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
Forfattere
Daniel Rasse Marie-france Dignac Haithem Bahri Cornelia Rumpel André Mariotti Claire ChenuSammendrag
Lignin has long been suspected a major source of stable carbon in soils notably because of the recalcitrant nature of its polyphenolic structure relative to other families of plant molecules. However, lignin turnover studies have produced conflicting results, most of them suggesting that large proportions of plant-residue lignin decompose within a year of incorporation into soils. Here, we propose a two-reservoir model where lignin in undecomposed plant residue (Lp) can either reach soil fractions where it is somewhat protected from further decomposition (Ls) or is transformed to non-lignin products. Model calibration data were obtained through compound-specific 13C isotopic analyses conducted in a zero- to nine-year chronosequence of maize monoculture after wheat in a temperate loam soil of the Paris basin. Lignin was quantified by CuO oxidation as VSC-lignin, i.e., the sum of vanillil- (V), syringyl- (S) and coumaryl-type (C) phenols. Model calibrations indicate that Lp has a turnover rate faster than one year and that 92% is mineralized as CO2 or transformed into other non-lignin products, while only 8% reaches the Ls fraction. Estimated turnover rate of the Ls fraction was 0.05 yr-1. The model also suggested that about half of Lp was not measured because it had been excluded from the samples in the process of sieving at 5 mm. In conclusion, the model indicates that chemical recalcitrance alone is not sufficient to explain VSC-lignin turnover in soils, and that, functionally, the most relevant mechanism appears to be the transfer of VSC-lignin molecules and fragments from decomposing plant tissues to soil-protected fractions.
Forfattere
Ricardo Holgado Stig Andersson Christer MagnussonSammendrag
Cereal cyst nematodes, Heterodera spp., are known worldwide as parasites of cereals and grasses. Surveys of cereal fields in Norway have revealed that nematodes belonging to the H. avenae complex occur throughout the country, and that H. avenae (the oat cyst nematode) is the most common species, followed by H. filipjevi (the rye cyst nematode). Both species are of economic importance in Scandinavia. H. avenae has been found in two common pathotypes, Ha 11 and Ha 12. Work in Sweden, however, has detected three additional pathotypes, H. avenae "Knislinge", H. avenae "Ringsåsen" and H. avenae "Våxtorp". These pathotypes were found also in the Norwegian surveys. In Sweden H. filipjevi has two pathotypes, "East" and "West". In Norway, only pathotype "West" has been detected so far. Nematode management practices must be based on the knowledge of the relationship between initial nematode density and yield, the population dynamics, and the measures capable of reducing or keeping the population density below the threshold for economic damage. Crop rotation and the use of cultivars with resistance are important measures for controlling cereal cyst nematodes. Several cereal cultivars with resistance to H. avenae are on the market. As to H. filipjevi, resistance may be found in some commercial cultivars, although no intentional breeding for resistance against this nematode species has been attempted. In 2004 and 2005 the majority of the cereal cultivars on the Norwegian market were tested for susceptibility/resistance towards H. avenae pathotype Ha 11, H. avenae pathotype "Våxtorp" and H. filipjevi pathotype "West". Management systems, based on careful nematode identification and good knowledge of appropriate resistant cultivars, are in operation in Norway. Resistant barley is generally recommended when nematode populations are high due to its high tolerance compared to resistant oats. Farmers implementing this program have reported increased cereal yields on the average of 1000 kg /ha. It has been calculated that by implementing this program in full the county of Vestfold could make an economic gain of 800 000 " annually.
Forfattere
Ingvild Wartiainen Anne Grethe Hestnes Ian R. McDonald Mette M. SvenningSammendrag
A Gram-negative, rod-shaped, non-motile, non-spore-forming, pink-pigmented bacterium, SV97T, was isolated from a wetland soil near Ny-Ålesund, Svalbard Islands, Norway (78° N). On the basis of 16S rRNA gene sequence similarity, strain SV97T was shown to belong to the Alphaproteobacteria and was highly related to a number of non-characterized Methylocystis strains with GenBank accession nos AJ458507 and AJ458502 (100 %) and AF177299, AJ458510, AJ458467, AJ458471, AJ431384, AJ458475, AJ458484, AJ458501 and AJ458466 (99 %). The most closely related type strains were Methylocystis parvus OBBPT (97.2 %) and Methylocystis echinoides IMET 10491T (97 %). The closest related recognized species within the genus Methylosinus was Methylosinus sporium NCIMB 11126T (96.0 % similarity). Chemotaxonomic and phenotypic data (C18 : 1w8 as the major fatty acid, non-motile, no rosette formation) supported the af"liation of strain SV97T to the genus Methylocystis. The results of DNA"DNA hybridization and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain SV97T from the two recognized Methylocystis species. Strain SV97T therefore represents a novel species, for which the name Methylocystis rosea sp. nov. is proposed, with the type strain SV97T (=DSM 17261T =ATCC BAA-1196T).
