Silicon-induced changes in plant volatiles reduceattractiveness of wheat to the bird cherry-oat aphid Rhopalosiphum padiand attractthe parasitoid Lysiphlebus testaceipes.

Reinaldo Silva De Oliveira,Weliton D Silva,Maria Fernanda G V Peñaflor,Felipe G Gonçalves,Ana Paula Korndörfer,José Maurício S Bento,Marcus Vinicius Sampaio,Yonggen Lou

doi:10.1371/journal.pone.0231005

Abstract

Silicon (Si) supplementation is well-known for enhancing plant resistance to insect pests, however, only recently studies revealed that Si accumulation in the plant not only confers a mechanical barrier to insect feeding, but also primes jasmonic acid-dependent defenses. Here, we examined whether Si supplementation alters wheat volatile emissions that influence the bird cherry-oat aphid (Rhopalosiphum padi) olfactory preference and the aphid parasitoid Lysiphlebus testaceipes. Even though Si accumulation in wheat did not impact aphid performance, we found that R. padi preferred constitutive volatiles from–Si wheat over those emitted by +Si wheat plants. In Y-tube olfactometer bioassays, the parasitoid was attracted to volatiles from +Si uninfested wheat, but not to those from–Si uninfested wheat. +Si and–Si aphid-infested plants released equally attractive blends to the aphid parasitoid; however, wasps were unable to distinguish +Si uninfested plant odors from those of aphid-infested treatments. GC-MS analyses revealed that +Si uninfested wheat plants emitted increased amounts of a single compound, geranyl acetone, compared to -Si uninfested wheat, but similar to those emitted by aphid-infested treatments. By contrast, Si supplementation in wheat did not alter composition of aphid-induced plant volatiles. Our results show that changes in wheat volatile blend induced by Si accumulation mediate the non-preference behavior of the bird cherry-oat aphid and the attraction of its parasitoid L. testaceipes. Conversely to the literature, Si supplementation by itself seems to work as an elicitor of induced defenses in wheat, and not as a priming agent.

Highlights

The role of Silicon (Si) in plant nutrition is controversial [1,2,3]
As we have gained more insight into the underlying mechanisms that account for the enhanced resistance of Si-supplemented plants to herbivores, studies have focused on addressing the effects of Si accumulation via defense signal transduction pathways [22, 50]
Studies on rice indicate that the physical barrier formed by Si accumulation makes plants more resistant to herbivores before their arrival and, once Si-supplemented plants are upon attack, greater levels of induced defenses results from priming of jasmonic acid (JA)-modulated antiherbivore defenses [11, Fig 1

Summary

Introduction

The role of Silicon (Si) in plant nutrition is controversial [1,2,3]. interest on Si supplementation as an agronomic practice has been growing because it generally promotes increased crop yield [4], especially of those that are Si-accumulators plants, such as Poaceae [5]. Numerous studies have demonstrated that accumulation of Si in the shoots of crop grasses induces resistance against a wide range of herbivorous arthropods of different feeding guilds, such as leaf feeders [11], sap-sucking insects [12], stalk borers [13] and piercing-sucking [14]. Si supplementation promotes higher activity levels of defense-related enzymes in plants following insect attack [11, 21], indicating a priming effect. Ye et al [22] elucidated that jasmonic acid-signaling pathway, which plays a central role in activating antiherbivore induced defenses [23], is involved in Siinduced resistance and that Si enhances the accumulation of jasmonic acid (JA) levels following herbivory, confirming the priming effect

Methods

Results

Conclusion