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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.

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    Diversity and biological control of Sclerotium rolfsii, causal agent of stem rot of groundnut
    Lê, N.C. - \ 2011
    Wageningen University. Promotor(en): Francine Govers, co-promotor(en): Jos Raaijmakers. - [S.l.] : S.n. - ISBN 9789461731074 - 152
    arachis hypogaea - aardnoten - plantenziekteverwekkende schimmels - athelia rolfsii - genetische diversiteit - biologische bestrijding - bacteriën - arachis hypogaea - groundnuts - plant pathogenic fungi - athelia rolfsii - genetic diversity - biological control - bacteria

    Groundnut (Arachis hypogaea L.) is an economically important legume crop in Vietnam and many other countries worldwide. Stem rot disease, caused by the soil-borne fungus Sclerotium rolfsii Sacc., is a major yield limiting factor in groundnut cultivation. Current control methods mostly rely on the extensive use of fungicides and on cultural practices. Both methods are not always effective and repeated fungicide use can lead to resistance development in the pathogen population. To further improve disease control and to reduce the use of chemical pesticides in groundnut cultivation, the feasibility of biological control of stem rot was investigated. The project initially focused on evaluating the occurrence and severity of stem rot disease in farmer fields in central Vietnam. It appeared that 5-25% of the groundnut plants in farmer fields in central Vietnam were infected by S. rolfsii. From infected fields, S. rolfsii isolates were collected and their genetic diversity was investigated as well as the variation in sensitivity to tebuconazole, a fungicide commonly used to control stem rot disease. Based on ITS-rDNA sequence analyses, three distinct groups were identified among a total of 103 randomly selected S. rolfsii field isolates, with the majority (n=90) in one ITS group. S. rolfsiiisolates originating from groundnut, tomato and taro were all pathogenic on groundnut and relatively sensitive to tebuconazole. However, the isolates displayed substantial diversity in various genetic and phenotypic traits, including mycelial compatibility, growth rate, and sclerotial characteristics.

    Subsequently, the efficacy of various beneficial bacteria to suppress stem rot disease was investigated. First, the biocontrol activity of well-characterized antagonistic Pseudomonas strains was evaluated in vitro and in growth chamber, nethouse and field experiments. Secondly, indigenous groundnut-associated bacteria were isolated, their diversity was investigated and their antifungal activity was analysed in nethouse and field experiments in central Vietnam. Finally, endophytic bacteria living inside groundnut nodules were isolated, characterized and tested for biocontrol and plant growth promotion under field conditions. For several of the most promising bacterial strains, the mechanisms involved in biocontrol of stem rot disease were investigated.

    The experiments conducted with well-characterized Pseudomonas strains showed that only phenazine-producing Pseudomonas chlororaphis strain Phz24 and Pseudomonas sp. strain SH-C52, producing the chlorinated lipopeptide thanamycin, inhibited hyphal growth of S. rolfsii and suppressed stem rot disease. Mutants of these strains that were deficient in phenazine or thanamycin production did not show any activity against S. rolfsii, indicating that these metabolites play an important role in suppression of stem rot disease. Other Pseudomonas strains producing structurally different lipopeptides did not or only marginally inhibit growth of S. rolfsii. These results suggested variation in sensitivity of the stem rot pathogen S. rolfsii for structurally different lipopeptides produced by Pseudomonas.

    Indigenous groundnut-associated bacteria with activity against S. rolfsii were classified by 16S-rDNA sequence analysis as γ-Proteobacteria (Pseudomonas), Bacteroidetes (Chryseobacterium), and Firmicutes (Bacillus). Among these indigenous bacterial genera, Pseudomonas sp. R4D2 consistently reduced stem rot disease under nethouse and field conditions. The genes and bioactive compounds involved in the biocontrol activity of strain R4D2 have not been identified yet, but phenotypic analyses suggest that biosurfactant production plays a central role. Chryseobacterium sp. R4B3 did not reduce stem rot disease in nethouse experiments, but was effective in suppression of stem rot disease under field conditions. Finally, the two indigenous isolates that were identified as Bacillus spp. did not reduce stem rot disease in nethouse experiments, but were effective in disease control under field conditions. Furthermore, both Bacillus strains significantly increased pod yield with dry weight increases of up to 30% relative to the control.

    Endophytic bacteria of groundnut nodules appeared to be genetically diverse. The majority was closely related to Sphingomonas while others were classified as Rhizobium, Burkholderia, Stenotrophomonas, and Sphingobacterium species. In nethouse experiments, occasionally, nodule formation on roots was observed on groundnut plants grown in soil supplemented with some of these endophytic isolates, but further analyses are required to establish that these isolates are indeed responsible for nodule formation and nitrogen fixation. For two of the identified endophytic isolates, i.e. Rhizobium sp. HR9 and Sphingomonas sp. HR32, field experiments showed that both strains were not effective against stem rot and other soil-borne diseases of groundnut, but significantly reduced leaf spot diseases caused by Cercospora and Cercosporidium spp. Application of these two endophytic bacterial strains also led to increases in pod yield of groundnut under field conditions.

