Nucleopolyhedrovirus infection enhances plant defences by increasing plant volatile diversity

ABSTRACT

Plant–herbivore–entomopathogen tri-trophic interactions and biodiversity are relatively understudied topics in ecology. Particularly, the effects of entomopathogens on herbivore-induced plant volatiles and plant volatile diversity on the defensive function of plants have not been studied in detail. We used soybean (Glycine max), beet armyworm larvae (Spodoptera exigua), and nucleopolyhedrovirus (NPV) as a tri-trophic system to determine whether NPV infection can promote the emission and diversity of volatiles from plants. We also investigated whether NPV infection affects the attraction of Microplitis pallidipes, an important endoparasitoid of larval S. exigua. Uninfested soybean plants released 7 detectable volatile compounds while plants fed upon by healthy and NPV-infected S. exigua larvae released 12 and 15 volatiles, respectively. Female parasitoids were more attracted to the volatiles from plants that were fed upon by NPV-infected larvae than healthy larvae, and more attracted to the volatiles from plants that were fed upon by healthy larvae than no larvae. The selective responses of parasitoids to plant odours increased as plant volatile diversity increased. Our study suggests that the NPV infection facilitates the release of plant volatiles and enhances the defensive function of plants by increasing plant volatile diversity which in turn attracts more parasitoids. Also, this work reveals that plants might accrue two indirect benefits from NPV infection, cessation of herbivore feeding and more parasitisation.

KEYWORDS:

• Biological control
• defensive function
• parasitoid
• tri-trophic system
• volatile diversity

Acknowledgements

The authors thank Professor Coby Schal at Department of Entomology & Plant Pathology of North Carolina State University for offering useful suggestions and helpful comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The present work was supported by the National Natural Science Foundation of China (31672083, 31601641), Shanghai Agriculture Commission of China (2014-7-3-2), SAAS Program for Excellent Research Team (2017) and Forestry scientific Research in the Public Interest (201304403-1-5).