Risk Assessment and Management in Transgenic Crops

Transcription

1 Risk Assessment and Management in Transgenic Crops P. Balasubramanian Director Centre for Plant Molecular Biology Tamil Nadu Agricultural University Coimbatore

2 Status of Development of Bt Brinjal at TNAU

3 Bt Brinjal Programme Network programme involving TNAU, Coimbatore, University of Agricultural Sciences, Dharwad, Indian Vegetables Research Institute, Varanasi and Mahyco, Jalna Project funded by Agricultural Biotechnology Support Programme II of USAID and Department of Biotechnology, Government of India Mahyco provides the Bt gene Public sector institutes develop Bt brinjal varieties

4 Objective Development of Bt brinjal varieties expressing resistance to fruit and shoot borer Development of Bt brinjal lines in local elite genetic background keeping in view the local consumer preference Facilitating resource-poor farmers to save seeds for their future use

5 Programme Mahyco brinjal event EE1 expressing cryiac used as donor to introgress the gene into local elite backgrounds through back- cross breeding programme With a view to developing Bt versions Co2, MDU1, PLR1 and KKM1 are used as recurrent parents

6 Progress and future programme BC 2 F 1 progenies are being evaluated in transgenic greenhouse BC 3 F 1 will be produced Superior plant types will be identified in BC 3 F 2 and BC 3 F 3 generations Bioassay on homozygous transgenic lines Field testing

7 Co2 PLR1 KKM1 MDU1

8 Bt eggplant research at TNAU

9 History of Technology Adoption Resistance to Innovations Related to Food Pasteurization Change is Inevitable Progress is Optional

10 History of Technology Adoption Resistance to Innovations Related to Food Canning Change is Inevitable Progress is Optional

11 History of Technology Adoption Resistance to Innovations Related to Food Freezing Change is Inevitable Progress is Optional

12 History of Technology Adoption Certain Innovations Not Readily Accepted Recalcitrance to Adopt (Dvorak v/s QWERTY) Change is Inevitable Progress is Optional

13 History of Technology Adoption Certain Innovations Not Readily Accepted Entrenched Economic Interests (Metric in US) Change is Inevitable Progress is Optional

14 Risk, defined The probability of a hazard The probability of exposure to hazard

15 Where RISK Risk = f (hazard, probability) Risk = f (exposure x hazard), exposure is the frequency at which an event occurs and hazard is the magnitude of the impact of that event

16 Risks, examples Risks for animal and human health Toxicity & food quality safety Pathogen drug resistance Risks for the environment Persistency of gene of transgene (volunteers, increased fitness, invasiveness) or transgenic products (accumulative effect) Susceptibility of non-target organisms Increased use of chemicals in agriculture Unpredictable gene expression or transgene instability

17 Risks, examples Risks in agriculture Resistance or tolerance of target organism Weeds or super weeds Alteration of nutritional value (attractiveness of the organism to pests) Horizontal gene transfer Genetic pollution through pollen or seed dispersal Transfer of foreign gene to microorganism (DNA uptake) or generation or new live viruses by recombination Interaction among different GMOs

18 Risk analysis, three steps in Risk assessment evaluates and compares scientific evidence regarding the risks associated with alternative activities Risk management develops strategies to prevent and control risks within acceptable limits and relies on risk assessment Risk communication involves an on-going dialogue between regulators and the public about risk and options to manage risk so that appropriate decisions can be made

19 General risk assessment of GMOs is different from that of chemicals GMO are living organisms Potential to disperse to new habitats, colonize these sites and multiply Their novel activity (production of metabolic products, enzymes, toxins) will occur as long as GMOs remain metabolically active Once established, living organism cannot be recalled

20 Risk assessment Identifying and evaluating possible dangers predicting the chances the danger will occur assessing the extent of damage should the danger occur

21 Risk assessment Science-based Transparent Case by case by transformation event Absence of scientific evidence is not construed to imply safety nor danger Risk assessment is revisited if new evidence is found

22 Risk assessment In order to be able to assess the environmental safety of a genetically engineered plant, one must be familiar with both the biology of the plant itself, This concept of familiarity is a key approach used in identifying and evaluating environmental risks (i.e., hazards) that may be associated with the release of a genetically engineered plant and also in informing management practices that may be needed to manage recognized risks. Familiarity considers the biology of the plant species,, the trait,, and the agricultural practices used in the production of the crop.

23 The Biology of the Plant Species A Monograph may be used to identify species-specific specific characteristics that may be affected by the novel trait so as to permit the transgenic plant to become weedy,, invasive of natural habitats, or be otherwise harmful to the environment. It can also provide details on significant interactions between the plant and other life-forms forms that must be evaluated in the impact analysis.

