© 2007 Heron Publishing—Victoria, Canada
Physical and chemical responses of Sitka spruce (Picea sitchensis) clones to colonization by Heterobasidion annosum as potential markers for relative host susceptibility
Steve Woodward (1, 2), Simone Bianchi (3), William J. A. Bodles (1), Liz Beckett (1) and Marco Michelozzi (2, 3)
1. University of Aberdeen, School of Biological Sciences, Department of Plant and Soil Science, Cruickshank Building, St. Machar
Drive, Aberdeen AB24 3UU, U.K. / 2. Corresponding authors (s.woodward@abdn.ac.uk, marco.michelozzi@igv.cnr.it) / 3. Istituto di Genetica Vegetale – Consiglio Nazionale delle Ricerche, Via Madonna del Piano, 50019 Sesto Fiorentino, Firenze,
Italy / Received September 14, 2006; accepted March 16, 2007; published online September 4, 2007
Summary
Forty-one 2-year-old clones of
Picea sitchensis (Bong.) Carr. from three full-sib families (14 clones from each of two families and 13 clones from a third family) were either
wounded and inoculated with an isolate of
Heterobasidion annosum (Fr.) Bref. or wounded without inoculation. Lesion lengths on the inner bark from the point of inoculation varied among clones
35 days after treatment. There was no relationship between lesion length and relatedness within families. Two clones (21342
and 25202) with the shortest lesions, tentatively designated as less susceptible to
H. annosum, and two clones (21176 and 27166) with the longest lesions, designated more susceptible, were selected for comparison of
host anatomical and chemical responses to infection. The position and structure of the ligno-suberized boundary zone (LSZ)
in the bark of the clones suggested that the less susceptible clones formed thicker layers of suberized cells in the LSZ following
wounding plus inoculation. No LSZ was observed in two ramets of the more susceptible Clone 27166 following wounding and inoculation
with
H. annosum.
Compared with more susceptible genotypes, clones of P. sitchensis with low susceptibility to H. annosum had high relative proportions of (+)-α-pinene, (–)-β-pinene and one unidentified terpene constituent (Unknown-15) in cortical
resin sampled 25 cm from the lesions. In contrast, more susceptible clones had higher relative proportions of (–)-limonene,
Unknown-16, Unknown-18 and Unknown-19. In the secondary resin produced in bark tissues surrounding the lesions, proportions
of several monoterpene constituents varied; these changes included a decrease in the relative amount of β-phellandrene and
corresponding small increases in some minor constituents. The concentrations of the monoterpenes, except a few minor constituents,
increased in the infected tissues. Wounding plus inoculation with H. annosum resulted in varied monoterpene responses, with distinct differences between less susceptible and more susceptible clones.
In less susceptible clones, Unknown-19 increased following wounding plus inoculation, whereas in more susceptible clones,
concentrations of δ-3-carene and Unknown-13 and Unknown-16 increased. Differences in both constitutive and induced resin monoterpene
profiles may provide useful markers for resistance to H. annosum in selection and breeding programs.
Keywords:
δ-3-carene, lesions, ligno-suberized boundary zone, monoterpenes, resin, resistance.
