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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Metabolic modeling to understand and redesign microbial systems
Heck, Ruben G.A. van - \ 2017
Wageningen University. Promotor(en): Vitor Martins dos Santos, co-promotor(en): Maria Suarez Diez. - Wageningen : Wageningen University - ISBN 9789463434553 - 239
micro-organismen - modelleren - kooldioxide - biotechnologie - algen - metabolisme - pseudomonas - microorganisms - modeling - carbon dioxide - biotechnology - algae - metabolism

The goals of this thesis are to increase the understanding of microbial metabolism and to functionally (re-)design microbial systems using Genome- Scale Metabolic models (GSMs). GSMs are species-specific knowledge repositories that can be used to predict metabolic activities for wildtype and genetically modified organisms. Chapter 1 describes the assumptions associated with GSMs, the GSM generation process, common GSM analysis methods, and GSM-driven strain design methods. Thereby, chapter 1 provides a background for all other chapters. In this work, there is a focus on the metabolically versatile bacterium Pseudomonas putida (chapters 2,3,4,5,6), but also other model microbes and biotechnologically or societally relevant microbes are considered (chapters 3,4,6,7,8).

GSMs are reflections of the genome annotation of the corresponding organism. For P. putida, the genome annotation that GSMs have been built on is more than ten years old. In chapter 2, this genome annotation was updated both on a structural and functional level using state-of-the-art annotation tools. A crucial part of the functional annotation relied on the most comprehensive P. putida GSM to date. This GSM was used to identify knowledge gaps in P. putida metabolism by determining the inconsistencies between its growth predictions and experimental measurements. Inconsistencies were found for 120 compounds that could be degraded by P. putida in vitro but not in silico. These compounds formed the basis for a targeted manual annotation process. Ultimately, suitable degradation pathways were identified for 86/120 as part of the functional reannotation of the P. putida genome.

For P. putida there are 3 independently generated GSMs, which is not uncommon for model organisms. These GSMs differ in generation procedure and represent different and complementary subsets of the knowledge on the metabolism of the organism. However, the differing generation procedures also makes it extremely cumbersome to compare their contents, let alone to combine them into a single consensus GSM. Chapter 3 addresses this issue through the introduction of a computational tool for COnsensus Metabolic Model GENeration (COMMGEN). COMMGEN automatically identifies inconsistencies between independently generated GSMs and semi-automatically resolves them. Thereby, it greatly facilitates a detailed comparison of independently generated GSMs as well as the construction of consensus GSMs that more comprehensively describe the knowledge on the modeled organism.

GSMs can predict whether or not the corresponding organism and derived mutants can grow in a large variety of different growth conditions. In comparison, experimental data is extremely limited. For example, BIOLOG data describes growth phenotypes for one strain in a few hundred different media, and genome-wide gene essentially data is typically limited to a single growth medium. In chapter 4 GSMs of multiple Pseudomonas species were used to predict growth phenotypes for all possible single-gene-deletion mutants in all possible minimal growth media to determine conditionally and unconditionally essential genes. This simulated data was integrated with genomic data on 432 sequenced Pseudomonas species, which revealed a clear link between the essentiality of a gene function and the persistence of the gene within the Pseudomonas genus.

Chapters 5 and 6 describe the use of GSMs to (re-)design microbial systems. P. putida is, despite its acknowledged versatile metabolism, an obligate aerobe. As the oxygen-requirement limits the potential applications of P. putida, there have been several experimental attempts to enable it to grow anaerobically, which have so far not succeeded. Chapter 5 describes an in silico effort to determine why P. putida cannot grow anaerobically using a combination of GSM analyses and comparative genomics. These analyses resulted in a shortlist of several essential and oxygen-dependent processes in P. putida. The identification of these processes has enabled the design of P. putida strains that can grow anaerobically based on the current understanding of P. putida metabolism as represented in GSMs.

