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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    Op het spoor van de boktor
    Kleis, R. ; Copini, P. - \ 2015
    Resource: weekblad voor Wageningen UR 20 (2015)6. - ISSN 1874-3625 - p. 18 - 19.
    cerambycidae - plantgezondheid - plantenplagen - bossen - bomen - acer palmatum - jaarringen - dissertaties - cerambycidae - plant health - plant pests - forests - trees - acer palmatum - growth rings - theses
    Boktorren die uitvliegen laten sporen na in hun kraamkamer. Promovendus Paul Copini leest die sporen in jaarringen van bomen en kan zeggen wanneer de boktor is geboren. Een oordeel met gewicht.
    Bedrijven financieren weinig promotieonderzoek : dossier universiteit en bedrijf
    Sikkema, A. ; Winkel, G.L. van; Velez Ramirez, A.I. - \ 2015
    Resource: nieuwssite voor studenten en medewerkers van Wageningen UR 9 (2015)18. - ISSN 1389-7756 - p. 12 - 15.
    universitair onderzoek - financieren - publiek-private samenwerking - universiteiten - dissertaties - university research - financing - public-private cooperation - universities - theses
    Steeds meer onderzoek van Wageningen Universiteit wordt betaald en bepaald door externe financiers. Dat roept vragen op – wie stuurt het Wageningse onderzoek? Resource dook eens grondig in het promotieonderzoek, het leeuwendeel van de wetenschappelijke productie op de universiteit. De belangrijkste financiers zijn niet bedrijven. De EU en andere publieke financiers zijn veel belangrijker.
    An array of responses to insect feeding in Brassica
    Broekgaarden, C. - \ 2009
    Gewasbescherming 40 (2009)2. - ISSN 0166-6495 - p. 67 - 70.
    dissertaties - koolsoorten - groenteteelt - brassica - insectenplagen - natuurlijke vijanden - insectenlokstoffen - verdedigingsmechanismen - vollegrondsgroenten - theses - cabbages - vegetable growing - brassica - insect pests - natural enemies - insect attractants - defence mechanisms - field vegetables
    De resultaten in dit proefschrift laten zien dat intra- en interspecifieke variatie tussen Brassicaplanten een sterk effect hebben op de groei van plantenetende insecten en op de transcriptiereacties van de plant na aanval door insecten, zowel in de kas als in het veld. Het combineren van onderzoek naar transcriptieprofielen van de plant en de groei van insecten, draagt bij aan het beter begrijpen van de interactie tussen Brassicaplanten en plantenetende insecten. Dit proefschrift vormt de basis voor het verder onderzoeken van directe verdedigingsmechanismen van witte kool
    Effect van "Ruimte voor Geo-informatie" op GIScience in Nederland : eindrapport RGI-402
    Veller, M.G.P. van; Fransen, H. ; Duizendstraal, M.B. ; Gerritsma, W. - \ 2009
    Wageningen : Bibliotheek Wageningen UR - 39
    geografische informatiesystemen - periodieken - dissertaties - evaluatie - prestatieniveau - bibliothecarisambt - wetenschap - geographical information systems - periodicals - theses - evaluation - performance - librarianship - science
    This report describes bibliometric analyses of the scientific output of GIScience in the Netherlands over the period 1999-2007. The bibliometric analyses have been based upon bibliographic data from articles published in 12 peer reviewed GIScience journals, articles in two professional journals and PhD theses which have been published at Dutch universities. Based upon these sources information is obtained for the publication output and citation impact of the Netherlands in an international context, the (inter)national co-operation of Dutch organizations with other organizations when publishing on geographic information systems in scientific literature and information on both scientific output in GIScience as well as related scientific disciplines for authors from the Netherlands. The bibliometric results obtained for GIScience are discussed in relation to science as a whole for the Netherlands.
    Gewaskeuze beïnvloedt insectendiversiteit
    Poelman, E.H. - \ 2009
    Gewasbescherming 40 (2009)1. - ISSN 0166-6495 - p. 9 - 11.
    gewasbescherming - verdedigingsmechanismen - biodiversiteit - brassica oleracea - roofinsecten - pieris rapae - plutella xylostella - mamestra brassicae - entomologie - dissertaties - insect-plant relaties - sluipwespen - plant protection - defence mechanisms - biodiversity - brassica oleracea - predatory insects - pieris rapae - plutella xylostella - mamestra brassicae - entomology - theses - insect plant relations - parasitoid wasps
    Op 1 oktober 2008 promoveerde Erik Poelman aan Wageningen Universiteit op het proefschrift getiteld ‘Linking variation in plant defence to biodiversity at higher trophic levels: a multidisciplinary approach’. Het doel van dit onderzoeksproject was om te bepalen wat het effect is van variatie in de directe, en indirecte verdediging binnen een plantensoort op de insectengemeenschap. Daarbij werd gebruik gemaakt van gecultiveerde witte kool (Brassica oleracea) en de insecten die daarop voorkomen. Beschreven worden de effecten van directe plantenverdediging op diversiteit van herbivoren, de effecten van indirecte verdediging op de levensgemeenschap van sluipwespen en de effecten van herbivorie op de diversiteit aan herbivoren
