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.
1995
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Halvor SolheimAbstract
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Dan AamlidAbstract
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Dan AamlidAbstract
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Halvor SolheimAbstract
Invasion of lodgepole pine sapwood by blue-stain fungi was followed for 7 weeks afterinfestation by the mountain pine beetle, Dendroctonus ponderosae. During this period all sapwood was heavily stained blue and blue-stain fungi were always isolated close to the front of visible occlusion. Ophiostoma clavigerum and Ophiostoma montium were commonly isolated, both of which are known to be carried in the mycangia of the mountain pine beetle. Ophiostoma montium was most frequently isolated, but when both fungi were present O. clavigerum was always at the lending edge of fungal penetration. On average O. momium trailed 7.3 mm behind O. clavigerum. Other microorganisms were seldom isolated.
Authors
Malcolm M. Furniss Alan E. Harvey Halvor SolheimAbstract
Strial pits on the elytra of unflown Ips pini (Say) carry spores like those of the tree-pathogenic blue-stain fungus Ophiostoma ips (Rumbold) Nannfeldt, yeast, and other fungi, as seen by scanning electron microscopy. O. ips ascospores develop on the walls of pupal chambers in the phloem of infested pines and adhere to newly transformed I. pini adults. Inoculation of severed pine stem sections with body parts excised from beetles washed in water or alcohol produced phloem lesions characteristic of the hypersensitive wound reaction to O. ips. A fungus, characteristic of O. pini, was isolated from infected wood beneath lesions caused by inoculation with head, prothorax, elytron, and alimentary canal. Similar infections and reisolations resulted from inoculations of live trees with an elytron-derived culture that caused necrosis of sapwood radially inward from lesions, and tree mortality when lesions encircled the stem.
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Darrell W. Ross Halvor SolheimAbstract
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Guro BrodalAbstract
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Roots of Picea abies seedlings were inoculated with pathogenic Pythium dimorphum. The ongoing lignification process, the accumulation of lignin, and the distribution of flavanols and condensed tannins (CT), were related to the concurrent visual disease symptoms, hyphal colonization, and cellular changes. The hyphae ramified in both the cortex and the stele within 24 h. Three days after inoculation the concentration of lignin had increased to a level twice that in noninfected tissues. With histochemical staining, the accumulation of lignin and the ongoing lignification were co-located in the inner cortex layer 4-6 days after infection. Comparison of temporal onset of lignification with the timing of the intruding hyphae shows that this defense response occurs too late to effectively prevent the pathogen from spreading. Flavanols and CT were also detected in both infected and noninfected roots.Increased staining of these compounds in infected roots was often detected in the inner cortex. Electron microscopic studies revealed that at least some of these phenolic compounds were localized either as spherules or as a layer appressed to the tonoplast of the central vacuole.