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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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    Correction to: Plant presence reduces root and shoot litter decomposition rates of crops and wild relatives
    Barel, Janna M. ; Kuyper, Thomas W. ; Boer, Wietse de; Deyn, Gerlinde B. De - \ 2020
    Plant and Soil (2020). - ISSN 0032-079X

    The authors wish to report an error in the original version of the paper. In figure 4, panels a) and b) are incorrectly titled respectively "Crop shoots" and "Crop roots". The correct titles should be a) "Wild shoots", and b) "Wild roots" as presented on the next page. No other aspects of the results presented in the publication were affected. The caption of the figure stays unchanged. (Figure presented.).

    Leven de bodem: over samenwerking, zorgzaamheid en een dubbelleven
    Winkler, Karin - \ 2019
    entomologie - oorworm

    over samenwerking, zorgzaamheid en een dubbelleven

    Plant presence reduces root and shoot litter decomposition rates of crops and wild relatives
    Barel, J.M. - \ 2019
    plant functional traits - litter decomposition - litter quality - rhizosphere priming - domestication
    We tested coordination of above-and belowground litter traits and decomposition rates for six pairs of crops and closely related wild plants and studied the influence of plant presence on decomposition.
    Plant presence reduces root and shoot litter decomposition rates of crops and wild relatives
    Barel, Janna M. ; Kuyper, Thomas W. ; Boer, Wietse de; Deyn, Gerlinde B. De - \ 2019
    Plant and Soil 438 (2019)1-2. - ISSN 0032-079X - p. 313 - 327.
    Above- and belowground trait coordination - Domestication - Litter quality - Microbial r- and K strategy - Plant functional traits - Rhizosphere priming

    Aims: Roots contribute greatly to carbon cycling in agriculture. Measuring aboveground litter decomposition could approximate belowground turn-over if drivers of decomposition, f.e. litter traits and plant presence, influence shoot and root decomposition in a comparable manner. We tested coordination of above- and belowground litter traits and decomposition rates for six pairs of crops and closely related wild plants and studied the influence of plant presence on decomposition. Methods: Above- and belowground traits were measured, compared and related to decomposition rates. Shoot and root litters were incubated in presence of the same plant species as the litter species (own) or in presence of two other plant species (a grass or forb). Results: Shoots decomposed 1.43–1.98 times faster than (resp.) wild plant and crop roots. Decomposition correlated negatively with litter carbon and lignin concentrations, except crop root decomposition which correlated negatively with nitrogen concentration. Unexpectedly, plant presence reduced litter decomposition, with strongest effects for root litters in presence of forbs. Conclusions: Carbon cycling might be slower than predicted solely based on shoots decomposition rates, especially in presence of growing plants. While root decomposition of wild plants can be approximated by shoot decomposition, crop shoots are a poor proxy for crop root decomposition.

    Winter cover crop legacy effects on litter decomposition act through litter quality and microbial community changes
    Barel, Janna M. ; Kuyper, Thomas W. ; Paul, Jos ; Boer, Wietse de; Cornelissen, Johannes H.C. ; Deyn, Gerlinde B. de - \ 2019
    Journal of Applied Ecology 56 (2019)1. - ISSN 0021-8901 - p. 132 - 143.
    1.In agriculture, winter cover crop (WCC) residues are incorporated into the soil to improve soil quality, as gradual litter decomposition can improve fertility. Decomposition rate is determined by litter quality, local soil abiotic and biotic properties. How these factors are interlinked and influenced by cropping history is, however, unclear. 2.We grew WCC monocultures and mixtures in rotation with main crops Avena sativa (oat) and Cichorium endivia (endive) and tested how crop rotation influences WCC litter quality, abiotic and biotic soil conditions, and litter decomposition rates. To disentangle WCC litter quality effects from WCC soil legacy effects on decomposition, we tested how rotation history influences decomposition of standard substrates and explored the underlying mechanisms. 3.In a common environment (e.g. winter fallow plots), WCC decomposition rate constants (k) correlated negatively with litter C, lignin and, surprisingly, N content, due to strong positive correlations among these traits. Plots with a history of fast‐decomposing WCCs exhibited faster decomposition of their own litters as well as of the standard substrates filter paper and rooibos tea, as compared to winter fallow plots. 4.WCC treatments differentially affected soil microbial biomass, as well as soil organic matter and mineral nitrogen content. WCC‐induced soil changes affected decomposition rates. Depending on the main crop rotation treatment, legacy effects were attributed to biomass input of WCCs and their litter quality or changes in microbial biomass. 5.Synthesis and applications. These results demonstrate that decomposition in cropping systems is influenced directly through crop residues, as well as through crop‐induced changes in soil biotic properties. Rotation history influences decomposition, wherein productive winter cover crops with low lignin content decompose fast and stimulate the turnover of both own and newly added residues via their knock‐on effect on the soil microbial community. Thus, winter cover crops have promise for sustainable carbon‐ and nutrient‐cycling management through litter feedbacks.
    A plant’s inheritance : Soil legacy effects of crops and wild relatives in relation to plant functional traits
    Barel, Janna Marlinde - \ 2018
    Wageningen University. Promotor(en): G.B. de Deyn; T.W. Kuyper, co-promotor(en): W. de Boer. - Wageningen : Wageningen University - ISBN 9789463434713 - 182

