato plants grown out from seed stored
at the U.S. Potato Genebank.
Why are populations at different sites genetically different, and how did
these wild populations become distributed in the current locations? Potatoes
moved north into the United States from Mexico. How genetic diversity could
have been influenced by geographic factors such as latitude, climate, and other
flora and fauna in the area is under investigation.
"Potato remains recently discovered in ruins now also provide the first
solid evidence that the wild potato species were used by ancient native people
in the region," says Bamberg. The Hopi and Navajo Indians ate potatoes
prepared in dishes made of a special clay to neutralize bitter alkaloids.
Similarly, the Pueblo and Zuni Indians are known to have eaten potatoes.
Germplasm like these wild potatoes is becoming more and more valuable. One
reason is that concerns about use of pesticides and fungicides to control plant
diseases and pests have made genetic solutions found in germplasm more
"The beauty of maintaining the natural populations of crop species in
their native habitat is that the evolutionary processes continue," says
ARS horticulturist Ned J. Garvey, who heads the Beltsville Plant Exchange
Office. "The plant populations continue to be challenged by insects,
diseases, animals, droughts, and fires--and they change genetically in response
to these challenges."
"Our goal in the in situ program is to make landowners like the
National Park Service aware that there are genetically important plant
populations on their land," says Garvey. "We ask landowners to not
take action that would jeopardize these populations, to allow us continued
access to them, and to alert us to possible threats."--By Hank Becker,
Linda Cooke McGraw,
Stelljes, Agricultural Research Service Information Staff.
Diane S. Pavek and
Ned J. Garvey are at the USDA-ARS
Resources Laboratory, 10300 Baltimore Ave., Beltsville, MD 20705-2350;
phone (301) 504-5692, fax (301) 504-6305.
Warren F. Lamboy is in the USDA-ARS
Resources Unit, Cornell University, Geneva, NY 14456-0462; phone (315)
787-2339, fax (315) 787-2397.
Barbara C. Hellier is at the
Regional Plant Introduction Station, 59 Johnson Hall, Washington State
University, Pullman, WA 99164-6402; phone (509) 335-3763, fax (509) 335-6654.
John B. Bamberg is at the USDA-ARS
Station, 4312 Hwy. 42, Sturgeon Bay, WI 54235; phone (920) 743-5406, fax
"Why In Situ?" was published in the
December 1998 issue of
Agricultural Research magazine.