10 research outputs found
Putting the Phytophthora infestans genome sequence at work: multiple novel avirulence and potato resistance gene candidates revealed
No full text Individual variation in milk yield response to concentrate intake and milking interval length 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. In the first observational study (Ch. 2), data from 299 cows on four farms in the first 3 weeks of the lactation were collected. Individual response in daily milk yield to concentrate intake was analysed by a random coefficient model. During the first three weeks of lactation, considerable variation in individual milk yield response to concentrate intake was found on all four farms. An economic simulation was carried out, based on the estimated parameter values in the observational study. Individual economically optimized settings for concentrate supply were compared with conventional strategies for concentrate supply based on averaged population response parameters. Applying individual economic optimal settings for concentrate supply during early lactation, potential economic gain ranges from 0.20 to 2.03 €/cow/day. In a second observational study (Ch.3), data of normal uninterrupted milkings during one week from 311 cows kept in 5 separate herds on one farm were collected. The data set consisted of 4,915 records and random coefficient models were fitted to estimate the individual effects of milking interval on daily milk yield and milking duration. Between individuals, considerable variation in milk yield and milking duration was found in response to milking interval. Based on the estimated individual response, a simulation was carried out in order to optimize the utilization of an AMS for different herd sizes and occupation rates. Applying optimal individual milking intervals for a herd of 60 cows and an AMS operating at an occupation rate of 64%, the average milking interval reduced from 0.421 day to 0.400 day, the daily milk yield at the herd level increased from 1,883 to 1,909 kg/day, and milk revenues increased from 498 to 507 €/day. In the actual situation, the herd consisted of 60 cows. A further increase of daily milk revenues per AMS was possible by increasing the operation rate and/or herd size. The conclusion is that between dairy cows there is a considerable variation in effects of concentrate intake and milking interval length on milk yield and, consequently, milking duration. A marked increase in economic profits of dairy production is possible by improvement of the concentrate allocation and/or the utilisation of an AMS, applying optimal individual settings based on the actual individual response in milk yield. Development of adaptive models 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. In Ch. 4 adaptive dynamic models for on-line estimation of the actual individual milk yield response to concentrate intake and milking interval length were evaluated. The parameters in these models may change over time and are updated through a Bayesian approach for on-line analysis of time series. Time series data of daily milk yield during the first 200 days of lactation from 17 cows were analysed with different adaptive dynamic models. Three models were evaluated: a model with linear terms for concentrate intake and length of milking interval, a model with linear and quadratic terms, and an enhanced model in order to obtain more stable parameter estimates. The linear model was only useful for forecasting milk production and the estimated parameters of the quadratic model turned out to be unstable. The parsimony of the enhanced model lead to far more stable parameter estimates. In Ch. 5 an adaptive dynamic model was used for time series analysis of herd mean daily milk yield, in order to quantify the impact of heat stress and to assess the potential for monitoring and control of milk production. Time series data of daily milk yield from 2003 to 2006 were collected on six experimental research farms in The Netherlands. The impact of heat stress was quantified in terms of critical temperature, duration and loss in milk yield. The estimated critical temperature was 17.8 oC, the duration was 5.5 days, and loss in milk yield 31.4 kg milk/cow/year, averaged over farms. Besides estimation of the impact of heat stress, level and trend, including a weekly cyclical pattern were estimated to evaluate the production process. The Bayesian approach for on-line analysis of time series comprises also a procedure for the detection of potential outliers and other deteriorations that might be promising for monitoring the production process. Outliers and other process deteriorations are adequately detected by this monitoring procedure. 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. </p
Anesthesiologists' demography in French-speaking Sub-Saharan Africa: the impact of fifteen years of Belgo-Beninese cooperation