    During their lives plants build-up a legacy for subsequent plants to inherit. The soil that supports plant growth is simultaneously conditioned by the growing plant and carries-over lasting imprints of the previous plant to influence growth of next plants. The microbial soil community and litter decomposition are two essential aspects of plant-soil legacies, as decomposition, mineralisation and microbial community composition and functioning have profound effects on subsequent plant growth by providing nutrients or by causing diseases. Characteristics of a plant may be predictive of its inheritance. Functional plant traits reflect a plant’s growth strategy and response to selection forces in the environment. During crop domestication plant characteristics have been artificially selected for, with potential unwanted side-effects as some characteristics might have been altered unintentionally. Since productivity in agriculture relies on the interactions between plant and soil, it is a necessity to study the relationship between plant traits, decomposition, microbial community composition and the possible effects on future plant growth.

    This thesis presents results from several experiments studying how plants influence the soil, through decomposition of plant residues, the soil microbial community assemblage, and its possible consequence for subsequent plant growth. In a crop rotation experiment plant-soil feedback effects have been studied at field scale, with legacy effects of winter cover crops as the primary focus. Influences of plant traits on litter decomposition and microbial community were studied both in a field context and under controlled greenhouse conditions. By comparing the legacy effects of crops with close-relatives from natural grasslands the effects of domestication on litter decomposition and rhizosphere microbial community composition were explored.

    In the field experiment, it was observed that mixtures of cover crops can perform better than the sum of their parts when the plants in the mixture complemented each other during their growth. Productivity and quality of cover crops was found to promote growth of subsequent main crops, in part through stimulation of soil fungal biomass and feedback effects of decomposing litter. In the greenhouse, growing plants were observed to suppress decomposition of root and shoot litter to varying extent depending on which plant was present and on the quality of the decomposing litter. The results also indicate that domestication has affected plant functional traits in a variety of ways, rather than having predictable effects across a range of crops. Plant functional traits are a useful approach to study legacy effects, as they predict decomposability of plant residues and partially explain the microbial community composition in the rhizosphere. Significance of plant traits as predictors varied with environmental conditions, thus interpretation of the results should be related to its context. This thesis contributes to the understanding of plant-soil interactions, with emphasis on differences and similarities of agricultural and natural ecosystems.

