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.
2018
Forfattere
Roger Holten Frederik Bøe Marit Almvik Marianne Stenrød Mats Larsbo Nicholas Jarvis Ole Martin EkloSammendrag
No abstract has been registered
Forfattere
Roger Holten Frederik Bøe Marit Almvik Sheela Katuwal Marianne Stenrød Mats Larsbo Nicholas Jarvis Ole Martin EkloSammendrag
Limited knowledge and experimental data exist on pesticide leaching through partially frozen soil. The objective of this study was to better understand the complex processes of freezing and thawing and the effects these processes have on water flow and pesticide transport through soil. To achieve this we conducted a soil column irrigation experiment to quantify the transport of a non-reactive tracer and the herbicide MCPA in partially frozen soil. In total 40 intact topsoil and subsoil columns from two agricultural fields with contrasting soil types (silt and loam) in South-East Norway were used in this experiment. MCPA and bromide were applied on top of all columns. Half the columns were then frozen at −3 °C while the other half of the columns were stored at +4 °C. Columns were then subjected to repeated irrigation events at a rate of 5 mm artificial rainwater for 5 h at each event. Each irrigation was followed by 14-day periods of freezing or refrigeration. Percolate was collected and analysed for MCPA and bromide. The results show that nearly 100% more MCPA leached from frozen than unfrozen topsoil columns of Hov silt and Kroer loam soils. Leaching patterns of bromide and MCPA were very similar in frozen columns with high concentrations and clear peaks early in the irrigation process, and with lower concentrations leaching at later stages. Hardly any MCPA leached from unfrozen topsoil columns (0.4–0.5% of applied amount) and concentrations were very low. Bromide showed a different flow pattern indicating a more uniform advective-dispersive transport process in the unfrozen columns with higher con- centrations leaching but without clear concentration peaks. This study documents that pesticides can be pre- ferentially transported through soil macropores at relatively high concentrations in partially frozen soil. These findings indicate, that monitoring programs should include sampling during snow melt or early spring in areas were soil frost is common as this period could imply exposure peaks in groundwater or surface water.
Sammendrag
No abstract has been registered
Sammendrag
Pathogenic soft rot Enterobacteriaceae (SRE) belonging to the genera Pectobacterium and Dickeya cause diseases in potato and numerous other crops. Seed potatoes are the most important source of infection, but how pathogen-free tubers initially become infected remains an enigma. Since the 1920s, insects have been hypothesized to contribute to SRE transmission. To validate this hypothesis and to map the insect species potentially involved in SRE dispersal, we have analyzed the occurrence of SRE in insects recovered from potato fields over a period of 2 years. Twenty-eight yellow sticky traps were set up in 10 potato fields throughout Norway to attract and trap insects. Total DNA recovered from over 2,000 randomly chosen trapped insects was tested for SRE, using a specific quantitative PCR (qPCR) TaqMan assay, and insects that tested positive were identified by DNA barcoding. Although the occurrence of SRE-carrying insects varied, they were found in all the tested fields. While Delia species were dominant among the insects that carried the largest amount of SRE, more than 80 other SRE-carrying insect species were identified, and they had different levels of abundance. Additionally, the occurrence of SRE in three laboratory-reared insect species was analyzed, and this suggested that SRE are natural members of some insect microbiomes, with herbivorous Delia floralis carrying more SRE than the cabbage moth (Plutella xylostella) and carnivorous green lacewing larvae (Chrysoperla carnea). In summary, the high proportion, variety, and ubiquity of insects that carried SRE show the need to address this source of the pathogens to reduce the initial infection of seed material.
Sammendrag
Bark beetles and their symbiotic bluestain fungi kill more trees than all other natural factors and cause great economic losses in Norway spruce and other conifers. The tree's natural defenses are the most important factor maintaining bark beetle-fungus complexes at low, endemic levels. Spraying Norway spruce trees with the plant hormone methyl jasmonate (MeJA) primes tree defenses without eliciting notable induced defenses, but enables the trees to respond much more quickly and strongly when challenged by bark beetles or fungi several weeks after treatment. This phenomenon, known as defense priming, is a form of acquired resistance that enables cost-effective and vigorous defense responses. In field experiments with 50-year-old clonal spruce trees terpene concentrations in the bark increased 60-fold within 24 h after mechanical wounding of MeJA primed trees, compared with a 13-fold increase in unprimed control trees. We also observed altered transcriptional patterns in primed trees using Illumina deep transcriptome sequencing. When wounded, primed trees launched vigorous induced defenses with significant differential regulation of gene transcripts, such as those involved in phenylpropanoid synthesis leading to lignification. Resistance-like genes, such as the NB-LRR coding genes, are also more rapidly induced in primed than in unprimed trees. Transcriptome results from primed but unwounded trees indicate an alteration in the state of the chromatin, resembling changes associated with the activity of the epigenetic machinery creating long-lasting epigenetic marks. We do not know yet how long the primed state is activated in Norway spruce, but our data so far indicate that it may last for at least 3 years.
