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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Improved Pastures Support Early Indicators of Soil Restoration in Low-input Agroecosystems of Nicaragua
Webster, Emily ; Gaudin, Amélie C.M. ; Pulleman, Mirjam ; Siles, Pablo ; Fonte, Steven J. - \ 2019
Environmental Management 64 (2019)2. - ISSN 0364-152X - p. 201 - 212.
Brachiaria brizantha - Earthworms - Pasture degradation - Permanganate oxidizable carbon - Silvopastoral systems - Soil health

Pasture degradation hinders livestock production and ecosystem services that support rural smallholder communities throughout Latin America. Silvopastoral systems, with improved pasture cultivars (especially Brachiaria spp.) and multipurpose trees, offer a promising strategy to restore soils and improve livelihoods in the region. However, studies evaluating the impact of such systems on pasture productivity and soil health under realistic smallholder constraints are lacking. We evaluated the impact of improved pasture grass and tree establishment on a suite of soil health indicators in actively grazed, low-input, farmer-managed silvopastoral systems. In August 2013, paired pasture treatments (improved grass with trees vs. traditional pastures) were established on nine farms with similar land-use histories near Matagalpa, Nicaragua. On each farm, one treatment was left as traditional pasture with naturalized grass (Hyparrhenia rufa), while the adjacent treatment was sown with the improved grass (Brachiaria brizantha cv. Marandu) and planted with tree saplings without fertilizer. In August 2015, we measured standing biomass and a suite of chemical, biological, and physical soil health variables. Improved silvopastoral systems with B. brizantha produced more standing grass biomass and supported higher levels of earthworm populations and permanganate oxidizable carbon (POXC) compared to the traditional control. Correlations suggest that earthworms and POXC were associated with incipient improvements to soil aggregate stability and water holding capacity. We report measurable improvements to soil health just two years following the establishment of improved pasture systems under common smallholder management practices and suggest that these systems, even with minimal fertility inputs, have the potential to enhance regional sustainability.