    In conclusion, several of the bacterial strains tested in this study, in particular Pseudomonas and Bacillus spp., significantly improved pod yield of groundnut by 10 to 30%. The consistency in pathogen control and yield increase observed in two independent field experiments at two different locations in two consecutive years, holds great promise for further development of these bacterial strains as key components of an integrated strategy to manage multiple diseases of groundnut and to improve yield.

    Allergenicity in food allergy : influence of food processing and immunomodulation by lactic acid bacteria
    Vissers, Y.M. - \ 2011
    Wageningen University. Promotor(en): Harry Wichers; Huub Savelkoul, co-promotor(en): E.N.C. Mills. - [S.l.] : S.n. - ISBN 9789085859161 - 226
    voedselallergieën - voedselverwerking - immunotherapie - aardnoten - melkzuurbacteriën - food allergies - food processing - immunotherapy - groundnuts - lactic acid bacteria

    Allergic diseases such as allergic rhinitis, allergic asthma, atopic eczema and food allergy have become an increasing health problem world-wide, affecting between 20-30% of the total population. Peanut allergy (prevalence ~1%) is a common and persistent food allergy accounting for severe allergic reactions. Peanuts are often consumed after thermal processing (e.g. boiling, roasting) which can alter the protein structure and change its immunoreactivity and allergenicity. In vitro diagnostic testing, however, is generally performed using the native, unprocessed protein and more knowledge on the effect of processing on allergens is necessary to improve these diagnostic procedures. In addition, rationally designed processing could also lead to reduction of the allergen content in certain products and therefore be an effective food technological approach in allergy management. Another approach in allergy management is the use of immunomodulating foods, such as probiotics. There are indications that probiotics, e.g. specific lactic acid bacteria, could be beneficial for many conditions, including different clinical expressions of allergy.
    Chapter 1 gives an overview of several aspects of allergy with a focus on food allergy. Firstly the basic mechanism and the involved immune cells are discussed, after which the prevalence of food allergy in the context of the EuroPrevall project is described. Different food allergens are discussed with an emphasis on the allergens from peanut and different methods are described to assess the potential allergenicity of proteins under widely used processing conditions, including heating and the Maillard reaction. Lastly, different methods to prevent or treat allergies are discussed with a special emphasis on immunomodulation by lactic acid bacteria. This introduction chapter is concluded with the research aim and thesis outline.

    Section 1: Influence of processing on allergenicity of proteins
    In our first study, described in Chapter 2, Ara h 2/6 was purified from raw peanut and heated in solution (boiling) in the presence or absence of glucose. Ara h 2 and 6 were also purified from roasted peanuts for comparison. Structural changes, the capacity to induce cell proliferation and cytokine production, and IgE-binding and IgE cross-linking capacity were evaluated. Although no effect of processing on T-cell reactivity was observed, heat-induced denaturation reduced the IgE-binding and cross-linking capacity. Interestingly, the soluble fraction of the Ara h 2/6 isolated from roasted peanuts retained the conformation and allergenic activity of the native protein.
    In Chapter 3 similar methods were used to assess the effect of heating and glycation on Ara h 1. Heating in solution, irrespective of their level of glycation, resulted in formation of aggregates having reduced IgE-binding and cross-linking capacity, while T-cell reactivity was retained. The soluble fraction of Ara h 1 isolated from roasted peanuts appeared to be highly denatured, formed more globular and smaller aggregates, and showed no evidence of glycation. However, these smaller aggregates retained IgE-binding capacity, unlike the aggregates formed after heating and glycating purified Ara h 1. These results could account for observed differences between boiled and roasted peanuts and suggest that other modifications than the Maillard reaction affect the allergenicity of Ara h 1.
    As peanuts are often consumed after roasting, the wet-thermal processing procedures, employed in the two previous described studies, were related to the effect of thermal treatment and Maillard reaction under low moisture conditions, which is described in Chapter 4. The extensive heating at low moisture resulted in hydrolysis of both Ara h 1 and Ara h 2/6. However, in contrast to Ara h 2/6, soluble Ara h 1 formed large aggregates. Thermally treated Ara h 2/6 had both a lower IgE-binding and degranulation capacity compared to the native form, and the presence of glucose during heating partly counteracted both the decrease in IgE-binding and degranulation capacity. The IgE-binding capacity of Ara h 1 was also decreased; however, the basophil degranulation capacity increased significantly. This demonstrates the importance of including degranulation assays in addition to IgE-binding assays, when assessing allergenic potency of allergens. In addition, we here propose a role for large aggregates in the increased IgE-cross-linking capacity of individual allergens.
    Chapter 5 describes the effect of glycation on the immunoreactivity and basophil degranulation capacity of Cor a 11, the 7S globulin from hazelnut (and thus a homologue of Ara h 1). Three processing methods (heating at low moisture content at 37, 60 and 145°C) resulted in proteins with increasing degrees of glycation. Glycation at 37°C did not influence the specific IgG or IgE binding, while both were decreased after heating at 60°C and 145°C. However, heating at 145°C in the absence or presence of glucose resulting in the formation of aggregated structures, increased the basophil degranulation capacity of Cor a 11 using sera high in Cor a 11 specific IgE, but not when using sera from peanut allergic patients low in Cor a 11 specific IgE. Therefore, this study besides showing the importance of the use of a combination of tests also indicated the importance of using well-characterized sera as a source of IgE.
    In Chapter 6 we focused on the clinical features of all our clinically well-defined peanut allergic patients of which immune cells and sera were used for the previously described studies. In addition, soy allergic patients were included and an extensive IgE profile was determined for all patients. Gly m 4 (Bet v 1 homologue from soy) sensitization was suggested to be an important indicator of severe soy allergy in the soy allergic patients, while in peanut allergic patients sensitization to allergens from soy and pea extract nor Gly m 5 and 6 was found to have a good diagnostic specificity. This is likely due to the presence of clinically non-relevant cross-reactivity between peanut-specific IgE and homologues soy and pea components.

