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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    Data presented in the PhD thesis "Cucumber Mildew Resistance Identification of Cucumber Genes Involved in Susceptibility and Resistance to Powdery and Downy Mildew"
    Berg, J.A. - \ 2019
    Wageningen University & Research
    cucumber - downy mildew - plant-pathogen interactions - powdery mildew - susceptibility genes
    The aims of this thesis were to identify genes involved in cucumber-mildew interactions, in order to better understand these pathosystems, thus providing new leads for the breeding of mildew resistant cucumbers. As resistances against both PM and DM were previously shown to be usually recessive, special attention is given to the concept of susceptibility genes (S genes), loss-of-function alleles of which can contribute to effective and durable resistance.
    Autonomous Greenhouse Challenge, First Edition (2018)
    Hemming, S. ; Zwart, H.F. de; Elings, A. ; Righini, I. ; Petropoulou, Anna - \ 2019
    Wageningen University & Research
    climate set points - crop management - cucumber - greenhouse climate - harvest - irrigation - outside weather - pruning - resource consumption
    The dataset contains data on greenhouse climate, irrigation, outside weather, greenhouse climate set points, harvest and crop management, resource consumption. Data were collected during a 4-month cucumber production (cv. Hi Power) in 6 glasshouse compartments (96 m2), located in Bleiswijk (The Netherlands). The dataset contains raw and processed data. Raw data were collected via climate measuring boxes, climate and irrigation process computer, manual registrations, outside weather station. The dataset was produced during the first edition of Autonomous Greenhouse Challenge, an international competition aiming at using Artificial Intelligence algorithms for the remote control of greenhouse horticulture production. Five international teams consisting of scientists, professionals and students participated in this experiment. The teams' names are: iGrow, deep_greens, AiCU, Sonoma, Croperators. They developed AI algorithms to remotely determine the Climate control set points and they additionally sent instructions for the crop pruning strategy. They had to realize the highest yield with minimal use of resources (e.g. water, CO2). The achievements in AI-controlled compartments were compared with a reference compartment, operated manually by three Dutch commercial growers (named Reference).
    Effect of Taste Enhancement on Consumer Acceptance of Pureed Cucumber and Green Capsicum
    Stokkom, Vera L. van; Graaf, Cees de; Kooten, Olaf van; Stieger, Markus - \ 2018
    Journal of Food Science 83 (2018)10. - ISSN 0022-1147 - p. 2578 - 2585.
    acceptance - capsicum - cucumber - taste - vegetable

    Abstract: Vegetables have low taste intensities, which might contribute to low acceptance. The aim of this study was to investigate the effect of taste (sweetness, sourness, bitterness, umami, and saltiness) and fattiness enhancement on consumer acceptance of cucumber and green capsicum purees. Three concentrations of sugar, citric acid, caffeine, mono-sodium glutamate, NaCl, and sunflower oil were added to pureed cucumber and green capsicum. Subjects (n = 66, 35.6 ± 17.7 y) rated taste and fattiness intensity. Different subjects (n = 100, 33.2 ± 16.5 years) evaluated acceptance of all pureed vegetables. Taste intensities of vegetable purees were significantly different (P < 0.05) between the three tastant concentrations except for umami in both vegetable purees, sourness in green capsicum puree, and fattiness in cucumber puree. Only enhancement of sweetness significantly (P < 0.05) increased acceptance of both vegetable purees compared to unmodified purees. In cucumber purees, relatively small amounts of added sucrose (2%) increased acceptance already significantly, whereas in green capsicum acceptance increased significantly only with addition of 5% sucrose. Enhancement of other taste modalities did not significantly increase acceptance of both vegetable purees. Enhancing saltiness and bitterness significantly decreased acceptance of both vegetable purees. We conclude that the effect of taste enhancement on acceptance of vegetable purees differs between tastants and depends on tastant concentration and vegetable type. With the exception of sweetness, taste enhancement of taste modalities such as sourness, bitterness, umami, and saltiness was insufficient to increase acceptance of vegetable purees. We suggest that more complex taste, flavor, or texture modifications are required to enhance acceptance of vegetables. Practical Application: Results can be used by cultivators to select and grow vegetable varieties with enhanced taste and flavor. Especially for cucumber, relatively small sweetness enhancement is sufficient to increase acceptance.

