Farmers can spray crops with less herbicide to kill weeds Ex

polarbearfellowshipΒιοτεχνολογία

12 Δεκ 2012 (πριν από 4 χρόνια και 4 μήνες)

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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.


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