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
Mats Høglind Ann NorderhaugSammendrag
I denne rapporten prøver vi å belyse hvilke økologiske konsekvenser klimaendringene kan få for stølslandskapet i Valdres og det biologiske mangfoldet som er knyttet til de gamle slåtte- og beitemarkene der. Som utgangspunkt brukes nedskalerte scenarioer for daglig temperatur og nedbør som er tilgjengelig for nedlasting fra internett, samt kunnskap og modeller som er utviklet i Bioforsks strategiske instituttprogram WINSUR (2004-2008) om klimaeffekter på dyrket eng. Klimascenarioene viser at det vil bli store klimaforandringer både på "gårdsnivå" og i stølslandskapet i Valdres. Beregninger er gjort for en gård på 525 m høyde og en støl på 890 m høyde. Vekstsesongen vil bli lengre og klimaindeksberegninger for vinterstressfaktorer for flerårige fôrvekster i fulldyrka eng indikerer at overvintringen vil bli minst like god som i dag. Produksjonen vil derved øke både på gårds- og seternivå og man vil kunne øke antallet slåtter til tre. Beregningene, som er gjort for dyrka eng, kan delvis overføres til semi-naturlig beiteog slåttemark (naturbeite og natureng), men fordi de er ugjødsla vil produksjonsøkningen ofte bli mindre og økningen blir i stor grad påvirket av endringer i næringsforsyningen som følge av klimaendringene. Disse endringene vil variere fra sted til sted og er vanskelige å beregne uten omfattende studier. Vår kunnskap om hvilke effekter klimaforandringene vil få for de semi naturlige grasmarkene er fortsatt begrenset, men vi vet at konkurransen mellom artene vil forandres. Det er likevel stor sannsynlighet for at disse grasmarkene kan bevares der de finnes i dag og kanskje også spre seg oppover, hvis beiteog slåttedriften opprettholdes og justeres i forhold til klimaendringene. Tørrere somre vil kunne gi en negativ effekt på den seminaturlige engvegetasjonen, i hvert fall på tørkesvak jord, noe som ytterligere kan forsterkes av for sterkt beitetrykk. Det vil derfor bli ekstra viktig å opprettholde et "optimalt" beitetrykk. De semi naturlige grasmarkene i seterlandskapet representerer en stor beiteressurs og en "in situ"-bevaring av arter og genressurser som kan få stor betydning i en verden der matproduksjonen på forskjellig måte trues av klimaendringene. Menneskelig aktivitet kan både forsterke og motvirke effektene av klimaendringene på de semi-naturlige slåtte- og beitemarkene. Stølslandskapet truesi dag av gjengroing på grunn av mindre eller opphør av stølsdrift og denne trusselen vil forsterkes av klimaforandringene. Også oppdyrking vil utgjøre en økende trussel for det biologiske mangfoldet som er knyttet til disse grasmarkene når klimaet forandres, men en gjennomtenkt forvaltning av viktige stølsområder basert på tradisjonelle driftsformer, vil kunne motvirke en negativ utvikling.
Forfattere
Ricardo Holgado Anette Stryken Christer Magnusson Irene Rasmussen Kari-Ann Strandenæs Bonsak HammeraasSammendrag
A survey was undertaken to investigate the occurrence of plant parasitic nematodes in the municipality of Lier located in southern Norway. A wide variety of vegetables crops are grown in this area. Soils in Lier are mostly sandy loam, and irrigation is practiced when necessary during the growing season. There is little information on the occurrence on plant parasitic nematodes in vegetables; particularly in areas where farmers have specialized in intensive production, and often grow two to three cultures of vegetables during the growing season. In the year prior to this investigation several crops had been observed with symptoms of attack by plant parasitic nematodes. The aim of this survey was to identify the species responsible for the damage. The emphasis was placed on genera of known economic importance. During the end of the growing season plants showing poor growth or symptoms of nematode damage and plants with healthy appearance were sampled. A total of 74 root samples were collected and assessed for galls and 37 soil samples were collected from the rhizospheres. In the study samples were collected from 7 producers. Five samples were taken from cauliflower (Brassica oleraceae var. botrytis), 4 from broccoli (Brassica oleraceae var. italica), 8 from pak-choy Chinese cabbage (Brassica rapa ssp. pekinensis), 8 from lettuce (Lactuca sativa) and 1 from celery (Apium graveolens). Soil sampling included 11 samples from areas with fallow, ploughed and rotocultivated land. Root knot nematodes were not recorded in the root samples. In soil samples economically important nematode genera were recorded. Tylenchorhynchus sp. (72.9 % of samples), was the most frequently encountered genus, followed by the species Heterodera cruciferae and other Heterodera spp. (67.5 %), Pratylenchus spp. (54 %), Paratylenchus spp. (29,7 %), and Helicotylenchus spp. (8.1 %). In addition to cyst detections Heterodera juveniles were found in 32.4 % of samples. In all the samples from Pak-choy Chinese cabbage (Brassica rapa ssp. pekinensis) Heterodera cruciferae was recorded, symptoms of nematode damage was also observed in the field. The results of the survey will help in planning future research as well as in developing effective nematode management strategies suitable for vegetable producer particularly in this area. The authors are thankful to the FMLA in Buskerud County for economical support.