    Functional characterization of cucumber (Cucumis sativus L.) Clade V MLO genes
    Berg, J.A. ; Appiano, Michela ; Bijsterbosch, G. ; Visser, R.G.F. ; Schouten, H.J. ; Bai, Y. - \ 2017
    cucumber - cucumis sativus - powdery mildew - MLO - susceptiblity genes - gene expression
    Seed and leaf treatments with natural compounds to induce resistance against Peronospora parasitica in Brassica oleracea
    Wolf, J.M. van der; Michta, A. ; Zouwen, P.S. van der; Boer, W.J. de; Davelaar, E. ; Stevens, L.H. - \ 2012
    Crop Protection 35 (2012). - ISSN 0261-2194 - p. 78 - 84.
    systemic acquired-resistance - induced disease resistance - defense responses - fusarium-wilt - downy mildew - damping-off - plants - protection - cucumber - growth
    Seed and leaf treatments with natural compounds having a low risk profile (LRP) were evaluated for their potential to induce resistance in cabbage plants (Brassica oleracea) against Peronospora parasitica, causal organism of downy mildew. The selection of 34 LRP compounds comprised micronutrients, organic compounds such as proline, riboflavin, oligogalacturonides, aminolignosulfonates, bacterial lipopolysaccharides, and bacterial and fungal extracts. Treatments with the synthetic chemical inducers 2,6-dichloroisonicotinic acid (INA), d,l-ß-aminobutyric acid, salicylic acid, benzothiadiazole and the fungicide Previcur™ were included as controls. After seed treatment a maximum reduction of 27% diseased leaf area was found with an extract of a Lysobacter strain, compared to a reduction of 99% for INA, the most effective synthetic inducer. Seed treatments with extracts of Pectobacterium carotovorum subsp. carotovorum, Bacillus macerans, Pseudomonas syringae, Streptomyces and Xanthomonas campestris strains also reduced downy mildew infection significantly. After leaf treatment, a maximum reduction of 85% was again found with the Lysobacter extract, compared to a reduction of 99% for INA, the most effective synthetic inducer. Leaf treatments with CuSO4 (=1 mM), MnCl2 (=10 mM), K2HPO4 (100 mM), and extracts of P. syringae, P. carotovorum subsp. carotovorum, Streptomyces, X. campestris and B. macerans strains also reduced the diseased leaf area, but CuSO4 was highly phytotoxic. For seed and leaf treatments with Lysobacter extract, proline, MnCl2 and INA the effect on the induction of chitinase and glucanase activity was tested, using two pathogenesis-related proteins as markers for induced resistance. For seed treatments only INA and for leaf treatments INA, proline and MnCl2 treatments resulted in increased activity of both enzymes. The rate of enzyme activity induced by INA was dependent on the time seeds were exposed to the compound. Highlights ¿ Seed treatments with isonicotinic acid protects Brassica seedlings from Peronospora infections. ¿ Treatments of seedlings with extracts of Lysobacter protects against Peronospora infections. ¿ Effect of seed treatments is dependent on the time of incubation with the elicitor
    Estimation of leaf area for large scale phenotyping and modeling of rose genotypes
    Gao, M. ; Heijden, G.W.A.M. van der; Vos, J. ; Eveleens, B.A. ; Marcelis, L.F.M. - \ 2012
    Scientia Horticulturae 138 (2012). - ISSN 0304-4238 - p. 227 - 234.