    Data from: Winter cover crop legacy effects on litter decomposition act through litter quality and microbial community changes
    Barel, J.M. ; Kuijper, T.W.M. ; Paul, Jos ; Boer, W. de; Cornelissen, Johannes H.C. ; Deyn, G.B. de - \ 2018
    Wageningen University & Research
    decomposition - microbial community composition - crop rotation - winter cover crop - legacy effects - standardised substrates - nitrogen cycling - carbon cycling - Avena sativa - Cichorium endivia - Lolium perenne - Trifolium repens - Raphanus sativus - Vicia sativa
    1. In agriculture, winter cover crop (WCC) residues are incorporated into the soil to improve soil quality, as gradual litter decomposition can improve fertility. Decomposition rate is determined by litter quality, local soil abiotic and biotic properties. However, how these factors are interlinked and influenced by cropping history is unclear. 2. We grew WCC monocultures and mixtures in rotation with main crops Avena sativa and Cichorium endivia and tested how crop rotation influences WCC litter quality, abiotic and biotic soil conditions, and litter decomposition rates. To disentangle WCC litter quality effects from WCC soil legacy effects on decomposition, we tested how rotation history influences decomposition of standard substrates and explored the underlying mechanisms. 3. In a common environment (e.g. winter fallow plots), WCC decomposition rate constants (k) correlated negatively with litter C, lignin and, surprisingly, N content, due to strong positive correlations among these traits. Plots with a history of fast-decomposing WCCs exhibited faster decomposition of their own litters as well as of the standard substrates filter paper and rooibos tea, as compared to winter fallow plots. 4. WCC treatments differentially affected soil microbial biomass, as well as soil organic matter and mineral nitrogen content. WCC-induced soil changes affected decomposition rates. Depending on the main crop rotation treatment, legacy effects were attributed to biomass input of WCCs and their litter quality or changes in microbial biomass. 5. Synthesis and applications: These results demonstrate that decomposition in cropping systems is influenced directly through crop residues, as well as through crop-induced changes in soil biotic properties. Rotation history influences decomposition, wherein productive winter cover crops with low lignin content decompose fast and stimulate the turn-over of both own and newly added residues via their knock-on effect on the soil microbial community. Thus, winter cover crops have promise for sustainable carbon- and nutrient-cycling management through litter feedbacks.
    Spatial heterogeneity in root litter and soil legacies differentially affect legume root traits
    Saar, Sirgi ; Semchenko, Marina ; Barel, Janna M. ; Deyn, Gerlinde B. de - \ 2018
    Plant and Soil 428 (2018)1-2. - ISSN 0032-079X - p. 253 - 264.
    Functional traits - Local and systemic response - Plant-soil feedback - Root litter - Soil heterogeneity - Spatial root distribution
    Background and Aims: Plants affect the soil environment via litter inputs and changes in biotic communities, which feed back to subsequent plant growth. Here we investigated the individual contributions of litter and biotic communities to soil feedback effects, and plant ability to respond to spatial heterogeneity in soil legacy. Methods: We tested for localised and systemic responses of Trifolium repens to soil biotic and root litter legacy of seven grassland species by exposing half of a root system to control soil and the other half to specific inoculum or root litter. Results: Soil inoculation triggered a localised reduction in root length while litter locally increased root biomass independent of inoculum or litter species identity. Nodule formation was locally suppressed in response to soil conditioned by another legume (Vicia cracca) and showed a trend towards systemic reduction in response to conspecific soil. V. cracca litter also caused a systemic response with thinner roots produced in the part of the root system not directly exposed to the litter. Conclusions: Spatial heterogeneity in root litter distribution and soil communities generate distinct local and systemic responses in root morphology and nodulation. These responses can influence plant-mutualist interactions and nutrient cycling, and should be included in plant co-existence models.
    Legacy effects of diversity in space and time driven by winter cover crop biomass and nitrogen concentration
    Barel, J.M. ; Kuijper, T.W.M. ; Boer, W. de; Douma, Bob ; Deyn, G.B. de - \ 2018
    Journal of Applied Ecology 55 (2018)1. - ISSN 0021-8901 - p. 299 - 310.
    1. Plant diversity can increase nitrogen cycling and decrease soil-borne pests, which are feedback mechanisms influencing subsequent plant growth. The relative strength of these mechanisms is unclear, as is the influence of preceding plant quantity and quality. Here, we studied how plant diversity in space and time influences subsequent crop growth.
    2. During 2 years, we rotated two main crops (Avena sativa, Cichorium endivia) with four winter cover crop (WCC) species in monocultures and mixtures. We hypothesized that, relative to monocultures, WCC mixtures promote WCC biomass (quantity) and nitrogen concentration (quality), soil mineral nitrogen, soil organic matter, and reduce plant-feeding nematode abundance. Additionally, we predicted that preceding crops modified WCC legacies. By structural equation modelling (SEM), we tested the relative importance of WCC shoot biomass and nitrogen concentration on succeeding crop productivity directly and indirectly via nitrogen cycling and root-feeding nematode abundance.
