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
Nina Heiberg Arnfinn NesSammendrag
The aim of this work was to find methods of producing red raspberry long canes of good quality in a Northern climate with a short growing season. Plants of two red raspberry cultivars ("Glen Ample" and "Glen Moy") were produced from roots in February and March. The plants were left in a greenhouse during spring. During summer the plants were placed in three different environments: outdoor, under rain cover and in polyethylene tunnels; and in December, the plants were moved into cold store (-1o C). The plants had one cane each. They were taken out of cold store at two times: 15 May and 15.June and placed into a plastic tunnel for berry production. The experiment was carried out at two different places and replicated twice. The best development of long canes was obtained by growing them in polyethylene tunnel during summer and autumn the first year. These plants also developed more laterals and flowers per laterals, and gave the highest yield. The plants grown under rain cover gave higher yield than plants grown outdoors. Prolonging the cold storage of the plants from 15 May to 15 June reduced the yield by 22 %. The reduction in yield was first of all a result of a reduction in the number of berries. The cultivar "Glen Ample" gave higher yield than cv. "Glen Moy" in all treatments. Based on the results of these experiments, use use of polyethylene tunnels or rain cover for long cane production of red raspberry in Northern climate with short growing season is recommended. Delaying the harvest season by prolonging the cold storage period in spring reduced the yield, but higher prices in autumn may make it profitable.
Sammendrag
Berry damage by the larva of raspberry beetle (Byturus tomentosus) is a major risk for growers of organic raspberry. The identification of two volatile compounds in raspberry flowers that are attractive to the beetle by scientists at SCRI has facilitated the idea of mass trapping as an alternative control method to using conventional insecticides. The challenges are to design efficient and user-friendly traps, and to document if and how such traps can reduce the number of ovipositing beetles sufficiently to get a low level of berry damage. These questions are being investigated as part of a large U.K. project (Defra HortLINK) which is developing IPDM (Integrated Pest and Disease Management) for protected raspberries. We here report the results from a cooperating Norwegian project in which the volatile ‘compound B" was used in pilot trials, 2003-2006. A combined collision-funnel trap from SCRI and AgriSense with the compound in a slow release lure attracted and killed a high number of raspberry beetles in the weeks before flowering, but more studies are needed to find a trap strategy that consistently leads to less berry damage. Norwegian organic fields are small, with large populations of raspberry beetle, and usually with wild raspberry growing nearby. A successful mass trapping strategy must therefore pay equal attention to immigrating and resident beetles.
Forfattere
S. Ulland E. Ian R. Mozuraitis A.-K. Borg-Karlson Richard Meadow H. MustapartaSammendrag
The cabbage moth, Mamestra brassicae L. (Lepidoptera, Noctuidae), is a polyphagous species that is often choosing plants of Brassica as hosts for oviposition. In the search for biologically relevant odorants used by these moths, gas chromatography linked to electrophysiological recordings from single receptor neurons (RNs) has been employed, resulting in classification of distinct types of neurons. This study presents specific olfactory RNs responding to methyl salicylate (MeS) as primary odorant and showing a weak response to methyl benzoate, the 2 aromatic compounds occurring together in several plant species. In 2 cases, the neuron was colocated with another RN type responding to 6 green leaf volatiles: 1-hexanol, (3Z)-hexen-1-ol, (2E )-hexen-1-ol, (3Z )-hexenyl acetate, (2Z )-hexen-1-ol, and an unidentified compound. Whereas the specific RNs detected the minor amounts of MeS in some plants, the compound was not found by gas chromatography linked to mass spectrometry in intact plants, but it was found after herbivore attack. The behavioral effect of MeS was studied in outdoor test arenas with Brassica napus and artificial plants. These experiments indicated that mated M. brassicae females avoid plants with dispensers emitting MeS. As it is induced by caterpillar feeding, this compound may mediate a message to mated M. brassicae females that the plant is already occupied.
