Journal of Chemical Ecology (2019) 45, 715-724

Enakshi Ghosh and Radhika Venkatesan (2019)
Plant volatiles modulate immune responses of Spodoptera litura
Journal of Chemical Ecology 45 (8), 715-724
Abstract: Plants emit a specific blend of volatiles in response to herbivory and these volatiles, which often attract predators and parasitoids function as an indirect plant defense. The impact of plant volatiles in shaping herbivore defenses is unclear. Here, we report that specific plant volatiles induce immune responses in the polyphagous herbivore, Spodoptera litura. We characterized the hemocyte profile and established their functional significance with respect to ontogeny and exposure to specific plant volatiles. Fifth instar larvae showed the highest number and hemocytes diversity. We characterized seven different types of hemocytes, of which granulocytes performed phagocytosis, oenocytoids showed melanization activity, and plasmatocytes along with granulocytes and oenocytoids were found to be involved in encapsulation. Among the six volatiles tested, exposure to (E)-β-ocimene caused the highest increase in total hemocytes number (THC) followed by linalool and (Z)-3-hexenyl acetate exposure. Although THC did not differ between these three volatile treatments, circulating hemocytes diversity varied significantly. (E)-β-ocimene exposure showed higher number of plasmatocytes and phenol oxidase activity. The interaction of the parasitic wasp Bracon brevicornis with (E)-β-ocimene exposed larvae was poor in terms of delayed paralysis and lower egg deposition. In choice assays, the wasp showed clear preference towards control larvae indicating (E)-β-ocimene treatment renders the host unattractive. Hemocyte profiles post-parasitoid exposure and (E)-β-ocimene treatment were similar indicating cue-based priming. When challenged with Bacillus thuringiensis, linalool exposure resulted in the highest survival as compared to other volatiles. Our results show that specific HIPVs can modulate cellular immunity of S. litura, revealing a new role for HIPVs in tri-trophic interactions.
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Link to article at publishers website
Database assignments for author(s): Enakshi Ghosh

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Spodoptera litura
Habrobracon brevicornis (parasitoid)	Spodoptera litura