24 The Biology of the Plant Species Typically such a document includes the following: Taxonomic description Consumption and uses of the crop plant Regional/national breeding, seed production, and agronomic practices Reproductive biology of the crop plant, including details on pollination, mechanisms for dispersal of pollen and seed, and any other means of gene escape Occurrence and viability of intraspecific, interspecific,, and intergeneric hybrids Details on the centres of origin and genetic diversity for the plant species Details on the ploidy of the cultivated crop, its progenitors and any sexually compatible species Distribution and ecology of related species or feral biotypes, including any evidence of weediness Common diseases and pests Potential interactions with other organisms such as pollinators, mycorrhizal fungi, animal browsers, birds, soil microbes and soil insects

25 Novel Trait The environmental risk of releasing a genetically modified plant is not determined by the novelty of the genetic elements used to transform it, but by the novelty of the plant itself. Useful information can be gained from evaluating whether a trait expressed in a transgenic plant is similar to traits already introduced into that plant species. For example, the potential impact of introducing a fungal resistance gene on the persistence of a transgenic plant may be addressed, in part, by evaluating the effect that conventionally bred varieties with the same fungal resistance trait had when they

26 Substantial Equivalence The concept of familiarity is coupled with that of substantial equivalence Substantial equivalence is based on the principle that novel plants can be compared with their non-transformed counterparts that have an established history of safe use The objective is to determine if the novel plant presents any new or greater risks in comparison with its traditional counterpart,, or whether it can be used interchangeably with its traditional counterpart without negatively affecting the environment in which it is grown The goal is not to establish an absolute level of safety,, but rather a relative level of safety, so that there is a reasonable certainty that no undue risk to the environment will result from the cultivation of the novel plant under anticipated conditions of production

27 Ancient Agriculture (Domestication of Wild Species) Modern Agriculture (Traditional Plant Breeding) Modern Agriculture (Genetic Engineering)

28 From a trichological point of view

29 Safety Considerations The goal of environmental risk assessment of genetically modified plants is to identify and evaluate the risks associated with the release and cultivation of these plants in comparison with a counterpart that has a history of safe use. In addition to information on the host organism, and the donor organism, particularly if the donor or other members of its genus normally exhibit characteristics of pathogenicity or environmental toxicology, or have other traits that affect human health, these concerns include: Molecular characterization and stability of genetic modification Gene transfer to related plants Gene transfer to unrelated organisms Weediness potential Secondary and non-target adverse effects Bacillus thuringiensis Vs Bacillus anthracis

30 Molecular characterization and stability of genetic modification Characterization of a transgenic plant at the molecular level is used to provide information about: the composition and integrity of the inserted DNA the number of copies of the inserted DNA the number of sites of insertion and the level of expression of the novel protein(s) ) over time and in different tissues. It is very important that a rigorous molecular characterization of each transgenic plant submitted for review be completed, it is equally important to recognize the limitations of this approach in predicting the safety of a novel food or plant. On an individual event basis

31 Gene Transfer to Related Plants Introgression from one plant to another is only significant if the two plants are sexually compatible and if their hybrid offspring are viable. In order to assess potential environmental risks associated with outcrossing from transgenic plants, the reproductive biology of the plant and distribution of sexually compatible relatives must be known,, and the impact of the introduced trait, should it be introgressed into other plant species,, must be understood. Bt cotton Vs wild cotton

32 Gene Transfer to Unrelated Organisms CaMV 35S promoter and safety of Cauliflower Horizontal gene transfer (HGT) is the non-sexual exchange of genetic material between organisms belonging to the same or different species The possibility of HGT between plants and bacteria in either the soil or gut - particularly as this relates to the possible transfer of genes encoding antibiotic resistance - has been seen as a hazard associated with genetically engineered plants HGT is a natural process of cross-species species gene movement responsible for effecting genetic change, and that genes introduced into transgenic plants are no more likely to be transferred to other organisms than are other plant genes

33 Weediness Potential a measure of a plant s s ability to successfully colonize an ecosystem, especially when it may also lead to the displacement of other species To evaluate if a transgenic plant has altered weediness potential in comparison with its conventional counterpart, the following may be examined: e.g.: the Congress weed (Parthenium) Dissemination of seed Dormancy of seed Germination of seed/survival Competitiveness Agronomic characteristics time to maturity, disease and pest resistance Stress tolerance

34 Secondary and Non-Target Adverse Effects Environmental risk assessment must consider the unintended consequences of the environmental release of a transgenic plant, particularly as this may impact on existing agricultural practices and the agro-ecosystem A non-target organism is any plant, animal or microorganism that is unintentionally impacted by the novel, or transgenic, plant.

