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
Determining the level of pathogenic fungi and other microorganisms during colonization of the host is central in phytopathological studies. A direct way is to monitor fungal hyphae by microscopic examination, but indirect chitin and ergosterol-based assays have been among the most applied methods in determining fungal biomass within host tissues. Recently real-time technology is increasingly receiving attention as a way to follow infection agents in host tissues.We study the molecular basis of host defense responses, using the coniferous host Norway spruce (Picea abies) infected with the basidomycete Heterobasidion annosum as the experimental system. This basidiomycete is the major root rot causing pathogens in conifers of all age classes.In order to screen host material for differential resistance towards H.annosum for both scientific and commercial reasons, it is a necessity to reliably quantify the fungal colonization of the host tissues. Therefore, the aim of this study was to develop and compare the sensitivity of a real-time PCR assay to an ergosterol based method for determining the rate of colonization by H.annosum in inoculated spruce material. We also applied the methods to rank the infection level of the pathogen on the spruce tissue culture clones.We were able to develop a quantitative multiplex real-time PCR procedure that reliably detecting down to 1pg H.annosum DNA and 1ng host DNA in DNA extracted from infected tissues. 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 respectively, strengthening the credibility of both methods.Based on both ergosterol and real-time PCR, it was clear that some spruce clones were faster and more heavily infected than others. These results indicate that both ergosterol and this real-time procedure can be useful methods to screen different spruce material for their relative resistance to the pathogen H.annosum.
2001
Abstract
No abstract has been registered
Authors
Isabella BørjaAbstract
No abstract has been registered
Authors
Toril Drabløs Eldhuset Berit Swensen Heleen A. de Wit Nina Davidsen Gro WollebækAbstract
No abstract has been registered
Authors
Jenny Fäldt Halvor Solheim Bo Långström Anna-Karin Borg-KarlsonAbstract
No abstract has been registered
Authors
Harald Kvaalen Erik Christiansen Øystein Johnsen Halvor SolheimAbstract
Genetic associations between initiation of embryogenic tissue (ET) and susceptibility to the phytopathogenic fungi Ceratocystis polonica (Siem.) C. Moreau and Heterobasidion annosum (Fr.) Bref. in Norway spruce have been studied by initiating ET from zygotic embryos of mature seeds collected from 19 clones tested for susceptibility to the pathogens in a clonal field trial.Initiation frequencies varied significantly among clones (families), ranging from 12 to 56%. The family variance component accounted for more than 40% of the total variance in initiation frequency of ET. The estimates of broad-sense heritability of fungus susceptibility of the clones ranged from 0.12 for length of phloem necrosis after low-density inoculation with H. annosum to 0.55 for blue-stained sapwood after mass inoculation with C. polonica.None of the susceptibility measures showed any phenotypic correlation with initiation of embryogenic tissue. Genetic correlations and their standard errors were estimated by bootstrapping. Two measures of fungal susceptibility correlated genetically with initiation of ET; estimated at 0.58 for lesion length after inoculation with C. polonica and 0.29 for H. annosum lesion length. A better measure of susceptibility, blue-stained sapwood following inoculation with C. polonica, was not correlated with initiation of ET.
Abstract
Air pollution induced changes in pine needle chemistry were observed at sample sites in the surroundings of the Pechenganikel smelter. Close to the smelter, elevated concentrations of Ni, Cu and S were found (Ni: 0.7-1 mmol/kg, CU: 0.4-0.5, and S 40-60 mmol/kg) Close to the pollution source needles were enriched in Ni and Cu by needle age. Correlation and principal component analyses show that changes in the element composition of pine needles depended on air pollution and on natural factors as well. The contribution from air pollution increased with needle age. Besides direct input of pollutants from atmosphere, soil contamination and nutritional disturbance contributed significantly to the observed changes.
Abstract
Epiphytic lichen vegetation on birch stems was studied in the border areas between Norway and Russia. The area is heavily influenced by sulphur dioxide pollution emitted from Russian nickel smelters.Hypogymnia physodes and Melanelia olivacea were the two most abundant lichen species on birch stems in the investigated area. However, the coverage of H. physodes and M. olivacea was clearly reduced in parts of the investigated area. The lichen vegetation increased with increasing distance from the pollution source, i.e. from a lichen desert to normal background levels. A different pattern of occurrence of the two lichen species was observed.
2000
Abstract
No abstract has been registered
Abstract
A rapid and sensitive method was developed to discriminate between Seiridium cardinale and Seiridium cupressi, the fungi causing severe cankers on common cypress in the Mediterranean area. The method amplified sequence variants in the ITS2 region of ribosomal DNA using the polymerase chain reaction (PCR), followed by polyacrylamide gel electrophoresis, to reveal single-strand conformation polymorphism (SSCP) between the two species. The greatest separation pattern was obtained with a gel matrix containing 7-10% formamide and 3-5% glycerol under optimized running conditions, which were found to be 30-40 V at 4-5 degrees C for 4-8 h. Sequence homology among isolates within each of the two species caused no mobility shifts, with all isolates displaying the same migration pattern. A few base differences between S. cardinale and S. cupressi caused markedly different migration patterns, allowing differentiation of the two pathogens. Differences between these fungi at the genetic level are consistent with known data on morphological, physiological and pathogenic characteristics. SSCP analysis constitutes a rapid and easy-to-perform method by which to recognize and distinguish closely related organisms, and has considerable potential for use in diagnosis and taxonomy.