Efficient microbial CO2 fixation is a requirement for the biobased community, but the natural CO2 fixation pathways are rather inefficient, while the synthetic CO2 fixation pathways have been designed without considering the metabolic context of a target organism. Chapter 6 introduces a computational tool, CO2FIX, that designs species-specific CO2 fixation pathways based on GSMs and biochemical reaction databases. The designed pathways are evaluated for their ATP efficiency, thermodynamic feasibility, and kinetic rates. CO2FIX is applied to eight different organisms, which has led to the identification of both species-specific and general CO2 fixation pathways that have promising features while requiring surprisingly few non-native reactions. Three of these pathways are described in detail.

In all previous chapters GSMs of relatively well-understood microbes have been used to gain further insight into their metabolism and to functionally (re-)design them. For complex microbial systems, such as algae (chapter 7) and gut microbial communities (chapter 8), GSMs are similarly useful, but substantially more difficult to create and analyze. Algae are widely considered as potential centerpieces of a biobased economy. Chapter 7 reviews the current challenges in algal genome annotation, modeling and synthetic biology. The gut microbiota is an incredibly complex microbial system that is crucial to our well-being. Chapter 8 reviews the ongoing developments in the modeling of both single gut microbes and gut microbial communities, and discusses how these developments will enable the move from studying correlation to causation, and ultimately the rational steering of gut microbial activity.

Chapter 9 discusses how the previous chapters contribute to the research goals of this thesis. In addition, it provides an extensive discussion on current GSM practices, the issues associated therewith, and how these issues can be tackled. In particular, the discussion focuses on issues related to: (i) The inability to distinguish between biological difference and GSM generation artifacts when using multiple GSMs, (ii) The lack of continuous GSM updates, (iii) The mismatch between what GSM predictions and experimental data represent, (iv) The need for standardization in GSM evaluation, and (v) The lack of experimental validation of GSM-driven strain design for metabolic engineering.

Zieke bomen krijgen een jas aan (onderzoek van André van Lammeren en Fons van Kuik)
Lammeren, Andre van - \ 2015
arboriculture - street trees - chestnuts - aesculus - plant protection - plant pathogenic bacteria - pseudomonas - tree surgery - heat treatment - cultural control - educational resources
Bodembacterie helpt plant tegen rupsenvraat
Sikkema, A. ; Pangesti, N.P.D. - \ 2015
Wageningen : St. voor Duurzame Ontwikkeling
arabidopsis - bodembacteriën - rizosfeerbacteriën - pseudomonas - gewasbescherming - rupsen - plaagresistentie - biologische bestrijding - landbouwkundig onderzoek - soil bacteria - rhizosphere bacteria - plant protection - caterpillars - pest resistance - biological control - agricultural research
Bodembacteriën die in het wortelmilieu van planten leven, verminderen de vatbaarheid van planten voor rupsenvraat. Dat blijkt uit onderzoek van Wageningse entomologen. In de modelplant Arabidopsis konden ze aantonen dat rhizobacteriën de plant in verhoogde staat van paraatheid brengen.
Bacterieziekten in Prunus
Dalfsen, Pieter van - \ 2013
prunus - woody plants - bacterial diseases - detection - pseudomonas syringae pv. morsprunorum - xanthomonas - pseudomonas - monitoring - tests - cultural methods - phytosanitary measures
Geïntegreerde beheersstrategie Pythium in bolgewassen
Boer, M. de; Vreeburg, P.J.M. ; Breeuwsma, S.J. ; Bent, J. van der; Roelofs, P.F.M.M. - \ 2013
Lisse : Praktijkonderzoek Plant en Omgeving BBF - 32
pythium - plantenziekteverwekkende schimmels - gewasbescherming - bloembollen - wortelrot - bestrijdingsmethoden - fungiciden - pseudomonas - groenbemesters - veldproeven - modules - plant pathogenic fungi - plant protection - ornamental bulbs - root rots - control methods - fungicides - green manures - field tests
Pythium is een grondgebonden schimmel die in diverse bolgewassen, maar vooral bij hyacint en krokus, veel schade veroorzaakt door wortelrot. Dit wortelrot leidt tot slechte groei van de bol en dus tot opbrengstderving. Er is momenteel één fungicide (Ridomil Gold) toegelaten om Pythium te bestrijden. Echter, de toepassing van dit fungicide resulteert niet altijd in een Pythium vrij gewas. Uit eerder onderzoek is bekend dat wortelrot in hyacint ook bestreden wordt door toepassing van een bacterie, Pseudomonas SS101, en door het onderwerken van een groenbemester zoals bladrammenas. Maar, net als bij Ridomil Gold, geldt ook voor deze maatregelen dat wanneer deze maatregel alleen wordt toegepast dit vaak niet resulteert in een betrouwbare en voldoende bestrijding. Daarom is in een meerdere jaren durend project onderzocht of het toepassen van (combinaties van) deze maatregelen gedurende een aantal jaren achter elkaar in verschillende samenstellingen wel effectief Pythium wortelrot kan bestrijden. De verwachting is dat op deze manier Pythium gedurende een aantal jaren met behulp van verschillende mechanismen wordt bestreden zodat de bestrijding veel effectiever is en langdurig.
