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.
2009
Forfattere
Arnfinn NesSammendrag
Forbruket av frukt og bær har auka mykje siste åra, men det kan gjerne auka endå meir. Det er sortinteresse for meir kunnskap om dei positive komponentane i ferske frukter og bær som vi trur gjev god helse. Antiokidantar er særleg i fokus - og her er mange bærarter viktige sidan dei inneheld store mengder.
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Grønt plantevev i vekst inneholder den ernæringsmessig gunstige omega-3-fettsyren α-linolen. Beiteplanten smyle i et nordlig fjellbeite hadde ikke forskjeller i konsentrasjon av α-linolensyre med hensyn til høstetidspunkt eller nord/sørhelling, men planter ved høyere lokaliteter ble funnet å ha lavere konsentrasjon av spesielt α-linolensyre.
Forfattere
Hanne SickelSammendrag
I prosjektet ”Driftssystemer for et bærekraftig landbruk i fjellbygdene” ble det i 2007 samlet melk fra to besetninger på utmarksbeite i fjellet. Analyser av melken viste et høyere innhold av umettede fettsyrer, antioksidanter og et lavere innhold av mettede fettsyrer sammenliknet med vintermelk og oppgitte standardverdier.
Forfattere
alena gibalova PublikasjonsforfatterSammendrag
Fiberduk og insektnett tjener til utestenging av skadegjørere i hagebrukskulturer. Fiberduk brukes også for å øke temperaturen til å forkorte kulturtiden der dette er ønskelig. I økologisk dyrking er det vanskelig å lykkes uten å bruke fiberduk eller insektnett i skadedyrutsatte områder. Om en skal velge fiberduk eller insektnett blir en vurderingssak - begge har sine fordeler og ulemper.
Forfattere
Ricardo Holgado Kari Anne Oppen Christer MagnussonSammendrag
Soil samples from a growth depression in potato (Solanum tuberosum) cv. Saturna field in Grue, eastern Norway, yielded large numbers of root lesion nematodes, Pratylenchus penetrans. Yield of potato was reduced by 50% in the affected area of the field. Transect-sampling showed plant growth to be negatively correlated with densities of P. penetrans and suggested a damage threshold of potato to the nematode of 100 specimens per 250 g of soil. Common scab (Streptomyces scabies) occurred frequently in the affected area. Pratylenchus penetrans was present in roots, underground stems, stolons and tubers. In tubers, nematodes were detected inside cross-lesions typical of common scab, and occurred also in the outermost 0.5 mm tissue associated with such lesions. On potato cv. Saturna grown in a green-house, P. penetrans alone induced tuber lesions similar to those of common scab. Also, the combined inoculation of the bacterium and the nematode seemed to enhance symptom expression. Pratylenchus penetrans survives storage of potatoes, from which new infections may develop. Hence, potato tubers do appear to be an important means for the spread of P. penetrans to new areas.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Eivind UlebergSammendrag
QTL mapping experiments aim to find the genes or mutations that contribute to phenotypic variance. This knowledge is important for biological understanding and can be utilized, e.g. for medical or breeding purposes. QTL mapping methods can be categorised as linkage analysis (LA) methods, linkage disequilibrium (LD) based methods and methods combining linkage and linkage disequilibrium analysis (LLD). The basic difference between LA and LD analysis is the calculations of the probability that two animals carry genes that are identical-by-descent (IBD) at a given point on the chromosome. LA is based on within family IBD, whereas LD is based on population-wide IBD probabilities. LA analysis is dependent on recombinations that can be observed in the genotyped data, which limits the accuracy. LD is based on historical recombinations and can find short confidence intervals, but is likely to result in false positives due to spurious associations between markers and QTL. To avoid the problems of separate LA or LD analysis, approaches combining linkage and linkage disequilibrium mapping (LLD) have been proposed. The main objective of this thesis has been to make maximum use of genotyping information from QTL mapping experiments for detecting as many as possible QTL and position them as precisely as possible. Specific issues addressed have been single versus multiple mapping methods (paper 1), the effects of including the causative mutation amongst the markers in QTL mapping experiments (paper 2) and developing a statistical test to distinguish causative from non-causative SNPs (paper 3).In paper 1 single and multi QTL fine-mapping methods were compared in a situation where two QTL were located in the analysed region. The single QTL method had problems differentiating between two QTLs when these were closely located, which often resulted in discovery of a ghost QTL between the real ones, or no clear QTL discovery. The multi QTL approach found evidence of both QTLs even when these were close (15cM). Although these differences to some extent may be explained by the different statistical approaches used by the two methods, the main conclusion from this paper is that multi QTL mapping methods