Dual dialect of herbivore-induced chickpea plant volatile organic compounds: Roles in threat to pod borer and egg parasitoid attraction

Abstract

Volatile organic compounds (VOCs) emitted by crop plants in response to herbivore attack—known as herbivore-induced plant volatiles (HI-pVOCs)—play a key role in indirect inducible resistance. These volatiles are utilized by plants either to repel herbivores or to attract their natural enemies. However, a limited understanding of the mechanisms underlying HI-pVOCs has hindered further research and application of plant volatiles in pest management strategies. In the present study, volatile profiles induced by the pod borer Helicoverpa armigera were analyzed in both infested and uninfested chickpea seedlings. A total of 27 volatile compounds, including 11 hydrocarbons, were detected in infested seedlings, whereas only 16 compounds with three hydrocarbons were identified in healthy seedlings. Eight volatiles from the infested chickpea profile were selected and evaluated under field conditions against the pod borer during the winter season of 2021–22. Foliar application of synthetic eicosane and azulene at 500 ppm on the 35^th and 45^th days after sowing significantly reduced larval populations by 41.18–44.11 %, and pod damage by 26.37–26.89 %. Additionally, eicosane and octadecane at 500 ppm enhanced the foraging activity of the egg parasitoid Trichogramma chilonis under laboratory conditions. These findings suggest that eicosane, in particular, is a promising volatile compound for the management of chickpea pod borer, while also supporting the activity of its natural egg parasitoid.