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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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    Seed quality in informal seed systems
    Biemond, P.C. - \ 2013
    Wageningen University. Promotor(en): Paul Struik, co-promotor(en): Tjeerd-Jan Stomph. - S.l. : s.n. - ISBN 9789461736420 - 120
    zaadkwaliteit - zaadfysiologie - vigna unguiculata - vignabonen - zaadkieming - zaadpathologie - mycotoxinen - zea mays - nigeria - seed quality - seed physiology - vigna unguiculata - cowpeas - seed germination - seed pathology - mycotoxins - zea mays - nigeria

    Keywords: informal seed systems, seed recycling, seed quality, germination, seed pathology, seed health, seed-borne diseases, mycotoxigenic fungi, Fusarium verticillioides, mycotoxins, Vigna unguiculata, Zea mays, Nigeria.

    Seed is a crucial input for agricultural production. Approximately 80% of the smallholder farmers in Africa depend for their seed on the informal seed system, consisting of farmers involved in selection, production and dissemination of seed. The lack of overhead, distribution and seed testing costs enables seed-producing farmers to offer seed for low prices, but seed quality is not always good. Seed-producing farmers multiply their seed on-farm without frequent seed renewal, referred to as seed recycling, which may lead to low seed quality. This research analysed the effect of seed recycling on physiological quality and seed health of cowpea and maize, and compared seed quality of the formal and informal seed system.

    We tested the physical and physiological quality of cowpea seeds produced by the formal and informal seed system. Five out of six foundation seed samples, 79 out of 81 samples of farmers’ seed, and six out of six seed company samples failed to meet standards for foundation and certified seeds of the National Agriculture Seed Council (NASC), the seed industry regulatory agency in Nigeria. No evidence was found for a negative effect of seed recycling on physiological quality of cowpea seeds. We analysed 45,500 cowpea seeds for seed-borne bacteria and fungi to compare the performance of formal and informal seed systems. All samples were heavily infected with seed-borne pathogens, including Fusarium oxysporum (69% of the samples) and Macrophomina phaseolina (76%). No evidence was found that seed recycling in the informal seed system did lead to increased levels of seed-borne pathogens. We also analysed seed quality of farmer-produced maize seed to compare it with the formal seed system. The seed company samples had significantly higher germination (99.3%) than farmer-produced seed (97.7%), but not a single sample passed the requirements for certified seed of the NASC. Twelve seed-borne pathogens were identified including Bipolaris maydis (found in 45% of the farmer-produced samples), Botryodiplodia theobromae (97%) and Fusarium verticillioides (100%). Seed recycling had no negative effect on the physiological quality or seed health of maize seed. We analysed formal and informal seed systems to assess the opportunities to prevent mycotoxigenic fungi infection in maize seeds. A range of control methods to avoid fungal infection and mycotoxin production is discussed in relation to three criteria for sustainable implementation in developing countries. An integrated approach is recommended, with special attention towards the local seed system. As an overall conclusion of the work it can be stated that the informal seed system did not underperform compared to the formal seed system for cowpea, but did underperform in relation to seed company samples of maize. There was no evidence that seed recycling reduces seed quality of cowpea and maize seed samples, so frequent seed renewal will not improve seed quality of the informal seed system. We recommend a new quality assurance system for the informal seed system based on seed quality testing by farmers themselves, without interference by government or external laboratories. Farmers publish their seed testing results on the bag, while buyers can retest the seed to verify the quality. Further research is required to develop and implement this system in different countries, agro-ecologies and crops, and to develop methods that enable farmers to test seed health quality themselves.

    Biology and ecology of Apanteles taragamae, a larval parasitoid of the cowpea pod borer Maruca vitrata
    Dannon, A.E. - \ 2011
    Wageningen University. Promotor(en): Marcel Dicke; Arnold van Huis, co-promotor(en): M. Tamò. - [S.l.] : S.n. - ISBN 9789085859482 - 188
    vigna unguiculata - vignabonen - insectenplagen - maruca vitrata - boorders (insecten) - apanteles - sluipwespen - biologie - levensgeschiedenis - biologische bestrijding - vigna unguiculata - cowpeas - insect pests - maruca vitrata - boring insects - apanteles - parasitoid wasps - biology - life history - biological control

