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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Improving the limits of detection in sensor systems
Bent, J.F. van der - \ 2017
University. Promotor(en): Cees van Rijn. - Wageningen : Wageningen University - ISBN 9789463430555 - 127
sensors - data processing - nanotechnology - potentiometers - detection - gegevensverwerking - nanotechnologie - detectie

Nowadays, sensors are designed to consume less power with decreased size, making them suitable for application in low-power wireless sensor networks (WSN) systems. The challenge is not to compromise on the sensor’s sensitivity and selectivity towards the target. This thesis studies various options to improve the limits of detection. Usually, sensors are limited in detection range and resolution; they are also restricted by cross sensitivity towards other target agents and other parameters. This cross sensitivity, towards humidity and temperature, for instance, reduces the sensor’s detection limit and, therefore, its usability. This work discusses three examples where the limit of detection has been investigated, localised and improved with nanotech-based sensors.

The first example is a nanowire-based hydrogen sensor. The second example was based on a potentiometric-sensor principle, capable of sensing CO2. The third example is an Inter-Digitated Electrode (IDE) sensor, capable of selective sensing through the coating of an active layer.

Unravelling aspects of spatial and temporal distribution of Verticillium dahliae in olive, maple and ash trees and improvement of detection methods
Keykhasaber, Mojtaba - \ 2017
University. Promotor(en): Bart Thomma; Pierre de Wit, co-promotor(en): Jelle Hiemstra. - Wageningen : Wageningen University - ISBN 9789463430142 - 163
olea europaea - olives - acer - fraxinus - plant pathogenic fungi - verticillium dahliae - distribution - virulence - detection - olijven - plantenziekteverwekkende schimmels - distributie - virulentie - detectie

Vascular wilts caused by xylem-colonizing pathogens are among the most devastating plant diseases that affect a wide range of plant species worldwide. Information on the distribution of V. dahliae in infected trees helps to design an appropriate and efficient sampling method for reliable detection of the pathogen in diseased trees. In Chapter 3, the distribution of V. dahliae in young twigs and leaves of infected olive trees is studied by real-time quantification of V. dahliae DNA. Analysis of twig and leaf samples collected from different sides of the crown of infected olive trees showed a non-uniform distribution of the fungus within infected parts of diseased olive trees. It was demonstrated that testing of combined samples comprising subsamples from at least 5 twigs from different sides of the tree, or 5-10 random leaves, can reliably detect the pathogen. V. dahliae isolates that infect olive trees can be classified as defoliating (D) isolates that are highly virulent, or non-defoliating (ND) isolates that are generally less aggressive. Discrimination of these pathotypes is important in order to predict the severity of disease, and decide on appropriate disease management strategies. This is particularly important due to the alarming spread of highly virulent isolates of the D pathotype worldwide. In Chapter 4, a novel method is designed for accurate discrimination and sensitive detection of D and ND isolates of V. dahliae. Through comparative genomics of multiple D and ND isolates of V. dahliae a region was identified that is present in all sequenced ND isolates, while absent from all D isolates. Based on this presence-absence polymorphism, a set of primers was designed spanning this region that was able to generate differentially sized amplicons for isolates that belong to the different pathotypes. Additionally, a nested-PCR assay was designed to increase the sensitivity and improve detection of D and ND isolates in planta. In Chapter 5, the relation of the dynamics in pathogen distribution in infected plants to the differences in extent and severity of disease caused by D and ND isolates in resistant and susceptible olive genotypes is studied. To this end, the distribution of a D (V117) and a ND (V4) isolate of V. dahliae in root-inoculated young plants of a susceptible (Picual) and a partially resistant cultivar (Frantoio) of olive and its relationship to the disease progression was investigated using real-time PCR. The amount of pathogen DNA detected in the two cultivars correlated with their susceptibility to Verticillium wilt, with lower quantities of V4 and V117 DNA detected in ‘Frantoio’ than in ‘Picual’. Also quantities of pathogen DNA in V117-inoculated plants were higher than quantities of pathogen DNA in V4-inoculated plants. The distribution patterns of D and ND isolates in the lower, middle and top parts of tested olive cultivars showed that differences in symptom severity were related to amounts of the pathogen in lower and middle parts of the trees, since colonization of the pathogen in top parts of the stem of inoculated plants was minor and was not significantly different between treatments. Moreover, microscopic analysis of infection and colonization processes of V. dahliae in olive plants inoculated with GFP-labelled isolates revealed that colonization of the above ground tissues of infected olive plants is by means of conidia transported upward with the xylem sap stream. In Chapter 6 we investigated the spatial and temporal distribution of V. dahliae in relation to disease progression and recovery in stem-inoculated maple and ash trees. These species differ strongly in vascular anatomy with maple having a diffuse porous xylem anatomy whereas ash has a ring porous xylem anatomy. Results showed that that differences in the xylem anatomy of ash and maple did not significantly affect the speed and extent of the upward spread of the pathogen in stem-inoculated trees. Nevertheless, the xylem of ash trees is much less supportive for growth and survival of V. dahliae than that of maple trees, as in the year after inoculation disease incidence and also quantities of V. dahliae detected in maple trees were significantly higher than in ash trees. Moreover, V. dahliae could not be reisolated at all from ash trees that had recovered from disease. However, it could be detected by PCR in some cases in the xylem formed in the year of inoculation, never in the xylem formed in the year after inoculation. Nevertheless, V. dahliae easily could be detected in the wood of diseased ash and maple trees in the year after inoculation. Notably, despite the presence of a layer of terminal parenchyma cells between growth rings, in ash trees showing disease symptoms in the year after inoculation V. dahliae was present in the xylem of the new growth ring. It was also observed that in stem-inoculated trees V. dahliae can move downward from the point of inoculation into the root collar, which may provide an avenue for infection of new growth rings in ash trees.

