Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Schmallenberg virus : technical and scientific studies
Poel, W.H.M. van der - \ 2014
Lelystad : Central Veterinary Institute of Wageningen UR - 67
dierpathologie - schmallenbergvirus - epidemiologie - pathogenese - transmissie - vectoren - diagnose - reverse transcriptase pcr - serologie - wilde dieren - huisdieren - kalveren - lammeren - koeien - schapen - animal pathology - schmallenberg virus - epidemiology - pathogenesis - transmission - vectors - diagnosis - serology - wild animals - domestic animals - calves - lambs - cows - sheep
Schmallenberg virus primarily infects domestic and wild ruminants. Cattle and sheep seem to be the most susceptible species. Goats, pigs and camelids seem to be less susceptible. In pregnant cattle and sheep, the virus can infect multiple organs of the un-borne fetus. However, this infection often does not cause major lesions and infrequently leads to malformations.
Bronnen van Aardappelvirus Y
Vlugt, R.A.A. van der; Bekkum, P.J. van; Raaij, H.M.G. van; Piron, P.G.M. ; Verbeek, M. ; Topper, C.G. ; Bus, C.B. ; Wustman, R. - \ 2012
Wageningen : Plant Research International, Business Unit Biointeracties en Plantgezondheid - 40
akkerbouw - aardappelen - aardappelvirus y - besmetters - waardplanten - aphididae - virus-gastheer interacties - vectoren - gewasbescherming - plantenvirussen - arable farming - potatoes - potato virus y - contaminants - host plants - virus-host interactions - vectors - plant protection - plant viruses
Mogelijke bronnen van besmettingen met het aardappelvirus Y (PVY) in aardappelen. In dit onderzoek is met name gekeken naar de rol van bladluizen als belangrijkste overbrengers (‘vectoren’) van PVY. Daarnaast is gekeken naar het mogelijk voorkomen van het virus in andere planten (m.n. onkruiden).
Verspreiding van komkommerbontvirus (CGMMV) door vogels
Stijger, I. ; Hamelink, R. ; Ludeking, D.J.W. - \ 2012
Bleiswijk : Wageningen UR Glastuinbouw (Rapporten WUR GTB 1213) - 15
komkommerbontvirus - verspreiding - preventie - vogels - vectoren - komkommers - cucumis sativus - kassen - glastuinbouw - nederland - cucumber green mottle mosaic virus - dispersal - prevention - birds - vectors - cucumbers - greenhouses - greenhouse horticulture - netherlands
Het komkommerbontvirus is een zeer persistent virus. De afgelopen jaren heeft het zich uitgebreid naar meerdere bedrijven. Door komkommertelers worden veel verschillende maatregelen op het gebied van hygiëne doorgevoerd om het virus uit de kas te houden of om verspreiding te voorkomen. Ondanks deze maatregelen komt het virus toch soms in ongrijpbare patronen voor in de kas. In een onderzoek is nagegaan of vogels een vector kunnen zijn voor het virus. Vogels worden waargenomen in kassen en kunnen gemakkelijk door de luchtramen in en uit de kas vliegen. In het onderzoek konden ze de proefkas niet uit omdat de ramen waren afgegaasd. In deze kas met virus geïnfecteerde planten en gezonde komkommerplanten is vastgesteld dat vogels komkommerbontvirus kunnen verspreiden. In het onderzoek bleek dit al mogelijk 23 dagen nadat gezonde vogels in de kas waren losgelaten. Telers zullen dus alert moeten zijn op het invliegen van vogels. Aan de buitenkant van een vogel is niet te zien of deze virus bij zich heeft. Indien er in de buurt ook komkommers worden geteeld en bekend is dat daar virus in voorkomt dan moeten vogels wel degelijk tot mogelijke verspreiders worden gerekend
Olfaction in vector-host interactions
Takken, W. ; Knols, B.G.J. - \ 2010
Wageningen : Wageningen Academic Publishers (Ecology and control of vector-borne diseases vol. 2) - ISBN 9789086860913
gastheren (dieren, mensen, planten) - gewervelde dieren - hematofage geleedpotigen - ziekten overgebracht door vectoren - gastheer parasiet relaties - vectoren - vectorbestrijding - hosts - vertebrates - haematophagous arthropods - vector-borne diseases - host parasite relationships - vectors - vector control
This book addresses the topic how blood-feeding arthropods interact with their vertebrate hosts. As the transmission of infectious vector-borne pathogens is much dependent on the contact between vector and host, the efficacy of host location is of profound importance. Interruption of vector-host contact is considered on of the most effective means of vector-borne disease control, as is currently witnessed by the successful use of insecticide-treated bed nets for malaria control in sub-Saharan Africa.
