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.
2011
Abstract
Twenty cypress accessions were tested for freezing tolerance. After freezing to −15°C, differences among cypress accessions were tested by measuring electrolyte leakage and chlorophyll fluorescence. Based on these data, cypress accessions showing contrasting freezing tolerance were subjected to transcript profiling of candidate genes upon the development of cold hardening, with the ultimate goal of providing a scientific basis for selecting/breeding cypress genotypes with higher tolerance to low temperature. Nine different cypress genes were selected: a heat shock protein, a putative chaperonin, a chlorophyll-binding protein, a serine/threonine protein kinase, a putative exonuclease, a dehydrin, and three senescenceassociated proteins. Transcript levels of these genes were profiled during cold hardening under controlled conditions using real-time reverse-transcription-polymerase chain reaction. While the genes showed regulation patterns common to both cypress accessions, in the case of chaperonin, exonuclease, and some senescence-associated proteins, clonal differences in gene regulation were found. The potential relationship of these differences with cold tolerance is discussed.
Abstract
The causative agent of dieback on European ash (Fraxinus excelsior) was first described as Chalara fraxinea based on cultural morphology because no sexual stage of the fungus was known. Later, based on culturing of ascospores of a candidate teleomorph, morphological comparison and nuclear ribosomal internal transcribed spacer sequencing, the sexual stage of C. fraxinea was assigned as Hymenoscyphus albidus, a native and widespread species in Europe. Recently, the morphological species concept of H. albidus was shown to cover two species that cannot be separated from each other based on teleomorph characters, but which can be distinguished by several DNA markers. As a result, the strains causing ash dieback were reassigned as H. pseudoalbidus. The closely related H. albidus is presumably a non-pathogenic endophyte, but pathogenicity tests to confirm this hypothesis have not yet been performed. Genotyping of herbarium specimens has shown that H. pseudoalbidus was present in Switzerland for at least a decade prior to the epidemic outbreak in Europe. The origin of the ash dieback pathogen, and the general importance of correct pathogen identification to development of effective disease control, are discussed.
Abstract
Gene expression levels (PAL, CCR1, HCT1, and CAD for the phenylpropanoid pathway, PX3 peroxidase, and CHI4 class IV chitinase), lignin, and soluble and cell wall bound phenolic compounds in bark and sapwood of Picea sitchensis clones inoculated with Heterobasidion annosum s.s. were compared before and 3 days after wounding and artificial inoculation, at site of inoculation and 1 cm above the inoculation site. In bark all genes were up-regulated at the site of inoculation but, except for CAD, not in the distal zone. In sapwood all genes were down-regulated, except for PX3 and CHI4; PAL, CCR1, HCT1 and CAD were present at lower levels around the inoculation site than in the distal zone. Compared to wounding only, inoculation with H. annosum triggered different CAD, PX3, and CHI4 levels in bark but not in sapwood. Different concentrations of cell wall bound phenolic compounds (unknown2, unknown3, coniferin, astringin, taxifolin, piceid, and isorhapontin) were found in bark after wounding and inoculation compared to constitutive material (i.e. untreated samples), whereas in sapwood concentrations did not differ following treatment. These results indicate that bark of Sitka spruce has a stronger and earlier response to wounding and pathogen inoculation than sapwood.
