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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    Exploring the resistance against root parasitic plants in Arabidopsis and tomato
    Cheng, Xi - \ 2017
    Wageningen University. Promotor(en): H.J. Bouwmeester, co-promotor(en): C.P. Ruyter-Spira. - Wageningen : Wageningen University - ISBN 9789463437004 - 305
    plants - parasitic plants - arabidopsis thaliana - solanum lycopersicum - host parasite relationships - plant growth regulators - resistance - planten - parasitaire planten - arabidopsis thaliana - solanum lycopersicum - gastheer parasiet relaties - plantengroeiregulatoren - weerstand
    Root parasitic plant species such as broomrapes (Orobanche and Phelipanche spp.) and witchweeds (Striga spp.) are notorious agricultural weeds. They cause damage to crops by depriving them of water, nutrients and assimilates via a vascular connection. The difficulty in controlling root parasitic weeds is largely due to their intricate lifecycle and partially underground lifestyle. Their life cycle includes processes such as germination of the seed, the formation of the vascular connection with the host, the growth and development of the parasite after attachment and the emergence of shoots and flowers aboveground. The germination of many parasitic plants is induced by strigolactones that were recently shown to also be signalling compounds that stimulate mycorrhizal symbiosis. In addition, in the past few years, their role in plant development and plant defense has been established revealing them as a new class of plant hormones that exert their function likely in interaction with other hormones.
    'Alerte plant kan een aanval van schimmels weerstaan' : onderzoek naar invloed rood licht op weerbaarheid
    Hofland-Zijlstra, Jantineke - \ 2016
    fungi - fungus control - resistance - red light - agricultural research - greenhouse horticulture - plant pests - plants - immune system
    On the evolution of azole resistance in Aspergillus fumigatus
    Zhang, J. - \ 2016
    Wageningen University. Promotor(en): Bas Zwaan; P.E. Verweij, co-promotor(en): Fons Debets; Sijmen Schoustra. - Wageningen : Wageningen University - ISBN 9789462578555 - 183
    aspergillus fumigatus - azoles - triazoles - aspergillosis - resistance - life cycle - asexual reproduction - sexual reproduction - experimental evolution - evolutionary genetics - agriculture - composting - medicine - aspergillus fumigatus - azolen - triazolen - aspergillose - weerstand - levenscyclus - ongeslachtelijke voortplanting - geslachtelijke voortplanting - experimentele evolutie - evolutionaire genetica - landbouw - compostering - geneeskunde

    During the last decade azole resistance has increasingly been reported in Aspergillus fumigatus, which is a fungal pathogen involved in the vast majority of invasive aspergillosis infections in humans, and is now a global public health concern. Antifungal azoles, especially triazoles, are the drugs of choice for medical treatment. However, this treatment is hampered by the emergence of multi-azole resistant A. fumigatus isolates, especially the highly resistant variants TR34/L98H and TR46 /Y121F/T289A. Therefore, to control this disease, it is essential to elucidate by what mechanisms resistance emerges, how resistance spreads and how resistant genotypes persist in environments without azoles. The presented thesis shows the relevance of the life cycle of A. fumigatus to the development of azole resistance and possible evolutionary routes that lead to it. The work highlights the importance of fungal biology and evolution towards understanding the development of azole resistance in fungi. We conclude that azole resistance in A. fumigatus is a consequence of selection pressure by azole in the environment on the genetic variation generated via various aspects in the A. fumigatus life cycle. This thesis also introduces an experimental evolution approach to study the dynamics and mechanisms of the evolution of azole resistance. In addition, we investigate what condition can lead an environment to be a possible hotspot for the development of resistance. Finally, we link this to the potential conditions under which resistance can emerge and spread in the lungs of humans and how this depends on the specific azole used.