    3. WCC shoot biomass, soil properties and succeeding Avena productivity were affected by first-season cropping, whereas subsequent Cichorium only responded to the WCC treatments. WCC mixtures’ productivity and nitrogen concentration showed over- and under-yielding, depending on mixture composition. Soil nitrogen and nematode abundance did not display WCC mixture effects. Soil organic matter was lower than expected after Raphanus sativus + Vicia sativa mixture. Subsequent Avena productivity depended upon mixture composition, whereas final Cichorium productivity was unresponsive to WCC mixtures. SEM indicated that WCC legacy effects on subsequent Avena (R2 = 0.52) and Cichorium (R2 = 0.59) productivity were driven by WCC biomass and nitrogen concentration, although not by the quantified soil properties.
    4. Synthesis and applications. Through understanding plant–soil feedback, legacy effects of plant species and species mixtures can be employed for sustainable management of agro-ecosystems. Biomass and nitrogen concentration of plants returned to the soil stimulate subsequent plant productivity. Winter cover crop quantity and quality are both manipulable with mixtures. The specificity of spatial and temporal diversity effects warrants consideration of plant species choice in mixtures and rotations for optimal employment of beneficial legacy effects.
    Data from: Legacy effects of diversity in space and time driven by winter cover crop biomass and nitrogen concentration
    Barel, J.M. ; Kuijper, T.W.M. ; Boer, W. de; Douma, J.C. ; Deyn, G.B. de - \ 2017
    crop rotation - soil oranic matter - soil mineral nitrogen - plant-feeding nematodes - plant-soil feedback - plant productivity - agroecology - winter cover crops - agriculture - plant diversity - Avena sativa - Cichorium endivia - Lolium perenne - Trifolium repens - Raphanus sativus - Vicia sativa
    Plant diversity can increase nitrogen cycling and decrease soil-borne pests, which are feedback mechanisms influencing subsequent plant growth. The relative strength of these mechanisms is unclear, as is the influence of preceding plant quantity and quality. Here, we studied how plant diversity in space and time influences subsequent crop growth. During 2 years, we rotated two main crops (Avena sativa, Cichorium endivia) with four winter cover crop (WCC) species in monocultures and mixtures. We hypothesized that, relative to monocultures, WCC mixtures promote WCC biomass (quantity) and nitrogen concentration (quality), soil mineral nitrogen, soil organic matter, and reduce plant-feeding nematode abundance. Additionally, we predicted that preceding crops modified WCC legacies. By structural equation modelling (SEM), we tested the relative importance of WCC shoot biomass and nitrogen concentration on succeeding crop productivity directly and indirectly via nitrogen cycling and root-feeding nematode abundance. WCC shoot biomass, soil properties and succeeding Avena productivity were affected by first-season cropping, whereas subsequent Cichorium only responded to the WCC treatments. WCC mixtures’ productivity and nitrogen concentration showed over- and under-yielding, depending on mixture composition. Soil nitrogen and nematode abundance did not display WCC mixture effects. Soil organic matter was lower than expected after Raphanus sativus + Vicia sativa mixture. Subsequent Avena productivity depended upon mixture composition, whereas final Cichorium productivity was unresponsive to WCC mixtures. SEM indicated that WCC legacy effects on subsequent Avena (R2 = 0.52) and Cichorium (R2 = 0.59) productivity were driven by WCC biomass and nitrogen concentration, although not by the quantified soil properties. Synthesis and applications. Through understanding plant–soil feedback, legacy effects of plant species and species mixtures can be employed for sustainable management of agro-ecosystems. Biomass and nitrogen concentration of plants returned to the soil stimulate subsequent plant productivity. Winter cover crop quantity and quality are both manipulable with mixtures. The specificity of spatial and temporal diversity effects warrants consideration of plant species choice in mixtures and rotations for optimal employment of beneficial legacy effects.
    Data from: Remote sensing of plant trait responses to field-based plant–soil feedback using UAV-based optical sensors
    Meij, Bob Van Der; Kooistra, L. ; Suomalainen, J.M. ; Barel, J.M. ; Deyn, G.B. de - \ 2017
    Wageningen University & Research
    plant-soil feedback - soil legacy - treatment discrimination - high-resolution hyperspectral imagery - UAV remote sensing - plant height - biomass - nitrogen - leaf chlorophyll
    The experimental set-up, treatments, data collection and data analyses are thoroughly described in the Biogeoscience manuscript ‘Remote sensing of plant trait responses to field-based plant-soil feedback using UAV-based optical sensors’ doi:10.5194/bg-2016-452. Therefore we refer to the manuscript for detailed information an here we provide a brief summary to enable readers to follow what the data entail. The data were collected from a 2-year field experiment with plant rotations in a full factorial design. The plant treatments we focused on are legacy effects of the plant treatments (listed below) to the following oat crop. In this oat crop we quantified several plant traits both in situ and via remote sensing by use of UAV and hyperspectral and EGB sensors. The experiment was set-up in five randomized field blocks. We used part of the in situ collected data to parameterize the hyperspectral data based models and we validated these models with the other half of the field plots. Plant treatments Fa= fallow Lp= Lolium perenne Rs= Raphanus sativus Tr= Trifolium repens Vs= Vicia sativa Lp+Tr= 50:50 species mixture (relative to the monoculture seed densities) of the species Lp and Tr Rs+Vs= 50:50 species mixture (relative to the monoculture seed densities) of the species Rs and Vs
    Remote sensing of plant trait responses to field-based plant-soil feedback using UAV-based optical sensors
    Meij, Bob van der; Kooistra, Lammert ; Suomalainen, Juha ; Barel, Janna M. ; Deyn, Gerlinde B. de - \ 2017
    Biogeosciences 14 (2017)3. - ISSN 1726-4170 - p. 733 - 749.