35 Risk assessment, the OECD guidelines According to the Organisation for Economic Co-operation operation and Development (OECD): Safety in biotechnology is achieved by the appropriate application of risk/safety analysis and risk management. Risk/safety analysis comprises hazard identification and, if a hazard has been identified, risk assessment. Risk/safety analysis is based on the characteristics of the organism, the introduced trait, the environment into which the organism is introduced, the interaction between these, and the intended application. Risk/safety analysis is conducted prior to an intended action and is typically a routine component of research, development and testing of new organisms, whether performed in a laboratory or a field setting. Risk/safety analysis is a scientific procedure which does not imply or exclude regulatory oversight or imply that every case will necessarily be reviewed by a national or other authority. In short, risk assessment of genetically engineered plants should be based on sound science and should be applied on a case-by by-case basis.

36 Case study Bt corn Mon 810

37 Host Organism Genetic and Phenotypic Variability The assessment of the interaction of MON 810 with the environment has included studies on: susceptibility to insects and diseases; survival capacity (volunteers); seed multiplication capacity (yields); Cry1Ab protein expression in leaves and grain; seed composition analysis; safety for birds; and safety for mammals No significant differences have been observed between MON810 and other maize varieties apart from protection from certain lepidopteran insects

38 Host Organism No differences in seed or plant maturity have been observed A comparison of a non-transgenic hybrid with the same hybrid in which one parent was a backcross derived MON 810 line showed no significant difference between these hybrids in yield No differences in agronomic quality, disease, or insect susceptibility other than European corn borer control were detected between MON 810 and non-transgenic plants.

39 Donor organism MON 810 contains DNA sequences derived from the following donor organisms: Bacillus thuringiensis cry1ab gene Cauliflower mosaic virus (CaMV( CaMV) ) enhanced 35S promoter with the duplicated enhancer region The intron from the maize hsp70 gene for an increased level of transcription The 3' untranslated region of the nopaline synthase gene (NOS 3') from the Ti plasmid of Agrobacterium tumefaciens. None of the inserted sequences are known to have any pathogenic or harmful characteristics.

40 Transformation Method Particle bombardment Genes encoding for glyphosate tolerance (CP4 EPSPS and gox genes used for selection but not present in MON810 Co-transformation of pv-zmbko7 (contains the cry1ab gene) and pv-zmgtlo (containing the CP4 EPSPS and gox genes) nptii for bacterial selection, origin of replication from puc Plant expression vector cry1ab gene under the control of the enhanced CaMV 35S promoter (0.6 kb) 0.8 kb intron from the maize hsp70 located between the the promoter and the cry1ab gene Intron followed by 3.47 kb cryiab gene modified to increase the levels of expression in maize 0.27 kb nopaline synthase 3' nontranslated sequence, NOS 3

41 Molecular Characterisation Southern Blot Analysis Probes homologous to the cryiab,, CP4 EPSPS, gox, nptii,, and ori-puc genetic regions the insert number (number of integration sites within the maize genome), and the copy number and integrity of each gene was examined Insert Number (cryiab( cryiab) one MON 810 does not contain the CP4 EPSPS and gox gene No backbone integration

42 Genetic stability of introduced trait Segregation Analysis of MON 810 a single active insert segregating according to Mendelian genetics Stability of this insertion demonstrated through seven generations of crossing Southern blot analysis demonstrated that the cry1ab insertion was stable through three generations

43 Expression of transgene Field trials of MON 810 were conducted in major maize growing regions of US, Italy, and France (representing a variety of environmental conditions) The identity and levels of expression of the Cry1Ab protein in plant tissue samples collected from these sites determined by ELISA The Cry1Ab protein levels in maize line MON 810 were low relative to total protein in maize leaf, grain and whole plant tissues, but sufficient to provide season long control of ECB CP4 EPSPS and GOX protein were not detectable in maize leaf, grain and whole plant tissue MON 810 was shown by Western blot analysis to contain a Cry1Ab trypsin-resistant resistant core protein that was equivalent to the E. coli-produced Cry1Ab trypsin-resistant resistant core protein used for safety assessment studies. The equivalence established by this study served as the justification for using the safety data generated with E. coli-produced Cry1Ab trypsin-resistant resistant core protein to support the safety of the Cry1Ab trypsin-resistant resistant core protein expressed in this insect protected maize line

44 Gene transfer to related plants For gene flow to occur via normal sexual transmission, certain conditions must exist: the two parents must be sexually compatible their fecundity must coincide a suitable pollen vector must be present and capable of transferring pollen between the two parents and resulting progeny must be fertile and ecologically fit for the environment in which they are situated Maize easily crosses with teosinte,, but teosinte is not present in the United States Outcrossing with Tripsacum species is not known to occur in the wild and it is only with extreme difficulty that maize can be crossed with Tripsacum No cases of gene flow between maize and its wild relatives are known in either Canada or the United States

