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
The effect of different light environments on trap catches of Frankliniella occidentalis and Trialeurodes vaporariorum was investigated in a commercial greenhouse rose production unit during late autumn. Two top light treatments were used: 1) High pressure sodium lamps (HPSLs) and 2) HPSLs and light emitting diodes (LEDs) with 20% blue and 80% red light. More thrips and fewer whiteflies were caught on yellow sticky traps, and more thrips were found in the flowers, in areas were LEDs were used in addition to HPSLs compared to areas where only HPSLs were used. No effect of the light treatments was found on the population level of Amblyseius swirskii, but a lower ratio of predatory mites to thrips was found on the plants where LEDs were used. The results suggest that using blue and red LEDs as interlighting, or otherwise supplementary to HPSLs, will change thrips and whitefly spatial distribution in the rose crop, and that natural enemy release rates probably need to be adjusted accordingly.
Abstract
No abstract has been registered
Abstract
Arable weeds are generally distributed in patches, while herbicides are applied uniformly. Herbicides can be saved if only the patches are sprayed, i.e. patch spraying (PS). Bottlenecks for cost-effective PS are weed monitoring technology and valid technology-based decision rules for PS (thresholds). The novel machine vision algorithm Weedcer has been developed as an efficient weed monitoring tool for PS. Weedcer estimates the proportions of young weed leaves and cereal leaves in high resolution red–green–blue images. We conducted field trials to test relative weed cover (RWC) and relative mayweed cover (RMC) estimated by Weedcer as decision rules for PS. RWC is the total weed cover divided by the total plant cover and RMC is the mayweed cover divided by the total plant cover. The main criterion for evaluation and basis of these thresholds was the measured grain yield. Images (about 0.06-m2) were acquired with a GPS guided autonomous field robot in spring, the normal time for spraying seed-propagated broadleaf weeds in both winter – and spring cereals in Norway. Three map-based trials (weed monitoring and spraying in two separate operations) showed that mean RWC per management unit (12.0 × 12.5-m) was generally adequate. In winter wheat heavily infested with scentless mayweed (Tripleurospermum inodorum (L.) Sch.Bip.) and/or scented mayweed (Matricaria recutita L.), the mean RMC per management unit was more adequate. Progress during the project allowed three additional trials conducted in real-time (weed monitoring and spraying in the same operation). These were conducted with the robot in spring cereals, and showed that a weighted moving average of RWC per image was adequate. The sprayed and unsprayed management units in these trials were minimum 3.0 × 3.0-m and 0.5 × 3.0-m, respectively. Results indicated that the Weedcer-based thresholds should be lower in wheat (Triticum aestivum) than in barley (Hordeum vulgare).
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