Transcript Slide 1

Research Scientists
Advocating the Use of Bt Corn
Dr. Hilda Castillo
Dr. Carol Tolley
University of Gattica
Historical Plant Breeding Programs
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Incorporation of genes
Crossbreeding
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Wild species into
common cultivars
Introgression
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Time consideration
Cost
Effectiveness
From The National Agricultural Biotechnology Council Report 2001
Plant Breeding Goals
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Genetic modification to gain
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Higher yields
Nutritional values
Environmentally compatible production
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Reduced pesticide use
Herbicide tolerance
Reduced energy use
Longer shelf life
Biotechnology and Genetic
Engineering
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Genetic modification
Built in protection from pests
Selection of single known gene
Precise
Cost effective
Bacillus thuringiensis
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Naturally occurring bacteria
Known biopesticide
Used for 50+ years
Predictable effects
Delivery of new genes - Vector
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Ti plasmid
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Agrobacterium tumefaciens
Remove DNA
Insert Bt gene
Introduce in plant
Picture from Strickberger, (1991) Genetics
Benefit of Bt corn
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Reliable control of target pest
Reduced crop loss
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Reduced pesticide use
Increased yields
Healthier
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Estimated $1.2 billion/year in U.S.
Reduced fumonisin mycotoxin levels
Utilization of marginal land
U.S. Regulatory Policy
EPA – regulates plants with pest
protection
 USDA – imposes regulations during
development
 FDA – approves new food safety
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In Conclusion
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Pest population reduction affects the overall
biological community whether using:
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Bt plants, biological control agents, resistant plants,
insecticides, cultivation techniques, or any other method to
control pest
As with any technology, Bt plants were incorporated
without complete understanding of their effects but
with a certainty that the risks would be fewer than
current technology and that the benefits of GE crops
would be greater.
Shelton, A.M. et al. (2002). Economic, Ecological, Food Safety, and Social Consequences of the Development of
Bt Transgenic Plants. Annu. Rev. Entomol. 47:845-81
Extra Slides
Bacillus thuringiensis
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Isolated in Japan in 1915
Insecticide commercialized in 1930
1995 – 182 Bt products marketed
Known entity
Several strains used in Bt corn
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Cry1, Cry 2, Cry 3, Cry9
Corn Fungi
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Naturally occurring
fungi
Edible and non-edible
Point of entry
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Through roots
Areas of water collection
damage to ears via
Lepidoptera feeding
Fusarium moniliforme
(and other species)
Mycotoxins
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Fusarium moniliforme
Mycotoxins produced
– Adverse health effect in livestock
– Possible carcinogen
– Occurrence
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High in Raw Corn
Less in processed corn
Very reduced in Bt corn
What Can You Get
From a Bushel of Corn?
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A typical bushel of corn weighs 56 pounds and
contains approximately 72,800 kernels. Most of
the weight is the starch, oil, protein and fiber,
with some natural moisture.
What can be extracted from a bushel of corn?
 32 Pounds of Starch
OR
33 Pounds of Sweetener
OR
2.5 Gallons of Fuel Ethanol
AND
11.4 Pounds of 20% Gluten Feed
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3 Pounds of 60% Gluten Meal
AND
1.6 Pounds of Corn Oil
©Copyright 2001 Ohio Corn Marketing Program.
Wild Relatives
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From genetic origin
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Mexico
Central America
South America
Potential outcrossing
Influence continued
evolution
Land Races
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Grown and selected for
generations
Found world wide
May have developed
resistance to specific
pests
Selected for specific
growing regions
Potential outcrossing
with cultivars
Problems
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Loss of genetic variability
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Through outcrossing
Loss of habitat of wild species
Planting instead of land races
Influence on potential evolution
Outcrossing
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Gene capture and expression
Wild, weedy relatives
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Mexico
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Teosinte
– Effort to reduce outcrossing
Weed potential
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10 year study
Britain
Rape, corn, sugar beet
Conclusion – not invasive
Horizontal gene transfer
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Through
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Crop residue
Pollen
Root exudates
Dependent on soil characteristics
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1.6 to 22 days
As long as 46 days
As stable DNA – months to years
Soil organisms
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EPA evaluated
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Birds
Fish
Honeybees
Ladybugs
Parasitic wasps
Lacewings
Springtails
Aquatic invertebrates
Pollen
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Bt is expressed
Heavy
Wind dispersed
Limited movement
Agricultural GM Crops
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Widely used
Accepted
No proven detrimental
effects
Increased yields
without increased
pesticide use
From: Biotechnology Industry Organization http://www.bio.org/er/agriculture.asp