    Section 2: Immunomodulation by Lactobacillus strains
    In the first in vitro study, described in Chapter 7, initially 51 Lactobacillus strains were screened of which 8 were selected and tested for their immunomodulating effects on peripheral blood mononuclear cells (PBMC) of healthy donors. All tested Lactobacillus strains were capable of inducing the production of IL-1β, IL-10, IFN-γ and TNF-α. Clear strain-specific effects were observed with L. plantarum strains showing significantly higher induction capacity of IFN-γ, IL-12 and TNF-α compared with L. acidophilus strains. We therefore concluded that especially L. plantarum strains are promising candidates in IgE-mediated allergy by their stimulation potential of the T-cell response toward a putative Th1 response.
    As healthy subjects, in contrast to allergic individuals, are assumed to finely regulate the Th1/Th2 balance by inducing sufficient Treg cell activity, immunomodulatory effects of six selected Lactobacillus strains were investigated on PBMC of pollen-allergic patients in Chapter 8. All strains could modulate PBMC to induce innate cytokine production and in addition, all strains had the ability to repress IL-13 production. Again a differential effect on IFN-γ and IL-12 induction was observed. In addition, one strain could extensively suppress proliferation induced by anti-CD3/anti-CD28 stimulation. Specific strains that were able to suppress the Th2 cytokine induction and induce Th1 cytokines might be beneficial for allergic patients.
    Effects found in vitro cannot directly be extrapolated to in vivo and therefore, in Chapter 9, we performed an in vivo screening including five Lactobacillus strains. Blood samples were collected before and after a 4-week intervention with probiotics from all 62 birch-pollen-allergic patients included. Four strains caused a decrease in birch-pollen-specific IgE and for one specific strain this coincided with significant decreases in IL-5 and IL-13 and an increase in IL-10 production by anti-CD3/anti-CD28 stimulated PBMC cultures and might therefore have the potential to alleviate seasonal allergy symptoms.
    The last chapter, Chapter 10, gives an overview of the most important results of this thesis and discusses the research limitations and future research perspectives. We hypothesize the role of protein aggregation in allergenicity and we elaborate on the importance of a proper stepwise approach to realize selection of a proper lactic acid strain for in vivo human testing.
    In conclusion, this thesis showed that processing effects can have profound and specific effects on the structure and the allergenicity of relevant allergens. However, to test putative effects on allergenicity, IgE-binding tests only are not sufficient and mediator release assays are important to include, particularly when testing aggregated proteins. These results might have consequences for the proper diagnosis of food allergy in daily practice. Finally, as effects of lactic acid bacteria are strain specific, a proper pre-selection of candidate strains is important to choose the most promising strains for clinical testing. In our in vivo screening, one strain, L. plantarum CBS125632, was found to be promising because of its desired immunomodulatory activity to test in a follow-up trial to reduce symptoms of birch-pollen allergy.

