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.

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The fish egg microbiome : diversity and activity against the oomycete pathogen Saprolegnia
Liu, Y. - \ 2016
Wageningen University. Promotor(en): Francine Govers; Jos Raaijmakers, co-promotor(en): Irene de Bruijn. - Wageningen : Wageningen University - ISBN 9789462577671 - 169 p.
salmon - fish eggs - marine microorganisms - microbial diversity - bioinformatics - genomics - saprolegnia - oomycota - fish diseases - suppression - fungal antagonists - zalm - visseneieren - mariene micro-organismen - microbiële diversiteit - bio-informatica - genomica - oömycota - visziekten - onderdrukking - schimmelantagonisten

Y. Liu

Prof. dr. F. Govers (promotor); Prof. dr. J.M. Raaijmakers (promotor); Dr. I. de Bruijn (co-promotor); Wageningen University, 13 June 2016, 170 pp.

The fish egg microbiome: diversity and activity against the oomycete pathogen Saprolegnia

Emerging oomycete pathogens increasingly threaten biodiversity and food security. This thesis describes the study of the microbiome of Atlantic salmon (Salmo salar L.) eggs and analyses of the effects of infections by the oomycete pathogen Saprolegnia on the microbial architecture. A low incidence of Saprolegniosis was correlated with a relatively high abundance and richness of specific commensal Actinobacteria. Among the bacterial community, the isolates Frondihabitans sp. 762G35 (Microbacteriaceae) and Pseudomonas sp. H6 significantly inhibited hyphal attachment of Saprolegnia diclina to live salmon eggs. Chemical profiling showed that these two isolates produce furancarboxylic acid-derived metabolites and a lipopeptide viscosin-like biosurfactant, respectively, which inhibited hyphal growth of S. diclina in vitro. Among the fungal community, the fungal isolates obtained from salmon eggs were closely related to Microdochium lycopodinum/Microdochium phragmitis and Trichoderma viride. Both a quantitative and qualitative difference in the Trichoderma population between Saprolegnia-infected and healthy salmon eggs was observed, which suggested that mycoparasitic Trichoderma species could play a role in Saprolegnia suppression in aquaculture. This research provides a scientific framework for studying the diversity and dynamics of microbial communities to mitigate emerging diseases. The Frondihabitans, Pseudomonas and Trichoderma isolates, and/or their bioactive metabolites, are proposed as effective candidates to control Saprolegniosis.

Analysis of microbial taxonomical groups present in maize stalks suppressive to colonization by toxigenic Fusarium spp.: A strategy for the identification of potential antagonists
Köhl, J. ; Lombaers-van der Plas, C.H. ; Moretti, A. ; Bandyopadhyay, R. ; Somma, S. ; Kastelein, P. - \ 2015
Biological Control 83 (2015). - ISSN 1049-9644 - p. 20 - 28.
biological-control - rhizosphere microbiome - quantitative detection - microdochium-bolleyi - acremonium-strictum - fungal antagonists - idriella-bolleyi - seed treatment - head blight - durum-wheat
Pink ear rot of maize caused by Fusarium verticillioides, Fusariumproliferatum and Fusariumgraminearumcan lead to severe yield losses and contamination of grain with a range of mycotoxins. Maize stalks colonized by Fusarium spp. are the main primary inoculum source for Fusarium incited epidemics in maize or other susceptible crops grown in rotation. The colonization of individual maize stalks originating from fields in The Netherlands, Italy and Nigeria byFusarium spp. was quantified using specific TaqMan-PCR assays. Highest values were found for F. graminearum and Fusariumavenaceum in Dutch samples, for F. graminearum and FUM producing species (F. verticillioides and F. proliferatum) in Italian samples and FUM producing Fusarium spp. in Nigerian samples. The increase in Fusarium spp. colonization under field conditions during a period of 3–6 months after harvest of the maize crops varied considerably between individual stalks. The fungal and bacterial diversity was analyzed for sub-sets of stalks with high versus low increase of Fusariumcolonization. Bacterial taxonomic groups such as Bacillus, Curtobacterium, Erwinia, Flavobacterium,Novosphingobium, Pantoea, Sphingomonas, Rahnella and Staphylococcus and fungal taxonomic groups such as Acremomium sp., Cryptococcus flavescens, Cryptococcus zeae, Leptosphaeria sp. andMicrodochium bolleyi were more abundant in the stalks with lower increase in pathogen colonization. Such fungal and bacterial groups associated with ‘suppressive stalks’ may be antagonistic to Fusarium spp. and a source of candidate strains for the selection of new biological control agents
Short-term fluctuations of sugar-beet damping-off by Pythium ultimum in relation to changes in bacterial communities after organic amendments to two soils
He, M. ; Tian, G. ; Semenov, A.M. ; Bruggen, A.H.C. van - \ 2012
Phytopathology 102 (2012)4. - ISSN 0031-949X - p. 413 - 420.
