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Search Results: 1 - 10 of 191259 matches for " D Fourie "
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Susceptibility of South African dry bean cultivars to bacterial diseases
D Fourie
African Crop Science Journal , 2011,
Abstract: Dry beans are an important crop in South Africa with the annual bean consumption being approximately 120 000 t. The crop is annually subjected to a number of biotic constraints such as bacterial diseases that can cause serious yield losses especially when the climate is conducive to diseases. The use of resistant varieties is an effective way of reducing the risk of crop failure and deployment of resistance requires knowledge on the susceptibility of cultivars. Twenty-one locally grown commercial dry bean cultivars were evaluated at Potchefstroom in South Africa to evaluate the resistance to common bacterial blight, halo blight and bacterial brown spot. Results indicated that South African cultivars differed in susceptibility to bacterial diseases. Cultivars Teebus, Cerillos, PAN 146 and PAN 159 were most susceptible to common bacterial blight with Monati and OPS-RS2 having low levels of resistance. Negative correlations (r=-0.44) (P<0.001) between disease ratings and yields were obtained in the common bacterial blight trial. Levels of resistance to halo blight were observed with small seeded cultivars generally being more resistant than large seeded types. A negative correlation (r=-0.35)(P=0.001) was obtained between halo blight rating and yield. Cultivars differed regarding susceptibility to bacterial brown spot with the majority having adequate resistance. Teebus, Cerillos, Bonus and PAN 159 were most susceptible, with Mkuzi exhibiting highest levels of resistance. No correlation was obtained between disease rating and yield. Although a number of cultivars exhibited field resistance to halo blight and bacterial brown spot, all cultivars were more or less susceptible to common bacterial blight. Common bacterial blight can be considered the most important bean bacterial disease in South Africa. Improvement of common bacterial blight resistance in South African cultivars is necessary for yield stability.
Application of molecular markers in breeding for bean common blight resistance in South Africa
D Fourie, L Herselman
African Crop Science Journal , 2011,
Abstract: Sequence characterised amplified region (SCAR) markers, linked to four independent quantitative trait loci (QTL) in XAN 159 and GN #1 Nebr. sel. 27, are available for indirect selection of resistance to common bacterial blight in Phaseolus vulgaris. Existing SCAR-markers, SU91, BC420, BC409 and SAP6, were evaluated for potential use in the South Africa breeding programme. Segregating populations of progenies developed through backcross breeding with cultivars Teebus and Kranskop as susceptible recurrent parents, and XAN 159 and Vax 4 as resistant donor parents were evaluated for presence of existing markers. Presence of all four markers in improved Teebus lines (XAN 159 derived) confirmed transfer of resistance in these lines. Marker BC420 was absent in XAN 159 derived Kranskop-lines. These lines were only moderately resistant when tested in the greenhouse, indicating that the QTL linked to this marker is important in order to obtain high levels of resistance. Progenies from backcrosses with Kranskop as recurrent parent using Vax 4 have exhibited high levels of resistance and presence of all markers found in Vax 4 confirmed transfer of resistance. Marker-assisted selection can successfully be implemented in breeding for common bacterial blight resistance in South African materials.
