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.
2013
Abstract
The outcome of a compatible mycorrhizal interaction is different from that in a compatible plant–pathogen interaction; however, it is not clear what mechanisms are used to evade or suppress the host defence. The aim of this work is to reveal differences between the interaction of Norway spruce roots to the pathogen Ceratocystis polonica and the ectomycorrhizal Laccaria bicolor, examine if L. bicolor is able to evade inducing host defence responses typically induced by pathogens, and test if prior inoculation with the ectomycorrhizal fungus affects the outcome of a later challenge with the pathogen. The pathogen was able to invade the roots and caused extensive necrosis, leading to seedling death, with or without prior inoculation with L. bicolor. The ectomycorrhizal L. bicolor colonised primary roots of the Norway spruce seedlings by partly covering, displacing and convoluting the cells of the outer root cortex, leaving the seedlings healthy. We detected increased total peroxidase activity, and staining indicating increased lignification in roots as a response to C. polonica. In L. bicolor inoculated roots there was no increase in total peroxidase activity, but an additional highly acidic peroxidase isoform appeared that was not present in healthy roots, or in roots invaded by the pathogen. Increased protease activity was detected in roots colonised by C. polonica, but little protease activity was detected in L. bicolor inoculated roots. These results suggest that the pathogen efficiently invades the roots despite the induced host defence responses, while L. bicolor suppresses or evades inducing such host responses in this experimental system.
Authors
Ivano Brunner Mark R. Bakker Robert G. Björk Yasuhiro Hirano Martin Lukac Xavier Aranda Isabella Børja Toril Eldhuset Heljä-Sisko Helmisaari Christophe Jourdan Bohdan Konôpka Bernat Claramunt López Carolina Miguel Pérez Hans Persson Ivika OstonenAbstract
Background and Aims: Forest trees directly contribute to carbon cycling in forest soils through the turnover of their fine roots. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values. Methods: We compiled available European data and applied various turnover rate calculation methods to the resulting database. We used Decision Matrix and Maximum-Minimum formula as suggested in the literature. Results: Mean turnover rates obtained by the combination of sequential coring and Decision Matrix were 0.86 yr−1 for Fagus sylvatica and 0.88 yr−1 for Picea abies when maximum biomass data were used for the calculation, and 1.11 yr−1 for both species when mean biomass data were used. Using mean biomass rather than maximum resulted in about 30 % higher values of root turnover. Using the Decision Matrix to calculate turnover rate doubled the rates when compared to the Maximum-Minimum formula. The Decision Matrix, however, makes use of more input information than the Maximum-Minimum formula. Conclusions: We propose that calculations using the Decision Matrix with mean biomass give the most reliable estimates of root turnover rates in European forests and should preferentially be used in models and C reporting.
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Authors
Berit Nordskog Jan Netland Håvard Eikemo Halvard Hole Tor-Einar Skog Annette Folkedal Schjøll Guro BrodalAbstract
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Authors
Aruppillai Suthaparan Arne Stensvand Knut Asbjørn Solhaug Nils Bjugstad David Gadoury Hans Ragnar GislerødAbstract
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2012
Abstract
Winter damage caused by frost is frequently observed on common ash (Fraxinus excelsior) in Norway. In spring 2007, extensive winter damage most likely camouflaged ash dieback caused by Chalara fraxinea. In 2008, ash dieback caused by C. fraxinea had spread to large areas in the southern part of Norway. The disease was widespread in forests and nurseries, but also on roadside trees, and in gardens and parks. In 2009, the disease had spread to new areas; about 30 km into Rogaland county in southwestern Norway and also further into some valleys in southeastern Norway.
Authors
Carl Gunnar Fossdal Nadeem Yaqoob Benedicte Riber Albrectsen Halvor SolheimAbstract
Aspen trees are exposed to a range of attackers and employ varied strategies to reduce their impact. The diversity of responses may have importance for resistance properties at the stand level, and justifies the search for varied defensive strategies in natural populations. We used transcriptomic tools to evaluate diverse responses at the gene activity level in Populus tremula in response to wounding, and to inoculation with two pathogenic fungi (Melampsora magnusiana vs Ceratocystis sp.) that differ in life style (biotroph vs necrotroph) and host tissue requirement (live leaf vs dead wood tissues). Two aspen genotypes from the SwAsp collection with differences in growth and phenolic composition were used to study differences in resistance properties. High defence gene induction, high growth and elevated defence properties toward the biotroph appeared to support each other in this study exemplified in the more resistant SwAsp clone, whereas the more susceptible SwAsp clone was much less responsive to infections, and displayed more symptoms when infected with M. magnusiana. Interestingly, in the more resistant clone wounding gave greater systemic activity of selected candidate genes than when combined with the necrotroph, suggesting that this pathogen has some ability to suppress the induction or translocation of the systemic defence signal in this particular clone.