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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    Characterization of Coxiella burnetii outbreak strains
    Kuley, Runa - \ 2017
    Wageningen University. Promotor(en): M.A. Smits; J.M. Wells, co-promotor(en): A. Bossers. - Wageningen : Wageningen University - ISBN 9789463431514 - 226
    coxiella burnetii - q fever - outbreaks - strains - characterization - pathogenesis - zoonoses - virulence - dna sequencing - polymerase chain reaction - livestock farming - netherlands - coxiella burnetii - q-koorts - uitbraken (ziekten) - stammen (biologisch) - karakterisering - pathogenese - zoönosen - virulentie - dna-sequencing - polymerase-kettingreactie - veehouderij - nederland

    Q fever is a worldwide zoonotic infectious disease caused by the bacterium Coxiella burnetii. During 2007-2010, the largest Q fever outbreak was reported in The Netherlands, where more than 4000 human cases were registered showing a serious burden of the disease. During this outbreak, goats harboring predominantly the CbNL01 genotype strain were identified as the major source of disease in humans and drastic measures such as mass culling of infected goats were implemented to reduce the spread of the pathogen and control the disease. In order to minimize such complications in the future, it is crucial to have a thorough understanding of the disease causing pathogen and to develop effective Q fever vaccines. The causes of the large Dutch outbreak are not well-understood and one of the main reasons speculated were the hyper-virulent behavior of the circulating C. burnetii isolates. The research described in this thesis focuses on the characterization of C. burnetii outbreak strains isolated from infected goats, cattle, sheep and human clinical materials. Our studies were initiated to better understand the bacterial pathogenesis, virulence, evolution, adaptations in various environments, host immune responses and to identify pathogen related factors that have modulated the disease outbreak. We specifically aimed to identify the virulence factors and mechanisms that contributed to the increased zoonotic potential of the strain associated with the Dutch Q fever outbreak.

    The studies presented in this thesis majorly applied Pathogenomic approaches at the genome and transcriptome level to decipher host-pathogen interactions and to develop new tools to study C. burnetii infections. A transcriptome analysis of the outbreak C. burnetii strain of the CbNL01 genotype grown under in vivo and in vitro conditions resulted in the identification of distinct metabolic adaptations and virulence mechanisms of the bacterium. Detailed comparative analysis of complete genome sequences of C. burnetii strains showed a high similarity between strains of the same genotype. Genome sequences of the Dutch outbreak CbNL01 genotype strains were more divergent than the genome sequences of the less prevalent CbNL12 genotype strains and the NM reference strain. The analysis also showed that the high virulence of the outbreak strains was not associated with acquiring novel virulence-related genes arguing against the idea that the Dutch outbreak was due to emergence of hyper-virulent strains though horizontal gene transfer. Among the prominent genetic differences in the CbNL01 outbreak strains compared to CbNL12 and NM, were the presence of several point mutations and increased transposon mediated genome plasticity, which might have contributed to its epidemic potential. Point mutations, especially in a large number of membrane proteins, could also have contributed to the increased zoonotic potential of CbNL01 strains allowing this clone to escape the host immune responses in goats and humans. In addition, mutations in critical genes involved in virulence and evasion of the host immune system could be potentially involved in the increased virulence of the CbNL01 outbreak strains. On the contrary, studies on host immune responses in an in vivo (experimental infections in mice) and an in vitro (human PBMC’s stimulation) model did not show any difference associated with the strain genotype. However, differences in immune responses were found to be associated with the host-origin of the C. burnetii strains. Among different host-origin strains, strains derived from goats and humans generated significantly lower innate and adaptive immune responses than strains derived from cattle, whereas no differences in immune responses were observed when strains were grouped based upon their genotype. These observations support immune evasions as a major virulence strategy of goat and human strains in hosts and further suggest that bacteria originating from goats have a greater potential to cause outbreaks in humans. This indicates that for Q fever prevention purposes goats should be efficiently monitored for the presence of C. burnetii. Taken together, the results described in this thesis suggest that the virulence potential of C. burnetii strains is not only based on genetic differences, but also on other host-adaptation mechanisms such as transposition of genomic elements and/or differential regulation of gene expression. Finally, the results from this thesis provide a framework for future studies in the development of vaccines and diagnostic tools for Q fever.

