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  • Leptographium terebrantis  (1)
  • Terpenes  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Interaction of pre-attack and induced monoterpene concentrations in host conifer defense against bark beetle-fungal complexes (1995)
    Springer
    Oecologia 102 (1995), S. 285-295 
    Details
    ISSN: 1432-1939
    Keywords: Induced resistance ; Plant-insect interactions ; Insect-fungal interactions ; Terpenes ; Bark beetles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two pine species (Pinus resinosa, P. banksiana) responded to inoculation with fungi carried by bark beetles by rapidly increasing monoterpene concentrations at the entry site. Changes in total monoterpenes were more pronounced than changes in proportionate compositions. The extent and rate of host response was affected by fungal species, the viability of the inoculum, and host tree species. In general, host responses were highest to fungi that are phytopathogenic and consistently associated with the major bark beetles in the study region. Simple mechanical wounding cannot account for the observed allelochemical changes, as aseptic inoculations elicited only minor reactions. Similarly, inoculation with autoclaved inviable fungi generally elicited intermediate responses, suggesting that both structural and metabolic fungal properties are important. Responses by jack pine, P. banksiana, were generally more rapid and variable than those of red pine, P. resinosa. Dose-toxicity experiments with synthetic compounds demonstrated that monoterpene concentrations present in vivo only a few days after simulated attack are lethal to most beetles. Constitutive (pre-attack) monoterpene levels can also exert some toxicity. Because bark beetles engage in pheromone-mediated mass attacks that can deplete host defenses, constitutive monoterpene levels, while a necessary early phase of successful plant defense, appear insufficient by themselves. Such interactions between constitutive and induced defense chemistry may be important considerations when evaluating general theories of plant defense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329795
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Combined chemical defenses against an insect-fungal complex (1996)
    Springer
    Journal of chemical ecology 22 (1996), S. 1367-1388 
    Details
    ISSN: 1573-1561
    Keywords: Insect-fungal interactions ; host selection ; plant stress ; forest decline ; monoterpenes ; phenolics ; bark beetles ; Ophiostoma ips ; Ips pini ; Dendroctonus valens ; Hylastes porculus ; Leptographium procerum ; Leptographium terebrantis ; Pinus resinosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This study considered how host plant allelochemicals may contribute to defense against insects and fungi that jointly colonize the subcortical tissues of trees, the relative roles of constitutive and inducible chemistry in these defenses, and how the actions of two different feeding guilds might be interrelated. Our model consisted of the coniferous treePinus resinosa, the root- and lower stem-colonizing beetlesHylastes porculus andDendroctonus valens, and their associated fungiLeptographium procerum andL. terebrantis, and the stem-colonizing bark beetleIps pini and its associated fungusOphiostoma ips. In a novel bioassay, extracts from reaction tissue elicted by wound inoculation withL. terebrantis were more repellent to beetles than were similar extracts from constitutive or mechanically wounded tissue. The effect on beetle behavior was more pronounced in nonpolar extracts, which contain mostly monoterpenes, than in polar extracts, which contain mostly phenolics. Synthetic monoterpenes at concentrations present in the various tissues exerted similar effects and were likewise repellent in dose-response experiments. Growth ofL. procerum andL. terebrantis was inhibited by polar extracts from constitutive and reaction tissue. Inhibition was higher in wounded than control tissue, but the inhibition response did not vary with the type of wounding. Synthetic monoterpenes strongly inhibited spore germination and mycelial growth of both fungi. Colonization of red pine roots byLeptographium spp. altered the subsequent effects of extracts of stem phloem tissue onI. pini. These effects varied with host condition. Beetles preferred extracts from constitutive stem phloem tissue of healthy trees to that of root-diseased trees. However, extracts from reaction tissues of healthy trees were more repellent toI. pini than were the reaction tissues of root-diseased trees. The implications of these results to plant defense against insect-fungal complexes and interactions among different feeding guilds are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02027719
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    Paper (German National Licenses)
    Fulltext
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