Ontdek je plekje: ook voor teken
Gassner, F. - \ 2009
Nature Today 2009 (2009)10-11.
metastigmata - tekenbeten - vectoren - gastheerpreferenties - acaridae - tick bites - vectors - host preferences
Door de regen en koude nachten neemt het aantal actieve teken sterk af. Toch worden nog steeds actieve teken aangetroffen. De vraag die veel gesteld wordt, is hoe teken bepalen in welke beesten ze zich vastbijten en welk lichaamsdeel de voorkeur heeft.
Populatiedynamica van trips in relatie tot vectorfunctie
Stijger, C.C.M.M. ; Derks, A.F.L.M. ; Vlugt, R.A.A. van der - \ 2008
plantenvirussen - teelt onder bescherming - tomatenbronsvlekkenvirus - detectie - thysanoptera - vectoren - glastuinbouw - plant viruses - protected cultivation - tomato spotted wilt virus - detection - vectors - greenhouse horticulture
Doel van het onderzoek was na te gaan welke factoren bepalend zijn voor de schade die tospovirussen veroorzaken in kasteelten
Tabaksratelvirus in aardappel
Hoek, H. - \ 2006
Kennisakker.nl 2006 (2006)15 maart.
pootaardappelen - tabaksratelvirus - plantenvirussen - plantenziekten - nematoda - vectoren - ziekten overgebracht door vectoren - landbouwkundig onderzoek - akkerbouw - seed potatoes - Tobacco rattle virus - plant viruses - plant diseases - vectors - vector-borne diseases - agricultural research - arable farming
Aardappel is vatbaar voor het tabaksratelvirus (TRV). Bij gevoelige aardappelrassen kan aantasting door dit virus dit leiden tot kringerigheid in de knollen. Tabaksratelvirus wordt overgebracht door aaltjes die behoren tot de geslachten Trichodorus of Paratrichodorus. Van TRV zijn meerdere virustypen bekend. Een aaltjessoort kan maar één virustype overbrengen. Tot voor kort werd aangenomen dat TRV niet of nauwelijks via pootgoed overgaat en dat besmetting met TRV niet ten koste gaat van de opbrengst. Bovendien werd verondersteld dat het virus bij gevoelige rassen wordt ingekapseld, waardoor het niet overdraagbaar zou zijn In dit onderzoek van het PPO-AGV is aangetoond dat TRV met het pootgoed kan overgaan. De mate van vatbaarheid voor TRV, van gevoeligheid voor kringerigheid en van overdraagbaarheid via pootgoed is afhankelijk van het ras, het virustype en de interactie tussen ras en virustype. Het virustype hangt samen met het Trichodoride aaltje dat de eerste infectie heeft veroorzaakt. In het rassenonderzoek aardappelen zullen de rassen dan ook met meerdere Trichodoride soorten getoetst moeten worden.
Perspectieven voor bestrijding van Verticillium fungicola in de champignonteelt
Baar, J. ; Rutjens, A.J. ; Kogel, W.J. de; Zijlstra, C. - \ 2005
gewasbescherming - paddestoelen - lecanicillium fungicola - plantenziekteverwekkende schimmels - vectoren - megaselia halterata - biologische bestrijding - biopesticiden - moleculaire detectie - plant protection - mushrooms - plant pathogenic fungi - vectors - biological control - microbial pesticides - molecular detection
Voor de bestrijding van Verticillium fungicola in de champignonteelt is een moleculaire detectietest ontwikkeld. Daarnaast zijn nieuwe biologische gewasbeschermingsmiddelen tegen Verticillium fungicola en Megaselia halterata in ontwikkeling
Nieuwe feiten over hardnekkige necrose in freesia
Middelburg, A.F. ; Verbeek, M. - \ 2005
Vakblad voor de Bloemisterij 60 (2005)4. - ISSN 0042-2223 - p. 44 - 45.