Pathogenic and genetic variation in Xanthomonas axonopodis pv. Phaseoli and its fuscans variant in Southern Africa
D Fourie, L Herselman
African Crop Science Journal , 2011,
Abstract: Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli and its fuscans variant, X. axonopodis pv. phaseoli var. fuscans is a widespread disease of dry beans in South Africa. Variation within pathogen populations has been reported and in order to breed for resistance it is important to investigate whether variation exists within the local pathogen population. One hundred and forty three common bacterial blight isolates from 44 localities in four countries, were inoculated onto eight Phaseolus acutifolius lines that differentiate between pathogenic races. This differential set was expanded to include resistant genotypes, XAN 159, GN #1 Nebr. sel 27, Wilk 2, Wilk 6, Vax 4, Vax 5 and Vax 6 and cv. Teebus as susceptible check. Genetic variation within nine selected Xap and Xapf isolates and a non-pathogenic Xanthomonas isolate, was studied using RAPD and AFLP analysis. Genotypes XAN 159, Wilk 2, Wilk 6, Vax 4, Vax 5 and Vax 6 were resistant to all isolates, while GN #1 Nebr. sel 27 and cv. Teebus were susceptible. Isolates varied in aggressiveness on cv. Teebus; however, the pathogenic reaction on the set of differentials indicated that all, but one isolate, grouped in what has been reported as race 2. Thus, results based on reaction of the majority isolates, suggest the absence of different races. However, the distinct differential reaction recorded for a single isolate, may prove to represent another, as yet unrecorded, race of this pathogen. Both RAPD and AFLP analyses revealed high frequency of DNA polymorphism among isolates and could distinguish between Xap, Xapf and a non-pathogenic isolate. Differences between Xap and Xapf isolates demonstrate that these are two distinct groups of bacteria.
Improvement of common bacterial blight resistance in South African dry bean cultiver teebud
D Fourie, L Herselman, C Mienie
African Crop Science Journal , 2011,
Abstract: Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli is an important seed-borne disease of dry beans in South Africa. Development of resistant cultivars is considered the best control measurement for the disease. Backcross breeding was used to improve BB resistance in the small white canning bean, cv. Teebus, using resistance sources XAN 159 and Wilk 2. High resistance levels in near-isogenic lines, developed in two independent breeding programmes, indicated successful transfer of resistance from both sources. Presence of SCAR-markers, SU91 and BC420, in 35 of 39 XAN 159 derived Teebus lines and all lines derived from Wilk 2, confirmed successful resistance transfer. AFLP studies conducted to determine genetic relatedness of two near-isogenic Teebus lines, showed a similarity of 96.2% with the maximum similarity between these lines and Teebus being 93.1%. One cultivar, Teebus-RCR2 with yield similar to Teebus and improved resistance to CBB has been released from the programme.
Characterisation of bacterial brown spot pathogen from dry bean production areas of South Africa
HTH Muedi, D Fourie, NW Mclaren
African Crop Science Journal , 2011,
Abstract: Pseudomonas syringae pv. syringae (Pss) causes bacterial brown spot (BBS) of beans (Phaseolus vulgaris L.), with yield losses of up to 55% in South Africa. Pss has a wide host range and for many of these, the pathogen has been biochemically and genetically characterised. However, few studies have been conducted on Pss isolated from beans. The aim of this study was to assess the biochemical and genetic variability of Pss isolates collected from dry bean producing areas in South Africa. Pure isolates were subjected to LOPAT tests and SyrB gene assessment. Biolog GN Microplates were used to assess carbon substrate utilisation. The SyrB gene was present in 42% of isolates. The Biolog GN Microplates showed biochemical variation among isolates. Variable genomic patterns were observed in 48.5% by the BOX A1R primer and in 37.1% of isolates by the ERIC 2 primer. Thus, variability exists in Pss populations of dry beans.
