Plant Biotech Blog

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

Technologies come with some concomitant and some consequential benefits, both of which should be taken together in assessing the total benefits that accrue.   No technology is risk free.   Benefits of a technology should hence be weighed against minimal and acceptable risks and a favourable cost-benefit ratio.  

Risk assessment, mitigation and management are at the heart of regulatory processes.   Planting a non-Bt refugium along with Bt crops is a means of mitigating the risk of acquired resistance, and so is gene stacking (see the article ‘Transgenic Bt Technology: 2. Bt Crop varieties’ in this series). 

Stakeholder acceptance of a technology is rooted in a rational and balanced projection and not in hype.   Factual information will enhance the credibility of the establishment and help the consumer take educated and lasting decisions.

Concomitant benefits of Bt technology:  The most direct and the most important benefit of Bt technology is the control of the most damaging pest of particular crop, such as the American bollworm of cotton, stem borers of rice and corn, rootworm of corn, Colorado beetle of potato or stem and fruit borers of aubergine (brinjal).   As systemic pesticides, Bt proteins take care of these pests.   The other pests, on which Bt proteins have little or no effect, need to be controlled by pesticide application, preferably as a part of Integrated Pest Management (IPM) practices.

Bt technology imparts only tolerance of the targeted pest of a particular crop and not total resistance to it.  In view of the variation in the expression of Bt genes, due to various internal and external factors (see the article ‘Transgenic Bt  Technology: 4. Variation in Gene Expression, in this series), two or three pesticide applications are needed, against even the targeted pest, such as the bollworms of cotton, instead of the usual 10 to 20.   Even so, in a country like India, where over 50 per cent of pesticide application is on cotton, Bt technology results in a very substantial savings on pesticide costs and labour costs associated with pesticide application, provided the farmer does not resort to ill-advised or panic spraying.

A report from ISAAA (Brief No. 37, 2007) has reported diverse benefits from GE crops over a period of about 12 years of commercialization.  In India, from 2002 to 2007 there was an increase of farmer profits between 50 to 110 per cent, with yield increase between 30 to 60 per cent.  There was about 50 per cent reduction in pesticide usage.

Significantly, suppression of cotton bollworm in multiple crops in areas with Bt cotton was reported from China (Science, September 2008).

Optimal cultivation practices are mandatory:  Any crop should be grown under optimal conditions to obtain the best benefits from the new technology.   Although cotton is hardier than many other crops, it performs satisfactorily only under irrigation.   In India, cotton is often grown under near impossible conditions, as farmers are lured into growing a cash crop, irrespective of the inappropriate infrastructure, and suffer disastrous consequences.   The Government of Andhra Pradesh, India, rather unsuccessfully advised the farmers to avoid growing cotton on red soils, particularly as a rain fed crop.  A long time advice to grow cotton only in areas with the average rainfall of more than 60 cm per year, uniformly distributed throughout the crop season, is largely unheeded.   In many developing countries, the record of both the advice given to the farmers and of farmers taking it seriously, is dismal.  

Consequential benefits of Bt technology:  Bt technology’s consequential benefits are:

a) a healthy crop, more biomass and more yield;
b) reduced risk to farm labour involved in pesticide application; in the developing countries several thousand farm workers suffer or even die, due to unintended pesticide poisoning;
c) far lower concentrations of pesticide residues on the produce and in the environment;
d) reduced exposure of non-target organisms in the environment to pesticides, and so a better conservation of biodiversity; and
e) the Bt farmer experiences a far lower tension and is certainly better off with Bt technology than the earlier scenario of ‘spray and pray’.

What is not to be expected of Bt technology:  Bt technology has no role to play in the following areas:

a) Yield: Bt technology has no gene based influence on crop yield; nevertheless, there is a substantial increase in yield due to prevention of loss of the crop produce caused by the pests; Bt farmers in India earned Rs. 6,000 (about US$ 135) more per acre, than the non-Bt farmers during the last season (ISAAA (Brief No. 37, 2007);
b) Seed germination: failure of seed to germinate is often mischievously attributed to Bt technology; causes for the failure of seed germination lie in the varieties or cultivation practices or environmental factors; the percentage of germination of the seed of a Bt variety would be about the same as that of its isogenic;
c) Non-target pests:  Bt technology is specific pest targeted and has little or no effect on other pests;
d) Diseases:   Bt technology does not cause or control any viral, bacterial or fungal diseases; such diseases as the viral leaf curl prevalent in northern India or the physiological disorder para-wilt that occurs after a heavy rain fall preceded by drought conditions, are erroneously or deliberately attributed to Bt technology. 

It is a compulsive habit of the antitech activists to repeatedly attribute farmer suicides in India to the failure of Bt cotton crop.  A comprehensive review on the issue (October 2008) found no evidence in support of the allegation and it even pointed out that the number of suicides has actually come down after the introduction of Bt cotton cultivation. 