iridaceae - freesia - plantenziekten - afwijkingen, planten - necrosen - plantenvirussen - schimmels - vectoren - landbouwkundig onderzoek - plant diseases - plant disorders - necroses - plant viruses - fungi - vectors - agricultural research
Onderzoek van PRI en Naktuinbouw heeft aan het licht gebracht dat bladnecrose waarschijnlijk wordt veroorzaakt door een ophiovirus dat overgebracht wordt door een vrij algemene schimmel: Olpidium brassicae. Bovendien is er een methode ontwikkeld om uitgangsmateriaal te toetsen op het gevonden ophiovirus. Veredelen op resistentie tegen necrose of onderzoek naar het bestrijden van de schimmel, lijken de manieren om necrose de baas te worden
New insights in freesia leaf necrosis disease
Verbeek, M. ; Meekes, E.T.M. - \ 2005
FlowerTECH 8 (2005)3. - ISSN 1388-8439 - p. 14 - 15.
iridaceae - freesia - plantenziekten - afwijkingen, planten - necrosen - plantenvirussen - schimmels - vectoren - landbouwkundig onderzoek - plant diseases - plant disorders - necroses - plant viruses - fungi - vectors - agricultural research
Onderzoek van PRI en Naktuinbouw heeft aan het licht gebracht dat bladnecrose waarschijnlijk wordt veroorzaakt door een ophiovirus dat overgebracht wordt door een vrij algemene schimmel: Olpidium brassicae. Bovendien is er een methode ontwikkeld om uitgangsmateriaal te toetsen op het gevonden ophiovirus. Veredelen op resistentie tegen necrose of onderzoek naar het bestrijden van de schimmel, lijken de manieren om necrose de baas te worden
Het gebruik van bijen en hommels als vector als vector van antagonisten voor de bestrijding van bloemverwelking (mucor) bij aubergines
Smeekens, C.C. - \ 2003
Zoetermeer : Productschap Tuinbouw - 13
aubergines - solanum melongena - mucor - bijenblazers - bombus - antagonisten - vectoren - gewasbescherming - plantenziektebestrijding - teelt onder bescherming - bee blowers - antagonists - vectors - plant protection - plant disease control - protected cultivation
Het onderzoek is uitgevoerd door Praktijkonderzoek Plant en Omgeving (PPO) sector bijen in samenwerking met PPO sector glastuinbouw (Test locatie: PPO glastuinbouw in Naaldwijk)
De kwalijke rol van kevers : overbrenging Salmonella en Campylobacter
Bolder, N.M. ; Jacobs-Reitsma, W.F. ; Wagenaar, J.A. ; Hazeleger, W.C. ; Beumer, R.R. - \ 2003
De Pluimveehouderij 33 (2003)50. - ISSN 0166-8250 - p. 14 - 15.
coleoptera - insecten - vectoren - ziekteoverdracht - salmonella - enterobacteriaceae - campylobacter - spirillaceae - onderzoek - pluimveehouderij - veehouderijbedrijven - huisvesting van kippen - insects - vectors - disease transmission - research - poultry farming - livestock enterprises - chicken housing
De vraatzucht van kevers aan isolatiemateriaal in stallen valt wel mee. Inmiddels is echter bekend dat piepschuimkevers verantwoordelijk kunnen zijn voor de overdracht van verschillende infectieziekten zoals Salmonella, Campylobacter, E.coli en allerlei virusziekten
Slabobbelblad en slakringnecrose, twee complexe ziekten
Verbeek, M. ; Wilk, F. van der - \ 2002
Gewasbescherming 33 (2002)2. - ISSN 0166-6495 - p. 49 - 51.
lactuca sativa - slasoorten - plantenziekten - plantenvirussen - diagnostische technieken - epidemiologie - vectoren - plantenziekteverwekkende schimmels - bladgroenten - lettuces - plant diseases - plant viruses - diagnostic techniques - epidemiology - vectors - plant pathogenic fungi - leafy vegetables
Onderzoek naar de vector van slabobbelblad en slakringnecrose, virusziekten die door bodemschimmels kunnen worden overgebracht
Wiskunde in Werking Dl. 1: vectoren en matrices toegepast
Gee, M. de - \ 2001
Utrecht : Epsilon (Epsilon uitgaven 48) - ISBN 9789050410632 - 288
wiskunde - vectoren - matrices - studieboeken - vectoranalyse - mathematics - vectors - textbooks - vector analysis
De eerste vier hoofdstukken van dit boek komen in licht gewijzigde vorm overeen met hoofdstukken uit Wiskunde in Werking (deel 28 in deze reeks). Het vijfde hoofdstuk is wat meer verdiepend. De klassieke basisstof uit de differentiaal- en integraalrekening en de lineaire algebra is verdeeld in betrekkelijk kleine eenheden, die de student zich door zelfstudie kan eigen maken. De docent speelt hierbij eerder een begeleidende dan een docerende rol. Bij deze zelfstudie wordt tevens veel aandacht besteed aan het bestuderen van concrete voorbeelden en oefeningen. De wiskundige technieken die worden aangedragen, worden direct ingebed in toepassingen, waardoor de verbinding tussen toepassing en wiskunde zeker zo belangrijk is als de wiskunde zelf.
