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.
2010
Abstract
Plants use an array of responses to pathogenic infection. Understanding of the underlying defence mechanisms may lead to new strategies for reducing the damage. Our objective here was to study histological and cytological responses in Norway spruce of different ages (from seedlings to mature trees) to infection with several pathogenic organisms (Pythium dimorphum, Ceratocystis polonica and Heterobasidion annosum) and compared them to effects of mechanical wounding. To visualize the reaction on infection/wounding we used different histological staining techniques followed by laser confocal microscopy and TEM. Primary roots of Norway spruce seedlings were infected with P. dimorphum, while mature trees (about 30 years old) were infected with C. polonica, H. annosum and wounded. In seedling roots the hyphae of P. dimorphum penetrated the tissue rapidly and colonized the root within 24 hours. In the infected tissue the lignin concentration doubled within 6 days compared to non infected roots. General response to infection by C. polonica and H. annosum in mature trees was the production of lignosuberised wound periderm, accumulation of polyphenolic aggregates in living parenchyma cells in the phloem and development of traumatic resin ducts in the xylem. Upon wounding, we observed a similar, but less intense response. In conclusion, although we tested fungi belonging to different taxonomical and ecological groups, the responses were similar, differing in intensity and timing of the defence response mainly. The response seems to be similar but dependent on the degree of susceptibility in the individual trees and clones.
Authors
Peder GjerdrumAbstract
This presentation describes the Conifer Heartwood rule, i.e. the constant difference between the square root of the cambial age and the number of heartwood rings. This difference seems to be an inherent property of each species, irrespective of stand or site characteristics, or for location in the tree. When needed, heartwood can be identified by means of IR ecposures or chemical indicators.
Authors
Igor A. Yakovlev Carl Gunnar Fossdal Øystein JohnsenAbstract
Norway spruce (Picea abies (L.) H. Karst.) displays a temperature-dependent epigenetic memory from the time of embryo development, which thereafter influences the timing of bud phenology. As a first step toward unravelling the molecular mechanism behind an epigenetic memory, transcriptional analysis was performed on seedlings from seeds of six full-sib families produced under cold (CE) and warm (WE) embryogenesis temperature regimes. We prepared two suppressive subtracted cDNA libraries, representing genes predominantly expressed after bud set induction in plants from seeds obtained after CE and WE embryogenesis. Sequencing and annotation revealed considerable differences in the transcriptome of WE and CE seedlings. We studied the expression patterns of 32 selected candidate genes using qRT-PCR. Five genes, two transposon-related genes and three with no matching sequence in databases showed differential expression in progeny from CE and WE correlated with family differences. Another step was to study microRNAs (miRNAs), which are endogenous small RNAs exerting epigenetic gene regulatory effects. We tested for their presence and differential expression. We then prepared concatemerized small RNA libraries from seedlings of two fullsib families, originated from seeds developed in a cold or a warm environment. One family showed distinct epigenetic effects whilst the other did not. Sequencing identified 24 novel and 4 conserved miRNAs. Further search and screening of the conserved miRNAs confirmed the presence of 17 additional miRNAs. Most of the miRNAs were targeted to unknown genes. The expression of seven conserved and nine novel miRNAs showed significant differences in transcript levels in the full-sib family showing distinct epigenetic difference in bud set, but not in the non-responding full-sib family. The differential expression of specific miRNAs indicates their putative participation in epigenetic regulation. Putative miRNA targets were studied. These findings may contribute to our understanding of the epigenetic mechanisms underlying adaptive changes acquired during embryogenesis in Norway spruce.
Authors
Harald Bratli Per Magnus Jørgensen Reidar Haugan John Inge JohnsenAbstract
Catapyrenium psoromoides has been discovered in three localities in southern Norway, in Aust-Agder (Åmli), Hedmark (Ringsaker) and Rogaland (Rennesøy). In Aust-Agder and Rogaland it occurred on Ulmus glabra in a wood pasture and an open deciduous forest. In Hedmark the species was found on a calcareous rock outcrop. These finds fill in the distribution gap between Scotland and Sweden and confirm that the species is nemoral to southern boreal with oceanic tendencies. The preference for big, broad-leaved trees in the Atlantic-Mediterranean part of the distribution area is pointed out.
Authors
Nadeem Yaqoob Jan Karlsson Benedicte Riber Albrectsen Halvor Solheim Carl Gunnar FossdalAbstract
Plants are exposed to a variety of pathogens in their natural habitats. To understand the key processes of defense responses in aspen (Populus tremulae) at the transcript level two clones C72 and C23 with differential level of resistance from the SwAsp collection were inoculated with a foliar rust (Melampsora magnusiana Wagnar). Leaf samples were collected from adjacent areas of the inoculation site to examine the long distance (systemic) defense responses at day1, day3 and day14 post treatments. We performed microarray experiments on the biothrophic interaction, on comparison with the healthy controls we found that the two clones respond in a widely different fashion to the rust. Clone C23 showed almost no response to biotroph after 24 hours while clone 72 gave a clear defense response to the pathogen. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) showed a significant differential expression patterns in susceptible and resistant colnes. Chitinase, cinnamic acid reductase and the iaa genes showed signification up-regulation in resistant clone. The level of expression was 5.9 delta threshold cycles in chitinase gene at day14. Data analysis from extracted total phenolics and condensed tannins verify the results of cDNA arrays and qRT-PCR.
