September 20, 2005
Prof. Joe Cummins
Escape of the Transgenic Zucchini
Seminis seeds, a company owned by Monsanto Corporation recently admitted that genetically modified (GM) zucchini squash (courgettes) had been planted in Germany, The company claims to have destroyed the crop.
Presumably, the GM zucchini was modified with viral coat protein genes for virus resistance (virus resistance has been the only trait Seminis Seeds incorporated into GM squash, Cucurbita pepo). Interestingly, Seminis is along with USDA and Cornell University patentees of GM virus resistant Papaya that was recently “accidentally” extensively planted in Thailand polluting much of the crop. “Accidental” genetic pollution of an existing crop could be used as a justification for rapid approval of the release of the transgenic crop.
Squash (Cucurbita pepo) is among the four cultivated species of Cucurbita, C. pepo, C. maxima ,C. mixa and C. moschata. These species originated from gourds in Mexico and Central America (1). Cucurbita pepo was domesticated about 10,000 years ago making its domestication contemporary with maize and beans (2). Cucurbita pepo includes zucchini, crook neck squash and pumpkins within its species. C. pepo is monecious with male and female flowers on the same plant. The male flowers produce heavy stick pollen that requires insect pollination but insect pollination may transfer the pollen over a large distance(1). C. pepo was introduced into Europe soon after the discovery of the Americas.
Currently there are a number of landraces and feral forms of C, pepo in Europe(3) C. pepo subspecies pepo includes Zucchini, Pumkin, Vegetable Marrow and Cocozelle, C. pepo subspecies texana includes the crookneck, Acorn and Scallop squash (4). Most wild C. pepo are located in the Americas (1), while feral races are commonplace in Europe (2).
There have been 68 field test applications for GM squash in the United States , 67 of these have been for virus resistance. 17 field tests were undertaken on virus resistant GM squash in Mexico, 9 in Egypt,3 in Italy,2 in Spain and one in France (5).
The GM zucchini presently handled by Seminis was derived by crossing Zucchini with GM crook necked squash developed by Asgrow Company who received a permit for commercial release of the the squash in 1994 ( the second GM crop approved for commercial release). Asgrow was fused with Petoseeds to become Seminis in 1995. Subsequently, Seminis joined Monsanto Corporation. The GM zucchini was modified with coat protein genes from Zucchini Yellow Mosaic Virus and Watermelon Mosaic Virus 2.
The GM squash and Zucchini were not well supported by farmers in the United states because viruses such as cucumber mosaic virus were not protected against by the GM C. pepo (6).
There is good evidence that the virus resistance genes are readily spread to wild forms of C. pepo. Spencer and Snow (7) showed that GM yellow squash , derived by crossing with GM crookneck squash ( essentially the same kind of cross that produced GM Zucchini) readily pollinated wild C. pepo to produce virus resistant wild (weedy) squash.
A commercial C. pepo squash bearing coat protein genes for the two viruses in the original GM squash along with a coat protein gene for Cucumber Mosaic Virus was found to make hybrids with the wild squash C. pepo subspecies ovifera var texana . The hybrids grew more vigorously and produced more seed than the wild plants from which they were derived
(8,9).
It seems clear that GM virus resistant squash are a blessing to wild and weedy relatives of the GM squash. In the case of the illegal releases of GM Zucchini in Germany it was suggested that the GM plants were grown in a green house. As a rule, greenhouses ventilation systems readily allow movement of pollinating insects between the greenhouse and nearby fields. It is safest to presume that the viral transgenes have contributed to the production of better wild and weedy squash in the fields of Germany.
References
1. Quemada,H. and Tricoli,D. Petition for determination of regulatory status of Cucurbiata pepo L. cultivar YC77E ZW-20 Petitions of Nonregulated Status Granted or Pending by Aphis 1992 http://www.aphis.usda.gov/brs/not_reg.html
2. Smith,B. The initial domestication of Cucurbita pepo in the Americas 10,000 years ago Science 1997, 276, 932-4
3. Diez,M,Pico,B. and Nuez,F. Cucurbit genetic resources in Europe
Future Harvest 2002 http://www.ipgri.cgiar.org/publications/pdf/835.pdf
4. Paris,H. and Nelson,H. Seed dimensions in the subspecies and cultivar groups of Cucurbita pepo Genetic Resources and Crop Evolution 2003,50,615-25
5. Gaba,V,Zelcer,A. and Gal-On ,A. Cucurbit biotechnology-The importance of virus resistance In Vitro Cell Dev Biol-plant 204,40, 346-58
6. Public Issues Education Project Am I eating GE squash or zucchini? 2004 http://www.geo-pie.cornell.edu/crops/squash.html
7. Spencer,L. and Snow,J. Fecundity of transgenic wild crop hybrids o of
Cucurbita pepo: Implications for crop to wild gene flow. Heredity 2001
86,694-702
8. Fuchs M, Chirco EM, McFerson and Gonsalves D. Comparative fitness of a wild squash species and three generations of hybrids between wild x virus-resistant transgenic squash. Environ Biosafety Res. 2004 Jan-Mar;3(1):17-28
9. Fuchs M, Chirco EM and Gonsalves D. Movement of coat protein genes from a commercial virus-resistant transgenic squash into a wild relative. Environ Biosafety Res. 2004 Jan-Mar;3(1):5-16.
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