Fate of food DNA

Evaluation of the safety of genetically modified (GM) crops seems to be hampered by the unwillingness of regulators recognize and to evaluate the impact of genetic effects that are outside simplistic models of genes and their behavior. It has been presumed that the organism destroys food genes during digestion and excretion. However, studies on DNA immunization showed that DNA could be delivered to the immune system through oral uptake. A few daring German researchers have also explored the fate of orally ingested genetic material. The papers below show that ingested DNA is not only circulated through the animal body but may be associated with nucleus and chromosomes.

The first paper "The fate of forage DNA in farm animals" by Einspanier et al (2001), studies ingestion of maize DNA and of GM maize DNA, while the second is an earlier study "On the fate of foreign DNA in mice" by Shubbert et al (1998) that showed that ingested DNA from a bacterial virus or from a plasmid transgene is incorporated in chromosomes and is passed from mother to fetus. The authors of the study ask "is maternally ingested foreign DNA a potential mutagen for developing fetus?" If food DNA sequences are randomly incorporated into coding sequences including introns, exons or promoters they will certainly act as mutagens.

These two studies show that food DNA is circulated to the tissues of animals and may even be transmitted from the mother to the fetal tissues. Studies of the type described above should be repeated and extended. Mainly, however, the studies should stand out as a clear warning to regulators that they cannot ignore a major paradigm shift in the way that DNA and genes evaluated.

In one of the two studies transgenic DNA from a plasmid is clearly circulated to tissues while in the other transgenic DNA was not detected in tissues. However, the latter study involved a lower relative input of the transgene and should be repeated with higher resolution of the transgene and using high relative input of the transgene say by feeding concentrated Bt plasmid. Experiments of that type can be undertaken using human volunteers as well as farm and experimental animals.

The available evidence is sufficient to support a moratorium on the massive intake of GM crops by human populations until the genetic consequences are resolved in the laboratory. It is not sane to suggest that the huge populations fed unlabeled GM crops are a sufficient test of the safety of the genetic constructions. No method is available to readily quantify the intake and exposure of humans to unlabeled GM foods.

The impact of bacterial DNA on the immune system (the CpG effect)

Essentially all of the GM crops marketed or being field tested presently contain bacterial sequences as a part of the plasmids used for delivering genes and many of the primary crop protection genes are of bacterial origin. Such genes include Bt and most herbicide tolerance genes.

DNA vaccines have generated a huge literature and clinical applications showing the activity and cellular incorporation of DNA administered by oral, inhalation, injection, vaginal or dermal application (Molling 1997,Donnoley et al 1997 and Gurunathan et al 2000). Ingestion of bacteria does not appear to be an effective means of delivering DNA because the bacterial cell walls effectively contain the nucleic acid (for example, in yogurt the milk products are digested but the bacteria of the culture are passed intact). Lysis genes have been found necessary and effective in triggering release of DNA for mucosal vaccine delivery (Jani and Mekalanos 200). In contrast , the crops eaten by animals release oligonucleotides and DNA peptide complexes during digestion and such molecules circulate to a significant degree.

The bacterial genes used in constructing GM crops have a property that impacts on the immune system over and above the ability to produce antibodies. Eukaryote DNA has relatively low frequencies of the dinuleotide motif CpG and that motif is methylated and plays a role in gene regulation while bacteria and their viruses have a high frequency of the CpG motif that is usually unmethylated. Apparently the CpG motif in DNA molecules and oligonucleotides provides a signal that the immune system recognizes and initiates a primary sequence of reactions leading to activation of the immune system leading to inflammation (Manders and Thomas 2000 and Gurunathan et al 2000). Gung et al (1999) found that bacterial DNA CpG caused septic arthritis. Hemmi et al (2000) found that there is a receptor protein that recognizes bacterial DNA. Oligonucleotides rich in the CpG motif are used to enhance immunization. Inflammation is an essential part of the immune response but it adversely affects existing conditions such as autoimmune disease. Furthermore, it has been found that CpG oligonucleotides rescue B cell lymphoma cells from anti-IgM mediated growth inhibition (Han et al 1999). The oligonucleotide acts as a promoter of lymphoma.

Finally, Gorecki and Simons (1999) pointed out a danger to the fetus in DNA vaccination of the mother. That danger was the creation of tolerance in the fetus leading to individuals more susceptible to infection and/or they may become carriers. The introduction of genes with bacterial CpG motif to the fetus is likely to have untoward consequences.

