الفهرس 
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Abstract
This study illustrates the importance of understanding the relative potential for resistance to recombinant toxins from different serovars of B. thuringiensis insecticides, which contain varying mixtures of Cry toxins. These were obtained in this study from conjugation between different serovars of B.t. Bacillus thuringiensis are used commercially to control pest insects belonging to the orders Lepidoptera, Diptera, and Coleoptera. The potency of B.t. preparations was determined against Spodoptera littoralis. Insecticidal crystal proteins from B.t. are extremely toxic to many pests and have been a primary focus of much recent research. These toxins, which are produced in crystalline inclusions during sporulation, kill insects by binding to and creating pores in midgut membranes.