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Conifer chemical defenses influence meal properties of the pine weevil Hylobius abietis
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (AKBK/Ecological Chemistry Group)ORCID iD: 0000-0003-2867-2004
Department of Ecology, Swedish University of Agricultural Sciences.
Department of Ecology, Swedish University of Agricultural Sciences.
Department of Ecology, Swedish University of Agricultural Sciences.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Chemical defenses of conifers can be experimentally activated to respond more efficiently to feeding damage by insects. One chemical elicitor that triggers plant defenses, and thereby protects conifers, is methyl jasmonate (MeJA). However, there is little known about the associations between MeJA-induced conifer defenses, and the meal properties of phytophagous insects. To address this knowledge gap, we have analyzed relations between volatile contents of Scots pine (Pinus sylvestris L.) tissues, and meal properties of the pine weevil (Hylobius abietis (L.)). Phloem and needles (both weevil target tissues) from MeJA-treated and control seedlings were extracted by n-hexane and analyzed by two-dimensional gas chromatography-mass spectrometry (2D GC-MS). Feeding of pine weevils on seedlings from the same batches were video-recorded to determine meal properties. Multivariate statistical analyses showed that phloem and needle contents of MeJA-treated seedlings had different volatile compositions from the control seedlings. Levels of (+)-α-pinene were high, and levels of the antifeedant 2-phenylethanol were low, in phloem of control seedlings with feeding damage. Accordingly, pine weevils fed more slowly and had shorter meals on MeJA-treated seedlings. In addition, the chemical compositions of phloem and needles – and accordingly weevil meal durations on them – were more similar in MeJA-treated seedlings than in controls. The results illustrate that detailed knowledge of insect responses can help efforts to identify and elucidate specific roles of resistance agents in complex chemical profiles.

Keyword [en]
Pinaceae; Pinus sylvestris; Hylobius abietis; Short-term feeding; Induced defense; Methyl jasmonate; Phloem; Needles; Terpenes; Aromatics
National Category
Organic Chemistry Analytical Chemistry Other Chemistry Topics Ecology
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-183267OAI: oai:DiVA.org:kth-183267DiVA: diva2:908933
Funder
Swedish Foundation for Strategic Research , Parasite Resistant Trees
Note

First and second author contributed equally to this work.

QS 2016

Available from: 2016-03-03 Created: 2016-03-03 Last updated: 2016-03-04Bibliographically approved
In thesis
1. Effects of methyl jasmonate on chemical defenses of conifer seedlings in relation to feeding by Hylobius abietis
Open this publication in new window or tab >>Effects of methyl jasmonate on chemical defenses of conifer seedlings in relation to feeding by Hylobius abietis
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The chemical elicitor methyl jasmonate (MeJA) could replace insecticides in Europe and Asia for protection of young conifers against the pine weevil (Hylobius abietis). This thesis mainly focuses on the effects of MeJA treatment on chemical defenses of conifers from seedling batches with documented field resistance. Tissues of three pine species and one spruce species, with various treatments, were here extracted in hexane, whereafter volatile contents of tissues were separated and analyzed by 2D GC-MS.

Induced responses of seedlings of Maritime pine (Pinus pinaster) and Monterey pine (Pinus radiata) to the folivore pine processionary (Thaumetopoea pityocampa), and the phloem-feeder H. abietis, have been studied. Amounts of mono- and sesqui-terpenes (and also non-volatile resin) in conifer tissues (needles and phloem) were less induced by T. pityocampa than by H. abietis.

The MeJA-treated seedlings of Scots pine (Pinus sylvestris) changed their composition of phloem monoterpenes (induction of (-)-β-pinene), and were better protected in field than the seedlings of Norway spruce (Picea abies), which increased their total amounts of monoterpenes. Orientation bioassays with H. abietis showed deterrent effects of (-)-β-pinene, (+)-3-carene, (-)-bornyl acetate and 1,8-cineole. Conversely, (-)-α-pinene (induced in P. abies but not in P. sylvestris) was non-deterrent.

MeJA-treated seedlings fed on by H. abietis contained higher amounts of the H. abietis antifeedant 2-phenylethanol, in tissues and emissions. Phloem of control seedlings instead induced the (+)-α-pinene, which is one of the enantiomers of the H. abietis attractant α-pinene.