    co2 enrichment popface - capsicum-annuum-l - linear measurements - cell expansion - sweet-pepper - elevated co2 - transpiration - environments - temperature - cucumber
    Leaf area is a major parameter in many physiological and plant modeling studies. When we want to use physiological models in plant breeding, we need to measure the leaf area for a large number of genotypes. This requires a fast and non-destructive method. In this study, we investigated whether for cut roses a statistical model of simple measurements of length and width of leaves, together with other information like relative rank and number of leaflets per leaf can provide an unbiased estimate of leaf area across many genotypes and environments. Harvestable shoots of 20 genotypes of cut roses (Rosa hybrida L.) were collected from 4 different commercially operated glasshouses in the Netherlands. Regression analysis of square root of leaf area source versus leaf length, leaf width, and leaflet number revealed several models that showed a high correlation for individual rose leaves. However, the factors genotype and environment were significant (P <0.001) indicating that there is no simple unbiased model across all genotypes and environments. Models ignoring genotypic information showed a 10% over- or underestimation of individual leaf area in at least 4 out of 20 genotypes. When genotype information was included in the model, good estimates of leaf area (R2 = 0.917, RMSE = 0.592, CV% = 6.7 and AIC = 8907) were obtained based on measurements of leaf width and leaflet number per leaf, so ignoring leaf length. This does require that the model should be calibrated for each specific genotype. For Dutch climate conditions, it was not necessary to calibrate the model per greenhouse environment, although there were considerable differences in leaf size between greenhouses. If the model was validated for total shoot leaf area, instead of individual leaves, similar results were obtained, but with higher accuracy
    The influence of light intensity and leaf age on the photosynthetic capacity of leaves within a tomato canopy
    Trouwborst, G. ; Hogewoning, S.W. ; Harbinson, J. ; Ieperen, W. van - \ 2011
    Journal of Horticultural Science and Biotechnology 86 (2011)4. - ISSN 1462-0316 - p. 403 - 407.
    photon flux-density - alocasia-macrorrhiza - nitrogen nutrition - cucumber - plants - acclimation - senescence - anatomy - yield
    In dense crop stands, the decrease in leaf photosynthetic capacity (Amax) is paralleled by a decrease in photosynthetically active photon flux density (PPFD) and an increase in leaf age. In greenhouse horticulture, assimilation lighting is traditionally applied from above the canopy. Recently a new lighting technique has been developed in which assimilation lighting is applied within the canopy: intracanopy lighting. This development raises the question whether the decrease in the Amax of lower, thus older and shaded, leaves in a crop is solely due to the lower PPFD, or also partly due to ageing of these leaves. We investigated whether leaf ageing influenced changes in the Amax of tomato leaves during their usual life-span during cultivation in commercial crop systems (i.e., up to 70 d). To uncouple leaf age from the PPFD, tomato plants were grown horizontally, so that the PPFD was similar for all leaves. To investigate the effect of PPFD during leaf development (PPFDLD), Amax-leaf age profiles were determined for the leaves of plants grown under conditions with distinctly different natural patterns of PPFD (i.e.,Winter, early Spring, and late Spring). In addition, in half of the plants used per experiment, all fully-developed leaves were shaded to 25% of the normal PPFD in the greenhouse using a neutral density filter. Photosynthetic capacity and chlorophyll contents were higher in late Spring than in Winter, but were hardly affected by leaf age. In early Spring, the Amax and chlorophyll contents were higher in younger leaves than in older leaves. To a large extent, this was due to the differences in PPFDLD, and hardly due to leaf ageing. Shading fully-developed, mature leaves dramatically decreased their Amax and chlorophyll contents within a few days. We conclude that, during the normal 70 d life-span of tomato leaves in commercial cultivation, the decrease in PPFD within the canopy, and not leaf-ageing, is the most important factor causing changes in Amax with canopy depth.
    Indigenous Populations of Three Closely Related Lysobacter spp. in agricultural soils using real-time PCR
    Postma, J. ; Schilder, M.T. ; Hoof, R.A. van - \ 2011
    Microbial Ecology 62 (2011)4. - ISSN 0095-3628 - p. 948 - 958.
    biological-control - enzymogenes christensen - antimicrobial activity - bacterial communities - rhizosphere - rhizoplane - cucumber - diseases - growth - 3.1t8
    Previous research had shown that three closely related species of Lysobacter, i.e., Lysobacter antibioticus, Lysobacter capsici, and Lysobacter gummosus, were present in different Rhizoctonia-suppressive soils. However, the population dynamics of these three Lysobacter spp. in different habitats remains unknown. Therefore, a specific primer–probe combination was designed for the combined quantification of these three Lysobacter spp. using TaqMan. Strains of the three target species were efficiently detected with TaqMan, whereas related non-target strains of Lysobacter enzymogenes and Xanthomonas campestris were not or only weakly amplified. Indigenous Lysobacter populations were analyzed in soils of 10 organic farms in the Netherlands during three subsequent years with TaqMan. These soils differed in soil characteristics and crop rotation. Additionally, Lysobacter populations in rhizosphere and bulk soil of different crops on one of these farms were studied. In acid sandy soils low Lysobacter populations were present, whereas pH neutral clay soils contained high populations (respectively,
    Simulation of fruit-set and trophic competition and optimization of yield advantages in six Xapsicum cultivars using functional-tructural plant modelling
    Ma, Y.T. ; Wubs, A.M. ; Mathieu, A. ; Heuvelink, E. ; Zhu, J.Y. ; Hu, B.G. ; Cournede, P.H. ; Reffye, P. de - \ 2011
    Annals of Botany 107 (2011)5. - ISSN 0305-7364 - p. 793 - 803.
