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Conifer chemical defense: Rugulation of bark beetle colonization and pheromone emission
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Ecological Chemistry)
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Terpenes and phenols are of importance in conifer defense against insects and pathogens. Knowledge about tree chemical defense is vital for developing practical methods to maintain healthy forests. With the aims of characterizing the defensive chemical induction in Norway spruce Picea abies and demonstrating its ecological function to spruce bark beetle Ips typographus, we measured the terpenoid and phenolic content in the bark of mature Norway spruce trees suffering windstorm, inoculated with Ceratocystis polonica, or treated with methyl jasmonate (MeJA), and investigated the colonization and pheromone emission of I. typographus.

All three stressors altered the chemical profile in the bark of Norway spruce. Trees damaged by windstorm had lower proportions of (+)-3-carene and two unidentified stilbenes, and a higher taxifolin glycoside content than trees without apparent windstorm damage; C. polonica inoculation induced extremely strong quantitative terpene accumulation in the wound reaction zone, but only increased the levels of (+)-3-carene, sabinene and terpinolene in the bark near the reaction zone; MeJA treatment generally elicited quantitative terpene accumulation, but the induction differed extensively between individual trees. In addition, logs from MeJA-treated tree showed much stronger wounding response compared to control logs.

The chemical profile of Norway spruce affected the colonization and pheromone emission of I. typographus. In response to fungal inoculation, terpene present in the reaction zone inhibited the colonization of I. typographus in a dose-dependent manner. Host defense elicited by MeJA treatment reduced emissions of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two key aggregation pheromone components of I. typographus, and altered the ratio between the two components.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 75 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:16
Keyword [en]
Picea abies, Ips typographus, Ceratocystis polonica, methyl jasmonate, windstorm, stress response, terpenes, phenols, colonization, pheromone emission
National Category
Agricultural Science
Identifiers
URN: urn:nbn:se:kth:diva-33199ISBN: 978-91-7415-884-7OAI: oai:DiVA.org:kth-33199DiVA: diva2:413917
Public defence
2011-05-23, sal F3, Lindstedtsvägen 26, KTH, Stockholm, 15:52 (English)
Opponent
Supervisors
Note
QC 20110503Available from: 2011-05-03 Created: 2011-04-29 Last updated: 2011-05-03Bibliographically approved
List of papers
1. Storm-induced tree resistance and chemical differences in Norway spruce (Picea abies)
Open this publication in new window or tab >>Storm-induced tree resistance and chemical differences in Norway spruce (Picea abies)
2011 (English)In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 68, no 3, 657-665 p.Article in journal (Refereed) Published
Abstract [en]

Windstorm is one of the most destructive environmental disturbance factors on forests, but its influence on conifer defense chemistry and susceptibility to insects and diseases is not well understood.

National Category
Agricultural Science
Identifiers
urn:nbn:se:kth:diva-33318 (URN)10.1007/s13595-011-0049-3 (DOI)000290913000021 ()2-s2.0-80051488241 (ScopusID)
Note
QC 20110607Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-06-07Bibliographically approved
2. The influence of Ceratocystis polonica inoculation and methyl jasmonate application on terpene chemistry of Norway spruce, Picea abies
Open this publication in new window or tab >>The influence of Ceratocystis polonica inoculation and methyl jasmonate application on terpene chemistry of Norway spruce, Picea abies
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2010 (English)In: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 71, no 11-12, 1332-1341 p.Article in journal (Refereed) Published
Abstract [en]

Constitutive and inducible terpene production is involved in conifer resistance against bark beetles and their associated fungi. In this study 72 Norway spruce (Picea abies) were randomly assigned to methyl jasmonate (MJ) application, inoculation with the bluestain fungus Ceratocystis polonica, or no-treatment control. We investigated terpene levels in the stem bark of the trees before treatment, 30 days and one year after treatment using GC-MS and two-dimensional GC (2D-GC) with a chiral column, and monitored landing and attack rates of the spruce bark beetle, Ips typographus, on the trees by sticky traps and visual inspection. Thirty days after fungal inoculation the absolute amount and relative proportion of (+)-3-carene, sabinene, and terpinolene increased and (+)-alpha-pinene decreased. Spraying the stems with MJ tended to generally increase the concentration of most major terpenes with minor alteration to their relative proportions, but significant increases were only observed for (-)-beta-pinene and (-)-limonene. Fungal inoculation significantly increased the enantiomeric ratio of (-)-alpha-pinene and (-)-limonene 1 month after treatment, whereas MJ only increased that of (-)-limonene. One year after treatment, both MJ and fungal inoculation increased the concentration of most terpenes relative to undisturbed control trees, with significant changes in (-)-beta-pinene, (-)-beta-phellandrene and some other compounds. Terpene levels did not change in untreated stem sections after treatment, and chemical induction by MJ and C polonica thus seemed to be restricted to the treated stem section. The enantiomeric ratio of (-)-alpha-pinene was significantly higher and the relative proportions of ( -)-limonene were significantly lower in trees that were attractive to bark beetles compared to unattractive trees. One month after fungal inoculation, the total amount of diterpenes was significantly higher in putative resistant trees with shorter lesion lengths than in putative susceptible trees with longer lesions. Thus, terpene composition in the stem bark may be related to resistance of Norway spruce against I. typographus and C. polonica.

