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Det ble sommeren 2017 gjennomført et kartleggingsprogram for å undersøke om importert plantemateriale av jordbær kunne være infisert av virus. Det ble tatt ut stikkprøver i jordbærfeltene hos utvalgte bærprodusenter som hadde baser sin produksjon på importerte planter, til sammen 150 prøver. Disse prøvene ble testet for fire bladlusoverførte virus som er relativt vanlige i Europa, men ikke i Norden: jordbær-nervebåndvirus (strawberry vein banding virus), jordbær-mildmosaikkvirus (strawberry mottle virus), jordbær-bladgulningvirus (strawberry mild yellow edge virus) og jordbærbladkrøllevirus (strawberry crinkle virus). Det ble påvist virus i prøver fra tre lokaliteter: strawberry crinkle virus ble funnet på tre steder, mens strawberry mild yellow edge virus ble funnet på ett sted i en prøve som hadde dobbeltinfeksjon med strawberry mild yellow edge virus og strawberry crinkle virus. Prøvene hadde ikke synlige symptomer.

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This study reports the findings of a distinct Potato virus Y (PVY) isolate found in Northeast China. One hundred and ten samples (leaves and tubers) were collected from potato plants showing mosaic symptoms around the city of Harbin in Heilongjiang province of China. The collected tubers were planted and let to grow in a greenhouse. New potato plants generated from these tubers showed similar symptoms, except for one plant. Subsequent serological analyses revealed PVY as the causing agent of the disease. A novel PVY isolate (referred to as HLJ-C-44 in this study) was isolated from this sample showing unique mild mosaic and crisped leaf margin symptoms. The complete genome of this isolate was analyzed and determined. The results showed that HLJ-C-44 is a typical PVY isolate. Phylogenetic analysis indicated that this isolate belongs to the N-Wi strain group of PVY recombinants (PVYN-Wi) and also shared the highest overall sequence identity (nucleotide and amino acid) with other members of this strain group. However, recombination analysis of isolate HLJ-C-44 revealed a recombination pattern that differed from that of other PVYN-Wi isolates. Moreover, biological assays in four different potato cultivars and in Nicotiana tabacum also revealed a different phenotypic response than that of a typical PVYN-Wi isolate. This data, combined, suggest that HLJ-C-44 is a novel PVY recombinant with distinct biological properties.

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Replication of all positive-sense single-stranded RNA viruses occurs in specific structures in close association with cellular membranes. Targeting of the viral replication complex (RC) to the site of replication is mediated by the interaction of viral-encoded proteins and host factors. Electron microscope studies have shown that Poinsettia mosaic virus (PnMV, family Tymoviridae) infection is associated with the presence of vesicular structures in the chloroplasts, which indicates that the replication of PnMV might occur in association with chloroplast-derived membranes. Using computer assisted homology search, we have identified that the coat protein (CP) of PnMV shows similarity to membrane bound proteins and contains a conserved amino acid sequence motif found in members of the Alb3/Oxa1/YidC protein family. This protein family is involved in the insertion of proteins into intracellular membranes. In this study we carried out localization studies combined with confocal laser microscopy to identify the cellular localization of the PnMV CP. Transient expression of red fluorescent protein (RFP)-tagged PnMV CP in Nicotiana benthamiana protoplast was shown to localize in the chloroplast.

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Chrysanthemum stunt viroid (CSVd) was first reported in US in the 1940s and is widespread in the world wherever chrysanthemum is grown. Cryotherapy of shoot tips, a new biotechnology developed in the recent years, is a novel application of plant cryopreservation techniques that allows pathogen eradication at a high frequency. Existing studies have proven that this technique can efficiently eradicate pathogens such as virus, phytoplasma and bacterium. However, up to now, there has been no report on viroid eradication. In the present study, we attempted to establish a droplet vitrification cryotherapy method for Argyranthemum and to apply it to eradicate CSVd. Results obtained so far demonstrated that cryotherapy of shoot tips alone failed to eradicate CSVd from the infected shoot tips of Argyranthemum maderense ‘Yellow Empire’. Using in situ hybridization of CSVd and histological analysis, we found that CSVd can invade meristematic cells and at the same time, these cells were able to survive following cryotherapy. These findings explained why cryotherapy of shoot tips alone could not be efficient enough to eradicate CSVd from the diseased materials. Further studies combining cold treatment with cryotherapy are under investigation for CSVd eradication.