Forfattere
Ricardo Holgado Anette Stryken Christer Magnusson Irene Rasmussen Kari-Ann Strandenæs Bonsak HammeraasSammendrag
A survey was undertaken to investigate the occurrence of plant parasitic nematodes in the municipality of Lier located in southern Norway. A wide variety of vegetables crops are grown in this area. Soils in Lier are mostly sandy loam, and irrigation is practiced when necessary during the growing season. There is little information on the occurrence on plant parasitic nematodes in vegetables; particularly in areas where farmers have specialized in intensive production, and often grow two to three cultures of vegetables during the growing season. In the year prior to this investigation several crops had been observed with symptoms of attack by plant parasitic nematodes. The aim of this survey was to identify the species responsible for the damage. The emphasis was placed on genera of known economic importance. During the end of the growing season plants showing poor growth or symptoms of nematode damage and plants with healthy appearance were sampled. A total of 74 root samples were collected and assessed for galls and 37 soil samples were collected from the rhizospheres. In the study samples were collected from 7 producers. Five samples were taken from cauliflower (Brassica oleraceae var. botrytis), 4 from broccoli (Brassica oleraceae var. italica), 8 from pak-choy Chinese cabbage (Brassica rapa ssp. pekinensis), 8 from lettuce (Lactuca sativa) and 1 from celery (Apium graveolens). Soil sampling included 11 samples from areas with fallow, ploughed and rotocultivated land. Root knot nematodes were not recorded in the root samples. In soil samples economically important nematode genera were recorded. Tylenchorhynchus sp. (72.9 % of samples), was the most frequently encountered genus, followed by the species Heterodera cruciferae and other Heterodera spp. (67.5 %), Pratylenchus spp. (54 %), Paratylenchus spp. (29,7 %), and Helicotylenchus spp. (8.1 %). In addition to cyst detections Heterodera juveniles were found in 32.4 % of samples. In all the samples from Pak-choy Chinese cabbage (Brassica rapa ssp. pekinensis) Heterodera cruciferae was recorded, symptoms of nematode damage was also observed in the field. The results of the survey will help in planning future research as well as in developing effective nematode management strategies suitable for vegetable producer particularly in this area. The authors are thankful to the FMLA in Buskerud County for economical support.
Forfattere
jihong liu clarke Carl Jonas Jorge Spetz Sissel Haugslien Dag-Ragnar Blystad Merete Wiken Dees Shaochen Xing Roar MoeSammendrag
Abstract Poinsettia (Euphorbia pulcherrima Willd. Ex Klotzsch), is a contemporary symbol of Christmas in most parts of the world. Today, Europe and North America represent the largest volume of production and sales, but demand is growing quickly in the other regions as poinsettia becomes more popular each year. In Norway, poinsettia is one of the most important pot plants, with a yearly production close to 6 million plants. Its ornamental value and innovation potential have laid the foundation for extensive research in Norway and elsewhere. Poinsettia mosaic virus (PnMV) can cause diseases in modern poinsettia cultivars. PnMV is a single-stranded, positive-sense RNA virus that belongs to the family Tymoviridae. Infection of poinsettia plants with PnMV results in mosaic symptoms during parts of the growing season, which in turn decreases the commercial value of this ornamental plant. Thus, growers are interested in the potential benefits of growing PnMV-free poinsettias. PnMV-free poinsettia plants can be obtained by heat treatment or in vitro culture of apical meristems, which are time-consuming and cost-ineffective methods. There is a need for a new and effective alternative approach, like Agrobacterium-mediated transformation, which can overcome these difficulties. Therefore, we have developed an Agrobacterium-mediated transformation approach for poinsettia for the first time. Internode stem explants of poinsettia cv. Millenium were transformed by Agrobacterium tumefaciens, strain LBA 4404, harbouring three hairpin (hp) RNA gene constructs to induce RNA silencing-mediated resistance to Poinsettia mosaic virus (PnMV). Prior to transformation, an efficient somatic embryogenesis system was developed for poinsettia cv. Millenium in which about 75 % of the explants produced somatic embryos. In five experiments utilizing 868 explants, 18 independent transgenic lines were generated. Stable integration of transgenes into the poinsettia nuclear genome was confirmed by PCR and Southern blot analysis. Both single- and multiple-copy transgene integration into the poinsettia genome were detected among transformants. Northern blot analysis confirmed the production of transgene-derived small interfering RNAs (siRNAs). Transgenic lines showing resistance to mechanical inoculation of PnMV were detected by double antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISA). The Agrobacterium-mediated transformation methodology developed in the current study should facilitate improvement of this ornamental plant with enhanced disease resistance, quality improvement and desirable colour alteration. Because poinsettia is a non-food, non-feed plant and is not propagated through sexual reproduction, this is likely to be more acceptable even in areas where genetically modified crops are currently not cultivated.
