Virus-resistant crops are becoming a mainstay in the biotechnology
industry. These crops incorporate foreign virus genes, which are
genetically engineered into the plants, for the purpose of producing
resistance to the virus.
For example, crookneck squash with engineered virus resistance has been
marketed in the United States--much of that product is marketed as baby
food. US Permits to grow virus resistant beets, cucumber, lettuce, melon,
pepper, potato, sunflower, tomato and watermelon have been granted or are
pending, even though laboratory experiments showed that they could
potentially give rise to new viruses-- deadlier than the viruses that the
crops are being protected from!
There are three kinds of hazards associated with the virus resistant crops,
which incorporate foreign virus genes: recombination, transcapsidation and
* Recombination is the scrambling of virus genes to create new gene
combinations, some of which can give rise to deadlier viruses. Laboratory
experiments showed that tobacco plants engineered with a virus gene created
new virus strains by recombination when infected with a virus. With
virus-resistant crops soon to be released on such a huge scale, there is a
very high probability that super viruses will be created by recombination.
* Transcapsidation happens when the virus "coat" from the plant cell is
taken up and used by an invading virus. The transcapsidated virus could
have an enhanced infection and extended range of hosts to infect.
* In synergism, the virus gene in the plant cell potentiates the effect of
the incoming virus. This may be manifest in more severe disease symptoms
or in the increased concentration of virus particles in the cells.
Recombination is the most threatening of the three effects because
recombination can produce a host of new virus diseases and create viruses
capable of destroying a whole crop or many crops.
In 1993 the Union of Concerned Scientists called for a moratorium on
commercialization of virus resistant crops until a stronger risk assessment
program was introduced by the government. The Union's proposal was
ignored by government regulators.
The virus resistant crops are not being monitored for the production of new
plant viruses. Any new virus problem from the use of transgenic crops
would be detected by farmers, seed producers, and scientists as new virus
disease. It is likely that such detection would take place too late to
deal with a strong disease producing virus.
For example, a super virus could begin with the introduction of a crop
such as potato bearing a "movement" gene to provide protection against
virus. Recombination with a previously immobile virus might yield a
superior, highly infectious virus that in one season could infect most seed
stock. By the following season, most potato production would have been
eliminated or greatly diminished in North America.
The marketing of virus resistant crops bearing copies of virus genes in
each cell has begun. The number of biotech foods in general in this
country is rising steadily, in spite of concerns of very serious
As consumers, we need to let our governments and local supermarket managers
know that we will not tolerate unlabeled genetically engineered foods. We
deserve the freedom to make an informed choice about what we put on our
kitchen tables every day. Visit with your supermarket manager soon.
Support organic growers across the country with your produce purchases.
And write your concerns to:
Hon Alan Rock, Minister of Health ((Fax 613-427-4276)
Hon Lyle Vanclief, Minister of Agriculture (Fax: 613-996-8652)
House of Commons, Ottawa, ON K1A 0A6 (no postage necessary)
Greene, A. and Allison, R. 1994 Science 263, 1423-5
Wuethrich, B. 1994 New Scientist 2April page15
Robinson, D. 1996 Transgenic Research 5, 359-62
Wintermantel, W. and Schoelz, J. 1996 Virology 223, 156-64
ISB/NBIAP News Reports Jan.1996, Aug.1996, April 1997