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Bladlusoverført virus er et problem i potet i Norge. Hvert år er det settepotetpartier i den sertifiserte avlen som ikke kan godkjennes fordi innholdet av PVY/PVA er for høye. For høyt virusinnhold i potetprodusentenes egen oppformering er også et problem. For årene 2008, 2009, 2010 og 2011 har det blitt sendt inn virusprøver til NAK (Nederland) fra egne oppformerte settepoteter hos potetdyrkerne. Resultatene viste høye innhold av både PVA og PVY. Dette kan fort gi store avlingstap. I Norge har vi ikke god nok kunnskap om hvilke lusarter som herjer i potetåkre. Med bakgrunn i problemstillingen skissert over ønsket Norsk Landbruksrådgiving at Bioforsk Plantehelse skulle opparbeider seg mer kunnskap om følgende: Hvilke bladlusarter er det i norske potetåkre? Prosjekt: Kartlegging av bladlusarter i potetåkre. Hvor aktive er de i overføring av virus? Hvilken skade gjør disse bladlusartene i potetåkre i Norge? Prosjekt: Forsøk i potetåker med bladlusproblemer. Hvordan kan lus i potet overvåkes, for dermed å sette inn riktig tiltak til rett tid, slik at skader ikke oppstår i avlinga. For eksempel få til en ”indeks” (terskel) som ut fra bladluspopulasjonen angir når riset skal fjernes for å redusere virusmengden i settepotetene. Prosjekt: Vurderes når kartlegging og resultater fra forsøk er ”på plass”

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Det ble våren 2011 igangsatt et overvåkingsprogram for viroider i prydplanter i søtvierfamilien. Det ble analysert i alt 158 prøver av ulike arter og sorter. Prøvene ble først analysert med en PCRmetode som påviser alle viroider i slekten pospiviroider. Hver prøve ble deretter identifisert til art ved hjelp av sekvensering. Det ble påvist viroider i 19 prøver (12 % av prøvene). Potato spindle tuber viroid (PSTVd) ble påvist i 1 prøve av Petunia. Tomato apical stunt viroid (TASVd) ble påvist i til sammen 15 prøver: 1 prøve av Brugmanisa, 11 prøver av Solanum jasminoides og 3 prøver av S. rantonetti. Citrus exocortis viroid (CEVd) ble påvist i 3 prøver av S. jasminoides.

Sammendrag

Tomato chlorotic dwarf viroid ble nylig påvist i et tomatgartneri i Rogaland. Påvisning av viroid som skadegjører i tomat representerer noe nytt for plantehelsesituasjonen i Norge. Til tross for at dette viroidet ikke står på karante¬nelister, har det blitt rapportert om store skader ved angrep i veksthus i andre europeiske land. De siste 10 årene har det blitt klart at mange viroid opptrer latent i prydplanter, og at mange av de samme viroidene kan forårsake sterke symptomer og skade i tomat. De to viktigste spredningsveiene inn til tomatveksthusene er kontaktsmitte fra prydplanter som ikke viser symptomer, og frøsmitte.

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Agrobacterium-mediated transformation for poinsettia (Euphorbia pulcherrima Willd. Ex Klotzsch) is reported here for the first time. Internode stem explants of poinsettia cv. Millenium were transformed by Agrobacterium tumefaciens, strain LBA 4404, harbouring virus-derived 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 5 experiments utilizing 868 explants, 18 independent transgenic lines were generated. An average transformation frequency of 2.1% (range 1.2-3.5%) was revealed. 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 found among transformants. Transgenic poinsettia plants showing resistance to mechanical inoculation of PnMV were detected by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Northern blot analysis of low molecular weight RNA revealed that transgene-derived small interfering (si) RNA molecules were detected among the poinsettia transformants prior to inoculation. 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

An infectious cDNA clone of a Norwegian isolate of Poinsettia mosaic virus (PnMV) was generated. It consisted of 6,098 nucleotides and encoded a polyprotein of 219.5 kDa. Sequence comparisons indicated that this isolate shared 98.6% (nucleotide) and 97.1% (amino acid) identity with the previously sequenced isolate from Germany. RNA transcripts derived from this cDNA were infectious in Nicotiana benthamiana. However, plants did not present typical PnMV symptoms. Furthermore, RNA transcripts from this cDNA clone were not infectious in poinsettia. Serial propagation of this cDNA clone in N. benthamiana plants restored symptom induction in this host but did not re-establish infectivity in poinsettia.

Sammendrag

Vi vil presentere strategier for kontroll og metoder for å unngå spredning av bladlusoverførte virus, med potetvirus Y som eksempel. Vi vil også legge fram de siste resultatene fra prosjekter som er i gang, potetmopptoppvirus (PMTV) prosjektet og prosjektet på rattelvirus (TRV) som er nytt fra i år.

Sammendrag

Potato mop-top virus (PMTV) is the type member of the genus Pomovirus. PMTV is one of the most damaging potato infecting viruses due to the symptoms induced in the tubers. The symptoms caused by PMTV can be similar to the ones induced by another potato infecting virus, Tobacco rattle virus (TRV). Both viruses are known to generate great economic losses in Norway. Since the beginning of 2005, NCRI has as one of its objectives to enhance research on PMTV and will subsequently initiate studies on TRV as well.