Minder lage RV biedt mogelijkheden tot energiebesparing: Bij Phalaenopsis is 75% RV laag genoeg om Pseudomonas te voorkomen
Arkesteijn, M. ; Ludeking, D.J.W. - \ 2011
Onder Glas 8 (2011)8. - p. 50 - 51.
phalaenopsis - plantenplagen - pseudomonas - preventie - gewasbescherming - relatieve vochtigheid - energiebesparing - landbouwkundig onderzoek - glastuinbouw - groenten - potplanten - plant pests - prevention - plant protection - relative humidity - energy saving - agricultural research - greenhouse horticulture - vegetables - pot plants
Pseudomonas catteyea is al een oud probleem in de teelt van phalaenopsis. Bij een relatieve luchtvochtigheid van 90% kan de bacterie zich snel verspreiden door de kas. Uit recent onderzoek blijkt dat dit probleem minder optreedt bij een RV van 75% of lager. De RV verlagen tot 60% zoals nu gebeurt, hoeft dus niet. Dit biedt mogelijkheden tot energiebesparing.
Detectie en beheersing van bacterierot veroorzaakt door Pseudomonas cattleyae in Phalaenopsis
Ludeking, D.J.W. ; Hamelink, R. ; Kromwijk, J.A.M. ; Schenk, M.F. ; Vermunt, A. ; Woets, F. - \ 2011
Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1096) - 31
phalaenopsis - bacterieziekten - infectie - pseudomonas - bladvlekkenziekte - black spot - moleculaire technieken - relatieve vochtigheid - waterzuivering - invloeden - bacterial diseases - infection - leaf spotting - molecular techniques - relative humidity - water treatment - influences
Phalaenopsis growers suffer from mayor losses up to 20% due to bacterial spot. This bacterial infection in caused by the Acidovorax avenae subsp. cattleyae. In practice this bacterial disease is also known as Pseudomonas. This bacterium is causing black leaf spots with a yellow border. Pseudomonas cattleyae is very contagious and is promoted by high temperatures en moist conditions. In this project Groen Agro Control laboratory (Delfgauw) has developed a molecular analysis method to detect Pseudomonas cattleyae in different matrices. The influence of the relative humidity on the development of Pseudomonas cattleyae is investigated during this research. The results show that a relative humidity of 90% strongly promotes infection of the bacteria. A relative humidity of 75% shows no extra dispersion of Pseudomonas cattleyae compared to a greenhouse compartment with a continuous relative humidity of 60%. This knowledge offers the opportunity to safe energy in the cultivation of Phalaenopsis. During this research the effects of water treatments on the dispersion of Pseudomonas cattleyae have been investigated. The results show that a treatment with hydrogen peroxide (20 ppm) offers the best reduction of dispersion. This treatment turns out to be better than the control and all other treatments. This research has led to new insights about the dispersal and optimal growing conditions of this bacteria, but leads to new questions. Questions, about other different dosages and the effects of other water treatments, but also about the optimal level to promote plant growth and reduce bacterial infections, have to be investigated in new research.