Toetsontwikkeling PSTVd in Dahlia
Leeuwen, P.J. van; Trompert, J.P.T. ; Lemmers, M.E.C. ; Verbeek, M. ; Meekes, E.T. - \ 2016
Lisse : Praktijkonderzoek Plant & Omgeving, onderdeel van Wageningen UR Business Unit Bloembollen, Boomkwekerij en Fruit - 23 p.
dahlia - plantenvirussen - aardappelspindelknolviroïde - detectie - extractie - experimenteel veldonderzoek - methodologie - diagnostische technieken - nederland - plant viruses - potato spindle tuber viroid - detection - extraction - field experimentation - methodology - diagnostic techniques - netherlands
Improvement of methods for the detection of Gram-negative foodborne pathogens
Margot, H.F.T. - \ 2016
University. Promotor(en): Marcel Zwietering; Han Joosten, co-promotor(en): R. Stephan. - Wageningen : Wageningen University - ISBN 9789462578708 - 158 p.
gram negative bacteria - pathogens - foodborne pathogens - detection - real time pcr - salmonella - escherichia coli - mung beans - gramnegatieve bacteriën - pathogenen - voedselpathogenen - detectie - mungbonen

Foodborne diseases are a major source of morbidity and mortality worldwide. In most cases, these diseases are caused by contaminated food products, but transmission can also subsequently occur via person to person contact. The ability to detect the pathogens is an important aspect in the verification of food safety. A major proportion of foodborne disease is caused by Gram-negative bacteria. In this thesis, the detection of Gram-negative foodborne pathogens is addressed by looking at the successive steps from enrichment to detection with Salmonella, Shiga toxin-producing E. coli and Cronobacter spp. as example pathogens. The detection of foodborne pathogens using microbiological culture media aiming at the resuscitation and growth of bacteria is still regarded as the gold standard and included in many reference methods. However, cultural methods are time and labour-intensive. Since an immediate response is required in case of contamination and during outbreaks there is a strong interest in methods that deliver information on the microbiological status of the product as quickly and reliable as possible. Rapid cultural methods and commercially available real-time PCR systems for the detection of Salmonella and STEC were compared with regards to their sensitivity and specificity. It was shown that most of the marketed systems are as reliable as the standard methods. However, false-positive results were obtained with real-time PCR systems for the detection of Salmonella. Rapid cultural methods that were based on procedures without the pre-enrichment step, reduced the time to detection but did show some ambiguous results with difficult matrices such as tea. Of the seven rapid tests for the detection of STEC, one did not detect relevant Stx subtypes.