Keyword
Picea abies, Ceratocystis polonica, Methyl jasmonate, Terpene, Defense, Ips typographus
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-29456 (URN)10.1016/j.phytochem.2010.05.017 (DOI)000280321000015 ()2-s2.0-77954244208 (ScopusID)
Funder
Formas
Note
QC 20110208Available from: 2011-02-08 Created: 2011-02-02 Last updated: 2011-05-03Bibliographically approved
3. Induced Terpene Accumulation in Norway Spruce Inhibits Bark Beetle Colonization in a Dose-Dependent Manner
Open this publication in new window or tab >>Induced Terpene Accumulation in Norway Spruce Inhibits Bark Beetle Colonization in a Dose-Dependent Manner
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2011 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 6, no 10, e26649- p.Article in journal (Refereed) Published
Abstract [en]

Background: Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and resistance to bark beetle colonization. Methods: To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle, Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark. Results: Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m(-2)) and 2.6% as much gallery length (0.029 m m(-2) vs. 1.11 m m(-2)) as trees with low terpene levels (n = 6). There was a highly significant rank correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of similar to 100 mg terpene g(-1) dry phloem trees suffered only moderate beetle colonization, and above a high threshold of similar to 200 mg terpene g(-1) dry phloem trees were virtually unattacked. Conclusion/Significance: This is the first study demonstrating a dose-dependent relationship between induced terpenes and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the impact of tree-killing bark beetles.

National Category
Environmental Sciences Agricultural Science
Identifiers
urn:nbn:se:kth:diva-33324 (URN)10.1371/journal.pone.0026649 (DOI)000296507500103 ()2-s2.0-80054784209 (ScopusID)
Note
QC 20111213Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-12-13Bibliographically approved
4. Host resistance elicited by methyl jasmonate reduces emission of aggregation pheromones by the spruce bark beetle: Ips typographus
Open this publication in new window or tab >>Host resistance elicited by methyl jasmonate reduces emission of aggregation pheromones by the spruce bark beetle: Ips typographus
2011 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 167, no 3, 691-699 p.Article in journal (Refereed) Published
Abstract [en]

We treated Norway spruce (Picea abies) stems with methyl jasmonate (MeJA) to determine possible quantitative and qualitative effects of induced tree defenses on pheromone emission by the spruce bark beetle Ips typographus. We measured the amounts of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two main components of the beetle's aggregation pheromone, released from beetle entrance holes, along with phloem terpene content and beetle performance in MeJA-treated and untreated Norway spruce logs. As expected, phloem terpene levels were higher and beetle tunnel length was shorter (an indication of poor performance) in MeJA-treated logs relative to untreated logs. Parallel to the higher phloem terpene content and poorer beetle performance, beetles in MeJA-treated logs released significantly less 2-methyl-3-buten-2-ol and (S)-cis-verbenol, and the ratio between the two pheromone components was significantly altered. These results suggest that host resistance elicited by MeJA application reduces pheromone emission by I. typographus and alters the critical ratio between the two main pheromone components needed to elicit aggregation. The results also provide a mechanistic explanation for the reduced performance and attractivity observed in earlier studies when bark beetles colonize trees with elicited host defenses, and extend our understanding of the ecological functions of conifer resistance against bark beetles.

Keyword
Conifer, Induced defenses, Ips typographus, Pheromone, Terpene
National Category
Agricultural Science
Identifiers
urn:nbn:se:kth:diva-33327 (URN)10.1007/s00442-011-2017-x (DOI)000295984800010 ()2-s2.0-80054017869 (ScopusID)
Funder
Formas
Note
QS 2011. Updated from submitted to published.Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-11-17Bibliographically approved

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