gradient gel-electrophoresis - 16s ribosomal-rna - microbial activity - pseudomonas-fluorescens - fertility amendments - rhizoctonia-solani - fungal antagonists - southern blight - wheat roots - populations
Previously, oscillations in beet seedling damping-off by Pythium ultimum, measured as area under the disease progress curve (AUDPC), were demonstrated after incorporation of organic materials into organic and conventional soils. These periodic fluctuations of P. ultimum infections were cross-correlated with oscillations of copiotrophic CFU at lags of 2 to 4 days. For this article, we investigated whether bacterial communities and microbial activities fluctuated after a disturbance from incorporation of organic materials, and whether these fluctuations were linked to the short-term oscillations in AUDPC of beet seedling damping-off and bacterial populations (CFU) in soil. Soil microbial communities studied by polymerase chain reaction-DGGE analysis of 16S DNA after isolation of total DNA from soil and microbial activities measured as CO2 emission rates were monitored daily for 14 days after addition of grass-clover (GC) or composted manure (CM) into organic versus conventional soils. Similar to our previous findings, AUDPC and density of copiotrophic bacteria oscillated with time. Fluctuations in species richness (S), Shannon diversity index (H), and individual amplicons on DGGE gels were also detected. Oscillations in AUDPC were positively cross-correlated with copiotrophic CFU in all soils. Oscillations in AUDPC were also positively cross-correlated with 19 to 35% of the high-intensity DNA fragments in soils amended with GC but only 2 to 3% of these fragments in CM-amended soils. AUDPC values were negatively cross-correlated with 13 to 17% of the amplicons with low average intensities in CM-amended soils, which were not correlated with densities of copiotrophic CFU. CO2 emission rates had remarkable variations in the initial 7 days after either of the soil amendments but were not associated with daily changes in AUDPC. The results suggest that infection by P. ultimum is hampered by competition from culturable copiotrophic bacteria and some high-intensity DGGE amplicons, because AUDPC is cross-correlated with these variables at lags of 1 to 4 days. However, negative cross-correlations with low-intensity DNA fragments indicate that P. ultimum infection could also be suppressed by antagonistic bacteria with low densities that may be nonculturable species, especially in CM amended soil. The organic soil generally had lower AUDPC values, higher bacterial diversity, and negative cross-correlations between AUDPC and low-intensity DNA fragments (after CM amendment), indicating that specific bacteria that do not attain high densities may contribute to P. ultimum suppression in organic soils
Infectiebronnen zwartvruchtrot in kaart gebracht
Jong, P.F. de; Köhl, J. - \ 2010
stemphylium vesicarium - infectiebestrijding - boomteelt - biologische bestrijding - schimmelantagonisten - trichoderma - plantenresten - infection control - arboriculture - biological control - fungal antagonists - plant residues
Poster met onderzoeksinformatie. Het doel van het onderzoek is het lokaliseren van infectiebron zwartvruchtrot in de boomgaard en vermindering daarvan.