Kasproef detectie en beheersing van Pseudomonas cattleyae in Phalaenopsis
Kromwijk, J.A.M. ; Ludeking, D.J.W. ; Woets, F. ; Vermunt, A. ; Schenk, M.F. - \ 2010
gewasbescherming - bacteriën - infecties - verspreide infecties - preventie - pseudomonas - phalaenopsis - glastuinbouw - plant protection - bacteria - infections - disseminated infections - prevention - greenhouse horticulture
Samenvatting van een kasproef getiteld "detectie en beheersing van Pseudomonas cattleyae in Phalaenopsis"
Slijmstelen bij Zantedeschia
Leeuwen, P.J. van; Pham, K.T.K. ; Dees, R.H.L. ; Doorn, J. van - \ 2009
Lisse : PPO Bloembollen en Bomen (PPO Rapport 32 340357 00) - 49
erwinia - pseudomonas - afwijkingen, planten - zantedeschia - vaasleven - houdbaarheid (kwaliteit) - landbouwkundig onderzoek - nederland - plant disorders - vase life - keeping quality - agricultural research - netherlands
Slijmstelen zijn bloemstengels van Zantedeschia die op de vaas vooral aan de onderkant verslijmen als gevolg van bacterieaantasting. Deze afwijking vormt een van de grootste problemen in de afzet van de bloemen. Hoewel vermoed werd dat Erwinia (carotovora subsp. carotovora) de veroorzaker is, blijken ook Pseudomonas-soorten die pectinasen (celwandafbrekende enzymen) produceren, slijmstelen te kunnen veroorzaken. Op grond van de DNA-sequentie van deze pectinase (pel-) genen zijn in PCR deze bacteriën te identificeren; het pel-gen blijkt noodzakelijk om slijmstelen te kunnen veroorzaken. Bij lokalisatie-experimenten bleek soms bij de oogst ook hoog in de steel veel bacteriën aanwezig te zijn; het trekken van de stelen lijkt geen knikstelen te kunnen veroorzaken. Injectie van stelen met Erwinia of Pseudomonas veroorzaakte slijmstelen. Ook kunnen bacteriën overleven op (veiling-) fust, rekjes en in water. Het is aannemelijk, dat er gezonde en zieke partijen stelen zijn; in sommige partijen zit al een percentage pseudomonaden, mogelijk latent. Als beheersingsmaatregelen kan dienen het afsnijden van de onderste 2-5 cm van de steel; dit levert significant minder slijmstelen op. Middelen zoals de chloorpil en Florissant werken goed mits er niet te hoge aantallen bacteriën in het vaaswater zitten; deze middelen kunnen echter niet via passieve diffusie hoog in de stelen komen. Er bleek geen goede correlatie tussen aantallen bacteriën in de bloemstelen enerzijds en het ontstaan van slijmstelen; niet alle bacteriën die hierin groeien geven namelijk slijmstelen. © Praktijkonderzoek
Methoden voor residuafbraak op fruit
Jong, P.F. de; Balkhoven-Baart, J.M.T. - \ 2009
De Fruitteelt 99 (2009)37. - ISSN 0016-2302 - p. 10 - 11.
fruitteelt - pruimen - onderstammen - pseudomonas - groot-brittannië - fruit growing - plums - rootstocks - great britain
De ervaringen met de pruimonderstam VVA-1 zijn divers. Sommige percelen hebben te maken met veel uitval door Pseudomonas- al dan niet weg te schrijven aan de onderstam - aan andere percelen is geen zieke boom te ontdekken. Een reden voor de Productcommissie Steenfruit om eens een kijkje te nemen naar ervaringen in Groot-Brittanië
Genotypische diversiteit en rhizosfeerkolonisatie van DAPG-producerende Pseudomonas spp.
