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.
2006
Sammendrag
Dormancy and flowering responses of the strawberry cultivars Korona and Elsanta have been studied in controlled environments. After short day (SD) floral induction for 5 weeks at temperatures ranging from 9 to 27°C, long photoperiods only were required for optimal leaf and inflorescence growth and development at 18°C, with no additional effect of chilling. However, with extended SD treatment for 10 or 15 weeks at 15°C the plants entered the usual semi-dormant state typical for strawberry plants in late autumn, and subsequent long day (LD) conditions could not fully reverse the restrained growth habit. Extended SD treatment at 6°C did not bring about this dormant state, indicating that the dormancy-inducing effect of SD is continuously nullified by such low temperature. When SD induced plants were forced under continued SD conditions, leaf and inflorescence growth were strongly restrained even in plants that had been chilled for up to 6 weeks. The restrained plant growth habit attained in SD, proved not to be a reliable indicator of the dormant state of the plants as it occurred also at low temperature. Floral induction in `Korona" and `Elsanta" was shown to have an obligatory SD requirement at temperatures ranging from 9 to 21°C, while SD floral induction was marginal at 27°C. The floral inducing effect of SD was also strongly reduced at temperatures below 9°C. Application of these findings for multiple cropping of inherently single-cropping strawberry cultivars in winter season greenhouse production systems is discussed.
Sammendrag
Early cut organic grass silage was compared with silage harvested 17 days (180 daydegrees) later in a continuous production experiment with 32 Norwegian Red dairy cows in early lactation. A half of the cows received a feed ration with 40% concentrates (H), and the other half 10% (L) on an annual energy basis. Early cut resulted in lower crop yields (2.17 t DM/ha) compared with normal cut (4.66 t DM/ha). Energy and protein concentrations were higher for early cut than for normal cut silage (6.4 vs. 5.6 MJ NEl, as assessed by NIRS, 136 vs. 105 g/kg DM CP). Feeding early cut silage of an organic ley increased feed intake. Cows at H produced 27.5 kg ECM per day with early cut silage and 25.3 kg ECM with normal cut silage, and cows at L produced respectively 24.7 and 22.4 kg ECM. Cows offered early cut silage had highest milk protein concentration (H: 34.6 vs. 32.8; L: 34.4 vs. 31.4 g/kg). In the present experiment the harvesting time did not influence the sensoric quality of milk, but low concentrate level reduced the milk taste slightly. Therefore early cut may only be recommended to farmers in northern Norway when acerage is not a limiting factor.
Forfattere
Grete Waaseth Roar Moe Royal D. Heins Svein GrimstadSammendrag
Varying photo thermal ratios (PTR) were supplied to Salvia x superba Stapf "Blaukönigin" during pre-inductive vegetative development with the exception of a short germination period under uniform conditions. In addition, both unvernalized plants and plants receiving a saturating vernalization treatment of 6 weeks at 5 oC were given two photosynthetic photon flux (PPF) levels (50 or 200 µmol m-2 s-1) during subsequent inductive 16-hour long days. There were no effects of PTR treatments during vegetative development on subsequent flowering. However, the higher PPF level during inductive long days significantly accelerated floral evocation in unvernalized plants, lowering the leaf number at flowering. The effect was practically negligent after the vernalization requirement was saturated. In a second experiment, varying periods (4, 7, 10, and 14 days or until anthesis) at a PPF of 200 µmol m-2 s-1 during 20-hour days were given at the beginning of a long day treatment, either with or without preceding vernalization treatment. Flowering percentage increased considerably as the period at 200 µmol m-2 s-1 was extended compared with plants grown at a lower PPF of 50 µmol m-2 s-1. However, the leaf number on flowering plants was not affected, except in unvernalized plants receiving the highest PPF continuously until anthesis, where leaf number was reduced by almost 50%. We propose that the PPF dependent flowering is facilitated either by the rate of ongoing assimilation or rapid mobilization of stored carbohydrates at the time of evocation. Abortion of floral primordia under the lower PPF (50 µmol m-2 s-1) irrespective of vernalization treatment indicates that the assimilate requirement for flower bud development is independent of the mechanism for floral evocation.
