Silicon Supplementation Alters the Composition of Herbivore Induced Plant Volatiles and Enhances Attraction of Parasitoids to Infested Rice Plants

Abstract

Silicon (Si) is important in plant defenses that operate in a direct manner against herbivores, and work in rice (Oryza sativa) has established that this is mediated by the jasmonate signaling pathway. Plant defenses also operate indirectly, by the production of herbivore induced plant volatiles (HIPVs) that attract predators and parasitoids of herbivores. These indirect defenses too are mediated by the jasmonate pathway but no earlier work has demonstrated an effect of Si on HIPVs. In this study, we tested the effect of Si supplementation versus Si deprivation to rice plants on subsequent HIPV production following feeding by the important pest, rice leaffolder (Cnaphalocrocis medinalis). Gas chromatography–mass spectrometry analyses showed lower production of α-bergamotene, β-sesquiohellandrene, hexanal 2-ethyl, and cedrol from +Si herbivore-infested plants compared with -Si infested plants. These changes in plant chemistry were ecologically significant in altering the extent to which parasitoids were attracted to infested plants. Adult females of Trathala flavo-orbitalis and Microplitis mediator both exhibited greater attraction to the HIPV blend of +Si plants infested with their respective insect hosts compared to -Si infested plants. In equivalent studies using RNAi rice plants in which jasmonate perception was silenced there was no equivalent change to the HIPV blend associated with Si treatment; indicating that the effects of Si on HIPVs are modulated by the jasmonate pathway. Further, this work demonstrates that silicon alters the HIPV blend of herbivore-infested rice plants. The significance of this finding is that there are no earlier-published studies of this phenomenon in rice or any other plant species. Si treatment to crops offers scope for enhancing induced, indirect defenses and associated biological control of pests because parasitoids are more strongly attracted by the HIPVs produced by +Si plants.

Silicon amendment to rice plants contributes to reduced feeding in a phloem‐sucking insect through modulation of callose deposition

“…Si amendment is also reported to be involved in priming the chemical defense in plants (Ghareeb et al., ; Han et al., ; Yang, Han, Li, Li et al., ; Ye et al., ) as well as in the augmented release of herbivore‐induced plant volatiles that attract natural enemies of the attacking pests (Kvedaras, An, Choi, & Gurr, ; Liu et al., ). An important induced plant defense to sucking insects is callose deposition on sieve plates.…”

Silicon amendment induces synergistic plant defense mechanism against pink stem borer (Sesamia inferens Walker.) in finger millet (Eleusine coracana Gaertn.)

“…JA and SA regulate defenses against herbivores, particularly JA controls cell-content-feeding and tissue-chewing insects 16,17 while SA and JA together regulate the defense against phloem-feeding insects 18 . It has been shown recently that Si induces JA-mediated defense responses against insects and pests 19 , indicating that Si can enhance the plant resistance against herbivores by regulating the defense responsive phytohormone pathways. Si also induces the priming process in host plant by sensitizing and preparing the plant for quick responses against the future herbivore attacks [20][21][22] .…”

“…Organization of conserved motifs identified in finger millet silicon transporter proteins was predicted by MEME tools. The sequence and motifs identified were indicated by different coloured(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). (2020) 10:4229 | https://doi.org/10.1038/s41598-020-61182-0…”

Do silicon and nitric oxide induce resistance to Mahanarva spectabilis (Hemiptera: Cercopidae) in forage grasses?

“…Although silicon and nitric oxide positively affect the growth and development of some crops, this effect was not observed in the current analysis. This result may be related to the influence of these chemicals on plant resistance because increased resistance could cause photoassimilates to be directed toward defense mechanisms instead of vegetative growth . In fact, the current analysis showed a significant interaction between inducers and attack by M. spectabilis nymphs and adults with regard to phenolic compound concentrations in forage grass species.…”

“…The current study also demonstrated that plants attacked by adult insects showed a greater concentration of phenolic compounds than control plants or plants attacked only by nymphs and also proved to have greater concentrations of foliar silicon. Several authors have demonstrated that insect infestation triggers the production of secondary compounds and antiherbivore enzymes, and affects the emission of volatile compounds . According to Lattanzio et al , resistance traits in plants require the replacement of resources.…”