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.
2006
Authors
Volkmar TimmermannAbstract
Monitoring on the forest officers\" plots in Norway has been running since 1988, with annual assessments carried out by local forest officers. In 2005 they assessed 30277 trees on 557 plots. For 15090 of these trees on 348 plots, there exist complete records of crown condition over the past 18 years. The plots are subjectively selected, mainly in Norway spruce dominated stands, and divided into four development classes. The results from 2005 show a slight increase in mean defoliation of Norway spruce to 16.4 %. There were small, but mostly negative changes in most regions without clear trends in the long term series. In southern Norway, a strong increase in defoliation was observed. Crown colour was improving in the western and northern regions of the country, whereas discolouration was increasing in south-eastern Norway. The mean discolouration was still very low in 2005, with 90 % of the spruce trees having normal, green colour. The mortality rate was low, on the average 3.4 ‰ for all trees. Only few causal agents of crown damage were reported. Data from 18 years of monitoring on the forest officers’ plots reveal some regional patterns for defoliation of spruce in Norway, with western Norway having the lowest mean defoliation through all years, and Mid-Norway the highest. In the other regions, the trends are not so clear with greater fluctuations in defoliation and discolouration.
Abstract
Conidia germination of the root pathogen fungi Fusarium sp. and Cylindrocarpon sp. were followed for up to 96 hours in the presence of border cells from newly germinated Norway spruce. The border cells stimulated the conidium germination of both fungi. We postulate that this may be a part of the defence mechanism of Norway spruce against pathogens. The stimulating agent is unknown The stimulating effect was not seen when border cells originated from plants grown in the presence of aluminium
Authors
Guro BrodalAbstract
A survey of the loose smut frequencies in certified barley seed lots in Norway during 1997"2002 showed that the disease has become more prevalent and has occurred at higher infection frequencies in recent years. Laboratory analyses (embryo method) of barley seeds harvested in 2001 and 2002, including both certified and farm saved seed, showed a large number of infected seed lots with higher than expected infection frequencies. One lot of farm saved seed (cv. Otira) from 2002 had 32% seed infection. Unexpectedly high loose smut infection frequencies recorded in fields sown with carboxin treated barley seed suggest a reduced effectiveness of the fungicide. A seed treatment experiment was conducted in 2002 using both greenhouse and field trials with two infected seed lots (cv. Otira with 14.4% and cv. Fager with 6.9% infected seeds) to evaluate and compare the effect of Fungazil C (carboxin + imazalil) and Premis Robust (triticonazol + imazalil) against loose smut. Fungazil C at normal rates reduced loose smut frequencies by approximately 50% or less. At twice the normal rate, loose smut symptoms were reduced by 60-80%. Premis Robust showed more effective loose smut control, but did not confer complete control.
Abstract
No abstract has been registered
Abstract
The difficulty in sub-culturing biotrophic fungi complicates etiological studies related to the associated plant diseases. By employing species-specific ITS sequence stretches, we used real-time PCR to investigate the spatial colonization profiles of T. areolata and a co-existing Phomopsis species in seedlings and saplings of Norway spruce showing bark necrosis. There was a strong gradient in the colonization level of T. areolata DNA along the lesion length, with the highest DNA amount levels being recorded in the area with dark brown phloem. The separate analysis of bark and wood tissues indicated that the initial spread of the rust to healthy tissues neighbouring the infection site presumably takes place in the bark. A Phomopsis species co-existing together with T. areolata in several cases showed very high DNA levels in the upper part of the lesion outside the brown phloem area, and even in the visually healthy proximal tissues above the lesions. This indicates that this ascomycete has a latent stage during early colonization of Norway spruce shoots. This mode of infection most probably explains the successful co-existence of Phomopsis with a biotrophic rust, as their mutual interest would be to avoid triggering host cell death.
