Presentation on theme: "The GM debate "The old saying that vox populi;vox dei as every philosopher knows cannot be trusted in science" DARWIN 1876. The science is quite clear."— Presentation transcript:
The GM debate "The old saying that vox populi;vox dei as every philosopher knows cannot be trusted in science" DARWIN 1876. The science is quite clear concerning the crops on trial in the UK. The debate is really about values, feelings and beliefs. Assessments will always be made on a case-by-case basis. Approval of one GM crop does not provide blanket approval of all. In risk assessment, relative risk is crucial. Comparison is made with what we do now and is accepted as safe from a history of experience. There is no absolute safety for anything in human life but we act as though there is. Who regards their motor car as unsafe?
Current plant breeding We have all eaten genetically engineered food all of our lives. Conventional plant breeding A. Uses natural mutants: that is natural genetic engineering. Why wait for nature? If we replicate by GM what nature has already done is there really a difference? B. Induced mutation. Radiation used on 2252 crop samples to speed up mutation rates enormously (IAEA Vienna 1999). Estimates suggest radiation modifies up to 10% genome. 80% worlds wheat has genes from radiation induced mutagenesis. C. Genes obtained from weeds for pest resistance. In cereals hardly any species barrier exists. D. In comparison GM is much more targeted, quicker and more accurate. We share 50% of our genes with a banana.
Gene flow. To the same crop A. Figure from detailed studies by Roush and others in Australia. Maximum spread, 0.07%. B. Distance of spread up to 3 kilometres probably by bees. C. Varietal purity, seed certification and/or product segregation not a problem which only guarantee 99.5% purity. D. Organic regulations- EC level for non-GM description is 0.9% GM in sample.
E. Gene stacking of Herbicide Tolerance (HT) in volunteer hybrids have been reported in Canada arising from two GM rape and one conventional HT rape grown in close proximity. Any mixture of cultivars of one crop grown in close proximity will give rise to similar problems. Cross resistance to herbicides is well known. Problems are not unique to GM crops and more of a nuisance than a problem. F. All current GM crops and equivalents do not survive in fallow fields.
Introgression A. Two parents must be equally compatible. B. Fecundity must coincide C. Suitable pollen vector must be present D. Resulting progeny must be fertile and ecologically fit. With current herbicide tolerant (HT) and pest resistant GM crops- introgression at a low rate can occur from oil seed rape into several closely related weeds like wild turnip or sugar beet into sea beet. Should we be concerned? A. Current introgression hybrids do not survive (lack fitness). B. HT not considered to be of genetic value outside farm environment and thus quickly lost.
C. Weeds are a sea of natural mutant variants; HT already present in weed populations as indicated by speed of resistance development (3-20 years). (Weeds worldwide have resistance to 15 different herbicides). Pest resistance is already present in weeds and in most plants, as indicated by rapid spread of exotics transferred from their normal environment when pest pressure is removed. Thus present GM traits are not novel. D. No evidence that genes inserted by GM transfer more vigorously to weeds. E. At least 3 crops marketed with resistance to herbicides from conventional breeding-rape resistant to atrazine, maize resistant to imidazolinone, soybean resistant to sulfonylurea. No known problems have emerged with their use.
F. Traits which could increase weediness potential are those that increase tolerance to drought, cold or dormancy. However crops with these traits are already currently used and they do not currently lead to increased weed problems. In the UK an estimated 1000 crop cultivars are introduced every year from conventional breeding mainly for pest resistance but other unique traits are probably present but untested. G. Will there be impacts on biodiversity? Currently the HT trait has been introduced into many different lines of rape.
Avoiding Gene flow. Four methods at least are available- A. Isolation of crop B. Use of crop that produces sterile flowers C. Use of terminator technology- production of sterile seed. D. Transformation via the chloroplast genome.
Advantages of chloroplast GM compared to nuclear GM. 1. Chloroplast traits in most crops are maternally inherited- pollen does not contain chloroplasts. 2. Much higher expression achievable-when used with Bt protein 100% kill of target insects thus no resistance development. 3. Single site for incorporation of gene. Incorporation uses homologous recombination. 4. No gene silencing. 5. Multigene constructs and whole operons expressed in chloroplasts. 6. Systems for ready transformation present. Potato and tomato transformed. 7. Cholera vaccine and biologically active somatotrophin expressed in chloroplasts. 8. Marker gene removal method present using CRE-lox. 9. However seed spread still possible.
Benefits to the use of HT crops "Had we not originally gone contrary to the laws of nature by plowing the land we would have avoided the problems as well as the time consuming efforts to solve them. We would have missed all of the erosion, the sour soils, the mounting floods, the lowering water table, the vanishing wildlife, the compact and impervious soil surface" Ed Faulkner, (1943) Plowmans Folly. All of Faulkner's claims have been established by measurement and indicate the superiority of no-till agriculture over organic and conventional ploughing technologies. Ploughing is the most damaging soil treatment and no-till agriculture most easily introduced with HT crops to avoid weed problems. Organic has no choice but to plough to mineralise and form nitrate and bury difficult weeds.
No-till benefits compared to till 1. Farm fossil fuel use 1/3 rd. 2. Erosion reduced to 5% ploughed field. Soil nutrition, structure and drainage vastly better. 3. Pest predators and large earthworms up 6 fold. 4. Birds and nest increase anywhere from 3-100 fold. Time requirements for young bird feeding reduced five fold. 5. Preventing sediment losses improves aquatic habitat. Run off greatly diminished. Herbicides no longer detectable in soil drainage. Nitrate 1/20 th. 6. Soil moisture better balanced during drought. 7. Soil carbon accumulates- released on ploughing when introduction of oxygen breaks down organic material. 1/3 rd global warming potential of organic. 8. Mimicks seasonal change in meadow and prairie.
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