Plant Biotech Blog

C Kameswara Rao
Foundation for Biotechnology Awareness and Education, Bangalore, India
pbtkrao@gmail.com

In the context of modern agricultural biotechnology the term Biosecurity has two components:  a) Biosafety, the safety of genetically engineered (GE) organisms and/or their products to humans and animals as food, feed and medicine, and b) Environmental safety, the safety of non-target organisms, soil and water.  The terms biosecurity and biosafety are often used incorrectly as synonyms.  

Biosecurity issues raised to oppose GE crops by antitech activists are relevant to even to products of classical agricultural biotechnology, but were never made an issue in that context.  

It was the international scientific community, not the antitech activists, who have identified the possible biosecurity risks from the transgenic crops and devised testing and mitigation protocols.    Science has reasonable peer reviewed experimental evidence to answer biosecurity concerns.   The regulatory process in every country ensures that all questions are answered reasonably satisfactorily before commercialization is permitted. Most of those who raise biosecurity issues to voice their opposition to GE crops have no locus standi in terms of scientific knowledge and expertise to trash the combined global scientific wisdom.

Biosafety of Bt:  Bt being a universally occurring soil bacterium, all species of plants and animals in agricultural and other situations, and those that use plants as food have been exposed to Bt and Bt proteins for centuries.   Bt proteins are transient in the environment  The toxicity of Bt proteins is pest specific, dependent upon a set of biological pre-requisites.  The use of Bt as a conventional pesticide for over 60 years has demonstrated that it is safe to a variety of non-target organisms.   Cry proteins were shown to be harmless to vertebrates, including mammals and humans, even at high doses, by ingestion, inhalation or injection. For details see the other six articles in the series ‘Transgenic Bt Technology’ on this website.

Bt is one of the few pesticides recommended for widespread application in North America, and was broadcast or sprayed on crops and air sprayed to control forest pests in Utah (US, 1990-1995) and Ontario (Canada, 1985-1994).   Water borne Bt was air sprayed to control the Asian gypsy moth in Vancouver (Canada, 1988), and North Carolina (US, 1993) and the white-spotted tussock moth in Auckland (New Zealand, 1996).   Over 350 million people in North America have been eating Bt products for over a dozen years.  No greater testimony is needed for human safety of Bt than that no adverse effects on the human population have been reported so far.  

Toxicity and allergenicity:  Antitech activists raise issue after issue to brand GE crops as toxic.  Reports of the death of peacocks and the death of farm animals in Andhra Pradesh and honey bee Colony Collapse Disaster in Europe and North America, were attributed to the presumed toxicity of Bt proteins in GE crops.  These incidents projected as major issues have been effectively shown to be due to causes other than Bt protein toxicity. 

Several claims have been made of allergenicity of transgenic crops, including Bt cotton in some places in India, but there has never been any scientific evidence. 

A transgenic soybean with a gene for the Brazil nut protein developed to increase the content of  methionine, an essential amino acid, was one of the targets.   Though no one actually developed allergy by eating the transgenic soybean, since the transgenic is likely to affect people who are allergenic to Brazil nuts, Pioneer Hi-Bred International, the developer of the product, did not proceed with it, setting an example of self-regulation.  

The United States Department of Agriculture (USDA) cleared Aventis Starlink Bt corn for use as both food and feed.  Since the Bt Cry9 protein in this transgenic corn was projected to be allergenic, the US Environment Protection Agency (EPA) took a precautionary measure and approved this corn only for animal feed, as animals do not generally suffer from food allergies.   Bt Cry9 protein was never demonstrated to be allergenic.  The US Centers for Disease Control (CDC) tested 17 samples of blood from people claimed to have developed allergenic reactions to Starlink and found that none of the blood samples showed cross-reactivity to Cry9 Bt protein.  The Cry9 gene is not deployed in any commercial product now.   Since transgenic products approved as only feed may accidentally get into the food products, no transgenic is now approved exclusively for use as feed.    This shows that the regulatory regime is in fact functioning effectively.

Impact of Bt on non-target organisms:  Glare and O’Callaghan (‘Bacillus thuringiensis: Biology, Ecology and Safety’ 2000, John Wiley), and every country’s regulatory process provide extensive data demonstrating the safety of Bt proteins to non-target organisms.  

The much-brandished instance of toxicity of Bt proteins to non-target organisms was based on the study by Losey, et al.,  (Nature, 1999) who reported that transgenic Bt corn pollen harm monarch larvae, a conclusion immediately questioned by Hodgson (Nature Biotechnology, 1999).   Subsequently, Sears, et al., (2001) re-examined the issue, avoiding the flaws in the experimental design in the study of Losey et al., and concluded that impact of Bt corn pollen on monarch butterfly populations was not significant.

