Ecology of Transgenic Crops

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Ecology of Transgenic Crops

• ??? (Ayo)
• ???? ??????? ??
• http//mail.nutn.edu.tw/hycheng

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?????????????????????
2003/10/3 ????
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No ????
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Ecology of Transgenic Crops

• Genetically engineered plants might generate weed
  problems and affect non-target organisms, but
  measuring the risk is difficult.
• ???? Marvier, M. (2001) Ecology of transgenic
  crops. American Scientist 89(2)160-167.

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???????

• On May 20, 1999, a short article in Nature called
  attention to a potential ecological problem with
  a genetically engineered, or transgenic, crop.
• Losey and his colleagues at Cornell Univ.
  reported that a variety of transgenic corn could
  kill the larvae of monarch butterflies.

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Fig. 1. Monarch caterpillars feed on a milkweed
leaf dusted with pollen from corn that was
genetically engineered to resist pest. Plant
breeders can transfer a gene from a bacterium
called Bacillus thuringiensis into corn, which
causes it to produce an insecticidal compound,
commonly called Bt toxin.
Losey and his colleagues found that only 56 of
the monarch larvae survived when fed milkweed
plants coated with transgenic corn pollen,
whereas 100 of larvae survived when the plants
were coated with non-transgenic corn pollen.
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??? vs. ???

• Opponents of transgenic crops help up the report
  as evidence of the potentially devastating
  environmental impact.
• Proponents largely dismissed this
  laboratory-based research as unrepresentative of
  conditions on real farms.

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???????

• Genetic engineering makes it possible to transfer
  genes from virtually any species animal,
  bacteria, plant or virus into almost any other
  species, no matter how unrelated the two species
  might be.
• ??????? ?????????????,???????(Monsanto ??)?

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???????????

• ?????????????????,?????(???????)?
• ???????????(allergens)?????(carcinogens)??????,??
  ??pests,?non-target species???,disruption of
  ecosystem processes?
• ??,????????,????????????

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??????????!

• In 1996,??????????????????430????
• In 1998,??????? 6,950????
• With such rapidly in creasing use of transgenic
  crops, scientists and society must weigh whether
  the potential benefits outweigh the potential
  risks.

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????,more than ???

• Do transgenic crops pose different risks from
  those common to crops created through traditional
  methods of plant breeding?
• Genetic engineering can create many more
  combinations of genes and new traits than can
  traditional breeding.
• This greatly enhanced novelty diminishes anyones
  ability to predict the safety of a transgenic
  organism on the basis of past experience.

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DDT???

• Scientists and manufactures considered DDT
  totally risk-free when first marketed in the late
  1940s, and data that documented ill effects took
  nearly 20 years to surface.
• Similarly, major problems might result from
  transgenic crops over time.

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Fig. 2. DDT gets praise from an advertisement in
the June 30, 1947, issue of Time.
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DDT ????

• DDT Dichloro-Dipheny-Trichloroethane
• ??-??-????
• DDT??????
• ???????1874?
• ?1939?,????????? (Paul Muller)
• ?????????1940?????
• 1948? Paul Muller ???1939??????????????

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DDT ????

• ?????,????????????,?1959?????,????8,000???
• 1959??,????????1972???????(???????,??)
• ???30?,????????13?5???DDT,????????

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DDT??????

• 1947??,DDT??????????
• 1957?,???????DDT?????,???????
• 1962?,Rachel Carson ?Silent Spring
• 1963?5?,????????????DDT????????
• 1967?,DDT??????????
• 1972?6?14?,???9,312?(??125?????)???,??350???????,?
  ?????????,?????

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Insect-resistant transgenic crops

• Creating new weeds
• Troubles for non-targets
• What is significantly safe?
• Setting standards for sampling
• Dealing with uncertainty

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Creating new weeds

• The release of organisms with novel phenotypes
  bears similarities to the introduction of
  non-native species.
• ???????,?????,??????(weeds),????????????
• ?????,???????????,?????
• Hybridization between a transgenic crop and a
  related non-crop plant can spread novel traits to
  additional species.

