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Initially, scientists thought genes were unlikely to flow from transgenic
crops to weeds, because known crop-weed hybrids are often sterile. But last
September, Bergelson and two Chicago colleagues startled researchers with a
study of Arabidopsis thaliana, a mustard species often used as a test organism
by plant geneticists. Usually, the plant pollinates itself, implying to
scientists that foreign genes in transgenic A. thaliana would not escape by
hybridization. But after the researchers planted ordinary A. thaliana,
transgenic herbicide-resistant A. thaliana, and a naturally occurring,
herbicide-resistant mutant variety, they learned that the transgenic plants
were 20 times more likely to outcross than the mutantsthey were “promiscuous,”
as a headline in the journal Nature put it. “Nobody knows why,” Bergelson
says.
“We’re still trying to find the mechanism that drives the pattern we saw.
There’s a lot we don’t understand, including how common it is.”

The implications are ominous. A decade ago, for instance, European sugar beets
spontaneously mixed with a wild relative, creating a hybrid species that is
now a continent-wide problem. Whereas the sugar beet is biannualthe root is
harvested at the end of the second year the new weed is an annual. At the end
of the year, Ellstrand says, “the root turns into a chunk of wood that damages
farm equipment or gets into the sugar-beet processing plant and screws up the
machinery. You can’t kill it with an herbicide because any herbicide that gets
the weed hits its relative. It’s not until the thing blooms and flowers that
you see it, and by that time it has set seed that gets into the beet field
forever.”

Transgenic crops have already shown the potential to create similar problems.
The prospect of herbicide- or insect-resistant superweeds is particularly
dismaying. In 1995, Monsanto and AgrEvo introduced herbicide-tolerant oilseed
rape (Brassica napus), the plant that is the source of canola oil. One year
later, an 11-member team from the Scottish Crop Research Institute
reported, to scientists’ surprise, that pollen from oilseed rape fields can travel as much as two kilometers. At almost the same time, three Danish geneticists
discovered that transgenic Brassica napus readily breeds with a weedy relative, Brassica campestris. The resulting plants look much like B. campestrisbut are
unaffected by herbicides. Taken together, says Dean Chamberlain of the University of North Carolina at Greensboro, the two reports “showed that hybridization is a real concern and that you need a very large buffer area around your plot to control it.”

When Ellstrand reviewed the literature on the 30 most agriculturally important
plant species, most scientists he consulted believed few hybridize easily. In
fact, he found evidence that more than 25 of the crops can break the species
barrier, sometimes with unrelated species. Included in that list is wheat,
which Robert S. Zemetra and his colleagues at the University of Idaho reported
in April can outcross with bearded goatgrass, a problem weed in the western
United States.

“What really shocks me as a biologist is that you have two species with
different numbers of chromosomes hybridizing,” says Allison Snow, a
botanist at Ohio State. “Goatgrass has 28 chromosomes and wheat has 42, but they can cross.” Biologists have regarded viable offspring from such mismatches as almost impossible. As a result, they thought the range of species that could
hybridize was limited. The goatgrass-wheat hybridization suggests that the
range is bigger than had been thought.

“You get very low rates of reproduction,” Snow says. “But when you’re talking
about acres and acres of wheat with goatgrass all around them, even a very low
probability event can occur.” If hybridization created insect-resistant
goatgrass in areas where the weed’s spread is naturally controlled by insects,
she says, “that could end up being the only kind of goatgrass you have, and
then you might end up with even larger infestations of it than we already
have.” Such fears are one reason that insect-resistant Bt cropswhich contain
genes from the bacterium Bacillus thuringiensishave been targeted by
activists.

In the United States, transgenic corn is unlikely to pose much risk of
hybridization because it has no close relatives. But Mexico has teocinte, the
wild plant that may be the ancestor of modern corn. What would happen if
Mexican farmers planted bioengineered corn? Could the new genes affect the
fitness of teocinte, which some agricultural ecologists view as a potential
storehouse of valuable genes for future corn breeders? “With the
information we have now,” Snow says, “it’s hard to tell when the long-term risks are serious enough to ban certain crops.”

