پاورپوینت Crop Biotechnology
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Crop Biotechnology
How much worldwide?
GE crops accounted for slightly more than 22% of the worldwide acreage of land under cultivation. (22% > twice the size of the UK).
Six countries (out of approximately 190) account for 99% of the worldwide acreage of GE crops.
U.S.: 63% (cotton, corn, soybeans, canola)
Argentina: 21% (cotton, corn, soybeans)
Canada: 6% (canola, corn, soybeans)
Brazil: 4% (soybeans)
China: 4% (cotton)
South Africa: 1% (cotton, corn, soybeans)
Three Main Applications
Roundup Ready Soybeans
Bt Corn
Bt Cotton
(Roundup Ready Wheat was nearing commercialization until Monsanto ceased development.)
U. S. Acreage
Roundup Ready Soybeans
Roundup is a broad spectrum herbicide whose active ingredient is glyphosate.
Roundup is produced by Monsanto, although the patent on it recently expired. Applying glyphosate to a non-resistant plant interrupts the ability of an enzyme (EPSP synthase) to catalyze the production of amino acids, causing the plant to suffer from amino acid starvation and cell death. Glyphosate has minimal effect on human or animal health and degrades quickly in the environment.
Roundup Ready Soybeans
RR soybeans were made roundup ready by the introduction of a resistance gene from a strain of Agrobacterium using particle bombardment. This gene produces a slightly different form of the enzyme which is not interrupted by glyphosate.
Rationale: Simplifies weed control program. Roundup is a highly effective herbicide and gives farmers more flexibility in timing herbicide treatments.
Bt Corn
Bacillus thuringiensis (Bt) is a common soil bacterium which produces a crystalline toxin, primarily effective against Lepidoptera (moth and butterfly species). When the toxin is eaten by a susceptible insect, the insect’s digestive system breaks down the proteins into smaller polypeptides, which then become active and bind with molecules in the midgut of the insect, where they cause pores to develop which upset the osmosis between the gut and the rest of the insect. The insect stops feeding, and dies within a few days.
Organic farmers use spray formulations of Bt, which is the only organic pesticide. Compared to most pesticides, which are neurotoxins and extremely harmful to anything with a central nervous system, Bt is comparatively specific and safe.
Bt Corn
Rationale: The European Corn Borer is a major corn pest in the U. S., but synthetic insecticides and spray Bt are not very effective against it due to the fact that the Corn Borer lives underground and burrows into the corn where the insecticides don’t reach. Annual losses to the ECB were sometimes as high as 300 million bushels per year. Bt Corn produces Bt toxin in every one of its cells continuously, and is quite effective in reducing yield losses.
Bt Cotton
Bt toxin is also effective against tobacco budworm, cotton bollworm, and pink bollworm, three major cotton pests.
Cotton is the crop which receives the heaviest pesticide applications, and those posts are ones that farmers were spraying for.
A Taxonomy of the Ethical Issues
Consumer Issues
Environmental Issues
Socioeconomic Issues
Consumer Issues
Unintended increase in antinutrients or decrease in nutrients
Unintended introduction of allergens
Do not presently have a reliable test for whether or not a novel protein is an likely to be an allergen
90% of known food allergies are due to specific proteins in 8 foods: peanuts, tree nuts, milk, eggs, soybeans, shell fish, fish, and wheat
Pioneer Hi-Bred International developed a line of soybeans that higher efficiency and nutritional content for animal feed by moving a gene from the Brazil nut into the soybean. The soybean did produce an allergic reaction in people who were allergic to Brazil nuts. Pioneer shut down the project before it ever reached the market.
Unintended introduction of toxins
Consumer Issues – The Pusztai Affair
August 1998: Arpad Pusztai, a well-established researcher at the Rowett Research Institute in Scotland, discussed preliminary data during a television interview
Said that the data suggested that rats fed 2 kinds of potatoes genetically engineered to produce snowdrop lectin (a potential pesticide) exhibited stunted growth and suppressed immune function compared to controls fed non-GM potatoes with or without added snowdrop lectin.
Consumer Issues – The Pusztai Affair
He says that two days after the interview was aired, “When I got to my laboratory I found the computer sealed, the desks locked and all my papers taken away.” (Rampton and Stauber 2001)
He was threatened with loss of pension if he made any public statements about the research.
June 1999: The UK Royal Society concluded that “Because of the poor experimental design, it is simply not possible to be sure about the causes of the small effects obtained in the study.”
Consumer Issues – The Pusztai Affair
August 1999: Pusztai’s response in the Lancet: “… not all the facts were in the possession of the Royal Society. Thus, it is difficult to understand how they could deduce that the GM-potato experiments were badly designed and poorly carried out from an internal report by Pusztai that contained no such details. The Royal Society had never considered, or even asked for, a copy of the original research proposal of 1995. This omission was further compounded by the Royal Society s unwillingness to take up Pusztai s offer of full cooperation. Moreover, as crucial details of the histological findings were never divulged to them, it is more than perplexing that the Royal Society s unnamed experts were so emphatic in their condemnation of the GM-potato experiments.”