    Quantitative and ecological aspects of Listeria monocytogenes population heterogeneity
    Metselaar, K.I. - \ 2016
    Wageningen University. Promotor(en): Marcel Zwietering; Tjakko Abee, co-promotor(en): Heidy den Besten. - Wageningen : Wageningen University - ISBN 9789462577664 - 173
    listeria - listeria monocytogenes - stress - stress tolerance - ribosomes - proteins - lactobacillus plantarum - behaviour - ecological assessment - genome analysis - dna sequencing - resistance - heterogeneity - listeria - listeria monocytogenes - stress - stresstolerantie - ribosomen - eiwitten - lactobacillus plantarum - gedrag - ecologische beoordeling - genoomanalyse - dna-sequencing - weerstand - heterogeniteit

    Bacterial stress response and heterogeneity therein is one of the biggest challenges posed by minimal processing. Heterogeneity and resulting tailing representing a more resistant fraction of the population, can have several causes and can be transient or stably in nature. Stable increased stress resistance is caused by alterations in the genome and therefore inheritable and is referred to as stable stress resistant variants. Also L. monocytogenes exhibits a heterogeneous response upon stress exposure which can be partially attributed to the presence of stable stress resistant variants. Adverse environments were shown to select for stable stress resistant variants. The objective of the research described in this thesis was to evaluate if L. monocytogenes population diversity and the presence of stable resistant variants is a general phenomenon that is observed upon different types of stress exposure, to get more insight in the mechanisms leading to increased resistance and to evaluate the ecological behaviour and potential impact on food safety of these stable resistant variants. Acid stress was chosen as it is an important hurdle both in food preservation, as well as in stomach survival.

    First, the non-linear inactivation kinetics of L. monocytogenes upon acid exposure were quantitatively described. A commonly used biphasic inactivation model was reparameterized, which improved the statistical performance of the model and resulted in more accurate estimation of the resistant fraction within L. monocytogenes WT populations. The observed tailing suggested that stable stress resistant variants might also be found upon acid exposure. Indeed, 23 stable acid resistant variants of L. monocytogenes LO28 were isolated from the tail after exposure of late-exponential phase cells to pH 3.5 for 90 min, with different degrees of acid resistance amongst them. Increased acid resistance showed to be significantly correlated to reduced growth rate. Studying the growth boundaries of the WT and a representative set of variants indicated that the increased resistance of the variants was only related to survival of severe pH stress but did not allow for better growth or survival at mild pH stress.
    A set of variants were further characterized phenotypically and cluster analysis was performed. This resulted in three clusters and four individual variants and revealed multiple-stress resistance, with both unique and overlapping features related to stress resistance, growth, motility, biofilm formation and virulence indicators. A higher glutamate decarboxylase (GAD) activity correlated with increased acid resistance. Whole genome sequencing of a set of variants was performed and revealed mutations in rpsU, encoding ribosomal protein S21. This rpsU mutation was found in all 11 variants comprising the largest phenotypic cluster, indicating a potential role of this ribosomal protein in stress resistance. Mutations in ctsR, which were previously shown to be responsible for increased resistance of heat and HHP resistant variants, were not found in the acid resistant variants. This underlined that large population diversity exists within one L. monocytogenes strain and that different adverse conditions drive selection for different variants.

    Next, the performance in mixed species biofilms with Lactobacillus plantarum was evaluated, as well as their benzalkonium chloride (BAC) resistance in these biofilms. It was hypothesized that the acid resistant variants might also show better survival in biofilms with L. plantarum, which provide an acidic environment by lactose fermentation with pH values below the growth boundary of L. monocytogenes when biofilms mature. L. monocytogenes LO28 WT and eight acid resistant variants were capable of forming mixed biofilms with L. plantarum at 20°C and 30°C in BHI supplemented with manganese and glucose. Some of the variants were able to withstand the low pH in the mixed biofilms for a longer time than the WT and there were clear differences in survival between the variants which could not be correlated to (lactic) acid resistance alone. Adaptation to mild pH of liquid cultures during growth to stationary phase increased the acid resistance of some variants to a greater extent than of others, which could be correlated to increased survival in the mixed biofilms. There were no clear differences in BAC resistance between the wild type and variants in mixed biofilms.

    Lastly, a set of robustness and fitness parameters of WT and variants was obtained and used to model their growth behaviour under combined mild stress conditions and to model their performance in a simulated food chain. This gave more insight in the trade-off between increased stress resistance and growth capacity. Predictions of performance were validated in single and mixed cultures by plate counts and by qPCR in which WT and an rpsU deletion variant were distinguished by specific primers. Growth predictions for WT and rpsU deletion variant were matching the experimental data generally well. Globally, the variants are more robust than the WT but the WT grows faster than most variants. Validation of performance in a simulated food chain consisting of subsequent growth and inactivation steps, confirmed the trend of higher growth fitness and lower stress robustness for the WT compared to the rpsU variant. This quantitative data set provides insights into the conditions which can select for stress resistant variants in industrial settings and their potential persistence in food processing environments.