A February 2008 publication indicates that Cry 1Ab Bt proteins do not affect the performance of bumble bees in any manner.

In May 2008 Bt Cry1C proteins were shown to be safe to parasitoids that control pest populations in many crops, in contrast to the severe damage caused to the parasitoids by the traditional insecticides.

Vertical gene flow:  The essential pre-requisite for vertical gene flow is sexual reproduction between the transgenics and related plants.   The transferred genes express only in the next generation.   The ease of vertical gene flow depends upon the genetic relationships between the varieties and whether the crop is self or open pollinated, which Bt technology cannot change.   Transgenics are no more promiscuous than their isogenics.   If vertical gene flow were possible between isogenics and any related varieties or species, it would be so between transgenics and related plants too.   However, centuries of agricultural experience does not indicate any alarming possibilities. 

A study, much quoted by the critics as a risk of vertical gene flow, relates to Bt maize in Mexico.   Quist and Chapela, (Nature, 2001), reported the presence CaMV 35S promoter and a Bt gene, ‘traced’ to Bt maize, in native maize populations in Oaxaca, Mexico.   They claimed that the genes got incorporated into the native land race and that the promoter was out of control and may activate any other genes.   The scientific community challenged the methodology and the conclusions, which lead Nature to announce that it should never have published the paper.   Ortiz-Garcia et al., (PNAS, 2005) have analyzed 1,03620 corn seeds collected during 2003-04, from 125 fields at 18 locations, in the State Oaxaca, Mexico, the same area as of Quist and Chapela’s study, and found no evidence of the transgenes in native maize populations.  The defense was that the genes were there in 2001 and vanished subsequently!

Lateral/horizontal gene flow:  Lateral/horizontal gene flow involves exchange of genes between genetically unrelated organisms, a fact of evolution, but not of day-to-day occurrence.   It does not involve sexual reproduction and the transferred genes can express in the same generation.   Transgenic technology itself is an example of lateral gene transfer.   All known examples of lateral gene transfer relate to endoparasites and their hosts, as for example, the commonality of about 30 per cent of genes between mammalian intestinal parasites and their hosts.   

The use of antibiotic markers in transgenic technology, to confirm genetic transformation was used to create the fear of GE technology.  The argument, not supported by any tangible evidence,  is that if there were lateral transfer of antibiotic resistance genes to pathogenic organisms, it would result in pathogens resistant to the antibiotics used as markers and endanger our prospects in the fight against the new pathogens using the antibiotics to which they are resistant.  Supported by numerous studies, a report in Transgenic Research (June, 2007) concluded that there is no scientific basis to argue against the use and presence of selectable antibiotic resistant marker genes in transgenic plants.  However, to assuage the fears expressed, the use of antibiotic resistance marker genes is now minimized, as alternatives are found.   The antibiotic marker genes can also be removed, after confirming genetic transformation.

How safe are Bt transgenics?  All the evidence indicates that Bt transgenics are very safe and over a decade’s cultivation of Bt transgenics has neither confirmed the scary scenarios aired by the critics nor has thrown up any new threats. 

A comprehensive report on the impact of agricultural biotechnology on biodiversity from the Bern University’s Botanic Garden (2004) reiterated that the introduction of GE crop varieties does not represent any greater risk to crop genetic diversity than the varieties of conventional agriculture.  GE actually increases crop diversity by adding new varieties.

A peer reviewed report of March 2007 stated that no aspect of credible science based on ten years of field research and commercial cultivation has indicated that GE crops have harmed biodiversity or the environment.

The Consensus Document from the Organization for Economic Cooperation and Development (No. 42, 2007) on the safety of Bt proteins in transgenic plants did not identify any hazards caused by them.  

Biosecurity issues are unfortunately often mixed up with political, economic, management, societal and ethical issues, emotionalizing and sensationalizing the concerns, to spread fear and suspicion of GE technology. 

Other articles in this series:
TRANSGENIC BT TECHNOLOGY: 1. BACILLUS THURINGIENSIS, BT PROTEINS AND TOXINS

TRANSGENIC BT TECHNOLOGY: 2. BT CROP VARIETIES

TRANSGENIC BT TECHNOLOGY: 3. EXPRESSION OF TRANSGENES

TRANSGENIC BT TECHNOLOGY: 4. VARIATION IN GENE EXPRESSION

TRANSGENIC BT TECHNOLOGY: 5. SUBSTANTIAL EQUIVALENCE OF TRANSGENICS AND THEIR ISOGENICS

TRANSGENIC BT TECHNOLOGY: 7. BENEFITS

January 1, 2009