Survival and reproduction of natural populations of Helicoverpa armigera on Bt-cotton hybrids in Raichur, India

摘要

Transgenic Bt-cotton is commercially cultivated on the rationale that it produces toxins that defend the plants primarily from caterpillars damaging cotton bolls. From the context of crop protection, it is important that these bollworms remain susceptible to the toxins, so that their populations are under check. However, if certain individuals are able to survive and breed on the transgenics, they can build populations resistant to the toxins. In one such instance we discovered individuals of Helicoverpa armigera, the most prominent among bollworms in India, surviving on commercial Bt-cotton hybrids containing single (Cry1Ac) and double (Cry1Ac and Cry2Ab) genes in experimental plots of the University of Agricultural Sciences, Raichur campus, India. Analyses of various biological parameters measured through laboratory breeding on the respective hybrids revealed that these surviving individuals could not only complete their life cycle but also reproduce. A proportion of individuals of the succeeding generation were also able to complete their life cycle on the transgenic commercial hybrids. Interestingly, many of the biological parameters of the bollworm across Bt and non-Bt hybrids were mostly comparable. These results not only validate the occurrence of natural populations of H. armigera on Bt-cotton hybrids, but also provide evidence for its survival and successful reproduction in India.