Burgess, T.M. & Webster, R. 1980. Optimal interpolation and isarithmic mapping of soil properties. I. The semi-variogram and punctual kriging. Journal of Soil Science, 31, 315–331. : Commentary on the impact of Burgess & Webster (1980a) by R.M. Lark, G.B.M. Heuvelink and T.F.A. Bishop
Lark, R.M. ; Heuvelink, G.B.M. ; Bishop, T.F.A. - \ 2019
European Journal of Soil Science 70 (2019)1. - ISSN 1351-0754 - p. 7 - 10.
Erratum to: The sponge microbiome project
Moitinho-Silva, Lucas ; Nielsen, Shaun ; Amir, Amnon ; Gonzalez, Antonio ; Ackermann, Gail L. ; Cerrano, Carlo ; Astudillo-Garcia, Carmen ; Easson, Cole ; Sipkema, Detmer ; Liu, Fang ; Steinert, Georg ; Kotoulas, Giorgos ; McCormack, Grace P. ; Feng, Guofang ; Bell, James J. ; Vicente, Jan ; Björk, Johannes R. ; Montoya, Jose M. ; Olson, Julie B. ; Reveillaud, Julie ; Steindler, Laura ; Pineda, Mari Carmen ; Marra, Maria V. ; Ilan, Micha ; Taylor, Michael W. ; Polymenakou, Paraskevi ; Erwin, Patrick M. ; Schupp, Peter J. ; Simister, Rachel L. ; Knight, Rob ; Thacker, Robert W. ; Costa, Rodrigo ; Hill, Russell T. ; Lopez-Legentil, Susanna ; Dailianis, Thanos ; Ravasi, Timothy ; Hentschel, Ute ; Li, Zhiyong ; Webster, Nicole S. ; Thomas, Torsten - \ 2018
GigaScience 7 (2018)12. - ISSN 2047-217X
The sponge microbiome project
Moitinho-Silva, Lucas ; Nielsen, Shaun ; Amir, Amnon ; Gonzalez, Antonio ; Ackermann, Gail L. ; Cerrano, Carlo ; Astudillo-Garcia, Carmen ; Easson, Cole ; Sipkema, Detmer ; Liu, Fang ; Steinert, Georg ; Kotoulas, Giorgos ; McCormack, Grace P. ; Feng, Guofang ; Bell, James J. ; Vicente, Jan ; Björk, Johannes R. ; Montoya, Jose M. ; Olson, Julie B. ; Reveillaud, Julie ; Steindler, Laura ; Pineda, Mari Carmen ; Marra, Maria V. ; Ilan, Micha ; Taylor, Michael W. ; Polymenakou, Paraskevi ; Erwin, Patrick M. ; Schupp, Peter J. ; Simister, Rachel L. ; Knight, Rob ; Thacker, Robert W. ; Costa, Rodrigo ; Hill, Russell T. ; Lopez-Legentil, Susanna ; Dailianis, Thanos ; Ravasi, Timothy ; Hentschel, Ute ; Li, Zhiyong ; Webster, Nicole S. ; Thomas, Torsten - \ 2017
GigaScience 6 (2017)10. - ISSN 2047-217X
16S rRNA gene - Archaea - Bacteria - Marine sponges - Microbial diversity - Microbiome - Symbiosis
Marine sponges (phylum Porifera) are a diverse, phylogenetically deep-branching clade known for forming intimate partnerships with complex communities of microorganisms. To date, 16S rRNA gene sequencing studies have largely utilised different extraction and amplification methodologies to target the microbial communities of a limited number of sponge species, severely limiting comparative analyses of sponge microbial diversity and structure. Here, we provide an extensive and standardised dataset that will facilitate sponge microbiome comparisons across large spatial, temporal, and environmental scales. Samples from marine sponges (n = 3569 specimens), seawater (n = 370), marine sediments (n = 65) and other environments (n = 29) were collected from different locations across the globe. This dataset incorporates at least 268 different sponge species, including several yet unidentified taxa. The V4 region of the 16S rRNA gene was amplified and sequenced from extracted DNA using standardised procedures. Raw sequences (total of 1.1 billion sequences) were processed and clustered with (i) a standard protocol using QIIME closed-reference picking resulting in 39 543 operational taxonomic units (OTU) at 97% sequence identity, (ii) a de novo clustering using Mothur resulting in 518 246 OTUs, and (iii) a new high-resolution Deblur protocol resulting in 83 908 unique bacterial sequences. Abundance tables, representative sequences, taxonomic classifications, and metadata are provided. This dataset represents a comprehensive resource of sponge-associated microbial communities based on 16S rRNA gene sequences that can be used to address overarching hypotheses regarding host-associated prokaryotes, including host specificity, convergent evolution, environmental drivers of microbiome structure, and the sponge-associated rare biosphere.
Genetic selection for dairy cow welfare and resilience to climate change
Pryce, J. ; Haas, Y. de - \ 2017
In: Achieving sustainable production of milk / Webster, John, Burleigh Dodds Science Publishing Limited - ISBN 9781786760524
Rates of genetic gain in dairy cows are impressive, especially for milk production traits that drive profitability (VanRaden 2004). However, narrow breeding goals focused on milk production traits are detrimental to reproductive performance and health of cows (Rauw et al. 1998), and consequently there has been pressure to develop breeding values to enable selection that balances both production and non-production traits. Although, the rationale to extend breeding goals initially focused entirely on the impact of the new breeding value to farmer profitability, breeding goals are now becoming more complex in order to meet challenges set by consumers and society (Boichard and Brochard 2012; Martin-Collado et al. 2015). For example, the growing human population places more pressure on the available limited resources; global changes may mean hotter drier conditions to manage livestock and there is also increased consumer awareness about animal welfare and farming conditions. To accommodate this requirement, over recent decades there has been a rapid expansion of the number of breeding values that are available for farmers to select on. Almost without exception these breeding values rely on large amounts of field data that are freely available through current recording systems, such as milk production, calving records, insemination dates, pregnancy test outcomes, health records and culling dates.
Predicting the HMA-LMA status in marine sponges by machine learning
Moitinho-Silva, Lucas ; Steinert, Georg ; Nielsen, Shaun ; Hardoim, Cristiane C.P. ; Wu, Yu Chen ; McCormack, Grace P. ; López-Legentil, Susanna ; Marchant, Roman ; Webster, Nicole ; Thomas, Torsten ; Hentschel, Ute - \ 2017
Frontiers in Microbiology 8 (2017). - ISSN 1664-302X - 14 p.
16S rRNA gene - Marine sponges - Microbial diversity - Microbiome - Random forest - Symbiosis

The dichotomy between high microbial abundance (HMA) and low microbial abundance (LMA) sponges has been observed in sponge-microbe symbiosis, although the extent of this pattern remains poorly unknown. We characterized the differences between the microbiomes of HMA (n = 19) and LMA (n = 17) sponges (575 specimens) present in the Sponge Microbiome Project. HMA sponges were associated with richer and more diverse microbiomes than LMA sponges, as indicated by the comparison of alpha diversity metrics. Microbial community structures differed between HMA and LMA sponges considering Operational Taxonomic Units (OTU) abundances and across microbial taxonomic levels, from phylum to species. The largest proportion of microbiome variation was explained by the host identity. Several phyla, classes, and OTUs were found differentially abundant in either group, which were considered "HMA indicators" and "LMA indicators." Machine learning algorithms (classifiers) were trained to predict the HMA-LMA status of sponges. Among nine different classifiers, higher performances were achieved by Random Forest trained with phylum and class abundances. Random Forest with optimized parameters predicted the HMA-LMA status of additional 135 sponge species (1,232 specimens) without a priori knowledge. These sponges were grouped in four clusters, from which the largest two were composed of species consistently predicted as HMA (n = 44) and LMA (n = 74). In summary, our analyses shown distinct features of the microbial communities associated with HMA and LMA sponges. The prediction of the HMA-LMA status based on the microbiome profiles of sponges demonstrates the application of machine learning to explore patterns of host-associated microbial communities.