Looming behind the ecologists’ fears is the belief that molecular biologists
who work with DNA on the laboratory bench don’t understand fully how it
behaves in the field. According to Rosemary S. Hails of the British National
Environmental Research Council’s Institute of Virology and Environmental
Microbiology, “The risk assessment of transgenic organisms is a
multidisciplinary subject, which should include ecologists, molecular
biologists, agronomists and sociologists.” Instead, companies tend to delegate
decisions about the release of transgenic crops to molecular biologistswho are
not trained to appreciate the full complexity of how the genetic code
interacts with environmental factors.

“How fast would a new weed get around?” Snow asks. “Nobody really knows. I’m sort of assuming that most of these crops will be approved eventually and
people like me will study what the consequences are. Then, after the cat is
out of the bag, we may figure out how to regulate this technology.”

A Hungry World

Given these risks, why do so many of these scientists support the continued
development of agricultural biotechnology? One answer is witchweed. Witchweed, the common name for three species in the genus Striga, is a parasitic plant that feeds on the roots of cereals and legumes in much of Africa. Attacking
maize, sorghum and milletthe continent’s three most important cereal
cropsStriga, in the view of Gebisa Ejeta, an agronomist at Purdue University,
is a “scourge” of African agriculture. It has been estimated that the weed
destroys 40 percent of the continent’s total cereals harvesta staggering loss
in the world’s hungriest places.

From a biological perspective, Striga is fascinating. Its seeds, smaller than
grains of sand, lie dormant for as long as 20 years, waking only when aroused
by a chemical emitted by the roots of the host plant. While still underground,
the parasite plants develop root-like organs called haustoriums, which
penetrate the host roots and siphon nutrients. Scores or hundreds of Striga
plants can attack the same host. Witchweed eventually grows into fields of
five-foot-tall plants with pretty pink flowers, but by that time it has long
destroyed the crops it feeds on. Because each plant produces as much as
100,000 seeds, witchweed is almost impossible to eradicatethe United States spent four decades wiping out a single small outbreak in the Carolinas.

Because witchweed rapidly adapts to new hosts, losses in Africa keep growing.
When the parasite made it impossible to grow sorghum in eastern Sudan,
desperate farmers tried to grow pearl millet. At first millet was immune. But
within a few years witchweed was wreaking havoc on the new crop, too. “People are literally starving because of Striga,” says Ejeta.

Ejeta and several other Purdue scientists have spent years trying to breed
varieties of sorghum that produce low levels of the chemicals needed to
germinate Striga. But parasite-infested cropland has such dense concentrations
of fallow seeds that even the improved varieties can be “overwhelmed,”
according to Fred Kanampiu, an agricultural researcher in Kenya for the
International Maize and Wheat Improvement Center, a Mexico-based laboratory that is usually known by its Spanish acronym of CIMMYT. “The solution is obvious,” Kanampiu says. “Herbicides kill witchweed. But unless we can engineer herbicide-resistant sorghum, the herbicides also kill the crop.”

Another “obvious” example of the need for biotech in poor countries is
broomrape, according to Jonathan Gressel of the Weizmann Institute’s
Department of Plant Genetics in Israel. The common name for several parasitic species in the genus Orobanche, broomrapethe name, Gressel says, comes from its effects on a legume called broomplagues vegetables, sunflowers and grain legumes throughout the Middle East. Like its cousin Striga, Orobanche produces tens of thousands of tiny seeds that lie dormant, ruining all attempts at planting the land. “The seeds are the size of talcum powder, maybe 50 cells per seed,”
Gressel says. “How they can live for 20 years is beyond me.” Methyl bromide,
the only available treatment, is expensive, not terribly effective and toxic.
“The activists want to ban biotech and herbicides and have farmers pull out
the weeds by hand,” he says.

According to economists, witchweed and broomrape epitomize the most important potential targets of agricultural biotechnology: the problems of farmers in developing nations. “At first blush you look at this technology and you say
this is the last thing that’s appropriate for poor farmers,” says James of the
International Service for the Acquisition of Agribiotech Applications. “It’s
proprietary, so farmers have to buy seed they now get for free, it’s developed
by industrial countries, so money flows from the poor to the richit must
all be ill-suited for developing countries. But when you look at it carefully, the
specs of the technology allow you to fit almost exactly what the small farmer
needs.”