Teler staat niet met lege handen tegenover Botrytis (interview met Leo Marcelis en Jantine Hofland)
Bezemer, J. ; Marcelis, L.F.M. ; Hofland-Zijlstra, J.D. - \ 2010
Onder Glas 7 (2010)2. - p. 36 - 37.
tuinbouw - botrytis - deuteromycotina - microklimaat - omgevingstemperatuur - schimmelziekten - groenteteelt - vochtgehalte - luchtstroming - antagonisten - schimmelantagonisten - glastuinbouw - sierteelt - groenten - horticulture - microclimate - environmental temperature - fungal diseases - vegetable growing - moisture content - air flow - antagonists - fungal antagonists - greenhouse horticulture - ornamental horticulture - vegetables
Botrytis kan in heel wat gewassen fikse problemen veroorzaken. Omdat de sporen in een vochtige omgeving gaan kiemen, is een droog microklimaat de beste remedie. Maar het droogstoken van een hele kas is kostbaar. Met buitenluchtaanzuiging is een betere en energiezuinigere vochtbeheersing te realiseren. Het gewas voldoende open houden, blad snijden en luchtcirculatie zijn manieren om het gewenste microklimaat te bereiken. Antagonisten kunnen Botrytis preventief tegengaan en zijn een alernatief voor chemische middelen, terwijk bestuiving met oxidatieve zoeten of bestrlaing met UV-C-licht met namen in de na-oogst effectief kunnen zijn
Preventieve en curatieve bestrijding van Botrytis stengelaantasting in tomaat met chemische en niet-chemische middelen
Hofland-Zijlstra, J.D. ; Köhl, J. ; Böhne, S. - \ 2009
Bleiswijk : Wageningen UR Glastuinbouw (Rapport / Wageningen UR Glastuinbouw 232) - 20
solanum lycopersicum - tomaten - botrytis - plantenziektebestrijding - biologische bestrijding - chemische bestrijding - schimmelantagonisten - trichoderma hamatum - gliocladium - ziektepreventie - tomatoes - plant disease control - biological control - chemical control - fungal antagonists - disease prevention
Conclusie uit het onderzoek: Preventieve bestrijding van stengelbotrytis werkt duidelijk effectiever dan curatieve bestrijding van al zichtbaar geïnfecteerde plekken. Bij preventieve behandeling van wondvlakken zijn een aantal middelen effectief. Dit betreft zowel chemische middelen als biologische middelen op basis van schimmels. Van de wondafdekmiddelen waren kalk en Botri-spray het meest effectief.
Nieuwe biologische bestrijders van bodempathogene schimmels
Postma, J. - \ 2009
komkommers - cucumis - pythium aphanidermatum - antagonisten - schimmelantagonisten - glastuinbouw - cucumbers - antagonists - fungal antagonists - greenhouse horticulture
Poster met informatie van aanvullend onderzoek naar de antagonist Lysobacter enzymogenes 3.1T8, dat Pythium aphanidermatum in komkommer op substraatteelt effectief kan onderdrukken
Moleculaire en biochemische analyse van antagonistische bacteriën betrokken bij bodemgebonden ziektewering tegen Rhizoctonia solani
Kruijt, M. ; Pangesti, N. ; Wagemakers, L. ; Raaijmakers, J. - \ 2008
Gewasbescherming 39 (2008)supplement. - ISSN 0166-6495 - p. 35S - 36S.
gewasbescherming - thanatephorus cucumeris - plantenziektebestrijding - ziektebestrijdende teeltmaatregelen - bodembacteriën - schimmelantagonisten - biopesticiden - bodemkwaliteit - plant protection - plant disease control - cultural control - soil bacteria - fungal antagonists - microbial pesticides - soil quality
Gebruik de competentie van de bodem voor ziekte- en plaagonderdrukking
Cuijpers, W.J.M. ; Postma, J. ; Bezemer, T.M. ; Bloem, J. ; Paternotte, S.J. ; Messelink, G.J. ; Wurff, A.W.G. van der - \ 2008
Gewasbescherming 39 (2008)Suppl.. - ISSN 0166-6495 - p. 35 - 35.