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
David M. Gadoury Arne Stensvand Robert C. Seem Catherine Heidenreich Maria Herrero Mary Jean Welser Andrew Dobson Håvard Eikemo Belachew AsalfSammendrag
Cleistothecia on leaves of deciduous perennials are often dispersed before leaf fall to other substrates. In contrast, strawberry leaves remain attached during winter, and cleistothecia of Podosphaera macularis remained attached to these leaves. Release of overwintered ascospores was coincident with renewed plant growth, and pathogenicity of ascospores was confirmed. Upper and lower surfaces of emergent leaves were similarly susceptible, but upper surfaces were obscured by folding in emergent leaves. Emergent leaves exposed to airborne inoculum developed severe infection of the lower surface, but not the obscured upper surface. Emergent leaves acquired ontogenic resistance during unfolding, and the upper leaf surface thereby escaped infection. We found no evidence that the pathogen survives winters in New York, USA or Norway within crown tissue. Plants stripped of infected leaves remained mildew-free when forced after overwintering, while mildew colonies commonly developed on emergent leaves of plants not stripped of mildewed leaves. Unsprayed plots established using mildew-free plants either remained asymptomatic or developed only traces of powdery mildew during one growing season, even when located within 100 to 150 meters of severely diseased plots. In summary, our results suggest the following: (i) sanitation, use of disease-free plants, and eradicative treatments could contribute greatly to management of strawberry powdery mildew; (ii) cleistothecia represent a functional source of primary inoculum; and (iii) the common observation of higher mildew severity on lower leaf surfaces may reflect escape of the upper epidermis due to the combined effect of leaf folding and rapid acquisition of ontogenic resistance.
Forfattere
May Bente BrurbergSammendrag
The oomycetes form a diverse group of eukaryotic microorganisms comprising several notorious pathogens of plants, insects, crustaceans, fish, vertebrates, and various microbes. Several pathogenic oomycetes are responsible for massive destruction and huge losses in agriculture, aquaculture and natural environments. Oomycetes belong to the stramenopiles, a major line of eukaryotes, and are most closely related to algae and unicellular diatoms. They display hyphal growth and spore types that are morphologically and physiologically similar to fungi. However, their parasitic lifestyles have independent evolutionary origins. The plant pathogenic species, in particular the genus Phytophthora, have been studied most extensively and will be focused on in the lecture. The majority of the approximately 80 Phytophthora species that have been described are distinguished by their complex life histories, with both asexual and sexual phases and a number of associated reproductive structures. Plant pathogens secrete an array of effector molecules that facilitate infection of their hosts. Some effectors, called avirulence (Avr) proteins, display specific gene-for-gene interactions with host resistance proteins. Recent characterization of four oomycete Avr genes revealed that they encode proteins with a common modular structure, including N-terminal conserved RXLR-dEER motifs required for targeting these effectors into host cells. The presence of such a conserved "tag" has provided a tool for discovering the otherwise structurally diverse Avr genes present in five recently sequenced genomes of oomycetes. Bioinformatic analysis has identified about four hundred potential genes encoding secreted RXLR-dEER class proteins in each of the genomes of P. infestans, P. sojae and P. ramorum. The genome sequences have also revealed many other protein families possibly associated with plant infection such as hydrolases, ABC transporters, protein toxins and proteinase inhibitors. The next challenge is to understand how these proteins together with the RXLR-dEER effectors function to establish infection of their host plants.
Forfattere
Anne-Kristin LøesSammendrag
Prosjektet "Frafallet blant norske økobønder ? hva er årsakene?" (2007-08) har gjennomført en spørreundersøkelse blant alle bønder som meldte seg ut av den økologiske sertifiseringsordningen og dermed ut av Debio mellom 2004 og 2007. Spørreskjemaet ble også sendt til en kontrollgruppe med bønder som drev økologisk i 2006. Alle bøndene i undersøkelsen hadde et driftsomfang som gjorde at de var kvalifisert til å motta produksjonstilskudd. Resultatene ble sammenstilt med opplysninger fra Statens landbruksforvaltning om arealer og dyretall. Et urovekkende resultat er at 25% av dagens økobønder planlegger å melde seg ut av Debio-ordningen i løpet av 5-10 år. Av dem som vil slutte er det 20% som vil legge ned drifta, 40% som vil gå over til konvensjonell drift, og hele 40% som vil drive etter økologiske retningslinjer, men uten Debiogodkjenning. Når det gjelder dem som har meldt seg ut, er det 55% av disse som nå driver konvensjonelt. 10% har startet opp igjen som Debiobønder,16% har lagt ned drifta, og 18% hevder at de driver etter økologiske retningslinjer uten sertifisering. Siden Debio-sertifisering er en forutsetning for å motta tilskudd til økologisk produksjon er det overraskende at så mange bønder er interessert i økologisk landbruk, men ikke godkjenningsordningen. For mye byråkrati med Debiosertifisering og ?kontroll ble da også oppgitt som den klart viktigste årsaken til utmelding av dem som hevder å drive etter retningslinjene, men uten Debio-inspeksjoner. For dårlig lønnsomhet og usikkerhet rundt landbrukspolitikken var også viktige årsaker til utmelding, mens sosiale forhold som manglende støtte fra familie og naboer var av liten betydning. Resultatene blir nå analysert statistisk, og bearbeidet ved hjelp av en teoretisk beslutningsmodell.
