Example 2: Pyramiding Bt toxins: effects on pest populations?
Example 2: Pyramiding Bt toxins: effects on pest populations?
Bt cotton, corn and potatoes first planted in 1996; by 2006, Bt corn and cotton on 32 million ha. worldwide
Development of Bt resistance
Risk factors for pest populations evolving Bt resistance
Bt resistance
Managing Bt resistance
Managing Bt resistance
Slide 8
“High dose plus refugia”
High-dose plus refugia
Why does adding susceptible plants (refuges) slow evolution of Bt resistance?
Slide 12
Fitness (ω)
What does this mean?
Managing Bt resistance
Slide 16
Bt pyramids should have different modes of action to minimize cross-resistance
Common ideas – HF and Bt
Dogma: gene pyramids work because of low probability of mutation to multiple virulence
Mundt’s critique:
Slide 21
Probabilities hypothesis requires the assumption that virulence mutations at different loci are independent, yet there are several mechanisms for attaining simultaneous changes to virulence at different loci
Is it worthwhile pyramiding resistances that are already partially or completely defeated?
Kousik and Ritchie, Phytopathology, 1999, 89:1066-1072:
Pyramiding multiple QTL for disease resistance