Indian Journal of Science and Technology

Abstract

Cotton (Gossypium hirsutum) is the most important fiber crop and backbone of textile industry of the world. Cotton bollworm (Helicoverpa armigera)is one of the most destructive insect pests of cotton in India. Expression of chimeric or hybrid Bt protein has led to enhanced resistance to pests and added advantage with respect to insect resistance management. We report in this paper, expression of a chimeric cry2AX1 gene (consisting part of cry2Aa and cry2Ac) in transgenic cotton and its resistance towards H. armigera. Agrobacterium strain LBA4404 harbouring chimeric cry2AX1 gene construct driven by enhanced CaMV35S promoter in pCAMBIA2300 backbone was used for co-cultivation of cotton cv. Cocker 310 embryogenic calli. A total of 11 putative T0 transgenic plants were generated and all of them found PCR positive for the presence cry2AX1 and nptII genes. Southern blot hybridization confirmed the T-DNA integration and intactness of cry2AX1 gene. Quantitative assessment of cry2AX1 protein by ELISA in transgenic T0 cotton plants showed expression of protein in the range 0.015 to 0.080 µg/g fresh leaf tissue. Insect bioassay of transgenic T0 cotton plants using H. armigera neonates recorded a mortality of 10 to 36.66 per cent and showed significant reduction in leaf feeding and inhibition of growth in surviving larvae. The results demonstrate potential of the chimeric cry2AX1 gene in developing H. armigera-resistant transgenic cotton varieties.
Keywords: Agrobacterium tumefaciens, Cotton Transformation, Cry2AX1, ELISA, Insect Bioassay, Helicoverpa armigera