Forfattere
Anne Kari Bergjord Arne Oddvar Skjelvåg Helge BonesmoSammendrag
God overvintring er avgjørende for å lykkes med dyrking av høsthvete (Triticum aestivum L.). Beregninger av risiko for høsthvete-produksjon i et endret klima eller på nye lokaliteter fordrer utvikling av verktøy som overvintringsmodeller, modeller som kan kvantifisere forhold mellom klimatiske faktorer og plantenes evne til å overleve vinteren. Ett slikt forhold er plantenes frosttoleranse, påvirket av fenologisk utvikling. Det er imidlertid utviklet veldig få modeller som simulerer frosttoleranse og overvintring. Som en del av forskningsprogrammet WINSUR ble feltforsøk utført gjennom to vintre på tre lokaliteter rundt 63°N 11°E; Stjørdal, Selbu, og Oppdal med beliggenhet på henholdsvis 26, 165, and 590 m o.h. Plantene ble sådd i kasser og herdet under naturlige forhold i Stjørdal før de i november ble fordelt til de tre lokalitetene. Planter ble hentet inn fra feltene en gang i måneden fra november til april og testet for frost toleranse (LT50). Funksjoner fra en canadisk overvintrings-modell ble kalibrert til forholdene mellom daglige værobservasjoner fra feltene og månedlige bestemmelser av LT50. Modellen simulerer plantenes aktuelle LT50-verdier fra såing, gjennom vinteren, og fram tll våren. Frosttoleransen øker ved herding og tapes ved avherding og stress. Den originale stress-funksjonen for lave temperaturer hentet fra den canadiske modellen ble utvidet med en stress-funksjon basert på varighet av snødekke på jord uten tele. På grunn av at vernaliserings-prosessen påvirker LT50 estimeres også den daglig til vernaliseringen er fullført. Nødvendige data for å kjøre modellen er maksimum LT50 for den aktuelle kornsorten og daglige målinger av snødekke og temperatur i 2 cm jorddybde (kronetemperatur).
Forfattere
Ingrid HoltsmarkSammendrag
Lys ringråte på potet er forårsaket av den Gram-positive bakterien Clavibacter michiganensis subsp. sepedonicus (Cms). Lys ringråte er en utbredt plantesykdom, som forårsaker store økonomiske tap. En strategi som kan gi kontroll over sykdommen er utvikling av midler som spesifikt hemmer vekst av patogenet. I dette arbeidet har smalspektrede antimikrobielle stoffer som utskilles av den tomatpatogene slektningen, Clavibacter michiganensis subsp. michiganensis (Cmm), blitt renset og studert. Disse antimikrobielle stoffene hemmer vekst av Cms, og kan vise seg nyttige som midler i kampen mot ringråtepatogenet. De antimikrobielle stoffene omfatter et bakteriosin på 14 kDa, et lantibiotikum på 2145 Da og en rekke antibiotika med molekylmasser rundt 800-900 Da, som ser ut til å tilhøre tunicamycinfamilien. Det lantibiotiske peptidet, michiganin A, likner på actagardine, som er et type-B lantibiotikum produsert av actinomyceten Actinoplanes liguriae. Begge disse peptidene har likheter med mersacidin, som er et velkjent type-B lantibiotikum. Disse likhetene omfatter blant annet en konservert aminosyre som man tror er viktig for mersacidins antimikrobielle aktivitet. Det å oppnå større forståelse av mekanismene som styrer patogeniteten til Cms, er en vei mot bekjempelse av sykdommen. I tråd med dette ble det utført ekspresjonsanalyse av ni mulige virulensgener. Fem av de utvalgte genene er homologer av pat-1, et gen som antas å kode for en serin-protease som spiller en rolle i patogenitet hos Cmm, og gener som koder for celleveggnedbrytende enzymer (to cellulaser, en xylanase og en pektat-lyase). Genuttrykk ble målt med bruk av Real-Time PCR amplifisering av revers-transkribert RNA, fra celler fra kultur og fra infisert bladmateriale av potet. Genene som koder for de to cellulasene, xylanasen og to av Pat-1-homologene ble klart oppregulert under infeksjon. Uttrykket av pektat-lyasen ble kun svakt påvirket av infeksjon, mens de tre andre homologene av Pat-1 ble nedregulert. Den overbevisende oppreguleringen av de to cellulasene, xylanasen og to av homologene av Pat-1 under infeksjon, tyder på at disse proteinene er involvert i patogenitet, og avdekker dermed mål for videre studier av Cms.