Engineers at the Patient’s Bedside: : The Case of Silence in Inter-institutional Educational Innovation
Verouden, Nick ; Sanden, M.C.A. van der; Aarts, M.N.C. - \ 2016
In: The Silences of Science / Mellor, Felicity, Webster, Stephen, London : Routledge - ISBN 9781472459978 - p. 89 - 112.
Innovation in science and technology is increasingly linked with interdisciplinarity. Encouraging this trend depends in part on cutting-edge educational programmes that revise, reinvent and redesign curricula as interdisciplinary vehicles, establishing and re-establishing relations between traditional fields and areas of expertise (Stone et al., 1999; Casey, 1994). Such programmes are valuable because they can overcome ‘silo’ mentalities and equip prospective students with the skills and knowledge necessary for understanding and solving complex societal problems (Stone et al.,1999; McFadden et al., 2010). Although these programmes are very promising, their development and

implementation also brings challenges. The literature on curriculum development shows that many programmes have struggled to achieve true integration (McFadden et al., 2010; Stone et al., 1999). Dam-Mieras et al. (2008), in their study of an international master’s programme in sustainable development and management developed collaboratively by nine universities, observed that universities have their own experts and own programmes and that the ‘not invented here’ argument influences how details about new programme are discussed. Focussing on innovative online instruction courses, Xu and Morris (2007) found that the absence of group cohesiveness between faculty and project coordinators can hinder the collaborative course development process and affect the quality of the end product. Stone et al. (1999) emphasize that faculty members and administrators work at cross-purposes and view each other’s initiatives with suspicion. Given the importance that scientists, academic institutions and policy makers ascribe to innovation, along with their assumption that such innovation is a sure result of interdisciplinarity, it is essential to gain a better understanding of how curriculum development in academic education actually works. For this chapter, we consider how processes of connecting and inter-

relating could add to our understanding of the problems and dilemmas that arise in developing and implementing such programmes. Scholars of innovation, in science and technology and beyond, have explained that innovation is not some abstract algorithm: it relies on interaction and collaboration between

multiple actors with different expertises, visions, priorities and investment (Van Bommel et al., 2011; Leeuwis and Aarts, 2011; Akrich et al., 2002; Fonseca, 2002). This process of interacting is very difficult, however, and creates many tensions. This is revealed by studies that show the lurking problems of connecting previously unconnected people around new ideas and technologies. These studies show how innovation processes become defined by competition for scarce resources, protracted negotiations over priorities and interests, and dynamics of inclusion and exclusion (Leeuwis andAarts, 2011; Pretty, 1995; Van Bommel et al., 2011). Fonseca (2002) hence explains that innovation always creates a paradoxical situation, in which organizations, in their search to accelerate change and adapt to and find solutions for external challenges and demands, unavoidably create new and unpredictable interactional patterns. Given that interacting is a complicated matter in innovation processes, a

key question within the management of innovation literature is how we can account for the way relevant actors connect, or fail to connect (Akrich et al., 2002). In this respect, verbal communication is often cited as an essential mechanism for effectively connecting important actors and social groups around innovative ideas, products, or technologies (Van Bommel et al., 2011). In turn, the markers of effective verbal communication as a frame for innovation are seen to be openness, dialogue, and the ability to cooperate and be reflective on one’s thoughts and actions (Stilgoe et al., 2013). Thorp and Goldstein (2010), writing about university innovation, describe conversations as the fertile ground from which innovation grows and urge us to make time and space for those conversations. Dialogue and openness are seen as indicators of the quality of interaction, and process transparency as a decisive component of academic innovation. By being open or transparent in discussing issues and problems, actors build confidence that negotiation is ‘real’ and not a cover-up for private backroom deals (de Bruijn and ten Heuvelhof, 2008). Although there is a wealth of research on communication for innovation,

