© 2006 Heron Publishing—Victoria, Canada
Multiplex real-time PCR detection of pathogen colonization in the bark and wood of Picea sitchensis clones differing in resistance to Heterobasidion annosum
William J. A. Bodles (1, 4), Carl-Gunnar Fossdal (2, 4) and Steve Woodward (1, 3, 4)
1. University of Aberdeen, School of Biological Sciences, Plant and Soil Science, Aberdeen AB24 3UU, Scotland, U.K. / 2. Norwegian Forest Research Institute, 1432 Ås, Norway / 3. Corresponding author (s.woodward@abdn.ac.uk) / 4. The three authors contributed equally to this work / Received June 9, 2005; accepted October 16, 2005; published online March 1, 2006
Summary
A quantitative multiplex real-time polymerase chain reaction (PCR) procedure was developed to assess the extent of Heterobasidion annosum (Fr.) Bref. growth in Sitka spruce (Picea sitchensis (Bong.) Carr.) bark and wood and to determine correlations between lesion length and fungal colonization. Based on lesion
length and real-time PCR, the responses of four 3-year-old Sitka spruce clones to inoculation with H. annosum were characterized as showing either resistance or susceptibility to the pathogen. In susceptible clones, the extent of bark
colonization did not differ from the visible length of the bark lesion, whereas lesions were longer than the extent of fungal
colonization in resistant clones. The resistant clones contained considerably less fungal DNA than the susceptible clones,
relative to the amount of host DNA in both the bark and the wood, indicating less resistance and more host cell death in the
susceptible clones following inoculation. In both resistant and susceptible clones, fungal colonization in the wood extended
beyond the visible necrotic lesion in the bark, indicating that host defense responses are weaker in wood than in bark. The
spread of the pathogen in both bark and wood was less in the resistant clones than in the susceptible clones, indicating that
defenses in both bark and wood of the resistant clones were superior to those in the susceptible clones.
Keywords:
laccase, polyubiquitin, Sitka spruce clones, susceptibility.
