Over-expression of Trigonella foenum-graecum defensin (Tfgd2) and Raphanus sativus antifungal protein (RsAFP2) in transgenic pigeonpea confers resistance to the Helicoverpa armigera

Abstract

Pigeonpea is an important food legume crop cultivated in tropical and sub-tropical regions around the world wherein the Indian subcontinent accounting for over 90 % of global production. It is a rich source of protein and is an important component of a well-balanced diet for the majority of Indians. Among the other insect pests, pigeonpea productivity is mostly affected by Helicoverpa armigera which is causing severe yield loss. Non-availability of resistant genes in germplasm and constraints with traditional breeding induce the application of a genetic engineering approach to generate insect resistance in pigeonpea. Expression of plant defensins in various crops provided enhanced resistance towards a variety of pests and pathogens. In the current study, two defensins Trigonella foenum-graecum defensin 2 (Tfgd2) and Raphanus sativus antifungal protein 2 (RsAFP2) integrated by a linker peptide was transferred into pigeonpea as a fusion gene by Agrobacterium mediated transformation. Putative transgenic lines were confirmed through PCR and the promising lines were identified in the following generations based upon integration, expression and bioefficiency of the fusion gene. Leaf bioassay conducted against H. armigera larvae showed increased levels of insect resistance compared to the control, where six T2 plants were identified as superior lines showing less than 25 % of leaf damage. Our findings illustrates that Tfgd2–RsAFP2 fusion protein is efficient in imparting protection against the insect pest and the transgenic lines developed in this study could be used for further pigeonpea improvement projects.