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.
2009
Authors
Fushi Wen Ho Hyung Woo Elizabeth A. Pierson Toril Eldhuset Carl Gunnar Fossdal Nina Elisabeth Nagy Martha C. HawesAbstract
No abstract has been registered
Abstract
Two mature clones of Norway spruce (Picea abies (L.) Karst.) shown to have different level of resistance towards inoculation of Heterobasidion parviporum were compared with respect to spatiotemporal expression of transcripts related to biosynthesis of lignin, stilbenes and other phenolic compounds in response to fungal inoculation and physical wounding. Both clones responded to H. parviporum and physical wounding at transcriptional and chemical levels. Taxifolin, detected in the resistant clone only, increased in concentration following both wounding and inoculation. Concentrations of stilbenoid glucosides were highest in the susceptible clone. Following wounding or inoculation, concentrations of these glucosides increased in the susceptible clone, and quantities of their corresponding aglycones increased dramatically in both clones close to the treatment point. Significant changes in transcription were detected over the entire lesion length for all transcripts, and only the changes in a few transcripts indicated a response to inoculation with H. parviporum differing from that caused by wounding alone. The resistant clone had higher basal concentrations of lignin (LTGA) compared to the susceptible clone; concentrations increased in both clones after wounding and wounding plus inoculation treatments, but remained consistently higher in the resistant clone, suggesting higher lignin levels in the cell walls compared to the susceptible clone. In addition, the transcript level in the same clones was also measured the following year and we saw indications of primed defences for a number of gene products likely resulting from the inoculations performed 12 months prior.
Authors
Nadeem Yaqoob Igor A. Yakovlev Paal Krokene Harald Kvaalen Halvor Solheim Carl Gunnar FossdalAbstract
Clonal variation towards resistance has been observed in Norway spruce Heterobasidion annosum s.l. (H.a). H.a. is the main cause of root rot and has a severe economic impact on an economically important conifer tree species. Annual financial losses are in the hundreds of millions of Euros annually. Less susceptible clones appear to have an efficient system of recognizing the pathogen and initiating early defense signalling events. Active defense responses can be started locally and transmitted systemically. This work focus on the expression both spatially (systemically) and temporally in this pathosystem. Two-year-old, somatic saplings of the Norway spruce clone were challenged with H.a., wounded, methyl jasmonate painted and compared to untreated controls and ninety plants were used for the experiment. Stem samples were collected at 1, 3, 6 and 13 days post inoculation (d.p.i). The stem of the saplings were divided into sections along its length and the bark and wood separated from each other at time of collection. In order to see local response an area of 1cm including the site of inoculation was collected, while the spatial (systemic) response was assessed in sections collected at distances of 3 and 6cm away from the site of inoculation. The separated bark and wood were analysed for differential gene expression by qRT-PCR, and the results from peroxidases (PaPX3 and PaPX2) and a chitinase (PaChi4) are presented. Both local and systemic up- and down-regulation were observed at the transcriptional level in both bark and wood, up to 2000 fold local increase in expression was observed for PaChi4.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Berit Nordskog David M. Gadoury May Bente Brurberg Tor Håkon Sivertsen R. Kennedy Arne HermansenAbstract
No abstract has been registered
Authors
Ari Hietala Nina Elisabeth Nagy Arne Steffenrem Harald Kvaalen Carl Gunnar Fossdal Halvor SolheimAbstract
No abstract has been registered
Authors