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:  6. BIOSECURITY

January 1, 2009

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

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

The US Food and Drug Administration (FDA) routinely and stringently used the Principle of Substantial Equivalence (PSE) for decades to assure the public of the safety of foods and drugs. This criterion refers only to the product and not the process of its production.   On account of the high standards of FDA’s regulatory oversight, most other countries generally approve drugs and pharmaceuticals on the basis of FDA’s approval.  

PSE is now being applied to products from genetically engineered organisms (GEOs), in order to assure the consumer that the product is ’substantially equivalent’ (SE) to its conventional counterpart and so is safe for human consumption.   In the context of modern agricultural biotechnology, PSE is frequently an issue for serious discussion

The FDA has long considered GE crops to be substantially equivalent to conventional varieties and required no other regulatory review.   However, using the ‘provision for voluntary consultation’, biotech companies in the US seek independent SE certification by FDA, of all GE varieties and their products that are marketed in the US.

The policy of the FDA did not result in any health concerns but invited criticism on account of, a) the FDA itself has a mandatory process for approving transgenic animals, b) the US Environment Protection Agency (EPA) and the US States Department of Agriculture (USDA) have a mandatory and open process for evaluating the biosafety of transgenic plants, and c) the data are provided by the product developers (and so are suspect). 

Products from transgenics of such crops as soybean, tomato, corn, cotton, etc., on the US markets have been tested extensively and judged substantially equivalent to their conventional counterparts.   Some products may contain miniscule quantities of one or two additional proteins, which are usually broken down during processing or digestion, or some others may contain some compounds not occurring in the counterparts but at below threshold levels. Such products are categorized as ‘Generally Recognized As Safe’ (GRAS).  

The presence in the GEOs, of new genes that would code for fats, proteins or carbohydrates, that may be toxic or may cause allergies or may adversely affect the nutritional value of the product, prevents certification as SE or GRAS, without appropriate and adequate testing.   

While in the US no labeling as SE or GRAS is mandatory, it is not so in several other parts of the world. This leads to considerable confusion and controversies. Suggestions were made for the application of PSE to all products of genetic engineering, including livestock feed and GE crops, which raises certain questions.

In the application of PSE, the comparison should be between the GE variety and its isogenic, which is the basic variety into which a transgene was inserted.   The certification is to the effect that the GE crop variety is substantially equivalent to its isogenic, in genotype, marked characteristics and performance, but for the transgenes and their anticipated characteristics.   If the isogenic were safe, the transgenic would be equally safe, provided that the newly introduced transgenes do not exercise any adverse effects by themselves or through altering the expression of any other genes of the isogenic, in the transgenic environment.   Such an assurance requires scientific evaluation of the crop variety first, and then of its products. This involves additional efforts, time and expense, raising consumer costs.    

All US agricultural biotechnology companies submit to the FDA, voluminous dossiers on the safety and risk analysis of the GEOs and their products developed by them, before the products are on the US markets. Such a voluntary mechanism should be global, although antitech activists look down upon data provided by the product developers.  If testing standards and procedures in different countries were uniform, what is considered safe in one country should also be considered so in other the countries.  This will eliminate the need for repeating the same and every test in every country.

At no time, transgenics can be substantially equivalent to their isogenics in their entire genotypes and this is not related to transgenic technology.   Even to start with, members of the same population are not entirely genetically identical.   In addition, mutations occur naturally and randomly, involving different genes.  Lethal mutations are naturally eliminated. Mutations of the genes of the desired characteristics are eliminated in the process of selection, but those that do not affect the desired characteristics escape attention and accumulate. After a certain number of generations, a critical genetic analysis will contravene SE, although SE can be established for the genes of the desired characteristics.   Such a situation would cause problems in some countries, where the regulatory authorities apply the principle of SE more in letter than in spirit, and a lot more strictly than in other countries.  

 The official European consensus is that SE should only be used to guide to inform safety assessments. Codex Alimentarius sees it as a starting point in the regulatory process rather than an end point. However, in the US, SE still plays a significant role in the regulation and commercialization of GE foods.

Notwithstanding the importance given to PSE, it has been criticized as vague, ill defined, flexible, malleable, open to interpretation, unscientific and arbitrary (Ho, M.W. and Steinbrecher, R. (1998)). 

On account of such concerns, PSE should be re-examined, and for re-defining its applicability to GE crop plants and their products, laying emphasis on a reasonable application of the principle, addressing only those genes and their products that are relevant to the objectives of developing a particular transgenic variety or product.   There is also a dire need for a uniform and harmonized international policy.   At the moment, there is no evidence that SE is an issue that adversely affects the safety of Bt transgenics or their products.

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:  6. BIOSECURITY

TRANSGENIC BT TECHNOLOGY: 7. BENEFITS

January 1, 2009

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

Natural variation in gene expression: The tendency to vary is the only consistent feature of Nature.   All species of organisms, whether wild or cultivated, show naturally inherent variation in physical, chemical and physiological features, which is also the basis for distinguishing different species, varieties.   Each species or variety shows some variation in several features both between and within its populations.   Nevertheless, species and varieties have a set of discernible and invariable features characterizing their identity.   For example all transgenic Bt cotton varieties contain some quantity of Bt protein, though the actual quantities of the protein may vary from one variety to the other, as well as within each variety.   In addition, there is a) variation related to time (temporal), based in the age of the individual/population reflected in the growth phase such as vegetative, flowering, fruiting and other stages, and b) spatial variation within an individual specimen reflected in different parts of the plant such as the root, stem, leaf, floral parts, fruits and seeds. 