    Are all eggs equal? : embryonic development and nutrient metabolism in chicken eggs of different origins
    Nangsuay, A. - \ 2016
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; R. Meijerhof. - Wageningen : Wageningen University - ISBN 9789462577749 - 213
    eggs - hens - broilers - characteristics - strains - embryonic development - nutrients - metabolism - hatcheries - poultry - nutrition physiology - eieren - hennen - vleeskuikens - karakteristieken - stammen (biologisch) - embryonale ontwikkeling - voedingsstoffen - metabolisme - broedinstallaties - pluimvee - voedingsfysiologie

    Hatching eggs, supplied to hatcheries are originating from different origins varying in breed, strain, and breeder age. These hatching eggs can be different in size, composition and eggshell properties, which might influence nutrient and O2 availability and consequently could affect embryonic development and nutrient metabolism. The aim of this thesis was therefore 1) to investigate effects of egg origin on nutrient and O2 availability, 2) to investigate effects of egg origins on nutrient metabolism and embryonic development and 3) to investigate consequences of different egg origins on the incubation process and hatching characteristics. In five studies, effects of different egg origins on nutrient and O2 availability, nutrient metabolism, embryo development and hatching characteristics were investigated. The first and second study focused on breeder age and egg size. The third study on breed; broilers and layers. The fourth study on broiler strain and the fifth study on breeder age, strain and eggshell temperature (EST). The overall findings in this thesis suggest that hatching eggs from different origins are not equal in availability of nutrients and O2. Nutrient availability is altered through variation in yolk size, especially by the effects of breeder age and breed. O2 availability is altered by differences in eggshell properties, which is influenced by especially breed and broiler strain. The availability of both nutrients and O2 plays a role on nutrient metabolism measured as embryonic heat production (HP) and consequently on embryonic development. Between incubation day (E) E7 and E14, both nutrient and O2 availability might affect nutrient metabolism as shown in the results of the broiler and layer comparison. Between E14 and hatching, the availability of O2 becomes the most determinant factor for nutrient metabolism and consequently for embryonic development. An increase in EST from 37.8 to 38.9°C from E7 onward resulted in an acceleration of nutrient metabolism and embryonic development until E16, but thereafter a high EST resulted in reduced yolk free body mass development. Embryos with an accelerated metabolic speed at an early stage of incubation, caused by an increased EST, might reach limited O2 availability at a higher magnitude than the embryos at a normal EST. As a result, nutrient metabolism is restricted and embryonic development is depressed. It can be concluded that not only the HP, but also the availability of O2 is crucial to be taken into account for developing incubator temperature. The principle is to obtain an optimal EST, which could maintain the balance between O2 requirement (driven by nutrient metabolism) and O2 availability for a continuing optimal nutrient metabolism to generate sufficient energy for embryonic development throughout incubation.

    Phenotypic and genetic diversity of the species Lactobacillus rhamnosus
    Ceapa, C.D. - \ 2016
    Wageningen University. Promotor(en): Michiel Kleerebezem; Jan Knol; J. Lambert. - Wageningen : Wageningen University - ISBN 9789462576285 - 195
    fermentation products - probiotics - intestinal microorganisms - lactic acid bacteria - strains - medicinal properties - genomics - nutrition and health - fermentatieproducten - probiotica - darmmicro-organismen - melkzuurbacteriën - stammen (biologisch) - medicinale eigenschappen - genomica - voeding en gezondheid

    The thesis explores the diversity of Lactobacillus rhamnosus, a species from which strains are studied for their anti-inflammatory, anti-allergic, and diarrhea preventing effects. The work combines observations on the behavior of the bacteria in a simplified laboratory setting (use of carbohydrates, immune modulation effects, anti-pathogenic effects) with genomic information obtained by sequencing, with the aim to pinpoint genes that could be relevant for bacterial survival and metabolic capacities. Phenotypic and genotypic profiling analyses congruently revealed that carbohydrate metabolism and transport is essential for this species’ adaptation to the environment. Genotype–phenotype correlation analysis enabled us to predict and then experimentally verify genes responsible for the utilization of L-Sorbose, L-Fucose α-D-Methyl Glycoside.