Forfattere
Alemayehu Chala May Bente Brurberg Anne Marte TronsmoSammendrag
Sorghum anthracnose caused by Colletotrichum sublineolum is one of the most destructive diseases of sorghum around the world. Owing to the production of sorghum in a wide range of agro-ecological zones with different farming systems since earlier times, diverse sorghum land races exist in Ethiopia that may be creating favorable conditions for the presence of diverse pathogen races. It is for the time being not possible to exploit the variations in the landraces to develop sustainable and affordable disease management strategies because information on the genetic diversity of both the plant and the pathogen are little or lacking in Ethiopian condition. Therefore the current project was developed with the objectives of studying the reaction of Ethiopian adapted sorghum germplasm to anthracnose infection and investigating the morphological and genetic variations among isolates of C. sublineolum from Ethiopia. Two separate experiments are being conducted to achieve these objectives. The first experiment deals with field screening of sorghum germplasm for resistance to anthracnose. More than 100 sorghum lines were screened in 2006 and 2007 cropping seasons at Alaba and Wolayta, Southern Ethiopia. Anthracnose severity at 140 days post planting, measured as the proportion of leaves covered by the disease, ranged from 11% to more than 50% over the 2 years. Results of this experiment revealed the existence of variations in the reaction of the tested lines to natural infection by anthracnose. Some of the lines appeared to possess a good level of stable resistance while others show differential reactions across experimental locations and years. This suggests not only the potential of Ethiopian adapted sorghum germplasm in serving as sources of resistance to anthracnose but also the impact environmental conditions may have on the genotype response to the disease. Furthermore this may suggest the presence of different pathogen pathotypes in the two experimental sites. The second experiment is aimed at investigating the morphological, pathogenic and genetic variations among C. sublineolum isolates from Ethiopia. To achieve this objective more than 90 leaf samples were collected from different parts of Ethiopia and brought to Norway for laboratory analysis. Single spore isolates are being grown on culture media and the genetic variations among the isolates will be analyzed using AFLP. Besides, the isolates will be characterized morphologically. In addition, selected isolates representing different genetic and morphological groups will be inoculated to sets of differential cultivars obtained from Texas, USA in a green house. The experiment will be arranged in CRD (completely randomized design) with 3 replications, and data will be recorded on the presence or absence of anthracnose and severity of the disease will be measured at a week interval to determine the pathogenecity and aggressiveness of the isolates.
