Study of Expression of Indigenous Bt cry2AX1 Gene in T₃ Progeny of Cotton and its Efficacy Against Helicoverpa armigera (Hubner)

Abstract

Development of transgenic Bt crops with stable and high level of Bt protein expression over generations under different environmental conditions is critical for successful deployment at field level. In the present study, progenies of transgenic cotton Coker310 event, CH12 expressing novel cry2AX1 gene were evaluated in T₃ generation for stable integration, expression and resistance against cotton bollworm, Helicoverpa armigera. The cry2AX1 gene showed stable inheritance and integration in the T₃ progeny plants as revealed by PCR and Southern blot hybridization. The expression of Cry2AX1 protein on 90 days after sowing (DAS) was in the range of 1.055 to 1.5 µg/g of fresh leaf tissue except one plant which showed 0.806 µg/g of fresh leaf tissue and after 30 days (i.e., on 120 DAS) three plants recorded in between 0.69 to 0.82 µg/g and other plants are in range of 0.918 to 1.058 µg/g of fresh leaf tissue. Detached leaf bit bioassay in T₃ progeny on 110 DAS recorded mortality of 73.33 to 93.33 per cent against H. armigera and severe growth retardation in surviving larvae. These results indicate that the expression of chimeric cry2AX1 is stable and exhibits insecticidal activity against H. armigera in T₃ progeny of CH12 event of transgenic cotton.

Keywords:
cry2AX1; Helicoverpa armigera; Bacillus thuringiensis; Insect bioassay