most scholarly work focuses on what is exchanged verbally, on how actors collate all the relevant evidence, put it on the table and discuss it openly. As of yet, silence is absent from these studies of communication for innovation. Building on recent organizational and strategy scholarship, in which silence is approached as an intricate concept with powerful functions and meanings in social interaction (Van Assche and Costaglioli, 2012; Carter et al., 2008; Henriksen and Dayton, 2006; Panteli and Fineman, 2005; Tucker and Edmondson, 2003; Jaworski, 2005; Morrison and Milliken, 2000), we suggest that silence merits much more attention in analyses of academic innovation. This chapter therefore explores the role of moments of silence during interactions within networks developing and implementing educational innovation. The structure of this chapter is as follows. We start by looking at the litera-

ture on dynamic innovation networks and communication and complement these insights with scholarship on silence within organization studies. After briefly introducing our approach, we present the findings of a study of an inter-institutional and interdisciplinary joint bachelor’s programme that was

implemented at the interface of health and technology. The purpose of the study was to better understand the significance of moments of silence in developing and implementing this programme. We end with the implications of our findings for steering in the context of interdisciplinary innovation.
High C3 photosynthetic capacity and high intrinsic water use efficiency underlies the high productivity of the bioenergy grass Arundo donax
Webster, R.J. ; Driever, S.M. ; Kromdijk, Johannes ; McGrath, Justin ; Leakey, A.D.B. ; Siebke, Katharina ; Demetriades-Shah, Tanvir ; Bonnage, Steve ; Peloe, Tony ; Lawson, Tracy ; Long, S.P. - \ 2016
Scientific Reports 6 (2016). - ISSN 2045-2322

Arundo donax has attracted interest as a potential bioenergy crop due to a high apparent productivity. It uses C3 photosynthesis yet appears competitive with C4 grass biomass feedstock's and grows in warm conditions where C4 species might be expected to be that productive. Despite this there has been no systematic study of leaf photosynthetic properties. This study determines photosynthetic and photorespiratory parameters for leaves in a natural stand of A. donax growing in southern Portugal. We hypothesise that A. donax has a high photosynthetic potential in high and low light, stomatal limitation to be small and intrinsic water use efficiency unusually low. High photosynthetic rates in A. donax resulted from a high capacity for both maximum Rubisco (Vc,max 117 μ1/4mol CO2 m-2 s-1) and ribulose-1:5-bisphosphate limited carboxylation rate (Jmax 213 μ1/4mol CO2 m-2 s-1) under light-saturated conditions. Maximum quantum yield for light-limited CO2 assimilation was also high relative to other C3 species. Photorespiratory losses were similar to other C3 species under the conditions of measurement (25%), while stomatal limitation was high (0.25) resulting in a high intrinsic water use efficiency. Overall the photosynthetic capacity of A. donax is high compared to other C3 species, and comparable to C4 bioenergy grasses.

Development and preliminary evaluation of a 90 K Axiom® SNP array for the allo-octoploid cultivated strawberry Fragaria × ananassa
Bassil, N.V. ; Davis, T.M. ; Zhang, Hailong ; Ficklin, Stephen ; Mittmann, Mike ; Webster, Teresa ; Mahoney, Lise ; Wood, David ; Alperin, E.S. ; Rosyara, U.R. ; Koehorst-vanc Putten, Herma ; Monfort, Amparo ; Sargent, D.J. ; Amaya, Iraida ; Denoyes, Beatrice ; Bianco, Luca ; Dijk, Thijs van; Pirani, Ali ; Iezzoni, Amy ; Main, Dorrie ; Peace, Cameron ; Yang, Yilong ; Whitaker, Vance ; Verma, Sujeet ; Bellon, Laurent ; Brew, Fiona ; Herrera, Raul ; Weg, Eric van de - \ 2015
BMC Genomics 16 (2015)1. - ISSN 1471-2164
Fragaria - Genotyping array - Plant breeding - Polyploidy - Reduced ploidy - Single nucleotide polymorphism - Strawberry

