1. Research Scientists Advocating the Use of Bt Corn
Dr. Hilda Castillo
Dr. Carol Tolley
University of Gattica

2. Historical Plant Breeding Programs
Incorporation of genes
Crossbreeding
Wild species into common cultivars
Introgression
Time consideration
Cost
Effectiveness
From The National Agricultural Biotechnology Council Report 2001

3. Plant Breeding Goals Genetic modification to gain Higher yields
Nutritional values
Environmentally compatible production
Reduced pesticide use
Herbicide tolerance
Reduced energy use
Longer shelf life

4. Biotechnology and Genetic Engineering
Genetic modification
Built in protection from pests
Selection of single known gene
Precise
Cost effective

5. Bacillus thuringiensis
Naturally occurring bacteria
Known biopesticide
Used for 50+ years
Predictable effects

6. Delivery of new genes - Vector
Ti plasmid
Agrobacterium tumefaciens
Remove DNA
Insert Bt gene
Introduce in plant
Picture from Strickberger, (1991) Genetics

7. Benefit of Bt corn Reliable control of target pest Reduced crop loss
Estimated $1.2 billion/year in U.S.
Reduced pesticide use
Increased yields
Healthier
Reduced fumonisin mycotoxin levels
Utilization of marginal land

8. U.S. Regulatory Policy EPA – regulates plants with pest protection
USDA – imposes regulations during development
FDA – approves new food safety

9. Bt Transgenic Plants. Annu. Rev. Entomol. 47:845-81
In Conclusion
Pest population reduction affects the overall biological community whether using:
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

11. Extra Slides

12. Bacillus thuringiensis
Isolated in Japan in 1915
Insecticide commercialized in 1930
1995 – 182 Bt products marketed
Known entity
Several strains used in Bt corn
Cry1, Cry 2, Cry 3, Cry9

13. Corn Fungi Naturally occurring fungi Edible and non-edible
Point of entry
Through roots
Areas of water collection
damage to ears via
Lepidoptera feeding
Fusarium moniliforme (and other species)

14. Mycotoxins Fusarium moniliforme Mycotoxins produced
Adverse health effect in livestock
Possible carcinogen
Occurrence
High in Raw Corn
Less in processed corn
Very reduced in Bt corn

15. What Can You Get From a Bushel of Corn?
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 AND 3 Pounds of 60% Gluten Meal AND 1.6 Pounds of Corn Oil
©Copyright 2001 Ohio Corn Marketing Program.

16. Wild Relatives From genetic origin Potential outcrossing
Mexico
Central America
South America
Potential outcrossing
Influence continued evolution

17. Land Races Grown and selected for generations Found world wide
May have developed resistance to specific pests
Selected for specific growing regions
Potential outcrossing with cultivars

18. Problems Loss of genetic variability Through outcrossing
Loss of habitat of wild species
Planting instead of land races
Influence on potential evolution

19. Outcrossing Gene capture and expression Wild, weedy relatives Mexico
Teosinte
Effort to reduce outcrossing

20. Weed potential 10 year study Britain Rape, corn, sugar beet
Conclusion – not invasive

21. Horizontal gene transfer
Through
Crop residue
Pollen
Root exudates
Dependent on soil characteristics
1.6 to 22 days
As long as 46 days
As stable DNA – months to years

22. Soil organisms EPA evaluated Birds Fish Honeybees Ladybugs
Parasitic wasps
Lacewings
Springtails
Aquatic invertebrates

23. Pollen
Bt is expressed
Heavy
Wind dispersed
Limited movement

24. Agricultural GM Crops Widely used Accepted
No proven detrimental effects
Increased yields without increased pesticide use
From: Biotechnology Industry Organization