    sweet-pepper - sink strength - annuum-l - growth - abscission - patterns - cucumber - validation - irradiance - components
    Background and aims - Many indeterminate plants can have wide fluctuations in the pattern of fruit-set and harvest. Fruit-set in these types of plants depends largely on the balance between source (assimilate supply) and sink strength (assimilate demand) within the plant. This study aims to evaluate the ability of functional–structural plant models to simulate different fruit-set patterns among Capsicum cultivars through source–sink relationships. Methods - A greenhouse experiment of six Capsicum cultivars characterized with different fruit weight and fruit-set was conducted. Fruit-set patterns and potential fruit sink strength were determined through measurement. Source and sink strength of other organs were determined via the GREENLAB model, with a description of plant organ weight and dimensions according to plant topological structure established from the measured data as inputs. Parameter optimization was determined using a generalized least squares method for the entire growth cycle. Key Results and Conclusions - Fruit sink strength differed among cultivars. Vegetative sink strength was generally lower for large-fruited cultivars than for small-fruited ones. The larger the size of the fruit, the larger variation there was in fruit-set and fruit yield. Large-fruited cultivars need a higher source–sink ratio for fruit-set, which means higher demand for assimilates. Temporal heterogeneity of fruit-set affected both number and yield of fruit. The simulation study showed that reducing heterogeneity of fruit-set was obtained by different approaches: for example, increasing source strength; decreasing vegetative sink strength, source–sink ratio for fruit-set and flower appearance rate; and harvesting individual fruits earlier before full ripeness. Simulation results showed that, when we increased source strength or decreased vegetative sink strength, fruit-set and fruit weight increased. However, no significant differences were found between large-fruited and small-fruited groups of cultivars regarding the effects of source and vegetative sink strength on fruit-set and fruit weight. When the source–sink ratio at fruit-set decreased, the number of fruit retained on the plant increased competition for assimilates with vegetative organs. Therefore, total plant and vegetative dry weights decreased, especially for large-fruited cultivars. Optimization study showed that temporal heterogeneity of fruit-set and ripening was predicted to be reduced when fruits were harvested earlier. Furthermore, there was a 20 % increase in the number of extra fruit set
    Cross-protection or enhanced symptom display in greenhouse tomato co-infected with different Pepino mosaic virus isolates
    Hanssen, I.M. ; Gutiérrez-Aguirre, I. ; Paeleman, A. ; Goen, K. ; Wittemans, L. ; Lievens, B. ; Vanachter, A.C.R.C. ; Ravnikar, M. ; Thomma, B.P.H.J. - \ 2010
    Plant Pathology 59 (2010)1. - ISSN 0032-0862 - p. 13 - 21.
    genomic rna - sequence - protein - population - cucumber - strains - squash - time - uk
    The potential of three mild Pepino mosaic virus (PepMV) isolates, belonging to the CH2, EU and LP genotypes, to protect a tomato (Solanum lycopersicum) crop against an aggressive challenge isolate of the CH2 genotype was assessed in greenhouse trials and PepMV symptoms were rated at regular time points. After challenge infection, enhanced symptom display was recorded in plants that were pre-inoculated with a protector isolate belonging to a different genotype (EU, LP) from the challenge isolate. A quantitative genotype-specific TaqMan assay revealed that in these plants, the accumulation of the challenge isolate only temporarily slowed down. By contrast, efficient cross-protection was obtained using the mild isolate of the CH2 genotype, and in this case the challenge isolate was barely detectable in the pre-inoculated plants. These results suggest that the interaction between PepMV isolates largely depends on RNA sequence homology and that post-transcriptional gene silencing plays an important role in cross-protection
    "Protected biological control"- Biological pest management in the greenhouse industry
    Pilkington, L.J. ; Messelink, G.J. ; Lenteren, J.C. van; Mottee, K. Le - \ 2010
    Biological Control 52 (2010)3. - ISSN 1049-9644 - p. 216 - 220.