Leif Sundheim Maria-Luz Herrero Trond Rafoss Brita Toppe May Bente Brurberg Trond Hofsvang Christer Magnusson Anne Marte Tronsmo Bjørn ØklandAbstract
Phytophthora ramorum S. Werres, A.W.A.M. de Cook & W.A. Man in‘t Veld is a newly described Phytophthora-species which is considered to be relatively recently introduced to both USA and Europe from an unknown area, or areas, of origin. The pathogen has a wide host range and causes a complexity of disease symptoms generally grouped into three categories: canker, foliage lesion, and dieback. In Europe the pathogen has been reported in 21 countries, Norway included; predominantly on ornamental plants in nurseries, but also outside nurseries in gardens and semi-natural environment, most often on rhododendrons. The Norwegian Food Safety Authority needs a risk assessment of the pest as basis for an evaluation of a future phytosanitary risk management of P. ramorum, including whether the organism should be regulated as a quarantine pest in Norway. On this background the Norwegian Food Safety Authority, in a letter of 22nd August 2008, requested a pest risk assessment of P. ramorum from the Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM). The pest risk assessment was adopted by VKM"s Panel on plant health (Panel 9) on a meeting 24th June 2009. VKM"s Panel 9 gives the following main conclusions of the risk assessment: 1) P. ramorum is present but not widely distributed in Norway, and the pest is under official control. The outdoors surveys of P. ramorum in Norway have not been conducted systematically over the whole country, and some uncertainty therefore still remains regarding the current distribution of P. ramorum in the PRA area. 2) The overall probability of entry of P. ramorum into Norway and the overall probability of establishment of P. ramorum in Norway are both rated as high with low levels of uncertainty; 3) In the absence of statutory control the probability for P. ramorum to be spread quickly in the PRA area by trade of host plants for planting is rated as high. The uncertainty of this assessment is low; 4) The part of the PRA area where presence of P. ramorum might result in economically important losses (the endangered area) is assessed to be most of the country of Norway, except where the climate is predicted to be unfavourable for the pest. However, this area must be regarded as a maximum estimate for the endangered area. On the other hand, a narrow and very conservative estimate for the endangered area can be defined based on the geographical distribution of highly susceptible host plants in Norway. This area is gardens and parks with Rhododendron spp., Viburnum spp. and F. sylvatica and areas in the wild into which Rhododendron spp. has spread and woods with F. sylvatica. Woods with F. sylvatica is limited to the county of Vestfold and some small areas in the counties of Aust-Agder and Hordaland; 5) P. ramorum is likely to have moderate economic impact on the nurseries in the PRA area with current phytosanitary measures. Without any such regulations P. ramorum is likely to have major economic impact on the nursery industry of the PRA area. The levels of uncertainties of these assessments are low; 6) With current phytosanitary measures P. ramorum is likely to have moderate economic impact on parks and private gardens in parts of the PRA area. Without any such regulations P. ramorum is likely to have major economic impact in the best climatic zones of the PRA area. The levels of uncertainties of these assessments are low; 7) The impact of P. ramorum in coniferous and mixed forests of the PRA area is likely to be minor. The level of uncertainty of this assessment is medium. The impact of P. ramorum in natural and planted deciduous broadleaf forests of the PRA area is likely to be minor due to the scattered and limited distribution of the most susceptible species. The level of uncertainty of this assessment is medium; 8) The non-commercial and environmental consequences to natural environments in the PRA area are likely to be moderate. The level of uncertainty ...
