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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    Fermented infant formula (with Bifidobacterium breve C50 and Streptococcus thermophilus O65) with prebiotic oligosaccharides is safe and modulates the gut microbiota towards a microbiota closer to that of breastfed infants
    Béghin, Laurent ; Tims, Sebastian ; Roelofs, Mieke ; Rougé, Carole ; Oozeer, Raish ; Rakza, Thameur ; Chirico, Gaetano ; Roeselers, Guus ; Knol, Jan ; Rozé, Jean Christophe ; Turck, Dominique - \ 2020
    Clinical Nutrition (2020). - ISSN 0261-5614
    Early-life microbiota - Fermented formula - Healthy term infants - Postbiotics - Prebiotics - Secretory IgA

    Background & aims: Microbiome-modulators can help positively steer early-life microbiota development but their effects on microbiome functionality and associated safety and tolerance need to be demonstrated. We investigated the microbiome impact of a new combination of bioactive compounds, produced by the food-grade microorganisms Bifidobacterium breve C50 and Streptococcus thermophilus ST065 during a fermentation process, and prebiotics in an infant formula. Tolerance and safety were also assessed. Methods: An exploratory prospective, randomized, double-blind, controlled, multi-centre study was designed to investigate the effect of bioactive compounds and prebiotics (short-chain galacto-oligosaccharides (scGOS)/long-chain fructo-oligosaccharides (lcFOS) 9:1). Experimental formulas containing these bioactive compounds and prebiotics (FERM/scGOS/lcFOS), prebiotics (scGOS/lcFOS), or bioactive compounds (FERM), were compared to a standard cow's milk-based control formula (Control). Exclusively breastfed infants were included as a reference arm since exclusive breastfeeding is considered as the optimal feeding for infants. The study lasted six months and included visits to health care professionals at baseline, two, four and six months of age. Stool SIgA concentration was the primary study outcome parameter. Results: There were 280 infants randomized over the experimental arms and 70 infants entered the breastfed-reference arm. Demographics were balanced, growth and tolerance parameters were according to expectation and adverse events were limited. At four months of age the median SIgA concentration in the FERM/scGOS/lcFOS group was significantly higher compared to the Control group (p = 0.03) and was more similar to the concentrations found in the breastfed-reference group. Bifidobacterium increased over time in all groups. The FERM/scGOS/lcFOS combination resulted in a microbiota composition and metabolic activity closer to the breastfed infants’ microbiome. Conclusion: The FERM/scGOS/lcFOS combination showed a significant positive effect on SIgA levels. All formulas tested were associated with normal growth and were well-tolerated. Additionally, at four months of age the FERM/scGOS/lcFOS formula brought the microbiome composition and metabolic activity closer towards that of breastfed infants. Clinical trial registry: Registration number NTR2726 (Netherlands Trial Register;

    Good taste or gut feeling? A new method in rats shows oro-sensory stimulation and gastric distention generate distinct and overlapping brain activation patterns
    Roelofs, Theresia J.M. ; Luijendijk, Mieneke C.M. ; Toorn, Annette van der; Camps, Guido ; Smeets, Paul A.M. ; Dijkhuizen, Rick M. ; Adan, Roger A.H. - \ 2020
    International Journal Eating Disorders (2020). - ISSN 0276-3478
    functional magnetic resonance imaging - functional neuroimaging - rats - satiation - stomach - taste

    Satiation is influenced by a variety of signals including gastric distention and oro-sensory stimulation. Here we developed a high-field (9.4 T) functional magnetic resonance imaging (fMRI) protocol to test how oro-sensory stimulation and gastric distention, as induced with a block-design paradigm, affect brain activation under different states of energy balance in rats. Repeated tasting of sucrose induced positive and negative fMRI responses in the ventral tegmental area and septum, respectively, and gradual neural activation in the anterior insula and the brain stem nucleus of the solitary tract (NTS), as revealed using a two-level generalized linear model-based analysis. These unique findings align with comparable human experiments, and are now for the first time identified in rats, thereby allowing for comparison between species. Gastric distention induced more extensive brain activation, involving the insular cortex and NTS. Our findings are largely in line with human studies that have shown that the NTS is involved in processing both visceral information and taste, and anterior insula in processing sweet taste oro-sensory signals. Gastric distention and sucrose tasting induced responses in mesolimbic areas, to our knowledge not previously detected in humans, which may reflect the rewarding effects of a full stomach and sweet taste, thereby giving more insight into the processing of sensory signals leading to satiation. The similarities of these data to human neuroimaging data demonstrate the translational value of the approach and offer a new avenue to deepen our understanding of the process of satiation in healthy people and those with eating disorders.