    parasitoid encarsia-formosa - western flower thrips - phytoseiid predators - control agents - intraguild predation - biocontrol - populations - pesticides - cucumber - benefits
    This paper briefly describes the foundations and characteristics of biological control in protected cropping and what drivers are behind adoption of this management system within this industry. Examining a brief history of biological control in greenhouses and what makes it a successful management strategy within the industry, the authors describe the rapid growth of biological control in parts of Europe and what this may mean for the industry in other parts of the world. The reaction of the greenhouse industry to several consumer led campaigns aimed at reducing the incidence of pesticides in the marketplace may be replicated in many other parts of the world. The size and robustness of the biological control industry in greenhouses, which is a reflection of the inherent characteristics of this industry that lends itself to biological control, is strong and growing with indications that this trend will be followed in many areas of the world
    Specific detection of Lysobacter enzymogenes (Christensen and Cook 1978) strain 3.1T8 with TaqMan® PCR
    Nijhuis, E.H. ; Pastoor, R. ; Postma, J. - \ 2010
    Journal of Applied Microbiology 108 (2010)4. - ISSN 1364-5072 - p. 1155 - 1166.
    pseudomonas-fluorescens eps62e - summer patch disease - real-time pcr - biological-control - pythium-aphanidermatum - phylogenetic analysis - kentucky bluegrass - biocontrol strain - fire blight - cucumber
    Aims: To develop a strain-specific TaqMan® PCR method for detecting and quantifying the biocontrol strain Lysobacter enzymogenes 3.1T8. Methods and Results: A primer–probe combination was designed on the basis of a strain-specific sequence selected using REP-PCR (repetitive extragenic palindromic-polymerase chain reaction). The specificity of this combination was demonstrated by 14 other Lysobacter strains that did not react with the selected primer–probe combination. To quantify strain 3.1T8 in cucumber root samples, a calibration curve was prepared by spiking roots with a 10-fold dilution series of the strain. Detection of the biocontrol strain 3.1T8 with this method showed that the strain survived well for 22 days on root tips as well as on older cucumber roots. Survival was higher when the strain was inoculated to younger plants. In a cucumber production system with large volumes of substrate, strain 3.1T8 was detected in high numbers on cucumber roots 3 weeks after inoculation. Conclusions: The primer–probe combination developed was strain specific, because it did not react with other strains of the same species and genus. The TaqMan® PCR method successfully quantified the inoculated biocontrol strain on cucumber roots grown in different cropping systems. Significance and Impact of the Study: The developed TaqMan® PCR method is a strain-specific real-time detection method that can be used to assess the population dynamics of L. enzymogenes strain 3.1T8 for further optimization of its biocontrol efficacy
    The status of biological control of plant diseases in soilless cultivation
    Postma, J. - \ 2009
    In: Recent Developments in Management of Plant Diseases Dordrecht : Springer Netherlands (Plant Pathology in the 21st Century 1) - ISBN 9781402088032 - p. 133 - 146.
    pythium-aphanidermatum - fusarium-oxysporum - growing systems - greenhouse horticulture - indigenous microflora - microbial-populations - crown rot - tomato - cucumber - root
    Avoidance of plant diseases has been a major driver for the development of soilless cultivation systems. Nevertheless, diseases still occur in these systems and the need for additional control measures exist. Traditionally, control has relied on the use of chemical fungicides but environmental pressure to reduce chemical usage in the environment, and fewer active ingredients registered for use, has stimulated the development of biological methods of disease control. One approach has been to utilise microbial inoculants as straight replacements for chemical pesticides and some commercial products are now available. Sufficient root colonization and activity are key issues for effective biocontrol. Another approach has been to create growing systems with improved suppressiveness towards plant diseases. The challenge is to combine the available strategies into environmentally and economically sound soilless plant production systems with low risks for pathogen outbreaks. Soilless systems have the potential of creating a balance between a pathogen-free start and a suppressive microflora. Keywords Biological control - Disease-suppressive substrate - Hydroponics - Recirculated nutrient solution - Microbial populations - Rhizosphere - Root pathogens
    Genetic differences in fruit-set patterns are determined by differences in fruit sink strength and a source : sink threshold for fruit set
    Wubs, A.M. ; Ma, Y.T. ; Heuvelink, E. ; Marcelis, L.F.M. - \ 2009
    Annals of Botany 104 (2009)5. - ISSN 0305-7364 - p. 957 - 964.