In conclusion, the bacterial genes used in GM crops have been found to have significant impacts on the individuals ingesting GM crops. The impacts include inflammation, arthritis and lymphoma promotion. The consequence of GM food genes being incorporated into the chromosomes of somatic cells of those consuming GM food and their unborn has been ignored by those charged with evaluating the hazards of GM crops.

References

1. Deng G, Nilsson A, Verdrengh M, Collins L, Tarkowski A "intra-articularly located bacteria containing CpG motifs induces arthritis" 1999 Nature Medicine 5,702-6

2. Donnelly J,Ulmer U,Shiver J and Lui M. "DNA Vaccines"1997 Annu Rev Immunol 15,617-48

3. Einspanier R, Klotz A, Kraft J et al (2001). European Food Research and Technology Abstract Volume 212 Issue 2 (2001) pp 129-134 The fate of forage plant DNA in farm animals: a collaborative case-study investigating cattle and chicken fed recombinant plant material

4. Gorecki D and Simons J "The dangers of DNA vaccination" 1999 Nature Medicine 5,126

5. Guunathan S, Klinman D and Seder R. "DNA Vaccines" 2000 Annu Rev. Immunol 18,927-74

6. Hemmi H,Takeuchi O, Kawai T, Kaisho T, Sato S, Sanjo H, Matsumoto M, Hoshino K, Wagner H, Takeda K, Akira, S "A Toll-like receptor recognizes bacterial DNA"2000 Nature 408, 740 - 745

7. Hsu S, Chung S, Robertson D, Ralph L, Chelvarajan R, Bondada S (1999) "CpG oligodeoxynucleotides rescue BKS-2 immature B cell lymphoma from anti-Ig-M-mediated growth inhibition by up-regulating of egr-1" International Immunology 6,871-9

8. Jain V and Mekalanos J "Use of lambda phage S and R gene products in an inducible lysis system from Vibrio cholerae and Salmonella enterica servovar Typhimurium-Based vaccine delivery systems" (2000) Infection and Immunity 68,986-9

9. Manders P and Thomas R "Immunology of DNA vaccines: CpG motifs and antigen presentation" Inflamm Res 49,199-205

10. Molling K "Naked DNA for vaccine or therapy" (1997) JMolMed 75,242-6

11. Schubbert R, Hohlweg U, Renz D and Doerfler W (1998). "On the fate of orally ingested foreign DNA in mice: chromosomal association and placental transmission to the fetus" (1998) Mol Gen Genet 259: 569-576

12. Schubbert R,Renz D, Schmitz B and Doerfler W, "Foreign (M13) DNA ingested by mice reaches peripheral leucocytes, spleen,and liver via the intestinal wall mucosa and can be covalently linked to mouse DNA" (1997) Proc. Natnl Acad Sci USA 94,961-6

GM DNA in Human Gut Underestimated

By Dr. Mae-Wan Ho
ISIS Report
21 July 2002

That GM DNA should transfer to bacteria in the human gut is not at all unexpected. We already know that DNA persists in the gut, and that bacteria can readily take up foreign DNA. Why did our regulators wait so long to do the experiment? And an experiment that's designed against making positive findings?

The research in question is the final part of the Food Standards Agency (FSA) project on evaluating the risks of GMOs in human foods, commissioned by the former Ministry of Agriculture, Fisheries and Food (MAFF).

A single meal containing GM soya was fed to human subjects. It consisted of commercial soya meal - 150g El Corte Ingles, batch number and GM content unspecified - mixed in the burgers and soya protein supplement – 100g Holland and Barrett, batch number and GM content again unspecified -mixed in 'milk' shakes. No data were presented on how much DNA was present in the commercial samples, and whether the DNA was broken down and to what degree. Needless to say, the GM DNA inserts were not characterised at all.

The method of detecting GM DNA is highly flawed. It depends on amplifying a small part – 180bp - of the entire GM DNA insert that was at least ten or twenty times as long. So, any other fragment of the insert would not be detected, nor would a fragment that did not overlap the whole 180bp amplified, or that had been rearranged. The chance of getting a positive result is 5% at best, and likely to be much, much less. Thus, a negative finding with this detection method most probably does not indicate the absence of GM DNA.

