Assessment of Pigeonpea (Cajanus cajan L.) transgenics expressing Bt ICPs, Cry2Aa and Cry1AcF under nethouse containment implicated an effective control against herbivory by Helicoverpa armigera (Hübner)

Abstract

BACKGROUND Pigeonpea is a source of quality proteins and the main constituent of a well‐balanced diet for majority of Indian population. One of the major constraints in the production of pigeonpea is a polyphagous insect pest, Helicoverpa armigera. Non‐availability of resistant sources in the germplasm and limitations in conventional breeding have been key factors for continued yield losses. Additionally, hazards of chemical fertilizers on the environment have prompted the scientific community to develop alternative strategies. Bacillus thuringiensis (Bt) insecticidal proteins (ICPs) have emerged as the most reliable source for the control of insect pests through transgenics. RESULTS Transgenic pigeonpea plants harboring validated Bt ICPs, Cry2Aa and Cry1AcF were developed by a non‐tissue culture based in planta transformation strategy and assessed for integration of Transfer‐DNA (T‐DNA) and efficacy against pod borer under in vitro conditions. For the first time this study demonstrates the successful evaluation of 19 transgenic pigeonpea events (11 with cry2Aa and 8 with cry1AcF) under soil and pot conditions in a nethouse containment. The stability in the performance was assessed stringently by deliberate H. armigera larval challenging. The trial identified ten promising events of both the genes that portrayed reduced damage to the herbivore. CONCLUSION We present the first ever successful evaluation of pigeonpea transgenics with the ability to mitigate pod borer under nethouse conditions. The transgenics depicted molecular evidence for the stability of T‐DNA integration, consistency in the expression of Cry proteins and resistance against H. armigera. These events can form a pool of useful transgenics to manage the devastating pod borer. © 2019 Society of Chemical Industry

Secondary genepool of Australian Cajanus species contains sources of resistance to Helicoverpa armigera (Hübner)

“…Protease inhibitors were reported to interfere with gut proteinases of H. armigera , leading to inactivation of the insect digestive system followed by insect mortality (Swathi et al, 2015). Subsequently, high expression of the genes associated with α‐linolenic acid metabolism was reported in C. platycarpus (Ramkumar et al, 2020; Rathinam et al, 2020) with an increase in time of pod borer infestation. Simultaneously incremental levels of lipoxygenase enzyme in Fusarium udum resistant accessions of pigeonpea were reported in an experiment employing mechanical wounding and inoculation of α‐linolenic acid, providing further evidence of the involvement of jasmonic acid in response to biotic stress (Uma Maheswari Devi, Srinivas Reddy, Usha Rani, Reddy, Narsa Reddy, & Reddanna, 2000).…”

Biochemical basis of resistance to pod borer (Helicoverpa armigera) in Australian wild relatives of pigeonpea

“…Despite identifying potential markers for pod borer resistance in wild pigeonpea (Sharma & Manohar, 2009; Swathi et al, 2016), linkage drag has been the major limitation in transferring the resistance through conventional breeding (Venkata et al, 2019). Due to this limitation, attempts were made to develop transgenic pigeonpea with herbivory resistance through transformation using several different approaches, such as pricked embryo axes ( cry1Ac ) (Ajinder et al, 2016), in planta transformation ( cry2Aa and cry1AcF ) (Ramkumar et al, 2020) and embryo rescue in pigeonpea (Shivali et al, 2020). Being the second‐largest source of Cajanus species, Australian wild species have been less exploited for their biotic and abiotic stress‐resistance traits.…”

Exploitation of Novel Bt ICPs for the Management of Helicoverpa armigera (Hübner) in Cotton (Gossypium hirsutum L.): A Transgenic Approach

“…Genetic engineering for the development of insect resistant plants has been considered as a revolutionary contribution in agricultural biotechnology. Transgenesis in economically important crop plants like cotton ( Chen et al, 2017 ; Ribeiro et al, 2017 ; Siddiqui et al, 2019 ; Bajwa et al, 2020 ; Jadhav et al, 2020 ; Katta et al, 2020 ); soybean ( Marques et al, 2017 ; Moghaieb et al, 2019 ; Qin et al, 2019 ; Bacalhau et al, 2020 ); maize ( Moscardini et al, 2020 ); pigeon pea ( Ghosh et al, 2017 ; Singh et al, 2018 ; Ramkumar et al, 2020 ); chick pea ( Das et al, 2017 ); cow pea ( Bett et al, 2017 ; Addae et al, 2020 ; Kumar et al, 2021 ); sweet potato ( Zhong et al, 2019 ); jute ( Majumder et al, 2020 ); castor ( Muddanuru et al, 2019 ), etc., by the introgression of insecticidal proteins encoding genes from Bacillus thuringiensis ( Bt ) resulted in plants with improved ability to mitigate the pest load. Reduced topical applications of chemical pesticides and increased agricultural productivity have been major achievements of transgenic technology ( Fleming et al, 2018 ) in crop improvement.…”

“…Similarly, cry2Aa (GenBank accession ID: ABW87832.1 ), is known to exhibit broad spectrum efficacy against two insect orders ( Singh et al, 2018 ; Kumar et al, 2021 ), lepidoptera and diptera ( Qiu et al, 2017 ; Zhao et al, 2017 ; Goje et al, 2020 ). Efficacy of these genes has been effectively demonstrated against H. armigera in both model and crop plants ( Muralimohan et al, 2020 ; Ramkumar et al, 2020 ; Kumar et al, 2021 ).…”