    Naar een beter substraatgebruik in de champignonteelt via rassen : een genetische analyse
    Baars, J.J.P. ; Sonnenberg, A.S.M. - \ 2015
    Wageningen : Plant Research International (Rapport / Plant Research International 2015-2) - 20
    eetbare paddestoelen - agaricus bisporus - veredelen - kruisingen - stammen (biologisch) - genetische bronnen - segregatie - materialen uit biologische grondstoffen - substraten - edible fungi - agaricus bisporus - breeding - crosses - strains - genetic resources - segregation - biobased materials - substrates
    In 2014 is een nieuwe stap gezet in het project om tot een efficienter substraatgebruik te komen in de champignonteelt. Deze stap heeft twee doelen: • Het bepalen van de breeding value (hoe gedragen de stammen zich in kruisingen en welke waarde hebben ze dus in de veredeling) • Welke lijnen zijn geschikt om segregerende populaties te maken. Deze populaties zullen gebruikt worden om genomische gebieden/genen te vinden die de verschillen in efficientie in substraat gebruik kunnen verklaren. De kennis kan gebruikt worden voor zowel veredelen op substraatgebruik als het vinden van alternatieve grondstoffen voor het maken van substraat.
    Substraatgebruik van de collectie champignonlijnen van Plant Breeding
    Sonnenberg, A.S.M. ; Baars, J.J.P. - \ 2012
    paddestoelen - agaricus - stammen (biologisch) - stamverschillen - rassenproeven - efficiëntie - genetische bronnen - mushrooms - agaricus - strains - strain differences - variety trials - efficiency - genetic resources
    Poster met onderzoeksinformatie. Om te kijken welke mogelijkheden er liggen om rassen met een verbeterd substraatgebruik te maken is een gedeelte van de collectie van Plant Breeding Wageningen UR doorgelicht.
    'Green 33 zou wel eens een probleem kunnen zijn' : Nieuwe stam onder de loep : Interview met Schepers, Evenhuis en Kessel
    Tiggelen, A. van; Schepers, H.T.A.M. ; Evenhuis, A. ; Kessel, G.J.T. - \ 2012
    Akker magazine 2012 (2012)2. - ISSN 1875-9688 - p. 30 - 33.
    phytophthora infestans - stammen (biologisch) - fungiciden - aardappelen - plantenziekteverwekkende schimmels - veldproeven - akkerbouw - phytophthora infestans - strains - fungicides - potatoes - plant pathogenic fungi - field tests - arable farming
    In 2010 werd Nederland geconfronteerd met een nieuwe phytophthorastam, Green 33. Het gevonden isolaat bleek minder goed bestreden te worden door het veelgebruikte phytophthoramiddel. PPO en PRI doen nu naarstig onderzoek naar het gedrag van deze stam.
    Towards high productivities of microalgae in photobioreactors
    Bosma, R. - \ 2010
    Wageningen University. Promotor(en): Rene Wijffels; Hans Tramper, co-promotor(en): Marian Vermue. - [S.l. : S.n. - ISBN 9789085855590 - 133
    bioreactoren - algen - fotosynthese - licht - lichtregiem - oogsten - screenen - stammen (biologisch) - ultrageluid - onderwijs - lesmaterialen - fotobioreactoren - bioreactors - algae - photosynthesis - light - light regime - harvesting - screening - strains - ultrasound - education - teaching materials - photobioreactors
    The biodiversity of microalgae is enormous and they represent an almost untapped source of unique algae products. Presently, there is a niche market for high-value algal products (e.g. carotenoids and fatty acids). To make commercial production of low-value bulk products possible, still many bottlenecks should be solved. This thesis addresses several of these bottlenecks.
    Based on research on the light conversion by the microalgae, a model was developed that predicts the minimal and maximal productivity of the microalgae in a photobioreactor. In addition, a screening method was developed for fast determination of the growth rate of microalgae. This method can be used to optimize the growth medium as well as to optimize cultivation conditions. We used this method to determine the growth inhibiting effects of free fatty acids on a microalga. In addition, the application of ultrasound as harvesting process for microalgae was investigated. It was found that ultrasound could indeed be used to harvest microalgae, but that this process was commercially only feasible for special applications on small scale. Because algal technology is a relatively new research field, learning materials should be developed for appropriate education in this field. This thesis describes the development of a practical in which third year BSc students learn how to cultivate microalgae and to develop a production strategy to achieve as much ß-carotene production as possible using these algae. Finally, the research described above is evaluated and further research strategies are identified to push microalgal technology ahead and to achieve higher productivity of microalgae in photobioreactors in the future.