By centuries of experience, biologists in general and agricultural scientists in particular, fully understand that the expression of the same gene or set of genes is influenced by several factors, some inherent in the organism and some in the environment. Some of this variation, called genotypic variation, is based in the differences in the genetic constitution (genotype) between the varieties.   The other kind, called phenotypic variation, is the result of an interaction between the genotype and the environment, so much so the same genotype behaves differently in different areas and seasons.     Cultivation and management practices also influence gene expression and so the crop’s performance.  Consequently, no crop variety, either conventional or genetically engineered, can be expected to perform uniformly throughout the entire area, or history of its cultivation.  

The full expression of the transgenes in a transgenic crop variety is crucial, but transgenic varieties may behave differently depending upon the genotype of the recipient variety and on where and how it is being cultivated, as has happened also in conventional agriculture all through.   Most of the factors that affect gene expression are beyond the control of the plant breeders and biotechnologists, once a variety is chosen for transgenic development.  

Agro-climatic zones and crop varieties: The physical and chemical characteristics of a) the soil, b) the quantity, periodicity and distribution of rainfall and/or irrigation facilities, and c) the range of temperature, are factors important for a healthy crop life.   These factors, which vary from country to country and even within a country from region to region, are very critical to successful agriculture.  Taking all such relevant factors together, several agro-climatic zones, each characterized by a set of soil, rainfall (or irrigation facilities), and temperature parameters, are identified in countries with diverse geographical features.   The Planning Commission of India has recognized 15 agro-climatic zones in India, and these are further divided into about 120 sub-zones.   Each agro-climatic zone or sub-zone requires varieties of crops particularly suitable to be grown there.   Consequently, a very large number of varieties of different crops was developed by farmers and agricultural scientists in different parts of the world, over centuries, either to suit a particular agro-climatic zone and for certain beneficial traits in them.   As a result, there are over 1,00,000 varieties of cultivated rice, some 80,000 varieties of wheat, and about 15,000 varieties each of potato and the bean in the world today.  

Transgsenic Bt crop varieties: Transgenic Bt cotton containing Cry1Ac was originally developed using the American cotton variety Cocker 312, and this variety is not suitable for cultivation outside America.   Different local varieties of cotton are chosen for developing transgenic Bt cotton varieties, incorporating the same Cry1Ac event, for cultivation in different agro-climatic zones in different countries.    There are now over about 140 approved varieties of transgenic Bt cotton in India, containing the same Cry1Ac transgenic event, and most of them marketed under the Monsanto’s trade name Bollgard I.    The situation is similar with all transgenic events.   The Golden Rice event was first inserted into the genome of a temperate japonica variety and the event had to be transferred to the indica varieties for cultivation in different rice growing agro-climatic zones in tropical countries.   The costs of developing so many varieties with the same transgenic event and the costs of the associated regulatory processing of all these varieties escalate steeply by the time the transgenic products reach the consumer.

Variation in the expression of Bt genes: Even when Bt crop varieties are cultivated in the recommended agro-climatic sub-zone, there would be significant differences in the expression of Cry1Ac gene in them.  

The general health of the crop is an important factor in realizing the full genetic potential of a crop variety.   The expression levels of a gene may decrease as the age of the crop advances.   There may be differences in expression levels between young and older parts such as the leaves or between comparable parts in vegetative and reproductive phases.   Such variation in the expression of Bt event in cotton was observed in Australia and India.

Soil characteristics, rain fall, the severity of pests and diseases, adequate, appropriate and timely farming inputs such as irrigation, weeding, fertilizer, supportive pesticide application, all have a direct or indirect influence on the performance of the crop and may affect the expression of the transgenes and so the benefits to be derived from transgenic technology.   All these factors, inherent in the varieties and/or the environment vary from crop season to season, make the difference between supraoptimal, optimal or suboptimal performance of a crop or even its failure.
 
Transgenic Bt technology produces crop varieties that are only tolerant of the targeted pests and not fully resistant to them.   The farmer has to be advised on the varieties suitable for cultivation in an area and the appropriate practices and precautions needed in every crop season, in order to derive the maximum possible benefit during each season.  The objective of transgenic technology is to derive cost effective benefits of the technology over a considerable period of time and not in a particular season or in a particular region in a season.   No crop variety has ever performed uniformly season after season in all regions of its cultivation.  

Ignoring the factors that control crop performance is poor crop husbandry.   Technology should not be blamed for ills befalling for reasons of poor management that lie beyond the realm of a particular 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: 5. SUBSTANTIAL EQUIVALENCE OF TRANSGENICS AND THEIR ISOGENICS

TRANSGENIC BT TECHNOLOGY:  6. BIOSECURITY

TRANSGENIC BT TECHNOLOGY: 7. BENEFITS

 January 1, 2009