Transgenic plants expressing two Bacillus thuringiensis toxins delay insect resistance evolution

Area of Science:

• Agricultural Science
• Entomology
• Genetics

Background:

• Insect resistance to Bacillus thuringiensis (Bt) toxins in transgenic crops is a significant agricultural challenge.
• Theoretical models propose that pyramided Bt toxins (two dissimilar genes) can more effectively delay resistance than single-toxin strategies.
• Managing insect resistance is crucial for the sustainability of Bt crop technology.

Purpose of the Study:

• To experimentally test the prediction that pyramided Bt toxins delay insect resistance more effectively than single-toxin deployment.
• To evaluate the efficacy of two-gene Bt pyramids against the diamondback moth (Plutella xylostella).

Main Methods:

• Developed a model system using Bt transgenic broccoli and an artificial population of diamondback moths.
• Moth populations were selected over 24 generations under exposure to single-gene (Cry1Ac or Cry1C) or pyramided (Cry1Ac + Cry1C) Bt toxins.
• Compared resistance development rates across different Bt toxin deployment strategies (pyramids, mosaics, sequential).

Main Results:

• Resistance to pyramided two-gene Bt plants was significantly delayed compared to single-gene plants in mosaic deployment.
• Pyramided toxins were more effective in delaying resistance than sequential deployment starting with Cry1Ac.
• The study confirmed theoretical predictions regarding the enhanced efficacy of pyramided Bt toxins.

Conclusions:

• Pyramided Bt toxin strategies in transgenic crops are highly effective in delaying insect resistance.
• These findings have critical implications for the development and regulatory approval of next-generation insecticidal crops.
• Implementing pyramided Bt toxins can enhance the durability of pest control in agriculture.