    Survival and vigour of ultra-dry seeds after ten years of hermetic storage
    Hong, T.D. ; Ellis, R.H. ; Astley, D. ; Pinnegar, A.E. ; Groot, S.P.C. ; Kraak, H.L. - \ 2005
    Seed Science and Technology 33 (2005)2. - ISSN 0251-0952 - p. 449 - 460.
    zaadkieming - groeikracht - uitdrogingstolerantie - daucus carota - aardnoten - koolzaad - allium cepa - opslag van zaden - seed germination - vigour - desiccation tolerance - daucus carota - groundnuts - rape - allium cepa - seed storage - moisture-content limit - logarithmic relation - theoretical basis - longevity - temperatures - groundnut - protocols - lettuce
    Seeds of carrot, groundnut, lettuce, oilseed rape and onion were stored hermetically in laminated aluminium foil packets in four environments (dry or ultra-dry moisture contents combined factorially with temperatures of 20 degrees C or -20 degrees C), replicated at several sites. After ten years' hermetic storage, seed moisture content, equilibrium relative humidity, viability (assessed by ability to germinate normally in standard germination tests) and vigour were determined. After a decade, the change in seed moisture content of samples stored at -20 degrees C was small or nil. Except for groundnut and lettuce (where loss in viability was about 8 and 3%, respectively), no loss in viability was detected after 10 years' hermetic storage at -20 degrees C. In all cases, there was no difference in seed survival between moisture contents at this temperature (P > 0.25). Comparison of seed vigour (root length and rate of germination) also confirmed that drying to moisture contents in equilibrium with 10-12% r.h. had no detrimental effect to longevity when stored at -20 degrees C: the only significant (P <0.05) differences detected were slightly greater root lengths for ultra-dry storage of four of the six seed lots. Seed moisture content had increased after a decade at 20 degrees C (generally to the level in equilibrium with ambient relative humidity). Hence, sub-zero temperature storage helped maintain the long-term integrity of the laminated aluminium foil packets, as well as that of the seeds within.
    Quantitative resistance to peanut bud necrosis tospovirus in groundnut
    Buiel, A.A.M. - \ 1996
    Agricultural University. Promotor(en): J.E. Parlevliet; D. Peters. - S.l. : Buiel - ISBN 9789054856023 - 113
    plantenveredeling - ziekteresistentie - plaagresistentie - Arachis hypogaea - aardnoten - planten - plantenziekten - plantenvirussen - tomatenbronsvlekkenvirus - plant breeding - disease resistance - pest resistance - Arachis hypogaea - groundnuts - plants - plant diseases - plant viruses - tomato spotted wilt virus

    Quantitative resistance to peanut bud necrosis virus (PBNV) is expressed as a reduced disease incidence (percentage of infected plants) in the groundnut crop. An increased plant density reduced this incidence, but the number of infected plants per unit area increased, maintaining high levels of PBNV.

    No significant inter-plot interference was observed. It appeared that the quantitative resistance, assessed in small plots of the plant breeder, is representative of the farmers' situation.

    The PBNV infection was higher in the center of the field as compared to the border zones of the field. This effect was probably caused by the dispersal pattern of the vector.

    Selection for resistance to the virus was most effective in environments with average or high levels of natural infection. However, selection in environments with low levels of infection yielded similar results when the data of several years were combined.

    At least three resistance factors were found in seven groundnut genotypes. Two different factors were present in the resistant ICGV genotypes, while another factor was present in groundnut cultivar TMV 2. The latter has a slight resistance compared to the most susceptible check, but it has been effective for several decades and can be considered durable.

    In addition, mature plant and tissue resistance caused a reduction in incidence and increased the incubation period. This effect was shown to occur in the field, and caused a slowing down and a termination of the epidemic in the course of the growing season.

    Virus resistance can be explained by an inhibition of virus multiplication and/or virus movement. These mechanisms result in a reduction of the disease incidence in resistant genotypes.