Consumer Issues – The Pusztai Affair
October 1999: Pusztai’s article was published in The Lancet, subject to 6 peer reviewers, twice the usual number. 4 recommended publication, 1 thought it had problems but recommended publication anyway, and 1 recommended rejection.
Environmental Issues
Engineered crop may become a weed and disrupt neighboring ecosystems
Gene may move from into a relative, increase its weediness, and disrupt neighboring ecosystems
Corn, soybeans, and cotton have no relatives in the U.S.
Canola, wheat, and sunflowers do have relatives in the U.S. (Allison Snow found that wild sunflowers modified with the Bt gene produced fifty-five percent more seeds than unmodified wild sunflowers. Pioneer and Dow exercised their patent rights and prevented her from doing follow-up research.
Hard to predict how a gene transfer would affect fitness of relatives.
Environmental Impact
Increased Negative Impact of Herbicide Use
Rat LD50 value (indicator of acute mammalian toxicity)
Environmental indicator is the sum of LD50 doses per acre for all herbicides applied
Herbicide Use with RR Soybeans
Slight reduction in yield with RR soybeans (2%)
Dramatic decrease in toxic doses of herbicide
Bt Corn
The National Center for Food and Agricultural Policy estimates that Bt corn saved 66 million bushels of corn in 1999, the yield of about 500,000 acres.
The use of Bt corn does not significantly reduce synthetic pesticide use (because farmers weren’t spraying for the ECB); rather, it supplements it.
Environmental Issues – The Chapela Affair
September 2001: David Quist and Ignatio Chapela published in Nature that transgenic DNA had moved into maize landraces in the mountains of Oaxaca, Mexico.
“This region is part of the Mesoamerican center of origin for maize (Zea mays L.), and the genetic diversity that is maintained in open-pollinated landraces recognized as an important genetic resource of great cultural value. The presence of transgenes in landraces was significant because transgenic maize has never been approved for cultivation in Mexico.” (Snow et al. 2005)
Environmental Issues – The Chapela Affair
Chapela was an outspoken opponent of a five-year deal struck in 1998 that gave biotech giant Novartis privileged access to UC plant research in exchange for $25 million.
Despite a positive vote from his department, a unanimous ratification by an ad hoc tenure committee, and recommendation by the chair and college Dean, the campus Budget Committee denied tenure in June 2003.
A Michigan State University review concluded that there was “little doubt” that the Novartis deal had played a role in the tenure decision.
Chapela was later granted tenure when a new chancellor arrived at Berkeley.
Environmental Issues – The Chapela Affair
Commission for Environmental Cooperation of North America (2004): “Transgenes have entered some landraces of maize in Mexico. This finding was confirmed by scientific studies sponsored by the Mexican government. However, no peer-reviewed summaries of this work have been published and information released to the public has been vague. In any event, there is no doubt that transgenes will spread in Mexican maize, and that they are present now.”
Snow et al. (2005) conclude: “No transgenic sequences were detected with highly sensitive PCR-based markers, appropriate positive and negative controls, and duplicate samples for DNA extraction. We conclude that transgenic maize seeds were absent or extremely rare in the sampled fields.”
Bt Cotton
The National Center for Food and Agricultural Policy estimates that Bt cotton has reduced synthetic insecticide use by 2.7 million pounds, and resulted in 15 million fewer pesticide applications. Pesticide-related hospital visits for farm workers on farms that grow Bt cotton are substantially reduced in number.
Environmental Issues
Effects on non-target organisms
Direct: John Losey at Cornell reported that pollen from Bt corn kills monarch butterfly larvae. The main food source for the larvae is milkweed plants on the edge of corn fields.
Indirect: in some areas, more effective elimination of weeds in Roundup Ready fields has reduced ecological biodiversity in the surrounding area
Socioeconomic Issues
Increases in yield can makes prices drop, not always a good thing.
Pests will become resistant to Bt, thus undermining its usefulness. (According to Scott (2005), industry pressed for as small a refuge as possible, while scientists argued that 10% was necessary to avoid resistance; resulting in a 4% refuge.)
GE crops contaminate organic farmers fields.
Contamination can also jeopardize markets.
StarLink (2000): In 2000, the USDA agreed to spend $20 million to buy up contaminated corn
Prodigene and pharmaceutical production (2002)
Roundup Ready Wheat was going to be commercialized in 2005. An Iowa State agricultural economist predicted that “American spring wheat producers could lose 30 to 50 percent of their export market” and that the price of U.S. wheat could drop by as much as 33%.” Monsanto finally gave up developing RR Wheat.
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