Characterisation of Bacillus thuringiensis kurstaki strains by toxicity, plasmid profiles and numerical analysis of their cryIA genes

  • S Kashyap
  • DV Amla
Keywords: Bacillus thuringiensis kurstaki, Helicoverpa armigera, Spodoptera litura, -endotoxin, plasmids, Southern hybridization.


In the present comparative study, four Bacillus thuringiensis kurstaki strains (HD1, dipel, HD73, HD1dipel) were characterized by investigating their total plasmid profiling; cryIA genes profiling and
toxicity towards local isolates of agricultural insects Helicoverpa armigera and Spodoptera litura. Result showed that LC50 for S. litura were 0.11 g of HD73, 0.027 g of HD1, 0.20 g of dipel and 0.018
g of HD1 dipel, while LC50 for H. armigera insect were 0.04 g of HD73, 0.031 g of HD1, 0.011 g of dipel and 0.008 g of HD1dipel. The native plasmid number and type varied from 4 - 8 among these strains and HindIII restriction showed 0.4 to 8.0 kb size fragments. The numerical classification of the cryIA gene profiles showed two distinct clusters at 48% similarity level. Cluster one of 80% similarity comprises of two strains HD73 and dipel, while cluster two of 65% consisted of HD1 and HD1dipel strains. Southern analysis of restricted plasmid combined with cryIA profile can provide an effective approach for investigation of taxonomic relationship within Bacillus thuringiensis kurstaki strains.

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eISSN: 1684-5315