    Molecular characterization of beet necrotic yellow vein virus in Greece and transgenic approaches towards enhancing rhizomania disease resistance
    Pavli, O.I. - \ 2010
    Wageningen University. Promotor(en): Just Vlak; G.N. Skaracis, co-promotor(en): M. Prins; N.J. Panopoulos. - [S.l. : S.n. - ISBN 9789085855477 - 166
    beta vulgaris - suikerbieten - bietenrhizomanievirus - stammen (biologisch) - karakteristieken - pathogeniteit - plantenvirussen - ziekteresistentie - resistentie van variëteiten - transgene planten - genexpressie - griekenland - beta vulgaris - sugarbeet - beet necrotic yellow vein virus - strains - characteristics - pathogenicity - plant viruses - disease resistance - varietal resistance - transgenic plants - gene expression - greece
    Rhizomania disease of sugar beet, caused by Beet necrotic yellow vein virus (BNYVV), is responsible for severe economic losses. Due to the widespread occurrence of BNYVV and the absence of other practical and efficient control measures, economic viability of the crop is to the largest extent dependent on the use of varieties genetically resistant to the disease. Recent reports on the emergence of virus strains capable of compromising the Rz1-based resistance as well as on the spread of highly pathogenic RNA 5-containing BNYVV isolates have necessitated a detailed investigation of the situation as it evolves in Greece. The study revealed the widespread occurrence of BNYVV throughout the country as well as the prevalence of pathotype A isolates in all sugar beet growing regions. Sequence determination of the p25 protein, responsible for symptom development, pointed to the amino acid motifs ACHG/VCHG in the hypervariable amino acid region 67-70. However, the presence of valine (V) in position 67 was not associated with increased pathogenicity and resistance breaking properties. Disease severity appeared mostly dependent on agroclimatic conditions influencing the progress of the disease. A survey for a possible occurrence of Beet Soilborne Virus (BSBV) and Beet Virus Q (BVQ) in rhizomania infested fields revealed the co-existence of both viruses, with BVQ being systematically found in co-infections with BNYVV, while BSBV was in all cases only found in triple infections. Towards the exploitation of the antiviral properties of RNA silencing, three intron hairpin constructs carrying parts of the BNYVV replicase gene, were evaluated for their potential to confer rhizomania resistance in Ri T-DNA-transformed sugar beet roots. The results show that transgenic hairy roots were effectively protected against the virus disease and further indicate that the developed methodology for Agrobacterium rhizogenes-mediated transformation can be employed as a suitable platform to study transgene expression in sugar beet and other transformation recalcitrant crop species. In parallel, the potential to exploit the HrpZPsph protein from Pseudomonas syringae pv. phaseolicola for engineering rhizomania resistance in sugar beet against BNYVV was demonstrated by the successful engineering and protection against BNYVV in the model plant Nicotiana benthamiana
    Non-persistente virusoverdracht door bladluizen, Aardappelvirus Y in aardappel
    Verbeek, M. ; Piron, P.G.M. ; Cuperus, C. ; Dullemans, A.M. ; Wiegers, G.L. ; Bruin, A. de; Raaij, H.M.G. van; Vlugt, R.A.A. van der; Bovenkamp, G. van den; Haan, E. de; Miedema, G. ; Stolte, T. - \ 2009
    Wageningen : Plant Research International - 23
    aardappelvirus y - stammen (biologisch) - aphididae - aardappelen - epidemiologie - ziekteoverdracht - akkerbouw - potato virus y - strains - aphididae - potatoes - epidemiology - disease transmission - arable farming
    De laatste jaren nemen de problemen met Aardappelvirus Y (PVY) toe. Dit is terug te vinden in de toenemende percentages declassering van partijen pootaardappelen. Deze tendens is niet te verklaren met behulp van de vangstcijfers van bladluizen, de overbrengers van het virus. De bladluisvangsten nemen de laatste jaren juist af. Om de oorzaak van de toenemende problemen met PVY te achterhalen, startte in 2006 het proejct "Non-persistente overdracht door bladluizen, aardappel", gezamenlijk gefinancierd door het Ministerie van LNV, de NAK en het productschap Akkerbouw (PA). Het onderzoek richtte zich op een drietal vragen: •Is de bladluissituatie in het veld veranderd? Met andere woorden, zijn er nieuwe bladluissoorten aanwezig die PVY kunnen overdragen? •Zijn er andere of nieuwe stammen van het virus in het veld aanwezig? •Is de overdrachtsefficiëntie van bladluizen voor nieuwe PVY-stammen anders? Er is aangetoond dat in de afgelopen jaren de veldsituatie voor wat betreft aanwezige PVY-stammen is veranderd. Enkele jaren geleden werd nog algemeen aangenomen dat voornamelijk PVYN in de Nederlandse aardappelteelt voorkwam. Nu komt deze stam nauwelijks meer voor en zijn PVYO en de recombinante stammen PVYNTN en PVYN-Wi volop aanwezig. Gedurende drie jaar zijn de bladluisvangsten door de NAK uitgebreid geanalyseerd op het eventueel voorkomen van nieuwe soorten. De cijfers zijn