Efficacy of Once-Monthly Doses of Oral Afoxolaner and Afoxolaner/Milbemycin Oxime in a Well-Controlled Study for the Treatment of Canine Generalized Demodicosis  [PDF]
Steffen Rehbein, Christa de Vos, Frédéric C. Beugnet, Doug S. Carithers, Josephus J. Fourie
Open Journal of Veterinary Medicine (OJVM) , 2018, DOI: 10.4236/ojvm.2018.812022
Abstract: The efficacy of oral treatment with chewable tablets containing afoxolaner 2.27% w/w (NexGard, Merial, now part of Boehringer-Ingelheim) or 1.875% w/w of afoxolaner and 0.375% w/w milbemycin oxime (NexGard Spectra, Merial, now part of Boehringer-Ingelheim) was each assessed in eight dogs diagnosed with generalized demodicosis in this parallel group designed, blinded, randomized, single center negative controlled, efficacy study. Afoxolaner at the therapeutic dose (as close as possible to 2.5 mg/kg) was administered to Group 2 dogs, and afoxolaner (as close as possible to 2.5 mg/kg) with milbemycin oxime at 0.5 mg/kg was administered to Group 3 dogs on Days 0, 28 and 56. All dogs were observed once daily for general health starting on Day -7 until Day 84. All dogs were clinically examined on Days -7, -2, 14, 28, 42, 56, 70 and 84. Dogs were weighed on Days -7, -2, 27, 55, and 84. Live mite counts (based on five scrapings per dog and occasion) and clinical assessments, including photographic documentation, were performed on Days -2, 28, 56 and 84. Three monthly treatments with NexGard or NexGard Spectra against generalized demodicosis in dogs were highly effective resulting in a 99.9% and 100% efficacy against mites, respectively. After treatment with NexGard, only three live mites were recovered in five scrapings in one dog on Day 84. After treatment with NexGard Spectra, no mites were recovered in any scraping on any dogs in this group by Day 84. Both treatments resulted in a marked reduction of skin lesions and >90% hair-regrowth at three months after the initial treatment. Reduction of live mite counts was consistent with reduction in the extent and severity of the skin changes. Although the arithmetic mean mite numbers in the negative control group decreased slightly during the study, infection persisted in 7 of the 8 control dogs until Day 84. Both treatment groups of dogs showed a marked improvement of the associated dermatologic signs with steady improvement over the three-month treatment period.
A critique of social marketing in the non-profit development sector
L.M. Fourie,J.D. Froneman
Koers : Bulletin for Christian Scholarship , 2009, DOI: 10.4102/koers.v74i1&2.125
Abstract: In its struggle to find funding, non-profit organisations world-wide are increasingly using social marketing strategies. This approach potentially influences non governmental organisations (NGOs) and community based organisations (CBOs) in their communication with their “clients”, i.e. those persons and com-munities in need of development. Marketing strategies con-sequently become instruments in achieving social development, with as main premise that behaviour could be changed by means of persuasive, top-down communication. Social marketing, with its roots in marketing, has a strong focus on persuasion and favours top-down communication rather than dialogical communication strategies suggested by the par-ticipatory development communication approach. It is also questionable whether social marketing can be equated with the principles of a Biblically informed approach to communication. With these questions in mind, this article discusses Biblical views on communication and the participatory development communication approach. A critique of the social marketing approach is then offered. It is argued here that there is no clear-cut answer as to whether social marketing could be described as participatory. What is clear is that there are many different views on social marketing, as is the case with participatory approaches. It would thus seem more correct to place social marketing on a participation continuum, rather than to define it as being participatory and thus per definition ethical or not. Finally, a number of suggestions are made which could bring it more in line with the participatory communication approach as well as Biblical principles on com-munication.
The dilemma of ethical political communication in South African elections
L.M. Fourie,J.D. Froneman
Koers : Bulletin for Christian Scholarship , 2007, DOI: 10.4102/koers.v72i3.209
Abstract: In view of South Africa’s diversity, its unresolved issues of race and complex social legacy, election campaigns are highly sensitive. From a Reformed Christian perspective, a critical question is: To what extent is the political culture infused by the Biblical imperatives of brotherly love, respect and compassion? Given the growing use of adversarial political advertising the following two questions arise and are specifically addressed: Could it realistically be expected of Christian political communicators in a secular country such as South Africa to communicate with full respect to people at all times, or should they be excused if they try to win at all costs? and How do political theorists view the issue? In answering these questions, social responsibility and the need for social harmony as precondition for free and fair political activities, as well as a Biblical perspective on communication are addressed. In view of these theoretical points of departure the role of emotional messages is discussed and evaluated. It is argued that all advertising, but specifically political advertising in an emotionally charged atmosphere such as an election campaign, could have a direct negative impact on social harmony and is therefore Biblically unacceptable. Examples from previous South African general elections are discussed and evaluated from a Biblical viewpoint. It is argued that parties should not merely campaign with the aim of winning an election, but rather with the intention of respecting voters while campaigning. Simultaneously they could promote democracy within a fragile social context. Any victory outside of these parameters will not stand the test of a Biblical critique. However, it would seem extremely difficult, if not impossible, to prescribe in any detail which types of negative advertisements are acceptable and which are not.
