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.
2008
Authors
Berit Nordskog David M. Gadoury May Bente Brurberg Tor Håkon Sivertsen R. Kennedy Arne HermansenAbstract
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The difficulty in subculturing biotrophic fungi complicates etiological studies related to the associated plant diseases. By employing internal transcribed spacer rDNA-targeted quantitative real-time polymerase chain reaction, we now show that the heteroecious rust Thekopsora areolata, commonly associated in natural conditions to sapling shoots and cones of Norway spruce and leaves of wild bird cherry, frequently infects nurserygrown seedlings of the conifer. A spatial sampling scheme was used to investigate seedlings and saplings of Norway spruce showing phloem necrosis: the highest concentration of DNA of T. areolata was recorded in the area with necrotic phloem. The separate analysis of bark and wood tissues suggested that the initial spread of the rust to healthy tissues neighboring the infection site takes place in the bark. A Phomopsis species found to coexist with T. areolata in several seedlings showed very high DNA levels in the upper part of the lesion, and even in the visually healthy proximal tissues above the lesions, which indicates that the ascomycete, most probably a secondary invader following primary infection by T. areolata, has a latent stage during early host colonization. We hypothesize that this hemibiotrophic mode of infection contributes to the successful coexistence of Phomopsis with a biotrophic rust.
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We investigated whether the stand age affects the life span of tree and understory fine roots (<1mm) in three Norway spruce (Picea abies) stands: 30, 60 and 120-yr-old. In each stand 9 minirhizotrons were installed and images were collected once in a month throughout the growing season during the three years. Norway spruce fine roots in the 30-yr old stand had a life span 401 ± 27 and 341 ± 68 days, and understory 409 ± 162 and 349 ± 142 days, estimated by using the Kaplan Meier survival analysis (KM) and Weibull distribution, respectively...
Authors
Nenad Kea Halvor SolheimAbstract
No abstract has been registered
Authors
Halvor SolheimAbstract
Climate change may influence in a worse manner for the forests in various ways. Some pathogens may increase their importance and new may arrive. Root and butt rot is the most serious problem in Norway spruce forests. In mean more than every fourth tree is infested when harvested. Dryer summers may give increased frequency of rot caused by Heterobasidion. In addition Armillaria spp may gain change in weather condition both as root rot and in connection with a syndrome together with drought and bark beetles. More unstable winter climate may give increase of Gremmeniella attack on Scots pine. Longer and warmer growth season will give many pathogens better condition. Among those is Ophiostoma novo-ulmi causing Dutch elm disease which is lasting in south eastern Norway at a rather low frequency and the volume of elm is not lower than for 15 years ago. In which way the newly introduced Chalara fraxinea will behave in Norway is uncertain, but a better growth season will probably also influence on the possibility to be spread all over Norway where ash are growing.
Authors
Rimvydas Vasaitis Bo Långström Halvor Solheim Ylva Persson Katarina Ihrmark Jan StenlidAbstract
Ips typographus is economically most important insect pest of mature spruce in Eurasia. Normally, it prefers to reproduce in dead and/or dying trees, but following large-scale storm disturbances, its outbreaks kill waste areas of living stands. One factor triggering such epidemics is a surplus of broken and uprooted trees with non-existent, or weak, defence....
Abstract
No abstract has been registered