Abstract
No abstract has been registered
Abstract
Fungal hyphae in soil, although crucial in the C-dynamics, are difficult to quantify. Here we present a simple method for fungal biomass assessment and possibility for up-scaling. Originally we used root nets to quantify fine roots in drought-stressed Picea abies stand as described by Lukac and Godbold (2010).Root nets (7 cm wide, mesh size 1 mm) were inserted vertically to 20 cm depth, twice during the course of one year. When root nets were extracted from the soil, large amounts of hyphae were growing on and through the nets in the control plot, whereas little or no hyphae were growing in nets from the drought-stressed plot.This observation led us to consider root nets as a promising tool to quantify hyphae as well. The inert net material together with its regular geometric pattern is well suited for obtaining fungal biomass estimates and provide a material for further molecular analysis of fungal species. We will describe a proposal how to scan the hyphae, calculate the biomass and upscale to the soil volume unit.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Current risk assessment procedures for contaminated land and for pesticides often fail to properly characterize the risk of chemicals for environment or human health and provide only a rough estimate of the potential risk of chemicals. Chemicals often occur in mixtures in the environment, while regulatory agencies often use a chemical-by-chemical approach, focusing on a single media, a single source, and a single toxic endpoint. Further, the importance of soil microbes and their activity in the functioning of soils impose a need to include microorganisms in soil quality assessments including terrestrial ecotoxicological studies. Numerous papers have been published on the effects of different contaminants on soil microbes, establishing changes in soil microbial diversity as an indicator of soil pollution. However, only a limited number of molecular studies focus on changes in fungal species when investigating soil microbial diversity. The main objective of the study presented here, is to assess the applicability of changes in soil microbial diversity and activity levels as indicators of ecologically relevant effects of chemicals contamination. We will achieve this through studies of effects of the fungicide picoxystrobin and the chemical 4-n-nonylphenol on the microbial biodiversity in a Norwegian sandy loam, with focus both on prokaryotes and the fungal species. Laboratory incubation experiments at 20°C with soil samples treated with the single chemicals or mixtures, with continuous monitoring of respiration activity as well as occasional destructive sampling for extraction of soil DNA, RNA, and chemical residues, was performed through a 70 d period. Results from amplification of soil bacterial and fungal DNA followed by T-RFLP (terminal restriction fragment length) analyses to assess chemicals effects on soil microbial diversity, indicate significant effects of the studied chemicals on soil microbial community structure. To identify specific bacterial or fungal groups that are affected, an assessment of the effects of the chemicals on the soil microbial metagenome by high throughput shot-gun sequencing (454 sequencing) is in progress This work is part of the research project ‘Bioavailability and biological effects of chemicals - Novel tools in risk assessment of mixtures in agricultural and contaminated soils’ funded by the Norwegian research council.
Authors
Line Emilie Sverdrup Christine Bjørge Ole Martin Eklo Merete Grung Torsten Källqvist Ingeborg Klingen Marit Låg Edgar Rivedal Erik Ropstad Steinar ØvrebøAbstract
No abstract has been registered
Abstract
In a series of tritrophic-level interaction experiments, the effect of selected host plants of the spider mites, Tetranychus evansi and Tetranychus urticae, on Neozygites floridana was studied by evaluating the attachment of capilliconidia, presence of hyphal bodies in the infected mites, mortality from fungal infection, mummification and sporulation from fungus-killed mite cadavers. Host plants tested for T. evansi were tomato, cherry tomato, eggplant, nightshade, and pepper while host plants tested for T. urticae were strawberry, jack bean, cotton and Gerbera. Oviposition rate of the mites on each plant was determined to infer host plant suitability while host-switching determined antibiosis effect on fungal activity. T. evansi had a high oviposition on eggplant, tomato and nightshade but not on cherry tomato and pepper. T. urticae on jack bean resulted in a higher oviposition than on strawberry, cotton and Gerbera. Attachment of capilliconidia to the T. evansi body, presence of hyphal bodies in infected T. evansi and mortality from fungal infection were significantly higher on pepper, nightshade and tomato. The highest level of T. evansi mummification was observed on tomato. T. evansi cadavers from tomato and eggplant produced more primary conidia than those from cherry tomato, nightshade and pepper. Switching N. floridana infected T. evansi from one of five Solanaceous host plants to tomato had no prominent effect on N. floridana performance. For T. urticae, strawberry and jack bean provided the best N. floridana performance when considering all measured parameters. Strawberry also had the highest primary conidia production. This study shows that performance of N. floridana can vary with host plants and may be an important factor for the development of N. floridana epizootics.