should be applied when analysing QTL data. Paper 2 investigated the effect of including the causative SNP amongst the markers in a QTL mapping experiment. Both power and precision was greatly increased by including the causative mutation. When the causative mutation was not included amongst the markers the LLD method had clearly better precision and power than the association method. The increased power from including the causative SNP as marker was larger with association mapping than LLD mapping, and when the causation was included amongst the markers the methods had similar power and precision. These differences were partly due to the test-statistics, as the association method tested directly on the markers, while the LLD method tested the midpoints of the marker brackets. Including the causative mutation as marker increases the possibility of discovering QTLs of smaller effects.The increased power and precision obtained by including the causative SNP amongst the markers, was in paper 3 used to develop a test to confirm causative SNPs. The ‘Causative SNP Test" obtained a power of 28 % in this study, while the power of QTL detection was 97 %. The low power of CST was due to strong LD between the analyzed markers. All confirmed SNPs were truly causative and correctly positioned by the CST test. Thus, if positive, this test provides a lot of evidence for causality.Results from QTL mapping experiments so far indicates that most complex traits are controlled by many genes, with mainly small effects on variance. Currently available genome sequences and sample sizes has limited power to detect QTLs with small effects and thus, reported QTLs so far only explains small proportions of observed phenotypic variance for most traits. Future prospects of complete genome sequences will increase the power to find QTLs. The recent strong focus on genome-wide association studies (GWAS) will be expected also for future experiments. This study has shown that future QTL mapping experiments should use multi QTL approaches, to avoid bias from additional QTLs. As the power of QTL mapping is greatly increased by including the causative mutation amongst the markers, one should also aim to design experiments that have high power to distinguish causative from non-causative mutations. Experiments where the relationship between the individuals is low, as is generally the case in human GWAS studies, seem to achieve this. The causality can in the next step be tested by the proposed CST test.
Forfattere
Anne-Grete Roer HjelkremSammendrag
Computer models are built to simulate real world systems. It is well known that models are related with uncertainty, still uncertainties are rarely quantified. The Bayesian statistical approach is used to calibrate a complex deterministic dynamic model of snow depth. Challenges emerging when applying the method will be explored. The Bayesian approach regards parameters as random and allows integration of prior knowledge. It will be demonstrated how prior information and new data affect the calibration process, parameters and model outputs, with focus on uncertainty. Point estimates and uncertainties are calculated and visualized for both parameters and model outputs. Generally, uncertainty decreased when new data were incorporated. Uniformly distributed priors gave the best fit for this model according to root mean square error, while the more informative beta distributed priors gave more physically meaningful parameter estimates. Markov chains of samples from the posterior distribution of the parameters were obtained by the random walk Metropolis algorithm. Crucial points when using these methods are reaching and determining convergence of the chains. In order to reach convergence faster, informative priors, Sivia"s likelihood, reflection and updating the proposal distribution with parts of the data gave successful results. To determine convergence objectively and correctly, the use of multiple chains and the Gelman Rubin method was found useful. Several decisions must be made when implementing Bayesian calibration and the choices that were found to be most effective will be highlighted and visualized.
Forfattere
Jan-Ole Skage Åge ØstgårdSammendrag
Sørlandet og Vestlandet har meget gode forhold for dyrking av juletrær, spesielt gjelder dette for edelgranarter. I Agder, Dalane og Ryfylke er klimaet spesielt godt egnet for produksjon av juletrær. Det er her gode arealer som er velegnet for planting. Disse arealene utgjør et stort potensial for juletreproduksjon på Sørlandet og Sørvestlandet. For øyeblikket opplever danske juletredyrkere at etterspørselen er større enn tilbudet. De klarer ikke å dyrke tilstrekkelig antall juletrær til det europeiske grossistmarkedet, og det er her vi kan ha en god mulighet til å komme sterkere inn på eksportmarkedet. Artikkelen omtaler provenienser i fjelledelgran med raskt og høyt juletreutbytte fra ett forsøk på skogsmark ved Moi i Dalane. Proveniensen Inzana Lake fra British Columbia i Canada og flere andre provenienser kan med godt hell dyrkes i deler av Agder og Rogaland med godt lokalklima som er lite utsatt for vårfrost.