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  • 1.
    Axelsson, Karolin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zendegi-Shiraz, Amene
    Swedjemark, Gunilla
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Clone specific chemical defense responses in Norway spruce to infestations by two pathogenic fungi2016In: Forest Pathology, ISSN 1437-4781, E-ISSN 1439-0329Article in journal (Other academic)
    Abstract [en]

    Heterobasidion parviporum (Hp) were investigated using four clones of Norway spruce (Picea abies) with different susceptibility to Heterobasidion sp. Eight year old trees were inoculated with Ep and Hp to minimize the variation due to environment. After three weeks the bark tissue at the upper border of the inoculation hole were extracted with hexane and analyzed by GC-MS. Both treatment and clonal differences were found based on induced mono-, sesqui- and diterpenes. In addition, the Hp produced toxin, fomanoxin, was identified in lowest amount in the most Hp susceptible clone. The clonal trees seem to use different defense strategies towards the two fungi. One of the clones was able to induce strong chemical defense against both fungi, one clone induced chemical defense only against Ep and the most susceptible clone exhibited the least capacity to produce an effective defense against Ep and Hp. Two diterpenes were found to be distinctly different between clones with different susceptibilities, which can be used as chemical indication of Norway spruce resistance against fungi.

  • 2.
    Danielsson, Marie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lunden, Karl
    Elfstrand, Malin
    Hu, Jiang
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Arnerup, Jenny
    Ihrmark, Katarina
    Swedjemark, Gunilla
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Stenlid, Jan
    Chemical and transcriptional responses of Norway spruce genotypes with different susceptibility to Heterobasidion spp. infection2011In: BMC Plant Biology, ISSN 1471-2229, E-ISSN 1471-2229, Vol. 11, p. 154-Article in journal (Refereed)
    Abstract [en]

    Background: Norway spruce [Picea abies (L.) Karst.] is one of the most important conifer species in Europe. The wood is economically important and infections by wood-rotting fungi cause substantial losses to the industry. The first line of defence in a Norway spruce tree is the bark. It is a very efficient barrier against infection based on its mechanical and chemical properties. Once an injury or an infection is recognized by the tree, induced defences are activated. In this study we examined transcriptional response, using 454-sequencing, and chemical profiles in bark of Norway spruce trees with different susceptibility to Heterobasidion annosum s.l. infection. The aim was to find associations between the transcriptome and chemical profiles to the level of susceptibility to Heterobasidion spp. in Norway spruce genotypes. Results: Both terpene and phenol compositions were analysed and at 28 days post inoculation (dpi) high levels of 3-carene was produced in response to H. annosum. However, significant patterns relating to inoculation or to genotypes with higher or lower susceptibility could only be found in the phenol fraction. The levels of the flavonoid catechin, which is polymerized into proanthocyanidins (PA), showed a temporal variation; it accumulated between 5 and 15 dpi in response to H. annosum infection in the less susceptible genotypes. The transcriptome data suggested that the accumulation of free catechin was preceded by an induction of genes in the flavonoid and PA biosynthesis pathway such as leucoanthocyanidin reductase. Quantitative PCR analyses verified the induction of genes in the phenylpropanoid and flavonoid pathway. The qPCR data also highlighted genotype-dependent differences in the transcriptional regulation of these pathways. Conclusions: The varying dynamics in transcriptional and chemical patterns displayed by the less susceptible genotypes suggest that there is a genotypic variation in successful spruce defence strategies against Heterobasidion. However, both high levels of piceasides and flavonoids in the less susceptible genotypes suggested the importance of the phenolic compounds in the defence. Clearly an extended comparison of the transcriptional responses in the interaction with Heterobasidion between several independent genotypes exhibiting reduced susceptibility is needed to catalogue mechanisms of successful host defence strategies.

  • 3.
    Danielsson, Marie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lundén, Karl
    Arnerup, Jenny
    Hu, Jiang
    Zhao, Tao
    Swedjemark, Gunilla
    Elfstrand, Malin
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Stenlid, Jan
    Chemical and transcriptional responses of Norway spruce clones with different susceptibility to Heterobasidion spp. infectionManuscript (preprint) (Other academic)
  • 4.
    Danielsson, Marie
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Zhao, Tao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Science and Technology, Örebro University, Örebro, Sweden.
    Borg-Karlson, Anna-Karin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Arthropod infestation sites and induced defence can be traced by emission from single spruce needles2019In: Arthropod-Plant Interactions, ISSN 1872-8855, E-ISSN 1872-8847, Vol. 13, no 2, p. 253-259Article in journal (Refereed)
    Abstract [en]