A high-throughput genotyping platform is needed to enable marker-assisted breeding in the allo-octoploid cultivated strawberry Fragaria × ananassa. Short-read sequences from one diploid and 19 octoploid accessions were aligned to the diploid Fragaria vesca 'Hawaii 4' reference genome to identify single nucleotide polymorphisms (SNPs) and indels for incorporation into a 90 K Affymetrix® Axiom® array. We report the development and preliminary evaluation of this array. Results: About 36 million sequence variants were identified in a 19 member, octoploid germplasm panel. Strategies and filtering pipelines were developed to identify and incorporate markers of several types: di-allelic SNPs (66.6%), multi-allelic SNPs (1.8%), indels (10.1%), and ploidy-reducing "haploSNPs" (11.7%). The remaining SNPs included those discovered in the diploid progenitor F. iinumae (3.9%), and speculative "codon-based" SNPs (5.9%). In genotyping 306 octoploid accessions, SNPs were assigned to six classes with Affymetrix's "SNPolisher" R package. The highest quality classes, PolyHigh Resolution (PHR), No Minor Homozygote (NMH), and Off-Target Variant (OTV) comprised 25%, 38%, and 1% of array markers, respectively. These markers were suitable for genetic studies as demonstrated in the full-sib family 'Holiday' × 'Korona' with the generation of a genetic linkage map consisting of 6,594 PHR SNPs evenly distributed across 28 chromosomes with an average density of approximately one marker per 0.5 cM, thus exceeding our goal of one marker per cM. Conclusions: The Affymetrix IStraw90 Axiom array is the first high-throughput genotyping platform for cultivated strawberry and is commercially available to the worldwide scientific community. The array's high success rate is likely driven by the presence of naturally occurring variation in ploidy level within the nominally octoploid genome, and by effectiveness of the employed array design and ploidy-reducing strategies. This array enables genetic analyses including generation of high-density linkage maps, identification of quantitative trait loci for economically important traits, and genome-wide association studies, thus providing a basis for marker-assisted breeding in this high value crop.