    In conclusion, the work presented in this thesis highlights the population diversity of L. monocytogenes and the impact of environmental conditions on the population composition, which is of great importance for minimal processing. The work of this thesis resulted in more insight in the mechanisms underlying increased resistance of stress resistant variants and quantitative data on the behaviour of stress resistant variants which can be implemented in predictive microbiology and quantitative risk assessments aiming at finding the balance between food safety and food quality.

    Resistentieveredeling - Verdedigingsmechanisme : Kennisclip Bogo-project e-learning
    Hop, M.E.C.M. - \ 2016
    Groen Kennisnet
    resistance breeding - susceptibility - resistance - tolerance - host pathogen interactions - plant protection - teaching materials - disease resistance - resistentieveredeling - vatbaarheid - weerstand - tolerantie - gastheer-pathogeen interacties - gewasbescherming - lesmaterialen - ziekteresistentie
    Deze kennisclip maakt onderdeel uit van de lesmodule Resistentie Veredeling van het CIV T&U.
    Resistance identification and rational process design in Capacitive Deionization
    Dykstra, Jouke ; Zhao, R. ; Biesheuvel, P.M. ; Wal, A. van der - \ 2016
    Water Research 88 (2016). - ISSN 0043-1354 - p. 358 - 370.
    ionentransport - weerstand - waterzuivering - ontzilting - elektrodes - ionenuitwisseling - specifieke ionenelektrodes - ion transport - resistance - water treatment - desalination - electrodes - ion exchange - specific ion electrodes
    Capacitive Deionization (CDI) is an electrochemical method for water desalination employing porous carbon electrodes. To enhance the performance of CDI, identification of electronic and ionic resistances in the CDI cell is important. In this work, we outline a method to identify these resistances. We illustrate our method by calculating the resistances in a CDI cell with membranes (MCDI) and by using this knowledge to improve the cell design. To identify the resistances, we derive a full-scale MCDI model. This model is validated against experimental data and used to calculate the ionic resistances across the MCDI cell. We present a novel way to measure the electronic resistances in a CDI cell, as well as the spacer channel thickness and porosity after assembly of the MCDI cell. We identify that for inflow salt concentrations of 20 mM the resistance is mainly located in the spacer channel and the external electrical circuit, not in the electrodes. Based on these findings, we show that the carbon electrode thickness can be increased without significantly increasing the energy consumption per mol salt removed, which has the advantage that the desalination time can be lengthened significantly.
    Invasieve soorten Waddenzee: : Ecosysteem resistentie en de Filipijnse tapijtschelp
    Sneekes, A.C. ; Mendez Merino, Natalia ; Weide, B.E. van der; Glorius, S.T. ; Tamis, J.E. - \ 2015
    Den Helder : IMARES (Rapport / IMARES C175/15) - 67
    invasieve soorten - schaaldieren - veevervoer - weerstand - aquatische ecosystemen - milieueffect - waddenzee - nederland - invasive species - shellfish - transport of animals - resistance - aquatic ecosystems - environmental impact - wadden sea - netherlands
    Jaarverslagen van de KNPV-werkgroepen over 2014: Werkgroep Bodempathogenen en bodemmicrobiologie
    Os, G.J. van; Postma, J. - \ 2015
    Gewasbescherming 46 (2015)2. - ISSN 0166-6495 - p. 46 - 46.
    jaarverslagen - werkgroepen - gewasbescherming - bodempathogenen - bodemmicrobiologie - fusarium - oömyceten - onkruidkunde - nematoda - pathogenen - resistentie tegen insecticiden - resistentie tegen herbiciden - weerstand - bacteriologie - graansoorten - annual reports - working groups - plant protection - soilborne pathogens - soil microbiology - fusarium - oomycetes - weed science - nematoda - pathogens - insecticide resistance - herbicide resistance - resistance - bacteriology - cereals
    Dit artikel omvat de jaarverslagen van de volgende KNPV-werkgroepen over 2014: Bodempathogenen en bodemmicrobiologie; Fusarium; Oömyceten; Nematoden; Onkruidbeheersing; Middelenresistentie; Fytobacteriologie; Gewasbescherming en Maatschappelijk Debat; Jongeren; Fytobacteriologie; Graanziekten.
    Inzicht door het 'videotracken' van insecten
    Jongsma, M.A. - \ 2014
    pest resistance - varietal resistance - resistance - resistance breeding - plant breeding - insects - insect pests - monitoring - agricultural research - methodology - video cameras

