Comparative Analysis Delineates the Transcriptional Resistance Mechanisms for Pod Borer Resistance in the Pigeonpea Wild Relative Cajanus scarabaeoides (L.) Thouars.

Isaac Njaci,Abigail Ngugi-Dawit,Sita Ghimire,Sagadevan Mundree,Brett Williams,Richard Oduor,Linh Hoang,Leah Kago

doi:10.3390/ijms22010309

Abstract

Insect pests pose a serious threat to global food production. Pod borer (Helicoverpa armigera (Hübner)) is one of the most destructive pests of leguminous crops. The use of host resistance has been an effective, environmentally friendly and sustainable approach for controlling several agricultural pests. The exploitation of natural variations in crop wild relatives could yield pest-resistant crop varieties. In this study, we used a high-throughput transcriptome profiling approach to investigate the defense mechanisms of susceptible cultivated and tolerant wild pigeonpea genotypes against H. armigera infestation. The wild genotype displayed elevated pest-induced gene expression, including the enhanced induction of phytohormone and calcium/calmodulin signaling, transcription factors, plant volatiles and secondary metabolite genes compared to the cultivated control. The biosynthetic and regulatory processes associated with flavonoids, terpenes and glucosinolate secondary metabolites showed higher accumulations in the wild genotype, suggesting the existence of distinct tolerance mechanisms. This study provides insights into the molecular mechanisms underlying insect resistance in the wild pigeonpea genotype. This information highlights the indispensable role of crop wild relatives as a source of crucial genetic resources that could be important in devising strategies for crop improvement with enhanced pest resistance.

Highlights

Pigeonpea (Cajanus cajan (L.) Mill sp.) is the sixth most important grain legume in the world
The results indicate that wild pigeonpea relatives use superior defense mechanisms
To investigate the genotype-specific response to the borer we conducted an insect on the cultivated susceptible cultivar pod infestation, borer infestation, we conducted an bioassay insect bioassay on the cultivated susceptible and a resistant wild relative accession (WT)

Summary

Introduction

Pigeonpea (Cajanus cajan (L.) Mill sp.) is the sixth most important grain legume in the world. It is predominantly grown in Asia, Africa and the Caribbean islands. India is the largest producer, with 4.29 million tons, accounting for 72% of the world’s pigeonpea production [1]. The crop plays a vital role in rainfed agriculture to sustain the livelihood of millions of people in semi-arid tropics and subtropics. Pigeonpea productivity has stagnated due to abiotic and biotic stresses, inferior crop varieties and inefficient management practices. Biotic stress from insect pests comprises the major production constraint [3]. The pod borer (Helicoverpa armigera (Hübner)) is the most damaging pest of pigeonpea.

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Results

Discussion

Conclusion