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.
2002
Abstract
One of our main interests is to learn about the molecular basis of host defense responses, using the coniferous host Norway spruce infected with the pathogen Heterobasidion parviporum as the experimental system. This basidiomycete and the closely related pathogen H. annosum are the major root rot causing pathogens in conifers.To screen host material for differential resistance towards H. parviporum, it is a necessity to quantify the fungal colonization of the host tissues. Therefore, we aimed to develop and compare the sensitivity of a real-time PCR to an ergosterol based method for determining the rate of colonization. We developed a quantitative multiplex real-time PCR procedure that reliably detecting down to 1pg H. parviporum DNA and 1ng host DNA.There was a very high correlation between the fungal-biomass/total-biomass and fungal-DNA/total-DNA rankings obtained with ergosterol and real-time PCR, strengthening the credibility of both methods. The results indicate that this real-time procedure can be a useful method to screen different spruce material for their relative resistance to the pathogen H. parviporum.
Abstract
Determining the level of pathogenic fungi and other microorganisms during colonization of the host is central in phytopathological studies. A direct way to monitor fungal hyphae within the host is microscopic examination, but chitin and ergosterol-levels are commonly used to indirectly measure the amount of fungus present. Recently real-time PCR technology is being used to follow infection agents in host tissues. We study the molecular basis of host defense responses, using the coniferous host Norway spruce infected with the pathogen Heterobasidion parviporum as the experimental system. This basidiomycete and the closely related pathogen H. annosum are the major root rot causing pathogens in conifers. To screen host material for differential resistance towards H. parviporum, it is a necessity to quantify the fungal colonization of the host tissues. Therefore, we aimed to develop and compare the sensitivity of a real-time PCR to an ergosterol based method for determining the rate of colonization, and applied the methods to rank the infection level of the pathogen on the spruce clones 053 and 589. We developed a quantitative multiplex real-time PCR procedure that reliably detecting down to 1pg H. parviporum DNA and 1ng host DNA. There was a very high correlation between the fungal-biomass/total-biomass and fungal-DNA/total-DNA rankings obtained with ergosterol and real-time PCR, strengthening the credibility of both methods. Based on both ergosterol and real-time PCR, it was clear that the clone 053 was hosting more fungal biomass than clone 589. The results indicate that this real-time procedure can be a useful method to screen different spruce material for their relative resistance to the pathogen H. parviporum.
Abstract
This study shows that it is questionable if critical load modelling can contribute in the search for harmful effects of acid deposition on forest health at present. Critical loads for S and N deposition were calculated using the MAGIC and PROFILE models for more than 100 monitoring plots in Norway spruce forest in south-east Norway. The two models gave different results, likely due to differences in the models, including differences in the time spans applied. The PROFILE model gave considerably more plots with exceedance than the MAGIC model. At plots where the CL was exceeded, calcium/aluminium (Ca/Al) ratios in the soil solutions were low. However, very few of these plots had possible harmful values of the Ca/Al-ratio. More than 50 yr seems in most cases to be needed to bring Ca/Al ratios below 1.0. Present deposition was better correlated with measured forest condition variables such as crown condition and needle chemistry, than with modelled exceedance according to any of the two methods. The deposition of S and N was weakly, negatively correlated to foliar concentrations of P and Ca, and positively to foliar N concentrations and crown density.
Abstract
No abstract has been registered
2001
Abstract
Two zone sites, i.e. two circular areas with 50 km radius, were established in southern Norway. The zone sites were centred in Tofte (the location of a major pulp mill) and in Drammen (the site of a major timber yard). From June to October 2000, 66 forest blocks were visited, 65 of which were situated within the zone site areas. Samples were collected from 40 forest blocks, especially from wood attacked by wood boring insects. At 34 forest blocks, trees of Scots pine, Pinus sylvestris, or Norway spruce Picea abies were provided as trap-logs for Monochamus spp. This material will be sampled in the survey of 2001. Some samples were also taken from a wood chip pile and from imported wood material. The total number of wood samples analysed for nematodes were 275. Out of these, 214 samples were collected from forest trees, stumps, timber and logging wastes of P. sylvestris and P. abies. Three samples contained nematodes belonging to the genus Bursaphelenchus, but the Pine Wood Nematode (PWN), B. xylophilus, was not detected. Similarly, this nematode was not detected in the 10 samples of wood chips, or in the 25 samples of imported lumber or in the 26 samples of imported solid wood packing material. In order reach the minimal number of 3000 samples within reasonable time, the number of samples for the next survey season of 2001 needs to be increased drastically. To achieve this, the sampling will continue within the existing zone sites, and be extended into new zone sites to be established in 2001.
Abstract
No abstract has been registered
Abstract
In 1996, 7000 ha of pine forests were defoliated by the pine looper Bupalus piniaria in south-western Sweden.The susceptibility of trees of different defoliation classes (0, 30, 60, 90 and 100% defoliation) to beetle-vectored blue-stain fungi was tested in inoculation experiments.Forty and 120-year-old Scots pine trees were inoculated with `single\", i.e. a few inoculations of Leptographium wingfieldii and Ophiostoma minus, two blue-stain fungi associated with the pine shoot beetle Tomicus piniperda. The young trees were also \"mass\" inoculated with L. wingfieldii at a density of 400 inoculation points per m2 over a 60 cm stem belt.Host tree symptoms indicated that only trees with 90100% defoliation were susceptible to the mass inoculation.Single inoculations did not result in any consistent differences in fungal performance between trees of different defoliation classes, regardless of inoculated species or tree age class.Leptographium wingfieldii produced larger reaction zones than O. minus, and both species produced larger lesions in old than in young trees.As beetle-induced tree mortality in the study area occurred only in totally defoliated stands, mass inoculations seem to mimic beetle-attacks fairly well, and thus seem to be a useful tool for assessing host resistance.As even severely defoliated pine trees were quite resistant, host defence reactions in Scots pine seem to be less dependent on carbon allocation than predicted by carbon-based defence hypotheses.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered