Interaction between host plant resistance and biological activity of Bacillus thuringiensis in managing the pod borer Helicoverpa armigera in chickpea uri icon

abstract

  • The legume pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) has developedhigh levels of resistance to conventional insecticides, and therefore, efforts are being made to developtransgenic chickpea expressing toxin genes from the bacterium, Bacillus thuringiensis (Bt) for controllingthis pest. However, there is an apprehension that acid exudates in chickpea might interfere with biologicalactivity of Bt. Therefore, we studied the biological activity of Bt (BiolepR) on four chickpea genotypeswith different levels of resistance to H. armigera under field conditions, and by incorporating lyophilizedlead and pod tissue into the artificial diet with and without Bt. The pH of the acid exudates varied from2.1 to 2.90, and malic and oxalic acid were the major components of the acid exudates in differentchickpea genotypes. There was no survival of H. armigera larvae in chickpea plants spayed with 0.1, 0.2and 0.5% of Bt. There was a significant reduction in larval survival, larval and pupal weights andfecundity, and prolongation of larval and pupal periods in chickpea plots sprayed with Bt (0.05%) ascompared to the unsprayed plants. Biological activity of Bt was lower on artificial diets with leaf or podpowder of chickpea genotypes, which might be because of a low intake of Bt toxins due to antifeedanteffects of acid exudates in the chickpea or reduction in biological activity of Bt due to the interaction ofbiochemical constituents in chickpea with the Bt toxins. Larval survival, larval and pupal weights,pupation and adult emergence were significantly lower on diets with leaf or pod powder of the H.armigera-resistant genotypes than on the susceptible check. Chickpea genotypes with resistance to H.armigera acted in concert with Bt to cause adverse effects on the survival and development of this insect.The results suggested that development of transgenic chickpeas expressing toxin genes form Bt will bequite effective for controlling of the pod borer, H. armigera

publication date

  • 2011
  • 2011