Expression of chimeric Bt gene, Cry1Aabc in transgenic pigeonpea (cv. Asha) confers resistance to gram pod borer (Helicoverpa armigera Hubner.)

The gram pod borer (Helicoverpa armigera Hubner) is the most serious insect pest of pigeonpea. It is highly susceptible to the insecticidal proteins of Bacillus thuringiensis (Bt). A codon-optimized chimeric Cry1Aabc gene of Bt driven by a constitutive promoter was introduced in pigeonpea (cv. Asha) to confer resistance against the insect. A total of eight transgenic plants could be established with transformation frequency of 0.06%. Two transgenic events were selected for advancement based on high insect mortality, single locus integration, protein expression and fertility status. Quantitative ELISA indicated high protein expression in different plant parts viz., leaves (pre and post flowering), flowers, pod walls and immature seeds. Analysis for the stable integration, expression and insect mortality (detached leaf and pod bioassay) led to identification of lines with high efficacy. These events were further advanced for the identification of a viable event by selfing to create homozygosity. The chimeric Cry1Aabc expressed in pigeonpea is effective against gram pod borer and can be utilized in transgenic variety development programme.