The efficacy of collars impregnated with flumethrin and propoxur against experimental infestations of adult Rhipicephalus sanguineus on dogs
L.J. Fourie,D. Stanneck,I.G. Horak
Journal of the South African Veterinary Association , 2012, DOI: 10.4102/jsava.v74i4.524
Abstract: The efficacy of 2 sets of collars (Kiltix(R) Collar, Bayer AG), containing different plasticisers and impregnated with the acaricides flumethrin (2.25 %) and propoxur (10 %), was compared against adult Rhipicephalus sanguineus on experimentally infested, kennelled dogs. Thirty individually penned dogs were infested with 25 male and 25 female, unfed R. sanguineus. On the following day they were allocated to 3 groups of 10 dogs each on the magnitude of their tick burdens. Two days after infestation, medicated collars containing 1 of the plasticisers were fitted to 10 of the dogs and similar collars containing the other plasticiser were fitted to 10 others. The remaining 10 dogs were the untreated controls. Seven and 28 days after having fitted the collars, all dogs were re-infested with 50 unfed adult ticks of both sexes, and again at approximately 28-day intervals up to the 5th month, and then at approximately 14-day intervals during the 6th month. Efficacy was determined by comparing the mean number of live, attached ticks on the untreated control group with those on the collared dogs 2 days after each re-infestation. Immediate efficacy of the collars (Day +2) was > 95 %, and residual efficacy was > 98% up to and including Day +114, and > 93 % up to Day +170 on both groups of collared dogs. The mean tick counts on the 2 groups of collared dogs did not differ significantly (P < 0.0001) for any of the assessment days.
Ion Source Optimisation for Proton Beam Quality of the Van De Graaff Accelerator at iThemba LABS for Ion Beam Analysis  [PDF]
M. E. M. Eisa, J. L. Conradie, P. J. Celliers, J. L. G. Delsink, D. T. Fourie, G. de Villiers, K. A. Springhorn, C. A. Pineda-Vargas
World Journal of Nuclear Science and Technology (WJNST) , 2013, DOI: 10.4236/wjnst.2013.33014

The operating principles of the two duoplasmatron ion sources and the PIG source available for the Van de Graaff accelerator have been determined qualitatively, mainly by studying the extensive literature on ion sources. The main characteristics of the three sources have therefore been determined experimentally on an ion source test bench. Important parameters of the sources such as the pressure and temperature in different regions of the sources not measured, because of space limitations. However, in spite of these limitations in quantitative understanding of the sources, sufficient information to continue with the study of the beam transport through the Van de Graaff accelerator and its beamlines could be obtained from these measurements. With regard to beam intensity, lifetime and gas consumption the measurements showed that the hotcathode duoplasmatron is at present by far the most suitable source for the van de Graaff accelerator. The emittance of the ion source was measured with two slits, 90 mm apart, and a Faraday cup in the ion source test bench at an arc voltage of 83 V, an arc current of 1 Amp, a filament voltage of 24 V and an extraction voltage of 5 kV. The measured emittance for 90% of the beam intensity is 48π mm mrad. This figure will be used to calculate the beam transmission through the Van de Graaf accelerator. Different computer programs have been used for these calculations from the ion source through the terminal section, the accelerator and beam line up to the Nuclear Microprobe (NMP) for beam quality.

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