    Multispecies probiotics - composition and functionality
    Timmerman, H.M. - \ 2006
    Utrecht University. Promotor(en): A.C. Beynen; Frans Rombouts; L.M.A. Akkermans, co-promotor(en): G.T. Rijkers. - Utrecht : s.n. - ISBN 9789039341292 - 320
    probiotica - dissertaties - probiotics - theses
    Teat Condition in Dairy Cows
    Neijenhuis, F. - \ 2004
    Utrecht University. Promotor(en): J.P.T.M. Noordhuizen, co-promotor(en): Henk Hogeveen; H.W. Barkema. - - 193
    melkveehouderij - melkkoeien - uiers - spenen - mastitis - melken - diergezondheid - dissertaties - dairy farming - dairy cows - udders - weaning - mastitis - milking - animal health - theses
    The dairy cow's teat is the first line of defence against mastitis pathogens. The milking process may affect the teat's condition, increasing the risk of mastitis. It is well-proven that teat-ends with severe erosions or broken skin will have an increased risk of mastitis. However, more common changes in teat condition because of milking have not been related to udder health problems. The focus of this thesis was on the relationship between teat-end condition, machine milking and occurrence of mastitis. In this thesis, two types of changes of teat-end condition were distinguished: callosity rings around the orifice and machine-induced teat swelling. A classification system of the callosity rings around the orifice was defined: the teat-end callosity (TEC) classification system. In this system, a distinction is made between roughness of the callosity ring (TECR) and thickness of the callosity ring (TECT). The developed TEC classification system was used in a 1½ year longitudinal field study on 15 farms to examine the relationship between TEC and the incidence of clinical mastitis. Teats with a thin and smooth TEC ring showed the lowest incidence risk of clinical mastitis. To evaluate TEC in the field, a simplified 4-category scoring system is suggested and used in an observational study on 200 dairy farms. Variation in %ROUGH between farms is explained by cow factors such as teat-end shape and machine-on time and milking machine factors such as the liner and the vacuum. In order to measure machine-induced teat swelling, a methodology, using ultrasound, has been developed. Using this method, the changes of teat tissue in relation to machine milking and the recovery time of teat tissue after milking were evaluated. 8 h after milking, the teat-end width and the teat-canal length still differed from before milking. The teat-wall thickness and the teat-cistern width were recovered after 6 and 8 h. The overall conclusion of this thesis is that a healthy teat of a dairy cow has a good balance between the physiological reaction to machine milking and maintaining its first line of defence mechanism against invading mastitis pathogens. Increasing rates of IMI were related to one or more of the following: a high degree of machine-induced swelling, a high level of TECT, a high level of TECR and the absence of TEC. Pathways through which these machine-induced changes lowered the resistance of the teat to bacterial invasion are the openness of the teat canal, harbouring of pathogens in TEC, and significantly increased or decreased level of keratin regeneration rate. Part of the impaired reaction of the teat to machine milking may lay in the peak milkflow rate. Suggestions are made to adjust the characteristics of machine milking to the milk flow profile of an individual cow. This can minimise machine-induced teat condition problems. Teat condition changes can be used as an early warning signal for enhanced risk of clinical mastitis. Classification of teat condition is an essential tool in milking machine research and a useful monitoring tool of the quality of milking in the field. Protocols for systematic evaluation of teat condition are available
    Boekbesprekingen, Overzichtsartikel
    Frouws, J. - \ 2003
    Tijdschrift voor sociaalwetenschappelijk onderzoek van de landbouw 18 (2003). - ISSN 0921-481X - p. 233 - 242.
    natuurbescherming - waarden - taxatie - waardetheorie - dissertaties - overzichten - landschapsbescherming - landschapsecologie - ruimtelijke ordening - landgebruik - nature conservation - landscape conservation - landscape ecology - physical planning - land use - values - valuation - value theory - theses - reviews
    Bespreking en vergelijking van drie proefschriften. Het betreft achtereenvolgens: 1) J. Dekker. Dynamiek in de Nederlandse natuurbescherming. Universiteit Utrecht (2002) 2) M.D.T.M. de Jong. Scheidslijnen in het denken over natuurbeheer in Nederland. Technische Universiteit Delft (2002) 3) C.S.A. van Koppen. Echte natuur: een sociaaltheoretisch onderzoek naar natuurwaardering en natuurbescherming in de moderne samenleving. Wageningen Universiteit (2002). Het artikel wordt gevolgd door een gezamenlijke kanttekening van Van Koppen en Dekker
    Probabilistic segmentation of remotely sensed images
    Gorte, B. - \ 1998
    Agricultural University. Promotor(en): M. Molenaar; A. Stein. - Enschede : ITC - ISBN 9789061641575 - 143
    remote sensing - beeldverwerking - dissertaties - remote sensing - image processing - theses