Abstract
Fine root production, respiration, longevity and mortality are the major processes in carbon dynamics of the forest soils. The objective of the present work was to determine fine root biomass, respiration and root longevity. The study was carried out at a ten year-old stand of planted Norway spruce (Picea abies) (a clearcut, dominated by natural regrowth of Scots pine and birch) and three stands of Norway spruce, approximately 30, 60 and 120 years old, during 2001 and 2002. The stands were located at Nordmoen, a plain of sandy deposits in southeast Norway.Root biomass of both trees and understorey vegetation (0-1, 1-2 and 2-5 mm in diameter) in the humus layer and mineral soil horizons (to depth of 60 cm) was sampled by soil coring. Root respiration was performed in situ, by measuring the CO2 of excavated fine roots by using the CIRAS-I portable gas analyser. For the root turnover study, altogether 60 minirhizotrones were installed and images were processed. Root biomass and necromass (g m-2), specific root length (SRL, m g -1), root length density (RLD, cm cm-3), number of root-tips and mean longevity (y) were estimated.Root biomass was 2-3 times higher in the mineral soil than in the humus horizon. Compared with other stands, root biomass, SRL, RLD and the number of root tips were highest in the 30-year-old stand. At the 10 and 120 year-old stands understorey vegetation roots counted for 70 and 40% of total root biomass, respectively. The amount of necromass at 60 year-old stand was about twice as high (45%) compared to other stands.Root respiration (g C/min./g roots) was significantly lowest at 10-year-old stand. Root respiration among 30, 60 and 120 year-old stands was not significantly different, but it was highest in the 60-year-old stand. The respiration varied seasonally, with high peaks during the summer and lower values during the spring and autumn. Fine root longevity of tree and understorey roots at the 10-year-old stand were 1.2 and 1.4 years, respectively.It is concluded that stand age may influence the dynamics of the fine roots. The complexity of influences will be discussed.
Authors
Magnus Karlsson Ari M. Hietala Harald Kvaalen Halvor Solheim Åke Olson Jan Stenlid Carl Gunnar FossdalAbstract
Norway spruce (Picea abies (L.) Karst.) has a natural distribution in the northern parts of Europe and Asia and is economically the most important tree species grown in the Nordic countries. A common threat to Norway spruce is the basidiomyceteous fungus Heterobasidion parviporum Niemelä and Korhonen. H. parviporum mainly attacks Norway spruce, although Siberian fir (Abies sibirica Ledeb.) and Scots pine (Pinus sylvestris L.) occasionally get infected. One obstacle to studying host/pathogen interaction in conifers has been the limited availability of mature clones for controlled inoculations, as genetic variation within the host material and the lack of replicates complicate interpretation of the results. Somatic embryogenesis, rooted cuttings, and tissue cultures may provide solutions for this problem. Tissue cultures from mature Norway spruce trees have been proposed as a possible model system for assessing resistance toward fungal pathogens. Recent data on chitinase isoform activity in the Norway spruce/H. parviporum pathosystem are encouraging; clonal variation was observed in the isoforms affected by inoculation, and the isoforms showing increased band intensity following bark inoculation by H. parviporum were also induced in the inoculated tissue cultures of the corresponding clones. To investigate the biological relevance of tissue cultures in host-pathogen interaction studies, transcript levels of selected host and pathogen genes in tissue cultures of Norway spruce were compared to those in bark of 33-year-old ramets of the same clones upon challenge by the pathogenic fungus H. parviporum. Similar transcript profiles of the pathogen and host genes were observed in both tissues, this supporting the use of tissue cultures as experimental material for the pathosystem. Higher transcript levels of the host genes phenylalanine ammonia lyase, peroxidase, and glutathione-S-transferase were observed in the more resistant clone #589 than in the less resistant clone #409 during the early stages of colonization. The most striking difference between the spruce clones was related to gene transcript levels of a class IV chitinase, which showed a continuous increase in clone #409 over the experimental period, with a possible association of this gene product to programmed cell death. Several of the fungal genes assayed were differentially expressed during colonization, including putative glutathione-S-transferases, laccase, cellulase, cytochrome P450 and superoxide dismutase genes. The transcriptional responses suggest an important role for the antioxidant systems of both organisms.
Abstract
The minirhizotron technique provides the opportunity to perform in situ measurements of fine root dynamics and obtain accurate estimates of fine root production and turnover. The objective of the present work was to determine the fine root longevity and mycorrhization in a Norway spruce chronosequence. The study was carried out on four stands of planted Norway spruce (Picea abies), approximately 10, 30, 60 and 120 years old, during 2001 and 2002. The stands were located at Nordmoen, a plain of sandy deposits in southeast Norway (60o15 N, 11o06 E). For the root turnover study, altogether 60 minirhizotrones were installed and images were processed.Individual fine roots were identified, their mycorrhization assessed, appearance and possible disappearance dated, and growth in length measured. The data set was subjected to a survival analysis, using a Kaplan-Meier product-limit approach. The minirhizotron samples were stratified according to stand age class, and Coxs F-test was used to analyze differences in survival estimates. The analysis may also be extended to consider other covariates such as tree species (spruce, pine or birch), understory vegetation, or soil depth. Typical survival function estimates will be presented, and the influence of stand age on the mycorrhization and the dynamics of the fine roots will be discussed.
Authors
Joha W. Grobbelaar Michael J. Wingfield P. Bloomer Halvor Solheim Brenda D. WingfieldAbstract
No abstract has been registered
Abstract
No abstract has been registered