Forfattere
Anne Kristine Søvik Bjørn Kløve Kaisa Haikkinen J. Augustin Jari Huttunen J.M. Necki Satu Karjalainen Anu Liikanen Ülo Mander Markku Puustinen S. Teiter P. WachniewSammendrag
The potential atmospheric impact of constructed wetlands (CWs) should be examined as there is a worldwide increase in the development of these systems. Fluxes of N2O, CH4, and CO2 have been measured from CWs in Estonia, Finland, Norway, and Poland during winter and summer in horizontal and vertical subsurface flow (HSSF and VSSF), free surface water (FSW), and overland and groundwater flow (OGF) wetlands. The fluxes of N2O-N, CH4-C, and CO2-C ranged from "2.1 to 1000, "32 to 38 000, and "840 to 93 000 mg m"2 d"1, respectively. Emissions of N2O and CH4 were significantly higher during summer than during winter. The VSSF wetlands had the highest fluxes of N2O during both summer and winter. Methane emissions were highest from the FSW wetlands during wintertime. In the HSSF wetlands, the emissions of N2O and CH4 were in general highest in the inlet section. The vegetated ponds in the FSW wetlands released more N2O than the non-vegetated ponds. The global warming potential (GWP), summarizing the mean N2O and CH4 emissions, ranged from 5700 to 26000 and 830 to 5100 mg CO2-equivalents m"2 d"1 for the four CW types in summer and winter, respectively. The wintertime GWP was 8.5-89.5% of the corresponding summertime GWP, which highlights the importance of the cold season in the annual greenhouse gas release from north temperate and boreal CWs. However, due to their generally small area North European CWs were suggested to represent only a minor source for atmospheric N2O and CH4.
Sammendrag
Six cropping systems, ranging from conventional arable without livestock to organic livestock farming with few arable crops, have been compared since 1989 on a loam soil. Soil structure indicators measured initially included organic matter levels, pore size distribution and air permeability. These parameters were re-measured after 15 years, when the size distribution and stability of aggregates was also measured. A decline in soil structure quality was found in the system with conventional autumn ploughing with no rotational grass. This system had higher bulk density and mean aggregate size than other systems, and lower levels of plant available water and aggregate stability. Opposite trends were related to the proportion of grass leys in the other systems and to their levels of soil organic matter. The latter declined markedly over 15 years in the conventional arable system, and there were smaller declines in most other systems. In an arable system without ploughing, organic matter was maintained and high structural stability was found. This system had high bulk density, but the proportion of small aggregates equalled that found in the systems with ley. Satisfactory soil structure was maintained in systems with 50% leys in the rotation, in agreement with Norwegian long-term studies of the effect of crop rotation type on soil organic matter. Though the deterioration of soil structure in the all-arable system was not extreme, as the soil had good structure initially, the results have serious implications for the sustainability of stockless arable systems on soils with a less favourable starting point.
Forfattere
Jens G Hansen Arne Hermansen Leontine T Colon David E L Cooke Björn Andersson Bent Nielsen Ulrich Darsow Jozsef Bakonyi Poul Lassen Alison K LeesSammendrag
The Concerted Action on potato late blight `Eucablight" (www.eucablight.org) was launched in 2003 to promote collaboration between researchers across Europe and to collate the previously fragmented data on host resistance to late blight and characterization of its causal pathogen, Phytophthora infestans. Central to the project was the development of standardized protocols, databases and data collection tools with which data from across Europe could be centralized. The ultimate aim was to capitalize on the vast resource of data available in order to allow a pan-European analysis to be conducted. The P. infestans database is currently populated with information relating to over 13,800 isolates from 20 European countries. The host resistance database holds primary disease data and derived statistics from more than 50 field trials assessing mainly foliage blight resistance. The use of seven standard cultivars in these trials facilitated the comparison of resistance information across years and regions. The host database is structured, and made accessible, in such a way that DSS builders can access the model parameters they need to construct locally adapted forecasting systems. In this presentation we describe the data collection and data analyzing tools that have been developed in this project and how they are directly applicable to other host-pathogen systems.
Forfattere
Thomas Hartnik Frans Busser John Jensen Joop HermensSammendrag
During the last years biomimetic extractions have become quite popular to assess the bioavailable fraction in soils and sediments. These techniques can be divided in depleting and non-depleting techniques, those that are based on depletion of the aqueous phase and subsequent desorption of the weakly bound fraction of a compound, and those that try to avoid disturbing the equilibrium between solid and aqueous phase. We have performed experiments that try to identify chemical extraction methods that mimic exposure of earthworms for the non-ionic insecticide "-cypermethrin. The extractable amounts that were achieved by the different extraction techniques were then related to internal concentrations in earthworms and sublethal toxicity for earthworms. Extraction of soil using ß-cyclodextrin was used as a depletive method. The extraction was based on a method developed by Reid et al (2000) and optimized regarding extraction time, cyclodextrin concentration and analysis of the extracted fraction. Non-depletive solid phase microextraction (nd-SPME) was used as a non-depletive technique. As shown earlier the technique can be used to assess concentrations of freely dissolved compound in porewater. Our results show that at low concentrations (< 25 mg/kg) cyclodextrin-extractability correlate well with uptake of "-cypermethrin in earthworm. However, at high concentrations ß-cyclodextrin tends to overestimate uptake in earthworms. Non depletive SPME-extraction precisely mimics the uptake of "-cypermethrin in earthworms both at low and high compound concentrations in soil. Differences between the extraction techniques will be discussed and explanation for the different extraction patterns given.