In order to be detected, pathogens need to multiply to reach a minimum threshold level. However, because they are often sublethally injured due to hostile processing and storage conditions, they first need to be resuscitated. For most pathogens, (Salmonella, STEC and Cronobacter spp.) the first step in the detection is an enrichment including resuscitation in a non-selective medium such as BPW. Modifications to BPW were compared with respect to their ability to promote growth of unstressed and stressed Gram-negative pathogens. The aim was to develop a medium that could be used for the enrichment of pathogens in horizontal methods using only one enrichment step. The resuscitation of stressed Cronobacter cells was improved in BPW supplemented with an additional iron source and sodium pyruvate along with low levels of compounds for the inhibition of Gram-positive bacteria. However, it was observed that BPW containing these supplements allowed for less resuscitation of STEC when compared to regular BPW. Based on these results it was concluded that the application of a one-broth enrichment in food products with a high number of competing bacteria is not recommended due to the overgrowth of the target bacteria. Limitations of the current method for the detection of STEC from sprouted seeds were noticed. Therefore, the growth of stressed STEC cells from different serotypes was assessed in media used for the enrichment of Enterobacteriaceae. In addition, the growth of STEC was examined in the enrichment of sprouts using different media and incubation temperatures. It was shown that the high level of competitors was inhibiting the detection of the target pathogen and that the similarity of target and competing bacteria prevents the design of a selective enrichment procedure. In order to get a better insight in the enrichment ecology, the microbiome of mungo bean sprouts was analysed using Illumina HiSeq sequencing prior to and during the enrichment in BPW and EE-broth at different temperatures. The majority of the sprout flora was composed of bacteria belonging to the phylum Proteobacteria. Enrichment in BPW increased the proportion of Firmicutes whereas the incubation in EE-broth enriched Proteobacteria. The results point out that with the application of a selective medium like EE-broth, growth of the competitive microflora that complicates the detection of STEC is promoted. It was shown that EE-broth also resulted in good growth of STEC however, the problematic situation of low maximum population densities of the target strain in the matrix is still present. The probability of detection is not only influenced by the natural flora of a food product, but also by the physiological state of the pathogen. The influence of stress on the lag time of single cells and the resulting probability of detection were determined for Cronobacter spp. in powdered infant formula. Lag time was calculated from optical density measurement data and different scenarios were modelled. Lag time was longest after acid stress and lag time increase coincided with increased lag time variability. The probability of detection, however, depended both on the sampling plan and on the duration of the lag phase.

This thesis provides a critical evaluation of rapid methods and valuable new insights on enrichment procedures, the role of competitors in bacterial enrichment procedures and the limitations of selective agents. This information will be of great help to further improve microbiological methods and thereby contribute to more effective management of food safety.