No full textBelgium has been collaborating with the French-speaking University of Abomey-Calavi in Cotonou (Republic of Benin) for 15 years to train anesthesiologists for Sub-Saharan French-speaking African countries. At the end of the nineties, Sub-Saharan Africa was the only part of the world with a decreasing number of anesthesiologists. Thanks to various financial supports coming mainly from Belgian governmental cooperation funds, the program has been successful in reversing the demographic trend and even started a multiplying effect through the creation of schools for nurse-anesthetists, and through the creation of new training centers for physician anesthesiologists. Sixty-nine anesthesiologists from 13 countries graduated from Cotonou, 59 (85.5%) of whom actually choose to work in Africa. At least 40 of them teach anesthesia, playing a key role in the creation of new schools and training centers
Structural and taxonomic diversity predict above‐ground biomass better than functional measures of maximum height in mixed‐species forests
No full textAims: Mixed-species forests are known to be highly productive systems because of their high species diversity, including taxonomic diversity (species richness) and structural diversity. Recent empirical evidence also points to plant maximum height, as a functional trait that potentially drives forest above-ground biomass (AGB). However, the interrelations between these biotic variables are complex, and it is not always predictable if structural diversity attributes or functional metrics of plant maximum height would act as the most important determinant of stand biomass. Here we evaluated the relative importance of structural diversity attributes and functional metrics of plant maximum height (Hmax) in predicting and mediating AGB response to variation in species richness in mixed-species forests, while also accounting for fine-scale environmental variation.Location: Northern Benin.Methods: We used forest inventory data from mixed-species stands of native and exotic species. We quantified structural diversity as coefficient of variation of tree diameter at breast height (CVdbh) and of height (CVHt). For plant Hmax, we computed three metrics: functional range (FRHmax), functional divergence (FDHmax) and community-weighted mean (CWMHmax). We used topographical variables such as elevation and slope to account for possible environmental effects. Simple and multiple mixed-effects models, and structural equation models were performed to assess the direct and indirect links of AGB with species richness through structural diversity attributes and functional metrics of plant Hmax.Results: Species richness and CVdbh were positively related to AGB, while functional metrics of plant Hmax were not. Structural equation models revealed that species richness influenced AGB indirectly via CVdbh, which alone strongly promoted AGB. Elevation only had a positive direct effect on AGB. While increasing species richness enhanced CVdbh and functional measures of plant Hmax, there was no support for the latter mediating the effects of species richness on AGB.Conclusion: Structural diversity has a significant advantage in predicting and mediating the positive effect of species richness on AGB more so than functional measures of plant Hmax. We argue that structural diversity acts as a mechanism for the species richness–AGB relationship, and that maintaining high structural diversity would enhance biomass in mixed-species forests
Anesthesia in French-speaking Sub-Saharan Africa: An overview
No full textThe situation of Anesthesiology in Sub-Saharan Africa is unique in that nowhere else in the world has the absolute numbers of anesthesiologists decreased during the nineties. Most anesthesia services to the populations of these 17 poor countries are provided by nurse-anesthetists, either certified or trained on the job. Their mean age often exceeds 40, which leads to expect an acute shortage within fifteen years. Experienced anesthesiologists are now so few that, in most countries, the critical mass of knowledgeable specialists no longer exists to train new anesthesia professionals. This summary of local surveys provides a brief overview of current workforce, institutions, drugs and material constituting the daily environment of our colleagues. Challenges are outlined, with special emphasis on brain drain. Solutions are proposed, underlining the promising role of a few anesthesia schools, the need for young anesthesiologists to enter teaching, and the expectations they are supposed to meet. © Acta Anœsthesiologica Belgica, 2007
Pediatric anesthesia in developing countries: experience in the two main university hospitals of Benin in West Africa
No full textMaritime trade and biological invasions management: a Seaport Platform of Environmental Surveillance in Cotonou, Benin, as a pilot multi-stakeholder initiative
No full textMaritime Trade and Biological Invasions Management: A Seaport Platform of Environmental Surveillance in Cotonou, Benin, as a Pilot Multi-Stakeholder Initiative