    For information extraction from image data to create or update geographic information systems, objects are identified and labeled using an integration of segmentation and classification. This yields geometric and thematic information, respectively.

    Bayesian image classifiers calculate class posterior probabilities on the basis of estimated class probability densities and prior probabilities. This thesis presents refined probability estimates, which are local, i.e pertain to image regions, rather than to the entire image. Local class probability densities are estimated in a non-parametric way with an extended k-Nearest Neighbor method. Iterative estimation of class mixing proportions in arbitrary image regions yields local prior probabilities.

    The improved estimates of prior probabilities and probability densities increase the reliability of posterior probabilities and enhance subsequent decision making, such as maximum posterior probability class selection. Moreover, class areas are estimated more accurately, compared to standard Maximum Likelihood classification.

    Two sources of image regionalization are distinguished. Ancillary data in geographic information systems often divide the image area into regions with different class mixing proportions, in which probabilities are estimated. Otherwise, a regionalization can be obtained by image segmentation. A region based method is presented, being a generalization of connected component labeling in the quadtree domain. It recursively merges leaves in a quadtree representation of a multi-spectral image into segments with arbitrary shapes and sizes. Order dependency is avoided by applying the procedure iteratively with slowly relaxing homogeneity criteria.

    Region fragmentation and region merging, caused by spectral variation within objects and spectral similarity between adjacent objects, are avoided by regarding class homogeneity in addition to spectral homogeneity. As expected, most terrain objects correspond to image segments. These, however, reside at different levels in a segmentation pyramid. Therefore, class mixing proportions are estimated in all segments of such a pyramid to distinguish between pure and mixed ones. Pure segments are selected at the highest possible level, which may vary over the image. They form a non-overlapping set of labeled objects without fragmentation or merging. In image areas where classes cannot be separated, because of spatial or spectral resolution limitations, mixed segments are selected from the pyramid. They form uncertain objects, to which a mixture of classes with known proportion is assigned.

    Subsequently, remotely sensed data are used for taking decisions in geographical information systems. These decisions are usually based on crisp classifications and, therefore, influenced by classification errors and uncertainties. Moreover, when processing spatial data for decision making, the objectives and preferences of the decision maker are crucial to deal with. This thesis proposes to exploit mathematical decision analysis for integrating uncertainties and preferences, on the basis of carefully estimated probabilistic class information. It aims to solve complex decision problems on the basis of remotely sensed data.