Development of the WagRhSNP AXIOM SNP Array Based on Sequences from Tetraploid Cut Roses and Garden Roses
Smulders, M.J.M. ; Voorrips, R.E. ; Esselink, G. ; Santos Leonardo, T.M. ; Westende, W.P.C. van 't; Vukosavljev, M. ; Koning-Boucoiran, C.F.S. ; Weg, W.E. van de; Arens, P.F.P. ; Schulz, D. ; Debener, T. ; Bellon, L. ; Mittmann, M. ; Pirani, A. ; Webster, T. ; Brew, F. ; Cox, P. ; Maliepaard, C.A. - \ 2015
In: Proceedings VIth International Symposiul on Rose Research and Cultivation. - ISHS - ISBN 9789462610552 - p. 177 - 184.
Rose, as many other important ornamental, vegetable and field crops, is polyploid. This poses constraints in genetic analyses due to the occurrence of multiple alleles at marker and trait loci and the existence of multiple allele dosages. Developments in marker discovery (next generation sequencing), detection (SNP arrays) and analysis (software for dosage scoring) now make it feasible to develop high-density molecular marker maps for the homologous chromosomes in tetraploids separately, and thus perform QTL analysis in tetraploids. We developed a SNP array for rose to develop genetic maps in tetraploid garden roses and cut roses, which are to be used for inheritance studies and genetic mapping. Here we have indicated the general strategy followed for developing a SNP array and for scoring and using the SNP data generated, and elaborated on the activities undertaken to use the WagRhSNP Axiom array in rose. The array design is not proprietary but can be used by all researchers working in rose
Fungal Planet description sheets: 107-127
Crous, P.W. ; Summerell, B.A. ; Shivas, R.G. ; Burgess, T.I. ; Decock, C.A. ; Dreyer, L.L. ; Granke, L.L. ; Guest, D.I. ; Hardy, G.E.St.J. ; Hausbeck, M.K. ; Hüberli, D. ; Jung, T. ; Koukol, O. ; Lennox, C.L. ; Liew, E.C.Y. ; Lombard, L. ; McTaggart, A.R. ; Pryke, J.S. ; Roets, F. ; Saude, C. ; Shuttleworth, L.A. ; Stukely, M.J.C. ; Vánky, K. ; Webster, B.J. ; Windstam, S.T. ; Groenewald, J.Z. - \ 2012
Persoonia 28 (2012). - ISSN 0031-5850 - p. 138 - 182.
sp-nov - allied genera - south-africa - diaporthales - eucalyptus - genus - cryphonectriaceae - gnomoniaceae - reevaluation - evolutionary
Novel species of microfungi described in the present study include the following from Australia: Phytophthora amnicola from still water, Gnomoniopsis smithogilvyi from Castanea sp., Pseudoplagiostoma corymbiae from Corymbia sp., Diaporthe eucalyptorum from Eucalyptus sp., Sporisorium andrewmitchellii from Enneapogon aff. lindleyanus, Myrmecridium banksiae from Banksia, and Pilidiella wangiensis from Eucalyptus sp. Several species are also described from South Africa, namely: Gondwanamyces wingfieldii from Protea caffra, Montagnula aloes from Aloe sp., Diaporthe canthii from Canthium inerne, Phyllosticta ericarum from Erica gracilis, Coleophoma proteae from Protea caffra, Toxicocladosporium strelitziae from Strelitzia reginae, and Devriesia agapanthi from Agapanthus africanus. Other species include Phytophthora asparagi from Asparagus officinalis (USA), and Diaporthe passiflorae from Passiflora edulis (South America). Furthermore, novel genera of coelomycetes include Chrysocrypta corymbiae from Corymbia sp. (Australia), Trinosporium guianense, isolated as a contaminant (French Guiana), and Xenosonderhenia syzygii, from Syzygium cordatum (South Africa). Pseudopenidiella piceae from Picea abies (Czech Republic), and Phaeocercospora colophospermi from Colophospermum mopane (South Africa) represent novel genera of hyphomycetes. Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.
Effects of human handling during early rearing on the behaviour of dairy calves
Schütz, K.E. ; Hawke, M.L. ; Waas, J.R. ; McLeay, L.M. ; Bokkers, E.A.M. ; Reenen, C.G. van; Webster, J.R. ; Stewart, M. - \ 2012
Animal Welfare 21 (2012)1. - ISSN 0962-7286 - p. 19 - 26.
human-animal interactions - play-behavior - veal calves - cattle - welfare - cows - reactivity - responses - contact - heifers
We examined the effects of daily positive or negative human handling on the behaviour of Holstein-Friesian dairy calves (n = 20 calves per treatment, five calves per group). The response to humans and indicators of positive emotions were examined at four weeks of age. Calves that received positive handling approached a familiar handler within 1 min in 50% of the handling sessions compared to 17% of the sessions for negatively handled calves but showed no difference when approaching an unfamiliar person. Calves that received positive handling showed less avoidance behaviour in their home pen to an approaching unfamiliar person (score, positive: 3.7, negative: 2.8) but there was no treatment effect on flight distance when tested outside the home pen. Both treatment groups responded similarly to a novel object and performed the same amount of play behaviour. Calves that received positive handling interacted more with cow brushes than calves that received negative handling (positive: 9.9%, negative: 7.9% of the total time). At three months of age, avoidance behaviour was re-tested, this time including 20 control animals of the same breed and age, reared routinely on-farm. Controls showed more avoidance behaviour (positive: 1.5, negative: 1.0, control: 0.3) and had a greater flight distance (positive: 3.3 m, negative: 3.7 m, control: 4.9 m). The results confirm existing literature demonstrating that the quantity and quality of handling influence the response towards humans. Little evidence was found that the type of early handling influences behaviours indicative of positive emotions.
Epidemiology and effective control of Altenaria altenata, causal agent of dead (dormant) flower bud disease of pear
Wenneker, M. ; Joosten, N.N. ; Anbergen, R.H.N. ; Vink, P. ; Bruggen, A.S. van - \ 2011
In: ISHS Acta Horticulturae 909. - ISHS - ISBN 9789066055049 - p. 485 - 490.
