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.
2013
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Authors
Heidi Udnes Aamot May Bente Brurberg Anne Marte Tronsmo Sonja Klemsdal Ingerd Skow Hofgaard Guro BrodalAbstract
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Bjørn Arild Hatteland Solveig Haukeland Steffen Roth May Bente Brurberg Ian P. Vaughan William O. C. SymondsonAbstract
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2012
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1. Neodiprion sertifer nucleopolyhedrovirus (NeseNPV) is widely used as a viral bio-insecticide against larvae of the European pine sawfly N. sertifer (Geoff.) (Hymenoptera: Diprionidae), which is one of the most harmful defoliators of pines in Northern Europe. A major obstacle to studying this pathogenic virus in nature is the difficulty of confirming and quantifying the presence of NeseNPV. 2. In the present study, we developed real-time polymerase chain reaction (PCR) primers, based on the caspid gene 39 sequence, for the specific and quantitative detection of NeseNPV. The quantitative real-time PCR (qPCR) assay can detect virus from any substrate tested, including different insect life stages (egg, larval, adult), pine foliage, and litter or ground vegetation. The reproducible detection limit for the real-time assay is 0.013 pg of viral DNA (0.013 × 10−12 g), corresponding to 136 viral genomes or approximately one to seven virus occlusion bodies per sample. 3. qPCR is a specific, quantitative, sensitive, reliable and flexible procedure, and is a good supplement to conventional microscopy- or bioassay-based methods for detection of the virus. We have used qPCR to quantify the level of NeseNPV in samples collected in the field after aerial application of the virus, and demonstrated significantly higher virus levels in sawfly larvae from sprayed areas compared with unsprayed control areas 4 weeks after spraying. 4. This qPCR assay can be used to determine important aspects of the biology of NeseNPV (e.g. virus levels in different insect life stages and in their microhabitats on pine foliage and in forest litter).
Authors
Nadeem Yaqoob Igor A. Yakovlev Paal Krokene Harald Kvaalen Halvor Solheim Carl Gunnar FossdalAbstract
We compared gene expression in Norway spruce secondary phloem (bark) and developing xylem (sapwood) in response to the necrotrophic pathogen Heterobasidion parviporum, wounding and methyl jasmonate (MeJ). The pathogen induced systemic and local up-regulation of PaPX3, PaPX2 and PaChi4 in both bark and sapwood that returned to constitutive levels as the plants recovered from the infection, whereas the local responses to MeJ were similar in both tissues but was longer lasting for PaPX3 and PaChi4. Genes involved in lignin biosynthesis (PaPAL1, PaPAL2, PaC4H3/5 and PaHCT1) were up-regulated locally in the bark in response to pathogen and wounding whereas MeJ induced a similar but stronger local response. The ethylene biosynthesis related transcripts PaACO and PaACS did not increase in response to MeJ treatment or the pathogen, however it increased both locally and systemically as a response to wounding in the sapwood. These results demonstrate that the local and systemic host responses to pathogen infection and wounding largely correspond and reveal striking similarities between the local response to a necrotroph, wounding and MeJ treatment in both bark and living wood.
Authors
Carl Gunnar Fossdal Nadeem Yaqoob Paal Krokene Harald Kvaalen Halvor Solheim Igor A. YakovlevAbstract
Background: NB-LRR resistance proteins are involved in recognizing pathogens and other exogenous stressors in plants. Resistance proteins are the first step in induced defence responses and a better understanding of their regulation is important to understand the mechanisms of plant defence. Much of the post-transcriptional regulation in plants is controlled by microRNAs (miRNA). We examined the expression of five Norway spruce miRNA that may regulate NB-LRR related transcripts in secondary phloem (bark) of resistant Norway spruce after wounding and inoculation with the necrotrophic blue stain fungus Ceratocystis polonica. Results: The plants of this clone recovered from both the pathogen inoculations and wounding alone. We found local and systemic induction of the resistance marker genes PaChi4, PaPAL and PaPX3 indicative of an effective induced host defence response. There were minor local and systemic changes in the expression of five miRNAs and 21 NB-LRRs between healthy and treated plants. Only five putative NB-LRRs (PaLRR1, PaLRR3, PaLRR14, PaLRR15 and PaLRR16) showed significant increases greater than two-fold as a local response to C. polonica. Of all NB-LRRs only PaLRR3, the most highly differentially regulated NB-LRR, showed a significant increase also due to wounding. The five miRNAs showed indications of an initial local and systemic down-regulation at day 1, followed by a later increase up to and beyond the constitutive levels at day 6. However, the initial down-regulation was significant only for miR3693 and miR3705. Conclusions: Overall, local and systemic expression changes were evident only for the established resistance marker genes and PaLRR3. The minor expression changes observed both for the followed miRNAs and their predicted NB-LRR targets suggest that the expression of most NB-LRR genes are maintained close to their constitutive levels in stressed and healthy Norway spruce plants.
Abstract
No abstract has been registered