    Plant responses to biotic and abiotic legacies left in soil by preceding plants is known as plant-soil feedback (PSF). PSF is an important mechanism to explain plant community dynamics and plant performance in natural and agricultural systems. However, most PSF studies are short-term and small-scale due to practical constraints for field-scale quantification of PSF effects, yet field experiments are warranted to assess actual PSF effects under less controlled conditions. Here we used unmanned aerial vehicle (UAV)-based optical sensors to test whether PSF effects on plant traits can be quantified remotely. We established a randomized agro-ecological field experiment in which six different cover crop species and species combinations from three different plant families (Poaceae, Fabaceae, Brassicaceae) were grown. The feedback effects on plant traits were tested in oat (Avena sativa) by quantifying the cover crop legacy effects on key plant traits: height, fresh biomass, nitrogen content, and leaf chlorophyll content. Prior to destructive sampling, hyperspectral data were acquired and used for calibration and independent validation of regression models to retrieve plant traits from optical data. Subsequently, for each trait the model with highest precision and accuracy was selected. We used the hyperspectral analyses to predict the directly measured plant height (RMSE=5.12cm, R2=0.79), chlorophyll content (RMSE=0.11gm-2, R2=0.80), N-content (RMSE=1.94gm-2, R2=0.68), and fresh biomass (RMSE=0.72kgm-2, R2=0.56). Overall the PSF effects of the different cover crop treatments based on the remote sensing data matched the results based on in situ measurements. The average oat canopy was tallest and its leaf chlorophyll content highest in response to legacy of Vicia sativa monocultures (100cm, 0.95gm-2, respectively) and in mixture with Raphanus sativus (100cm, 1.09gm-2, respectively), while the lowest values (76cm, 0.41gm-2, respectively) were found in response to legacy of Lolium perenne monoculture, and intermediate responses to the legacy of the other treatments. We show that PSF effects in the field occur and alter several important plant traits that can be sensed remotely and quantified in a non-destructive way using UAV-based optical sensors; these can be repeated over the growing season to increase temporal resolution. Remote sensing thereby offers great potential for studying PSF effects at field scale and relevant spatial-temporal resolutions which will facilitate the elucidation of the underlying mechanisms.

