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.
2008
Forfattere
Arne Stensvand Heidi Udnes Aamot Gunn Mari Strømeng Venche Talgø Abdelhameed Elameen Jorunn Børve Sonja KlemsdalSammendrag
The ascigerous stage (formation of perithecia with viable ascospores) of Colletotrichum acutatum was recently reported to occur on fruits of highbush blueberry (Vaccinium corymbosum) in Norway. When 113 isolates of C. acutatum from various plant species were cultured on strawberry leaf agar, nine developed perithecia with viable ascospores. Four isolates originated from apple (Malus domestica) and one each from sweet cherry (Prunus avium), raspberry (Rubus idaeus), highbush blueberry (Vaccinium corymbosum), hollyberry cotoneaster (Cotoneaster bullatus), and northern dock (Rumex longifolius). Except from blueberry, we never detected the ascigerous stage on decaying fruits or any other parts of the above mentioned plant species. On potato dextrose agar, colour of the underside of the cultures forming perithecia varied from light grey-green to dark grey-green or dark brown-green. Colour of the upperside varied greatly, being dark grey-green, grey-brown, grey, and beige-pink, and only two of the isolates were beige-pink (the raspberry and blueberry isolates). Amplified fragment length polymorphism (AFLP) analysis of the isolates using six primer combinations resulted in 103 clear polymorphic bands. A dendrogram was constructed, and based on cluster analysis using genetic similarity, the isolates could be divided into several clusters. Eight of nine perithecia-forming isolates grouped together in the dendrogram, indicating genetical difference from other isolates. This was also supported by Principal Coordinate (PCO) analysis.
Sammendrag
Most fungicide applications targeting apple scab aim to control primary infections caused by ascospores and spraying is thereby linked to ascospore availability. We investigated the effect of pre bud break climatic conditions on seasonal patterns of ascospore release. Apple leaves bearing pseudothecia of Venturia inaequalis were overwintered at orchard sites in 8 countries for up to 3 years. Leaf samples were collected 2 to 5 weeks before bud break and again at bud break, air dried, and sent via airmail to Norway. The samples were stored at -18 ºC upon arrival until tested. Disks cut from each replicate leaf sample were incubated moist at 20 ºC to allow ascospore maturation but prevent discharge. Matured ascospores were induced to discharge twice a week and enumerated until the supply was exhausted. The proportion of ascospores ejected was fitted against degree day accumulation using logistic regression. The regression intercept (onset maturation), slope (maturation rate), as well as the absolute number of spores counted differed significantly (P < 0.001, P = 0.05, P < 0.001 respectively) among sites and sampling dates. There was a significant interaction between site and sampling date, indicating that climatic conditions prior to bud break differentially impacted the subsequent ascospore availability. Observed differences could perhaps be used to further refine previously described models of ascospore maturity.
Forfattere
Arne StensvandSammendrag
Black spot caused by Colletotrichum acutatum is occasionally found in strawberry fields in Norway. It was detected for the first time in 1999 and found in certified production in 2002. More than half of the certified nurseries, including the elite plant station, had symptomless infections of C. acutatum in strawberry planting material the following two years. A renovation programme was carried out, and in 2005 and 2006 C. acutatum was found in only one certified nursery. However, in 2007 latent infections of C. acutatum was detected in four certified strawberry plant nurseries. As been reported before from Norway, C. acutatum is present in almost all fruit and berry species grown in the country and has also been found on many ornamentals and in weeds, but it is a quarantine organism only in strawberry. It is particularly severe in cherry and apple. We have detected the perfect stage of the fungus in highbush blueberry, and when isolating the fungus we find a high frequency of isolates forming the perfect stage in culture. When doing genetic analysis (AFLP), the Norwegian isolates from strawberry separated in two groups. One set of isolates grouped together with strawberry isolates of C. acutatum from other countries, and the other set grouped with Norwegian isolates from several hosts, with a majority of isolates from sweet- and sour cherry. The latter group had more than 90% similarity between the polymorphic bands. There was also a third, very genetically diverse group of isolates that included most of the perithecia forming isolates. Further research will reveal if isolates from the different groups may vary in their aggressiveness to strawberry and if it will be possible to distinguish between them in simple molecular tests.