    Surface coating and particle size are main factors explaining the transcriptome-wide responses of the earthworm : Lumbricus rubellus to silver nanoparticles
    Roelofs, Dick ; Makama, Sunday ; Boer, Tjalf E. De; Vooijs, Riet ; Gestel, Cornelis A.M. Van; Brink, Nico W. Van Den - \ 2020
    Environmental Science: Nano covers the benefits... 7 (2020)4. - ISSN 2051-8153 - p. 1179 - 1193.

    Due to the unique properties of differently sized and coated silver nanoparticles (AgNPs), they are used in important industrial and biomedical applications. However, their environmental fate in soil ecosystems and potential mechanisms of toxicity remain elusive, especially at the level of transcriptional regulation. We investigated the transcriptome-wide responses of the earthworm Lumbricus rubellus exposed to nine AgNPs differing in surface coating/charge (bovine serum albumin/negative AgNP_BSA, chitosan/positive AgNP_Chit, and polyvinylpyrrolidone/neutral AgNP_PVP) and sizes (20, 35 and 50 nm) at concentrations close to the EC50 value related to reproduction. AgNO3 was used in two concentrations to benchmark the AgNP effects against those of the Ag salt. A correlation was observed between the number of differentially expressed genes (DEGs) and Ag internal body concentration. Only metallothionein was regulated by all treatments. Medium sized AgNPs caused the most pronounced transcriptional responses, while AgNO3 affected the transcriptome less. Medium sized AgNP_BSA exposure caused the most extensive transcriptional responses with 684 DEGs. Gene ontology enrichment analysis of medium sized AgNP_BSA affected DEGs revealed that mitochondrial electron transport, autophagy and phagocytosis, mesoderm and heart development and microtubule organisation were affected. This was also confirmed by gene set enrichment for KEGG pathway analysis, indicating that phagocytosis, autophagy and signalling pathways related to mesoderm formation were significantly up regulated. All AgNP_BSA and AgNP_PVP exposures caused severe down regulation of ribosomal translation, suggesting that the high energy-demanding protein synthesis process is inhibited. Our data confirm the mechanisms previously identified among other animal models and human cell lines. To conclude, coating formulation and particle size severely impact transcriptional responses at a particular nanoparticle size, suggesting diverse mechanistic responses depending on the coating type.

    Discrimination learning and judgment bias in low birth weight pigs
    Roelofs, Sanne ; Alferink, Floor A.C. ; Ipema, Allyson F. ; Pas, Tessa van de; Staay, Franz Josef van der; Nordquist, Rebecca E. - \ 2019
    Animal Cognition 22 (2019)5. - ISSN 1435-9448 - p. 657 - 671.
    Ambiguity - Birth weight - Cognition - Cognitive bias - Emotion - Pigs

