Transgenic cowpea plants expressing Bacillus thuringiensis Cry2Aa insecticidal protein imparts resistance to Maruca vitrata legume pod borer.

KEY MESSAGE: Fertile independent transgenic cowpea lines expressing the BtCry2Aa toxin with increased resistance to the most devastating lepidopteran insect pest, Maruca pod borer has been developed for the first time. Cowpea is a staple legume important for food and nutritional security in sub-Saharan Africa and Asia, where its production is limited by the key pest, legume pod borer (Maruca vitrata). Cowpea varieties resistant to M. vitrata are not known, hence, development of Maruca pod borer resistance cowpea through genetic engineering is a promising approach to improve its production. In the present study, transgenic cowpea plants expressing Bacillus thuringiensis Cry2Aa insecticidal protein were developed for the first time using Agrobacterium tumefaciens-mediated transformation of cotyledonary explants. T0 plants recovered from Agrobacterium cocultured explants on medium containing 120 mgl-1 of kanamycin were identified on the basis of the presence of transgenes by PCR, their integration into genome by Southern hybridization and expression of their transcripts by semi quantitative PCR (sqRT-PCR) and quantitative Real-time-PCR (qRT-PCR) and protein by Western blot analysis. The transformation efficiency obtained was 3.47% with 11 independent T0 transgenic lines. The bioefficacy of Cry2Aa protein expressed in randomly selected four T0 plant's leaves and pods was evaluated by feeding Maruca pod borer demonstrated a significant lower damage and a high level of Maruca mortality (more than 90%) for all these Bt lines. The inheritance of transgenes from T0 to T1 progeny plants was demonstrated by PCR analysis. The transgenic plants generated in this study can be used in cowpea breeding program for durable and sustainable legume pod borer resistance.