More revealing still, the researchers checked for GM DNA only in the gut contents, but failed to check if the DNA has passed through the gut into the blood stream and blood cells. This omission is inexcusable, as a series of experiments in mice dating back to 1997 had already documented that GM DNA can pass through the gut wall into the bloodstream, to be taken up by cells in the blood, liver and spleen. When fed to pregnant mice, the GM DNA also passed through the placenta to be taken up by the cells of the foetus and the newborn.

In the first trial, the GM meal was fed to seven subjects that had part of their lower bowel removed from a previous operation and wearing a colostomy bag. The digested food from the colostomy bag was analysed, and GM DNA was detected in all seven subjects. As much as 3.7% of the GM DNA was recovered in one subject. Bearing in mind the limitation of the method used for detecting GM DNA, all the values are probably gross underestimates.

In the second trial, the meal was fed to 12 human volunteers with intact bowels. No GM DNA was detected in the faeces, which the researchers claimed, indicated that the nucleic acid did not survive passage through the complete intestine. But this claim is most likely to be false, due to the limitation of the GM DNA detection method.

Microbes in the digested food that had passed through the small intestine were cultured through 6 passages in broth containing glyphosate. Bacteria grew to a density of 108/ml in each sub-culturing. In each sub-culture derived from samples taken from 3 subjects at 180, 240 and 300 min after eating, the transgene was found. This is yet another gross underestimate. The method depends on the bacteria having taken up an intact gene coding for glyphosate tolerance, and would not have detected bacteria that have taken up fragments of that gene, or other parts of the GM DNA containing other genes or gene fragments.

Although GM DNA was not detected in samples taken from these 3 subjects prior to GM soya consumption, when the microbes in this material were cultured in broth containing glyphosate, the transgene was detected in a sample collected before the GM meal, though at very low concentrations. This suggests that the subject may already have GM DNA in the gut prior to the experiment, possibly from consuming GM soya. The bacteria harbouring the transgene could not be isolated, so the researchers concluded that, "although present, the bacterium represented a very small proportion of the indigenous intestinal microflora". But as bacteria are capable of multiplying, even rare gene transfer events cannot be ignored.

The researchers were disingenuous when they expressed surprise at the relatively large proportion of GM soya DNA that has survived passage through the small bowel. But in earlier research already published, the same group had found that DNA in food or mixed up with food was much slower to degrade than naked DNA.

Despite the severe limitations placed on detecting GM DNA, and an experimental design both biased towards negative results, irrefutable positive evidence was nevertheless obtained. That means the transfer of GM DNA in the human gut could be much more extensive than the data indicate. This makes it all the more astonishing for the FSA to have reportedly claimed that "the findings had been assessed by several Government experts who had ruled that humans were not at risk". Those experts should now be named and made to defend their ruling.

In a statement on its website, the FSA said that the study had concluded it is "extremely unlikely" that GM genes can end up in the gut of people who eat them. This statement is highly misleading and very likely to be false.

Our government's scientific advisers have been guilty of persistent denial in the face of mounting evidence that horizontal gene transfer can happen and has happened. They are guilty of bad scientific research that misleads the public, of downplaying positive evidence, and of taking the absence of evidence as evidence of absence.

I first pointed out the dangers of horizontal gene transfer to MAFF in a series of correspondence in 1996. Their scientific advisers said there was no evidence it could happen. When it became clear that horizontal transfer of GM DNA from GM plants to bacteria can readily happen in the laboratory, the scientific advisors said "just because it happens in the laboratory does not mean it will happen in the field". When positive findings turned up in the only field monitoring experiment in the world that has ever been performed, the scientific advisors dismissed that too, and explained it away by a 'cautious' interpretation of the evidence.

This latest finding is the last piece of damning evidence that horizontal transfer of GM DNA can indeed happen, has already been happening, and cannot be controlled if GM crops continue to be released to the environment. GM DNA, as opposed to natural DNA, is in many respects optimised for horizontal gene transfer. Horizontal transfer of GM DNA can create new viruses and bacteria that cause diseases, spread drug and antibiotic resistance among pathogens, and trigger cancer by jumping into genomes of mammalian cells. New 'pharm' crops are being developed that poison our water and soil, affecting all organisms in our food web. The ecological impacts are unthinkable. What more do we need for an immediate comprehensive ban on GM crops?

