Transgenic rape behaves just as well as wild-type rape. That'sthe bottom line of a three-year, multiplot field test in Britain ofa recombinant oilseed-bearing rape plant geneticallyengineered to tolerate a major herbicide.
Results of the carefully controlled trial showed that thetransformed plants are no more invasive than conventionalrape crops, and that gene-altered seeds, if anything, surviveless well in nature.
But these findings, while encouraging for agriculturalbiotechnology, will not appease environmentalists who worrythat plants rendered genetically resistant to weed-killers mayspread the implanted trait to natural vegetation.
Research ecologist Peter Kaveira of the University ofWashington, Seattle, suggested that this concern overtransgenic "invasiveness" results from miscommunication. "Anagronomist," he told BioWorld, "would use the word'weediness,' worried only that the crop might become a weed inan agricultural setting. An environmentalist," Kaveiracontinued, "is worried about a plant escaping and enteringnatural habitats, and disrupting native communities ofvegetation."
He points out that the U.S. National Park Service considers itsnumber one environmental problem to be runaway exotic plantspecies, which are a major bioextinction threat. He cited suchrogue, overgrowing flora as Scotch broom, water hyacinth andkudzu, adding, "the environmentalists set up an analogybetween 'exotic' and 'genetically engineered' organisms," toinveigh against transformed crop cultivars.
Kaveira wrote the lead editorial in today's issue of Nature,acclaiming the report of the British field trial in the same issuethat reports "an ecological study which will bring one of thehottest debates about the use of genetically engineered plantsin agriculture into the realm of rational discourse."
That report is titled "Ecology of transgenic oilseed rape innatural habitats." Its lead author is biologist Michael Crawley ofImperial College in Ascot, England.
During the 1990, '91 and '92 growing seasons, Crawley and hiscolleagues planted three genotypes of oilseed rape (Brassicanapus subsp, oleifera) and compared their behavior. Onecarried genes for tolerance to gluphosinate, a herbicidedeveloped by Hoechst AG and marketed in Europe as 'Basta.' Asecond had been transformed with a marker gene forresistance to kanamycin antibiotic (of no agronomicconsequence). The third was untransformed commercial rape.
Instead of setting these out in plowed fields as prototype crops,the researchers sowed them in 12 plots at three widelyseparated, climatically different locations of natural vegetation,loaned by Britain's Forestry Commission. Plant Genetic Systemsof Ghent, Belgium, provided the transgenic seeds.
Several of the 25-by-25-meter plots were subdivided tosimulate varied natural conditions. Some were cultivated toreduce interspecies competition; others were fenced to keepout rabbits and larger herbivores, or chemically treated toexclude repel snails.
As required by regulations, the experimenters had to advertisetheir plans in the local press. At a public meeting in Cornwall,recalled co-author Rosemary Hails, an ecologist at the OxfordInstitute of Virology and Environmental Microbiology, "therewas hostility, but mainly they wanted further explanations.There was definitely a point in the meeting when the moodchanged, and the people felt they understood."
Internationally, herbicides and oilseed rape are both bigbusiness. Some 600 million pounds of weed killer are appliedto crops annually. Brassica napus alone accounts for 4 to 5million tons of oil sold each year. Some projections indicate thatby the mid-1990s, annual sales of herbicide-tolerant seedcould reach $75 million to $320 million.
Such numbers help explain why 10 European chemical andagricultural companies joined forces with three Britishgovernment bodies -- the Ministry of Agriculture Fisheries andFood License, the Department of Trade and Industry, and theAgriculture and Food Research Council -- to set up a consortiumto conduct the transgenic rape field trials. Its industrialmembers included Advanced Technologies Ltd., AgriculturalGenetics Co. Ltd., Ciba-Geigy plc, Du Pont (U.K.) Ltd., Hoechst AG,ICI plc, Monsanto Europe, Plant Genetic Systems, Shell ResearchLtd. and Unilever (U.K.) Ltd.
The principal biotechnology adviser to this group, Roy Dietz ofthe trade and industry ministry, told BioWorld that half of theconsortium's budget of 1.5 million was funded by thegovernment and half by its industry members.
Hoechst, which makes and markets 'Basta' on the Continent,and 'Challenge' in the United Kingdom, is testing itsgluphosinate herbicide in the U.S. Hoechst-Celanesespokeswoman Andrea Stine told BioWorld that the companydoes not expect EPA approval for the next several years. Whenthis does come through, Hoechst will market it in the U.S. underthe name 'Ignite.'
Kenneth Baker, director of biotechnology policy for Monsanto-Europe, told BioWorld: "I think the Crawley project was done asa scientific study to answer technical questions as to what theissue was. It was designed to answer the genuine scientificquestion as to what the plant's behavior would be. The fact thatthe government was involved is that they need to know if theissue is real, and how to respond. It was set up with that inmind."
The authors of the test concluded in their Nature paper that"there is no indication that genetic engineering for kanamycinor herbicide tolerance increased invasive potential of oilseedrape. In those cases in which there were significant differences(such as seed survival on burial), transgenic lines were lessinvasive and less persistent than their conventionalcounterparts."
But they prudently hedged this acquittal with caveats. As Hailsput it to BioWorld: "The thing we really want to emphasize isthe danger in extrapolating too far from our results. We havelooked at one specific construct in one specific plant, and inparticular the construct we've looked at -- resistance toherbicides -- is not one that you'd necessarily predict wouldgive the plant an ecological advantage. Genes which conferinsecticidal properties to the plant, or drought tolerance orsomething@the answers may well be different." Those answerswere also sought during the three-year tests, and are nowbeing written up for publication, Hails added.
Kaveira concurred. "Crawley's study doesn't lay thisinvasiveness question to rest, but it says, 'Instead of arguingabout it, you can experimentally assess it.' "
The Seattle scientist, who sees most deregulation applications,foresees that "the Crawley report will have repercussionswithin the U.S. Environmental Protection Agency andDepartment of Agriculture.
"I think so," Kaveira explained, "because there are a lot of cropsin the process of just about being proposed for deregulation.This gives an indication of how one can substantiate 'no greaterrisk,' so I think it will have a major effect on deregulationapplications before USDA, especially now that it's launched itsnew 'biotechnology risk assessment' program. "
-- David N. Leff Science Editor
(c) 1997 American Health Consultants. All rights reserved.