    pepper capsicum-annuum - flower abscission - cultivars - cucumber - growth - competition - position - tomato - susceptibility - temperature
    Background and Aims: Fruit set in indeterminate plant species largely depends on the balance between source and sink strength. Plants of these species show fluctuations in fruit set during the growing season. It was tested whether differences in fruit sink strength among the cultivars explained the differences in fruit-set patterns. Methods: Capsicum was chosen as a model plant. Six cultivars with differences in fruit set, fruit size and plant growth were evaluated in a greenhouse experiment. Fruit-set patterns, generative and vegetative sink strength, source strength and the source : sink ratio at fruit set were determined. Sink strength was quantified as potential growth rate. Fruit set was related to total fruit sink strength and the source : sink ratio. The effect of differences observed in above-mentioned parameters on fruit-set patterns was examined using a simple simulation model. Key Results: Sink strengths of individual fruits differed greatly among cultivars. Week-to-week fruit set in large-fruited cultivars fluctuated due to large fluctuations in total fruit sink strength, but in small-fruited cultivars, total fruit sink strength and fruit set were relatively constant. Large variations in week-to-week fruit set were correlated with a low fruit-set percentage. The source : sink threshold for fruit set was higher in large-fruited cultivars. Simulations showed that within the range of parameter values found in the experiment, fruit sink strength and source : sink threshold for fruit set had the largest impact on fruit set: an increase in these parameters decreased the average percentage fruit set and increased variation in weekly fruit set. Both were needed to explain the fruit-set patterns observed. The differences observed in the other parameters (e.g. source strength) had a lower effect on fruit set. Conclusions: Both individual fruit sink strength and the source : sink threshold for fruit set were needed to explain the differences observed between fruit-set patterns of the six cultivars
    Biological variation in the colour development of Golden Delicious apples in the orchard
    Tijskens, L.M.M. ; Unuk, T. ; Stanislav Tojnko, S. ; Hribar, J. ; Simcic, M. - \ 2009
    Journal of the Science of Food and Agriculture 89 (2009)12. - ISSN 0022-5142 - p. 2045 - 2051.
    granny smith apples - crop load - keeping quality - fruit - variance - impact - trees - maturity - cucumber - braeburn
    BACKGROUND: In managing apple orchards, crop load and rate of nitrogen (N) fertilisation are two factors with a significant influence on fruit quantity and quality, because they affect all physiological processes in the tree. Both factors are strongly related to external and internal fruit quality, especially to skin colour, sugar and acid contents and mineral composition, and consequently to the keeping quality of fruits. The aim of this study was to assess the effects of both factors (three crop load levels and two N fertilisation levels) on the colour development of Golden Delicious apples during the last month on the tree in two consecutive seasons. Data on skin colour (L*, a*, b* values) were analysed using nonlinear mixed effects modelling to extract information on the variation in biological shift factor for colour and to link this variation to the different strategies used concerning N fertilisation and crop load. RESULTS: The major source of information is contained in the a* value. The behaviour of the a* value could be described by a logistic or an exponential model depending on the season and the experimental set-up. Nonlinear mixed effects analysis estimating the biological shift factor (maturity) for each individual fruit (random effect) while estimating the rate constant of the decolouration process in common (fixed effect) resulted in explained parts well over 95%. CONCLUSION: The variation in maturity stage between individual fruits is large. Season has the most profound effect on the estimated values, far more important than that of crop load or fertilisation level. The magnitude of variation in colour due to crop load and N fertilisation is not too large. Its effect on the maturity stage of fruits is more profound: the higher the crop load, the higher the variation. The effect of fertilisation seems to be opposite: the higher the fertilisation level, the lower the variation.
