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
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.
Sammendrag
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) is a RNA virus that belongs to the family Tymoviridae. Infection of poinsettia plants with PnMV results in mosaic symptoms during parts of the growing season and decrease 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 thus an urgent need for a new approach, like Agrobacterium-mediated transformation, which can overcome these difficulties. We have therefore developed an Agrobacterium-mediated transformation approach for poinsettia. Transgenic poinsettia plants with improved resistance against PnMV by expressing hairpin RNA constructs which targeted various regions of the virus genome were produced. Mechanical inoculation of PnMV and subsequent enzyme-linked immunosorbent assay (ELISA) confirmed the PnMV resistance. The siRNA analysis has demonstrated gene silencing mediated resistance. The PnMV resistant transgenic poinsettia lines produced are in the process of being commercialized. 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
Berit Nordskog David M. Gadoury May Bente Brurberg Tor Håkon Sivertsen Roy Kennedy Arne HermansenSammendrag
Downy mildews represent some of the most important plant diseases in the production of several field vegetable crops in Norway. Disease outbreaks are difficult to predict since severity of the diseases and the first appearance of the pathogens can differ substantially between seasons. As part of an ongoing project, the initial sources of inoculum for downy mildews of onion (Peronospora destructor), lettuce (Bremia lactucae) and cucumber (Pseudoperonospora cubensis) is investigated to ensure the use of appropriate control measures for these diseases in Norway. Necrotic leaf tissue from infected plants has been examined for the presence of oospores. Oospores have so far been found profusely in lettuce and sparsely in onion, but not in cucumber. Other aspects that are surveyed are the distribution of spores in air. Spore traps are used to identify both the initial appearance of inoculum, and the presence and amount of spores over a field. To determine spore quantities, real-time PCR has been applied to analyze daily spore catch. These results were compared to data from parallel spore traps where hourly numbers of spores are enumerated by use of microscope. An attempt to backtrack an early infection of P. cubensis was made by producing trajectories to show where possible sources of infection may be located in the case of long distance distribution of spores by air. This work will be continued in 2008 and 2009, and the results will be used for better forecasting of downy mildew pathogens in Norway.
Forfattere
Berit Nordskog David M. Gadoury May Bente Brurberg Tor Håkon Sivertsen Roy Kennedy Arne HermansenSammendrag
Bladskimmel utgjør noen av de viktigste plantesjukdommene i norske frilandsgrønnsaker. Sjukdomsutbrudd er vanskelige å forutse siden angrepsgrad og tidspunkt for første funn av patogenene kan variere fra sesong til sesong. Som del av et pågående prosjekt har smittekilder for bladskimmel i løk (Peronospora destructor), salat (Bremia lactucae) og agurk (Pseudoperonospora cubensis) blitt undersøkt for å sikre at riktige tiltak for kontroll gjennomføres. Forekomst av oosporer i blad og fordeling av sporer i luft har vært undersøkt. Dette arbeidet fortsettes i 2008 og 2009, og resultatene skal brukes til utvikling av bedre varsling av bladskimmelpatogener i Norge.
Forfattere
Berit Nordskog David M. Gadoury May Bente Brurberg Tor Håkon Sivertsen Roy Kennedy Arne HermansenSammendrag
Downy mildews represent some of the most important plant diseases in the production of several field vegetable crops in Norway. Disease outbreaks are difficult to predict since severity of the diseases and the first appearance of the pathogens can differ substantially between seasons. As part of an ongoing project, the initial sources of inoculum for downy mildews of onion (Peronospora destructor), lettuce (Bremia lactucae) and cucumber (Pseudoperonospora cubensis) is investigated to ensure the use of appropriate control measures for these diseases in Norway. Necrotic leaf tissue from infected plants has been examined for the presence of oospores. Oospores have so far been found profusely in lettuce and sparsely in onion, but not in cucumber. Other aspects that are surveyed are the distribution of spores in air. Spore traps are used to identify both the initial appearance of inoculum, and the presence and amount of spores over a field. To determine spore quantities, real-time PCR has been applied to analyze daily spore catch. These results were compared to data from parallel spore traps where hourly numbers of spores are enumerated by use of microscope. An attempt to backtrack an early infection of P. cubensis was made by producing trajectories to show where possible sources of infection may be located in the case of long distance distribution of spores by air. This work will be continued in 2008 and 2009, and the results will be used for better forecasting of downy mildew pathogens in Norway.
