News | September '07 | Novel and everywhere
At least one American State has found cotton bollworms feeding in large numbers on GM cotton containing a 'Bt' toxin specifically designed to kill this pest. In several States a previously rare corn pest, 'western bean cutworm', is becoming increasingly established. Researchers suspect that the cause is the widespread planting of Bt crops which are now suppressing the pests' major predators.
A large number of strains of Bt maize have been found to produce high levels of amino acids (the building blocks of proteins) in their sap. This is thought to be promoting infestations by aphids which feed on the sap.
Attempts to overcome the above problems by stacking multiple genes in the plants are not living up to expectations. A very expensive commercially available maize with two Bt genes intended to prevent both cornborer which attacks leaves, and root worm which attacks underground, is still proving susceptible to storm damage due to infested, weakened roots.
A more sinister side-effect of Bt crops was revealed in a published study carried out by Canadian scientists. The researchers analysed aquatic environments (soil, sediment and surface water) around Bt maize fields during cob ripening, after harvesting and after mechanical root remixing. Bt genes were found to persist for more than 21 days in surface water and 40 days in sediment. Gene survival time, was not increased by the removal of bacteria. Levels of the transgene in the presence of bacteria were five-fold more abundant by the end of the study period. Transgenes were detected in the nearby river 82 kilometres downstream of the experimental plot.
OUR COMMENT
The Canadian study was described as 'sinister' because of its huge implications for environmental and human health.
Readily measurable artificial gene constructs persist in soil water for weeks on end and appear to be transported by the water column into rivers where they can be carried huge distances. In such aquatic environments, the DNA will always come into contact with bacteria which can absorb and use it. The evidence suggests that the artificial DNA does not become a source of bacterial nutrition as expected (i.e. there were no signs of it being 'eaten up' by the presence of bacteria). Worse, it also seems that the DNA constructs are being multiplied by the presence of bacteria (i.e. the transgenes are being absorbed by the microbes and kept intact for potential future use). The logical extrapolation of this is that our environment is filling up with bacteria which have acquired artificial DNA from their surroundings and can use it to generate artificial insect-damaging toxins.
Because the man-made versions of the Bt genes contain extensive human alterations, they don't represent simply a few new sources of a bacterial toxins which are kicking around in the soil anyway. There may, not only be more of them, but their toxicity to animal life might be hugely enhanced. The addition of viral promoters to these novel Bt genes may well cause its own havoc of horizontal toxin-gene transfer and over-expression of the gene and the stimulation of other toxin-producing bacterial genes. And, besides Bt toxin genes, there are now transgenes out there in the field (and soil and rivers) for a whole host of pharmaceutical products.
- Biotech crops are generating novel chemicals
- Biotech crops are generating novel pests
- Biotech crops are generating novel genes
- ... and soon they'll be everywhere.
If you're not thoroughly worried yet, have a look at TRY YOGA – News, September 2007.
SOURCES
- Douville et al. Ecotoxicology and Environmental Safety 66:2, February 2007 pp196-203
- Farmers' Weekly 17.01.07
- The News-Gazette, 13.07.07
- Scientists Live, July 2007.