    Maruca vitrata Fabricius is a key insect pest of cowpea in West Africa. Larvae of this moth can cause up to 80% of yield losses. The first classical biological control programme against M. vitrata started in 2005 with the introduction of Apanteles taragamae Viereck from Taiwan into Benin by the International Institute of Tropical Agriculture (IITA), Benin station.Thorough knowledge on the bioecology of A. taragamae is a prerequisite for implementing such programme. The work described in the present thesis evaluated the biological potential of this larval parasitoid to fill to the gap of information on its biology and ecology. Special emphasis was put on the main factors that determine the effectiveness/suitablility of biological control candidates, such as reproductive capacity, functional response, climatic adaptability, host foraging capacity, and non-target effects. The results revealed that two-day-old larvae were the most suitable host age, giving the highest percentage parasitism, lifetime fecundity and proportion of females. Larvae older than three days were not successfully parasitized. The percentage parasitism of two-day-old larvae was positively correlated with host density, indicating a good functional response of A. taragamae. Between 20 and 30 °C, the curve that described the relationship between the intrinsic rate of natural increase and the temperature for A. taragamae was above that of M. vitrata, suggesting that the parasitoid can faster build up its population than its host. The parasitoid showed its ability to use volatiles produced by cowpea flowers and host caterpillars when foraging. A host plant odour experience enhanced the capacity of the parasitoid to find uninfested flowers. The growth of non-parasitized or A. taragamae-parasitized larvae was slower and with reduced proportion of female wasps on some host plants compared to those reared on artificial diet. With regard to the non-target effects, the physiological host range and competitive ability of A. taragamae were assessed. None of the following lepidopteran species, Eldana saccharinaWalker, Chilo partellus (Swinhoe), Mussidia nigrivenella Ragonot, Cryptophlebia leucotreta (Meyrick), Sylepta derogata FabriciusandCorcyra cephalonica Stainto,was successfully parasitized by A. taragamae, suggesting its specificity for M. vitrata in Benin. In no-choice competition with the egg-larval parasitoid Phanerotoma leucobasis, A. taragamae outcompeted the latter. All the above attributes suggest that A. taragamae should be a suitable biocontrol agent against M. vitrata. A cage release strategy involved the host plant Sesbania cannabina, which was artificially infested with M. vitrata, and inoculated with adults of A. taragamae. The parasitoid was released in seven selected locations in Benin but the first recovery studies did not yet yield any information on its establishment after the first generation.

    Gewassaldo van Kouseband en Sopropo in drie Surinaamse tuinbouwgebieden : verslag van een survey in Commewijne, Saramacca en Wanica
    Putter, H. de; Wongsonadi, H. - \ 2010
    Lelystad : Praktijk Plant & Omgeving. Akkerbouw, Groene ruimte en Vollegrondsgroenten - 26
    tuinbouw - vigna unguiculata - momordica charantia - kwekers - interviews - suriname - horticulture - vigna unguiculata - momordica charantia - growers - interviews - suriname
    In september 2010 is een survey uitgevoerd in de tuinbouwgebieden Commewijne, Saramacca en Wanica. In Saramacca en Wanica werden elk 5 telers van sopropo en kouseband geïnterviewd en in Commewijne werden 5 kouseband en 5 sopropo telers geïnterviewd. De telers werden met behulp van een vragenformulier bevraagd naar de kosten en opbrengsten van een kouseband of sopropo teelt. Ook werd gevraagd naar de benodigde arbeid voor de diverse teelthandelingen. Uit dit onderzoek kwam naar voren dat over het algemeen er weinig teeltregistratie door de telers zelf wordt gedaan. De meeste gegevens zijn afkomstig op basis van herinnering. Voor het opstellen van de gewassaldo’s moesten aannames gemaakt worden op het gebied van teeltduur, oogstperiode en gewasbeschermingsmiddel gebruik. Op basis van de opgestelde gewassaldo’s blijken tussen de drie onderzochte regio’s verschillen aanwezig te zijn in bemestingsstrategieën, opbrengsten en benodigde arbeid.
    Genetic analysis of abiotic and biotic resistance in cowpea [Vigna unguiculata (L.) Walp.]
    Agbicodo, A.C.M.E. - \ 2009
    Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Gerard van der Linden; C.A. Fatokun. - [S.l. : S.n. - ISBN 9789085854777 - 168
    vigna unguiculata - vignabonen - genetische analyse - droogteresistentie - plantenziekteverwekkende bacteriën - xanthomonas axonopodis pv. vignicola - ziekteresistentie - plantenveredeling - resistentieveredeling - vigna unguiculata - cowpeas - genetic analysis - drought resistance - plant pathogenic bacteria - xanthomonas axonopodis pv. vignicola - disease resistance - plant breeding - resistance breeding

