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.
2019
Sammendrag
Invasive alien species and new plant pests are introduced into new regions at an accelerating rate, due to increasing international trade with soil, plants and plant products. Exotic, plant pathogenic oomycetes in soil from the root zone of imported plants pose a great threat to endemic ecosystems and horticultural production. Detecting them via baiting and isolation, with subsequent identification of the isolated cultures by Sanger sequencing, is labour intensive and may introduce bias due to the selective baiting process. We used metabarcoding to detect and identify oomycetes present in soil samples from imported plants from six different countries. We compared metabarcoding directly from soil both before and after baiting to a traditional approach using Sanger-based barcoding of cultures after baiting. For this, we developed a standardized analysis workflow for Illumina paired-end oomycete ITS metabarcodes that is applicable to future surveillance efforts. In total, 73 soil samples from the rhizosphere of woody plants from 33 genera, in addition to three samples from transport debris, were analysed by metabarcoding the ITS1 region with primers optimized for oomycetes. We detected various Phytophthora and Pythium species, with Pythium spp. being highly abundant in all samples. We also found that the baiting procedure, which included submerging the soil samples in water, resulted in the enrichment of organisms other than oomycetes, compared to non-baited soil samples.
2018
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Dieback of European ash, caused by the ascomycete Hymenoscyphus fraxineus originating from Asia, has rapidly spread across Europe, and is threatening this keystone tree at a continental scale. High propagule pressure is characteristic to invasive species. Consistently, the enormous production of windborne ascospores by H. fraxineus in an ash forest with epidemic level of disease obviously facilitates its invasiveness and long distance spread. To understand the rate of build-up of propagule pressure by this pathogen following its local introduction, during 2011–2017 we monitored its sporulation at a newly infested ash stand in south-western Norway characterized with mild winters and cool summers. We also monitored the propagule pressure by Hymenoscyphus albidus, a non-pathogenic native species that competes for the same sporulation niche with H. fraxineus. During the monitoring period, crown condition of ash trees had impaired, and 20% of the dominant trees were severely damaged in 2017. H. fraxineus showed an exponential increase in spore production between 2012 and 2015, followed by drastic decline in 2016 and 2017. During 2011–2013, the two Hymenoscyphus species showed similar sporulation level, but thereafter spores of H. albidus were no longer detected. The data suggest that following local introduction, the population of H. fraxineus reaches rapidly an exponential growth stage if the local weather conditions are favorable for ascomata maturation across years. In the North Atlantic climate, summer temperatures critically influence the pathogen infection pressure, warm summers allowing the population to grow according to its biotic potential, whereas cold summers can cause a drastic decline in propagule pressure.
Sammendrag
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Sammendrag
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Forfattere
Ari Hietala Isabella Børja Hugh B. Cross Nina Elisabeth Nagy Jørn Henrik Sønstebø Volkmar Timmermann Adam Vivian-Smith Halvor SolheimSammendrag
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Forfattere
Ari Hietala Isabella Børja Hugh Cross Nina Elisabeth Nagy Halvor Solheim Volkmar Timmermann Adam Vivian-SmithSammendrag
European ash (Fraxinus excelsior), a keystone species with wide distribution and habitat range in Europe, is threatened at a continental scale by an invasive alien ascomycete, Hymenoscyphus fraxineus. In its native range of Asia, this fungus is a leaf endophyte with weak parasitic capacity and robust saprobic competence in local ash species that are closely related to European ash. In European ash, H. fraxineus has a similar functional role as in Asia, but the fungus also aggressively kills shoots, resulting in crown dieback and tree death. H. fraxineus is a typical invasive species, as its spread relies on high propagule pressure. While crown dieback of European ash is the most obvious symptom of ash dieback, the annual colonization of ash leaves is a crucial key dependency for the invasiveness of H. fraxineus, since its fruiting bodies are formed on overwintered leaf vein tissues in soil debris. Leaves of European ash host a wide range of indigenous epiphytes, endophytes, facultative parasites and biotrophic fungi, including Hymenoscyphus albidus, a relative of H. fraxineus that competes for the same sporulation niche as the invader. At face value, leaves of European ash are colonized by a large and diverse indigenous mycobiome. In order to understand why this invader became successful in Europe, we discuss and summarize the current knowledge of diversity, seasonal dynamics and traits of H. fraxineus and indigenous fungi associated with leaves of European ash.
Forfattere
Heidi Udnes Aamot Katherine Ann Gredvig Nielsen Shiori Koga Anne Kjersti Uhlen Ulrike Böcker Erik Lysøe Guro Brodal Ruth Dill-Macky Ingerd Skow HofgaardSammendrag
The proportion of Norwegian wheat used for food has varied significantly during the recent decade, mainly because of the instability of factors that are essential to baking quality (i.e. protein content and gluten functionality). During the same period, serious contamination of Fusarium spp. and mycotoxins was observed in some grain lots [1, 2]. A project was established to generate greater knowledge of the interface between gluten functionality and effects of Fusarium species and other microorganisms on Norwegian wheat quality. Instances of severe degradation of gluten proteins that resulted in an almost complete loss of gluten functionality were observed in some lots of Norwegian wheat. The degradation of the gluten appeared to be caused by exogenous proteases. Metabarcoding of fungi and bacteria in these grain lots identified fungi within the Fusarium Head Blight complex, as well as one bacterial species, as candidate species for influencing gluten functionality. Some of these candidates were inoculated on wheat during flowering [3]. Analysis of baking quality of the flour from this experiment revealed a reduced proportion of un-extractable polymeric proteins (%UPP) and severe reductions in the gluten’s resistance to stretching (RMAX) in wheat flour from plants inoculated with Fusarium graminearum. Flour from wheat inoculated with Fusarium avenaceum was generally less infested, and showed minimal or no reduction in gluten functionality and %UPP compared to flour from the F. graminearum infested samples. Flour from wheat inoculated with Michrodochium majus is yet to be analysed. References 1. Koga, S., et al., Investigating environmental factors that cause extreme gluten quality deficiency in winter wheat (Triticum aestivum L.). Acta Agriculturae Scandinavica, Section B—Soil & Plant Science, 2016. 66(3): p. 237-246. 2. Hofgaard, I., et al., Associations between Fusarium species and mycotoxins in oats and spring wheat from farmers’ fields in Norway over a six-year period. World Mycotoxin Journal, 2016. 9(3): p. 365-378. 3. Nielsen, K.A.G., Effect of microorganisms on gluten quality in wheat., in Faculty of Biosciences. 2017, Norwegian University of Life Sciences: Ås.
Sammendrag
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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.