Smart Ziekzoeker 2015 : Detectie van virus- en bacteriezieke pootaardappelen met behulp van vision- en sensortechnologie
Kamp, J.A.L.M. ; Blok, P.M. ; Polder, G. ; Wolf, J.M. van der; Jalink, Henk - \ 2016
Lelystad : Praktijkonderzoek Plant & Omgeving (Applied Plant Research) Business Unit AGV (PPO/PRI rapport 703) - 51 p.
pootaardappelen - solanum tuberosum - plantenziekteverwekkende bacteriën - plantenvirussen - detectie - sensors - machine vision - seed potatoes - plant pathogenic bacteria - plant viruses - detection
Plantenvirussen in het vizier
Stijger, I. ; Verbeek, M. - \ 2016
Wageningen UR
plantenvirussen - virusziekten - ziekteoverdracht - detectie - ziektedistributie - diagnose - bedrijfshygiëne - plant viruses - viral diseases - disease transmission - detection - disease distribution - diagnosis - industrial hygiene
Aandacht wordt geschonken aan: voedingswater, micro-leven, rasverschillen, en oud stekmateriaal. Poster van PlantgezondheidEvent 12 maart 2015.
Resistentieveredeling - Stressfactoren en verschillende typen belagers : Kennisclip Bogo-project e-learning.
Hop, M.E.C.M. - \ 2016
Groen Kennisnet
resistance breeding - stress factors - plant breeding - selection methods - disease resistance - plant protection - teaching materials - detection - pathogens - resistentieveredeling - stressfactoren - plantenveredeling - selectiemethoden - ziekteresistentie - gewasbescherming - lesmaterialen - detectie - pathogenen
Deze kennisclip maakt onderdeel uit van de lesmodule Resistentie Veredeling van het CIV T&U.
Biologisch redmiddel tegen verwelkingsziekte in de Boomkwekerij : kennis en ervaringen uit een praktijknetwerk
Sluis, B.J. van der; Even, S. - \ 2015
Randwijk : Praktijkonderzoek Plant & Omgeving, Business Unit Bloembollen, Boomkwekerij en Fruit - 33 p.
boomkwekerijen - houtachtige planten als sierplanten - straatbomen - rosaceae - bodemschimmels - verticillium dahliae - biologische grondontsmetting - detectie - veldproeven - verwelkingsziekten - groenbemesters - folie - forest nurseries - ornamental woody plants - street trees - soil fungi - biological soil sterilization - detection - field tests - wilts - green manures - foil
Het doel van het project is om door samenwerking tussen kwekers, loonbedrijf, onderzoek en teelt-advisering de implementatie van (duurzame) biologische grondontsmetting te stimuleren door het samen opdoen en delen van kennis hierover. Daarnaast is er behoefte aan een snelle en nauwkeurige methode voor detectie van Verticillium in grond de bodem. Deze wordt in een EU-MKB project ontwikkeld. Vanuit het praktijknetwerk zal zo mogelijk kennis uit dit project benut worden.
Onderzoek in het kader van het ‘Actieplan Minder Virus in Tulp’, uitgevoerd door PPO- Bloembollen, Lisse en Proeftuin Zwaagdijk in 2013 en 2014
Dam, M.F.N. van; Verbeek, M. ; Stijger, I. ; Kreuk, F. - \ 2015
Lisse : Praktijkonderzoek Plant & Omgeving B.V., Sector Bomen, Bollen & Fruit - 66
tuinbouw - bloembollen - tulpen - gewasbescherming - virusziekten - tulpenmozaïekvirus (tulip breaking virus) - tulpenvirus x - tulpenmozaïekvirus (tulip mosaic virus) - plantenziektebestrijding - mineraaloliën - detectie - locatie - afmetingen - landbouwkundig onderzoek - horticulture - ornamental bulbs - tulips - plant protection - viral diseases - tulip breaking virus - tulip virus x - tulip mosaic virus - plant disease control - mineral oils - detection - location - dimensions - agricultural research
Doelstellingen van het Actieplan “Minder virus in Tulp” zijn: Dit project organiseert de opstart en de uitvoering van een actieplan dat leidt tot minder virus in tulp in een economisch rendabele teelt. De aandacht ligt met name bij TBV, TVX, Augustaziek, ArMV en LSV. Uitvoering van het actieplan moet leiden tot enthousiasme en power in de sector waardoor ook nieuwe inspiratie voor innovaties ontstaat. De beoogde modulaire en stapsgewijze aanpak van dit project zorgt voor een duidelijke afbakening van doelstellingen, activiteiten en budget en maakt tussentijdse nadere invulling van activiteiten mogelijk. Dit verslag beschrijft een aantal onderzoeken die hebben plaatsgevonden vanaf de start van dit Actieplan.
Camera vervangt ervaren selecteur
