title: Exogenous application of methyl jasmonate elicits defenses in Norway spruce (Picea abies) and reduces host colonization by the bark beetle Ips typographus.
abstract: The terpenoid and phenolic constituents of conifers have been implicated in protecting trees from infestation by bark beetles and phytopathogenic fungi, but it has been difficult to prove these defensive roles under natural conditions. We used methyl jasmonate, a well-known inducer of plant defense responses, to manipulate the biochemistry and anatomy of mature Picea abies (Norway spruce) trees and to test their resistance to attack by Ips typographus (the spruce bark beetle). Bark sections of P. abies treated with methyl jasmonate had significantly less I. typographus colonization than bark sections in the controls and exhibited shorter parental galleries and fewer eggs had been deposited. The numbers of beetles that emerged and mean dry weight per beetle were also significantly lower in methyl jasmonate-treated bark. In addition, fewer beetles were attracted to conspecifics tunneling in methyl jasmonate-treated bark. Stem sections of P. abies treated with methyl jasmonate had an increased number of traumatic resin ducts and a higher concentration of terpenes than untreated sections, whereas the concentration of soluble phenolics did not differ between treatments. The increased amount of terpenoid resin present in methyl jasmonate-treated bark could be directly responsible for the observed decrease in I. typographus colonization and reproduction.
authors.affiliation: Division of Insect Biology Department of Environmental Science, Policy and Management University of California, 140 Mulford Hall, Berkeley, CA, 94720, USA. erbilgin@nature.berkeley.edu
authors.forename: Nadir
authors.initials: N
authors.lastname: Erbilgin
authors.forename: Paal
authors.initials: P
authors.lastname: Krokene
authors.forename: Erik
authors.initials: E
authors.lastname: Christiansen
authors.forename: Gazmend
authors.initials: G
authors.lastname: Zeneli
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gershenzon
mesh_terms: D000085:Acetates; D000818:Animals; D001517:Coleoptera / Q000502:physiology*; D003517:Cyclopentanes; D054883:Oxylipins; D028222:Picea / Q000469:parasitology* / Q000502:physiology; D024301:Plant Bark / Q000469:parasitology*; D010937:Plant Growth Regulators; D012116:Resins, Plant / Q000737:chemistry; D013729:Terpenes / Q000032:analysis
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D054883:Oxylipins; D010937:Plant Growth Regulators; D012116:Resins, Plant; D013729:Terpenes; C072239:methyl jasmonate