Veeaankoop op melkveebedrijven nog geen verleden tijd
Hanekamp, W. - \ 2000
Praktijkonderzoek Rundvee, Schapen en Paarden. Praktijkonderzoek 13 (2000)3. - ISSN 1386-8470 - p. 34 - 35.
melkveehouderij - melkveebedrijven - inkopen - handel - melkvee - ziekteoverdracht - vectoren, ziekten - vectoren - diergeneeskunde - agrarische bedrijfsvoering - diergezondheid - dairy farming - dairy farms - purchasing - trade - dairy cattle - disease transmission - disease vectors - vectors - veterinary science - farm management - animal health
Uit I&R cijfers blijkt dat 70 % van de melkveebedrijven regelmatig vee aanvoert. Dit ondanks het feit dat bekend is dat aankoop van vee een grote risicofactor is voor de insleep van ziektekiemen.
Competence and specificity of thrips in the transmission of tomato spotted wilt virus
Nagata, T. - \ 1999
Agricultural University. Promotor(en): R.W. Goldbach; D. Peters. - S.l. : Nagata - ISBN 9789058080769 - 96 p.
tomatenbronsvlekkenvirus - plantenvirussen - plantenziekteverwekkers - plantenziekten - thrips - vectoren - transmissie - landbouwkundige entomologie - tomato spotted wilt virus - plant viruses - plant pathogens - plant diseases - vectors - transmission - agricultural entomology
<p>The study described in this thesis aims to elucidate the fate and pathway of ingested TSWV in thrips during their development from larvae to adult. Insight in this process will contribute to a better understanding of the factors regulating and determining vector competence and specificities.<p>Analysis of the differences in virus susceptibility among thrips species or populations was approached by infection of cell cultures. The methodology developed and the media used to prepare primary cell cultures of the species <em>F. occidentalis</em> and <em>T. tabaci</em> are described and discussed in Chapter 2. The cultures obtained were derived from an efficiently transmitting <em>F. occidentalis</em> population and from a non-transmitting <em>T.</em><em>tabaci</em> population which was not able to transmit the virus. The results obtained by inoculation of these cultures with preparations of purified TSWV particles are described in Chapter 3. To analyse the tissue tropism of TSWV in thrips in relation to its vector competence, a novel histological technique, called whole mount immunofluorescent staining (WMIS) was developed (Chapter 4). Using this technique and other immunohistochemical techniques, infection of the midguts and salivary glands during the development of <em>F. occidentalis</em> thrips was described (Chapter 4). By the combination of all techniques, the temporal development of the virus infection in larvae and adults could be elucidated. To define the various barriers which may regulate the development of virus infection, specific TSWV mutants were used which failed either to infect the thrips or to convert the thrips in a transmitter after infection. Definite barriers were observed at the level of virus entry in the midgut epithelium or virus escape from the midgut to the salivary glands (Chapter 5). The pathway of the virus within the thrips and the mechanism determining the vector specificities were further unravelled by analysing the infection in thrips of a transmitting F. occidentalis population and a nontransmitting T. tabaci population (Chapter 6). Concluding remarks of this study is presented in Chapter 7.
The molecular basis of the interactions between luteoviruses and their aphid vectors
Hogenhout, S.A. - \ 1999
Agricultural University. Promotor(en): R.W. Goldbach; J.F.J.M. van den Heuvel. - S.l. : Hogenhout - ISBN 9789058080523 - 119 p.