    Low birth weight (LBW) is a risk factor for cognitive and emotional impairments in humans. In pigs, LBW is a common occurrence, but its effects on cognition and emotion have received only limited scientific attention. To assess whether LBW pigs suffer from impaired cognitive and emotional development, we trained and tested 21 LBW and 21 normal birth weight (NBW) pigs in a judgment bias task. Judgment bias is a measure of emotional state which reflects the influence of emotion on an animal’s interpretation of ambiguous stimuli. Pigs were trained to perform a specific behavioral response to two auditory stimuli, predicting either a positive or negative outcome. Once pigs successfully discriminated between these stimuli, they were presented with intermediate, ambiguous stimuli. The pigs’ responses to ambiguous stimuli were scored as optimistic (performance of ‘positive’ response) or pessimistic (performance of ‘negative’ response). Optimistic or pessimistic interpretation of an ambiguous stimulus is indicative of a positive or negative emotional state, respectively. We found LBW pigs to require more discrimination training sessions than NBW pigs to reach criterion performance, suggesting that LBW causes a mild cognitive impairment in pigs. No effects of LBW on judgment bias were found, suggesting a similar emotional state for LBW and NBW pigs. This was supported by comparable salivary and hair cortisol concentrations for both groups. It is possible the enriched housing conditions and social grouping applied during our study influenced these results.

    Effects of parity and litter size on cortisol measures in commercially housed sows and their offspring
    Roelofs, Sanne ; Godding, Lisa ; Haan, Jeanne R. de; Staay, Franz Josef van der; Nordquist, Rebecca E. - \ 2019
    Physiology and Behavior 201 (2019). - ISSN 0031-9384 - p. 83 - 90.
    Birth weight - Hair cortisol - Pigs - Salivary cortisol - Stress

    Breeding sows are regularly exposed to on-farm stressors throughout the duration of their production period. The impact of such stressors may differ for primi- and multiparous sows, as sows could learn to cope with stressors as they gain experience with them. If parity affects stress in sows, it may also impact their prenatal offspring through differential maternal stress. In addition to parity, litter size is another potential factor involved in stress of sows and piglets. Larger litters may be a source of discomfort for gestating sows, while it can result in intra-uterine growth restriction of piglets. In the current study, we aimed to assess whether parity and litter size affect cortisol measures in breeding sows and their offspring. To do this, we measured salivary cortisol concentrations of 16 primiparous and 16 multiparous sows at three time points: 1) while sows were group housed, 2) after sows were separated from the group prior to moving to the farrowing unit and 3) after handling procedures. In addition, hair cortisol concentration was determined for the sows during late gestation and for their low birth weight (n = 63) and normal birth weight (n = 43) offspring on day 3 after birth, to reflect in-utero cortisol exposure. It was expected that if sows adapt to on-farm stressors, the more experienced, multiparous sows would show decreased stress responses in comparison to primiparous sows. However, we found a comparable acute stress response of primi- and multiparous sows to separation from the group. Handling procedures did not influence sows’ salivary cortisol concentrations. Sows’ hair cortisol concentration was positively correlated with litter size. Future research is needed to assess whether this finding reflects increased stress in sows carrying larger litters. Parity or litter size did not have a direct effect on their offspring's hair cortisol concentration. Larger litters did have a higher occurrence of low birth weight piglets. For these piglets, females had higher neonatal hair cortisol concentrations than males. Overall, our results indicate that breeding sows do not adapt to all on-farm stressors. In addition, litter size may influence HPA axis activity in both sows and piglets.