    Recent studies on peanut bud necrosis disease. Proc. Meeting ICRISAT.
    Buiel, A.A.M. ; Parlevliet, J.E. ; Lenné, J.M. - \ 1995
    Patancheru [etc.] : ICRISAT [etc.] - ISBN 9789290663188 - 76
    Arachis hypogaea - geleedpotigen - ziekteresistentie - aardnoten - insecten - plaagresistentie - plantenveredeling - plantenziekten - plantenplagen - plantenvirussen - planten - Thrips - Thysanoptera - tomatenbronsvlekkenvirus - vectoren - virussen - Thrips palmi - Arachis hypogaea - arthropods - disease resistance - groundnuts - insects - pest resistance - plant breeding - plant diseases - plant pests - plant viruses - plants - Thrips - Thysanoptera - tomato spotted wilt virus - vectors - viruses - Thrips palmi
    Onderzoek naar aflatoxine B1 in mengvoeders en grondstoffen : jaaroverzicht 1989
    Trijp, J.M.P. van; Mazijk, R.J. van; Roos, A.H. ; Tuinstra, L.G.M.Th. - \ 1990
    Wageningen : RIKILT (Rapport / RIKILT 90.16) - 14
    voer - veevoeder - maïs - aflatoxinen - aardnoten - besmetting - hplc - voedselanalyse - feeds - fodder - maize - aflatoxins - groundnuts - contamination - hplc - food analysis
    Het rapport geeft een overzicht van de resultaten , welke zijn verkregen bij het onderzoek van monsters rundveevoeder (n=287 ), grondnotenschroot (n=46) en een aantal diverse grondstoffen (n=30) naar het gehalte aan aflatoxine B1. De resultaten zijn verkregen met behulp van een methode gebaseerd op solid phase extractie als clean up, gevolgd door een HPLC-analyse waarbij een post-column derivatisering met broom plaatsvindt. Detectie van het derivaat gebeurt door middel van fluorescentie. Overschrijdingen van het maximum toelaatbaar gehalte voor aflatoxine B1 in rundveevoeders (0,010 mg/kg bij een vochtgehalte van 12%), werden met de officiële EG-methode vastgesteld in dertien monsters rundveevoeder. De mediaan in rundveevoeders (n=287) bedroeg 0,006 mg/kg en de range (0,001-0,050 mg/kg. In de loop van 1989 werd een dalende trend waargenomen in het gehalte aan aflatoxine B1 in rundveevoeders. In grondnotenschroot bedroeg de mediaanbesmetting 0,026 mg/kg aflatoxine B1 op produkt (range (0,005-0,40 mg/kg (n=46)). Deze mediaan is sterk verlaagd ten opzichte van 1988 (factor 5). De hoogste waarden werden gemeten in monsters afkomstig uit Soedan (mediaan 0,093 mg/kg ). Een overschrijding van de norm voor grondnoten (0,2 mg/kg) werd in drie monsters van Soedanese afkomst geconstateerd. Voor palmpitschilfers werd een mediaanwaarde berekend van <0,005 mg/kg (n=18). Het rapport heeft, voor wat betreft de grondstoffen, betrekking op de maanden januari t/m juli 1989. Na deze periode zijn de analyses in grondstoffen overgenomen door het laboratorium van het Comité van Graanhandelaren te Europoort-Rotterdam.
    Onderzoek naar aflatoxine B1 in mengvoeders en grondstoffen : jaaroverzicht 1988
    Roos, A.H. ; Mazijk, R.J. van; Rhijn, J.A. van; Trijp, J.M.P. van; Tuinstra, L.G.M.Th. - \ 1989
    Wageningen : RIKILT (Rapport / RIKILT 89.31) - 14
    voer - veevoeder - maïs - aflatoxinen - aardnoten - besmetting - voedselanalyse - feeds - fodder - maize - aflatoxins - groundnuts - contamination - food analysis
    Het rapport geeft een overzicht van de resultaten van het onderzoek naar aflatoxine Bl in rundveevoeders (n=238), grondnoten (n=200), varkensvoeder (n=8), legpluimveevoeder (n=3), mestpluimveevoeder (n=4), hondenvoer (n=1) en een monster maisgluten in 1988. Overschrijdingen van het maximum toelaatbare gehalte voor aflatoxine B1 in rundveevoeders (0,010 mg/kg bij een vochtgehalte van 12%) werden met de officiële EEG-methode aangetoond in 6 rundveevoeders, 2 mestpluimveevoeders, 1 legpluimveevoeder en 2 varkensvoeders. De mediaan bedroeg 0,004 en de range <0,002 - 0,080 mg/kg aflatoxine B1. Beide zijn vergelijkbaar met die van de voorgaande verslagperiode (1987). In grondnotenschroot bedroeg de mediaanbesmetting 0,12 mg/kg aflatoxine B1 op produkt (range
    Plant resources of South-East Asia: I. Pulses.
    Maesen, L.J.G. van der; Sadikin Somaatmadja, - \ 1989
    Wageningen : Pudoc - ISBN 9789022009840 - 105
    peulvruchten - Arachis hypogaea - aardnoten - Glycine max - sojabonen - Fabaceae - ecologie - gewassen - landbouw - fenologie - acclimatisatie - wilde planten - Zuidoost-Azië - economische botanie - grain legumes - Arachis hypogaea - groundnuts - Glycine max - soyabeans - Fabaceae - ecology - crops - agriculture - phenology - acclimatization - wild plants - South East Asia - economic botany
    Mixed cropping of groundnuts and maize in East Java
    Hoof, W.C.H. van - \ 1987
    Agricultural University. Promotor(en): M. Flach; G.H. de Bruijn. - Renkum : Van Hoof - 156
    Arachis hypogaea - aardnoten - tussenteelt - tussenplanting - Java - maïs - gemengde teelt - meervoudige teelt - Zea mays - Arachis hypogaea - groundnuts - intercropping - interplanting - Java - maize - mixed cropping - multiple cropping - Zea mays
    Mixed cropping of groundnuts and maize in East Java was studied by means of a survey of farming practice and by field experiments. The influence of different sowing times and plant density of maize on the development and yield of groundnuts and maize were the main topics in this thesis. Plant arrangement, light use efficiency, and economic aspects were also investigated.

    The normal farming practice in East Java for mixed cropping of groundnuts and maize was to sow the crops simultaneously at the end of the rainy season. The average plant densities used were: 190,000 plants per hectare (167,000-214,000) for groundnuts (95% of the plant density of the sole crop) and 40,000 plants per hectare (31,000-50,000) for maize (53% of the sole crop density). Average yields were 1140 kg/ha of groundnuts (80% of the sole crop yield) and 900 kg/ha of maize (43% of the sole maize yield). The average LER of the mixed crops was 1.23, which means a 23% higher productivity than the sole crops of groundnuts and maize.

    In the field experiments, the density of groundnuts was 160,000 plants per hectare, and the density of sole maize was 125,000 plants per hectare (80 x 20 cm, 2 plants per hill). In each of the experiments 3 to 7, the plant density of maize in the mixed crops was varied. in experiments 1 and 2 , however, the maize density was 83,000 plants per hectare (80 x 30 cm, 2 plants per hill), both in sole and mixed crops.