The original Green Revolution crops depended heavily on irrigation, artificial
fertilizer and chemical pesticides. By contrast, James says, the fruits of
bioengineering are encapsulated in “the simplest technology of allthe seed.”
Pest-resistant seed corn, for example, needs no costly spraying equipment, is
not very complicated to grow, and releases little toxin into the environment.
Because poor countries often owe their poverty to bad soils or lack of
agricultural water, James believes they will disproportionately benefit from
bioengineered crops that can grow in barren land or stand up to drought.

“People in developed countries spend a relatively small part of their budgets
on food,” says Evenson, the Yale economist. As a result, he argues,
productivity increases from transgenic crops will not mean much to Europe or
the United States. “We can afford to throw away the technologyit’s a luxury
for people who already have enough to eat.” The situation is different for the
destitute. “In some places,” Evenson says, “you can get food being more
than 75 percent of people’s budgets. In rice-based areas, you’d have half of that
being on rice. So if rice prices are 20 percent higher than they would otherwise be, it’s not a small thing.” Last October, he presented a model that, among other
things, projected an increase in global malnutrition from stopping
biotechnology for 10 years. The exact tally of the starving, he says, “depends
on the assumptions, but they are never something to ignore.”

“What really bothers me is the increasing opposition, especially in Europe, to
using biotechnology for agriculture,” says Per Pinstrup-Anderson,
director-general of the International Food Policy Research Institute. Although
some activists believe that the potential side effects make transgenic
research unethical, Pinstrup-Anderson argues that the ethical considerations cut both ways. “It’s probably more unethical to withhold solutions to food problems
that cause children to die,” he says. “I don’t want to be melodramatic but there
are several hundred million hungry people in this world.”

“Biotech will be a contributor in the future to increasing yields enough to
make the world’s food supply keep up with population growth,” says Stephen
Padgett, a chief agricultural researcher at Monsanto. “It won’t do the job
alone, but it’s a crucial part of the effort.” Even in the best of
circumstances, though, making Padgett’s predictions come true will not be
easy.

India, for example, initially embraced the new techniques. With the active
support of the state, half a dozen Western firms set up collaborative research
projects with Indian institutions. In the most well-known of these efforts,
Mahyco, the nation’s biggest seed company, joined forces with Monsanto to
develop insect-resistant cottonIndia is one of the world’s leading cotton
producers. High-intensity cotton farming is notoriously risky to the
environment; in India, according to C.S. Prakash of the Tuskegee Institute’s
Center for Plant Biotechnology, the crop covers just 5 percent of the
agricultural land but accounts for 50 percent of the country’s insecticide
use.

Yet the initial tests in India of cotton bioengineered to resist bollworm
caused violent controversy. As a rule, farmers license, rather than own, the
seeds for transgenic crops. For this reason, they are not allowed to save the
seed from one year’s harvest to plant in their fields the next year. Critics
both inside and outside India argue that this removes one of the
foundations of rural agriculture, forcing smallholders into colonial dependence on rapacious multinationals. The companies respond that the increased yield and decreased costs from biotech will more than make up for the price of the seed each year.

In some instances, however, the big companies think the benefits don’t
outweigh the costs. In the early 1990s, Pioneer Hi-Bredthen the world’s biggest seed company, now a subsidiary of DuPontdeveloped exactly the kind of transgenic, herbicide-resistant sorghum that could fight off attacks of Striga. Then
Arriola, the Elmhurst geneticist, demonstrated in 1996 that sorghum easily
hybridizes with Johnson grass, a weedy relative that has become an ecological
pest in the United States since its accidental introduction from Africa in the
mid-1800s. The hybrids, fertile and vigorous, looked very much like Johnson
grass.

Because herbicides are almost the only successful means of eradicating Johnson
grass, an herbicide-resistant strain would have a major selective advantage.
“It would spread,” Arriola says flatly. “It could create huge losses.” The
findings, he says, surprised the molecular biologists; fearful of inflicting
ecological damage in North America, Pioneer soon stopped working on transgenic sorghumpostponing the day, perhaps, when Africa can feed itself.

“We’re talking about long-term ecological problems,” Arriola says. “But how do
you look somebody in the eye and say we are not going to develop this crop and
feed these people today because we might create some long-term problems in the future? Maybe transgenic sorghum is so risky that everyone knows it just isn’t worth it. But how do we make that decision in other cases?”