Dead flower buds are a common phenomenon in pear culture in The Netherlands, Belgium and Mediterranean countries. Disease cases are also reported from South America. The disease is characterized by a partial or complete necrosis of flower buds during tree dormancy. The disease progresses during winter and spring, eventually resulting in the death of most flowers and decay of buds at flowering. In The Netherlands the problem is mostly found in the main pear cultivar ‘Conference’, but cultivars such as ‘Doyenne du Comice’ and ‘Gieser Wildeman’ are also affected. Disease incidence may be as high as 80-90%. Possible causes mentioned are abiotic stresses, incompatibility between scion and cultivar, and plant pathogens and pests. Research in recent years revealed that pear growth regulation does not prevent the occurrence of dead flower buds. Also, the bacterium Pseudomonas syringae pv. syringae (P.s.s.) was commonly regarded as the causal agent of dead flower buds in pear, although the relation between P.s.s. and dead flower buds in orchards has never been proven in The Netherlands. However, the fungus Alternaria alternata was found in diseased flower buds and also often in symptomless flower buds. A linear relationship between infection rate and dead flower bud disease incidence was found. Pathogenicity tests and Koch’s postulates were carried out. It was concluded that A. alternata is the causal agent of dead (dormant) flower bud disease. A. alternata is known to cause late blight in pistachio and several diseases in fruit crops such as moldy-core in apple and brown rot in citrus. By identifying the causal agent of dead flower bud disease, an effective control strategy could be developed. In field trials it was proven that fungicide treatments can reduce disease incidence significantly.
Crop load regulation in 'Conference' pears
Maas, F.M. ; Steeg, P.A.H. van der - \ 2011
In: XI International Pear Symposium, General Roca(Rio Negro), Argentina, 16 - 19 November, 2010. - ISHS - ISBN 9789066055049 - p. 367 - 379.
Estimativa do Índice de Área Foliar (IAF) e Biomassa em pastagem no estado de Rondônia, Brasil
Zanchi, F.B. ; Waterloo, M.J. ; Randow, C. von; Kruijt, B. ; Cardoso, F.L. ; Manzi, A.O. - \ 2009
Acta Amazonica 39 (2009)2. - ISSN 0044-5967 - p. 335 - 348.
Medidas mensais da altura da pastagem, biomassa total, variações de biomassa viva e morta, a área específica foliar (SLA) e o Índice de Área de Folha (IAF) de fevereiro de 1999 a janeiro de 2005 na Fazenda Nossa Senhora (FNS) e em Rolim de Moura (RDM) entre Fevereiro a Março de 1999, Rondônia, Brasil. A pastagem predominante é Urochloa brizantha (Hochst. ex A. Rich) R. D. Webster (99% na FNS e 76% em RDM), com pequenas manchas de Urochloa humidicula (Rendle). A altura média anual da grama foi de ~0,16 m. Com o pastejo, o mínimo mensal foi de 0,09 m (estação seca) e máximo de 0,3 m sem pastejo (estação úmida). O IAF, biomassa total, material morto, vivo e SLA tiveram valores médios de 2,5 m2 m-2 , 2202 kg ha-1, 2916 kg ha-1 e 19 m2 kg-1 respectivamente. A média mensal da biomassa foi 4224 kg ha-1 em 2002 e 6667 kg ha-1 em 2003. Grande variação sazonal do material vivo e morto, sendo mais alto o vivo durante a estação úmida (3229 contra 2529 kg ha-1), sendo o morto maior durante a seca (2542 contra 1894 kg ha-1). O nível de água no solo variou de -3,1 a -6,5 m durante as estações. Em médias anuais os IAF foram de 1,4 em 2000 a 2,8 em 2003 e o SLA entre 16,3 m2 kg-1 em 1999 e 20,4 m2 kg-1 em 2001. As observações do Albedo variaram de 0,18 para 0,16 em relação aos altos valores de IAF.
Book review: R. Webster, M.A. Oliver: Geostatistics for Environmental Scientists, 2nd ed.
Heuvelink, G.B.M. - \ 2009
Mathematical Geosciences 41 (2009). - ISSN 1874-8961 - p. 487 - 489.
Effects of previous handling on calf responses towards humans
Schütz, K.E. ; Stewart, M. ; Hawke, M.L. ; Bokkers, E.A.M. ; Reenen, C.G. van; Webster, J.R. - \ 2009
- p. 170 - 170.
Human-animal relationships affect the production and welfare of animals. We investigated whether the type of handling of dairy calves influences their response towards humans. Forty, group-housed, Holstein-Friesian calves were exposed to either positive (e.g. soft voices, slow movements, patting) or negative (e.g. rough voices, rapid movements, pushing) handling (n=20 calves/treatment, 5 calves/group), twice daily (7 min/session) from 4 days to 5 weeks of age. Reactions towards humans were investigated around 4 weeks of age in a 'calf escape test' in their home pens, and by measuring the flight distance in a raceway. In the calf escape test, each calf was given a score between 0 and 4 depending on whether the observer could (1) make eye contact, (2) take 1, or (3) 2 steps towards the calf, or (4) touch the calf before it moved away (defined as moving both forelegs). Data were analysed using ANOVA. Calves that received positive handling showed less avoidance behaviour (mean score; positive:3.7, negative:2.8, sd:0.66, p=0.039) but there was no difference between the treatment groups in flight distance (positive:0.6m, negative:0.7m, sed:0.24m, p=0.526). Calves that received positive handling were 3 times more likely to voluntarily approach a human within 1min, compared to negatively handled calves (50% vs 17% of the calves approached the human, sed: 9.8%, p=0.015). When the calves were 3 months old, we repeated the flight distance and calf escape tests and added a control group (n=20) of the same age that had been reared under normal farm management (minimal handling). Controls showed more avoidance behaviour in the calf escape test (mean score; positive:1.5, negative:1.0, control:0.3, sd:0.21, p
Evaluation of pyrus and quince rootstocks for high density pear orchards
Maas, F.M. - \ 2008
In: ISHS X International Pear Symposium, Peniche, Portugal, 31 August,2008. - Leuven : ISHS - ISBN 9789066056114 - p. 599 - 609.