Sammendrag
1 The European spruce bark beetle Ips typographus is a damaging pest on spruce in Europe. Beetle interactions with tree species originating outside the natural range of the beetle are largely unknown and may be unpredictable because trees without a co-evolutionary history with the beetle may lack effective defences. 2 The terpenoid composition and breeding suitability for I. typographus of the historic host Norway spruce Picea abies were compared with two evolutionary naïve spruces of North American origin that are extensively planted in North-West Europe: Sitka spruce Picea sitchensis and Lutz spruce Picea glauca x lutzii. 3 The bark of all three species had a similar chemical composition and similar levels of total constitutive terpenoids, although Norway spruce had higher total induced terpenoid levels. 4 Beetles tunnelling in the three spruce species produced similar amounts of aggregation pheromone. Controlled breeding experiments showed that I. typographus could produce offspring in all three species, with a similar offspring length and weight across species. However, total offspring production was much lower in Sitka and Lutz spruce. 5 Overall, the results of the present study suggest that I. typographus will be able to colonize Sitka and Lutz spruce in European plantations and in native spruce forests in North America if introduced there.
Sammendrag
No abstract has been registered
Sammendrag
Fusarium head blight and seedling blight, both caused by Fusarium spp. and Microdochium spp., and glume blotch caused by Parastagonospora nodorum, are important diseases in wheat. In Norway, wheat seed lots are routinely analysed for infestation by these pathogens using traditional methods (plating grain on PDA, recording presence or absence of fungal colonies). This method is time consuming, require knowledge within fungal morphology, and do not facilitate identification to species in all cases. Molecular methods such as quantitative PCR (qPCR) could allow detection and quantification of fungal DNA at the species level in a relatively time effective way, particularly since the method allows for automation in different steps such as DNA extraction and pipetting. Whether the latter method is suitable within seed health evaluations will depend on the relationship between the amount of DNA of the different fungal species and field performance, and the purpose of the test (evaluation of planting value, need for seed treatment, survey of fungal species, quality of grain for consumption etc). To compare the two different methods, about 150 spring wheat seed lots from the years 2016-2017 (including two cultivars) were selected for the analysis of different fungi using species-specific qPCR and compared with the results from routine testing on PDA. In the 2016 material (81 samples), a mean seed infestation rate of 26% was observed for Microdochium spp. in the PDA test. The level of Fusarium was lower (mean infestation rate of 5%). A strong relationship was observed between the percentage of seeds infested by Microdochium and the level of Microdochium DNA (sum of DNA from Microdochium majus and Microdochium nivale) quantified by qPCR (R2 of 0.76, p<0.01). The relationship between Fusarium infested seeds and the level of Fusarium DNA (sum of DNA from three species) was moderate (R2 of 0.33, p<0.01). The samples were also analysed for the presence of P. nodorum. Compared to Fusarium and Microdochium, P. nodorum was present at an intermediate level (mean infestation rate of 12%). The relationship between the two different methods was weaker for this fungus (R2 of 0.21, p<0.01) than for Fusarium and Microdochium. The relationship between germination capacity and rating of the three groups of fungi by either method was studied. Preliminary results suggest that of the three fungi, Microdochium was associated with germination capacity in the 2016 material, and that the Microdochium infestation rate on PDA was slightly better correlated to germination capacity than the level of Microdochium DNA. Further results will be presented at the conference, including the association between the relative DNA content of the different Microdochium and Fusarium species and seed germination.
Sammendrag
No abstract has been registered
Forfattere
Trond Rafoss Daniel Flø Leif Sundheim Per Hans Micael Wendell Guro Brodal Åshild Ergon Christer Magnusson Arild SlettenSammendrag
No abstract has been registered