© 2000 Heron Publishing—Victoria, Canada
Changes in volatile terpene and diterpene resin acid composition of resistant and susceptible white spruce leaders exposed
to simulated white pine weevil damage
Elizabeth S. Tomlin (1), Eva Antonejevic (2), Rene I. Alfaro (3) and John H. Borden (2)
1. Department of Biology, University of North Carolina at Greensboro, P.O. Box 26174, Greensboro, NC 27402-6174, USA / 2. Centre for Environmental Biology, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A
1S6, Canada / 3. Pacific Forestry Centre, Canadian Forest Service, 506 West Burnside Road, Victoria, British Columbia V8Z 1M5, Canada / Received September 2, 1999
Summary
Induced (traumatic) resin in white spruce (Picea glauca (Moench) Voss) leaders resistant or susceptible to the white pine weevil (Pissodes strobi Peck) was analyzed for volatile terpenes and diterpene resin acids after simulated white pine weevil damage. Leaders from
331 trees were wounded just below the apical bud with a 1-mm diameter drill, coinciding with the natural time of weevil oviposition
in the spring. Leaders were removed in the fall, and the bark and xylem from the upper and lower regions of the leader extracted
and analyzed by gas chromatography.
Unwounded trees had low amounts of resin in xylem compared with bark. In response to wounding, volatile terpenes and diterpene
resin acids increased in the upper xylem (area of wounding), with resistant trees showing a greater increase than susceptible
trees. Wounding caused monoterpenes in particular to decrease in the lower region of the leader (away from the drilled area)
in greater amounts in susceptible trees than in resistant trees. In response to wounding, the proportion of monoterpene to
resin acid increased in the upper and lower xylem of resistant trees, and slightly increased in the upper xylem of susceptible
trees. Monoterpene-enriched resin is more fluid than constitutive resin, and probably flows more readily into oviposition
cavities and larval mines, where it may kill immature weevils. Loss of resin components in the lower xylem suggested catabolism
and transport of these materials to the site of wounding; however, energetic and regulatory data are necessary to confirm
this hypothesis. This study provides a basis for measuring the ability of a tree to undergo traumatic resinosis that could
be used to screen for resistance to white pine weevil.
Keywords:
host resistance, Picea glauca, Pissodes strobi, traumatic resin.