Complete document with references

Natural Toxins:

Volume 6, Issue 6, 1998. Pages: 219-233
Published Online: 29 Jun 1999
Research Article

Fine Structural Changes in the Ileum of Mice Fed on -Endotoxin-Treated Potatoes and Transgenic Potatoes Nagui H. Fares 1 *, Adel K. El-Sayed 2 1Department of Zoology, Faculty of Science, Ain Shams University, Cairo, Egypt 2Department of Entomology, Faculty of Science, Ain Shams University, Cairo, Egypt email: Nagui H. Fares (nfares@asunet.shams.eun)

Abstract: The present work has been designed to study the effect of feeding on transgenic potatoes, which carry the CryI gene of Bacillus thuringiensis var. kurstaki strain HD1, on the light and electron microscopic structure of the mice ileum, in comparison with feeding on potatoes treated with the -endotoxin isolated from the same bacterial strain. The microscopic architecture of the enterocytes of the ileum of both groups of mice revealed certain common features such as the appearance of mitochondria with signs of degeneration and disrupted short microvilli at the luminal surface. However, in the group of mice fed on the -endotoxin, several villi appeared with an abnormally large number of enterocytes (151.8 in control group versus 197 and 155.8 in endotoxin and transgenic-treated groups, respectively). Fifty percent of these cells were hypertrophied and multinucleated. The mean area of enterocyte was significantly increased (105.3 µm2 in control group versus 165.4 µm2 and 116.5 µm2 in endotoxin and transgenic-treated groups, respectively). Several forms of secondary lysosomes or auotophagic vacuoles were recognized in these cells. These changes were confirmed with the scanning electron microscope which revealed a remarkable increase in the topographic contour of enterocytes (23 µm in control group versus 44 µm and 28 µm in endotoxin and transgenic-treated groups, respectively) at the divulged surface of the villi. The basal lamina along the base of the enterocytes was damaged at several foci. Several disrupted microvilli appeared in association with variable-shaped cytoplasmic fragments. Some of these fragments contained endoplasmic reticulum, as well as ring-shaped annulate lamellae. In addition, the Paneth cells were highly activated and contained a large number of secretory granules. These changes may suggest that -endotoxin-treated potatoes resulted in the development of hyperplastic cells in the mice ileum. Although mild changes are reported in the structural configuration of the ileum of mice fed on transgenic potatoes, nevertheless, thorough tests of these new types of genetically engineered crops must be made to avoid the risks before marketing. Copyright (c) 1998 John Wiley & Sons, Ltd. ... Ileum final and longest segment of the small intestine. It is specifically responsible for the absorption of vitamin B12 and the reabsorption of conjugated bile salts . The ileum is about 4 m (13 feet) in length and extends from the jejunum (the middle section of the small intestine) to the ileocecal valve, which empties into the colon (large intestine). The ileum is suspended from the abdominal wall by the mesentery. The smooth muscle of the ileum's walls is thinner than the walls of other parts of the intestines, and its peristaltic contractions are slower. The ileum's lining is also less permeable than that of the upper small intestine. Small collections of lymphatic tissue (Peyer's patches) are embedded in the ileal wall, and specific receptors for bile salts and vitamin B12 are contained exclusively in its lining; about 90 percent of the conjugated bile salts in the intestinal contents is absorbed by the ileum.

Microbiology

Genetic Transformation Of Hela Cells By Agrobacterium

Proceedings of the National Academy Sciences USA, 10.1073/pnas.041327598

Talya Kunik*, [dagger ] , [Dagger ] , Tzvi Tzfira*, Yoram Kapulnik [dagger ] , Yedidya Gafni [dagger ] , Colin Dingwall [Dagger ] ,b, and Vitaly Citovsky*,x * Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, NY 11794-5215; [dagger ] Institute of Field and Garden Crops, Agricultural Research Organization, P.O. Box 6, Bet-Dagan 50250, Israel; and [Dagger ] Department of Pharmacology, State University of New York, Stony Brook, NY 11794-8651

Edited by Eugene W. Nester, University of Washington, Seattle, WA, and approved December 8, 2000 (received for review July 13, 2000)

Agrobacterium tumefaciens is a soil phytopathogen that elicits neoplastic growths [ie. cancer] on the host plant species. In nature, however, Agrobacterium also may encounter organisms belonging to other kingdoms such as insects and animals that feed on the infected plants. Can Agrobacterium, then, also infect animal cells? Here, we report that Agrobacterium attaches to and genetically transforms several types of human cells. In stably transformed HeLa cells, the integration event occurred at the right border of the tumor-inducing plasmid's transferred-DNA (T-DNA), suggesting bona fide T-DNA transfer and lending support to the notion that Agrobacterium transforms human cells by a mechanism similar to that which it uses for transformation of plants cells. Collectively, our results suggest that Agrobacterium can transport its T-DNA to human cells and integrate it into their genome.