    Legume presence reduces the decomposition rate of non-legume roots
    Saar, S. ; Semchenko, M. ; Barel, J.M. ; Deyn, G.B. De - \ 2016
    Soil Biology and Biochemistry 94 (2016). - ISSN 0038-0717 - p. 88 - 93.
    Litter decomposition - Litter quality - Nutrient effects - Plant litter interaction - Rhizosphere priming effect - Root decomposition

    Living plants can enhance litter decomposition rates via a priming effect by releasing root exudates which provide energy to saprotrophic microbes and thereby enable them to degrade litter faster. The strength of this effect, however, is expected to be dependent on the litter properties. To test whether the presence of a growing plant affects the decomposition rate of dead roots with different traits, we used dead roots of seven species (3 grasses, 3 legumes, 1 forb) as litter and quantified litter mass loss after eight weeks of incubation in soil with or without a growing white clover (Trifolium repens) plant. We expected root decomposition to be faster in the presence of T. repens, especially for roots with high C:N ratio. We found that the presence of T. repens slowed down the decomposition of grass and forb roots (negative priming), while it did not significantly affect the decomposition of legume roots. Our results show that root decomposition can be slowed down in the presence of a living plant and that this effect depends on the properties of the decomposing roots, with a pronounced reduction in root litter poor in N and P, but not in the relatively nutrient-rich legume root litters. Negative priming effect of legume plants on non-legume litter decomposition may have resulted from preferential substrate utilisation by soil microbes

    Pyrrolizidine and tropane alkaloids in teas and the herbal teas peppermint, rooibos and chamomile in the Israeli market
    Shimshoni, Jakob Avi ; Duebecke, Arne ; Mulder, Patrick P.J. ; Cuneah, Olga ; Barel, Shimon - \ 2015
    Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 32 (2015)12. - ISSN 1944-0049 - p. 2058 - 2067.
    herbal tea - LC-MS/MS - pyrrolizidine alkaloids - tea - tropane alkaloids

    Dehydro pyrrolizidine alkaloids (dehydro PAs) are carcinogenic phytotoxins prevalent in the Boraginaceae, Asteraceae and Fabaceae families. Dehydro PAs enter the food and feed chain by co-harvesting of crops intended for human and animal consumption as well as by carry-over into animal-based products such as milk, eggs and honey. Recently the occurrence of dehydro PAs in teas and herbal teas has gained increasing attention from the EU, due to the high levels of dehydro PAs found in commercially available teas and herbal teas in Germany and Switzerland. Furthermore, several tropane alkaloids (TAs, e.g. scopolamine and hyoscyamine) intoxications due to the consumption of contaminated herbal teas were reported in the literature. The aim of the present study was to determine the dehydro PAs and TAs levels in 70 pre-packed teabags of herbal and non-herbal tea types sold in supermarkets in Israel. Chamomile, peppermint and rooibos teas contained high dehydro PAs levels in almost all samples analysed. Lower amounts were detected in black and green teas, while no dehydro PAs were found in fennel and melissa herbal teas. Total dehydro PAs concentrations in chamomile, peppermint and rooibos teas ranged from 20 to 1729 μg/kg. Except for black tea containing only mono-ester retrorsine-type dehydro PAs, all other teas and herbal teas showed mixed patterns of dehydro PA ester types, indicating a contamination by various weed species during harvesting and/or production. The TA levels per teabag were below the recommended acute reference dose; however, the positive findings of TAs in all peppermint tea samples warrant a more extensive survey. The partially high levels of dehydro PAs found in teas and herbal teas present an urgent warning letter to the regulatory authorities to perform routine quality control analysis and implement maximum residual levels for dehydro PAs.

