Bacillus thuringiensis Cry1C resistance development and its processing pattern in Egyptian cotton leaf worm: Spodoptera littoralis (Boisd.) (Lepidoptera:Noctuidae)

Abstract

Biopesticides based on the entomopathogenic bacterium, Bacillus thuringiensis toxins, have shown high ability to control several pests belonging to order Lepidoptera. Egyptian cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera:Noctuidae), is a major pest that attacks various crops in Egypt, and Cry1C toxin-based formulations are heavily used to its control. A laboratory investigation was conducted to study the resistance development in S. littoralis against Cry1C toxin. Thus, a field strain of S. littoralis was selected and maintained under laboratory conditions for 12 generations. The selection pressure resulted in 32.12-fold of resistance ratio after 12 generations. The hydrolysis of Cry1C toxin by the midgut extracts of the susceptible line, and the resistant line was compared. Results revealed that Cry1C toxin was hydrolyzed more rapidly in the resistant line than the susceptible one. The Cry1C toxin was processed till 1 hour after incubation in the susceptible line; but in case of resistant line, the Cry1C toxin was degraded in 1 hour after incubation.