    In experiments 1 and 2, the sowing date of maize (sown at 100% density) in the mixed crop was varied. Later sown maize plants were less developed and gave lower yields than simultaneouslysown maize. Groundnuts in the mixed crops showed a better development and yield when maize was sown later, but not as good as sole groundnuts.

    In experiment 2, the sole crop yields were much higher, and the response to a delay in sowing time of the maize was much stronger than in experiment 1. The higher yield was due to better nutrient availability and freedom from water stress in the beginning of the growing period.
    The most equal yield distribution between groundnuts and maize in mixed crops was reached when maize was sown about 10 days later than groundnuts.

    In experiments 3 to 5 the plant density of maize in the mixed crop was varied, with maize sown 10 days later than the groundnuts. At higher plant densities, the development and yield of the groundnut crop and of the individual maize plants was less than at lower maize densities.
    When maize was sown 10 days later than the groundnuts (100% density), maximum maize yields in mixed crops were obtained at maize densities between 80% and 150% of the sole crop density, but the highest LER values for the mixed crop were reached with slightly lower maize densities between 70% and 100%. This was higher than the usual maize density in farmers' fields of about 50% in mixed crops with simultaneously- sown groundnuts and maize.

    The effect of the arrangement of maize plants in mixed crops was small compared with the effect of plant density. only at extremely high maize densities, plant arrangement had a substantial effect (experiment 5).

    The interaction of sowing time effect and plant density effect, studied in experiments 6 and 7, showed that the longer the delay in sowing time of the maize, the higher the plant density of maize had to be, to reach maximum LER values for the mixed crop.

    The higher productivity of the mixed crops compared to sole maize can be explained by the higher percentage of intercepted light (67% against 43%), and compared to sole groundnuts by the better utilization of the intercepted light (1.0% against 0.6%).

    The revenues from the mixed crops were much higher than from sole maize and only slightly lower than from sole groundnuts. Delaying the sowing of maize in the mixed crop resulted in higher revenues. A change in the price ratio between groundnuts and maize from 4:1 to 2:1 would result in higher revenues for the mixed crop than for each of the sole crops (chapter g).

    In mixed crops, a higher share of the work was done by women (57%) than in sole groundnuts (53%) and sole maize (27%). A 10-day delay in the sowing time of maize resulted in a better spreading of the labour demand over the growing period.

    Sowing maize 10 days later than groundnuts at a density of 75% of the normal sole crop density can be an improvement of the normal farming practice to sow maize at 50% density simultaneously with the groundnuts. In mixed crops with 10 days delay in sowing time of maize and 70% to 100% maize density, the marketable yield was 1070 kg/ha of groundnuts and 1840 kg/ha of maize, averaged over the 7 field experiments. The groundnut yield in the experiments was similar to that in the farmers' practice with simultaneous sowing and 50% maize density, and the maize yield was twice as high.

    In experiment 2, with its high fertility level and its adequate water supply, the LAI of sole maize was higher than 4, and sole maize yield was over 4 tons per hectare. In mixed crops with LAI values of maize higher than 4, the shading of the groundnut crop is too heavy, and no yield advantage can be expected from the mixed crop compared to the sole maize crop. Relay cropping can be a proper practice of intensive crop production when high yield levels are obtained with sole crops. Mixed crops are more secure than sole crops in situations of marginal farming, low soil fertility, unreliable water supply and low input level. Improvements in mixed cropping techniques are a cheap way to increase the food production in East Java.

    Etudes epidemiologiques sur la rouille de l'arachide en Cote d'Ivoire
    Savary, S. - \ 1986
    Landbouwhogeschool Wageningen. Promotor(en): J.C. Zadoks. - S.l. : Savary - 154
    Arachis hypogaea - Ivoorkust - distributie - epidemiologie - aardnoten - plantenziekten - plantenziekteverwekkende schimmels - plantenplagen - Puccinia - pucciniales - Arachis hypogaea - Cote d'Ivoire - distribution - epidemiology - groundnuts - plant diseases - plant pathogenic fungi - plant pests - Puccinia - pucciniales
    The study of the pathosystem: Arachis hypogaea - Puccinia arachidis was undertaken at different scales: the leaf, the plant, the field, the region, which allow to consider the monocyclic (leaf and plant) and polycyclic (field and region) processes. Several epidemiological processes were investigated as well as their succession during the epidemic build-up. At the region scale, some other important diseases of groundnut were considered, leading to a study of the multiple pathosystem: Arachis hypogaea - Puccinia arachidis - Cercosporidium personatum - Cercospora arachidicola .

    A preliminary analysis of the data from a survey in the various regions of Ivory Coast where groundnut is cultivated showed that rust was omnipresent. A correspondence analysis allowed to unravel the large variations of weather, cropping, and pathological situations, and to produce a general picture of the development of an average small farmer's field in time. Every year, general epidemics of groundnut rust developped in the Northern and Central regions. These were, to a large extent, ascribed to the endemicity of groundnut rust in the Southern region, which is a permanent source of inoculum.

