This database contains bibliographic descriptions of all Wageningen University PhD theses from 1920 onwards. It is updated on a daily basis by WUR Library.
Author abstracts and/or summaries are added to all descriptions. A link to the full text dissertation is added to the bibliographic description. In a few cases, no electronic version is available, mostly because of copyright issues.
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Abstract: Generally, tomato is considered sensitive to heat stress. During the development of the tomato male gametophyte, anther development and particularly the first stage of meiosis are the most sensitive phases. Our goal was to analyse the general molecular response to moderate heat stress (MHS) in tomato meiotic anthers and then characterise aspects of the response to heat in tolerant genotypes. Understanding the metabolic changes that occur in heat tolerant varieties/lines during heat stress is essential for the production of tomato crops adapted to variable temperature increases. First, cDNA-AFLP was employed to reveal a general spatial and temporal response to MHS in a standard cultivar. The results showed about 1% of the analysed genes having significant modulation (down-regulation) in expression after just 2h of stress. Several transcripts were identified and associated to a response to heat. Additional analyses revealed that the candidate genes are expressed in the tapetum, but also in other tissues (Chapter 3). The Combimatrix technology has been used to fingerprint differences in response to heat between a tolerant and a sensitive genotype, with the aim of detecting candidate tolerance genes. The microarray analysis also shows about 1% of the genes having a significant modulation in expression after 2h of stress, and that the tolerant genotype reacts with fewer transcriptomic changes and exhibiting high constitutive levels of transcripts involved in protection and thermotolerance. In the heat-tolerant genotype, the majority of changes in gene expression is represented by up-regulation, while in the heat-sensitive genotype there is a general trend to down-regulate gene expression, soon after MHS. The putative functions associated with the genes identified by cDNA-AFLP or microarrays indicate involvement of heat shock, metabolism, antioxidant and development pathways. Based upon the observed differences in response to MHS and on literature sources, we identified a number of candidate transcripts involved in heat-tolerance. A functional analysis of expression modulation by qRT-PCR was performed in several pairs of genotypes and the results confirm observations from microarray regarding gene modulation (Chapter 4). An experimental approach to obtain insight into the hormonal regulation of the response to heat is described in chapter 5. Additional observations and results are discussed in chapter 6.
Abstract: During the last century in the Netherlands milk production per cow has almost tripled. Accordingly, the amount of concentrates yearly fed per cow strongly increased. Furthermore, automation and robotisation has changed dairy management, especially by the introduction of automatic concentrate feeders and milking systems. A new management concept, emerging in the last decades, is Precision Livestock Farming (PLF). The objective of PLF is to optimize livestock production, by on-line monitoring and control of the production process, utilizing the technical possibilities of automation and robotisation. Nowadays, individual settings for daily concentrate supply and milking frequency are based on standards, ignoring individual variation in milk yield response on concentrate intake and milking frequency. This leads to the main hypothesis for this thesis research that profitability of dairy farming can be improved by utilizing information on individual variation in response. The first objective of this research was to quantify the individual variation in milk yield response to concentrate intake and milking interval length, in order to assess the economic prospects of applying individual optimal settings for concentrate supply and milking frequency. The second objective was the development and testing of adaptive models for on-line estimation of the actual individual response in milk yield to concentrate intake and milking interval length. The conclusion is that on-line estimation of the actual individual response in milk yield and milking duration is possible following a Bayesian approach for time series using an adaptive dynamic model. Besides estimation of the actual response the Bayesian approach adequately detects process deteriorations. Therefore, adaptive dynamic models provide a useful tool for control and monitoring of the dairy production process.
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