Sammendrag
Monilinia laxa, M. fructigena and M. fructicola cause brown rot of stone and pome fruits, which result in considerable economic losses. M. fructigena causes fruit decay in both pome and stone fruit, while M. laxa causes blossom wilt, twig blight, canker and fruit rot on stone fruit. A special form of the fungus, M. laxa f.sp. mali, is found only in apple, where it causes blossom wilt, spur-kill and canker. M. fructicola is a quarantine pathogen in the EU, and it is thus of important to have reliable identification methods and to monitor the population of these fruit pathogens. More than 90 isolates of Monilinia spp. from the main fruit producing districts in Norway was collected. The isolates originated from cherry, plum, apple, apricot and peach. They were identified by growth characteristics in culture according to EPPO standards (EPPO Bull 33: 245-47) and by a multiplex PCR method (Côté (2004) Plant Disease 88:1219-1225). Thus far, the quarantine organism M. fructicola has not been detected in Norway. M. laxa and M. fructigena were isolated from plum, apricot, cherry and apple, however in apple M. fructigena was isolated only from fruits and M. laxa only from infected fruit spurs (generative shoots). In peach only M. laxa was detected. Genetic variation among the isolates is currently being examined using AFLP.
Sammendrag
Tributyltinn (TBT), som i hovedsak benyttes som begroingshindrende middel på skip, er et miljøgiftproblem i mange marine områder. På grunn av høye konsentrasjoner av tinnorganiske forbindelser som opptrer i sediment i mange områder av norskekysten (særlig i havner) og de lave effektgrensene som er dokumentert, er det viktig å få avklart i hvilken grad tinnorganiske forbindelser i sediment utgjør et miljøproblem. Det nasjonale råd for forurensede sedimenter har påpekt at nedbrytning og tilgjengelighet av TBT i sediment representerer temaer der en i dag har for lite kunnskap til å kunne foreta en kostnadseffektiv og bærekraftig opprydding . I denne rapporten beskrives resultater fra nedbrytningsforsøk der en har hatt som hovedmål å bestemme hvordan ulike miljøfaktorer påvirker nedbrytningen av TBT i sedimenter. Rapporten redegjør også for biotilgjengelighetstester som har hatt som mål å avklare i hvilken grad tinnorganiske forbindelser i sediment og fòr (foring med forurenset blåskjellinnmat) er tilgjengelig for sedimentlevende organismer som spises av fisk (dvs. børstemarken Hediste (Nereis) diversicolor). I rapporten redegjøres det også for utforskende undersøkelser som er gjennomført med tanke på å komme frem til metoder (endepunkt) som kan brukes til å vurdere giftighet av TBT-forurensede sedimenter. Disse utforskende undersøkelsene er gjennomført ved måling av noen utvalgte parametere (dødelighet, nedgraving, fødeinntak og glutation reduktase aktivitet) i børstemark. En har også undersøkt i hvilken grad tinnorganiske forbindelser i sediment fører til utvikling av hannlig kjønnskarakter (imposex) og effekter på cellenivå (membranstabilitet, mitokondriell aktivitet hos hemocytter) hos hunner av nettsnegl (Hinia reticulata = Nassarius reticulatus).