In response to MeJA treatment, the relative amounts of the (+)-α-pinene increased in the phloem of  P. radiata, while it decreased in P. pinaster phloem. The preference of H. abietis in the field for P. radiata before P. pinaster may be explained by these changes in enantiomers of the H. abietis attractant α-pinene.

Abstract [sv]

Barrträd är viktiga för skogsindustrin. I Sverige består 57% av ytan av produktiv skogsmark, och av dessa träd utgörs 80% av gran och tall. Som försvar mot insekter och sjukdomar, producerar barrträden kådämnen. För unga barrträd i Europa och Asien är snytbaggen (Hylobius abietis) en allvarlig skadegörare, som orsakar skogsnäringen stora kostnader. För att skydda små gran- och tallplantor före utplanteringen, skulle växthormonet metyljasmonat (MeJA) kunna användas.

I denna avhandling har effekter av MeJA-behandling och insektsangrepp undersökts på de två viktigaste barrträden i Sverige, tall och gran (Pinus sylvestris och Picea abies) och på två arter i medelhavsområdet (Pinus radiata och Pinus pinaster). De kemiska försvarsämnena i barrträd har analyserats för att utvärdera effekterna av MeJA-behandling. Vävnader från barrträd med olika behandling har extraherats i organiska lösningsmedel och dofterna från plantorna har insamlats genom fastfas-mikroextraktion. De flyktiga ämnena har separerats och identifierats med hjälp av gaskromatografi och masspektrometri (GC-MS). Dessutom har optiskt aktiva doftämnen separerats med hjälp av en tvådimensionell GC-MS.

Plantornas olika försvarsreaktioner har studerats vid angrepp av snytbaggen, som är en floemätare, och av tallfjärilslarv (Thaumetopoea pityocampa), som huvudsakligen äter barr. De lättflyktiga ämnena (mono- och seskviterpener) och de icke-flyktiga ämnena (kådsyror) ökade mer i stam och barr från angrepp av H. abietis än av T. pityocampa.

Sammansättning av monoterpener ändrades i de MeJA-behandlade tallplantorna i Sverige, specifikt ökade (-)-β-pinene i stamfloemet. Tallplantorna var bättre skyddade i fält än granplantorna, där den totala mängden monoterpener ökade.

(-)-β-Pinene, (+)-3-carene, (-)-bornyl acetate och 1,8-cineole visade sig ha en negativ effekt på snytbaggens orientering mot talldoft i orienteringstester. En av monoterpenerna, (-)-α-pinene, som av MeJA-behandlingen inducerats i granen, men inte i tallen, hade ingen negativ effekt på snytbaggen.

MeJA-behandlade tallplantor som angripits av snytbaggen, innehöll större mängder av snytbagge-äthämmaren 2-fenyletanol, både i vävnader och i emissioner. Stam från kontrollplantor inducerade istället (+)-α-pinene, vilken är en av de optiska isomererna av snytbagge-attrahenten α-pinene.

För de spanska arterna, som svar på MeJA-behandling, ökade de lättflyktigaste terpenerna i barren hos P. radiata men inte hos P. pinaster, vilken redan innehöll en hög terpenhalt. De relativa mängderna av (+)-α-pinene ökade också i stammen hos P. radiata, medan de minskade i P. pinaster. I fält väljer snytbaggen att gå till P. radiata- framför P. pinaster-plantor, vilket kan vara kopplat till de skillnader i α-pinene-isomerer, vilka här har observerats.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xii, 49 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:7
Keyword
Pinaceae, Pinus pinaster, Pinus radiata, Pinus sylvestris, Picea abies, Thaumetopoea pityocampa, Hylobius abietis, Needles, Phloem, Feeding, Vaccination, Priming, Methyl jasmonate, Aromatics, Phenolics, Monoterpenes, Pinaceae, Pinus pinaster, Pinus radiata, Pinus sylvestris, Picea abies, Thaumetopoea pityocampa, Hylobius abietis, Barr, Floem, Ätning, Vaccinering, Metyljasmonat, Aromater, Fenoler, Monoterpener
National Category
Other Chemistry Topics Organic Chemistry Analytical Chemistry Ecology
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-183268 (URN)978-91-7595-863-7 (ISBN)
Public defence
2016-03-30, sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , Parasite Resistant Trees
Note

QC 20160304

Available from: 2016-03-04 Created: 2016-03-03 Last updated: 2016-04-01Bibliographically approved

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