Forfattere
Arne Stensvand Maria Herrero Håvard Eikemo Andrew Dobson Belachew Asalf David M. Gadoury Robert C. Seem Catherine Heidenreich Mary Jean WelserSammendrag
Artikkelen omtalar resultat frå eit 4-årig prosjekt om mjøldogg i jordbær.
Sammendrag
Artikkelen omhandlar rotstokkrote og lerrote i jordbær som begge er årsaka av Phytophthora cactorum.
Forfattere
Arne Stensvand Maria Herrero Håvard Eikemo Andrew Dobson David M. Gadoury Robert C. Seem Catherine Heidenreich Mary Jean WelserSammendrag
Artikkelen gir ein kort omtale av resultat frå eit forskingsprosjekt om mjøldogg i jordbær.
Forfattere
Arne StensvandSammendrag
Artikkelen er ein omtale av Signum (aktive stoff: pyraklostrobin og boskalid) og inkluderer resultat frå utprøvingar av preparatet i Noreg.
Sammendrag
Incomplete combustion during vegetation fire can lead to the conversion of plant and soil organic matter (OM) into charcoal. The thermally altered OM is considered to contribute to the stable pool of soil C. Most of the data on thermal alteration of plant material were obtained in the laboratory, whereas fire consequences on ecosystem C storage calls for data collected in natural-fire conditions. The objective of this study was to relate the quality of visually-identified litter charcoal and the temperature recorded during a scrubland prescribed fire. Litter was sampled before and after the fire along a transect in the 30 ha experimental site. Litter-size fractions were analyzed for chemical composition and properties by elementary and isotopic analysis, solid-state 13C nuclear magnetic resonance spectroscopy, differential scanning calorimetry and quantification of oxidation-resistant pyrogenic C. The maximum temperature reached within the litter layer during fire was assessed with thermo-sensitive paints. Our results showed that fire had little effect on bulk litter composition because the fire event induced a large litter fall of both charred and non-charred material, resulting in the impossibility to distinguish new-litter-input and charring processes. As a consequence, the visual identification and separation of burned and unburned material constituted an essential preliminary step for chemical characterization of thermally altered organic matter. Fire temperatures ranged from 370 to 650°C. Charring signifi- cantly increased the litter C concentration by 115 to 142 mg g"1 under the effects of dehydration and aromatization processes occurring above 370°C. A significant correlation appeared between the production of aromatic structures, the decrease of O-alkyl C contribution and the temperature. The relationship between the maximum temperatures reached during the natural fire and the chemical transformation of the litter organic matter appeared highly consistent with previous results obtained under controlled conditions. Heating also led to a significant decrease of the 13C that we interpret as a higher thermal sensitivity of 13C-rich molecules. The elemental composition, NMR and thermal spectra are consistent with the low oxidation-resistant C concentration of this natural charcoal (16±5 % OC), reflecting a low condensation degree compared to graphitic-like model. These findings suggest that leaf-derived charcoal produced during natural vegetation fire may have a lower C storage potential than previously assumed.
Forfattere
Marie-France Dignac C Rumpel Daniel Rasse M Mendez-Millan H Bahri S Derenne G Bardoux A MariottiSammendrag
How the chemical composition of plant biomolecules controls their dynamics in soils at the long-term scale remains largely unknown. Stabilisation mechanisms in soils might depend upon the chemical nature of organic matter. These mechanisms either involve soil mineral constituents or are related to chemical recalcitrance of specific molecules such as lignins. Physical and physico-chemical protection mechanisms may act differently on above- and belowground tissues of plants, leading to contrasting contributions of these tissues to soil organic matter (SOM). Cutins and suberins are specific for above and the belowground tissues of higher plants, respectively. Their molecular constituents can be used as biomarkers of the inputs of these plant tissues to soils. In this study, the molecular turnover of specifically plant-derived constituents in soils were estimated using compound specific isotopic tracer techniques applied to agricultural lands converted from C3 plant to C4 plant cropping. We assessed the specific residence times of lignins, cutins and suberins in soils, in order to compare the contributions of above- and belowground tissues to SOM. Lignin turnover in soil was faster than that of total organic carbon. Contrasting dynamics in soils were observed among lignin monomers as well as among cutin/suberin markers, which might be related to their chemical nature, their position into the polymeric structure and/or to the plant tissue in which they are present. This study, combining compound specific isotope measurements with a long term field trial helped understanding soil carbon turnover on a molecular level.
Forfattere
Per StålnackeSammendrag
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