    UITGELICHT GEZOND & WEERBAAR - Maarten Jongsma is senior onderzoeker en werkt bij Plant Research International (PRI), onderdeel van Wageningen Universiteit en Research Centrum. Hij is moleculair bioloog en is gepromoveerd op ‘plant-insectrelaties’. Hij weet veel over hoe planten zich weerbaar maken tegen plagen zoals trips, bladluis en witte vlieg. “Wij bedenken innovatieve tools voor veredelaars om snel resistentie-eigenschappen te vinden.”

    Virus onschadelijk maken, voorkomen infectie, symptomen onderdrukken : beheersen door complex van middelen en maatregelen
    Arkesteijn, M. ; Stijger, I. - \ 2014
    Onder Glas 11 (2014)12. - p. 62 - 63.
    glastuinbouw - kasgewassen - plantenvirussen - gewasbescherming - maatregelen - landbouwkundig onderzoek - weerstand - ziektepreventie - virusziekten - greenhouse horticulture - greenhouse crops - plant viruses - plant protection - measures - agricultural research - resistance - disease prevention - viral diseases
    Virussen veroorzaken behoorlijk wat economische schade in cultuurgewassen. Een besmetting met komkommerbontvirus bijvoorbeeld levert al gauw 15% inkomstenderving op. Virusziekten zijn niet te bestrijden zoals schimmels en bacteriën, maar wel te beheersen. Virologe Ineke Stijger van Wageningen UR Glastuinbouw vertelt over de mogelijke wijzen van aanpak en het huidige onderzoek.
    VDI-1 Effect van maternale voedingsinterventies op de immuun competentie van de nakomelingen
    Krimpen, Marinus van - \ 2014
    animal nutrition - young animals - human feeding - resistance - immune system - maternal nutrition - colostrum - maternal immunity - literature reviews
    Weerbaarheid in innovatieve kasteelten
    Wurff, Andre van der - \ 2013
    greenhouses - greenhouse horticulture - ornamental horticulture - cultural methods - substrates - plant protection - biological control agents - resistance - sustainability - innovations - disease prevention
    Bodybuilders met schubben (interview met A. Palstra)
    Palstra, A.P. - \ 2013
    Visionair : het vakblad van sportvisserij Nederland (2013)28. - ISSN 1569-7533 - p. 4 - 7.
    vissen - danio rerio - europese zalm - zwemmen - dierfysiologie - weerstand - stress - kweekvis - fishes - danio rerio - atlantic salmon - swimming - animal physiology - resistance - stress - farmed fish
    Een getrainde vis is een fitte vis, kan een adagium worden in het visonderzoek. Want vissen die genoeg zwemmen groeien harder, zijn minder stressgevoelig en beter bestand tegen ziekten. Hoe dat precies werkt wordt langzaam duidelijk.
    Thermoregulatie bij honingbijen : hoe houd ik mijn huis warm in de winter?
    Langevelde, Frank van - \ 2013
    honey bees - winter - temperature - resistance - stress - animal diseases - pesticides - food deprivation - varroa - adverse effects
    Hormonen vaak betrokken bij versterking eigen afweer van planten : veel ontwikkelingen bij plantenhormonen
    Heuvelink, E. ; Kierkels, T. - \ 2013
    Onder Glas 10 (2013)1. - p. 13 - 15.
    glastuinbouw - potplanten - groeifactoren - hormonen - verdedigingsmechanismen - plantengroeiregulatoren - weerstand - landbouwkundig onderzoek - gewasbescherming - greenhouse horticulture - pot plants - growth factors - hormones - defence mechanisms - plant growth regulators - resistance - agricultural research - plant protection
    Vroeger was het simpel: er zijn vijf groepen plantenhormonen en dat is het. Maar het ligt veel ingewikkelder. Naarmate het inzicht groeit, wordt de lijst van hormonen langer. Opvallend veel daarvan zijn betrokken bij weerstand tegen stress, ziekten en plagen. Daar kan de tuinbouw in de toekomst wellicht voordeel bij hebben.
    Rood licht houdt defensie tomaat paraat
    Hofland-Zijlstra, J.D. - \ 2013
    Kennis Online 10 (2013)jan/febr. - p. 10 - 10.
