The Danger of Virus-Resistant Crops,

by Joe Cummins, PhD,

Professor Emeritus of Genetics,

University of Western


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!

Threefold Hazard

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.

Professional Concern

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 risks.

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