    Cross continental increase in methane ebullition under climate change
    Aben, Ralf C.H. ; Barros, Nathan ; Donk, Ellen Van; Frenken, Thijs ; Hilt, Sabine ; Kazanjian, Garabet ; Lamers, Leon P.M. ; Peeters, Edwin T.H.M. ; Roelofs, Jan G.M. ; Senerpont Domis, Lisette N. De; Stephan, Susanne ; Velthuis, Mandy ; De Waal, Dedmer B. Van; Wik, Martin ; Thornton, Brett F. ; Wilkinson, Jeremy ; Delsontro, Tonya ; Kosten, Sarian - \ 2017
    Nature Communications 8 (2017)1. - ISSN 2041-1723
    Methane (CH4) strongly contributes to observed global warming. As natural CH4 emissions mainly originate from wet ecosystems, it is important to unravel how climate change may affect these emissions. This is especially true for ebullition (bubble flux from sediments), a pathway that has long been underestimated but generally dominates emissions. Here we show a remarkably strong relationship between CH4 ebullition and temperature across a wide range of freshwater ecosystems on different continents using multi-seasonal CH4 ebullition data from the literature. As these temperature-ebullition relationships may have been affected by seasonal variation in organic matter availability, we also conducted a controlled year-round mesocosm experiment. Here 4 °C warming led to 51% higher total annual CH4 ebullition, while diffusion was not affected. Our combined findings suggest that global warming will strongly enhance freshwater CH4 emissions through a disproportional increase in ebullition (6-20% per 1 °C increase), contributing to global warming.
    Kansen voor 'Hospital Gardening' rond Streekziekenhuis Koningin Beatrix Winterswijk
    Ravesloot, M.B.M. ; Hassink, J. ; Heiden, Alma van der; Roelofs, P.F.M.M. - \ 2017
    Wageniningen University & Research, Bloembollen, Boomkwekerij & Fruit - 58 p.
    Coping with living in the soil : The genome of the parthenogenetic springtail Folsomia candida
    Faddeeva-Vakhrusheva, Anna ; Kraaijeveld, Ken ; Derks, Martijn F.L. ; Anvar, Seyed Yahya ; Agamennone, Valeria ; Suring, Wouter ; Kampfraath, Andries A. ; Ellers, Jacintha ; Ngoc, Giang Le; Gestel, Cornelis A.M. van; Mariën, Janine ; Smit, Sandra ; Straalen, Nico M. van; Roelofs, Dick - \ 2017
    BMC Genomics 18 (2017). - ISSN 1471-2164 - 14 p.
    Carbohydrate metabolism - Collembola - Gene family expansions - Genome collinearity - Horizontal gene transfer - Hox genes - Intragenomic rearrangement - Palindrome

    Background: Folsomia candida is a model in soil biology, belonging to the family of Isotomidae, subclass Collembola. It reproduces parthenogenetically in the presence of Wolbachia, and exhibits remarkable physiological adaptations to stress. To better understand these features and adaptations to life in the soil, we studied its genome in the context of its parthenogenetic lifestyle. Results: We applied Pacific Bioscience sequencing and assembly to generate a reference genome for F. candida of 221.7 Mbp, comprising only 162 scaffolds. The complete genome of its endosymbiont Wolbachia, was also assembled and turned out to be the largest strain identified so far. Substantial gene family expansions and lineage-specific gene clusters were linked to stress response. A large number of genes (809) were acquired by horizontal gene transfer. A substantial fraction of these genes are involved in lignocellulose degradation. Also, the presence of genes involved in antibiotic biosynthesis was confirmed. Intra-genomic rearrangements of collinear gene clusters were observed, of which 11 were organized as palindromes. The Hox gene cluster of F. candida showed major rearrangements compared to arthropod consensus cluster, resulting in a disorganized cluster. Conclusions: The expansion of stress response gene families suggests that stress defense was important to facilitate colonization of soils. The large number of HGT genes related to lignocellulose degradation could be beneficial to unlock carbohydrate sources in soil, especially those contained in decaying plant and fungal organic matter. Intra- as well as inter-scaffold duplications of gene clusters may be a consequence of its parthenogenetic lifestyle. This high quality genome will be instrumental for evolutionary biologists investigating deep phylogenetic lineages among arthropods and will provide the basis for a more mechanistic understanding in soil ecology and ecotoxicology.