    groenteteelt - tomaten - schimmelziekten - bestrijdingsmethoden - rood licht - weerstand - schimmelbestrijding - landbouwkundig onderzoek - vegetable growing - tomatoes - fungal diseases - control methods - red light - resistance - fungus control - agricultural research
    Een flinke dosis rood licht maakt tomaten beter bestand tegen schimmels. Onderzoekers van Wageningen UR Glastuinbouw en Plant Research International lieten zien dat meeldauw minder kans maakt in een kas die ’s nachts een bad rood licht krijgt. Hoe het licht de tomatendefensie opkrikt is nog niet duidelijk.
    Toepassing van elicitors ter verhoging van de plantweerstand
    Derkx, M.P.M. ; Doorn, J. van; Wolf, J.M. van der - \ 2012
    Lisse : Praktijkonderzoek Plant & Omgeving B.V. - 44
    gewasbescherming - plantenziekten - ziekteresistentie - weerstand - resistentiemechanismen - toepassing - toepassingsdatum - efficiëntie - schimmels - bacteriën - plantenziektebestrijding - plant protection - plant diseases - disease resistance - resistance - resistance mechanisms - application - application date - efficiency - fungi - bacteria - plant disease control
    PPO Projectnummer: 3236144000 PT projectnummer: 14443
    Verdeling van oxytetraxycline (afkomstig van versleping) in diervoeders
    Stolker, A.A.M. ; Zuidema, T. ; Egmond, H.J. van; Jong, J. de; Haelermans, P.J.M. ; Hooglugt, J.H. - \ 2012
    Wageningen : RIKILT Wageningen UR (Rapport / RIKILT 2012.003) - 32
    antibiotica - antibioticumresiduen - diervoedering - weerstand - besmetting - oxytetracycline - antibiotics - antibiotic residues - animal feeding - resistance - contamination - oxytetracycline
    De laatste jaren is er een toenemende aandacht voor de mogelijke bijdrage van therapeutisch gebruik van antibiotica in de dierhouderij op de ontwikkeling van antimicrobiële resistentie. Een additionele bron van blootstelling van landbouwhuisdieren aan antibiotica is versleping via diervoeders. In principe levert iedere partij gemedicineerd voeder, meerdere spoelcharges op met residuen van antibiotica. Landbouwhuisdieren worden door dit 'door versleping' gecontamineerde voer onbedoeld blootgesteld aan antibiotica.
    Abscisinezuur speelt rol bij resistentie tegen stress-omstandigheden : je kunt de plant ook te veel 'pamperen'
    Heuvelink, E. ; Kierkels, T. - \ 2012
    Onder Glas 9 (2012)11. - p. 26 - 27.
    glastuinbouw - plantenziekten - abscisinezuur - hormonen - resistentiemechanismen - cultuurmethoden - plaagresistentie - weerstand - greenhouse horticulture - plant diseases - abscisic acid - hormones - resistance mechanisms - cultural methods - pest resistance - resistance
    Abscisinezuur zorgt ervoor dat planten ongunstige omstandigheden kunnen overleven. In de kas proberen we zulke situaties juist te vermijden. Maar je kunt de plant ook te veel ‘pamperen’. Dat kan leiden tot een ongevoeligheid voor dit ‘stress-hormoon’ die zich later wreekt.
    Onderzoek naar effecten van plantversterkende preparaten
    Staalduinen, J. van; Wurff, A.W.G. van der - \ 2012
    Onder Glas 9 (2012)10. - p. 72 - 73.
    glastuinbouw - groenten - snijbloemen - substraten - cultuurmethoden - ziektebestrijdende teeltmaatregelen - weerstand - methodologie - wortels - greenhouse horticulture - vegetables - cut flowers - substrates - cultural methods - cultural control - resistance - methodology - roots
    Een groeiend aantal substraattelers gebruikt middelen die het wortelmilieu zouden vitaliseren en gewassen weerbaarder maken. Hoewel zij er baat bij zeggen te hebben, is niet altijd duidelijk wat deze middelen precies doen en hoe men de teelt er gericht mee kan sturen. Het vierjarige project ‘Weerbaar substraat’ moet daar verandering in brengen.
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