    Several inoculation methods of detached leaf lets with groundnut rust were compared under laboratory conditions. The infection efficiency is highest with dry urediniospores at low inoculum level and lowest with suspended urediniospores at high inoculum level.

    The effects of temperature and inoculum level on the monocyclic process were investigated. Temperatures of about 27°C appeared to be optimal for rust development: infection efficiency, infectious period, and sporulation intensity were then highest, while latency period was lowest. Temperature effects on groundnut rust were compared to those on other host-rust systems, The results suggested that temperature variation has a strong effect on the development of groundnut rust epidemics.

    Leaf age and plant development stage were also considered as influencing factors on rust development on a susceptible groundnut cultivar. The results, a reduction of infection efficiency with increasing leaf age and an increase of latency period with increasing leaf age and development stage, indicated that different leaf layers in the canopy could differ in their epidemiological parameters.

    The monocyclic studies on detached leaflets were accompanied by experiments on potted plants, which yielded the same general conclusions on the effects of some factors. Differences in values of variables were found (for the infection efficiency and latency period), which were discussed.

    Aerial dispersal of dry spores was studied In artificial groundnut rust foci. A significant linear regression was found of the logit of the relative spore content of the air on the logit of rust intensity expressed as the number of lesions m -2of field. A major explanatory variable of the diurnal rhythmicity of the aerial spore density was relative humidity, and a secondary one was wind velocity. The hypothesis was put forward that these variables affect rhythmicity over the whole range of variation of the aerial spore density as measured at different rust intensities.

    Rain-induced dispersal of groundnut rust urediniospores was studied in artificially infected plots on which variable rainfall amounts and intensities were applied, using a rainfall simulator. Several trapping methods allowed to compare dry, splash and drip dispersal. The spore liberation mechanisms and the resulting spore flows were considered at the canopy and at the individual lesion scales. The results indicated that dry dispersal was predominant. The observed increase of the flow of spores dripping from the canopy to the soil with increasing rainfall amounts suggested that light rain showers were favourable, whereas heavy showers were unfavourable to rust dispersal.

    Disease dispersal from artificial foci was studied with respect of variation in canopy structure with increasing plot age, The primary gradients of rust which developped in older plots had higher mean values and slopes. The relative height of infection was also higher in older plots. These age-dependant variations were attributed to variations in dispersibility and accessibility. The results also indicated a strong ability of groundnut rust to disperse at mesoscale

    The analysis of survey data was resumed, focusing on groundnut rust epidemiology. This disease exhibited marked weather (temperature and rainfall) requirements, strong dispersal abilities at mesoscale and macroscale, and intensified quickly in well-tended crops. These characteristics differed much from those of leaf-spot diseases, especially C. arachidicola leaf-spot. The conclusions of this analysis were in agreement with previous results from monocyclic experiments, The hypothesis is forwarded that intensification in groundnut cultivation would enhance rust epidemics build-up,

    The results of this thesis on groundnut rust epidemiology may be assembled to build a pictorial, qualitative model or a quantitative summary model for dynamic simulation. Both approaches allow to identify gaps in the available information and to evaluate the results of these studies.

