Morphological and Biochemical Characterization of Bacillus thuringiensis Berliner Isolates and their Evaluation against Plutella xylostella Linnaeus

Eleven isolates of Bacillus thuringiensis were morphologically and biochemically characterized and evaluated for iasecticidal activity against Plutella xylostella Linnaeus under field-cum-laboratory conditions. All the isolates were gram positive, rod shaped, spore forming and showed typical colony morphology with mucoid or glistening surfaces having entire edges and density ranging between translucent to opaque. Glucose was fermented by all the cultures only with acid production. Xylose and Mannitol were fermented by Bt d and Bt VK isolates, respectively. All cultures were catalase positive, oxidase positive, nitrate reducing (except Bt d), degraded tyrosine, hydrolysed casein and starch and utilized citrate as a carbon source. Results of bioassay studies revealed that four isolates, namely, Bt 5, 4D4, Bt 9 and MTCC 868 caused complete mortality of the second instar larvae of Plutella xylostella within 96 hours at uniform concentration of 10⁹ spores/ml.