vergeleken met de vangstcijfers uit de tachtiger jaren van de vorige eeuw. Nieuwe soorten bladluizen die PVY kunnen overbrengen zijn niet waargenomen. Er is één nieuwe soort gevonden (Utamphorophora humboldti), maar van deze soort is nog niet bekend of het PVY kan overbrengen en, zo ja, met welke efficiëntie. Dit kon helaas niet in dit project worden uitgezocht. Er is een nieuwe methode ontwikkeld om de relatieve transmissie efficiëntie (REF-waarde) van bladluissoorten te meten. Deze methode heeft als voordeel dat hij het gehele jaar door kan worden uitgevoerd. Daarnaast is de methode minder arbeidsintensief in vergelijking met de in de tachtiger jaren gebruikte methode. Van de belangrijkste bladluissoorten is de REF-waarde bepaald voor de overdracht van PVYN, PVYNTN en PVYN-Wi. De waarden van overdracht van PVYN komen goed overeen met de in de tachtiger jaren in Nederland bepaalde REF-waarden, die toen ook met PVYN zijn bepaald. Bij sommige bladluissoorten worden andere REF-waarden gevonden wanneer PVYNTN en PVYN-Wi worden overgedragen. Voor deze soorten zal voorgesteld worden nieuwe REF-waarden in gebruik te nemen voor bepaling van de advies-loofdodingsdatum
    Characterization of the stress response in 17a-hydroxylase deficient common carp (Cyprinus carpio L.)
    Nematollahi, M.A. - \ 2008
    Wageningen University. Promotor(en): Johan Verreth; Johan van Arendonk, co-promotor(en): Hans Komen; Hilde van Pelt-Heerschap. - [S.l.] : S.n. - ISBN 9789085049043 - 135
    karper - cyprinus - stressreactie - genexpressie - deficiëntie - stammen (biologisch) - dna-sequencing - polymerase-kettingreactie - nieren - carp - cyprinus - stress response - gene expression - deficiency - strains - dna sequencing - polymerase chain reaction - kidneys
    In this thesis we describe interrenal hyperplasia in a teleost fish, the common carp, Cyprinus carpio L, caused by 17α-hydroxylase deficiency. Two homozygous, XX male inbred strains, “E5” and “E7”, consistently show 5-10 fold less plasma cortisol in response to net confinement compared to normal male and female carp strains. Both E5 and E7 fish have enlarged head kidneys, which is caused by an increase in size and number of interrenal cells. The experiments and results described in this thesis aim to provide further insight into the genetic background of the 17α-hydroxylase deficiency, and the expression of genes involved in the stress response in P450c17 deficient common carp during and after stress. First, we describe the sequencing of the 17α-hydroxylase/17, 20 lyase gene, CYP17a1, in a normal, standard strain (“STD”) and one of the 17α-hydroxylase deficient strains (E5) of common carp. Two variants of the CYP17a1 gene were found. The nucleotide coding region of the CYP17a1.I variant contained 8 exons and 7 introns which is identical to the human CYP17. In total 3122 base pairs of the nucleotide sequence were determined. Variant I showed no differences between STD and E5, while variant II is missing exon 7 and part of exon 8 and contains a 3 bp insertion and 8 homozygous SNP’s downstream of exon 6. Next, we describe the stress response and gene expression in 17α-hydroxylase deficient E5 and normal STD common carp. The results show a significant increase of corticosterone levels in E5 carp in response to stress. Normal STD carp produce only small amounts of corticosterone. STD carp show a correlation between cortisol production and 11β-HSD2 mRNA expression during the stress response. In contrast, 11β-HSD2 expression is significantly lower in E5 fish and stays at a constant level during confinement. Real-time PCR analysis of StAR and 3β-HSD show a significantly higher expression of these enzymes in E5 during and after net confinement, but P450c21 not, suggesting that transcription of P450c21 is not a limiting step in corticosterone production. Messenger RNA levels in P450c17a1.I are quite variable with a trend towards lower expression levels in E5, suggesting a dysfunction at the transcriptional level. In the last part of this thesis, we investigate the inheritance of interrenal hyperplasia and low cortisol response using backcross and gynogenetic progeny of heterozygote carriers of common carp. Six-month old backcross (BC5 and BC7) and double haploid (DH) progenies were sacrificed after one hour net-confinement, blood sampled, and dissected to determine sex and head kidney-somatic index. Values for cortisol and head kidney index showed a continuous distribution in BC and DH progeny. Values for corticosterone, on the other hand showed a very clear segregation pattern in high and low responders, consistent with a single gene model. There was a significant difference in mean cortisol level between high (H) and low (L) corticosterone responders in BC and DH progeny groups. Surprisingely, H responders were predominantly male, while L responders were female or intersex. These results confirm that 17α-hydroxylase deficiency is inherited as a recessive mutation, and that 17α-deficiency and sex reversal are either caused by the same mutation (pleiotropy) or by closely linked genes.