    Characterization of the Buzura suppressaria single-nucleocapsid nucleopolyhedrovirus genome : a (phylo)genetic study
    Hu, Z. - \ 1998
    Agricultural University. Promotor(en): R.W. Goldbach; J.M. Vlak. - S.l. : Hu - ISBN 9789054859178 - 124
    kernpolyedervirussen - baculovirus - baculoviridae - insectenvirussen - biston - geometridae - genoomanalyse - fylogenie - dissertaties - biston suppressaria - nuclear polyhedrosis viruses - baculovirus - baculoviridae - insect viruses - biston - geometridae - genome analysis - phylogeny - theses - biston suppressaria

    Baculoviruses are attractive biological alternatives to chemical insecticides for insect pest control. So far, more than 600 baculoviruses have been isolated from different insect species which provide a rich resource for developing new viral insecticides. Most baculoviruses are host specific. Baculovirus nomenclature is based on the host from which the virus was first isolated and the taxonomy is based on the morphology of the occlusion body, polyhedra (nucleopolyhedroviruses = NPVs) or granula (granuloviruses = GVs). Until 1995, the NPVs had been further subdivided into single-nucleocapsid (S) and multiple-nucleocapsid (M) NPVs. Phylogeny studies based on the polyhedrin gene indicated that lepidopteran NPVs can be classified into two groups (I and II). Group II NPVs were found to encompass both SNPVs and MNPVs, whereas group I NPVs were composed of only MNPVs. Three Group I NPVs, Autographa californica (Ac) MNPV, Orgyia pseudotsugata (OpMNPV) and Bombyx mori (Bm) NPV, have been entirely sequenced and their genome organization was found to be very similar. Such detailed sequence information from other baculoviruses is scare particularly from SNPVs and GVs. The subject of this thesis is the Buzura suppressaria (Busu) NPV which was isolated from a Geometrid insect (tea moth) and has been used successfully as a bio-insecticide in China. Significant amount of sequencing was conducted on a genomic library of this virus which allowed us to conduct comparative investigations on the genome organization and phylogeny.

    First, the most conserved baculovirus gene, the polyhedrin gene, was identified by hybridization and then sequenced (Chapter 2). The location of the polyhedrin gene was used to set the zero point of the physical map of the viral genome. Phylogeny research based on the polyhedrin sequence placed BusuNPV into the Group II baculoviruses (see Chapter 8).

    Ecdysteroid UDP-glucosyltransferase (EGT) is an enzyme encoded by baculoviruses which delays larval molting and allows the virus to extend the production of large numbers of progeny virus. Deletion of the egt gene from the genome of baculoviruses results in an increased speed of kill and a reduced larval feeding activity and therefore enhances viral insecticidal activity. The strategy of deleting egt is now being adopted for the engineering of baculoviruses of economically important insect pests. In Chapter 3, the identification, sequencing and comparative analysis of the egt gene of BusuNPV is reported. This is the first egt gene characterized in a SNPV. Maximum parsimony analysis based on the amino acid sequence of baculoviruses EGTs confirmed that BusuNPV belongs to Group II baculoviruses.

    In order to study the genome organization of BusuNPV, a plasmid library covering the entire genome was constructed and the inserts were terminally or completely sequenced. In Chapter 4, the sequence analysis of the Hin dIII-J region (3.2 kb) of the BusuNPV genome revealed five ORFs ( pep , ORF117 , ctl , iap and sod ). The genomic arrangement of these ORFs in BusuNPV turned out to be significantly different from that of AcMNPV and other characterized baculoviruses. This indicates that BusuNPV may have a gene arrangement distinct from other baculoviruses identified so far.

    To further investigate the genomic organization and phylogenetic status of BusuNPV, a detailed physical map was constructed by extensive restriction enzyme analysis and Southern blot hybridization (Chapter 5). The size of the viral genome was estimated to be approximately 120.9 kb. About 43.5 kb of dispersed sequence information was generated from the plasmid library. Fifty-two ORFs, homologous to those of other baculoviruses, were identified and their location on the BusuNPV genome determined (Chapter 5). Although the gene content of BusuNPV, based on these 52 ORFs, is similar to that of AcMNPV, BmNPV and OpMNPV the arrangement is, however, significantly different from the latter, highly co-linear Group I NPVs. A new approach (GeneParityPlot) was developed to represent the differences in gene order among baculoviruses when limited sequence information is available. The method is useful to identify potential conserved gene clusters. The data obtained show that BusuNPV is a distinct baculovirus species and suggest that group II viruses may have a genome organization distinct from Group I viruses. It is concluded that the gene distribution along baculovirus genomes may be used as an independent parameter to study baculoviral phylogeny.