Who’s Watching the Greenhouse?

The uncertainty is due, in part, to the lack of a rigorous regulatory
framework to sort out the risks inherent in agricultural biotech. The plastic cages
covering the heads of the sunflowers help keep the transgenic pollen out of
the environment, a general requirement for obtaining a federal permit to grow a
test crop of bioengineered plants. But other than monitoring the plots, the
government imposes few conditions on biotech tests. The main reason is that
Congress has not passed any specific environmental law for genetically
engineered agriculture. Instead, transgenic crops are evaluated by three
overlapping federal agencies: the Food and Drug Administration, the
Environmental Protection Agency, and the Department of Agriculture.

Each government agency has a different statutory responsibility, which
sometimes leads to anomaliesand gaps in regulations. The FDA, for example,
doesn’t look at the safety of foods that have been engineered to express
pesticides, because pesticides are by law exempt from the agency’s purview.
Nor does the EPA, which is required to treat such foods as pesticides. Because
pesticides, of course, are toxic substances, the agency only establishes human
“tolerances” for each compound. (Responding to critics’ concerns, the agency
announced this spring that it may rethink its approach.) For its part, the
USDA simply tries to make sure that the crop grows in the way that the manufacturer says it will. The disjointed legal mandates, observes EPA biotechnology adviser Elizabeth Milewski, “make life interesting.”

One worrying consequence of this patchwork of regulations is that no one has
direct responsibility for looking at long-term effects on the environment. “We
have a first-approximation understanding of the population biology of these
plants and the insects, microbes and virus populations,” says Neal Stewart, a
biologist at the University of North Carolina at Greensboro. “But we know very
little about the community ecology and virtually nothing about the ecosystem
ecology of what these genes will do. And we are not pursuing this knowledge
actively.” Stewart’s concerns bore fruit in May, when Cornell scientists
reported that pollen from Bt corn can kill the caterpillars of monarch
butterflies.

According to Sally McCammon, science adviser to the USDA Animal and Plant
Health Inspection Service, biotech field trials can be of any size and last
for any length of time, though one or two years is the standard. From the
companies’ point of view, the tests are efforts to learn whether new crop
varieties will perform as intended. The government’s main job, McCammon says, “is to certify that the test is biologically contained.” Transgenic plants
must be kept apart from plants they might cross-pollinate. “Afterwards you have to account for it,” McCammon says. “We make sure that you bag what you take out and that the plant material is plowed under.”

These measures are necessary, to Snow’s way of thinking. But by ensuring that
transgenic genes won’t escape into the environment, they also make it
impossible to learn what will happen if they do. “The ecological questions
don’t even get touched,” she says. “In fact, it’s illegal to touch them.” She
believes that the environment and industry would be better served by
introducing a second level of testing devoted to ecological questions. Another
step, in her view, would be to fund academic research into the ecological
hazardscurrently the sole source of federal funds, the biotechnology-risks
panel of the USDA, has a budget of less than $2 million.

Technical controls may also be possible, says Gressel of the Weizmann
Institute. Most transgenic crops today have a single foreign gene. But
companies are already working on inserting several genes simultaneously into
the plant’s genome. In a May article in the journal Trends in Biotechnology,
Gressel argues that if these multiple genes were inserted in close
proximity to each other on the chromosome, potential hybrids would inherit all of them at once. And if the secondary genes coded for traits such as preventing dormancy, the hybrids would be less, not more, dangerous than their wild parents. For crops, the inability to lie dormant doesn’t matter, because the seed is harvested and replanted each year. But a weed that is unable to produce seed
that can remain dormant until an opportune time to germinate is at a
significant disadvantage. “The hybrid weed will be weaker, not stronger,”
Gressel says.

“I’m more worried about the future than the present,” Ellstrand says. “So far
it’s okaywe don’t have killer tomatoes flying through the air. But we need to
be thoughtful and careful about what we’re doing, and there are some people
and some portions of the industry where they have a better tradition of that than
others. People who have worked with plants outside in real life seem to have a
better handle on it than people who have worked with chemicals all their life.
If we keep paying attention to what’s happening in the field, we might be able
to make this technology realize its promise.”

Charles Mann is a contributing editor at The Atlantic Monthly and Science. He
wrote about the free software movement in the January/February issue.

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