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.
2004
Abstract
The anatomical defense responses in stems of Norway spruce (Picea abies) clones of different resistance to pathogenic fungi were characterized over time and distance from small mechanical wounds or wounds inoculated with the root rot fungus Heterobasidion annosum. Common responses for both treatments included division of ray parenchyma and other cells in the cambial zone, accumulation of phenolic inclusions in ray parenchyma cells, activation of phloem parenchyma (PP) cells, and formation of traumatic resin ducts (TDs) in the xylem. TD formation occurred synchronously from a tangential layer of cells, or symplasmic domain, within the zone of xylem mother cells. TD induction is triggered by a signal, which propagates a developmental wave in the axial direction at about 2.5cm per day. TDs are formed at least 30cm above single inoculations within 16–36days after inoculation. The size and number of TDs is attenuated further away from the inoculation site, indicating a dose-dependent activity leading to TD development. Compared to sterile wounding, fungal inoculation gave rise to more and larger TDs in all clones, and multiple rows of TDs in weak clones. Fungal inoculation also induced the formation of more new PP cells, increasing the number of PP cells in the phloem in the year of inoculation up to 100%. TD and PP cell formation was greater in susceptible compared to resistant clones and after fungal versus sterile inoculation. Potential mechanisms responsible for this variable response are discussed.
Authors
Live Semb Vestgarden Petter Nilsen Gunnar AbrahamsenAbstract
No abstract has been registered
Authors
Halvor B. Gjærum Kåre Arnstein Lye Halvor SolheimAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Nina Elisabeth Nagy Carl Gunnar Fossdal Paal Krokene Trygve Krekling Anders Lönneberg Anders Lønneborg Halvor SolheimAbstract
Polyphenolic parenchyma cells (PP cells) in Norway spruce (Picea abies (L.) Karst.) stem phloem play important roles in constitutive and inducible defenses. To determine whether anatomical and molecular changes in PP cells are correlated with tree resistance, we infected two Norway spruce clones with the pathogenic fungus Ceratocystis polonica (Siem.) C. Moreau. The fungus induced significantly different lesion lengths in the two clones, indicating that one clone was more resistant to the fungus (short lesions) than the other (long lesions). After infection, the cross-sectional area of PP cells and their vacuolar polyphenol bodies increased in the three most recent annual rings of PP cells in both clones. The more resistant clone had larger PP cells with denser polyphenol bodies than the less resistant clone, whereas the less resistant clone accumulated relatively more polyphenols after infection. Compared with the less resistant clone, the more resistant clone contained higher starch concentrations before infection that were reduced more quickly after infection before returning to original values. Low transcript levels of chalcone synthase were detected in uninfected tissues of both clones, but the levels increased dramatically after infection. Transcript levels were higher and peaked 6 days earlier in the more resistant clone than in the less resistant clone. The activity of at least one highly basic peroxidase isoform was greatly enhanced after infection, and this increase occurred earlier in the more resistant clone.
Authors
Steen Koekebakker Gudbrand LienAbstract
No abstract has been registered
Authors
Matthias Koesling Martha Ebbesvik Gudbrand Lien Ola Flaten Paul Steinar Valle Halvard ArntzenAbstract
This study presents empirical insight into organic and conventional cash crop farmers' perceptions of risk and risk management strategies, and identifies socio-economic variables linked to these perceptions. The data originate from a questionnaire survey of farmers in Norway. The results indicate that organic farmers perceived themselves to be less risk aversethan conventional farmers. For both groups, crop prices and yield variability were the two top rated sources of risk, followed by institutional risks. The two groups evaluated risk management strategies quite similarly; favoured strategies weregood liquidity and to prevent and reduce crop diseases and pests. The farmers' evaluation of sources of risk and choice of risk strategies depended onvarious socio-economic variables. The importance of institutional risks implies that policy makers should be cautious about changing policy capriciously and they should consider strategic policy initiatives that give farmers more long-term reliability.
Abstract
The objective of this study was to provide empirical insight into dairy farmers goals, relative risk attitude, sources of risk and risk management responses. The study also examines whether organic dairy farming, leads to important risk sources not experienced in conventional farming and, if so, howthose extra risks are managed. The data originate from a questionnaire survey of conventional (n=373) and organic (n = 162) dairy farmers in Norway. The results show that organic farmers have somewhat different goals than conventional farmers,and that the average organic farmer is less risk averse. Institutional risk was perceived as the most important source ofrisk, independently of conventional or organic production system. Keeping cash on hand wasthe most important strategy to manage risk for all dairy farmers.
Abstract
No abstract has been registered
Abstract
No abstract has been registered