    The gut microbiota as a modulator of innate immunity during melioidosis
    Lankelma, Jacqueline M. ; Birnie, Emma ; Weehuizen, Tassili A.F. ; Scicluna, Brendon P. ; Belzer, Clara ; Houtkooper, Riekelt H. ; Roelofs, Joris J.T.H. ; Vos, Alex F. de; Poll, Tom van der; Budding, Andries E. ; Wiersinga, W.J. - \ 2017
    PLoS Neglected Tropical Diseases 11 (2017)4. - ISSN 1935-2727
    Background: Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is an emerging cause of pneumonia-derived sepsis in the tropics. The gut microbiota supports local mucosal immunity and is increasingly recognized as a protective mediator in host defenses against systemic infection. Here, we aimed to characterize the composition and function of the intestinal microbiota during experimental melioidosis. Methodology/Principal findings: C57BL/6 mice were infected intranasally with B. pseudomallei and sacrificed at different time points to assess bacterial loads and inflammation. In selected experiments, the gut microbiota was disrupted with broad-spectrum antibiotics prior to inoculation. Fecal bacterial composition was analyzed by means of IS-pro, a 16S-23S interspacer region-based profiling method. A marked shift in fecal bacterial composition was seen in all mice during systemic B. pseudomallei infection with a strong increase in Proteobacteria and decrease in Actinobacteria, with an increase in bacterial diversity. We found enhanced early dissemination of B. pseudomallei and systemic inflammation during experimental melioidosis in microbiota-disrupted mice compared with controls. Whole-genome transcriptional profiling of the lung identified several genes that were differentially expressed between mice with a normal or disrupted intestinal microbiota. Genes involved in acute phase signaling, including macrophage-related signaling pathways were significantly elevated in microbiota disrupted mice. Compared with controls, alveolar macrophages derived from antibiotic pretreated mice showed a diminished capacity to phagocytose B. pseudomallei. This might in part explain the observed protective effect of the gut microbiota in the host defense against pneumonia-derived melioidosis. Conclusions/Significance: Taken together, these data identify the gut microbiota as a potential modulator of innate immunity during B. pseudomallei infection.
    HIPPIE: High Performance Polymers from Isoidide
    Hagberg, E. ; Poppe, Ernst ; Roelofs, Jules ; Knoop, J.R.I. - \ 2016
    There is a general need for biobased polymers with improved properties compared to the current commercial biobased polymers. In particular there is a need for biobased materials with improved thermal and mechanical properties, comparable with (or superior to) current petrochemical based engineering plastics, like polyethylene terephthalate (PET), polybutylene terephthalate (PBT) or polycarbonate (PC). Such materials are not only suitable for packaging applications, but also for more demanding applications like (consumer) electronics, automotive, building & construction, where properties high temperature performance, high strength, impact resistance, or optical transparency are required.
    Gene Family Evolution Reflects Adaptation to Soil Environmental Stressors in the Genome of the Collembolan Orchesella cincta
    Faddeeva-Vakhrusheva, Anna ; Derks, M.F.L. ; Anvar, Seyed Yahya ; Agamennone, Valeria ; Suring, Wouter ; Smit, S. ; Straalen, Nico M. van; Roelofs, Dick - \ 2016
    Genome Biology and Evolution 8 (2016)7. - ISSN 1759-6653 - p. 2106 - 2117.
    Collembola (springtails) are detritivorous hexapods that inhabit the soil and its litter layer. The ecology of the springtail Orchesella cincta is extensively studied in the context of adaptation to anthropogenically disturbed areas. Here, we present a draft genome of an O. cincta reference strain with an estimated size of 286.8 Mbp, containing 20,249 genes. In total, 446 gene families are expanded and 1,169 gene families evolved specific to this lineage. Besides these gene families involved in general biological processes, we observe gene clusters participating in xenobiotic biotransformation. Furthermore, we identified 253 cases of horizontal gene transfer (HGT). Although the largest percentage of them originated from bacteria (37.5%), we observe an unusually high percentage (30.4%) of such genes of fungal origin. The majority of foreign genes are involved in carbohydrate metabolism and cellulose degradation. Moreover, some foreign genes (e.g., bacillopeptidases) expanded after HGT. We hypothesize that horizontally transferred genes could be advantageous for food processing in a soil environment that is full of decaying organic material. Finally, we identified several lineage-specific genes, expanded gene families, and horizontally transferred genes, associated with altered gene expression as a consequence of genetic adaptation to metal stress. This suggests that these genome features may be preadaptations allowing natural selection to act on. In conclusion, this genome study provides a solid foundation for further analysis of evolutionary mechanisms of adaptation to environmental stressors.
    Early-Life events, including mode of delivery and type of feeding, siblings and gender, shape the developing gut microbiota
    Martin, Rocio ; Makino, Hiroshi ; Yavuz, Aysun Cetinyurek ; Ben-Amor, Kaouther ; Roelofs, Mieke ; Ishikawa, Eiji ; Kubota, Hiroyuki ; Swinkels, Sophie ; Sakai, Takafumi ; Oishi, Kenji ; Kushiro, Akira ; Knol, Jan - \ 2016
    PLoS ONE 11 (2016)6. - ISSN 1932-6203