    Emissions of defence chemicals from Norway spruce seedlings can be induced by feeding arthropods or by exogenous hormonal application. Some defence chemicals may attract or repel associated arthropods. The aim of this study was to show that it is possible to detect and collect stress-induced volatiles from micro sites, such as at the scale of a single needle, in vivo by using SPME. Methyl jasmonate application on the stem of Norway spruce seedlings induced emission of (E)-beta-farnesene only from the needles closest to the application site. Emissions of (E)-beta-farnesene, (E,E)-alpha-farnesene and (E)-alpha-bisabolene were only detected from needles infested by the spider mite Oligonychus ununguis. The total volatile amount detected by SPME-GC-MS reached a considerable mass of 14 ng/needle/24 h, suggesting that emission from damaged and stressed conifers might have a larger impact on the macro climate than previously estimated.

  • 5.
    Kusumoto, Norihisa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Akita Prefectural University, Japan.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Swedjemark, G.
    Ashitani, T.
    Takahashi, K.
    Borg-Karlson, Anna Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Antifungal properties of terpenoids in Picea abies against Heterobasidion parviporum2014In: Forest Pathology, ISSN 1437-4781, E-ISSN 1439-0329, Vol. 44, no 5, p. 353-361Article in journal (Refereed)
    Abstract [en]

    The antifungal properties of 14 major oleoresin-constitutive terpenoids of Norway spruce (Picea abies) against Heterobasidion parviporum were evaluated in vitro at three gradient concentrations, 0.1, 0.2 and 0.4 mu mol/cm(2), on potato dextrose agar medium. Eight monoterpene hydrocarbons (+)- and (-)-alpha-pinene, (-)-beta-pinene, (+)-3-carene, myrcene, (+)- and (-)-limonene, terpinolene; four oxygenated monoterpenes alpha-terpineol, terpinen-4-ol, 1,8-cineole, bornyl acetate; and two resin acids abietic acid and dehydroabietic acid were selected. Abietic and dehydroabietic acids showed the highest antifungal activities at all concentrations. Among oxygenated monoterpenes, bornyl acetate and alpha-terpineol showed antifungal activity at the highest concentration. Among monoterpene hydrocarbons, (+)-alpha-pinene showed similar activity to terpinen-4-ol and 1,8-cineole at the highest concentration; however, it was lower than alpha-terpineol and bornyl acetate. Other monoterpene hydrocarbons inhibited mycelial growth by <10%. Re-extraction of medium surfaces after the test period revealed that most alpha-terpineol and terpinen-4-ol remained unchanged on the surface but monoterpene hydrocarbons completely disappeared. However, notable fungal transformed products were observed on surfaces applied with 1,8-cineole and bornyl acetate. Thus, mycelial growth inhibition of monoterpenoids might be caused by complex functions such as biodegradation and/or detoxification by interaction between mycelium and compound. These results provide a basis for future studies considering the role of chemodiversity in the comprehensive chemical defence of P. abies.

  • 6.
    Kännaste, Astrid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lindström, A.
    Stattin, E.
    Långström, B.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Odors of Norway spruce (Picea abies L.) seedlings: Differences due to age and chemotype2013In: Trees, ISSN 0931-1890, E-ISSN 1432-2285, Vol. 27, no 1, p. 149-159Article in journal (Refereed)
    Abstract [en]

    Small conifer seedlings (mini-seedlings) are less damaged by the large pine weevil Hylobius abietis (L.) (Coleoptera: Curculionidae) compared to conventional seedlings. Chemical difference between the seedling types is one possible explanation for this phenomenon. In the present paper, the emissions of volatile organic compounds (VOC) of 7- to 43-week-old Norway spruce [Picea abies (L.) Karst.] seedlings were analyzed. Collection and identification of the volatiles was made by solid phase micro-extraction and gas chromatography mass spectrometry (SPME-GC-MS). The enantiomers of α-pinene and limonene were separated in a two-dimensional GC (2D-GC). Most of the seedlings represented either a limonene- or a bornyl acetate-chemotype. Only minor changes in the volatile composition of the two types of seedlings were found during the first year. Age-related changes, however, were found in the volatiles released by wounded phloem where green leaf volatiles (GLVs) and borneol were the dominated VOC for young seedling. The attractive compound for the pine weevil, α-pinene, was first detected in the phloem emissions of 18- to 22-week-old seedlings. Different storage conditions of the seedlings during the winter/early spring-phase influenced the volatile composition in the phloem. High amount of GLVs was characteristic for the 43-week-old seedlings stored in naturally changing outdoor temperature, but not present in the seedlings winter-stored at a constant temperature of -4 °C. The possible role of these observed differences in odor emissions between seedlings of different age and physiological status for the feeding preferences of the large pine weevil is discussed.