    Heliotropium europaeum Poisoning in Cattle and Analysis of its Pyrrolizidine Alkaloid Profile
    Shimshoni, J.A. ; Mulder, P.P.J. ; Bouznach, A. ; Edery, N. ; Pasval, I. ; Barel, S. ; Khaliq, M.A.E. ; Perl, S. - \ 2015
    Journal of Agricultural and Food Chemistry 63 (2015)5. - ISSN 0021-8561 - p. 1664 - 1672.
    metabolic-activation - senecio-jacobaea - toxicosis - livestock - enzymes - calves - milk
    Pyrrolizidine alkaloids (PAs) are carcinogenic and genotoxic phytochemicals found exclusively in angiosperms. The ingestion of PA-containing plants often results in acute and chronic toxicities in man and livestock, targeting mainly the liver. During February 2014, a herd of 15-18-month-old mixed-breed beef cattle (n = 73) from the Galilee region in Israel was accidently fed hay contaminated with 12% Heliotropium europaeum (average total PA intake was 33 mg PA/kg body weight/d). After 42 d of feed ingestion, sudden death occurred over a time period of 63 d with a mortality rate of 33%. Necropsy and histopathological examination revealed fibrotic livers and moderate ascites, as well as various degrees of hyperplasia and fibrosis of bile duct epithelial cells. Elevated ¿-glutamyl-transferase and alkaline phosphatase levels were indicative of severe liver damage. Comprehensive PA profile determination of the contaminated hay and of native H. europaeum by LC-MS/MS revealed the presence of 30 PAs and PA-N-oxides, including several newly reported PAs and PA-N-oxides of the rinderine and heliosupine class. Heliotrine- and lasiocarpine-type PAs constituted 80% and 18% of the total PAs, respectively, with the N-oxides being the most abundant form (92%). The PA profile of the contaminated hay showed very strong resemblance to that of H. europaeum
    Characterization of Dickeya strains isolated from potato grown under hot-climate conditions
    Tsror, L. ; Ben-Daniel, B. ; Chalupowicz, L. ; Wolf, J.M. van der; Lebiush, S. ; Erlich, O. ; Dror, O. ; Barel, V. ; Nijhuis, E.H. ; Manulis-Sasson, S. - \ 2013
    Plant Pathology 62 (2013)5. - ISSN 0032-0862 - p. 1097 - 1105.
    soft-rot erwinias - chrysanthemi - population - israel - crops - pcr
    Dickeya strains isolated in Israel in 2006–2010 were characterized by dnaX sequence analysis, pulsed-field gel electrophoresis (PFGE), biochemical assays and pectolytic activity, and found to be homogeneous: most of them could be classified as ‘Dickeya solani’. Of the 34 strains isolated from imported seed tubers or potato plants grown from imported seed, 32 were typed as ‘D. solani’ and only two were characterized as Dickeya dianthicola. Biovar typing indicated that all ‘D. solani’ strains were biovar 3. ‘Dickeya solani’ strains were most closely related to Dickeya dadantii subsp. dieffenbachiae according to PFGE and dnaX analyses and both species exhibited high pectolytic activity. Expression levels of two putative virulence genes, pelL (encoding a pectic enzyme) and dspE (encoding a type III effector) were significantly induced in ‘D. solani’ strains isolated from potato plants or tubers grown in hot climates such as the Negev region in Israel, compared to those isolated from seed tubers imported from the Netherlands, France or Germany. Results of this study support the hypothesis that ‘D. solani’ strains isolated in Israel are also clonal; however, they appear to be more virulent than strains isolated in Europe
    Biting force in cichlids : A discussion of the planar model of barel (1983)
    leeuwen, J.L. Van; Spoor, C.W. - \ 1986
    Netherlands Journal of Zoology 37 (1986)3-4. - ISSN 0028-2960 - p. 307 - 314.

    Some consequences of a definition of the 'static biting force' in cichlid fishes by BAREL (1983) are explored. A free-body diagram of the lower jaw shows that apart from the forces of the food and the jaw adductor muscle on the jaw other forces are needed to obtain static equilibrium. The introduction of joint forces solves this problem. Our analysis also shows that in many biting activities a locomotor force is required. Starting from an alternative definition for the static biting force, quite different results may be obtained for the space requirements of the jaw adductor muscle and the lower jaw as compared to those of BAREL.

    Vegetatie analyse met de computerprogramma's DECORANA en TWINSPAN
    Barel, R.A. - \ 1986
    Wageningen : ICW (Nota / Instituut voor Cultuurtechniek en Waterhuishouding no. 1701) - 28
    toepassingen - computer software - methodologie - plantenecologie - technieken - vegetatie - applications - computer software - methodology - plant ecology - techniques - vegetation
    TESTOP : een FORTRAN programma voor controle en bewerking van vegetatie - opnamen
    Barel, R.A. - \ 1986
    Wageningen : ICW (Nota / Instituut voor Cultuurtechniek en Waterhuishouding no. 1700) - 21
    toepassingen - computer software - methodologie - plantenecologie - technieken - vegetatie - applications - computer software - methodology - plant ecology - techniques - vegetation
    Studies on the sterile male technique as a means of control of Adoxophyes orana (Lepidoptera, Tortricidae) 5. Release trials
    Ankersmit, G.W. ; Barel, C.J.A. ; Mobach, J.D. ; Schouten-Parren, J. ; Wassenberg-de Vries, G. - \ 1977
    Netherlands Journal of Plant Pathology 83 (1977). - ISSN 0028-2944 - p. 73 - 83.
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