Forfattere
Peder Lombnæs Andrew C. Chang Bal Ram SinghSammendrag
Abstract: A series of experiments were conducted to examine the interactive effects of an organic ligand, a competing cation, and PH on the dissolution of zinc (Zn) from three California soils, Maymen sandy loam, Merced clay, and Yolo clay loam. The concentrations of soluble Zn of the three soils were low in a background solution of Ca(NO3)(2). Citric acid, a common organic ligand found in the rhizosphere, was effective in mobilizing Zn in these soils; its presence enhanced the concentration of Zn in soil solution by citrate forming a complex with Zn. The ability of Zn to form a complex with citric acid in the soil solution was dependent on the concentration of citric acid, PH, and the concentration of the competing cation Ca2+. The PH of the soil solution determined the extent of desorption of Zn in solid phase in the presence of citric acid. The amounts of Zn released from the solid phase were proportional to the concentration of citric acid and inversely proportional to the concentration of Ca(NO3)(2) background solution, which supplied the competing cation Ca2+ for the formation of a complex with citrate. When the soil suspension was spiked with Zn, the adsorption of Zn by the soils was retarded by citric acid via the formation of the soluble Zn-citrate complex. The dissolution of Zn in the presence of citric acid was PH dependent in both adsorption and desorption processes.
Forfattere
Ari Lehtinen Asko Hannukkala Björn Andersson Arne Hermansen Vinh Hong Le Ragnhild Nærstad May Bente Brurberg Bent J Nielsen Jens G Hansen Jonathan YuenSammendrag
A total of 743 single-lesion isolates of Phytophthora infestans were collected in summer 2003 from Denmark, Finland, Norway and Sweden. Most of the isolates were tested for mating type, snd subsets for sensitivity to fungicides and virulence (host specific pathogenicity). Approximately 60 % of the isolates were A1 mating type in each country. Both mating types were present in 40 % of the fields where more than one isolate was tested,indicating strong potential for sexual reproduction. The proportion of metalaxyl-resistant isolates dropped under 15 % from the 60% observed in the early 1990s in Norway and Finland, possibly due to lower selection pressure because of decreased use of metalaxyl. PropamocarbHCl sensitivity remained unchanged in the Nordic countries compared to the situation in 1997-2000 in Finland. Four isolates collected from Finland and Sweden were able to sporulate in the presence of this fungicide at a concentration of 1000 mg L-1. In Norway and Finland the frequencies of virulence factors and pathotypes remained nearly unchanged since 1990s, but the mean number of virulence factors per isolate increased from 5.6 to 6.3. In Denmark and Sweden virulence factors 2 and especially 6 were more common than in Norway and Finland. In addition, in the Swedish population the frequencies of pathotypes were quite even while in other countries pathotype 1.3.4.7.10.11 was most prevalent.
Forfattere
Knut Anders Hovstad Mikael OhlsonSammendrag
A field experiment was conducted in a semi-natural grassland to study the interspecific variation in the effect of litter on seedling emergence and establishment and separate physical from chemical effects. Seeds of seven forb species were sown in plots subjected to either litter amendment (0, 400 or 900 g m–2) or water extracts of litter (corresponding to 400 and 900 g litter m–2). In addition, an extract was treated with activated carbon to estimate the possible effects of secondary chemical compounds.The response to plant litter differed amongst species: negative, neutral and positive responses were observed. Anthriscus sylvestris was the only species with a strong positive response to litter. We found no consistent relation between seed size and response to plant litter. Physical effects of litter were generally stronger than chemical effects. However, water extract of litter inhibited emergence in three species. Activated carbon removed the negative effect of the litter extract, which suggests that the effect was caused by an inhibitory chemical compound rather than by increased competition in response to nutrients added via the extract. The balance between facilitative and inhibitory effects of litter depended on species identity and litter quantity. Facilitative effects dominated at low and intermediate quantities of litter, and inhibitory effects at high litter quantities. One species, Campanula rotundifolia, showed a switch from positive to negative responses with increasing quantities of litter. However, we found no general threshold for litter quantity valid across species.