Super Viruses Through Genetic Engineering

Prof. Joe Cummins
February 23, 2001

Abstract: Journal of Virology, February 2001, p. 1205-1210, Vol. 75, Expression of Mouse Interleukin-4 by a Recombinant Ectromelia Virus Suppresses Cytolytic Lymphocyte Responses and Overcomes Genetic Resistance to Mousepox

Ronald J. Jackson, Alistair J. Ramsay, Carina D. Christensen, Sandra Beaton, Diana F. Hall, and Ian A. Ramshaw

Genetic resistance to clinical mousepox (ectromelia virus) varies among inbred laboratory mice and is characterized by an effective natural killer (NK) response and the early onset of a strong CD8+ cytotoxic T-lymphocyte (CTL) response in resistant mice. We have investigated the influence of virus-expressed mouse interleukin-4 (IL-4) on the cell-mediated response during infection. It was observed that expression of IL-4 by a thymidine kinase-positive ectromelia virus suppressed cytolytic responses of NK and CTL and the expression of gamma interferon by the latter. Genetically resistant mice infected with the IL-4-expressing virus developed symptoms of acute mousepox accompanied by high mortality, similar to the disease seen when genetically sensitive mice are infected with the virulent Moscow strain. Strikingly, infection of recently immunized genetically resistant mice with the virus expressing IL-4 also resulted in significant mortality due to fulminant mousepox. These data therefore suggest that virus-encoded IL-4 not only suppresses primary antiviral cell-mediated immune responses but also can inhibit the expression of immune memory responses.

Fundamentals: In the experiments described above the gene added to the virus that caused the virus to turn off immune defense was interleukin-4. Interleukin-4 is a member of the cytokine regulators of the immune system. Cytokines are proteins produced by the genes they include interleukins, tumor necrosis factor and interferons. There are presently 18 cytokines with the name interleukin (IL). Other cytokines have retained their original biological description, such as tumor necrosis factor (TNF). Another way to look at some cytokines is their role in infection and/or inflammation. Some cytokines clearly promote inflammation and are called proinflammatory cytokines, whereas other cytokines suppress the activity of proinflammatory cytokines and are called anti-inflammatory cytokines. For example, IL-4, IL-10, and IL-13 are potent activators of B lymphocytes. However, IL-4, IL-10, and IL-13 are also potent anti-inflammatory agents. They are anti-inflammatory cytokines by virtue of their ability to suppress genes for proinflammatory cytokines such as IL-1, TNF, and the chemokines. Interferon (IFN)-[Gamma] is another example of the pleiotropic nature of cytokines. Like IFN-[Alpha] and IFN-[Beta], IFN-[Gamma] possesses antiviral activity. IFN-[Gamma] is also an activator of the pathway that leads to cytotoxic T cells. However, IFN-[Gamma] is considered a proinflammatory cytokine because it augments TNF activity and induces nitric oxide (NO). In summary, the cytokines both promote and prevent inflammation. Some fight pathogens while others shut down defense against pathogens. Cytokines modulate the numerous immune functions.

Our comments [by Joe Cummins]: The study described above clearly shows that genetic recombination is capable of creating virus (or other pathogens) with genes that allow the pathogen to overcome host defense and to spread with little or no control. There is growing evidence that viruses have used strategy of that type to overcome host defense during the course of their evolution. However, genetic modification will greatly hasten the mixing of regulatory cellular genes and virus genes. Gene therapy experiments may create dangerous pathogens, but can crop genetic engineering lead to creation of dangerous pathogens. Cytokine genes from human and animals have been extensively introduced into crop plants which have been tested in the open environment in field crops. Such experiments could easily lead to production of insect baculoviruses bearing human genes by recombination between the human genes in crops and the insect viruses. The insect baculoviruses readily infect human liver which normally produces non-pathogenic infection but with human genes inserted infections could be devastating. Certainly, a wide range of new pathogens may be created by genetic recombination and experimenting with human gene constructions in the open environment invites such pathogens to produce themselves. The production of novel plant pathogens should also be considered because their production is highly likely. Here, the analogy between animal viruses and mammalian regulators also extends to plant viruses and the plant defense genes. In conclusion, genetic engineering is proving its ability to create novel devastating pathogens.