luteovirus - plantenvirussen - plantenziekteverwekkers - plantenziekten - vectoren - transmissie - aphididae - landbouwkundige entomologie - interacties - plant viruses - plant pathogens - plant diseases - vectors - transmission - agricultural entomology - interactions
<p>Luteoviruses essentially replicate in the phloem tissue and are transmitted from plant to plant by aphids in a circulative, persistent manner. Virus particles are acquired when aphids feed on phloem sap. Particles are then transported from the midgut or hindgut into the haemolymph and from the haemolymph to the salivary gland, to be eventually released with the saliva to the phloem of uninfected plants. There is no evidence that luteoviruses replicate in the aphid vector. The haemolymph acts as a reservoir in which luteoviruses should persist in an infecting form during the whole lifespan of aphids.</p><p>A virus overlay technique was developed for the characterization of aphid-derived proteins involved in the circulative transmission of luteoviruses by aphids (Chapter 2). Proteins from whole-body homogenates of the aphid species <em>Myzus persicae</em> were separated with a two-dimensional denaturing poly-acrylamide gel (SDS-PAGE) and transferred to nitrocellulose membranes. Subsequently, these membranes were incubated with purified <em>Potato leafroll virus</em> (PLRV; genus <em>Polerovirus</em> ; Family <em>Luteoviridae</em> ) particles. Bound virus particles were detected by incubating membranes with anti-PLRV IgG and phosphatase conjugated goat anti-rabbit IgG. Thus it was demonstrated that PLRV particles bind to five different proteins. A protein of 63 kilodalton (p63) had the highest affinity for PLRV particles and was characterized by N-terminal amino-acid sequencing and immuno-gold labeling studies. These studies revealed that this protein is a homologue of GroEL and is abundantly synthesized by the primary bacterial endosymbiont ( <em>Buchnera</em> sp.) of <em>M. persicae</em> .</p><p>To show whether PLRV particles and <em>Buchnera</em> GroEL also interact <em>in vivo</em> , aphids were fed on diets containing tetracyclin (Chapter 2). This antibiotic acts as bacteriostatic by inhibiting protein synthesis. After a tetracyclin treatment, <em>Buchnera</em> GroEL was not detected in the haemolymph of the aphid, virus transmission was reduced by more than 70%, and the major viral capsid protein was degraded. These observations led to the suggestion that <em>Buchnera</em> GroEL is involved in protection of virus particles against proteolytic breakdown during circulation in the haemolymph.</p><p>To study the interaction of PLRV and <em>Buchnera</em> GroEL of <em>M. persicae</em> (MpB GroEL) in more detail, the gene encoding MpB GroEL and its flanking sequences were characterized and compared to those of <em>Escherichia coli</em> and <em>Buchnera</em> spp. of other aphid species (Chapter 3). The MpB GroEL encoding gene appeared to be part of an operon with a similar organization as the <em>groE</em> operon of <em>E. coli</em> , containing another gene for a 10-kDa protein with sequence similarities to GroES of <em>E. coli</em> . However, a constitutive promoter sequence comparable to that of the <em>E. coli</em><em>groE</em> operon could not be identified; only sequences comparable to the heat shock promoter of the <em>E. coli groE</em> operon were observed. Comparison of the deduced amino-acid sequences disclosed that MpB GroEL is approximately 98% similar to GroELs of other <em>Buchnera</em> spp. and 92% similar to <em>E. coli</em> GroEL. These results demonstrate that MpB GroEL belongs to the family 60-kDa chaperonin or heat shock protein family.</p><p>Several functions of GroEL proteins have been described and the most important one is the folding of nonnative proteins inside the cytosol of prokaryotes, mitochondria and chloroplasts. MpB GroEL and other GroEL proteins have typical double-doughnut structures composed of two stacked rings of seven subunits each. Using the crystal structure of <em>E. coli</em> GroEL, computer-generated structural predictions of the monomer of MpB GroEL was obtained (Chapter 3). Like <em>E. coli</em> GroEL, each subunit of MpB GroEL consists of an apical, an intermediate and an equatorial domain. The apical domain is a continuous domain on the primary MpB GroEL protein structure, whereas the equatorial and intermediate domains are discontinuous with regions located at the N- and C-terminus of the MpB GroEL subunit. The N- and C-terminal regions of the equatorial and intermediate domains assemble in the folded structure of MpB GroEL.</p><p>Functional studies of <em>E. coli</em> GroEL 14-mers have demonstrated that the apical domains are located at both sides of the cylindrical double-doughnut structure and contains amino acids involved in binding of nonnative proteins. The equatorial domains form the waist of the GroEL 14-mer. Intermediate domains function as hinges for moving the apical domain up and down so that amino acids in the apical domain can bind the unfolded protein. Subsequently, unfolded proteins are kept in the cavity of the GroEL 14-mer where they obtain their native structure without being disturbed by cytosolic compounds.