Selection for resistance to mCry3A-expressing transgenic corn in western corn rootworm

Area of Science:

• Agricultural Entomology
• Molecular Entomology
• Pest Management

Background:

• Western corn rootworm (Diabrotica virgifera virgifera) is a major pest of corn.
• Bt-toxins, such as mCry3A, are used in genetically modified corn to control this pest.
• Development of insect resistance to Bt-toxins is a significant concern for sustainable agriculture.

Purpose of the Study:

• To investigate the development of resistance to mCry3A in a laboratory colony of western corn rootworm.
• To quantify the level of resistance over multiple generations of selection.
• To assess the impact of resistance on insect performance and plant damage under field conditions.

Main Methods:

• Established a laboratory colony from field survivors of mCry3A-expressing corn (MIR604).
• Selected the colony over 14 generations on mCry3A-expressing corn, with a control colony on non-expressing corn.
• Assessed resistance using toxicity assays (LC50 values), field screening for plant damage, and seedling bioassays for larval recovery.

Main Results:

• Resistance ratio (LC50) increased significantly over generations, reaching 15.4 after 10 generations.
• Selected colonies showed no significant difference in plant damage or larval recovery between MIR604 and isoline corn after 7 and 14 generations, respectively.
• Control colonies showed significant differences in plant damage and larval recovery, indicating susceptibility.

Conclusions:

• Laboratory colonies of western corn rootworm have developed significant resistance to mCry3A.
• This resistance impacts pest performance and reduces the efficacy of mCry3A-expressing corn.
• Adherence to resistance management plans is crucial for preserving the effectiveness of Bt-based pest control strategies.