Report of Gene Transfer from GE Rapeseed
to Bacteria and Fungi in the Gut of Bees

These are the latest results from risk research in Germany:

The German Television ZDF reported on Sunday May 21 that a German researcher found a gene transfer from genetically engineered rapeseed to bacteria and fungi in the gut of honey bees. Prof. Hans-Hinrich Kaatz from the Institut fur Bienenkunde (Institute for bee research) at the University of Jena experimented during the last three years with honey bees on an experimental field with transgenic rapeseed in Saxony, Germany.

The field trial was performed by AgrEvo, the rapeseed was engineered to resist the herbicide glufosinate (Liberty, Basta). Prof. Kaatz built nets in the field with the transgenic rapeseed and let the bees fly freely within the net. At the beehives, he installed pollen traps in order tosample the pollen loads from the bees' hindlegs when entering the hive.

This pollen was fed to young honey bees in the laboratory. (Pollen is the natural diet of young bees which need a high protein diet). Then Prof.Kaatz took the intestine out of the young bees and spread the contents on growth medium to grow the microorganisms.

He probed the microorganisms for the pat-gene, the gene that conferes resistance to glufosinate. In some bacteria and also in a yeast, he found the pat-gene. This indicates that the gene from the genetically engineered rapeseed was transferred in the bees gut to the microbes.

The Fate Of Forage Plant DNA In Farm Animals

European Food Research and Technology
Abstract Volume 212 Issue 2 (2001) pp 129-134

A collaborative case-study investigating cattle and chicken fed recombinant plant material

R. Einspanier (1), Andreas Klotz (1), Jana Kraft (2), Karen Aulrich (3), Rita Poser (4), Fredi Schwagele (4), Gerhard Jahreis (2), Gerhard Flachowsky (3)

(1) Institut fur Physiologie, FML, Weihenstephaner Berg 3, Technische Universitat Munchen, 85350 Freising, Germany e-mail: einspani@weihenstephan.de Tel.: +49-8161-713510 Fax: +49-8161-714204
(2) Institut fur Ernahrung und Umwelt, Friedrich Schiller Universitat, Dornburger Str. 24, 07743 Jena, Germany
(3) Institut fur Tierernahrung, Bundesforschungsanstalt fur Landwirtschaft, Bundesallee 50, 38116 Braunschweig, Germany
(4) Institut fur Chemie und Physik, Bundesanstalt fur Fleischforschung, Baumann Str. 20, 95326 Kulmbach, Germany

Received: 23 February 2000 / Revised version: 20 March 2000

Abstract: The fate of ingested recombinant plant DNA in farm animals (cattle and chicken) being fed a diet containing conventional maize or recombinant Bacillus thuringiensis toxin-maize (Bt-maize) is described. The probability of the detection by polymerase chain reaction of chloroplast-specific gene fragments of different lengths (199 bp and 532 bp) and a Bt-maize-specific fragment [truncated version of CryIA(b)] is shown. First data indicated that only short DNA fragments (<200 bp) derived from plant chloroplasts could be detected in the blood lymphocytes of cows. In all other cattle organs investigated (muscle, liver, spleen, kidney) plant DNAs were not found, except for faint signals in milk. Furthermore, Bt-gene fragments possibly recording the uptake of recombinant maize, were not detected in any sample from cattle. However, in all chicken tissues (muscle, liver, spleen, kidney) the short maize chloroplast gene fragment was amplified. In contrast to this, no foreign plant DNA fragments were found in eggs. Bt-gene specific constructs originating from recombinant Bt-maize were not detectable in any of these poultry samples either.

Transgenic Insecticidal Corn: Beyond Insecticidal Toxicity to Ecological Complexity

John J. Obrycki, John E. Losey, Orley R. Taylor, and Laura C. H. Jesse
358 BioScience
May 2001 / Vol. 51 No. 5

Conclusions and recommendations

Unlike the use of transgenic potatoes and cotton, the use of transgenic corn will not significantly reduce insecticide use in most of the corn-growing areas of the Midwest. During the past 5 years, the percentage of field corn treated with insecticides in the United States has remained at approximately 30%, despite a significant increase in the hectares of Bt corn planted (Figure 2).From 1995 to 1998, about 1% to 2% of the corn grown in Iowa--where over 4 million hectares of corn are grown annually--was treated with insecticides for O. nubilalis (Figure 3).A survey of veteran corn farmers in Iowa and Minnesota--the average farming career was 21 years--showed that 70% had never used insecticides for the first generation of the corn borer, and 82.7% had never treated for the second generation (Rice and Ostlie 1997).Approximately 5% had used insecticides three or more times in 21 years to manage the corn borer.