  • 7.
    Kännaste, Astrid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lindström, Anders
    Dalarna University, School of Industrial Technology and Management.
    Stattin, Eva
    Dalarna University, School of Industrial Technology and Management.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Långström, Bo
    Swedish University of Agricultural Sciences, Department of Entomology.
    Odors of Norway spruce (Picea abies) seedlings: differences due to age and chemotype and their relevance for weevil resistanceManuscript (Other academic)
  • 8.
    Kännaste, Astrid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lindström, Anders
    Dalarna University, School of Industrial Technology and Management.
    Stattin, Eva
    Dalarna University, School of Industrial Technology and Management.
    Långström, Bo
    Swedish University of Agricultural Sciences, Department of Entomology.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Volatile emissions from pine seedlings: age-related changes and chemotypesManuscript (Other academic)
  • 9. Lu, Jun
    et al.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ye, Hui
    The shoot-feeding ecology of three Tomicus species in Yunnan Province, southwestern China2014In: Journal of Insect Science, ISSN 1536-2442, E-ISSN 1536-2442, Vol. 14, p. 37-Article in journal (Refereed)
    Abstract [en]

    Three Tomicus pine shoot beetles, T. yunnanensis (Kirkendall and Faccoli) (Coleoptera: Scolytidae), T. minor (Hartig), and T. brevipilosus (Wood and Bright), have been causing serious damage to Yunnan pine (Pinus yunnanensis (Franchet) (Pinales: Pinaceae)) stands in Yunnan, southwestern China. However, their ability to coexist in the crowns of the same trees during the shoot-feeding phase has not been elucidated. In our study, we investigated and compared the shoot-feeding ecology of the three species of pine shoot beetle in P. yunnanensis in Anning County, Yunnan Province. Shoot-feeding by T. yunnanensis, T. minor, and T. brevipilosus initiated in April, May, and June, and ended in February, April, and May, respectively. Individual T. yunnanensis and T. minor adults fed in shoots for about seven months, and T. brevipilosus for nine months, before initiating reproduction. All three Tomicus species fed in the current-year shoots close to the apical bud. No specific overwintering behavior was observed prior to reproduction. The entrance hole of T. yunnanensis was furthest away from the apical bud, and T. minor was the closest to the apical bud. Differences in the spatial distribution of these shoot-feeding sites might reduce competition among the three beetle species. The long-lasting and overlapping shoot-feeding by the three Tomicus species may reduce the resistance of P. yunnanensis and facilitate the reproduction of these beetles in the trunks of living trees, and thus help explain the severe damage by Tomicus in P. yunnanensis.

  • 10.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Conifer chemical defense: Rugulation of bark beetle colonization and pheromone emission2011Doctoral 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.

  • 11.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Axelsson, Karolin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, P.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fungal Symbionts of the Spruce Bark Beetle Synthesize the Beetle Aggregation Pheromone 2-Methyl-3-buten-2-ol2015In: Journal of Chemical Ecology, ISSN 0098-0331, E-ISSN 1573-1561Article in journal (Refereed)
    Abstract [en]

    Tree-killing bark beetles depend on aggregation pheromones to mass-attack their host trees and overwhelm their resistance. The beetles are always associated with phytopathogenic ophiostomatoid fungi that probably assist in breaking down tree resistance, but little is known about if or how much these fungal symbionts contribute to the beetles’ aggregation behavior. In this study, we determined the ability of four major fungal symbionts of the spruce bark beetle Ips typographus to produce beetle aggregation pheromones. The fungi were incubated on Norway spruce Picea abies bark, malt agar, or malt agar amended with 0.5 % 13C glucose. Volatiles present in the headspace of each fungus were analyzed for 7 days after incubation using a SPME autosampler coupled to a GC/MS. Two Grosmannia species (G. penicillata and G. europhioides) produced large amounts of 2-methyl-3-buten-2-ol (MB), the major component in the beetles’ aggregation pheromone blend, when growing on spruce bark or malt agar. Grosmannia europhioides also incorporated 13C glucose into MB, demonstrating that the fungi can synthesize MB de novo using glucose as a carbon source. This is the first clear evidence that fungal symbionts of bark beetles can produce components in the aggregation pheromone blend of their beetle vectors. This provides new insight into the possible ecological roles of fungal symbionts in bark beetle systems and may deepen our understanding of species interactions and coevolution in these important biological systems.