45 Gene transfer to related plants Outcrossing to Cultivated Zea Varieties Gene exchange between varieties of cultivated and genetically modified maize will be similar to that which occurs naturally between cultivated maize varieties. Wind-borne pollen will move between plants within the same field and to maize plants in nearby fields. The transfer of the transgenic trait to other cultivated maize will not impart any additional safety concerns to those already identified and addressed for the original transgenic maize The environmental impact of the novel trait in cultivated maize will have been considered during the environmental risk assessment of the genetically modified line and transferring the trait, either intentionally or unintentionally, to other maize varieties will not result in additional or new risks

46 Weediness potential Dissemination of seed - Maize cannot survive without human assistance due to past selection in its evolution and consequently, seed dispersal of individual kernels naturally does not occur because of the structure of the ears of maize. The introduced trait, insect-protection, had no influence on reproductive morphology and hence no changes in seed dissemination would be expected there are no differences in vegetative vigour or adaptation to environmental stress factors including drought, heat, and frost between MON 810 and the parental control or other maize lines of similar genetic background

47 Secondary and Non-Target Adverse Effects Plant pest potential - A plant may be considered a pest but not a weed. For example, a plant that produces an allelopathic substance may be considered a pest if the toxin produced has an undesirable environmental effect. Transgenic plants expressing novel toxins or potential allergens must be assessed accordingly There is no evidence to indicate that MON 810 has altered plant pest potential in comparison with its non-transformed counterpart.

48 Effect on non-target organism The insecticidally active trypsin-resistant resistant core protein (HD- 1) produced in MON810, is identical to the respective full length and trypsin-resistant resistant core Cry1Ab proteins contained in commercial microbial formulations Cry1Ab protein is extremely selective for the lepidopteran insects bind specifically to receptors on the mid-gut of lepidopteran insects and have no deleterious effect on beneficial/non-target insects Cry1Ab-expressing maize had neither a direct nor an indirect effect on the beneficial arthropod species studied. Insect-protected maize had no effect on spiders, coccinellid, chrysopid which are also known to be important predators of the European corn borer as well as of other economically important pests of maize.

49 Effect on non-target organism Dietary feeding trials of key non-target indicator species Honey bee larvae and adults Green lacewing Parasitic Hymenopteran Ladybird beetles Daphnia Earthworm Collembola Northern Bobwhite Quail

50 Resistance Management The potential development of insect resistance to Bt,, as a consequence of large-scale commercial plantings of Bt crops, is also a concern to farmers high dose/refuge strategy Exposing a portion of the pest population to Bt plants with an extremely high concentration of toxin [25 times the amount needed to kill 99% of the susceptible insects], while maintaining another part of the population in a refuge where the pests do not encounter any Bt toxin

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52 Best Management Principles for Bt Crops A specific Insect Resistance Management plan is necessary to ensure long-term resistance management. elements of the IRM plan are: high dose structured refuge susceptible pest biology and ecology data impact on secondary pests impact on pests affecting multiple Bt crops cross-resistance resistance potential resistance mechanisms monitoring/surveillance and remedial action

53 Best Management Principles for Bt Crops A high dose/structured refuge strategy is necessary to ensure long-term resistance management. Grower education, adoption, and compliance are essential to the implementation and success of a long-term resistance management strategy. Bt crops are to be used as part of an integrated pest management program to enhance pest management goals. Coordinated annual performance monitoring and surveillance is necessary to detect or follow resistance development. Immediate and coordinated remedial action for suspected and confirmed incidents of resistance is necessary. IRM strategies should be tailored to address specific regional resistance management concerns, as appropriate. Deployment of IPM tactics with different modes of action, including conventional pesticides, Bt toxins expressed in crops with different modes of action, biological control methods, and other control methods, is essential for sustainable pest management goals Continued resistance management research should be conducted to evaluate the effectiveness of, and be used to modify, as necessary, IRM strategies for Bt crops

54 Think it over!!! Popular assumption: Whatever we get in nature is good Fact: Whatever we get in nature is neutral. Viewing it as good or bad depends upon make-up of our mind and popular opinion or the conditioned behaviour

55 Oliver Goldsmith Oliver Goldsmith s s famous lines in his poem the deserted village 55: But a bold peasantry, their country's pride, 56: When once destroy'd,, can never be supplied.

56 "Whoever could make two ears of corn, or two blades of grass grow upon a spot of ground where only one grew before would deserve better of Mankind, and do more essential service to his country, than the whole race of politicians put together." - The King of Brobdingnag,, Gulliver's Travels by Jonathan Swift, 1727.