© 2003 Heron Publishing—Victoria, Canada
Inducible anatomical defense responses in Norway spruce stems and their possible role in induced resistance
Paal Krokene (1, 2), Halvor Solheim (1), Trygve Krekling (3) and Erik Christiansen (1)
1. Norwegian Forest Research Institute, Høgskoleveien 12, N-1432 Ås, Norway / 2. Author to whom correspondence should be addressed (paal.krokene@skogforsk.no) / 3. Institute of Chemistry and Biotechnology, EM, Agricultural University of Norway, Ås, Norway / Received April 15, 2002; accepted August 30, 2002; published online January 31, 2003
Summary
Norway spruce (Picea abies (L.) Karst.) trees were preinoculated with a sublethal dose of the blue-stain fungus Ceratocystis polonica Siem. (C. Moreau) 1 to 52 weeks before they were mass inoculated with the same fungus. Trees pretreated 1 week before mass
inoculation had similar, severe symptoms of fungal infection as the control trees. Pretreatment 3, 6 or 9 weeks before mass
inoculation resulted in effective protection of the trees, reducing pathogenic symptoms by 63–90% relative to the control
trees, whereas pretreatment 52 weeks before mass inoculation gave intermediate protection (44–71% reduction in symptoms).
Thus, pretreatment induced resistance to the blue-stain fungus in Norway spruce by a process that requires more than 1 week
to become activated and protects trees for at least one year after pretreatment. Pretreatment induced formation of traumatic
resin ducts (TDs) in the sapwood and swelling and proliferation of polyphenolic parenchyma cells (PP cells) in the phloem.
Trees pretreated 3–9 weeks before mass inoculation had more TDs and showed greater swelling of existing PP cells than control
trees or trees pretreated 1 week before mass inoculation. We conclude that induced disease resistance in Norway spruce is
probably associated with PP cell activation and TD induction, because resistance was enhanced within the same time frame as
the induction of these defense responses.
Keywords:
Ceratocystis polonica, inducible defenses, Picea abies, polyphenolic parenchyma cells, traumatic resin ducts.