    Genotyping and evaluation of Pleurotus ostreatus (oyster mushroom) strains
    Sonnenberg, A.S.M. ; Hendrickx, P.M. ; Sumiati, E. - \ 2005
    Horst : PPO Paddestoelen (PPO Publication / Applied Plant Research, Mushroom Research Unit no. 2005-18) - 29
    pleurotus ostreatus - genotypen - stammen (biologisch) - mycologie - paddestoelen - genotyping - pleurotus ostreatus - genotypes - strains - mycology - mushrooms - genotyping
    Oyster mushrooms (Pleurotus ostreatus) represent one of the most popular mushroom species grown in Indonesia. There is a need for strains that are better adapted to the climate conditions at Java, where most mushrooms in Indonesia are produced. Strains that can produce mushrooms at 22 to 28 oC and have a good yield and quality would improve the profit of mushroom growers substantially. In order to find strains that can be used for Indonesian growing conditions a large number of available strains were genetically examined.
    Breeding for improved production of Nile tilapia (Oreochromis niloticus L.)
    Rutten, M.J.M. - \ 2005
    Wageningen University. Promotor(en): Johan van Arendonk; Johan Verreth, co-promotor(en): Henk Bovenhuis; Hans Komen. - [S.I.] : S.n. - ISBN 9789085042198 - 122
    oreochromis niloticus - tilapia - selectief fokken - genetische verbetering - lichaamsgewicht - stammen (biologisch) - genetische analyse - genetische diversiteit - lichaamsafmetingen - genetische parameters - dierveredeling - visteelt - oreochromis niloticus - tilapia - selective breeding - genetic improvement - body weight - strains - genetic analysis - genetic diversity - body measurements - genetic parameters - animal breeding - fish culture
    The aim of this thesis was to generate knowledge that supports the design of breeding programs for Nile tilapia targeting genetic improvement of body weight and fillet yield to serve the European market. To this end, both the genetic variation and the performance levels of different strains of tilapia were investigated within intensive recirculation systems. Molecular genetic variation was investigated by use of microsatellite markers on four domesticated strains of tilapia. Moderate to great genetic differentiation was found and all strains had added value for the total genetic diversity.