Kamp, J.A.L.M. - \ 2015
Boerderij 100 (2015)36. - ISSN 0006-5617 - p. 50 - 53.
akkerbouw - aardappelen - vermeerderingsmateriaal - detectie - monitoring - diagnostische technieken - fotometrie - pootaardappelen - kwaliteit - kunstmatige selectie - gewasbescherming - precisielandbouw - arable farming - potatoes - propagation materials - detection - diagnostic techniques - photometry - seed potatoes - quality - artificial selection - plant protection - precision agriculture
Selecteren van pootaardappelen kost de teler veel tijd en vergt een hoge mate van vakmanschap. Wellicht kan een machine dat sneller en beter. Daarom start dit jaar het vierjarige project Smart Ziekzoeken Pootaardappelen om te testen of het automatisch opsporen van zieke aardappelplanten haalbaar is. Het project wordt uitgevoerd door Praktijkonderzoek Plant en Omgeving (PPO) en specialisten van Plant Research International (beide onderdeel van Wageningen UR)
DNA-diagnostiek maakt fytosanitaire controles beter en sneller : hightech gereedschap voor inspectie- en keuringsdiensten
Staalduinen, J. van; Bonants, P.J.M. - \ 2015
Onder Glas 12 (2015)6/7. - p. 48 - 49.
glastuinbouw - quarantaine organismen - detectie - technieken - innovaties - analytische methoden - fytosanitaire maatregelen - plantenplagen - polymerase-kettingreactie - landbouwkundig onderzoek - greenhouse horticulture - quarantine organisms - detection - techniques - innovations - analytical methods - phytosanitary measures - plant pests - polymerase chain reaction - agricultural research
Als vooraanstaand in- en exporteur van plantaardig uitgangsmateriaal en eindproducten heeft Nederland ook de taak om ongewenste organismen die met de handelswaar kunnen meereizen buiten of juist binnen de deur te houden. Wageningen UR ontwikkelt samen met partners in binnen- en buitenland nieuwe diagnose- en screeningsmethoden waarmee inspectie- en keuringsdiensten hun taken beter en efficiënter kunnen vervullen. DNA-analyse op de plaats van inspectie speelt daarin een belangrijke rol.
Plantenziektenkundig laboratorium voor elke glastuinbouwteler : On-site detectie voor snel opsporen pathogenen
Bezemer, J. ; Schoen, C.D. - \ 2015
Onder Glas 12 (2015)3. - p. 24 - 25.
glastuinbouw - groenten - tomaten - afwijkingen, planten - tests - testinstallaties - innovaties - detectie - technieken - greenhouse horticulture - vegetables - tomatoes - plant disorders - test rigs - innovations - detection - techniques
Een teler heeft een virus in de kas, maar hij weet niet welk virus precies? Hij heeft last van een aaltje en wil uitzoeken welk aaltje het is? Zijn de vlekjes veroorzaakt door Botrytis of door meeldauw? Binnenkort zorgen telers zelf voor antwoorden op deze vragen. Snel en goedkoop, in de kas.
Detectie en bestrijding van wol- en schildluis in de sierteelt onder glas
Messelink, G.J. ; Leman, A. ; Vijverberg, R. ; Kruidhof, H.M. ; Woning, J. ; Bruin, A. de; Mumm, R. ; Kogel, W.J. de - \ 2015
Wageningen UR Glastuinbouw (Rapport GTB 1339) - 52
glastuinbouw - plantenplagen - sierteelt - glasgroenten - organismen ingezet bij biologische bestrijding - bestrijdingsmethoden - planococcus citri - detectie - methodologie - landbouwkundig onderzoek - greenhouse horticulture - plant pests - ornamental horticulture - greenhouse vegetables - biological control agents - control methods - detection - methodology - agricultural research
Mealybugs and armoured scales are major pest species in ornamental crops in greenhouses. The first part of this report focuses on mealybug detection. The research presented here builds on previous study in which it was shown on laboratory scale that the odour profile released by plants after damage by mealybugs differs from the odour profile released by undamaged plants and plants that suffer from spider mite or mechanical damage. In the present study the change of several compounds in response to mealybug infection was shown to depend on a number of different factors: the growth stage of the plant (flowering/non-flowering), the time of the day sampling took place, the mealybug density and the duration of the mealybug infection. Although in each of the laboratory experiments several plant volatiles were found to significantly