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Fig. 3. Purple loosestrife ranks as one of the
most economically costly and environmentally
destructive examples of non-native species.
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Fig. 4. Invertebrate herbivores can limit plant
reproduction. This graph represents the pooled
results from many experiment on the impacts of
invertebrate herbivores on plant-reproductive
performance.
?????,production of flowerers, fruits or seeds
??,?????25??
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Troubles for non-targets

• ??
• a plant that is toxic to Colorado potato beetles
  could conceivably also be toxic to non-pest
  beetles or to beetles that actually benefit
  farmers, including ladybird beetles.
• Losey and his colleagues studied the effects of
  pollen produced by transgenic corn that resists
  lepodopteran pests.

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?Bt corn corn
????
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Fig. 5. This corn releases an insecticidal
compound (red) through its roots into the soil.
That compound can remain insecticidal for 230
days or more and could impact populations of soil
organisms. In addition, pollen from Bt corn
(blue) can travel as far as 60 meters, where it
coats the surface of non-crop plants. Non-target
insects, including monarch butterfly larvae,
consume some of the windblown corn pollen.
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What is significantly safe?

• Transgenic crops that produce insect toxins must
  undergo two separate reviews of environmental
  safety before they can be sold commercially in
  the U.S.
• 1. EPA reviews laboratory studies assessing a
  crops effects on particular non-target
  organisms, including pollinators, predatory
  insects and, often, soil invertebrates.
• 2. Sufficient field data regarding a crops
  performance and safety.

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?????

• As of July 2000, the US ???????50????????14???????
  ???,?????Bt toxin?
• ?????????Bt toxin??????????????????

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?????!

• ???????
• ??97-012-01p
• ??A variety of Bt cotton
• In experiments designed to test this transgenic
  crops impact on soil invertebrates,
  investigators placed four replicate batches of
  earthworms with 10 worms per batch in soil that
  included ground leaves from either transgenic or
  non-transgenic cotton.
• ??14??

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Fig. 6. The batches of earthworms exposed to Bt
cotton increased in weight on average by 49 (?).
The earthworms exposed to non-transgenic cotton
increased in weight on average by 78.5 (?).

• ????????29.5,??????????????
• ???????????????????
• ??,???????14?,????????

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Setting standards for sampling

• ??
• ??94-257-01p
• ??a Bt potato
• ????????????????????,??????????????????????,?????
  ?

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• ??
• The Swiss Federal Research Station found that
  green lacewings, which are beneficial predatory
  insects, experienced 62 mortality when fed a
  diet of pests reared on Bt corn, but only 37
  mortality when fed pests reared on non-transgenic
  corn.
• ???200?? per treatment.
• ????????? over the entire life span????

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A scientific advisory panel

• Met in December 1999 to review the EPA guidelines
  and recommended the following
• The agency (EPA) should consider how the data
  will be used and establish an acceptable level of
  statistical power. Based on these decisions,
  appropriate tests and sample sizes can be
  determined.
• http//www.epa.gov/scipoly/sap/1999/index.htm

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Dealing with uncertainty

• Risk analysis should reveal how the public good
  might suffer if new technologies backfire.
• We could assume that a transgenic product is
  unsafe until the manufacturer demonstrates its
  safety.
• Further exploration
• http//www.americanscientist.org/articles/01articl
  es/marvier.html

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?????? Complexity and Uncertainty

• ??????????????
• CO2?,?????????????,???????????????,??,??????????
• ???????,?????????,?????????????????
• ??????????????????,???????
• ??????????,???140??? ?
• ????????,???????????????

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??????????????????Stiling (1992), p.18?
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• ???? ???????? http//www.pu.edu.tw/humanity
• ?????Ayo ??? http//www1.pu.edu.tw/hycheng