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Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2007

Abstract

The root-rot causing fungus Heterobasidion annosum senso lato is the most devastating pathogen of conifers in Europe. This pathogen enter Norway spruce trees trough the roots and colonizes the tree from within, growing as a saprophyte when established within the dead heartwood and acting as a necrotroph when in contact with living host tissue. Twenty percent of the trees in Norwegian spruce stands tend to be infected and this pathogen that can colonize ten meters up inside the tree trunk, decaying the silvicultural most valuable part of the tree. Despite this high incidence of damage the tree has efficient defences against this pathogen and the attack is eventually fought off if present in the bark or living wood. The tree also has a defense against this internal attack (by Heterobasidion established in the heartwood expanding and invading outward toward the living sapwood) by forming a reaction zone; in this case the host defense is directed inwardly by the still living sapwood toward the central colonized wood. We have in the last years studied the host responses to infection in Norway spruce clones at the transcriptional level and found that the speed of recognition and that spatial defense signalling appears to be the hallmarks of trees with high degree of resistance. We strive to study both partners in this pathosystem from a molecular perspective, and are now focusing on the pathogen and what fungal gene-products are being expressed during the colonization of the heartwood compared to those expressed close to the active host defense (reaction zone) using suppressive subtractive hybridization (SSH) followed by Real-Time RT PCR analysis. In addition the colonization profiles were followed on extracted gDNA using quantitative Real-Time PCR.

Abstract

Our goal is to study what gene products (mRNA and proteins) are important for trees in order to fend off pathogens. We are interested in the genetic basis of resistance focusing on the molecular basis of both the local and systemic defence responses of trees. So far we have focused on the host defense against necrotrophic fungi and studied the expression and role of defensins, peroxidases, chitinases, CHS, PAL, CAD and a number of other host gene products. Earlier work using clonal trials (in both Sweden and Norway) indicate that there is a genetic basis for resistance to the root-rot causing fungus Heterobasidion annosum s.l.. We have studied the timing and spatial signaling of the defense response in mature Norway spruce trees as well as seedlings and found that the molecular responses differ. Our studies suggest that the time from wounding and infection to induction of defense-related expression is shorter in resistant spruce clones indicating a more efficient host defense response than in susceptible trees.

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Abstract

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