Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2018
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Forfattere
Roger Holten Frederik Bøe Marit Almvik Marianne Stenrød Mats Larsbo Nicholas Jarvis Ole Martin EkloSammendrag
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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.
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High-throughput sequencing for plant virus diagnosis in Norway
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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.
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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.