Bergsma-Vlami, M. - \ 2009
Gewasbescherming 40 (2009)3. - ISSN 0166-6495 - p. 117 - 118.
genotypische variatie - pseudomonas - soorten - antibiotica - biologische bestrijding - gewasbescherming - genetic variance - species - antibiotics - biological control - plant protection
Het antibioticum 2,4-diacetylphloroglucinol (DAPG) speelt een belangrijke rol in biologische bestrijding van verschillende plantenpathogenen door fluorescerende Pseudomonas-soorten. DAPG-producerende Pseudomonas-stammen zijn effectief in biologische bestrijding, maar hun saprofytisch vermogen is vaak variabel met als gevolg dat ook de mate van ziekteonderdrukking niet altijd consistent is
Genotypic diversity and rhizosphere competence of antibiotic-producing Pseudomonas species
Bergsma-Vlami, M. - \ 2008
Wageningen University. Promotor(en): Pierre de Wit, co-promotor(en): Jos Raaijmakers. - [S.l. : S.n. - ISBN 9789085049524 - 192
pseudomonas - antibiotica - rizosfeerbacteriën - rizosfeer - populatiedynamica - genetische diversiteit - biologische bestrijding - suikerbieten - antibiotics - rhizosphere bacteria - rhizosphere - population dynamics - genetic diversity - biological control - sugarbeet
The phenolic antibiotic 2,4-diacetylphloroglucinol (DAPG) has been implicated in biological control of multiple plant pathogens by fluorescent Pseudomonas species. DAPG-producing Pseudomonas strains are effective biocontrol agents, however, their ecological performance is often highly variable resulting in inconsistent disease suppression. The ecological performance is complex and determined by many bacterial traits and environmental factors, including the host plant. In this thesis, several genotypic and phenotypic characteristics underlying the ecological performance of DAPG-producing Pseudomonas were investigated.
To discriminate between genotypically different DAPG-producing Pseudomonas strains directly in rhizosphere samples without their prior isolation or enrichment on nutrient media, a simple and rapid method was developed based on polymorphisms in the polyketide synthase gene phlD. Denaturing Gradient Gel Electrophoresis (DGGE) analysis, sequencing and phylogenetic analyses of indigenous phlD+ isolates obtained from the rhizosphere of wheat, sugar beet and potato plants, resulted in the identification of seven phlD+ genotypes, designated A, B, C, D, E, F, and Z, five of which were not described previously (C, D, E, F and Z). The phlD-DGGE analysis allowed simultaneous detection of multiple phlD+ isolates in the rhizosphere and, compared to cultivation-based approaches, this technique does not have the bias toward detecting either the most dominant genotype or the genotype with higher growth rates or competitive abilities during cultivation.
Subsequent studies with representative strains of each of the Pseudomonas genotypes showed that three genotypes (A, Z and G) were superior in long-term colonization of roots of wheat, sugar beet and potato plants. These results suggest that their rhizosphere competence is not linked to a specific plant species, but is due to yet unknown characteristics that enable these strains to be competitive in different rhizosphere environments. In contrast, the rhizosphere competence of Pseudomonas genotypes E, C and F was dependent on the plant species and, therefore, these strains are considered to be specialists instead of generalists.
Results of this thesis further showed that the host plant species also have a significant effect on DAPG-production by indigenous phlD+ Pseudomonas: the wheat and potato rhizospheres supported significantly higher amounts of DAPG produced per cell basis than the rhizospheres of sugar beet and lily. In the same context, the eight Pseudomonas genotypes differed significantly in their ability to produce DAPG in the rhizosphere of sugar beet plants with in situ DAPG concentrations ranging from 1 to 144 ng per 105 cells. Based on these data, significant correlations were established between the rhizosphere competence of a genotype and in situ DAPG production levels. In general, these correlations suggest that Pseudomonas genotypes that produce high amounts of DAPG per cell basis in situ establish lower population densities in the sugar beet rhizosphere than genotypes that produce small amounts of DAPG. To our knowledge, this is the first study that shows an inverse correlation between rhizosphere competence of Pseudomonas strains and in situ antibiotic production.