    Het gehalte aan aflatoxine B1 in rundveevoeders en grondnotenschroot in 1982
    Roos, A.H. ; Neer, Th.C.H. van; Tuinstra, L.G.M.Th. ; Haasnoot, W. - \ 1983
    Wageningen : RIKILT (Verslag / RIKILT 83.33) - 4
    rundveevoeding - veevoeder - aflatoxinen - mycotoxinen - aardnoten - schroot - analytische methoden - cattle feeding - fodder - aflatoxins - mycotoxins - groundnuts - oilmeals - analytical methods
    Evenals in 1980 en 1981 zijn de resultaten van het aflatoxine B1 onderzoek getabelleerd om een inzicht te verkrijgen in de mate van besmetting van rundveevoeders en grondnotenprodukten met aflatoxine B1.
    cultuurmaatregelenproef bij aardnoot (Arachis hypogaea L. cv. Matjan) : het effect van al dan niet aanaarden bij chemische of mechanische onkruidbestrijding; rassenproef met creampea (Vigna unguiculata (L.) Walp.); Bepaling van de HCN - produktie door de verdikte wortels van 33 cassaveklonen
    Muileboom - Muffels, T. - \ 1975
    Wageningen : Landbouwhogeschool (Celos rapporten no. 105) - 48
    Arachis hypogaea - plantkunde - cassave - vignabonen - aardnoten - Manihot esculenta - plantenziekten - afwijkingen, planten - plantenziektekunde - plantenplagen - gewasbescherming - Vigna - suriname - Arachis hypogaea - botany - cassava - cowpeas - groundnuts - Manihot esculenta - plant diseases - plant disorders - plant pathology - plant pests - plant protection - Vigna - suriname
    Aflatoxine B1 in aardnoten
    Anonymous, - \ 1975
    Wageningen : [s.n.] (Literatuurlijst / Centrum voor landbouwpublikaties en landbouwdocumentatie no. 3730)
    Arachis hypogaea - bibliografieën - aflatoxinen - aardnoten - Arachis hypogaea - bibliographies - aflatoxins - groundnuts
    plantverbandproef met aardnoot; bekalkingsproef met aardnoot; Onderzoek aan aardnoot te Coebiti in de periode december 1973-april 1974; Vergelijking van een aantal cowpea-cultivars van het blackeye type
    Muijlwijk, T. van - \ 1974
    Wageningen : Landbouwhogeschool (Celos rapporten no. 95)
    suriname - landbouwkundig onderzoek - onderzoeksprojecten - aardnoten - plaatsen op afstand - bekalking - vignabonen - plantenontwikkeling - suriname - agricultural research - research projects - groundnuts - spacing - liming - cowpeas - plant development
    vergelijkende opbrengstproef met aardnoten; vergelijkende opbrengstproef met katjang idjo; vergelijkende opbrengstproef met soja; vergelijkend groei-analytisch onderzoek van de rijstcultivar Acorni bij verschillende plantdichtheden
    Slobbe, W.G. van - \ 1973
    Wageningen : Landbouwhogeschool (Celos rapporten no. 86)
    suriname - landbouwkundig onderzoek - onderzoeksprojecten - opbrengsten - aardnoten - vigna radiata - glycine max - cultivars - rijst - plantenontwikkeling - suriname - agricultural research - research projects - yields - groundnuts - vigna radiata - glycine max - cultivars - rice - plant development
    Seed morphology and early development of yhe groundnut (Arachis hypogaea L.)
    Staritsky, G. - \ 1973
    Wageningen : Landbouwhogeschool (Celos bulletins no. 23) - 16
    zaadmorfologie - morfogenese - plantenontwikkeling - aardnoten - arachis hypogaea - landbouwkundig onderzoek - suriname - seed morphology - morphogenesis - plant development - groundnuts - arachis hypogaea - agricultural research - suriname
    The morphogenesis of groundnut plants from an age of 0 to 21 days is described. The opinion that flower primordia are present in groundnut seeds is not confirmed. Further observations prove that the early development of the groundnut is less fixed than former conceptions about the structure of the seed suggest.
    Verdampingsmetingen in Suriname : deel 1: beschrijving van het onderwerp en de constructie van een hydraulisch weegbare lysimeter; Schatten van het bladschijfoppervlak uit lengte en grootste breedte bij twee rijstcultivars; vergelijkende opbrengsproef met aardnoten; vergelijkende opbrengstproef met cowpea
    Kieft, H. ; Wienk, J.F. ; Erdman, J.W. - \ 1972
    Paramaribo : Centrum voor Landbouwkundig Onderzoek in Suriname (Celos rapporten no. 64)
    landbouwkundig onderzoek - onderzoeksprojecten - suriname - evaporatie - verdampingsmeters - lysimeters - cultivars - bladoppervlakte - schijfcultivators - gewasopbrengst - opbrengsten - aardnoten - vignabonen - agricultural research - research projects - suriname - evaporation - evaporimeters - lysimeters - cultivars - leaf area - disc cultivators - crop yield - yields - groundnuts - cowpeas
    Dit bestand bevat vier onderzoeksverslagen uitgevoerd door het centrum landbouwkundig onderzoek Suriname. De onderwerpen van de onderzoeksverslagen zijn verdampingsmetingen, rijstcultivars en twee opbrengstproeven (een voor aardnoten en een voor cowpea).
    Produktie en verdeling van droge stof bij Arachis hypogaea L. CV. matjan onder invloed van het plantverband
    Wienk, J.F. - \ 1970
    Paramaribo : [s.n.] (Celos rapporten no. 32) - 24
    Arachis hypogaea - cultuurmethoden - aardnoten - Suriname - Arachis hypogaea - cultural methods - groundnuts - Suriname
    invloed van de Cotylen op groei en bloei van Arachis Hypogaea L. CV. Matjan; Potgrootte en bodemvruchtbaarheid in verband met groei en ontwikkeling van Phaseolus Aureus Roxb; invloed van de cotylen op de jeugdontwikkeling van Arachis Hypogaea L. CV. Matjan
    Verhaar, H.M. - \ 1968
    Parimaribo : [s.n.] (CELOS rapporten no. 14) - 14
    Arachis hypogaea - aardnoten - landbouw - Vigna mungo - urd (vigna mungo) - plantkunde - laboratoria - Suriname - voorzieningen - Arachis hypogaea - groundnuts - agriculture - Vigna mungo - black gram - botany - laboratories - Suriname - facilities
    Mechanisatie van de aardnotenteelt en - verwerking
    Anonymous, - \ 1967
    Wageningen : [s.n.] (Literatuurlijst / Centrum voor landbouwpublikaties en landbouwdocumentatie no. 2866)
    Arachis hypogaea - bibliografieën - boerderij uitrusting - landbouwwerktuigen - aardnoten - plantaardige producten - behandeling - Arachis hypogaea - bibliographies - farm equipment - farm machinery - groundnuts - plant products - treatment
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