Sammendrag
Kålbladskimmel, forårsaket av Hyaloperonospora parasitica (Pers.) Constant., er utbredt i alle deler av verden hvor det dyrkes kålplanter. De første symptomene på kålbladskimmel viser seg vanligvis først på blader og blomsterstander, men alle overjordiske deler av planten kan bli infisert. Frøplanter vil lettere dø som resultat av en infeksjon enn eldre planter. Effekten av patogenet på senere vekststadier er generelt ikke så alvorlig, men kan medføre svekket kvalitet eller redusert avling. Kålbladskimmel er vanlig forekommende på en lang rekke kultur-, ugress- og prydplanter innen korsblomstfamilien (Brassicaceae), men det er noe uklart hvor stor vertsspesialiering patogenet har innen de ulike slekter og arter. Bladskimmelinfeksjoner er polysykliske og danner mange generasjoner med ukjønna konidiesporer i løpet av en sesong. I tillegg kan kålbladskimmel danne hvilesporer (oosporer) som bidrar til at patogenet kan overleve lenge i jord. Hvert trinn i livssyklusen, for eksempel sporespiring, infeksjon, latenstid og sporulering påvirkes av klimatiske forhold. En generell tommelfingerregel for kålbladskimmel er at sjukdommen er mest problematisk i felt ved temperaturer mellom 10 og 15 °C og høy luftfuktighet. Sporulering skjer hovedsakelig om natta og sporene slippes om morgenen når tørkende konidioforer vrir seg kraftig og slynger konidier ut i lufta. De første symptomene på kålbladskimmel kan være synlige allerede 3 til 4 døgn etter infeksjon av konidiene. Konidier av H. parasitica spres med vind og vannsprut lokalt i åkeren og mellom felt som ligger i samme dyrkingsområde. Det er også mulig at konidiene kan fraktes over lengre avstander med luftstrømmer i atmosfæren, men det er uklart hvor langt konidier av H. parasitica kan transporteres og fremdeles være spiredyktige. Dersom oosporer dannes kan disse overleve i planterester og i jord og opptre som primær smittekilde. Kålbladskimmel kan overvintre i vinterettårige, toårige eller flerårige korsblomstra vertplanter. Det er imidlertid noe uklart hvor stor betydning slike vertplanter har som smittekilde for grønnsakvekster. Forebyggende bekjempelse av kålbladskimmel innebærer fjerning av planterester, vekstskifte med ikke korsblomstra vekster og ugresskontroll for å begrense smittekilder lokalt. Systemer som varsler om klimaforhold som fremmer sporulering og infeksjon kan være et godt hjelpemiddel til å vurdere faren for utvikling av bladskimmel og finne riktig sprøytetidspunkt.
Sammendrag
Kålbladskimmel har de siste årene ført til problemer for dyrkere av korsblomstra grønnsaker, spesielt ruccola og brokkoli. I 2007 har det vært gjennomført et forprosjekt hvor en blant annet har kartlagt sjukdommen i sesongen, sett på effekten av ulike fungicider og gjennomført et litteraturstudium.
Sammendrag
Aerial dispersal of inoculum is critical to the spread of many plant diseases; including potato late blight (Phytophthora infestans (Pi)), lettuce downy mildew (Bremia lactucae (Bl)) and cucurbit downy mildew (Pseudoperonospora cubensis (Pc)). In addition to relative humidity and temperature, spore survival during aerial dispersal is affected by solar irradiation (SI), in particular during long-distance transport at higher altitudes. We evaluated the potential survival of spores in air by placing detached spores of Pi, Bl and Pc on filter paper in either direct sun or shade at time intervals from 0.5 to 3 h (Pi and Bl), or up to 42 hours (Pc). Thereafter, the filter papers were placed in moist chambers for 15 min prior to incubation on pea agar (Pi) or water agar (Bl and Pc) for 24 h, before the viable spores were enumerated. Spores were considered viable if they exhibited a germ tube or released zoospores. Preliminary results show that no spores of Pi, Bl and Pc germinated after 1, 3 and 30 h exposure to direct sun, with critical SI doses near 700, 2000 and 8500 Wm-2, respectively. In shade, no Pi spores germinated after 3 h, while spores of Bl and Pc were still viable after 3 and 42 h, respectively. In Norway, the potential for long distance distribution of Pi is restricted, but more likely for Bl and Pc. Further experiments will be conducted to find the maximum survival time for spores of these pathogens under Norwegian climatic conditions.
Sammendrag
Aerial dispersal of inoculum is critical to the spread of many plant diseases; including potato late blight (Phytophthora infestans (Pi)), lettuce downy mildew (Bremia lactucae (Bl)) and cucurbit downy mildew (Pseudoperonospora cubensis (Pc)). In addition to relative humidity and temperature, spore survival during aerial dispersal is affected by solar irradiation (SI), in particular during long-distance transport at higher altitudes. We evaluated the potential survival of spores in air by placing detached spores of Pi, Bl and Pc on filter paper in either direct sun or shade at time intervals from 0.5 to 3 h (Pi and Bl), or up to 42 hours (Pc). Thereafter, the filter papers were placed in moist chambers for 15 min prior to incubation on pea agar (Pi) or water agar (Bl and Pc) for 24 h, before the viable spores were enumerated. Spores were considered viable if they exhibited a germ tube or released zoospores. Preliminary results show that no spores of Pi, Bl and Pc germinated after 1, 3 and 30 h exposure to direct sun, with critical SI doses near 700, 2000 and 8500 Wm-2, respectively. In shade, no Pi spores germinated after 3 h, while spores of Bl and Pc were still viable after 3 and 42 h, respectively. In Norway, the potential for long distance distribution of Pi is restricted, but more likely for Bl and Pc. Further experiments will be conducted to find the maximum survival time for spores of these pathogens under Norwegian climatic conditions.
Forfattere
Björn Andersson J.E. Yuen G.J.T. Kessel B. Evenhuis L.J. Turkensteen A. Hannukkala A. Lehtinen B. Nielsen S. Ravnskov J.G. Hansen Arne Hermansen May Bente Brurberg Berit NordskogSammendrag
The role of oospores in the epidemiology of potato late blight