Combination of Cry1Ac and Cry2A to Produce Resistance against Helicoverpa armigera in Cotton

Genetic manipulation to get desirable characters in cash crops like cotton remains the prime objective of crop biotechnology. To produce transgenic plants resistant against bollworms, newly emerged embryos of MNH-786 cotton variety were transformed with Agrobacterium tumefaciens strain LBA4404 harboring the plasmid pKHG4 vector containing Cry1Ac+Cry2A genes under the control of CaMV35S promoter. The integration and expression of these genes were evaluated by PCR, Florescent In-Situ Hybridization (FISH), and ELISA, respectively. Out of 700 putative transgenic cotton plants, 10 plants (1.03% transformation efficiency) showed the presence of genes Cry1Ac+Cry2A through PCR analysis. In vitro, insect feeding bioassay was done for estimation of mortality percentage of Helicoverpa armigera. Insect mortality rate and morphological characteristics of Bt cotton were analyzed by phenotypic correlation, path coefficient regression and covariance to evaluate the advantage of transgenic technology in numerical terms. Statistical analysis indicated significant positive correlation between insect mortality and cotton seed yield. Helicoverpa armigera mortality data produced a directly proportional relation with cotton seed yield. The results of this study support the improvement of cotton defense mechanism against insects and natural competitors through genetic modification.