Expression of Cry2Aa, a Bacillus thuringiensis insecticidal protein in transgenic pigeon pea confers resistance to gram pod borer, Helicoverpa armigera

Shweta Singh,T Vinutha,K Karthik,Rohini Sreevathsa,K Y S Rao,R Maniraj,R Lakshmikanth,Nikhil Ram Kumar,Prasanta K Dash,P Ananda Kumar,Debasis Pattanayak,T Arulprakash,N Muralimohan,N B Shashibhushan

doi:10.1038/s41598-018-26358-9

Abstract

Pigeon pea is an important legume infested by a plethora of insect pests amongst which gram pod borer Helicoverpa armigera is very prominent. Imparting resistance to this insect herbivore is of global importance in attaining food security. Expression of insecticidal crystal proteins (ICP) in diverse crops has led to increased resistance to several pests. We report in this paper, expression of Cry2Aa in transgenic pigeon pea and its effectiveness towards H. armigera by employing Agrobacterium-mediated in planta transformation approach. Approximately 0.8% of T1 generation plants were identified as putative transformants based on screening in the presence of 70 ppm kanamycin as the selection agent. Promising events were further recognized in advanced generations based on integration, expression and bioefficacy of the transgenes. Seven T3 lines (11.8% of the selected T1 events) were categorized as superior as these events demonstrated 80–100% mortality of the challenged larvae and improved ability to prevent damage caused by the larvae. The selected transgenic plants accumulated Cry2Aa in the range of 25–80 µg/g FW. The transgenic events developed in the study can be used in pigeon pea improvement programmes for pod borer resistance.

Highlights

Pigeon pea is an important grain legume in Asia, Africa and parts of Latin America[1,2]
In addition to Cry[1] series of insecticidal crystal proteins (ICP), it is pertinent to assess the ability of another ICP, Cry2Aa, for its efficacy against H. armigera in pigeon pea
Our group is actively involved in the development of pigeon pea transgenics with other novel Bt ICPs26

Summary

Introduction

Pigeon pea is an important grain legume in Asia, Africa and parts of Latin America[1,2]. Since the mode of action of cry2Aa is different when compared to cry[1] series of Bt ICPs17, stacking transgenic crops expressing both the genes can be a viable approach for delaying evolution of resistance to cry toxins by Helicoverpa armigera. In this direction, the purpose of the present study was to demonstrate the utility of cry2Aa gene in transgenic pigeon pea against H. armigera and reiterate the applicability of an apical meristem-targeted tissue culture-independent in planta transformation approach for pigeon pea improvement

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Conclusion