Sammendrag
Cavity spot (Pythium spp.), liquorice rot (Mycocentrospora acerina) and crater rot (Fibularhizoctonia carotae) are important carrot diseases. Cavity spot develops during the growing season, while the latter two are post harvest diseases. Five Pythium "species" were identified as agents of cavity spot in Norway; P. intermedium, P. sulcatum, P. sylvaticum, P. violae and P. "vipa" (probably a new species). Based on unique sequence regions in the ITS, PCR primers were designed to identify the five Pythium "species" and the two post harvest pathogens. PCR detection was species-specific with no cross-reaction to other Pythium species or to other fungal isolates from carrots. At different points in the growing season, soil and carrots were sampled from farm fields in Norway. PCR assays allowed detection of pathogens in both soil and carrot tissue. PCR results from samples of soil adhering to roots late in the growing season corresponded well with the incidence of cavity spot and liquorice rot on carrots after 6 months storage. PCR assay data from soil samples taken within 14 days after sowing carrots also predicted cavity spot incidence reasonably well. There was little incidence of crater rot during the experimental period, which did not allow proper evaluation of the test for F. carotae. Commercial testing of carrot soils is now available through the company "Carrotech" and work is in progress to implement quantitative PCR.
Sammendrag
The performances of the plum rootstocks Ferlenain, Ishtara, Jaspi and P 8-13 compared with St. Julien A as a standard, for the cultivars `Opal" and `Reine Claude GF 1119" were assessed in a field trial in western Norway at 60° North. This trial was one part of an international plum rootstock trial located in seven European countries and organized from INRA Bordeaux. Trees were planted in spring 1994; spaced 2.0 x 4.0 m and formed with a central leader as free spindles. Soil management was grass in the alleyways and herbicide strips 1-m wide along the tree rows. Tree vigour, yield, fruit size and yield efficiency were evaluated for the seven subsequent years. Tree size was significantly affected by the rootstocks. P 8-13 produced the largest trees for both cultivars as measured by trunk cross-sectional area. The smallest trees were produced on Ferlenain for the cultivar `Opal" and on Jaspi for `Reine Claude". The cultivar `Opal" was the most productive and gave three times larger crop than "Reine Claude" on average for the six cropping years. The `Reine Claude" trees came two years later into production than `Opal". There were small differences between the different rootstocks in productivity: However, the rootstock Ferlenain produced significant lower crop than the other rootstock for `Opal". Trees on Jaspi were the most yield efficient for `Opal" and Ferlenain for `Reine Claude". The fruit sizes were in general medium to small for both cultivars and became little affected by the different rootstocks. The average fruit size was about 30 g for `Opal" and 25 g for `Reine Claude". Fruit quality characterized by the content of soluble solids was high for `Reine Claude" with average 20 % and 15 % for `Opal" and did not differ much between trees on the various rootstocks.
Forfattere
Marie Bengtsson Gunnhild Jåstad Geir Kjølberg Knudsen Sverre Kobro Anna-Carin Bäckman Peter WitzgallSammendrag
Plant volatiles mediate host finding in insect herbivores and lead to host fidelity and habitat-specific mating, generating premating reproductive isolation and facilitating sympatric divergence. The apple fruit moth, Argyresthia conjugella Zeller (Lepidoptera: Argyresthiidae), is a particularly suitable species to study the cues and behavioural mechanisms leading to colonization of a new host: it recurrently oviposits on the non-host plant, apple Malus domestica Borkh. (Rosaceae), where the larvae cannot complete their development. The larval host of the apple fruit moth (Lepidoptera, Argyresthiidae), is rowan Sorbus aucuparia L. (Rosaceae). Fruit setting in rowan, however, fluctuates strongly over large areas in Scandinavia. Every 2"4 years, when too few rowanberries are available for egg laying in forests, apple fruit moth females oviposit instead on apple in nearby orchards, but not on other fruits, such as pear or plum. This poses the question of which cues mediate attraction to rowan and apple, and how apple fruit moth discriminates rowan from apple. Chemical analysis and antennal recordings showed that 11 out of 15 rowan volatiles eliciting an antennal response in A. conjugella females co-occur in rowan and apple headspace, in a different proportion. In the field, A. conjugella was attracted to several of these plant volatiles, especially to 2-phenyl ethanol, methyl salicylate, and decanal. Addition of anethole to 2-phenyl ethanol had a strong synergistic effect, the 1 : 1 blend is a powerful attractant for A. conjugella males and females. These results confirm that volatiles common to both plants may account for a host switch in A. conjugella from rowan to apple. Some of the most attractive compounds, including 2-phenyl ethanol, anethole, and decanal, which have been found in several apple cultivars, were not present in the headspace of the apple cultivar, Aroma, which is also susceptible to attack by A. conjugella . This supports the idea that the odour signal from apple is suboptimal for attraction of A. conjugella , but is nonetheless sufficient for attraction, during times when rowan is not available for egg laying.