Sammendrag
Commercial strawberry production in Scandinavia started as early as the 1920s, with the cultivar `Abundance". Although the production area was about 1500 ha, the yield was very low (< 3 t ha-1). In the 1960s Scandinavia had a large increase in strawberry area and yield per hectare. The strong development of strawberry production came after the introduction of the cultivar `Senga Sengana", new growing techniques (black polyethylene mulch) and the release of new and more efficient fungi- and herbicides. Over the past 30 years, the yield and growing area has stabilized, although the number of strawberry growers has decreased strongly. Today, Scandinavia has a strawberry production of about 8500 ha, yielding about 75 000 tons of berries in a very short summer-season. Almost all strawberry growing is perennial production with single-cropping (SD) cultivars in open field, and the fields are normally kept for 3-5 years. The main strawberry cultivars grown today are `Korona", `Polka", `Honeoye", `Jonsok" and `Florence". The area of `Sonata" is increasing. While almost all strawberries up to the 1970s were picked and sold through a "pick-your-own" system, today, almost 95% is sold through wholesale dealers for fresh consumption, and only a small amount is frozen for processing. Since the mid 1990s, there has been a slow decrease in the strawberry production area in Scandinavia. This is due to an over-production of strawberries in a short, hectic season, giving very low prices. To avoid this, attempts are being made to extend the season, especially with row cover, plastic tunnels, stored plants and new cultivars (including everbearing cvs.). The growing area covered with polyethylene tunnels are now increasing in all the Scandinavian countries. The area of raspberry in Scandinavia was stable up to the 1990s, with a production of about 500 ha. The production was mainly for the processing industry with old Norwegian and Finnish cultivars. Since 1995, the raspberry area has doubled, and is still increasing. This came after introduction of the Scottish cultivar `Glen Ample", which has shifted the production from mainly for the processing industry, over to mainly for fresh consumption. This development was started in Norway, and the other Scandinavian countries are following up. Introduction of `Glen Ample" has given the growers new possibilities to increase their income, and the focus on extending the season and on berry quality, have increased. About half of the Norwegian raspberry production is now under polyethylene tunnels, and this leads again to new possibilities of extension of the season by growing long canes or primocane-fruiting varieties like `Polka". Less than 120 ha of blueberries are produced in Scandinavia. The yields are low, and the picking cost too high. But, there is increasing interest, related to health benefits, from the marked. The main challenges for berry production in Scandinavia are access to and cost of labour, and how to meet the increased competition from imported berries. The Scandinavian countries have also strong restrictions in the number, and use of pesticides. Increased focus on taste and quality will be important in the future.
Forfattere
Gunn Mari StrømengSammendrag
Gråskimmel er en soppsjukdom som forårsakes av plantepatogenet Botrytis cinerea Pers. ex Fr. Denne skadegjøreren fører til store avlingstap i jordbær (Fragaria x ananassa), og det brukes mye kjemiske plantevernmidler for å bekjempe den. Dette arbeidet har i hovedsak omfattet undersøkelser knyttet til to alternative bekjempelsesstrategier; reduksjon av smittepresset i jordbærfelt om høsten og om våren før blomstring, og biologisk bekjempelse i blomstringen med bruk av nyttesopp (antagonistisk sopp). Den viktigste kilden til danning av konidier om våren var dødt og visnende plantemateriale av jordbær. Overvintrede sklerotier var i gjennomsnitt like viktige for produksjon av konidier som overvintret mycel i plantemateriale, men det var en sterk tendens til at enten sklerotier eller mycel sto for størstedelen av konidieproduksjonen innen et felt og år. Smitte i halm, ugras og jord var av liten betydning for konidiedanning om våren. Feltforsøk ble gjennomført i jordbærfelt i forskjellige fylker i Sør-Norge med sprøyting av fungicider og antagonistene Trichoderma og Clonostachys om høsten og om våren før blomstring. Behandlingene ga i de fleste tilfeller ingen effekt på gråskimmelangrep, men i ett tilfelle var det mindre gråskimmel når det ble sprøytet med fenheksamid høst og vår. Sprøyting med sporesuspensjoner av kommersielle preparater av Trichoderma eller uformulerte antagonister (Trichoderma og Clonostachys) i blomstringen, eller tilførsel av Trichoderma-sporer til jordbærblomstene ved hjelp av pollinerende insekter ga ingen reduksjon av gråskimmel i feltforsøk. Vi undersøkte ulike metoder for deteksjon av latente B. cinerea-infeksjoner i jordbærblomster for å se om dette kunne brukes til å teste potensielle antagonisters evne til å hemme blomsterinfeksjoner. Kvantitativ real-time PCR var den mest sensitive av metodene vi testet, og detekterte B. cinerea DNA 24 timer etter inokulering. Innvirkningen av ulike fuktighetsforhold gjennom blomstring og høsting på blomsterinfeksjon og symptomutvikling ble undersøkt. Kontinuerlig fuktige bladoverflater og høy relativ luftfuktighet (RH) resulterte i et betydelig avlingstap fordi B. cinerea forårsaket visning av blomster. Jordbærblomster som ble gitt ulike kombinasjoner av perioder med høy og lav RH etter inokulering utviklet begernekroser etter 96 timer ved høy RH, uavhengig av om det var kontinuerlig høy RH, eller avbrudd med tørre perioder etter 24 til 72 timer. Resultatene indikerer at fuktighetsforhold etter blomsterinfeksjon er avgjørende for når i bærutviklingen symptomene kommer til syne.