    Fruit Set and Yield Patterns in Six Capsicum Cultivars
    Wubs, A.M. ; Ma, Y.T. ; Hemerik, L. ; Heuvelink, E. - \ 2009
    HortScience 44 (2009)5. - ISSN 0018-5345 - p. 1296 - 1301.
    flower abscission - sink strength - cucumber - abortion - pepper - size - growth
    Fruit set and yield patterns were studied in detail in six pepper cultivars. Fruit set differed largely between the cultivars: cultivars with small fruits (fruit fresh weight 20 to 40 g) showed higher fruit set (50%) than cultivars with large fruits (fruit fresh weight 120 to 200 g; 11% to 19%). The former showed continuous fruit set (four to five fruits/plant/week), whereas the latter showed fluctuations in fruit set. Fluctuations in weekly fruit set, expressed as the ratio between standard deviation of weekly fruit set and the mean of weekly fruit set (CV), were much lower for the cultivars with small fruits (0.44 to 0.49) than for the cultivars with large fruits (1.1 to 1.6). Fluctuations in weekly fruit yield varied between 0.51 and 0.77 for cultivars with small fruits and between 1.04 and 1.45 for cultivars with large fruits. Fluctuations in fruit yield were significantly positively correlated (Pearson R = 0.87) with fluctuations in fruit set. The correlation between fruit set and fruit yield patterns was highest with a lag time of 8 weeks for the cultivars with small fruits and 9 to 10 weeks for the cultivars with large fruits. This corresponds with the expected lag time based on the average fruit growth duration. The cultivars produced the same amount of biomass, implying that source strength was more or less similar. Hence, differences in fruit set and fruit yield patterns between the cultivars were not the result of differences in source strength and must therefore be related to differences in sink strength
    Managing quality heterogeneity in the mango supply chain: evidence from Costa Rica
    Zuniga Arias, G. ; Ruben, R. ; Boekel, T. van - \ 2009
    Trends in Food Science and Technology 20 (2009)3-4. - ISSN 0924-2244 - p. 168 - 179.
    coffee chain - growth - metaanalysis - cucumber - storage - food
    Quality is a key aspect for evaluating the performance of commodity chains. Quality performance depends on both subjective consumer perceptions as well as intrinsic attributes of the product. Supply chain procedures and management activities influence the quality level and may reduce or increase the heterogeneity in product quality. In additional to technological measures, timely access to information on market and management options can be helpful to reduce human-related variability. In this article we present an explorative framework for disentangling the interactions between different managerial activities that have an effect on quality variability in mangoes. We use data dispersion statistics to understand the impact of technological and socio-economic factors on heterogeneity in quality performance at different stages of the supply chain. Based on a field survey amongst 51 different agents involved in the mango chain from Costa Rica, information regarding production technologies, agroecological conditions, management intensity, quality control, contracting practices and marketing operations is collected. We also tested randomly 10 mangoes from each agent to analyze the variability in quality attributes, focusing on the ratio between Brix and pH. We find that quality heterogeneity is influenced both by technological variability and by socio-economic diversity. In the mango supply chain from Costa Rica, management differences amongst agents vary depending on the upstream and downstream relationships. Agents related to international traders tend to maintain lowest variability in their management practices in order to be able to respond better to consumer demands. Effective linkages with downstream agents are thus critical to guarantee appropriate incentives for managing quality in upstream segments
    Transient Occurrence of Seed Germination Processes during Coffee Post-harvest Treatment
    Bytof, G. ; Knopp, S.E. ; Kramer, D. ; Breitenstein, B. ; Bergervoet, J.H.W. ; Groot, S.P.C. ; Selmar, D. - \ 2007
    Annals of Botany 100 (2007)1. - ISSN 0305-7364 - p. 61 - 66.