Biocontrol assays showed that P. ultimum was effectively controlled by all eight Pseudomonas strains and differential effects were observed in biocontrol activity against A. cochlioides. Pseudomonas genotype G was the most effective in biocontrol of Pythium and Aphanomyces damping-off, and its biocontrol activity was due, at least in part, to DAPG production as its DAPG-deficient mutant was significantly less effective. Comparative analysis of the eight DAPG-producing Pseudomonas genotypes revealed a highly significant correlation between their rhizosphere competence and efficacy to control Aphanomyces damping-off of sugar beet. These results indicate that the more rhizosphere competent DAPG-producing Pseudomonas strains are, the higher their efficacy is to control A. cochlioides in sugar beet. The promising results obtained with genotypes A, Z and G in the sugar beet bioassays provide a strong basis for their implementation in the current integrated disease management strategies in sugar beet.
The results acquired in this thesis have shown that the identification of the genotypic diversity and rhizosphere competence of antibiotic-producing Pseudomonas species is of great value, because it may allow maximizing root colonization and disease suppression. Knowledge of genetic traits involved in host preference of these antagonistic bacteria will help to identify strains that are adequately adapted to specific host-pathogen systems. Similarly, looking into plant traits that promote the growth and activity of introduced biocontrol strains can be highly complementary and further contribute to sustainability in agriculture.
Tijdbom pseudomonas nog niet onklaar gemaakt
Kruistum, G. van; Overbeek, L.S. van - \ 2008
Groenten & Fruit 18 (2008)4. - ISSN 0925-9708 - p. 48 - 49.
tuinbouw - allium porrum - preien - pseudomonas - bacterieziekten - gewasverliezen - plantenziektebestrijding - onderzoek - plantenziekteverwekkende bacteriën - horticulture - leeks - bacterial diseases - crop losses - plant disease control - research - plant pathogenic bacteria
Vooral in Limburg en Noord-Brabant zijn de productieverliezen door Pseudomonas in prei groot. De bacterie blijkt latent aanwezig te zijn op meer dan 60 procent van de bemonsterde percelen voor de opkweek en teelt van prei
Onderdrukking van ziekten en plagen in prei
Overbeek, L.S. van; Kruistum, G. van; Visser, J.H.M. - \ 2007
pseudomonas - preien - allium porrum - plantenziekteverwekkende bacteriën - gewasbescherming - vollegrondsteelt - leeks - plant pathogenic bacteria - plant protection - outdoor cropping
Onderzoek naar het onderdrukken van Pseudomonas (bacterievlekkenziekte) in prei
Interactions between biosurfactant-producing Pseudomonas and Phytophthora species
Tran, H. - \ 2007
Wageningen University. Promotor(en): Pierre de Wit, co-promotor(en): Jos Raaijmakers. - [S.l.] : S.n. - ISBN 9789085047445 - 136
plantenziekteverwekkende schimmels - phytophthora - biologische bestrijding - pseudomonas - oppervlaktespanningsverlagende stoffen - gastheer parasiet relaties - oömycota - plant pathogenic fungi - biological control - surfactants - host parasite relationships - oomycota
Fluorescent Pseudomonas bacteria produce a wide variety of antimicrobial metabolites, including soap-like compounds referred to as biosurfactants. The results of this thesis showed that biosurfactant-producing Pseudomonas bacteria are effective in controlling Phytophthora foot rot disease of black pepper in Vietnam and promote root and shoot development of the ‘King of Spices’. Biosurfactant-producing P. fluorescens strain SS101 was also effective in controlling tomato late blight caused by Phytophthora infestans. Current and future studies focus on how to implement these biocontrol agents in an integrated management practice to control Phytophthora diseases. The broad-spectrum activity of these antagonistic Pseudomonas bacteria and their biosurfactants also provide new opportunities to apply these agents for the protection and growth promotion of other crops.
