Effects of Bacillus thuringiensis delta-endotoxins on the pea aphid (Acyrthosiphon pisum)

Area of Science:

• Entomology
• Molecular Biology
• Biochemistry

Background:

• Bacillus thuringiensis (Bt) produces delta-endotoxins, a class of insecticidal proteins.
• Bt toxins are widely used as biopesticides in agriculture.
• The efficacy of specific Bt toxins against different insect species varies greatly.

Purpose of the Study:

• To evaluate the toxicity of four specific Bacillus thuringiensis delta-endotoxins (Cry3A, Cry4Aa, Cry11Aa, and Cyt1Aa) against the pea aphid, Acyrthosiphon pisum.
• To assess the impact of these toxins on aphid mortality and growth rates.
• To compare the toxicity of these toxins with Cry1Ab.

Main Methods:

• Pea aphids (Acyrthosiphon pisum) were exposed to varying concentrations of purified delta-endotoxins.
• Mortality rates and growth rates of the aphids were monitored over a defined period.
• Exhaustive buffer-based controls were employed to validate the observed effects.

Main Results:

• Cry3A, Cry4Aa, Cry11Aa, and Cyt1Aa demonstrated low to moderate toxicity, affecting both mortality and growth rates of Acyrthosiphon pisum.
• Cry1Ab exhibited negligible toxicity, with effects only observed at very high concentrations.
• Buffer controls confirmed the specificity of the observed toxic effects.

Conclusions:

• The tested Bacillus thuringiensis delta-endotoxins possess limited insecticidal activity against the pea aphid.
• Cry1Ab is not an effective toxin for controlling pea aphid populations.
• These findings highlight the need for targeted selection of Bt toxins based on the specific pest species.