    Colonization of the infant gut is believed to be critically important for a healthy growth as it influences gut maturation, metabolic, immune and brain development in early life. Understanding factors that influence this process is important, since an altered colonization has been associated with a higher risk of diseases later in life. Fecal samples were collected from 108 healthy neonates in the first half year of life. The composition and functionality of the microbiota was characterized by measuring 33 different bacterial taxa by qPCR/RT qPCR, and 8 bacterial metabolites. Information regarding gender, place and mode of birth, presence of siblings or pets; feeding pattern and antibiotic use was collected by using questionnaires. Regression analysis techniques were used to study associations between microbiota parameters and confounding factors over time. Bacterial DNA was detected in most meconium samples, suggesting bacterial exposure occurs in utero. After birth, colonization by species of Bifidobacterium, Lactobacillus and Bacteroides was influenced by mode of delivery, type of feeding and presence of siblings, with differences found at species level and over time. Interestingly, infant-type bifidobacterial species such as B. breve or B. longum subsp infantis were confirmed as early colonizers apparently independent of the factors studied here, while B. animalis subsp. lactis presence was found to be dependent solely on the type of feeding, indicating that it might not be a common infant gut inhabitant. One interesting and rather unexpected confounding factor was gender. This study contributes to our understanding of the composition of the microbiota in early life and the succession process and the evolution of the microbial community as a function of time and events occurring during the first 6 months of life. Our results provide new insights that could be taken into consideration when selecting nutritional supplementation strategies to support the developing infant gut microbiome.

    The gut microbiota plays a protective role in the host defence against pneumococcal pneumonia
    Schuijt, T.J. ; Lankelma, J.M. ; Scicluna, B.P. ; Melo, F.S. e; Roelofs, J.J. ; Boer, J.D. de; Hoogendijk, A.J. ; Beer, R. de; Vos, A. de; Belzer, C. ; Vos, W.M. de; Poll, T. van der; Wiersinga, W.J. - \ 2016
    Gut 65 (2016). - ISSN 0017-5749 - p. 575 - 583.
    OBJECTIVE: Pneumonia accounts for more deaths than any other infectious disease worldwide. The intestinal microbiota supports local mucosal immunity and is increasingly recognised as an important modulator of the systemic immune system. The precise role of the gut microbiota in bacterial pneumonia, however, is unknown. Here, we investigate the function of the gut microbiota in the host defence against Streptococcus pneumoniae infections. DESIGN: We depleted the gut microbiota in C57BL/6 mice and subsequently infected them intranasally with S. pneumoniae. We then performed survival and faecal microbiota transplantation (FMT) experiments and measured parameters of inflammation and alveolar macrophage whole-genome responses. RESULTS: We found that the gut microbiota protects the host during pneumococcal pneumonia, as reflected by increased bacterial dissemination, inflammation, organ damage and mortality in microbiota-depleted mice compared with controls. FMT in gut microbiota-depleted mice led to a normalisation of pulmonary bacterial counts and tumour necrosis factor-a and interleukin-10 levels 6 h after pneumococcal infection. Whole-genome mapping of alveolar macrophages showed upregulation of metabolic pathways in the absence of a healthy gut microbiota. This upregulation correlated with an altered cellular responsiveness, reflected by a reduced responsiveness to lipopolysaccharide and lipoteichoic acid. Compared with controls, alveolar macrophages derived from gut microbiota-depleted mice showed a diminished capacity to phagocytose S. pneumoniae. CONCLUSIONS: This study identifies the intestinal microbiota as a protective mediator during pneumococcal pneumonia. The gut microbiota enhances primary alveolar macrophage function. Novel therapeutic strategies could exploit the gut-lung axis in bacterial infections
    Profitability of the Dutch growing system of 'Conference'
    Heijerman-Peppelman, Gondy ; Roelofs, P.F.M.M. ; Groot, M.J. - \ 2015
    In: Acta Horticulturae International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462610927 - p. 233 - 238.
    'Conference' - Economic profitability - Establishment costs - Growing system - Pyrus communis L. - The Netherlands - Unit cost - Yield

