I.
Genetic Engineering
C.
Advantages
1.
Greater agricultural yields
•
More food production per acre could
•
Reduce area needed to support existing population
•
Support future population growth
•
Ex
–
European corn borer destroys 7% of annual corn harvest worldwide
•
Modified corn resistant to ECB could eliminate this loss
•
Extra corn =
7
-
10 mmt (enough to feed 60 million people)
2.
Reduced herbicide use
•
Wheat, corn, soybeans, cotton, sugar beets, alfalfa, etc. engineered to be
resistant to certain herbicides (e.g. Roundup)
•
Farmers can spray crops with less herbicide to kill weeds
•
Ex
–
Soybeans
–
Reduction of pesticide use by 10
-
40% from 1996
-
1997
3.
Reduced pesticide use
•
Crop plants can be engineered for resistance to certain pesticides
•
Ex
–
Insect resistant cotton planted in Alabama led to an 80% reduction in
use of insecticides on cotton from 1996
-
1997
4.
Environmentally beneficial tasks
•
Ex
–
Bacteria engineered to degrade petroleum rapidly can be used to
clean up oil spills
5.
Novel properties
•
Ex
–
Phytase maize (approved in China, 2009)
•
Enzyme makes phosphorus more available to livestock
•
Enhances animal growth, reduces P content of waste (up to 60%)
I.
Genetic Engineering
D.
Drawbacks
•
Opponents emphasize failures of
technology, potential environmental harm
•
“Frankenfood”
•
“Farmageddon”
1.
Harm to native species through competition
•
Transgenic organisms could be superior competitors
•
Potential route to extinction for native species
2.
Damage to beneficial insects
•
Ex
–
Evidence that ladybugs and lacewings suffer (shorter lifespan,
reduced reproduction) when fed aphids and caterpillars that had fed on
GM potatoes and corn, respectively
3.
Damage to soil community
•
Certain GM crops could reduce activity of soil fungi and microbes
•
Negative impact on nutrient cycling in the soil
4.
Release of resistance genes
•
Could potentially lead to “super weeds” if resistance genes get
transferred to weedy species
•
Could harm non
-
GM agriculture, including organic farming through pollen
drift
5.
Upset natural balance of ecosystems
•
Could result from release of GMOs or hybridization between GMOs and
native species
•
Ex
–
GM rape can crossbreed with wild turnips, passing herbicide
tolerance to offspring
•
Potential solution = “
Terminator technology
”
I.
Genetic Engineering
E.
Trends
•
125 GM agricultural plants approved for
growth in the U.S. (ISAAA)
•
Most designed to
1)
Reduce pest damage
2)
Confer resistance to herbicides, pesticides,
viruses, other pathogens
3)
Reduce crop spoilage
Huang et al. 2002
Nature
418
, 678
-
684
Genetically modified crop traits tested
in developed countries, 1987
–
2000
I.
Genetic Engineering
E.
Trends
•
US grows ~48% of GM crops worldwide
(acreage basis)
•
2011: corn 88%, cotton 90%, soy 94% GM
•
Other major growers of GM crops
1)
Brazil
2)
Argentina
3)
India
4)
Canada
5)
China
http://www.ers.usda.gov/Data/BiotechCrops/genengcrops.gif
I.
Genetic Engineering
F.
Examples
1.
Bollgard
®
and Bollgard II
®
Cotton
•
Both strains express insecticidal protein isolated from
Bacillus thuringiensis
(Bt)
•
Safe
–
Farmers can spray with Bt toxin and still label
produce as organic
•
Low toxicity to most non
-
target organism types
•
Low persistence
–
breaks down readily
•
Bollgard II
®
has
stacked traits
to enhance effectiveness
•
Controls bollworms, budworm
•
Year 2000
–
United States averages
•
Cotton fields planted with Bollgard
®
sprayed 3.9
times less often
vs.
conventional fields
•
Reduced total pesticide use by 2.7 million pounds
•
Pest control cost less
-
$15.43/acre
•
Higher production
-
37 pounds/acre
•
Higher profit
-
$39.86/acre
•
Concern
–
Development of resistance by insect pests
I.
Genetic Engineering
F.
Examples
2.
Golden Rice
•
GM rice containing genes that produce beta
-
carotene
•
Can be converted to vitamin A
•
Vitamin A deficiency (VAD) may cause weakened immune
systems, partial to total blindness, and increased chance of
death
•
VAD causes 350,000 cases of blindness and has been
linked to 1 million+ deaths each year
•
Highly controversial
a.
Proponents
•
Reduce incidence of blindness and other VAD related
health disorders
•
1/2 lb of rice/day will keep VAD symptoms away
b.
Opponents
•
Nutritional deficiencies will prevent people from absorbing
beta
-
carotene from rice
•
Concentrations of beta
-
carotene in rice are low, and an
average woman would need to eat 16 lbs of golden rice a
day to get 100% of daily requirement
•
Alternatives like leafy green vegetables or unpolished rice
are better, cheaper sources of vitamin A
•
Western corporations are trying to control rice production
I.
Genetic Engineering
F.
Examples
3.
Future GM crops
•
SmartStax
TM
corn
•
Pest resistant, herbicide tolerant
•
Bt rice
•
Pest resistant
•
High omega
-
3 soybeans
•
Enhanced nutrition
•
RR Sugarbeets*
•
Herbicide tolerant
•
2007: <10% of US
•
2009: 95% of US
•
Blue roses
•
Ornamental
I.
Genetic Engineering
G.
Benefits and Risks
1.
Benefits
•
Accelerated improvement of crop strains
a.
Elevated yields, either per plant or per acre
•
Usually involves inserting growth factor
•
Plants grow larger, faster or both
•
Con
–
Accelerated growth may alter chemical
composition
A汬敲杩敳Ⱐ摩来g瑩t攠灲潢汥浳Ⱐ整e.
戮
A捣敬e牡瑥搠浡瑵牡瑩潮 灲潣p獳
•
Increased yield per acre, more crops per year
•
Con
–
Plants produce different compounds at
different life stages
•
Young plants tend to produce more irritants and
toxins (self defense)
•
Potential to cause digestive or allergic problems
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