Synergistic Insecticidal Activity Against Hyphantria cunea by Cry9Aa3 Mutants and Cry1Ah Combinations.

Area of Science:

• Molecular biology
• Entomology
• Biotechnology

Background:

• The fall webworm (Hyphantria cunea) causes substantial damage to forestry and agriculture.
• Current control methods rely on cry1 genes, raising concerns about pest resistance.
• Developing novel insecticidal genes and combinations is essential to manage resistance.

Purpose of the Study:

• To identify new insecticidal genes effective against Hyphantria cunea.
• To enhance the insecticidal properties of Cry9Aa3 through mutation.
• To evaluate the synergistic effects of new genes and mutants in combination with existing ones.

Main Methods:

• Screening of cry9Aa3 and cry9Aa4 genes for insecticidal activity against H. cunea.
• Analysis of 14 mutants of Cry9Aa3, focusing on the triple-amino-acid substitution mutant 316LRG318AAA.
• Toxicity assays (LC50 determination) and stability tests in H. cunea midgut juice.
• Evaluation of synergistic effects when combined with Cry1Ah.

Main Results:

• Cry9Aa3 and Cry9Aa4 exhibited insecticidal activity against H. cunea.
• The 316LRG318AAA mutant showed a 1.49-fold increase in insecticidal activity (LC50 = 3.69 μg/g) and enhanced stability.
• Combinations of Cry9Aa3/316LRG318AAA with Cry1Ah demonstrated significant synergistic effects (4.76 and 8.33, respectively).

Conclusions:

• The mutant 316LRG318AAA and its combination with Cry1Ah represent highly toxic options against H. cunea.
• These findings provide valuable genetic resources for developing transgenic poplars.
• This research is crucial for delaying pest resistance and improving pest management strategies.