    Protein P10 is a major component of the fibrillar structures found in the cytoplasm and nucleus of infected insect cells. This small protein is involved in the release of polyhedra from infected cell-nuclei late in infection and plays a role in morphogenesis of the occlusion body. A putative p10 gene was identified for the first time in a SNPV (BusuNPV) based on its size and domain structures. Its function was determined in a 'swap assay' by using an AcMNPV p10 deletion mutant as an acceptor for the putative BusuNPV p10 gene (Chapter 6). The AcMNPV recombinant expressing the BusuNPV P10 formed fibrillar structures in the cytoplasm of Spodoptera frugiperda cells, but was unable to induce nuclear disintegration. This supports the current hypothesis that additional viral factors are required for this process.

    Polyhedrin is the major component of the occlusion body, which encapsulates the virions and protects them against physical and chemical decay. The gene swap assay was applied to investigate the specificity of the polyhedrin gene in the generation of occlusion bodies (Chapter 7). The BusuNPV polyhedrin gene expressed by AcMNPV resulted in the formation of normal occlusion bodies containing multiple-capsid virions. The occlusion bodies were as infective as normal AcMNPV suggesting that the occlusion process is not SNPV or MNPV specific. However, the recombinant AcMNPV expressing the polyhedrin gene of Spodoptera exigua (Se) MNPV, had an altered polyhedron morphology, pirmidal in shape, with few occluded virions. The infectivity was also lower than that of wild-type AcMNPV. These data suggest that the occlusion process is fine-tuned and may be dependent on one or more factors in addition to polyhedrin, that determine the size, shape and occlusion of virions.

    The genetic analysis compiled in this thesis shows that BusuNPV is a distinct baculovirus species. Alignment of various BusuNPV ORFs with baculovirus homologues and phylogenetic analyses indicated that SNPVs do not form a monophyletic group within the phylogenetic trees. The gene content of BusuNPV is very similar to that of AcMNPV, BmNPV and OpMNPV, suggesting that baculoviruses may have most of their genes in common. In addition to gene homology genome organization may also reflect the evolutionary history of baculoviruses. The molecular genetic studies of BusuNPV and their impact to future engineering of the virus for improved insecticidal activity are discussed (Chapter 8).

    Mapping genetic factors controlling potato - cyst nematode interactions
    Rouppe van der Voort, J.N.A.M. - \ 1998
    Agricultural University. Promotor(en): J. Bakker; F.J. Gommers. - S.l. : Rouppe van der Rouppe voort - ISBN 9789054858997 - 136
    plantenparasitaire nematoden - genkartering - heteroderidae - globodera - aardappelen - ziekteresistentie - dissertaties - plant parasitic nematodes - gene mapping - heteroderidae - globodera - potatoes - disease resistance - theses

    The thesis describes strategies for genetic mapping of the genomes of the potato cyst nematode and potato. Mapping in cyst nematodes was achieved by AFLP genotyping of single cysts and subsequent segregation analysis in a family of sibling populations. The genetic map of Globodera rostochiensis comprises nine linkage groups, a number similar to the haploid chromosome number determined. The low kb/cM ratio suggests that map based cloning of (a)virulence genes may be feasible for this organism.

    For potato, a mapping strategy based on catalogued, chromosome-specific AFLP markers facilitated the mapping of the nematode resistance loci Gpa2 and Grp1 . Gpa2 confers specific resistance to G. pallida and is tightly linked to a virus resistance on potato chromosome 12 . Locus Grp1 is identified by QTL mapping. It confers resistance to G. rostochiensis pathotype Ro 5 , partial resistance to G. pallida and maps on chromosome 5 . The spectra of nematode resistance loci and their positions on the potato genome suggest that these genes are involved in gene-for-gene interactions.

