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
Abstract
Isolates of Colletotrichum sublineolum were collected from different sorghum-producing regions of Ethiopia and divided into five groups based on their geographic origin. The growth rate of 50 isolates showed considerable variation: 1·7?5·8 mm day?1, mean 3·3 mm day?1. However, the isolates displayed little variation in colony colour and colony margin, except for isolates from the north, which were different from the others. Amplified fragment length polymorphism analysis of 102 isolates revealed much greater variations among the different groups. Dice similarity coefficients ranged from 0·32 to 0·96 (mean 0·78). Cluster analysis and principal coordinate analysis revealed a differentiation of the isolates according to their geographic origin, and both methods clearly indicated a genetic separation between the southern, the eastern and the other isolates. Analysis of molecular variance (amova) indicated a high level of genetic variation both among (42%) and within (58%) the C. sublineolum sampling sites in Ethiopia. The amova also indicated a high level of genetic differentiation (FST = 0·42) and limited gene flow (Nm = 0·343). The results of this study confirmed the presence of a highly diverse pathogen, which is in agreement with the existence of diverse host genotypes and widely ranging environmental conditions in sorghum-producing regions of the country. Such diversity should be taken into account in future breeding programmes to achieve an effective and sustainable disease management strategy.
Abstract
In terrestrial ecotoxicology there is a serious lack of data for potential hazards posed by engineered nanoparticles (ENPs). This is partly due to complex interactions between ENPs and the soil matrix, but also to the lack of suitable toxicological end points in organisms that are exposed to ENPs in a relevant manner. Earthworms are key organisms in terrestrial ecosystems, but so far only physiological end points of low sensitivity have been used in ecotoxicity studies with ENPs. We exposed the earthworm Lumbricus terrestris to silver nanoparticles and measured their impact on apoptosis in different tissues. Increased apoptotic activity was detected in a range of tissues both at acute and sublethal concentrations (down to 4 mg/kg soil). Comparing exposure in water and soil showed reduced bioavailability in soil reflected in the apoptotic response. Apoptosis appears to be a sensitive end point and potentially a powerful tool for quantifying environmental hazards of ENPs.
Authors
Heleen de Wit Toril Eldhuset Jan MulderAbstract
Dissolved aluminium (Al) in soils, mobilized by acid deposition, is considered a threat to forest health through hampering root growth and nutrient uptake. Since the end of the 1980s dissolved Al in forest soil water plays a key role in the assessment of critical loads of acid deposition. So far, most evidence for toxicity of dissolved Al in forest soil water is based on nutrient solution studies and pot experiments. Here, we present results from one of the few in situ ecosystem-scale forest manipulation experiments to study the effect of Al on mature forest trees. A plotwise addition of dilute AlCl3 was conducted during seven years in an even-aged spruce forest (Picea abies) in an area in Norway with low acid deposition. Soil solution concentrations of Al were increased to potentially toxic levels (up to 500 mu mol L-1) and base cation (Ca + Mg + K) to inorganic Al ratios in the soil solution in the root zone were mostly below 1 in the Al-addition treatments. In the control treatment (only water addition) Al concentrations did not exceed 15 mu mol L-1 and base cation to inorganic Al ratios were above 1. The toxic effects of Al on fine root growth and plant growth found in hydroponic studies and pot trials are not confirmed by this field manipulation. However, magnesium (Mg) contents in needles decreased significantly and persistently in plots with elevated Al concentrations, whereas the needle Ca content did not respond. The depletion of the Mg content in needles is suggested to be due to antagonistic effects of high Al concentrations at the root surface, consistent with observed reductions in Mg to Al ratio of inner bark. This study clearly supports a role for Al in critical load functions for forests as dissolved Al causes a decrease in uptake of Mg. However, other signs of reduced forest vitality were not observed. Soil base cation status may need to be included in risk evaluations of forest health under acid deposition. (C) 2010 Elsevier B.V. All rights reserved.
Abstract
Earliness, fruit yield and quality of six annual-fruiting raspberry (Rubus idaeus L.) cultivars were tested under protected cultivation in a cool Nordic environment. After raising plants for 5 weeks in greenhouses with average mean temperatures of 20 degrees C, 22 degrees C, or 26 degrees C, the plants were cropped in an open plastic tunnel at latitude 61 degrees N. The highest yielding cultivars were 'Autumn Bliss' and 'Polka', with 640 g plant(-1). Overall, the most promising cultivar was 'Polka' which combined high yield with large fruit of good flavour and firmness. In earliness, 'Polka' was surpassed only by 'Autumn Bliss', which confirmed its position as the earliest commercial annual-fruiting cultivar. However, 'Autumn Bliss' had soft fruits with little flavour and a short shelf-life, which greatly reduced the potential of the cultivar for the fresh fruit market. The later ripening cultivar 'Erika' did not complete its crop under these conditions, but its large unrealised yield potential and good fruit quality rendered it extremely promising for environments with a longer growing season. 'Sugana' was late, with low yields and poor fruit quality, while 'Marcela' did not yield enough fruit to be of interest under the present conditions. High temperatures during the 5-week raising period generally advanced flowering and fruit ripening in all cultivars, with the notable exception of 'Autumn Treasure' in which flowering was suppressed and strongly delayed by high temperature. Under the present conditions, there was a highly positive correlation between earliness and fruit yield. Regression analyses identified a low number of dormant buds as the single most important component of plant architecture associated with high fruit yield, accounting for 47% of the total variation.
