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.
2010
Authors
David M. Gadoury Belachew Asalf Tadesse M Heidenreich Maria Herrero MJ Welser Robert C Seem Anne Marte Tronsmo Arne StensvandAbstract
A collection of four clonal isolates of Podosphaera aphanis was heterothallic and was composed of two mutually exclusive mating types. Cleistothecial initials approximate to 20 to 30 mu m in diameter were observed within 7 to 14 days after pairing of compatible isolates and developed into morphologically mature ascocarps within 4 weeks after initiation on both potted plants maintained in isolation and in field plantings in New York State and southern Norway. Ascospores progressed through a lengthy maturation process over winter, during which (i) the conspicuous epiplasm of the ascus was absorbed; (ii) the osmotic potential of the ascospore cytoplasm increased, resulting in bursting of prematurely freed spores in water; and, finally, (iii) resulting in the development of physiologically mature, germinable, and infectious ascospores. Release of overwintered ascospores from field collections was coincident with renewed plant growth in spring. Overwintered cleistothecia readily dehisced when wetted and released ascospores onto glass slides, detached strawberry leaves, and leaves of potted plants. Plant material exposed to discharged ascospores developed macroscopically visible mildew colonies within 7 to 10 days while noninoculated controls remained mildew free. Scanning electron and light microscopy revealed that cleistothecia of P. aphanis were enmeshed within a dense mat of hyphae on the persistent leaves of field-grown strawberry plants and were highly resistant to removal by rain while these leaves remained alive. In contrast, morphologically mature cleistothecia on leaves of nine deciduous perennial plant species were readily detached by simulated rain and seemed adapted for passive dispersal by rain to other substrates. Contrary to many previous reports, cleistothecia appear to be a functional source of primary inoculum for strawberry powdery mildew. Furthermore, they differ substantially from cleistothecia of powdery mildews of many deciduous perennial plants in their propensity to remain attached to the persistent leaves of their host during the intercrop period.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Today the spruce bark beetle Ips typographus is always univoltine in Northern Europe including Norway and completes development from egg to adult between May and August. Further south in Europe, development is bivoltine with the completion of two generations in most years. A temperature-driven developmental model suggests that by 2070-2100 the voltinism of I. typographus will change dramatically in Norway. If summers become only 2.5°C warmer than today bivoltinism can be expected every single year in the major spruce growing areas in S-Norway. This is likely to have dramatic effects on forestry since two generations per year will give two, instead of one, attack periods each summer. In addition to increasing the number of attacked trees the effect of the attacks may also be more severe, as Norway spruce is more susceptible to beetle attacks later in the summer. However, climate change will probably also change the phenology of Norway spruce and thus its susceptibility to attack by I. typographus and its phytopathogenic fungal associates. We are currently modelling how tree resistance varies with temperature and tree phenology in order to provide more well-founded advice to forest managers on the interaction between bark beetles and tree in a future climate.
Abstract
No abstract has been registered
Authors
Venche Talgø G. Chastagner I. M. Thomsen T. Cech K. Riley K. Lange Sonja Klemsdal Arne StensvandAbstract
Current season needle necrosis (CSNN) has been a serious foliage disorder on true fir Christmas trees and bough material in Europe and North America for more than 25 y. Approximately 2-4 weeks after bud break, needles develop chlorotic spots or bands that later turn necrotic. The symptoms have been observed on noble fir (Abies procera), Nordmann fir (A. nordmanniana) and grand fir (A. grandis) on both continents. CSNN was reported as a physiological disorder with unknown aetiology from USA, Denmark, and Ireland, but was associated with the fungus Kabatina abietis in Germany, Austria and Norway. In 2007, a fungus that morphologically resembled K. abietis was isolated from symptomatic needle samples from Nordmann fir from Austria, Denmark, Germany, Norway, and USA. Sequencing of the internal transcribed spacer (ITS) region of ribosomal DNA of these cultures, plus a K. abietis reference culture from Germany (CBS 248.93), resulted in Hormonema dematioides, the imperfect stage of Sydowia polyspora, and thus the taxonomy is further discussed. Inoculation tests on Nordmann fir seedlings and transplants with isolates of S. polyspora from all five countries resulted in the development of CSNN symptoms. In 2009, S. polyspora was also isolated from symptomatic needles from Nordmann fir collected in Slovakia. (c) 2010 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.
Abstract
The gas chromatography mass spectrometry (GC-MS) deconvolution reporting software (DRS) from Agilent Technologies has been evaluated for its ability as a screening tool to detect a large number ofpesticides in incurred and fortified samples extracted with acetone/dichloromethane/light petroleum(Mini-Luke method). The detection of pesticides is based on fixed retention times using retention timelocking (RTL) and full scan mass spectral comparison with a partly customer built automated massspectral deconvolution and identification system (AMDIS) database. The GC-MS was equipped with a programmable temperature vaporising (PTV) injector system which enables more sample to be injected.In a blind study of 52 real samples a total number of 158 incurred pesticides were found. In addition to the 85 pesticides found by manual interpretation of GC-NPD/ECD chromatograms, the DRS revealed 73 morepesticides (+46%). The DRS system also shows its potential to discover pesticides which are normally notsearched for (EPN in long beans from Thailand). A spiking experiment was performed to blank matricesof apple, orange and lettuce with 177 different pesticides at concentration levels 0.02 and 0.1 mg/kg. The samples were analysed on GC-MS full scan and the AMDIS match factor was used as a mass spectralquality criterion. The threshold level of the AMDIS match factor was set at 20 to eliminate most of thefalse positives. AMDIS match factors from 20 up to 69 are regarded only as indication of a positive hit andmust be followed by manual interpretation. Pesticides giving AMDIS match factors at ≥70 are regarded as identified. To simplify and decrease the large amount of data generated at each concentration level,the AMDIS match factors ≥20 was averaged (mean AMF) for each pesticide including the commodities and their replicates. Among 177 different pesticides spiked at 0.02 and 0.1 mg/kg level, the percentage of mean AMF values ≥70 were 23% and 80%, respectively. For 531 individual detections of pesticides (177pesticides×3 replicates) giving AMDIS match factor 20 in apple, orange and lettuce, the detection rates at 0.02 mg/kg were 71%, 63% and 72%, respectively. For the 0.1 mg/kg level the detection rates were 89%,85% and 89%, respectively. In real samples some manual interpretation must be performed in addition. However, screening by GC-MS/DRS is about 5-10 times faster compared to screening with GC-NPD/ECDbecause the time used for manual interpretation is much shorter and there is no need for re-injection on GC-MS for the identification of suspect peaks found on GC-NPD/ECD.
Authors
Arild Andersen Trond Hofsvang May Bente Brurberg Christer Magnusson Trond Rafoss Anne Marte Tronsmo Bjørn Økland Leif SundheimAbstract
No abstract has been registered
Authors
Arild Andersen Trond Hofsvang May Bente Brurberg Christer Magnusson Trond Rafoss Brita Toppe Anne Marte Tronsmo Bjørn Økland Leif SundheimAbstract
No abstract has been registered