No full textThe Seaport Platform of Environmental Surveillance (PPSE, or Plateforme Portuaire de Surveillance Environnementale in French) was officially inaugurated in Cotonou Seaport (CS), Benin, by the end of 2021. To our knowledge, this platform is the first laboratory dedicated to the monitoring and management of invasive species to be built inside the walls of an African seaport. Its creation has benefitted from a combination of favorable factors, and its existence has resulted from a long-term, multi-stakeholder and still ongoing process that we here describe and analyze. We believe that the PPSE is an innovative science-guided operational initiative that may be useful to replicate in other settings throughout the world
The Phytophthora infestans avirulence gene PiaAvr4 and its potato counterpart R4
No full textThe potato late blight disease that is caused by the oomycete pathogen Phytophthora infestans is a major threat for potato crops worldwide. In recent years research on oomycete plant pathogens was boosted by the availability of novel genomic tools and resources for several oomycete genera, such as Phytophthora, Hyaloperonospora, Pythium and Aphanomyces. This has led to the identification of genes involved in diverse biological processes such as sporulation, mating, signaling and pathogenesis. One of the approaches that breeders use to obtain late blight resistant potato cultivars is the introgression of resistance traits from wild Solanum species into the cultivated potato Solanum tuberosum. The pathogen, however, is able to circumvent this resistance; it is often lost shortly after introduction of new cultivars. To better understand the mechanisms underlying this loss of resistance it is of utmost importance to gain insight into the characteristics of the cognate avirulence (Avr) genes of the pathogen. According to the gene-for-gene model Avr genes encode effectors that trigger resistance responses mediated by resistance (R) genes. This thesis first describes the identification of a P. infestans Avr gene, in particular the elicitor activity of the encoded effector protein, the domain structure of the effector and its putative sub-cellular localization. In the second part the recognition specificity of the corresponding R gene and the identification of a marker linked to this R gene are described. Chapter 1 summarizes the advances in oomycete genomics in recent years and the tremendous progress that has been made in gene discovery in oomycete plant pathogens. It describes the different oomycete species that have been studied in more detail and assesses which species are suitable model species for research on oomycete-plant interactions. The identification of the P. infestans avirulence gene PiAvr4 is presented in Chapter 2. PiAvr4, which encodes an RXLR-dEER effector protein, was isolated by positional cloning. AFLP markers were used for landing on BACs and cDNA-AFLP markers pinpointed the gene of interest. Transformation of race 4 strains with PiAvr4 resulted in transformants that are avirulent on the R4 differential of the Mastenbroek differential set (clone Ma-R4). Moreover, in planta expression of PiAvr4 resulted in a necrotic response on clone Ma-R4 but not on plants lacking R4 such as Bintje. All together this proves that PiAvr4 is the avirulence gene that corresponds to the R gene present in clone Ma-R4. In many identified avirulence proteins one or a few amino acid changes in the protein abolish avirulence function. In case of PiAvr4, race 4 strains have frame shift mutations in the open reading frame, resulting in a truncated protein that is not functional as avirulence factor. Effectors within the RXLR-dEER family are rapidly evolving. The selective pressure is targeted predominantly on the C-terminal region of these proteins. Despite this selective pressure the majority of these proteins carry motifs that can be distinguished using Hidden Markov Models searches. They are named W, Y and L motifs after the conserved tryptophan (W), tyrosine (Y) and leucine (L) residues, respectively. As described in Chapter 3 PiAvr4 carries three W motifs and a single Y motif. The motifs together with their flanking regions were tested for activity on Ma-R4 plants. Agroinfection of constructs carrying the W2 motif in combination with either the W1 or W3 motif resulted in a necrotic response. Moreover, we showed that the PiAvr4 homolog PmirAvh4, isolated from Phytophthora mirabilis was also able to elicit a necrotic response on the Ma-R4 potato clone. For several Phytophthora RXLR-dEER effectors it was demonstrated that these proteins are targeted into the host cell and that the RXLR-dEER motif is required for translocation. In Chapter 4 we investigated whether PiAvr4 and IPI-O, like other RXLR-dEER effectors, are also targeted into the host cell. A race 4 P. infestans isolate was transformed with constructs encoding either PiAvr4 or IPI-O fused to a monomeric red fluorescent protein (mRFP) at the C-terminus. Fluorescence microscopy of these transformants showed no specific mRFP fluorescence in free living, non-sporulating mycelium. However, in germinating cysts, the tips of germ tubes and appressoria showed mRFP fluorescence, and during infection of etiolated potato plantlets localized fluorescence was visible at the haustorial neck. Haustoria are highly specialized infection and feeding structures that are in close contact with the plant cell and have a putative role in delivering effector proteins into the host