Abstract
Today the spruce bark beetle Ips typographus is always univoltine in Northern Europe including Norway and completes development from egg to adult between May and August. Further south in Europe, development is bivoltine with the completion of two generations in most years. A temperature-driven developmental model suggests that by 2070-2100 the voltinism of I. typographus will change dramatically in Norway. If summers become only 2.5°C warmer than today bivoltinism can be expected every single year in the major spruce growing areas in S-Norway. This is likely to have dramatic effects on forestry since two generations per year will give two, instead of one, attack periods each summer. In addition to increasing the number of attacked trees the effect of the attacks may also be more severe, as Norway spruce is more susceptible to beetle attacks later in the summer. However, climate change will probably also change the phenology of Norway spruce and thus its susceptibility to attack by I. typographus and its phytopathogenic fungal associates. We are currently modelling how tree resistance varies with temperature and tree phenology in order to provide more well-founded advice to forest managers on the interaction between bark beetles and tree in a future climate.
Authors
Paal KrokeneAbstract
The interaction between conifers, ophiostomatoid fungi and bark beetles is a key factor in conifer ecosystems worldwide, since combined beetle-fungus attacks may cause massive tree mortality, huge economical losses and landscape-level ecological changes. For more than a century researchers have been arguing about who is responsible for tree mortality in bark beetle attacked trees - the beetles themselves or their associated fungi. As in many such polarized debates the best answer probably lies somewhere in between the extremes. The beetles are obviously central in tree killing, as they are actively selecting suitable host trees, short-circuiting tree defenses by boring straight into the relatively defenseless cambial area, and causing mechanical damage to the phloem. However, ophiostomatoid fungi are equally obvious contributors to tree death since nearly all tree-killing bark beetles are associated with such fungi, these fungi are able to colonize and kill healthy phloem and sapwood far beyond the beetle tunnels, and many fungi can kill healthy trees in experimental mass-inoculations. Thus, the trees are facing a beetle-fungus complex that probably acts synergistically to overwhelm tree defenses. The beetles’ mass-attack strategy is central to the success of the beetle-fungus complex, since multiple attacks deplete tree defenses and speed up tree-killing.
Abstract
Cone and seed insects reduce seed production in seed orchards by feeding on cones and/or seeds and thus cause a lack of seedlings for reforestation. One of the most serious pest species in conifers is the spruce cone worm, Dioryctria abietella. Since 2007, we have used pheromone traps to monitor the flight of this species in Denmark, Finland, Norway and Sweden (and Estonia from 2009). In addition to monitoring, all countries have measured air temperatures in the vicinity of the traps. It is thus possible to correlate flight activity with temperature and temperature sums (accumulated day degrees >5°C). In Sweden cone development has also been registered throughout the monitoring period. Our results show that D. abietella has an extended flight period in Northern Europe, which lasts from late May to late September. Further research is needed to determine if late flying individuals oviposit on shoots or in cones. Increased knowledge about the flight period of D. abietella and how it coincides with temperature and cone development may help us develop better control measures against this important pest.
Authors
Arnold Arnoldussen Eivind SolbakkenAbstract
Soil, composed of minerals, organic material, air and water, performs a number of key environmental, social and economic services that are vital to life. Supplying water and nutrients to plants while at the same time protecting water supplies by storing, bufferingand transforming pollutants. Soil is also an incredible habitat that provides raw materials, preserves our history and limits floods. Without soil, the planet as we know it would not function. However, the importance of soil and the multitude of environmental services that depend on soil properties are not widely understood by society at large. Soil scientists are becoming increasingly aware of the necessity to produce material to raise awareness and educate the general public, policy makers and other scientists of the importance and global significance of soil. This is particularly true of soils in northern latitudes where the impacts of global climate change would be dramatic on both a local and global perspective.
Authors
Markku Husso Erlend NybakkAbstract
Drawing upon the resource-based view (RBV) of the firm and Porter’s five forces, this study examines CEOs’ perceptions of the drivers of competitive advantage in Finnish and Norwegian small- and medium-sized (SME) sawmills. Using qualitative data from CEO interviews and secondary data sources, the results show differences in relevant resources among SME sawmills. In some cases, high-quality raw material is a driver of above-average industry performance, while certain organizational resources, together with correct positioning within an industry, are a way to compensate for a lack of other sources of competitive advantage. Resources such as advanced production technology or a flat organizational structure are essential to diluting the weaknesses of the case companies. Our cases also clarify the important role of intangible resources (e.g., personnel being willing to change).