  • 12.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Eerbilgin, Nadir
    Krokene, Paal
    Host resistance elicited by methyl jasmonate reduces emission of aggregation pheromones by the spruce bark beetle: Ips typographus2011In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 167, no 3, p. 691-699Article in journal (Refereed)
    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.

  • 13.
    Zhao, Tao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Ganji, Suresh
    Schiebe, Christian
    Bohman, Bjorn
    Weinstein, Philip
    Krokene, Paal
    Borg-Karlson, Anna-Karin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Unelius, C. Rikard
    Convergent evolution of semiochemicals across Kingdoms: bark beetles and their fungal symbionts2019In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 13, no 6, p. 1535-1545Article in journal (Refereed)
    Abstract [en]

    Convergent evolution of semiochemical use in organisms from different Kingdoms is a rarely described phenomenon. Tree-killing bark beetles vector numerous symbiotic blue-stain fungi that help the beetles colonize healthy trees. Here we show for the first time that some of these fungi are able to biosynthesize bicyclic ketals that are pheromones and other semiochemicals of bark beetles. Volatile emissions of five common bark beetle symbionts were investigated by gas chromatography-mass spectrometry. When grown on fresh Norway spruce bark the fungi emitted three well-known bark beetle aggregation pheromones and semiochemicals (exo-brevicomin, endo-brevicomin and trans-conophthorin) and two structurally related semiochemical candidates (exo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane and endo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane) that elicited electroantennogram responses in the spruce bark beetle Ips typographus. When grown on malt agar with C-13 D-Glucose, the fungus Grosmannia europhioides incorporated C-13 into exo-brevicomin and trans-conophthorin. The enantiomeric compositions of the fungus-produced ketals closely matched those previously reported from bark beetles. The production of structurally complex bark beetle pheromones by symbiotic fungi indicates cross-kingdom convergent evolution of signal use in this system. This signaling is susceptible to disruption, providing potential new targets for pest control in conifer forests and plantations.

  • 14.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, Paal
    Björklund, Niklas
    Långström, Bo
    Solheim, Halvor
    Christiansen, Erik
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    The influence of Ceratocystis polonica inoculation and methyl jasmonate application on terpene chemistry of Norway spruce, Picea abies2010In: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 71, no 11-12, p. 1332-1341Article in journal (Refereed)
    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.

  • 15.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, Paal
    Hu, Jiang
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Christiansen, Erik
    Björklund, Niklas
    Långström, Bo
    Solheim, Halvor
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Induced Terpene Accumulation in Norway Spruce Inhibits Bark Beetle Colonization in a Dose-Dependent Manner2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 10, p. e26649-Article in journal (Refereed)
    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.

  • 16.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Långström, Bo
    Performance of Tomicus yunnanensis and Tomicus minor (Col., Scolytinae) on Pinus yunnanensis and Pinus armandii in Yunnan, Southwestern China2012In: Psyche, ISSN 0033-2615, p. 363767-Article in journal (Refereed)
    Abstract [en]

    Pine shoot beetles, Tomicus yunnanensis Kirkendall and Faccoli and Tomicus minor Hartig (Col., Scolytinae), have been causing substantial mortality to Yunnan pine (Pinus yunnanensis Franch) in Yunnan, southwestern China, whereas only a few Armand pine (Pinus armandii Franch) were attacked by the beetles. In order to evaluate the suitability of P. armandii as host material for the two Tomicus, adults of both Tomicus were caged on living branches and felled logs of the two pines during shoot feeding and trunk attack phase, respectively. More beetles survived on the living branches of P. yunnanensis than on P. armandii. Tomicus yunnanensis and T. minor produced similar progeny in the logs of the two pines. The sex ratio and developmental period were not affected by host species, but the brood beetles emerging from Armand pine weighed less than those from Yunnan pine, suggesting that P. armandii are less suitable to be host of T. yunnanensis and T. minor.

  • 17.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Solheim, Halvor
    Långström, Bo
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Storm-induced tree resistance and chemical differences in Norway spruce (Picea abies)2011In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 68, no 3, p. 657-665Article in journal (Refereed)
    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.

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