Identification of Some Bacillus thuringiensis Isolates by PCR and their Potential against the Cotton Leaf Worm

Abstract

Bacillus thuringiensis produces unique crystalline cytoplasmic inclusion bodies during the process of sporulation. Both spores and inclusion bodies are released upon lysis of the parent bacterium at the end of sporulation and if ingested these spores and crystals act as poisons for certain insects. Therefore, B. thuringiensis is referred to as a stomach poison. Twenty five isolates of B. thuringiensis were tested for the presence of both crystal protein by a microscopic examination and the cryI (Aa) gene using PCR. The microscopic examination revealed that nine of the 25 isolates had the bipyramodial shaped crystal protein, a distinguishing feature of B. thuringiensis, and which is active against insects of the order Lepidoptera. Detection of the cryI (Aa) gene with PCR, using specific primers CJI-1 and CJI-2, revealed that all nine isolates which have crystal protein, also had the cryI (Aa) gene. Screening of these isolates with the cotton leaf worm (Spodoptera littoralis, order Lepidoptera) showed that M5, ATCF and M8 isolates were the most toxic. _____________________________________________________________________________________________________________