</p><p>To investigate which of the domains of MpB GroEL are involved in binding PLRV particles, deletion mutants were designed based on the primary structure of the MpB GroEL protein (Chapter 3). Full-length MpB GroEL and MpB GroEL deletion mutants were expressed in fusion with glutathione-S-transferase (GST) in <em>E. coli</em> and affinity-purified. The GST moiety was removed and similar amounts of recombinant protein were tested for PLRV binding in virus overlay assays. This revealed that recombinant full-length MpB GroEL proteins had a similar affinity for PLRV particles as wild type MpB GroEL proteins isolated from <em>M. persicae</em> . PLRV particles displayed affinity for MpB GroEL deletion mutants only if they still contained the N- or C-terminal regions of the equatorial domain. Strikingly, PLRV-binding to polypeptides containing the apical domain alone or when extended with flanking sequences did not bind PLRV. Furthermore, virus overlay assays with additional MpB GroEL deletion mutants demonstrated that determinants for PLRV binding at the C-terminal part of the equatorial domain are located between residues 408 and 475 of MpB GroEL (Chapter 4). This region comprises threeα-helices.</p><p>Since the N- and C-terminal regions of the equatorial domain assemble in the folded structure of MpB GroEL, the two PLRV-binding regions may become a single PLRV-binding site. The finding that the equatorial domain was involved in binding PLRV particles and not the apical domain is surprising, since studies of <em>E. coli</em> GroEL showed that the apical domain is involved in binding of unfolded proteins in the cytosol of <em>E. coli</em> cells. PLRV particles may have different binding characteristics because of the size limitation of the central cavity of the GroEL molecule and the fact that binding occurs extracellularly in the haemolymph.</p><p>The interaction between PLRV particles and MpB GroEL was investigated in more detail (Chapter 4). Virus overlay studies with additional MpB GroEL deletion mutants revealed that regions between amino acid residues 1 and 57, and 427 and 457 of the N- and C-terminal regions of the equatorial domain, respectively, contain the determinants for PLRV binding. To determine which amino acids are involved in PLRV binding, overlapping decameric peptides of PLRV-binding regions were synthesized and incubated with virus particles in a virus overlay based experiment (Chapter 4). Alanine replacement studies of binding peptides showed that amino acids R13, K15, L17 and R18 of the N-terminal region of the equatorial domain, and R441 and R445 of the C-terminal region of the equatorial domain are responsible for PLRV binding. Alanine replacement of R13, K15, L17 and R18 eliminated PLRV binding of MpB GroEL(1-408) completely, whereas replacement of R441 and R445 reduced, but not eliminated, virus binding of MpB GroEL(122-548). This suggests that besides R441 and R445 other residues in the C-terminus are part of the PLRV-binding site.</p><p>These still unknown residues are likely to be located in the region between amino acids 427 till 474, which comprises oneα-helix located to the outside of GroEL 14-mers. Residues R13, K15, L17 and R18 are located in a longα-helix that is present more internally of GroEL 14-mers. The N- and C-terminal amino acids are positioned behind each other in a cavity, which might be accessible for the readthrough domain (RTD) which protrudes from the surface of a luteovirus particle.</p><p>The luteovirus protein capsid is composed of a major 23-kDa coat protein (CP), and lesser amounts of a ~54-kDa readthrough protein, expressed by translational readthrough of the CP into the adjacent open reading frame encoding the RTD. The RTD is exposed on the surface of the virus particle and contains the determinants necessary for virus transmission by aphids. To study whether the highly conserved major CP or the RTD of the minor 54-kDa protein are involved in GroEL binding, BWYV mutants devoid of the RTD were synthesized and tested for GroEL affinity in a GroEL-ligand assay (Chapter 5). It was found that the BWYV RTD mutants did not bind GroEL, indicating that the RTD contains the GroEL-binding determinants. BWYV mutants lacking the RTD domain were also injected into the haemolymph of aphids and the persistence of these mutants was compared with those of wild-type virus particles (Chapter 5). These studies clearly showed that BWYV mutants devoid of the RTD were more rapidly degraded than wild-type viruses, indicating that the RTD, containing the GroEL-binding sites, is crucial for the persistency in the aphid.