differ between mealybug-infested plants and control plants, so far no candidate indicator-volatiles have been found that always reacted significantly and in the same manner to a mealybug infection. The screening of new pesticides showed one pesticide to be effective against both the citrus mealybug Planococcus citri and the rose scale Aulacapsis rosae. Several isolates of entomopathogenic fungi were able to infect mealybugs in the laboratory, but results obtained in the greenhouse were disappointing. Lacewing larvae of the species Chrysoperla lucasina were able to control mealybugs when released repeatedly. The addition of Ephestia eggs disrupted this control in some cases.
PPS project: ontwikkeling diagnostiek plantenziekten Q en K
Bonants, P.J.M. ; Ebskamp, M. ; Kock, M.J.D. de; Kooman, M. - \ 2015
tuinbouw - plantenziekten - gewaskwaliteit - detectie - moleculaire diagnostiek - inspectie - kwaliteitscontroles - diagnose - gewasbescherming - protocollen - conferenties - horticulture - plant diseases - crop quality - detection - molecular diagnostics - inspection - quality controls - diagnosis - plant protection - protocols - conferences
Doelstelling van dit project is de ontwikkeling van kostenefficiënte en gevalideerde moderne (moleculaire) methoden t.b.v. de diagnostiek plantenziekten (Q en K) voor de keuringsdiensten en NVWA, gebruikmakend van de meest innovatieve technologieën en strategieën.
Beheersing aarfusarium en bladvlekkenziekte in zomergerst
Evenhuis, A. ; Schepers, H.T.A.M. - \ 2015
Wageningen : Praktijkonderzoek Plant & Omgeving (Applied Plant Research), part of Wageningen UR Business Unit AGV - 24
akkerbouw - graangewassen - hordeum vulgare - gerst - schimmelziekten - fusarium - gibberella zeae - bladvlekkenziekte - bestrijdingsmethoden - proeven - detectie - fungiciden - arable farming - grain crops - barley - fungal diseases - leaf spotting - control methods - trials - detection - fungicides
Aarfusarium leidt tot kwaliteitsverlies in graangewassen. Aarfusarium in granen wordt veroorzaakt door verschillende ziekteverwekkers van het geslacht Fusarium: De belangrijkste veroorzaker van aarfusarium is F. graminearum. De schimmel infecteert de aar tijdens de bloeiperiode, onder vochtige omstandigheden. Is het tijdens de bloei droog dan is er weinig kans op Fusarium. Is het tijdens en voor de bloei nat dan vergroot dat de kans op aarfusarium. Als een partij tarwe of gerst te zwaar geïnfecteerd is kan dat leiden tot een lagere bakkwaliteit, respectievelijk een lagere brouwkwaliteit. In opdracht van het Productschap Akkerbouw is onderzoek gedaan naar de bestrijding van Fusarium in de teelt van brouwgerst. Het onderzoek is uitgevoerd in samenwerking met de gewasbeschermingsindustrie.
Eindrapportage: Bedrijven voor Bijen
Cornelissen, B. ; Alebeek, F.A.N. van; Berg, W. van den - \ 2015
Wageningen : Plant Research International, Wageningen UR - 46
apidae - wilde bijenvolken - detectie - drachtplanten - biodiversiteit - bedrijventerreinen - stadsomgeving - openbaar groen - bestuivers (dieren) - participatie - wilde bloemen - insecten - wild honey bee colonies - detection - pollen plants - biodiversity - business parks - urban environment - public green areas - pollinators - participation - wild flowers - insects
In het project “Bedrijven voor Bijen” (2012 – 2014) hebben verschillende partijen, waaronder De Gasunie en Wageningen UR, onderzocht hoe en met welke maatregelen populaties van bijen op bedrijventerreinen en in industriële infrastructuur versterkt kunnen worden. Het onderzoek bestaat uit drie onderzoekslijnen: a) Bijen op leidingtracés van de Gasunie, b) Bijen in de stad en c) beheer van gazons voor bestuivers. Dit rapport beschrijft de resultaten van de drie studies.
Improving obstacle awareness for robotic harvesting of sweet-pepper
Bac, C.W. - \ 2015
University. Promotor(en): Eldert van Henten, co-promotor(en): Jochen Hemming. - Wageningen : Wageningen University - ISBN 9789462571808 - 186
robots - oogsten - paprika's - obstructie - detectie - spectraalanalyse - beeldverwerking - simulatie - kassen - harvesting - sweet peppers - obstruction - detection - spectral analysis - image processing - simulation - greenhouses