Despite the relatively low use of insecticides during the 1990s for corn borer suppression, between 20% and 30% of the corn planted in the United States in 1998 and 1999 was transgenic (Fernandez-Cornejo and McBride 2000), suggesting that the Bt plantings are not being used as a replacement for insecticides but in addition to them. A core concept of integrated pest management is to use a management tactic only when pest populations exceed a threshold level. It seems, then, that the hectares planted in Bt corn represent a change in approach from management of O. nubilalis to a prophylactic strategy.

Because population densities of the European corn borer are unpredictable, the economic benefits of using transgenic corn are not assured (Rice and Pilcher 1998,Hyde et al. 1999, Archer et al. 2000).Comparisons of yields from transgenic and genetically similar nontransgenic corn hybrids grown in replicated plots in 14 to 16 locations in Iowa (Farnham and Pilcher 1998, Rice 1998) showed that only 34% of the transgenic lines produced significantly higher yields in 1997. In locations where corn borer damage was highest in nontransgenic lines, 50% to 58% of the transgenic hybrids produced significantly higher yields. In 1998, when corn-borer densities were generally lower than usual in Iowa, 12% of transgenic lines produced significantly higher yields.

Further analysis of these comparative data shows a weak relationship (r2 = 0.13) between the amount of insect damage and increased yields in the Bt corn in 1997 and no relationship in 1998. Analysis of a second data set collected for the USDA National Agricultural Statistics Survey in 1998 showed no economic benefit of transgenic insecticidal corn in Iowa (Duffy and Ernst 1999), probably because of differences in the amount of fertilizer applied to the Bt and non-Bt fields. Previous assessments of Bt corn have indicated that the economic benefits of this technology are highly dependent on the population densities of the corn borer and the market value of field corn (Rice and Pilcher 1998). From 1997 to 1999, corn borer densities were generally low in Iowa and the value of field corn had declined. Thus, in these 3 years the economic benefits of Bt corn were not consistently demonstrated.

Given the limited benefits for insect management and the documented ecological effects of transgenic insecticidal corn on nontarget species,we conclude that this biotechnology has a limited role in management of lepidopteran pests in corn. The use of transgenic crops has been promoted as safer for humans and the environment than use of broad-spectrum insecticides (Pimentel and Raven 2000). However, most field corn in the US corn belt is not treated for above-ground insect pests, and most corn hybrids already have substantial resistance to corn borers (Barry and Darrah 1991).

The approach taken in the registration of transgenic corn and in its current use in pest management has been narrowly focused on insecticidal toxicity, but we believe that a more comprehensive approach is required (see, e.g., Stern et al. 1959, Lewis et al. 1997), one that considers the ecological complexity of agroecosystems (Figure 1b).We have outlined in this article the potential benefits and ecological risks of the use of Bt corn. These potential risks are not thoroughly addressed in the US governmental registration process, an oversight that should be attended to.

The widespread and unquestioned acceptance of Bt corn by the agricultural research, regulatory, and educational communities is similar to the rapid adoption and deployment of synthetic insecticides in the early 1950s.During that time ecologically based management programs suffered, and predicted adverse ecological and environmental effects were generally ignored, resulting in limited management options for farmers as targeted species developed resistance and nontarget predator and parasitoid species declined.We are not advocating the elimination of Bt corn, nor do we discount the potential benefits of biotechnology for agriculture.We do argue, however, that a balanced examination of Bt corn suggests ways to improve the regulatory process and to incorporate this technology into an integrated control framework, and we caution against the acceptance of yet another silver bullet for pest management.

Effects of Klebsiella Planticola SDF20 on Soil Biota
and Wheat Growth in Sandy Soil.

Holmes, M.T., E.R. Ingham, J.D. Doyle and C.W. Hendricks.
Applied Soil Ecology 11: 67-78. 1999.

Read about the Klebsiella planticola research

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