</p><p>To reveal whether conserved domains of the RTD are involved in GroEL binding, five luteoviruses belonging to the genus <em>Polerovirus</em> and <em>Pea enation mosaic virus</em> (PEMV; <em>Enamovirus</em> ) were tested for binding to <em>Buchnera</em> GroEL proteins isolated from several aphid species using GroEL-ligand assays (Chapter 5). All luteoviruses displayed a specific but differential affinity for the GroEL homologues isolated from the endosymbiotic bacteria of both vector and non-vector aphid species, and for <em>E. coli</em> GroEL. This indicates that GroEL is not involved in vector specificity. Sequence alignment of the RTDs of different luteoviruses and PEMV revealed that only the N-terminal half of the RTDs is conserved, whereas the C-terminal halves have no global sequence identity. This C-terminal region is also lacking from the PEMV RTD. The highest overall level of sequence similarity in the RTD extends from position 184 to 223 where about 23% of the residues are identical.</p><p>To assess whether the viral determinants required for the interaction of luteoviruses with <em>Buchnera</em> GroEL reside in the conserved region of the RTD, GST-fusions of the RTD and mutants thereof were expressed in <em>E. coli</em> (Chapter 6). After affinity purification, the GST moiety was cleaved and the resulting RTD protein tested for MpB GroEL affinity using a GroEL-ligand assay. This showed that the conserved region of the RTD plays a crucial role in binding GroEL.</p><p>The knowledge derived from the binding studies of GroEL and luteoviruses is valuable for the development of specific control methods. The fact that <em>Buchnera</em> GroEL and luteoviruses directly interact <em>in vitro</em> suggests that this occurs in the haemolymph of aphids as well. Consequently, peptides or antibodies that interfere in this interaction by binding to the equatorial domain of <em>Buchnera</em> GroEL or the RTD of luteoviruses reduce specifically the transmission efficiency of luteoviruses by aphids. It is possible to produce these interfering compounds by plants so that aphids acquire them while feeding. Further studies should reveal whether there are possibilities for transporting peptides or antibodies from the gut to the haemolymph.</p><p>Chapter 7 of this thesis describes an investigation that may lead to an alternative control strategy. In this chapter the effects of neem ( <em>Azadirachta indica</em> A. Juss) seed kernel extracts (NSKE) and its major active compound, azadirachtin, on the ability of <em>M. persicae</em> to transmit PLRV is studied. This secondary plant metabolite has major effects on bacterial symbionts of leafhoppers. Since endosymbiotic bacteria play a major role in the performance of aphids and luteovirus transmission by aphids, it was investigated whether treatments with these compounds would exert an effect on aphid larval growth and mortality, and on the aphid intracellular symbionts. The neem metabolites displayed a 100% mortality at doses higher than 2560 ppm., and morphological aberrations on the bacterial endosymbionts were observed. At doses lower than 160 ppm of NSKE or azadirachtin, the endosymbiont population of <em>M. persicae</em> , and mortality, growth and feeding behavior was similar to that of the untreated groups of aphids. However, PLRV transmission was inhibited by 40-70%. These observations raise the possibility that interfering with the relationship between endosymbionts and aphids may contribute to the control of luteovirus transmission by aphids.</p>
Lintwormen bij schapen niet gauw gevaarlijk voor de mens
Borgsteede, F.H.M. - \ 1997
Het Schaap (1997)5. - ISSN 0165-3156 - p. 36 - 37.
diergeneeskunde - schapen - geiten - helminthosen - honden - darmen - parasieten - dieren - parasitologie - vectoren - echinococcus granulosus - veterinary science - sheep - goats - helminthoses - dogs - intestines - parasites - animals - parasitology - vectors
Schapen kunnen fungeren als tussengastheer van 4 lintwormsoorten die alle de hond als eindgastheer hebben. Een van deze 4 is ook gevaarlijk voor de mens, namelijk Echinococcus granulosus. het gevaar komt dan niet van het schaap, maar van de eindgastheer, de hond
Recent studies on peanut bud necrosis disease. Proc. Meeting ICRISAT.
Buiel, A.A.M. ; Parlevliet, J.E. ; Lenné, J.M. - \ 1995
Patancheru [etc.] : ICRISAT [etc.] - ISBN 9789290663188 - 76
Arachis hypogaea - geleedpotigen - ziekteresistentie - aardnoten - insecten - plaagresistentie - plantenveredeling - plantenziekten - plantenplagen - plantenvirussen - planten - Thrips - Thysanoptera - tomatenbronsvlekkenvirus - vectoren - virussen - Thrips palmi - arthropods - disease resistance - groundnuts - insects - pest resistance - plant breeding - plant diseases - plant pests - plant viruses - plants - tomato spotted wilt virus - vectors - viruses
Virus - vector relationships in the transmission of tospoviruses
Wijkamp, I. - \ 1995
Agricultural University. Promotor(en): R.W. Goldbach; D. Peters. - S.l. : Wijkamp - ISBN 9789054854487 - 143 p.