bodembacteriën - geïntegreerde plagenbestrijding - fusarium - biopesticiden - schimmelantagonisten - bodembeheer - bodemkwaliteit - soil bacteria - integrated pest management - microbial pesticides - fungal antagonists - soil management - soil quality
Biologische bestrijdingsmiddelen: kwaliteitscontrole met behulp van flowcytometrie
Lombaers-van der Plas, C.H. ; Bergervoet, J.H.W. ; Paternotte, S.J. ; Köhl, J. - \ 2008
biologische bestrijding - antagonisten - schimmelantagonisten - monitoring - doorstroomcytometrie - plantenziektebestrijding - biological control - antagonists - fungal antagonists - flow cytometry - plant disease control
Voor een kosteneffectieve biologische bestrijding van plantenziekten met antagonistische schimmels is het nodig de sporen van de antagonisten in grote hoeveelheden te kunnen produceren en formuleren. Flowcytometrie biedt de mogelijkheid om de sporenkwaliteit te monitoren. Oriënterende proeven zijn gedaan voor de kwaliteitsbepaling van meerdere batches van sporen van de modelantagonist PBGY1
Juiste druppelgrootte vergroot efficiëntie Ulocladium
Köhl, J. ; Zande, J.C. van de; Kessel, G.J.T. ; Goossen-van de Geijn, H.M. ; Molhoek, W.M.L. ; Evenhuis, A. - \ 2008
botrytis cinerea - antagonisten - schimmelbestrijding - schimmelantagonisten - biologische bestrijding - organismen ingezet bij biologische bestrijding - druppelgrootte - spuiten - dosering - antagonists - fungus control - fungal antagonists - biological control - biological control agents - droplet size - spraying - dosage
Ulocladium atrum is een veelbelovende antagonist voor bestrijding van Botrytis cinerea in een groot aantal gewassen. Introductie in de praktijk is o.a. afhankelijk van de benodigde dosering. Hoe lager de benodigde hoeveelheid, hoe groter de kans op introductie. Daarvoor is optimalisering van de toepassing van U. atrum nodig. De optimale spuittechniek voor de toepassing van U. atrum tegen B. cinerea werd onderzocht
Botrytis bestrijden met schimmels, bijen en hommels
Steen, J.J.M. van der - \ 2007
Onder Glas 4 (2007)3. - p. 18 - 19.
gewasbescherming - schimmelantagonisten - botrytis - groeiremmers - honingbijen - bombus - verspreiding - biologische bestrijding - glastuinbouw - plant protection - fungal antagonists - growth inhibitors - honey bees - dispersal - biological control - greenhouse horticulture
Op het eerste gezicht lijken Botrytis, bijen en hommels niets met elkaar te maken te hebben, maar toch is er een verband. Honingbijen en hommels kunnen namelijk botrytisinfecties helpen bestrijden of voorkomen. Veel plantpathogene schimmels, waaronder botrytis, infecteren de planten via de bloemen. Als er een andere, voor bloemen ongevaarlijke schimmel, bacterie of gist in de bloem groeit, is daarmee Botrytis te remmen of te voorkomen. Een reportage over deze schimmel en de verspreiding van BCA's door bijen en hommels
Activiteit van cyclische lipopeptide surfactants tegen pathogene Oomyceten
Raaijmakers, J.M. ; Tran Thi Thu Ha, H. ; Boer, M. de; Geerds, C.F. ; Waard, P. de; Beek, T.A. van; Souza, J.T. ; Ficke, A. - \ 2005
Gewasbescherming 36 (2005)1. - ISSN 0166-6495 - p. 23 - 24.
biologische bestrijding - pseudomonas fluorescens - schimmelantagonisten - oömycota - biological control - fungal antagonists - oomycota
Biological control of Botrytis spp. by Ulocladium atrum through competitive colonisation of necrotic plant tissues
Köhl, J. - \ 2004
Wageningen : Plant Research International - 232
botrytis - pezizomycotina - biologische bestrijding - epidemiologie - schimmelantagonisten - biological control - epidemiology - fungal antagonists
Sterke vermindering mogelijk van bewaarverliezen biologisch fruit: tweejarig onderzoek afgerond
Jager, A. de; Westerweele, C.G. ; Verschoor, J. ; Sluis, A. van der - \ 2003
Ekoland 23 (2003)11. - ISSN 0926-9142 - p. 18 - 19.