Effect van tussengewassen, Ridomil Gold en Pseudomonaden op Pythium beheersing in crocus en hyacint
Bijman, V.P. ; Breeuwsma, S.J. ; Boer, M. de; Koster, A.T.J. ; Bent, J. van der - \ 2005
Gewasbescherming 36 (2005)1. - ISSN 0166-6495 - p. 21 - 23.
tussengewassen (intercrops) - pseudomonas - fungiciden - crocus - hyacinthus - intercrops - fungicides
Pseudomonas in prei wijd verbreide tijdbom
Overbeek, L.S. van - \ 2005
Groenten en Fruit. Algemeen 2005 (2005)6. - ISSN 0925-9694 - p. 36 - 37.
allium porrum - preien - pseudomonas - gewasbescherming - bacterieziekten - cultuurmethoden - leeks - plant protection - bacterial diseases - cultural methods
Pseudomonas is een bacterie die onzichtbaar is, verpreid zich als een olievlek en is amper te bestrijden. Hoe groot is het probleem en hoe is te voorkomen dat de teelt van prei het aflegt tegen pseudomonas?
Pythium: inzet nuttige bacteriën bekeken
Leeuwen, P.J. van; Trompert, J.P.T. - \ 2005
BloembollenVisie (2005)66. - ISSN 1571-5558 - p. 24 - 24.
crocus - plantenziekteverwekkende schimmels - pythium - pseudomonas - fungiciden - bestrijdingsmethoden - biologische bestrijding - plant pathogenic fungi - fungicides - control methods - biological control
De afgelopen jaren is gezocht naar diverse methoden om Pythium in krokus te beheersen zonder chemische middelen. Zo is het inzetten van nuttige bacteriën en extreem vroeg planten onderzocht. De resultaten waren wisselend. PPO Bloembollen zet het onderzoek met bacteriën voort
Bacterial oxidation of low-chlorinated compounds under anoxic conditions
Dijk, J.A. - \ 2005
Wageningen University. Promotor(en): Fons Stams, co-promotor(en): Gosse Schraa; J. Gerritse. - [S.I.] : S.n. - ISBN 9085041260 - 112
gechloreerde koolwaterstoffen - oxidatie - pseudomonas - chlorinated hydrocarbons - oxidation
Toepassing van Pseudomonasbacteriën ter bestrijding van Pythium in bloembollen : praktijkproef Hyacint
Boer, M. de; Werd, H.A.E. de; Breeuwsma, S.J. - \ 2004
Lisse : Praktijkonderzoek Plant & Omgeving, Sector Bloembollen - 17
pythium - biologische bestrijding - pseudomonas - plantenziektebestrijding - bloembollen - landbouwkundig onderzoek - nederland - biological control - plant disease control - ornamental bulbs - agricultural research - netherlands
PPO Bloembollen doet onderzoek naar alternatieve beheersingsstrategieën om schade door Pythium wortelrot in bloembolgewassen tegen te gaan. Naar aanleiding van positieve resultaten uit eerdere proeven op kleine schaal is in opdracht van de productgroep Hyacint bestrijding met Pseudomonas bacteriën getest op een drietal percelen. Deze proef moet duidelijk maken of met de huidige kennis eerdere positieve resultaten te reproduceren zijn onder diverse praktijk omstandigheden. De toepassing van Pseudomonas heeft de gewasstand en bolopbrengst op een perceel dat niet met Pythium was besmet niet beïnvloed. Op twee percelen die wel met Pythium besmet waren zijn wel positieve effecten van de bacteriën gevonden. Het gewas bleef langer groen en/of de bolopbrengst werd hoger. Deze positieve effecten kwamen echter niet consequent terug over de twee proefjaren en de verschillende percelen. Op dit moment lijkt een behandelingen met Pseudomonasbacteriën onvoldoende betrouwbaar om als enige maatregel tegen Pythiumschade te gebruiken. De werking is echter wel zodanig goed dat Pseudomonas bacteriën kunnen worden ingezet als onderdeel van een Pythium beheersstrategie waar momenteel aan gewerkt wordt. In deze Pythium beheersstrategie worden verschillende maatregelen, zoals b.v. een fungicide, een biofumigatie gewas en de Pseudomonas bacterie, zodanig met elkaar gecombineerd dat dit zal resulteren in een goede Pythium beheersing.
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