Abstract
Le gel printanier peut etre dommageable pour les semis de Picea abies (L.) Karst. nouvellement plantes si leur rythme de croissance n'est pas suffisamment adapte aux conditions climatiques de la station forestiere. Les objectifs de cette etude consistaient a determiner de quelle facon le debourrement et la resistance au gel printanier sont influences par un traitement de jours courts (JC) appliques a differents moments et avec differents regimes de temperature durant la periode de formation des bourgeons. A la suite d'un entreposage hivernal, la resistance au gel a ete evaluee apres une, trois et cinq semaines dans des conditions de forcage. Le traitement JC a avance le debourrement comparativement aux semis temoins. Par comparaison, le moment du traitement et les differentes temperatures ont eu peu d'effet sur le debourrement. Le traitement JC a augmente la resistance au gel des aiguilles d'un an pendant la periode de desendurcissement. Applique tot, le traitement JC a augmente la resistance au gel des aiguilles d'un an et le diametre au collet comparativement a une application plus tardive. Il est important que la periode de noirceur atteigne une duree critique lorsque le traitement JC prend fin pour eviter une deuxieme eclosion des bourgeons. Des temperatures basses a la suite du traitement JC ont augmente la resistance au gel des aiguilles et diminue celle de la tige. Les effets contraires de la temperature sur differents tissus vegetaux demontrent l'importance d'examiner differents tissus apres des essais de gel-degel. Spring frost may result in detrimental damage in newly planted Picea abies (L.) Karst. seedlings if their growth rhythm is not sufficiently adapted to the climatic conditions on the forest site. The aims of this study were to evaluate how bud break and spring frost hardiness were influenced by short-day (SD) treatments with different timing and different temperature regimes during bud formation. Following winter storage, frost hardiness was tested after 1, 3 and 5 weeks in forcing conditions. The SD treatment advanced bud break compared with the control seedlings. In comparison, the effects of timing and the different temperatures on bud break were small. The SD treatment improved frost hardiness in first-year needles during dehardening. The early SD treatment resulted in improved frost hardiness in first-year needles and greater root collar diameter compared with later SD treatment. To avoid a second bud flush, it is important that a critical night length is attained when the SD treatment terminates. Low temperatures following the SD treatment resulted in increased hardiness of the needles and decreased hardiness of the stems. The contrasting effect of temperature in different plant tissues demonstrates the importance of examining different tissues following freezing tests.
Abstract
Norway spruce expresses a temperature-dependent epigenetic memory from the time of embryo development, which thereafter influences the timing bud phenology. MicroRNAs (miRNAs)are endogenous small RNAs, exerting epigenetic gene regulatory impacts. We have tested for their presence and differential expression. We prepared concatemerized small RNA libraries from seedlings of two full-sib families, originated from seeds developed in a cold and warm environment. One family expressed distinct epigenetic effects while the other not. We used available plant miRNA query sequences to search for conserved miRNAs and from the sequencing we found novel ones; the miRNAs were monitored using relative real time-PCR. Sequencing identified 24 novel and four conserved miRNAs. Further screening of the conserved miRNAs confirmed the presence of 16 additional miRNAs. Most of the miRNAs were targeted to unknown genes. The expression of seven conserved and nine novel miRNAs showed significant differences in transcript levels in the full-sib family showing distinct epigenetic difference in bud set, but not in the nonresponding full-sib family. Putative miRNA targets were studied. Norway spruce contains a set of conserved miRNAs as well as a large proportion of novel nonconserved miRNAs. The differentially expression of specific miRNAs indicate their putative participation in the epigenetic regulation.
Authors
May Sæthre Arnstein Staverløkk Eline HågvarAbstract
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Abstract
Studying the winter survival of forage grasses under a changing climate requires models that can simulate the dynamics of soil conditions at low temperatures. We developed a simple model that simulates depth of snow cover, the lower frost boundary of the soil and the freezing of surface puddles. We calibrated the model against independent data from four locations in Norway, capturing climatic variation from south to north (Arctic) and from coastal to inland areas. We parameterized the model by means of Bayesian calibration, and identified the least important model parameters using the sensitivity analysis method of Morris. Verification of the model suggests that the results are reasonable. Because of the simple model structure, some overestimation occurs in snow and frost depth. Both the calibration and the sensitivity analysis suggested that the snow cover module could be simplified with respect to snowmelt and liquid water content. The soil frost module should be kept unchanged, whereas the surface ice module should be changed when more detailed topographical data become available, such as better estimates of the fraction of the land area where puddles may form.
Authors
Aruppillai Suthaparan Sissel Torre Arne Stensvand Maria Herrero Rolf Inge Pettersen David M. Gadoury Hans Ragnar GislerødAbstract
When rose plants bearing colonies of Podosphaera pannosa were placed in a wind tunnel, the number of conidia trapped was directly proportional to intensity of daylight-balanced (white) light from 5 to 150 mu mol m(-2) s(-1). Illumination of samples using blue (420 to 520 nm) light-emitting diodes (LEDs) increased the number of conidia trapped by a factor of approximately 2.7 over white light but germination of conidia under blue light was reduced by approximately 16.5% compared with conidia germination under white light. The number of conidia trapped under far-red (>685 nm) LEDs was approximately 4.7 times higher than in white light, and 13.3 times higher than under red (575 to 675 nm) LEDs, and germination was not induced compared with white light. When mildewed plants were exposed to cycles of 18 h of white light followed by 6 h of blue, red, far-red light, or darkness, light from the red LEDs reduced the number of conidia trapped by approximately 88% compared with darkness or far-red light. Interrupting the above dark period with 1 h of light from red LEDs also reduced the number of conidia trapped, while a 1-h period of light from far-red following the 1 h of light from red LEDs nullified the suppressive effect of red light. Our results indicate that brief exposure to red light during the dark interval may be as effective as continuous illumination in suppressing powdery mildew in greenhouse rose plant (Rosa x hybrida).