Abstract

Obstacles are densely spaced in a sweet-pepper crop and they limit the free workspace for a robot that can detach the fruit from the plant. Previous harvesting robots mostly attempted to detach a fruit without using any information of obstacles, thereby reducing the harvest success and damaging the fruit and plant. The hypothesis evaluated in this research is that a robot capable of distinguishing between hard and soft obstacles, and capable of employing this knowledge, improves harvest success and decreases plant damages during harvesting. In line with this hypothesis, the main objective was to develop a sweet-pepper harvesting robot capable of distinguishing between hard and soft obstacles, and of employing this knowledge.

As a start, the thesis describes the crop environment of a harvesting robot, reviews all harvesting robots developed for high-value crops, and defines challenges for future development. Based on insights from this review, we explored the ability to distinguish five plant parts. A multi-spectral imaging set-up and artificial lighting were developed and pixels were classified using a decision tree classifier and a feature selection algorithm. Classification performance was found insufficient and therefore post-processing methods were employed to enhance performance and detect plant parts on a blob basis. Still, performance was found insufficient and a focussed study was conducted on stem localization. The imaging set-up and algorithm developed for stem localization were used to provide real stem locations for motion planning simulations. To address the motion planning problem, we developed a new method of selecting the grasp pose of the end-effector. The new method and the stem localization algorithm were both integrated in the harvesting robot, and we tested their contribution to performance. This research is the first to report a performance evaluation of a sweet-pepper harvesting robot tested under greenhouse conditions. The robot was able to harvest sweet-peppers in a commercial greenhouse, but at limited success rates: harvest success was 6% when the Fin Ray end-effector was mounted, and 2% when the Lip-type end-effector was mounted. After simplifying the crop, by removal of fruit clusters and occluding leaves, harvest success was 26% (Fin Ray) and 33% (Lip-Type). Hence, these properties of the crop partly caused the low performance. The cycle time per fruit was commonly 94 s, i.e. a factor of 16 too long compared with an economically feasible time of 6 s. Several recommendations were made to bridge the gap in performance. Additionally, the robot’s novel functionality of stem-dependant determination of the grasp pose was evaluated to respond to the hypothesis.

Testing the effect of enabling stem-dependent determination of the grasp pose revealed that, in a simplified crop, grasp success increased from 41% to 61% for the Lip-type end-effector, and stem damage decreased from 19% to 13% for the Fin Ray end-effector. Although these effects seem large, they were not statistically significant and therefore resulted in rejection of the hypothesis. To re-evaluate significance of the effects, more samples should be tested in future work.

In conclusion, this PhD research improves the obstacle awareness for robotic harvesting of sweet-pepper by the robot’s capability of perceiving and employing hard obstacles (plant stems), whereas previous harvesting robots either lumped all obstacles in one obstacle class, or did not perceive obstacles. This capability may serve as useful generic functionality for future robots.

LUMINEX®: fast fluorescent detection : multiplex detection for the agricultural and food industries
Bergervoet, J.H.W. ; Currie, H.T. - \ 2014
precisielandbouw - teeltsystemen - gewasbescherming - voedselgewassen - detectie - enzymimmunoassay - elisa - immunoassay - voedselveiligheid - fluorescentie - precision agriculture - cropping systems - plant protection - food crops - detection - enzyme immunoassay - food safety - fluorescence
Luminex®: Detection of mycotoxins, pathogenic fungi, proteins, DNA/RNA
Interactie tussen varroa en omgevingsfactoren. Bijennieuws 28
Blacquière, T. ; Cornelissen, B. ; Dooremalen, C. van; Steen, J.J.M. van der - \ 2014
Wageningen : Bijen@wur
apidae - honingbijen - bijensterfte - doodsoorzaken - factoranalyse - milieufactoren - technieken - detectie - wetenschappelijk onderzoek - honey bees - bee mortality - causes of death - factor analysis - environmental factors - techniques - detection - scientific research
Het probleem van de sterfte van bijenvolken is multifactorieel. Allerlei factoren kunnen soms een beetje of soms zelfs sterk negatieve uitwerking hebben op bijenvolken, en die negatieve uitwerking kan in principe bijdragen aan de bijensterfte. Sommige factoren komen ook nog hand in hand (varroa en sommige virussen). Zolang de relatieve bijdrage van factoren niet bekend is kunnen we maar beter uitgaan van en rekening houden met een mogelijke bijdrage en ondertussen de factoren waar we alvast iets aan kunnen doen zo gunstig mogelijk te maken
Bestrijding van Phytophthora-vruchtrot bij peer (Conference)
Wenneker, M. ; Werd, H.A.E. de; Pham, K.T.K. - \ 2014
Randwijk : Praktijkonderzoek Plant & Omgeving, Business Unit Bloembollen, Boomkwekerij en Fruit - 22
peren - pyrus communis - phytophthora - vruchtrot - plantenziekten - aantasting - detectie - methodologie - bodemschimmels - real time pcr - bestrijdingsmethoden - ziekteoverdracht - pears - fruit rots - plant diseases - infestation - detection - methodology - soil fungi - control methods - disease transmission
De afgelopen jaren werd op verschillende perenpercelen (zware) aantasting met Phytophthora-vruchtrot vastgesteld. Ook in de bewaring werd aantasting van Phytophthora geconstateerd. Naar aanleiding daarvan is een project gestart met de volgende doelstellingen: • Het leveren van basiskennis over de epidemiologie en infectiewijze van Phytophthora bij peer. • Aanzet voor ontwikkelen van mogelijke bestrijdingsstrategiën voor Phytophthora-vruchtrot.
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