    To enable phenotypic selection for fillet weight- and yield based on body measurements, phenotypic relationships between body measurements and fillet weight and fillet yield were investigated. Strong, almost linear, relationships between body measurements and fillet weight were found, but relationships with fillet yield were weak. Prediction models for fillet weight were accurate (R 2 =0.95) but not for fillet yield (R 2 =0.38) meaning that phenotypic selection for fillet weight is possible but hard for fillet yield. Genetic parameters for body weight, fillet weight,filletyield and body measurements were estimated to evaluate the potential of mass selection for fillet traits based on body measurements. The accuracy of a selection index including only body weight indicated that in this way almost the same amount of the selection response can be achieved compared to what hypothetical direct selection for fillet weight would. The use of only width in the selection index would result in 8.5% lower selection response than the use of body weight. It was concluded that body weight is the best predictor for fillet weight compared to body measurements.

    Genetic parameters for body weight at all ages ranging from 100 days to 326 days were estimated using a random regression model with covariance functions. The heritability of body weight was fairly constant around 0.2, which offers good prospects for selection on body weight. Genetic correlations were estimated between all ages and showed that early selection results in higher selection response than direct selection, when the target trait is body weight at the age of 326 days. Furthermore, evidence was found for genetic differences in growth patterns of fish of different strains. Phenotypic differences in body weight between male- and female fish were significant already at early ages (100 days). Results from a bivariate genetic analysis suggested that body weight in male and female fish is most likely controlled by the same genes since genetic correlations were high (>0.85) at all five measurement dates. Prospects to decrease the difference between mature male- and female body weight by selection, to reduce the total variation, are therefore unfavorable in Nile tilapia.

    New methodology to estimate variance components for genetic effects of competition was applied to Nile tilapia. No genetic variation for competitive behavior was found although environmental variation for competitive behavior could clearly be detected. This methodology is potentially very interesting for breeding in aquaculture, because no observations on behavior are required.

    Finally, the advantages and disadvantages of three selection strategies are discussed in terms of necessary facilities, workload and selection responses. It was argued that when traits measurable on live animals are targeted for genetic improvement, mass selection offers a cheap and simple strategy that can result in relatively high selection responses. However, when more complicated traits are desired, both family- and BLUP selection offer better possibilities depending on the trait of choice.
    Stammencollectie PPO bron van kennis
    Baars, J.J.P. ; Sonnenberg, A.S.M. - \ 2003
    Paddestoelen : onafhankelijk vakblad voor Nederland en België 2003 (2003)11. - ISSN 1380-359X - p. 7 - 7.
    agaricus - eetbare paddestoelen - stammen (biologisch) - wilde stammen - lijnen - stamverschillen - verzamelen - identificatie - cultivaridentificatie - conservering - genetische variatie - landbouwkundig onderzoek - edible fungi - strains - wild strains - lines - strain differences - collection - identification - cultivar identification - conservation - genetic variation - agricultural research
    De stammencollectie van Praktijkonderzoek Plant en Omgeving omvat meer dan 6.500 schimmelstammen van voornamelijk champignon en oesterzwam. Daarnaast nog circa 200 stammen van andere soorten paddestoelen. Het beheer van de collectie en het onderzoek zijn belicht
    Biological nitrogen fixation of soybean in acid soils of Sumatra, Indonesia
    Waluyo, S.H. - \ 2000
    Agricultural University. Promotor(en): W.M. de Vos; L. 't Mannetje; L.T. An. - S.l. : S.n. - ISBN 9789058082954 - 151
    glycine max - sojabonen - bodembiologie - stikstoffixatie - stikstofbindende bacteriën - rhizobium - bradyrhizobium - inoculatie - entstof - biochemische technieken - dna-fingerprinting - stamverschillen - stammen (biologisch) - zaadbehandeling - omhullen - zure gronden - bodemaciditeit - bekalking - sumatra - indonesië - glycine max - soyabeans - soil biology - nitrogen fixation - nitrogen fixing bacteria - rhizobium - bradyrhizobium - inoculation - inoculum - biochemical techniques - dna fingerprinting - strain differences - strains - seed treatment - pelleting - acid soils - soil acidity - liming - sumatra - indonesia

    The aim of this study is to improve soybean cultivation in transmigration areas, especially in Sitiung, West Sumatra. However, these soils are very acid, and have a high P-fixing capacity. To reduce the amounts of fertilisers, normally 5 - 7 ton lime ha -1 and 100 kg P as TSP, seed, pelleted with lime (60 kg ha -1 ) and TSP (10 kg ha -1 ), was introduced. In this way only 2 ton lime ha -1 are required.

    Soybean can fix nitrogen (BNF) in symbiosis with ( Brady ) Rhizobium bacteria. However, these acid soils in general, have low numbers of ( Brady ) Rhizobium . By inoculating the soils with ( Brady ) Rhizobium , BNF of soybean, and yield, were considerably improved.

    A study was made of the indigenous ( Brady ) Rhizobium population in view of the following:

      Although at the beginning the numbers may be low, by repeated soybean cultivation, the numbers will increase, and they may interfere with inoculation of effective ( Brady ) Rhizobium strains.These indigenous ( Brady ) Rhizobium are adapted to local stress conditions, and they may be useful for the improvement of strains, to be used as inoculants.

    Using molecular techniques, indigenous strains derived from soil samples from old soybean areas (Java) and from new soybean areas (Sumatra) were classified in more detail. Most likely B. japonicum is the dominant strain in Java while in Sumatra B. elkanii is more present. A Sinorhizobium fredii -like strain was isolated from one soil sample from Java.

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