appels - bederf na de oogst - bewaarziekten - voorraadbederf - systemen na de oogst - verliezen na de oogst - verval - schimmels - rottingsschimmels - behandeling na de oogst - heetwaterbehandeling - schimmelbestrijding - kwaliteit - heteluchtbehandeling - warmtebehandeling - antagonisten - schimmelantagonisten - biologische landbouw - apples - postharvest decay - storage disorders - storage decay - postharvest systems - postharvest losses - decay - fungi - decay fungi - postharvest treatment - hot water treatment - fungus control - quality - hot air treatment - heat treatment - antagonists - fungal antagonists - organic farming
PPO-fruit en ATO onderzochten een aantal methoden om bewaarproblemen bij biologische appelen aan te pakken: rot door schimmels en verlies van vruchtkwaliteit als gevolg van verruwing en vochtverlies. De maatregelen betroffen behandeling met heet water, warme lucht, antagonisten (bezetten de voor schimmels beschikbare plaats), plantversterkers, calciumchloride (wwerstandverhogend) en plantaardige olieën (schimmelonderdrukkend. Bij Elstar lijkt de heetwatermethode een duidelijke reductie te kunnen geven van de bewaarverliezen.
Alternaria in peen bij de bron bestrijden
Molhoek, W.M.L. ; Köhl, J. - \ 2003
Ekoland 23 (2003)2. - ISSN 0926-9142 - p. 23 - 23.
penen - afwijkingen, planten - alternaria radicina - bewaarziekten - gewasbescherming - plantenziektebestrijding - schimmelbestrijding - plantenziekteverwekkende schimmels - zaadproductie - biologische bestrijding - antagonisten - schimmelantagonisten - organismen ingezet bij biologische bestrijding - biologische landbouw - carrots - plant disorders - storage disorders - plant protection - plant disease control - fungus control - plant pathogenic fungi - seed production - biological control - antagonists - fungal antagonists - biological control agents - organic farming
Zwarte-vlekkenziekte, vaak veroorzaakt door de schimmel Alternaria radicini, is een toenemend probleem in de bewaring van peen. De schimmel kan worden overgedragen via zaad. Onderzoek van PRI op proefvelden van Rijk Zwaan BV toonde aan dat biologische bestrijding tijdens de zaadteelt, door de bloem te behandelen met de antagonistische schimmel Ulocladium atrum, effectief kan zijn
Biologische bestrijding van bovengrondse plantenziekten met Ulocladium atrum : biologische akkerbouw en vollegrondsgroenteteelt in perspectief
Meekes, E.T.M. ; Köhl, J. ; Molhoek, W.M.L. ; Goossen-van der Geijn, H.M.G. ; Gerlagh, M. - \ 2002
In: Biologisch bedrijf onder de loep : 'biologische akkerbouw en vollegrondsgroenteteelt in perspectief' / Wijnands, F.G., - p. 103 - 111.
biologische bestrijding - schimmelantagonisten - biologische landbouw - organismen ingezet bij biologische bestrijding - biopesticiden - Ulocladium atrum - biological control - fungal antagonists - organic farming - biological control agents - microbial pesticides
Bij beheersing van ziekten en plagen ligt in de biologische landbouw de nadruk op preventie, om te zorgen dat de kans op aantasting zo klein mogelijk is. Preventie is echter vaak onvoldoende bij zeer mobiele en/of polyfage ziekten en plagen, waardoor directe bestrijding noodzakelijk wordt. Naast fysische en chemische bestrijding kunnen ook biologische middelen worden ingezet. Biologische bestrijding van schimmelziekten met behulp van toevoeging van nuttige micro-organismen is in ontwikkeling. Fundamenteel en toegepast onderzoek, uitgevoerd door instituten en bedrijven, richt zich op de ontwikkeling van biologische bestrijdingsmiddelen voor toepassingen in biologische teelten, maar ook in gangbare systemen. Hier wordt een beeld geschetst van mogelijke bestrijding van bovengrondse ziekteverwekkers d.m.v. het inzetten van antagonisten, met name Ulocladium atrum. Deze antagonist is in staat de grauwe schimmel te onderdrukken onder veldomstandigheden. Mogelijkheden voor het gebruik van deze antagonist tegen andere ziektes, zoals zwarteplekkenziekte in peen en ringvlekkenziekte in kool, worden onderzocht. Verder wordt ingegaan op de mogelijkheden van het gebruik van microbiële bestrijdingsmiddelen in de biologische landbouw
Studies on biological control of powdery mildew in cucumber (Sphaerotheca fuliginea) and rose (S. pannosa) by means of mycoparasites
Verhaar, M.A. - \ 1998