    beta-tubulin accumulation - tomato seeds - gene - expression - cucumber - quality - beans
    Background and Aims: The chemical composition of green coffee and thus the final coffee quality are specifically determined by the mode of post-harvest treatment, i.e. the wet and dry processing. Recently, it was shown that metabolic processes, i.e. germination and, a slightly delayed stress-related metabolism are executed during the course of processing. The specific ambient conditions of either post-harvest treatment may influence differentially the extent and time course of these metabolic reactions; therefore, the incidence and intensity of germination processes in coffee seeds were analysed during processing. Methods: Expression of the germination-specific isocitrate lyase was monitored using competitive RT-PCRs analyses. Resumption of cell cycle activity and cell division were determined by flow cytometry, as well as by the abundance of ß-tubulin quantified by Western blot analyses. Key Results: The extent and the time courses of germination processes in coffee seeds differed significantly between wet and dry processed beans. The highest germination activity occurred 2 d after the onset of wet processing, whereas the corresponding maximum in the course of dry processing appeared about 1 week after the start of post harvest treatment. Conclusions: As recently shown, there are specific differences in the chemical composition of differentially processed coffee beans. It is concluded that these substantial differences are the consequence of the differential expression of germination processes, i.e. they are the result of differences in the corresponding metabolic activities. The coherence of germination-related metabolism and of expression-specific coffee qualities establishes the basis for a novel approach in coffee research. Key words: Coffea arabica, coffee processing
    Modelling the acceptance period of truss tomato batches
    Schouten, R.E. ; Huijben, T.P.M. ; Tijskens, L.M.M. ; Kooten, O. van - \ 2007
    Postharvest Biology and Technology 45 (2007)3. - ISSN 0925-5214 - p. 307 - 316.
    keeping quality - cucumber - fruit
    Tomato batches are characterised by large variation in the quality attributes colour and firmness. Acceptability of tomato batches is consequently affected by the colour maturity and firmness maturity. In this paper, a model for the acceptance period (AP) is presented that describes the acceptability of tomato batches as the time that all quality attributes are considered acceptable as a function of the maturity at harvest. This model takes into account that tomatoes can first be unacceptable due to being over-ripe, then be acceptable, and then be unacceptable again, due to being over-ripe. Furthermore, the AP model takes also into account that consumers may not consume all tomatoes in a truss at the same time, some immediately and some in 3¿4 days time. This is accomplished by combining the acceptance period for future and immediate consumption and taking the intersection of those two as the overall AP to indicate whether tomato batches are suited for both types of consumption. The AP model combines the effects of biological variation, varying consumer limits and the variation in the time of consumption into a practical method to assess acceptability of tomato batches at harvest. The AP model was based on three experiments. In the first and second experiment several tomato batches, differing in harvest maturity, were harvested and stored at three different temperatures. Colour and firmness was measured non-destructively and repeatedly over time so as to estimate the colour and firmness maturity at harvest for each batch. The third experiment was used to determine the consumer limits for today's consumption and consumption over the weekend. By combining the results from all experiments it was possible to estimate the AP as a function of the maturity at harvest, storage temperature and storage duration. The AP model might be used as a tool for growers to assess the acceptability of tomato batches periodically to analyse and solve quality issues or by optimising the compliance to consumer acceptance by varying the storage temperature and transport time to the retailers. Both applications may help to increase profitability in terms of repeated purchase by consumers.
    Role of sink-source relationships in chrysanthemum flower size and total biomass production
    Carvalho, S.M.P. ; Heuvelink, E. ; Harbinson, J. ; Kooten, O. van - \ 2006
    Physiologia Plantarum 128 (2006)2. - ISSN 0031-9317 - p. 263 - 273.
    photosynthesis - tomato - light - growth - fruit - plant - accumulation - morifolium - inhibition - cucumber
    The present work was aimed at understanding and quantifying the effect of sink-source relationships on flower size, using chrysanthemum as a model system. Sink/source ratio was manipulated by flower bud removal (leaving one, two or four flowers, and a control), axillary shoot removal, and varying daily light integral. Furthermore, the influence of flower position within the stem on the flower size was investigated. All means applied to reduce sink/source ratio resulted in a significantly higher individual flower dry mass and area in plants with a fixed number of flowers. Nevertheless, control plants responded to supplementary assimilation light with an increased number of flowers rather than producing larger flowers. Flower position had a negligible effect on flower size in both disbudded and control plants, except that the second-order lateral flowers were significantly smaller than the first-order ones. Singly flowered plants without side shoots represented the greatest potential flower size; they had flowers up to 2.4 times heavier than the control plants. Total aerial plant dry mass was only reduced at very low sink strength treatments, whereas flower mass ratio showed a saturating response to the number of flowers per plant. The results indicate that individual flower size is very sensitive to total plant sink strength, but it does not change with plant source strength when the number of flowers is not manipulated
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