Traits introduced in foods by genetic engineering

A brief overview

Trait Percentage of all GE-food products:

Herbicide tolerance about 40%
Virus resistance about 15 %
Improved technical quality about 15 %
Increased disease resistance and male sterility a few cases
Improved nutritional value a few cases

In some cases two or more of the above traits have been combined in the same product .

The figures are based on an OECD investigation of field trials in 14 countries (ref. OECD Evaluation of Biosafety Information Gathered During Field Releases of GMOs, DSTI/STP/BS(92)6. \b\f16).

Recent reports indicate that the use of herbicide resistant products represents more than 50 percent of the GE crops today.


1. Herbicide tolerance

The idea is to make the plant resistant to some powerful herbicide that will efficiently wipe out all weeds. Unfortunately, however, there are no herbicides that will only kill the weeds. In stead they will kill or harm other plants and may also (in the case of for example Roundup) affect bushes and trees in the neighborhood , leaving only the resistant crop unaffected.

Because the weeds will develop resistance to herbicides, the herbicide-tolerant crops will become useless after some time.

The sprayed herbicicide will not stay within the borders of the field. Significant harmful effects on plants have been observed outside the fields. Normally, plants in the ditches and non-cultivated regions surrounding the fields are important habitats and food sources for different insects and other creatures including birds and bats that may be beneficial for agriculture (recently it has been found that Bats in Texas play an important role in greatly reducing a harmful pest). By killing all other plants than the crop, a profound ecological disturbance is created. Its long term consequences for agriculture are incompletely known.

A report on over 8000 university-based field studies has found lower yields and increased use of herbicide compared to conventionally bred soy (see Genetically Engineered Roundup Ready Soy crops less profitable than conventionally bred varietes  [EL].

Findings by the U.S. Department of Agriculture demonstrate that such crops do not produce a higher yield and fail to reduce the use of pesticides: American experts studied GM soya beans, maize and cotton being grown across huge tracts of the U.S. farming belt. They found no increase in yields from crops in 12 of 18 areas. Farmers in seven of 12 areas studied used the same amount of pesticide as those growing traditional crops.

The findings shoot down the favorite arguments of the Biotech industry that these crops could help stop hunger in the Third World through higher yields. They also disprove claims that the plants, engineered to include their own pesticide, would need to be sprayed less often with chemicals.


Herbicide tolerant plants are likely to be useful only temporarily. Recent scientific reports indicate that they will not provide higher yields. Nor have they reduced the use of herbicides. The use of herbicides is not ecologically unproblematic and there is a growing consensus among agricultural experts that other solutions need to be developed to achieve sustainable agriculture.

2. Pesticidal crops

About one third of the plant products are engineered for insect resistance. This means that a gene has been inserted that produces some substance that will kill the insects. Some products have been engineered both for herbicide and insect tolerance.

Many projects have been started in order to create plants with "built-in pesticides". The genes are taken from certain plants that have a natural ability to produce pesticides. Such plants with a 'natural' tolerance to insects, fungus and bacteria are well known since many years. Their pesticidal substances have been extensively investigated. Like man-made artficial pesticides many such substances have been found to cause cancer, birth defects, nerve damage or reduced immunity.

An example of the negative health effects of increased pesticide production in celery is described by Professor Joe Cummins (ref. Cummins. J. Plant-Pesticides.)

Careful long-term food safety assessment is required to rule out harmful effects. Still, present regulations do not require such testing.

A Cornell University study has found that 56% of Monarch Butterfly larvae died from eating pollen from plants having a pesticide gene (the Bacillus Thuringiensis (Bt) toxin gene). This opens the possibility that many other insects of vital importance for the ecology and for agriculture may be harmed likewise, for example bees as they feed their larvae with pollen.

It is obvious that very careful long-term interdisciplinary studies are required before it can be judged whether pesticidal crops are safe for the environment. No such studies have been done on any of the pesticidal crops now approved for release in several countries.

Finally, the pests are likely to develop resistance to the pesticidal plants. This has been observed to occur surprisingly rapidly in the case of Bt toxin which presently is the most common GE pesticidal agent. In this case it is especially regrettable as Bt toxin spray has for many years been a valuable pesticide in organic farming. When used as a spray there was little resistance problems because the toxin disintegrated rapidly when exposed to the sun. But its permanent presence in the plants has created a different situation.


The pesticidal plants are likely to be a temporary solution. With potentially harmful health and ecological effects. Release of such crops should not be allowed until their safety has been established through careful long-term studies.

3. Virus resistance

The benefit from increased virus resistance may become off-balanced by new viruses that might be generated in GE plants, as these may be more aggressive and less species-specific according to some scientific observations. (See Virus hazards). The knowledge about this risk is still incomplete.

Because of this possibility, plants with engineered virus genes should not be allowed until this issue has been carefully elucidated.


The insertion of virus resistance genes is potentially harmful to the ecology because of possible generation of new viruses. This complication has been incompletely investigated.

4. Improved quality

The idea is to improve for example shelf-length and other properties that might be of commercial interest.The quality "improvements" that have been achieved so far are small.


The quality improvements so far achieved are of marginal value.

5. Improved nutritional value

Aware of the fact that a major argument against GE crops so far has been that they don't provide any significant benefits, the industry has recently been trying to develop products that might be claimed to be valuable. The "flagship" of this new strategy is the "golden rice", a rice variety, developed by Rockefeller Foundation to produce A-vitamin, which is a common cause of blindness in developing countries. However, recently it has been demonstrated that this rice, which is already being established on the market, a/o in Indonesia, does not produce A-vitamin to a significant extent, see GM rice promoters 'have gone too far'.

However, most importantly, there are strong reasons to question the usefulness of such a product even if a strain could be developed that would generate significant amounts of the vitamin, see "Vitamin A enhanced GE crops: potential problems". The reason for vitamin A deficiency in developing countries is great poverty, forcing people eat very one-sided diet. Vitamin A is just one of several important nutrients that are deficient in their diet. This kind of approach is therefore not a real solution.

Overall Conclusion

None of the genetically engineered products cultured today are so valuable to mankind that it is reasonable to expose the environment or the consumers to even the slightest risk.

We want also to remind that the knowledge is very incomplete about DNA and the effects of genetic engineering on the organism as well as of the environmental and health effects of GE foods. It will take decades before science will be able to judge whether really useful (which also means safe) products can be developed with this method. Until then GE organisms should not be released and used commercially.

Related articles:

"Genetically Engineered Food - Safety Problems"
Published by PSRAST

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