Agricultural University. Promotor(en): J.C. Zadoks; H.D. Frinking. - S.l. : Verhaar - ISBN 9789054859321 - 164
podosphaera fuliginea - podosphaera pannosa - plantenziekteverwekkende schimmels - plantenziekteverwekkers - plantenziekten - komkommers - rozen - komkommerfamilie groenten - rosa - organismen ingezet bij biologische bestrijding - biologische bestrijding - schimmelantagonisten - hyperparasitisme - plant pathogenic fungi - plant pathogens - plant diseases - cucumbers - roses - cucurbit vegetables - biological control agents - biological control - fungal antagonists - hyperparasitism
<p>Powdery mildew on rose ( <em>Sphaerotheca pannosa</em> ) and cucumber ( <em>Sphaerotheca fuliginea</em> ) are two serious diseases in glasshouses. Intensive control by fungicides is needed. The research presented here deals with biocontrol of powdery mildew on cucumber and rose by means of mycoparasites.</p><p>The mycoparasites <em>Ampelomyces quisqualis</em> , <em>Sporothrix rugulosa</em> and <em>Tilletiopsis minor</em> and <em>Verticillium lecanii</em> were tested on rose powdery mildew. <em>V. lecanii</em> produced the best results. For biocontrol at glasshouse scale an efficient production method of phialoconidia of <em>V. lecanii</em> was developed. In exploratory glasshouse experiments <em>V. lecanii</em> was superior to <em>S. rugulosa</em> in controlling cucumber mildew. Especially on a partially resistant cucumber cultivar biocontrol by <em>V. lecanii</em> showed prospect.</p><p>To identify characteristics for the selection of <em>V. lecanii</em> isolates with high potential for biocontrol under glasshouse conditions, effect of water limitation on 14 isolates was explored. Conidial germination, growth and sporulation were all clearly affected by humidity, but showed no correlation with mycoparasitic potential. The effect of timing the biocontrol treatment by <em>V. lecanii</em> was studied on rooted mildewed cucumber leaves. At high humidity early preventative and early curative treatments gave considerable reduction in mildewed leaf area. In semi-commercial glasshouse experiments our <em>V. lecanii</em> isolate, <em>A. quisqualis and Sporothrix flocculosa</em> were tested against cucumber powdery mildew.</p><em><p>A. quisqualis</em> did not control the disease. <em>V. lecanii</em> had only minor effects. <em>S. flocculosa</em> gave the best control. The failure of biocontrol by <em>V. lecanii</em> was attributed to low humidity in the glasshouse. Formulation of <em>V. lecanii</em> with arachid oil significantly reduced its humidity dependence. Possibilities for integrated control are combinations of partially resistant cultivars, formulation of <em>V. lecanii</em> and combination of <em>V. lecanii</em> with fungicides.</p>
Biological control of Verticillium dahliae by Talaromyces flavus
Nagtzaam, M.P.M. - \ 1998
Agricultural University. Promotor(en): M.J. Jeger; G.J. Bollen. - S.l. : Nagtzaam - ISBN 9789054859390 - 133
biologische bestrijding - organismen ingezet bij biologische bestrijding - talaromyces flavus - schimmelantagonisten - verticillium dahliae - biological control - biological control agents - fungal antagonists
<em><p>Verticillium dahliae</em> causes vascular wilt in a wide range of host plants. Control of Verticillium wilt is by soil disinfestation and to a lesser extent by crop rotation or, for a few host plants, by growing resistant varieties. For environmental reasons, the development of alternatives to chemical soil disinfestation is being sought. Biocontrol by microbial agents is one of the options. The potential of <em>Talaromyces flavus</em> as a biocontrol agent in management of the disease is the subject of the thesis.</p><p>The effect of the pathogen on plants was studied to adequately interpret results of biocontrol experiments. Under controlled conditions, a linear relationship was demonstrated between pathogen inoculum density in soil and its population density on roots or in sap extracted from stems. In field experiments, incidence of stem infection by <em>V. dahliae</em> and yield of tubers showed a clear dose-response relation to the amount of pathogen inoculum applied to soil. Incidence of stem infection and density of stem colonisation by the pathogen gradually increased during the season. For studying the effects of antagonists on dynamics of <em>V. dahliae</em> a quantitative bioassay is recommended using eggplant as a test plant.