    Genetic and molecular analysis of the tomato root-knot nematode resistance locus Mi-1
    Liharska, T.B. - \ 1998
    Agricultural University. Promotor(en): A. van Kammen; M. Koornneef; W.J.T. Zabel. - S.l. : Liharska - ISBN 9789054858218 - 95
    genetische analyse - tomaten - solanum lycopersicum - weerstand - meloidogyne incognita - dissertaties - genetic analysis - tomatoes - solanum lycopersicum - resistance - meloidogyne incognita - theses

    Het doel van het onderzoek dat in dit proefschrift beschreven wordt, was de isolatie en karakterisering van het tomaat locus Mi-1, dat resistentie verleent tegen plantpathogene wortelknobbelaaltjes van het geslacht Meloidogyne, die schade veroorzaken bij een groot aantal gewassen. Resistentie van een plant tegen een ziekteverwekker houdt in dat de plant reageert op infectie met een afweerreactie, die verdere aantasting voorkomt. Bij het tot stand komen van de afweerreactie spelen de resistentiegenen een sleutelrol. Het leek zeer interessant om het Mi-1 locus te isoleren en te onderzoeken welk product door dit gen gecodeerd wordt. Op die manier kan inzicht verkregen worden in het mechanisme van de resistentie en de specificiteit van de interactie van wortelknobbelaaltjes en de gastheerplant. Bovendien zou dan onderzocht kunnen worden of overdracht van het Mi-1 gen naar gevoelige planten in die planten ook resistentie tegen wortelknobbellaaltjes bewerkstelligt.

    De isolatie van een gen vereist een goed gedefinieerde genetische kaart met een groot aantal moleculaire merkers zoals RFLP's, die nauw gekoppeld zijn aan het fenotype van het gen dat geïsoleerd moet worden. Voorts zijn genomische banken nodig met grote inserties, b.v. een YAC (Yeast Artificial Chromosome) bank, terwijl voor de functionele identificatie van gekloneerde genen via complementatie analyse, een efficiënte methode om planten te transformeren beschikbaar moet zijn. Aan het begin van het onderzoek waren de benodigde technieken voor de tomaat in principe beschikbaar en leek de weg geëffend te zijn om de isolatie van een resistentie gen zoals Mi-1 te ondernemen via positionele klonering.

    Het Mi-1 resistentie locus is afkomstig van de wilde tomatensoort Lycopersicon peruvianum en is in de cultuurtomaat L. esculentum ingekruist. Het komt nu voor als een introgressie in verschillende nematode resistente lijnen van L. esculentum. In hoofdstuk 1 wordt beschreven welke fenotypische eigenschappen het Mi-1 locus aan tomatenplanten geef[ en wordt het voorkomen van andere genen voor resistentie tegen wortelknobbelaaltjes in Lycopersicon soorten besproken. In dit hoofdstuk wordt ook kort weergegeven wat, bij het begin van het onderzoek, de stand van zaken was van de moleculaire genetica van het Mi-1 locus, die de basis moet vormen voor de positionele klonering van Mi-1.

    Het Mi-1 locus ligt op de korte arm van chromosoom 6 van de tomaat. Om kloneren mogelijk te maken is het noodzakelijk om een zo klein mogelijk gebied van het chromosoom af te bakenen waarop het Mi-1 locus ligt en zoveel mogelijk fenotypische en moleculaire merkers in dit gebied in kaart te brengen. Daartoe werden een groot aantal recombinanten geanalyseerd. Het bleek dat de recombinatie van L. esculentum in het introgressiegebied met hetMi- locus sterk onderdrukt was. Die onderdrukking bleek het gevolg te zijn van de soortvreemde afkomst van het chromosomale DNA met het Mi- locus. HetMi- locusligt bovendien dichtbij het centromeer van chromosoom 6 en die positie kan extra bijdragen aan de onderdrukking van de recombinatie in het gebied dat in kaart gebracht moest worden. Daardoor was het niet mogelijk om het gebied waarinMiligt nauwkeurig af te bakenen (hoofdstuk 2).