plantenziekten - plantenziekteverwekkende bacteriën - tomatenbronsvlekkenvirus - plantenplagen - epidemiologie - distributie - virussen - vectoren - psocoptera - plant diseases - plant pathogenic bacteria - tomato spotted wilt virus - plant pests - epidemiology - distribution - viruses - vectors
<p>Tomato spotted wilt virus (TSWV), member of the genus <em>Tospovirus</em> within the family <em>Bunyaviridae,</em> ranks among the top ten of economically most important plant viruses. Tospoviruses cause significant yield losses in agricultural crops such as tomato, lettuce, pepper, tobacco, potato and groundnut, but also in ornamentals like chrysanthemum, alstroemeria, gloxinia and impatiens. Currently, more than 650 different plant species belonging to more than 70 distinct botanical families are known to be susceptible to tospoviruses. Following the introduction of the vector <em>Frankliniella occidentalis</em> from the United states in Europe, TSWV and impatiens necrotic spot virus (INSV), a tospovirus mainly occurring in ornamentals, are prevailing in the Netherlands, especially in greenhouse cultivations.<p>To gain more insight in the epidemiology of tospoviruses, information is needed on the kinetics of their transmission. The experiments described in this thesis were done to analyze some of the parameters involved.<p>An efficient local lesion assay was developed to facilitate transmission studies using leaf disks of <em>Petunia x hybrida</em> "Blue Magic". In this assay, transmission could be scored reliably within 2 to 3 days on the basis of local lesion formation. This assay also enabled easy handling of large numbers of thrips. Besides petunia, leaf disks of other plant hosts were found to be suitable as substrate in transmission studies as well.<p>Using this assay it was established that <em>F. occidentalis</em> could acquire and transmit the virus in periods of 5 min. Longer periods were required for more efficient transmission. To quantify virus transmission the median acquisition (AAP <sub><font size="-2">50</font></sub> ) and inoculation access periods (IAP <sub><font size="-2">50</font></sub> ), i.e. the periods needed for 50% of the thrips to respectively acquire or inoculate the virus were determined. The value for the AAP <sub><font size="-2">50</font></sub> was 67 min whereas an IAP <sub><font size="-2">50</font></sub> of 59 min was found. The leaf disk assay was also employed to determine the efficiency of transmission and the latent period (LP), the period between acquisition and inoculation of the virus, for both TSWV and INSV. The majority of thrips already transmitted virus at the end of the second larval stage at transmission rates for TSWV or INSV of 52.8 % or 80.0%, respectively.<p>The fate of the virus in the thrips after ingestion was studied in different developmental stages of <em>F. occidentalis.</em> The accumulation of two viral proteins, the nucleocapsid (N) and a non-structural (NS <sub><font size="-2">S</font></sub> ) protein, as monitored by ELISA en Western blot analyses, increased within two days above the levels initially ingested. Immunocytology of infected adults confirmed that viral products were present in high amounts, especially, in the salivary glands. Electron microscopic studies revealed the presence of many virus particles in the salivary ducts. These results unequivocally demonstrated that TSWV replicated in its insect vector and that the salivary glands were a major site of multiplication. This multiplication was not accompanied by pathological effects on the vector. No effect of virus infection was found on development time, reproduction rate and survival . This study al so revealed that no transovarial transmission of virus to the progeny took place.<p>The vector competence was determined for four thrips and four tospovirus species. The results showed that specificity of transmission, as occurring for other insect-transmitted plant viruses, also exists for tospovirus transmission by thrips. <em>F. occidentalis</em> appeared to be the most efficient vector for all 4 viruses tested, i.e. TSWV, INSV, tomato chlorotic spot virus (TCSV) and groundnut ringspot virus (GRSV). <em>Frankliniella schultzei</em> transmitted three (TSWV, TCSV and GRSV) of the four tospoviruses, whereas <em>Frankliniella intonsa,</em> not yet reported as tospovirus vector, transmitted TSWV and TCSV. Of <em>Thrips</em><em>tabaci,</em> previously known as an important vector for TSWV, only one out of four populations tested was able to transmit TSWV at, moreover, a low efficiency.<p>Finally, the transmission of mutant tospoviruses, which were generated after successive mechanical transfers of virus, was studied. Defective interfering mutants were found to be transmittable by thrips, albeit at a frequency 10 to 20 times lower than the wild type virus. In contrast, envelope deficient mutants were not transmitted by thrips, indicating the importance of the envelope glycoproteins in virus-vector relationships.
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