    During the past years the common growing system of 'Conference' pear in The Netherlands has intensified from 2,500 to 3,000 trees ha-1. At present, the common planting distance for the standard planting system is 3.25×1 m. Production costs are relatively high in The Netherlands. The main reason for this is the high labour cost, which concerns one third of the total production cost. In order to get a profitable growing system for pear, high yields are needed especially during the first five growing years. To achieve these higher early yields a number of cultural practices were improved. For instance drip irrigation with fertigation was optimised. The quality of the nursery trees and the higher density of trees are also important factors to achieve high early yields. These measures resulted in higher investment costs, but due to higher yields in the first five growing years also to lower establishment costs due to a shorter establishment period. Due to the higher yields the total unit cost per kg 'Conference' pears in The Netherlands was reduced with 2 €cent per kg.

    Dropsa: Ex-ante economic analysis of proposed strategies for D. suzukii and Psa
    Groot, M.J. ; Roelofs, P.F.M.M. - \ 2015
    Randwijk : Praktijkonderzoek Plant en Omgeving, Bloembollen, Boomkwekerij en Fruit - 17 p.
    Biofumigation using a wild Brassica oleracea accession with high glucosinolate content affects beneficial soil
    Zuluaga, D.L. ; Ommen Kloeke van, A.E.E. ; Verkerk, R. ; Röling, W.F.M. ; Ellers, J. ; Roelofs, D. ; Aarts, M.G.M. - \ 2015
    Plant and Soil 394 (2015). - ISSN 0032-079X - p. 155 - 163.
    chemical diversity - gene-expression - indian mustard - natural toxin - life-history - isothiocyanates - collembola - release - defense - tissues
    Aims This study explores the biofumigation effects of glucosinolate (GSL) containing Brassica oleracea plant material on beneficial, non-target soil organisms, and aims to relate those effects to differences in GSL profiles. Methods Leaf material of purple sprouting broccoli ‘Santee’, Savoy cabbage ‘Wintessa’, and the wild B. oleracea accession Winspit was analysed for GSL production and used for biofumigation experiments on the beneficial soil invertebrates, Folsomia candida (springtail) and Eisenia andrei (earthworm) and the soil bacterial community. Results When mixed into soil, the Winspit plant material exerted the highest toxic effects on beneficial soil invertebrates by reducing survival and reproduction. Total GSL levels varied substantially between genotypes, in particular the aliphatic GSL (AGSL) sinigrin and gluconapin being highly abundant or exclusively present in Winspit. Differences between the genotypes regarding biofumigation effects on the soil microbial community were only observed on a temporal basis with the largest difference in bacterial community structure after 1 week. Conclusions The high total GSL content in biofumigated soil could explain the toxicity of Winspit for soil invertebrates. These effects are likely to be the results of high AGSL levels in Winspit. The use of wild B. oleracea crops, such asWinspit, for biofumigation practices would need a proper assessment of the overall impact on soil biota before being applied on a wide scale
    'Bodemresetten’ bij chrysant geeft beste resultaten in juli
    Garcia Victoria, N. ; Helm, F.P.M. van der; Streminska, M.A. ; Roelofs, T. - \ 2015
    Kas als Energiebron
    Praktijkproef HNT Chrysant
    Raaphorst, M.G.M. ; Weel, P.A. van; Roelofs, T. - \ 2015
    Wageningen : Wageningen UR Glastuinbouw (Rapport GTB 1355) - 48
    glastuinbouw - teelt onder bescherming - chrysanten - vochtigheid - energiebesparing - teeltsystemen - ontvochtiging - temperatuur - greenhouse horticulture - protected cultivation - chrysanthemums - humidity - energy saving - cropping systems - dehumidification - temperature
    A combination of an air handling unit and an additional screen installation, has been tested at the chrysanthemums nursery Arcadia. With this air handling unit the humidity turned out to be controlled very accurately, which provided the opportunity to use less heat and to incrementally accept a higher RV. The combination with an extra screen installation implied 30% less use of heat compared to the adjacent reference site.