Authors
Ingerd Skow Hofgaard Katarzyna Marzec Guro Brodal Birgitte Henriksen May Bente Brurberg Anne-Marte TronsmoAbstract
Microdochium nivale (syn. Microdochium nivale var. nivale) and Microdochium majus (syn. Microdochium nivale var. majus) are important pathogens which cause snow mould on grasses and winter cereals. These fungi are also able to cause leaf blotch of oat and seedling blight, foot rot and ear blight in cereals. Although no distinct differences in the host range of M. nivale and M. majus are found, indications for differences in host preferences between these fungal species have previously been discussed. The culture collection at Bioforsk contains about 250 Microdochium sp. isolated from grasses and cereals over the last 20 years. Most of the isolates collected from leaves of cereals displaying snow mould symptoms in spring, were identified as M. nivale (71 %), whereas most of the isolates collected from cereal seeds (mostly wheat) belong to the species M. majus (92 %). All, except one out of the sixty nine Microdochium sp. isolated from grass leaves were identified as M. nivale (99 %). The relatively higher incidence of M. majus vs. M. nivale on cereal seeds (mostly wheat) harvested in Norway, is in agreement with studies in UK (Parry et al. 1995). Parry et al. suggested that higher natural occurrence of M. majus (vs. M. nivale) on seeds of cereals could be partly due to the higher proportion of M. majus isolates producing perithecia and thus, a relatively higher amount of M. majus spores spreading to the ear (Parry et al. 1995). The high frequency of M. nivale (99 %) vs. M. majus on grasses collected in Norway could indicate that M. nivale is more aggressive on certain grass species. Studies in our lab indeed point towards a higher aggressiveness of M. nivale vs. M. majus on perennial ryegrass at low temperature (2?C) (Hofgaard et al 2006). However, the high incidence of M. nivale on grass leaves could also be caused by differences in temperature preferences, saprophytic ability or ability to infect certain plant parts. Isolates of M. nivale display a higher in vitro growth rate compared to isolates of M. majus at 2?C (Hofgaard et al. 2006). In conclusion, the higher natural occurrence of M. nivale vs. M. majus on turf grasses and the relatively higher aggressiveness of M. nivale on perennial ryegrass could indicate that M. nivale somehow is better adapted to infect certain grass species.
Abstract
European ash (Fraxinus excelsior), also known as common ash, occurs naturally inland in lower areas of southeastern Norway and along the southern coast of the country. It is important both as a forest and ornamental tree. During the last decade, dieback has become a disastrous disease on F. excelsior in many European countries. The anamorphic fungus Chalara fraxinea T. Kowalski (1), described for the first time from dying ash trees in Poland, is now considered the cause of ash dieback (2). In May of 2008, C. fraxinea was isolated from 1.5 m high diseased F. excelsior in a nursery in Østfold County in southeastern Norway. Symptoms included wilting, necrotic lesions around leaf scars and side branches, and discoloration of the wood. From symptomatic branches, small pieces (approximately 1 cm3) were excised in the transition area between healthy and discolored wood. After surface sterilization (10 s in 70% ethanol + 90 s in NaOCl), the pieces were air dried for 1 min in a safety cabinet, cut into smaller pieces, and placed on media. The fungus was isolated on potato dextrose agar (PDA) and water agar (WA). On PDA, the cultures were tomentose, light orange, and grew slowly (21 mm mean colony diameter after 2 weeks at room temperature). Typical morphological features of C. fraxinea developed in culture. Brownish phialides (14.8 to 30.0 [19.5] × 2.5 to 5.0 [4.1] μm, n = 50) first appeared in the center of the colonies on the agar plugs that had been transferred. The agar plugs were 21 days old when phialides were observed. Abundant sporulation occurred 3 days later. Conidia (phialospores) extruded apically from the phialides and formed droplets. Conidia measured 2.1 to 4.0 (3.0) × 1.4 to 1.9 (1.7) μm (n = 50). The first-formed conidia from each phialide were different in size and shape from the rest by being longer (6 μm, n = 10) and more narrow in the end that first appeared at the opening of the phialide. Internal transcribed spacer sequencing confirmed that the morphological identification was correct (Accession No. EU848544 in GenBank). A pathogenicity test was carried out in June of 2008 by carefully removing one leaf per plant on 10 to 25 cm high F. excelsior trees (18 trees) and placing agar plugs from a 31-day-old C. fraxinea culture (isolate number 10636) on the leaf scars and covering with Parafilm. After 46 days, isolations were carried out as described above from discolored wood that had developed underneath necrotic lesions in the bark and subsequently caused wilting of leaves. All the inoculated plants showed symptoms, and C. fraxinea was successfully reisolated. No symptoms were seen on uninoculated control plants (eight trees) that had received the same treatment except that sterile PDA agar plugs had been used.