    Als een alternatieve methode om recombinanten in kaart te brengen zijn straling-geïnduceerde deletiemutanten gebruikt om te proberen met behulp daarvan een verfijnde kaart van moleculaire merkers van het Mi -gebied te verkrijgen (hoofdstuk 3). Hoewel de verkregen deletiemutanten bruikbaar waren om het niet-recombineerbare gebied rond het centromeer van chromosoom 6 in kaart te brengen, verschafte deze aanpak toch niet de verwachte en vereiste precisering van de genetische kaart. Dit werd veroorzaakt door de niet-willekeurige distributie van de deletiebreekpunten en het feit dat vooral grote terminale deleties werden verkregen.

    In hoofdstuk 4 wordt vervolgens beschreven hoe twee elkaar aanvullende strategieën zijn gebruikt om meer recombinanten in het Mi-gebied te identificeren en in kaart te brengen. Die aanpak bestond aan de ene kant uit een uitbreiding van het onderzoek naar recombinanten, waarvan in hoofdstuk 2 verslag is gedaan, met op PCR gebaseerde merkers en AFLP merkers rond deMi- locus in L. esculentum. De andere strategie bestond uit het genereren en analyseren van een segregerende populatie van de wilde tomaat L. peruvianum , waaruit hetMi -locus afkomstig is. Met PCR-merkers lukte het om in die populatie recombinanten te identificeren met kruisingen dicht bijMi.

    Op die manier kon hetMi-1locusbegrensd worden tot een gebied van het genoom van minder dan 65 kb. Daarmee was de weg vrijgemaakt omMi-1te identificeren in klonen van YAC banken en in cosmid klonen.

    Vervolgens werd het tomatengenotype L.esculentum 0T745 bestudeerd dat spontaan hetMi-1 locus had verloren en tegelijkertijd ook resistentie tegen aardappelluizen (Macrosiphum euphorbiae) was kwijtgeraakt (hoofdstuk 5). De genetische en moleculaire gegevens wezen op de aanwezigheid van een mutatie (lmml) in het 0T745 genotype, gelocaliseerd binnen de introgressie met Mi-1, die gepaard gaat met een hypergemethyleerde Clal herkenningsequentie buiten de gebieden van deMi-1en Meul genen.

    In hoofdstuk 6 wordt besproken welke vooruitgang is geboekt met de gebruikte genetische aanpak bij het bestuderen van het Mi-1 locus en welke betekenis dit onderzoek is geweest voor de recente vorderingen met de klonering vanMi-I.Het onderzoek weerspiegelt de snelle ontwikkeling van de moleculaire genetische technologie voor de identificatie en karakterisering van genen in planten.

    Aspects of resistance of flax and linseed (Linum usitatissimum) to Fusarium oxysporum f.sp. lini = Aspecten van de resistentie in vezel- en olievlas (Linum usitatissimum) tegen Fusarium oxysporum f.sp. lini
    Kroes, I. - \ 1997
    Agricultural University. Promotor(en): J.E. Parlevliet; W. Lange. - S.l. : Kroes - ISBN 9789054857839 - 159
    linum usitatissimum - vlas - lijnzaad - plantenziekteverwekkende schimmels - fusarium - ziekteresistentie - plantenveredeling - dissertaties - tuberculariaceae - linum usitatissimum - flax - linseed - plant pathogenic fungi - fusarium - disease resistance - plant breeding - theses - tuberculariaceae
    In the thesis aspects have been described of the flax and linseed interaction to Fusarium oxysporum f.sp. lini, the causal agent of flax wilt. Two in vitro tests were established to screen for resistance, to investigate race specificity and to study infection and colonization patterns in a resistant and a susceptible cultivar. The fungus appeared to colonize the cortex, causing root rot initially, followed by colonization of the protoxylem vessels. Several aspects of quantitative screening for resistance were investigated by visual disease screening, physiologic parameters, and ergosterol measurements. The results indicated that symptoms are related to resistance rather than tolerance. Race specificity was studied in vitro, and in an international field experiment performed at six locations in Europe and three in North America. Although significant genotype * isolate interaction and significant genotype * environment interaction was observed, possible races of the fungus could not be identified. No indication was obtained for race-specific resistance in flax and linseed.
    Interaction between root-knot nematodes and Solanum spp. : variation in pathogenicity, cytology, proteins and DNA = [De interactie tussen wortelknobbelnematoden en Solanum spp. : variatie in ziekteverwekkend vermogen, cytologie, eiwitten en DNA]
    Beek, J.G. van der - \ 1997
    Agricultural University. Promotor(en): R.F. Hoekstra; C.H. van Silfhout; P.W.T. Maas. - S.l. : Van der Beek - ISBN 9789054857280 - 219
    wortelknolletjes - knobbelvorming - plantenparasitaire nematoden - meloidogyne - plantenplagen - solanaceae - pathogeniteit - genetische variatie - cytologie - eiwitten - dna - plantennematologie - gastheer parasiet relaties - dissertaties - root nodules - nodulation - plant parasitic nematodes - meloidogyne - plant pests - solanaceae - pathogenicity - genetic variation - cytology - proteins - dna - plant nematology - host parasite relationships - theses