    Doorontwikkeling biologische grondontsmetting (bodemresetten) als alternatief voor stomen
    Garcia Victoria, N. ; Helm, F.P.M. van der; Streminska, M.A. ; Roelofs, T. - \ 2015
    Wageningen : Wageningen UR Glastuinbouw (Rapport GTB 1342) - 68
    biologische grondontsmetting - organische stof - grondbewerking - biologische processen - alternatieve methoden - bodemstructuur - glastuinbouw - proeven - energiebesparing - biological soil sterilization - organic matter - tillage - biological processes - alternative methods - soil structure - greenhouse horticulture - trials - energy saving
    Biological Soil Disinfection (BSD) or ‘soil resetting’ can technically, energetically and economically be an effective alternative to soil steaming. The program ‘Greenhouse as energy source’ of the Ministry of Economy, Agriculture and Innovation and the Dutch Horticultural Board gave fi nancial support to practical demonstrations and further development of this technology, in order to stimulate implementation of BSD in practice. Chrysanthemum growers, DLV Plant B.V., Wageningen UR Greenhouse Horticulture and Thatchtec B.V. gained experience with BSD in four chrysanthemums companies. Additional research was conducted into possibilities to speed up the process and fi nd reliable process indicators. The disinfection and cultivation results (up to 5 cycles) was after BSD as good or better as after steaming in 3 of the 4 companies. Anaerobic conditions, one of the prerequisites for disinfection, were not achieved in the fourth company, which may explain the unsatisfactory disinfection. In intensive cultivation, three weeks without cultivation need to be included in the planning. Implementation in July offers the best fi t in terms of effectivity and income.The process can be shortened to 9 days by means of a higher Raw Proteine dose, but this leads to growth inhibition in the next cultivation. Adding a “primer” or “inoculum” with own soil bacteria does not suffi ciently increase the operational reliability, and is therefore deleted as a process step in the protocol. The disinfection process can be well monitored by means of oxygen measurement and total nematode counts. Additional indicators are the concentrations of nitrate, ammonium and bicarbonate in the 1:2 soil volume extract.
    New approaches to uncertainty analysis for use in aggregate and cumulative risk assessment of pesticides
    Kennedy, M.C. ; Voet, H. van der; Roelofs, V.J. ; Roelofs, W. ; Glass, C.R. ; Boer, W.J. de; Kruisselbrink, J.W. ; Hart, A.D.M. - \ 2015
    Food and Chemical Toxicology 79 (2015). - ISSN 0278-6915 - p. 54 - 64.
    residential exposure - modeling framework - dietary
    Risk assessments for human exposures to plant protection products (PPPs) have traditionally focussed on single routes of exposure and single compounds. Extensions to estimate aggregate (multi-source) and cumulative (multi-compound) exposure from PPPs present many new challenges and additional uncertainties that should be addressed as part of risk analysis and decision-making. A general approach is outlined for identifying and classifying the relevant uncertainties and variabilities. The implementation of uncertainty analysis within the MCRA software, developed as part of the EU-funded ACROPOLIS project to address some of these uncertainties, is demonstrated. An example is presented for dietary and non-dietary exposures to the triazole class of compounds. This demonstrates the chaining of models, linking variability and uncertainty generated from an external model for bystander exposure with variability and uncertainty in MCRA dietary exposure assessments. A new method is also presented for combining pesticide usage survey information with limited residue monitoring data, to address non-detect uncertainty. The results show that incorporating usage information reduces uncertainty in parameters of the residue distribution but that in this case quantifying uncertainty is not a priority, at least for UK grown crops. A general discussion of alternative approaches to treat uncertainty, either quantitatively or qualitatively, is included.
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