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
Sonja KlemsdalSammendrag
The detection and quantification of plant pathogens in soil can be used to predict the risk to develop disease in the crop. Knowledge of the presence of such pathogens can also be used to plan control strategies for plant disease. The detection of carrot pathogens will be used as and illustrating example. Quality of carrots is influenced by several pathogens. In Norway the carrots are usually harvested in October, and while some carrots are used for immediate consumption, most carrots are stored shorter or longer periods in cold storage. During this storage there may be up to 70% loss due to carrot-rot caused by fungal diseases. The most important of these diseases are liquorice rot caused by the fungus Mycocentrospora acerina and crater rot caused by Fibularhizoctonia carotae. A standard PCR-based assay has been developed that enables us to detect the pathogens in the soil attached to the carrots at harvest. The results from this assay can be used to decide whether the harvested carrots can be stored or rather should be consumed immediately. Another disease, cavity spot, is worldwide considered to be one of the most economically important diseases of carrot. Multiple Pythium species are the cause of cavity spot and the importance of each species have been found to differ from one country to another. Five species of Pythium are the most important in causing cavity spot in Norway: P. violae, P. sulcatum, P. sylvaticum, P. intermedium and what is believed to be a new species, given the preliminary name P. "vipa". We have established standard PCR assays for the detection of all these five Pythium species in soil. These diagnostic assays have also been further developed to allow quantitative detection of these same pathogens by real-time TaqMan PCR. Such a test can potentially be used to analyze fields in order to avoid cropping carrots where the corresponding pathogens are found and the consequent risk of developing cavity spot is high. Another potential benefit for such a test might be to use the test result from a growing field of carrots to predict the need to spray this field with pesticides. The general experience is that it is difficult to extract "good" DNA from soil samples, and inhibition of the PCR reaction is often observed. DNA extraction protocols often need to be optimized to reduce the amount of compounds that otherwise would inhibit PCR, e.g. humic acid, as much as possible. Additional purification steps, dilution of the DNA samples and an adjusted mastermix might reduce the problems. Strategies to improve the PCR-based detection of plant pathogens in soil will be discussed.
Sammendrag
Vegetation fire is the worldwide disturbance that affects the largest area and biggest biomes variety. Fire instantaneously generates large C fluxes to the atmosphere, as gas and soot particles. In the same time, part of ecosystem organic matter (OM) is converted into charred material that may contribute to the stable pool of soil organic carbon (SOC). The net effect of vegetation fire on C sequestration remains uncertain because the two major impacts operate at very different timescales and C budget is highly dependent on ecosystem and fire conditions. The aim of the present research was to assess fire-induced C fluxes to the atmosphere and as new litter and charcoal production during a prescribed fire in a subtropical oak shrub. Pre-fire biomass and post-fire charred and unburned biomass were determined for vegetation leaves and stems, litter and soil in 20 sub-plots installed in a 30-ha area prescribed for fire. Concentrations of C were determined, and fluxes among pools and to the atmosphere were derived from these measurements. In a first assessment, charred OM was visually identified in standing biomass and litter using its black and shiny aspect. In a second step, a strong chemical oxidation with K2Cr2O7/H2SO4 was used to isolate only a highly recalcitrant part of pyrogenic C. After the fire, standing dead biomass was only composed of stems with charred surface. The leaves transferred from vegetation to litter during the fire represented more than a half of post-fire litter. Percentage of initial C pool that was lost to the atmosphere as gas or particles was 55 % from vegetation stems, 80 % from vegetation leaves, and 70 % from litter. Soil C stocks were not significantly modified by fire, in agreement with moderate temperature elevation in the soil proper. Total C release to the atmosphere, including gas and particles, was 2.6 kg C m"2. Visually-identified charcoal represented 5% of remaining stem C (i.e. 60 g C m"2) and 21% of post-fire litter C (i.e. 80 g C m"2). The stem and litter charcoal contained 4±4 % and 16±5 % of highly recalcitrant C, respectively. We assessed that a typical scrubland fire may add between 10 and 140 g C m"2of chemically stable pyrogenic C to the soil. The conversion rate of ecosystem C to chemically stable pyrogenic C would be between 0.2 and 3.4 %.