STUDIES ON GENE REGULATION OF SOME GENES THAT RELATED TO BT. TOXINS RESISTANCE IN THE COTTON WORM, Spodoptera littoralis

Abstract

The Egyptian cotton leaf worm, S. littoralis (Boisd.) (Lepidoptera: Noctuidae) is a polyphagous pest in subtropical and tropical regions. The long-term applications of conventional pesticides to control pests, including S. littoralis, has led to the developments of resistance, negative impacts on the ecosystems and unhealthy hazards to human and natural enemies. These problems are incentives to search for alternative safe and effective control measures with different modes of action. Biological control agents can be used where chemical pesticides are banned or where pests have developed resistance to standard chemicals and play an important role in integrated pest management programs. Among these approaches is the using of the entomopathogenic bacterium, B. thuringiensis that provides a valuable alternative to chemical insecticides. Bt synthesizes delta endotoxin protein crystals that belong to a class of bacterial toxins are known as pore forming toxins that specifically affect cell permeability and disrupting cellular integrity of insect-midgut cells. Cry toxins have a potent and specific insecticidal activity and can kill their insect larval hosts through a complex multi-step process resulting in the formation of a pore in the membrane of midgut epithelial cells. Development of transgenic crops that express Cry toxins was a remarkable breakthrough in pest control instead of the use of chemical