High density planting systems are a prerequisite to economise the use of land and labour costs of orchards. Dwarfing rootstocks controlling the vigour of the scion cultivars form the basis for such orchards (Wertheim and Webster, 2005). In the Netherlands, rootstock research is limited to and focussed on testing rootstocks selected abroad. For the Dutch pear growers the main selection criteria for new rootstocks are: 1) control of tree size; 2) production; 3) fruit size; 4) fruit quality; 5) production efficiency; 6) frost resistance. Additional criteria for Dutch fruit tree nurseries exporting trees to other countries are: 1) compatibility with scion cultivars; 2) suitability for growth in calcareous soils; 3) easy propagation. In all trials rootstock performance is compared to Quince MC, the most commonly used rootstocks for pears in the Netherlands. Recently, a number of Pyrus (Pyrus communis) and Quince (Cydonia oblonga) rootstocks have been tested with ‘Conference’ and ‘Doyenné du Comice’ as the scion cultivars. Generally, the production efficiency of the Pyrus rootstocks was much less than for Quince MC. Another disadvantage of the evaluated Pyrus rootstocks was their high sensitivity towards pear decline. Several rootstocks were rejected after examination of the graft union because of suspected compatibility problems. Of the tested Quince rootstocks C 132 shows promise because of its control of tree growth in combination with good fruit size and Eline® because of its reduction of fruit russeting in ‘Conference’
Course of chlormequat residue in 'Conference'pears over a 9-year period following its final use iin the orchard
Maas, F.M. - \ 2008
In: ISHS X International Pear Symposium, Peniche, Portugal. - Leuvel : ISHS - ISBN 9789066056114 - p. 281 - 288.
Chlormequat (CCC) was used for many years in the Netherlands as a chemical growth retardant to restrict vegetative growth and promote flower bud development in pears. After several years of annual applications, CCC residue levels in the fruits frequently exceeded the maximum residue limit (MRL) of 3.0 mg/kg. In 2001 the use of CCC in pears was banned and the MRL was reduced to 0.05 mg/kg. CCC is a very persistent chemical which seems to have accumulated in trees treated for many years with this growth retardant. Because of the expected carry over of these accumulated residues into fruits in the years following the last application of CCC, it was decided to decrease the MRL. In 2001 and 2002 a temporary MRL of 0.5 mg/kg was applied. From March 2003 until July 2006 the temporary MRL was reduced to 0.3 mg/kg. From August 2006 until July 2009 this was further reduced to 0.2 mg/kg. However, the final MRL will be reduced to 0.05 mg/kg within the shortest time possible. Pears sampled in years in which CCC was applied to the trees contained CCC residues that varied between 6.8 and 1.1 mg/kg, depending on the dosage and number of years of CCC application. During the first growing season without further CCC applications, the CCC residue of the fruits decreased on average by about 90%. During the following year without CCC the rates of decrease in CCC residues varied widely. In some trials a 60% decrease was noted in the second 'CCC free' year, while in other trials no further decrease was observed. In 2003 a further reduction was observed in most trees. Compared to 2002, the CCC levels had decreased by 6 to 80% and were all below the temporary MRL of 0.3 mg/kg. However, despite these decreases in CCC residue levels in trees grown for three to six years without any further CCC application, in 2003 the CCC residue in the fruits of most trees still exceeded the future MRL of 0.05 mg/kg. In 2006 only the fruits of one trial in Zeewolde still exceeded the MRL of 0.05 mg CCC/kg. In these trees which received their final CCC application in 1999, an average CCC level of 0.06 mg/kg was measured. Thus, even after 8 years of cultivation without CCC, pear trees which were amply treated with CCC in the past may produce fruits with a CCC residue level above the MRL of 0.05 mg/kg. Analysis of the wood of the trunks of these trees showed that this part of the trees still contained CCC levels up to 4.3 mg/kg. This CCC may have been partially transported into the fruits produced in 2007.
Strategies to control tree vigour and optimise fruit production in 'Conference' pears
Maas, F.M. - \ 2008
In: ISHS X International Pear Symposium, Peniche, Portugal. - Leuven : ISHS - ISBN 9789066056114 - p. 139 - 146.
The ban on the use of chlormequat (CCC) in pear orchards in 2001 forced Dutch pear growers to look for alternative methods to control tree vigour and stimulate flower bud development and fruit production. Root pruning and trunk notching have become the major growth retarding methods. In addition to the mechanical methods for controlling tree vigour, Regalis (Prohexadione-Calcium) and ethephon were tested as alternative chemical growth regulators for 'Conference' pears. In 2004, a trial was started in which six different strategies to control tree vigour and optimize fruit production in 'Conference' trees are compared. In 4 strategies root pruning was the major treatment, while in 2 strategies trunk incisions were the initial treatment to reduce tree vigour and stimulate fruit production. In 2005, no further root pruning or trunk incisions were made and ethephon and Regalis were the only treatments applied in some of the strategies. Ethephon and Regalis were also applied in 2006 in addition to root pruning in March and June or in June only. All of the strategies evaluated significantly reduced shoot growth and improved fruit production. Regular yields of 52 to more than 70 tons/ha were achieved for 3 consecutive years. So far, ethephon and Regalis have shown no or only minor additional beneficial effects compared to root pruning or trunk incision followed by root pruning in the years thereafter. Flowering, fruit yield and fruit quality of 'Conference' pears produced using the different strategies are presented and discussed.
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