Sammendrag
The occurrence of Fusarium (represented by Fusarium spp. and Microdochium nivale) has been recorded in barley, oats and spring wheat seeds in Norway since the 1970-ies as part of the seed quality assessment. Annually a large number of samples representing both certified and farm saved seed from all cereal growing areas, was tested (100 or 200 seeds from each sample) at the Seed Testing Laboratory using the freezing blotter, the Doyer filter paper, and/or the agar plate (PDA) methods. In total, almost 30 000 samples of barley, more than 16 000 samples of oats and more than 9 000 samples of spring wheat were tested. The Fusarium frequencies were recorded in each sample, a mean of all samples was calculated each year for each cereal species, and multiple regressions with weather data from the growing season and also the Fusarium incidences in seed the previous year, were carried out. 69 % of the variation of the incidence of Fusarium in barley seeds was explained by 1) precipitation in July, 2) the incidence of Fusarium the previous year (both significant positive effects), and 3) precipitation in June, 4) temperature in July (both significant negative effects). In oat seed, precipitation in July and incidence of Fusarium the previous year explained 59 % of the variation. In spring wheat, as for barley and oats, precipitation in July and the incidence of Fusarium the previous year contributed positively, whereas precipitation in May and temperature in August had a negative effect.These four factors contributed significantly by 58% to the variation of Fusarium in spring wheat seed. It is concluded that the incidence of Fusarium in seed the previous year and precipitation in July were the main factors affecting the incidence of Fusarium in cereal seeds in Norway.
Forfattere
Venche TalgøSammendrag
On the southwest coast of Norway there are natural stands of holly (Ilex aquifolium), but a number of different varieties of I. aquifolium and I. meserveae are also grown in bough production fields, private gardens and public parks. Except for conifers, holly is the only tree we have with green foliage during the winter in Norway. The leathery, dark green leaves with prickly spines and the red berries have made holly a popular plant for Christmas decorations. Leaf-drop/defoliation has become an increasing problem during the last decades both before and after harvest, and thus destroys the marketability. We suspect that reduced grazing has resulted in more overgrown/dense stands and hence created ideal microclimate for fungal growth. Wet foliage due to shade and restricted air movement gives the spores good conditions for germination. On investigated diseased plant material collected from holly in the period 2001-2006, a number of possible pathogenic fungi were isolated; Fusarium avenaceum, Vialaea insculpta, Nectria sp., Colletotrichum acutatum, Trochila ilicina and Diaporthe ilicis (Talgø et al. 2006). The fungi were identified morphologically mainly based on information given by Ellis & Ellis (1997). Colletotrichum was identified to species level by PCR. In the literature we find very little about what kind of damage these organisms may cause on holly. Benson & Jones (2000) say that leaf-spotting fungi on holly can cause heavy defoliation before new growth starts in the spring, but they do not mention any specific pathogen. Therefore we will run pathogenesis tests with all the fungi mentioned above to fulfil Koch"s postulate.
Forfattere
Erik LysøeSammendrag
Flere av de soppartene som naturlig finnes i korn, kan produsere giftstoffer. Det er et mål å redusere mengden av slike sopptoksiner til et nivå som gjør at vi trygt kan benytte kornet som råstoff for produksjon av mat eller dyrefòr. Den viktigste kilden til mykotoksiner ute på kornåkeren er Fusarium. Ulike Fusarium-arter kan produsere flere forskjellige mykotoksiner. Kunnskap om hvordan denne produksjonen skjer kan bidra til å redusere dette problemet.Ved å studere prosesser i Fusarium-sopper som produserer store mengder av soppgiften zearalenon, har de klart å frambringe viktig kunnskap om hvordan denne soppgiften dannes i soppen. Zearalanon er en østrogenlignende forbindelse som virker som en hormonhermer i mennesker og dyr, og er et av de vanligste mykotoksinene man finner i korn. Flere soppgener som var mye mer aktive når zearalenon ble produsert enn når denne forbindelsen ikke ble laget, ble funnet og karakterisert. Det ble laget en Fusarium-mutant der ett av soppgenene, PKS4, var inaktivert. Denne mutanten hadde mistet sin evne til å produsere zearalenon. På denne måten kunne man sikkert identifisere ett av flere gener som var absolutt nødvendig for at Fusarium skulle kunne lage dette toksinet. Genet PKS4 kodet for en polyketidsyntase, og hvordan aktiviteten av dette og andre gener ble regulert når zearalenon ble laget, ble studert i mer detalj. Aktiviteten av de samme genene ble også studert i unge hvete- og havrekorn som var smittet med Fusarium. Zearalenon sin rolle i soppen var tidligere ukjent, men basert på resultater framkommet i dette arbeidet er man ett skritt nærmere en forståelse av denne prosessen.