cell. In order to monitor the development of the infection a novel experimental set-up was developed. In this method etiolated in vitro grown potato plantlets are inoculated with P. infestans, which has the advantage that there is no autofluorescence of chlorophyll that masks the mRFP fluorescence and thus disturbs the microscopic analysis in green plant tissues. The lack of chlorophyll does not seem to interfere with infection; zoospores are capable to encyst and to germinate, and the etiolated tissues are readily colonized by P. infestans. The recognition specificity of R4 potato differentials is described in Chapter 5. Initially two different potato clones were developed as R4 differentials; The Mastenbroek differential set, developed in the Netherlands, contains the clone Cebeco44-31-5 (designated as Ma-R4) and the Black differential set, developed in Scotland, contains clone 1563 c (14) (designated as Bl-R4). Virulence assays using several wild type P. infestans strains revealed that the Bl-R4 clone is susceptible to all isolates that are avirulent on clone Ma-R4. Only one single isolate was found to be avirulent on clone Bl-R4, but virulent on Ma-R4. Moreover, in transient expression assays with binary PVX constructs carrying PiAvr4, the Ma-R4 clone but not the Bl-R4 clone responded with an HR. Similar to the R3 locus two different recognition specificities seem to exist for R4. The R3a and R3b genes are located on one locus but whether this is the case for the two R4 genes (named R4Ma and R4Bl, respectively) remains to be determined. Resistance to P. infestans strains carrying PiAvr4 segregates in an 1:1 ratio in two independent potato F1 populations suggesting that R4Ma resistance is determined by a single dominant locus. More in depth studies on the recognition of PiAvr4 by its cognate R protein are hampered by the fact that the resistance gene R4Ma has not yet been identified. In Chapter 6 nucleotide binding site (NBS) profiling was used to generate R4Ma-associated markers. NBS profiling is a biased approach based on PCR amplification of conserved NBS motifs in R genes and R gene homologs. In a bulked segregant analysis, DNA of resistant and susceptible F1 progeny was pooled and used as template for NBS profiling. Several candidate markers were found but eventually one amplified fragment was found to co-segregate with resistance mediated by R4Ma. DNA sequencing of this fragment revealed high similarity to BAC sequences that are mapped to potato chromosome 12. Moreover, the R4Ma marker is homologous to members of the Rx/Gpa2 gene family. Chapter 7 focuses on the secreted effectors of plant pathogenic oomycetes, with special attention to RXLR-dEER effectors, and the role of these proteins in pathogenesis. The RXLR-dEER effector family is rapidly evolving and comprises all secreted oomycete avirulence proteins that are identified up till now. There is now ample evidence that oomycetes utilize the RXLR-dEER domain to deposit effectors inside host cells. Furthermore, this chapter discusses the experimental results described in this thesis in the light of present knowledge on gene-for-gene interactions, effector recognition and late blight resistance. <br/
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Sustainable tourism development management in Central Africa: a case study of the tourism industry in Cameroon
No full textThe tourism industry in sub-Saharan Africa has been experiencing one of the fastest growth rates in the last decade at more than 10% in 2006, +7% in 2007 and +5% in 2008 and 2009 respectively and this positive trend is predicted to continue in future in spite of the present global recession. However, there are significant variations in tourism growth between the various countries and different sub-regions. Until now, there has been no detailed examination by researchers to find out the reasons for these variations in general and the stagnation and even decline in tourism growth observed in countries of the Central African sub-region in particular, which have recognised natural and socio-cultural potentials of developing a thriving sustainable tourism industry. Using Cameroon as a case study, this research examines the reasons of this stagnation in the Central African sub-region, and explores the possibility of tailoring, adapting and/or applying the key concepts of sustainable tourism in developing and managing the tourism industry in the Central African sub-region which is still at an early stage of development through the conception of a strategic framework for sustainable tourism development management in Cameroon. The principal objectives of the thesis are: a. To identify and outline the growth potential of the tourism industry in Cameroon as a means of improving the socio-economic conditions of the local communities. b. To examine the contradictions and challenges facing the development of a viable sustainable tourism industry in Cameroon. c. To determine how far sustainable tourism concepts successfully applied in other countries can be adapted and used in developing and managing the tourism potential of Cameroon in particular, and its sub-region