    This thesis describes genetic variation in the root-knot nematodes Meloidogyne hapla, M. chitwoodi and M. fallax, particularly with respect to their pathogenicity on Solanum spp. Significant differences in virulence and aggressiveness were shown to exist between and within these species. Evidence for the occurrence of pathotypes of M. chitwoodi on S. bulbocastanum was obtained. Differences in virulence corresponded to differences in overall genetic variation, revealed by 2-D protein electrophoresis. A distinct species classification for Meloidogyne spp. was obtained by AFLPs and 2-D electrophoresis. In mating experiments M.chitwoodi and M. fallax appeared to be true biological species as testified by infertility of their hybrids. Abnormalities during meiosis in oocytes of an isolate of M. hapla and in spermatocytes of isolates of M. fallax resulted in limited sexual recombination. The combination of post-reductional meiosis and the fusion of the second polar body with the egg pronucleus is probably responsable for maintenance of heterozygosity in meiotic parthenogenetic Meloidogyne. The constant production of males in these populations makes the development of homogeneous isolates impossible. A method was described to conserve nematode germplasm by long-term preservation of juveniles in liquid nitrogen.
    Evaluation of techniques to collect ileal digesta in pigs
    Koehler, T. - \ 1992
    Agricultural University. Promotor(en): M.W.A. Verstegen, co-promotor(en): H.R. Mosenthin; L.A. den Hartog. - S.l. : Koehler - 135
    varkens - spijsvertering - laboratoria - experimenten - dissertaties - pigs - digestion - laboratories - experiments - theses

    The results of some comparative experiments using different digesta collection techniques are presented. Physiological parameters such as growth performance, nitrogen and mineral balances and various blood variables were studied in pigs fitted with post-valve T-caecum (PVTC) cannulas and end-to-side ileo-rectal anastomosis (IRA). Digestibility measurements using different techniques (PVTC, IRA, simple T-cannula and re-entrant cannula) and different diets independently were carried out. Considerable effects of IRA on the physiological status of the animals were found. Digesta composition in IRApigs was in some aspects significant different from that in PVTC-pigs. This indicates an increased fermentative activity in IRA-pigs as well as some adaptative changes in mineral absorption as a result of the absence of hind-gut absorption. Differences in digestibility measurements between different cannulation techniques were small provided that the results were calculated on the basis of marker recoveries. The effect of a sugar/starch supplementation to the diet to compensate for the absence of the hind-gut functions in IRA-pigs was studied in PVTC-pigs. There was no effect on the apparent ileal digestibility of amino acids feeding a wheat based diet. The consequences of the different effects assosiated with the different techniques for digestibility measurements are discussed.

    Dissertation abstracts of the Agricultural University, Wageningen, The Netherlands 1918-1968
    Maltha, D.J. ; Eernstman, T. - \ 1968
    Wageningen : Veenman (Miscellaneous papers / Landbouwhogeschool 1) - 349
    landbouw - hogere agrarische scholen - universiteiten - dissertaties - bibliografieën - nederland - veluwe - gelderland - examens - agriculture - agricultural colleges - universities - theses - bibliographies - netherlands - veluwe - gelderland - examinations
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