</p><p>Recovery of viable propagules from old samples of seeds coated with ascospores of <em>T. flavus</em> in a clay formulation indicated that products containing the antagonist may have a long shelf life. On the pelleted seeds, a significant proportion of the ascospores had survived a storage period of 17 years.</p><p>In pot experiments with field soils, the fungus moved from seed tubers of potato and seeds of eggplant coated with ascospores to the developing roots, including the root tips, the site where <em>V. dahliae</em> infects the root, albeit at a low density. The population of <em>T. flavus</em> decreased log-linearly with distance from the seed. Results suggest that passive movement along the growing root is one of the main factors involved in colonisation by the fungus.</p><p>The potential of <em>T. flavus</em> to control <em>V. dahliae</em> was evaluated in several experiments. Its application to senescent stems collected from a field with a diseased potato crop reduced viability of microsclerotia. Incorporating an alginate wheat-bran preparation of <em>T. flavus</em> in soil (0.5% w/w) was followed by a decrease of &gt;90% of the population of <em>V. dahliae</em> in soil. The microbial antagonist also reduced colonisation by <em>V. dahliae</em> of roots and infection of eggplants. Although to a lesser extent than with the antagonist, alginate wheat-bran without <em>T. flavus</em> also reduced pathogen colonisation. <em>T. flavus</em> was tested for efficacy to control wilt in two independent field experiments with potato. After application of a <em>T. flavus</em> preparation, stems were less densely colonised by <em>V. dahliae</em> in the treated plots than in the control plots in the first growing season of experiment 1 and in the second growing season of experiment 2. A reduction in plant colonisation by the pathogen was not followed by higher yields of potato tubers. Although population density of <em>T. flavus</em> in soil had not increased during the growing season, it remained at a higher level in treated plots than in non-treated plots, also in the second year after introduction of the antagonist.</p><p>Treatment with combinations of <em>T. flavus</em> with <em>Bacillus subtilis</em> , <em>Fusarium oxysporum</em> or <em>Gliocadium roseum</em> gave similar control of root colonisation and stem infection by <em>V. dahliae</em> as application of the single antagonists. The results suggest that <em>T. flavus</em> is compatible with these antagonists.</p><p>The significance of propagule distribution in soil for the performance of mycoparasites was demonstrated using a simple model. Progress of infection of the host fungus was slower with a random distribution than a uniform distribution of mycoparasite propagules. With a random distribution, the average distance between propagules was 40-50% smaller than with a uniform distribution.</p><p>The results of the experiments presented in this thesis and in the literature, demonstrate that <em>T. flavus</em> has the potential for biocontrol of <em>V. dahliae</em> . However, thus far the results with this antagonist tend to be inconsistent. Control is often partial or even fails completely. This means that application of <em>T. flavus</em> as a single control method has little commercial potential. For the time being, biocontrol is considered as a method to be applied in combination with cultural methods, biological disinfestation, the use of tolerant cultivars or the selective application of chemical control. The next step in further research should focus on the nature of the inconsistency of biocontrol using this fungus.</p>
Beheersing van pathogene Erwinia spp. in de pootaardappelteelt met antagonisten : verslag over het in 1993 t/m 1996 uitgevoerde onderzoek
Kastelein, P. ; Schepel, E.G. - \ 1997
Wageningen etc. : DLO-Instituut voor Planteziektenkundig Onderzoek [etc.] (IPO-DLO rapport nr. 97-02) - 23
solanum tuberosum - aardappelen - pootaardappelen - erwinia - schimmelantagonisten - biopesticiden - antagonisten - biologische bestrijding - organismen ingezet bij biologische bestrijding - potatoes - seed potatoes - fungal antagonists - microbial pesticides - antagonists - biological control - biological control agents
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