    Cowpea [Vigna unguiculata (L.) Walp.] is a most versatile African crop, it feeds people, their livestock and because of its ability in nitrogen-fixation, it improves soil fertility, and consequently helps to increase the yields of cereal crops when grown in rotation and contributes to the sustainability of cropping systems. Because of its ability to tolerate some level of drought stress, cowpea is a crop of choice where > 10 million hectares are cultivated to cowpea in the semiarid Savanna and Sahelian zones of West and Central Africa. However due to the infrequent drought stress throughout cropping seasons over the last 3 decades, the crop suffers important yield reduction. Moreover, cowpea plants under water stress condition are more vulnerable to diseases, parasites and insect pests attacks. In this thesis we carried out genetic analyses of seedling and terminal drought tolerance and cowpea bacterial blight (CoBB) resistance. Two cowpea genotypes with contrasting reactions to drought and CoBB stresses, Danila (resistant) and TVu7778 (susceptible) were used to develop recombinant inbred lines (RILs) mapping population. The RILs and parents were phenotyped for CoBB resistance and for physiological drought tolerance traits and productivity traits under different water regimes in multiple environments at seedling and adult plant stages. A genetic linkage map of 282 single nucleotide polymorphism (SNP) loci covering a map distance of 633 cM distributed over 11 linkage groups (LG) from the same RILs was used for quantitative traits loci (QTL) analyses. Moisture stress significantly affected RILs performances with number of pods per plant as the yield component most adversely affected by water stress. Correlation and path analyses revealed that grain yield components (mainly number of pods per plant) and plant biomass had the largest direct effects on grain yield under moisture stress and irrigation. Stem greenness was an excellent predictor of seedling survival to drought (r2 = 0.91). Two QTLs were identified for each of the three traits scored under greenhouse, drought-induced trifoliate senescence (DTS), stem greenness (Stg) and survival (Sur) on LG3 and LG7. For all traits measured under field trials, a total of 42 QTLs were detected, 4 for stomatal conductance (Gs), 6 for delayed leaf senescence (DLS), 5 for flowering time and 16 for grain yield components (pod number/plant, seed number/pod, seed weight), 6 for grain yield and 5 for fodder yield. Three QTLs were detected for CoBB resistance, with two major ones (named CoBB-1 and CoBB-2 confirmed over two experiments) on LG3 and LG5 and one minor QTL (CoBB-3 only for experiment 1) on LG9. Although number of QTLs detected seems to be important, association between QTLs of different traits sharing a common genomic region was observed on LG3, LG5, LG7 and LG8 where QTLs for Gs, DLS, and flowering time co-localized with QTLs for yield parameters, DLS and DTS shared common chromosomal regions with CoBB resistance, on LG3 and LG5. These results suggest that common genes might mediate CoBB resistance and DLS. Two QTLs detected for DLS in the field, co-localized with QTLs under greenhouse for seedling drought tolerance traits DTS, Stg and Sur on LG7. This indicates the presence of potential loci controlling senescence in this genomic region. Moreover, this genomic region represents a syntenic genomic region between cowpea, soybean and Medicago. Our findings provide evidence for QTLs mediating seedling and terminal drought tolerance and CoBB resistance in cowpea. QTL and phenotypic analysis revealed that it should be possible to pyramid CoBB resistance with seedling and terminal drought tolerance. The fact that the genetic map of Danila x TVu7778 is integrated in a consensus map of cowpea of 6 RIL populations will permit comparative genomic studies which will enhance the discovery of functional markers for MAS of seedling and terminal drought tolerance and CoBB resistance in cowpea.

    Eindverslag Surituin deelproject: terugdringen van residu normen overschrijdingen in Surinaamse export groenten
    Putter, H. de; Sauers-Muller, A. van - \ 2008
    [S.l.] : S.n. - 37
    tuinbouw - groenteteelt - vigna unguiculata - voederpeulvruchten - insecticidenresiduen - bladmineerders - bestrijdingsmethoden - testen - controles (experimenteel) - projecten - horticulture - vegetable growing - vigna unguiculata - fodder legumes - insecticide residues - leaf miners - control methods - testing - controls (experimental) - projects
    Het project heeft er toe geleid dat de sector bewust is geworden van de residu problematiek. Voor kouseband zijn diverse alternatieve middelen gevonden die telers kunnen inzetten tegen bladmineerders. Deze middelen zijn echter slechts summier getoetst en verder testen dienen uitgevoerd te worden. Het project heeft ook bijgedragen aan een verbeterde communicatie tussen de VWA en LVV. Ook heeft het project een bijdrage geleverd aan het opzetten van een nationaal controle systeem. De resultaten hebben duidelijk de urgentie van een dergelijk systeem aangetoond
    De bladmineerder in kouseband : een literatuurstudie naar de levenswijze en praktische handreikingen voor de bestrijding van Liriomyza spp. bladmineerders
    Putter, H. de; Sauers-Muller, A. van - \ 2008
    [S.l.] : S.n. - 70
    tuinbouw - vigna unguiculata - voederpeulvruchten - groenteteelt - bladmineerders - insectenplagen - bestrijdingsmethoden - parasieten van plaaginsecten - natuurlijke vijanden - biologische bestrijding - voedergewassen - horticulture - vigna unguiculata - fodder legumes - vegetable growing - leaf miners - insect pests - control methods - parasites of insect pests - natural enemies - biological control - fodder crops
    In dit verslag wordt het probleem van bladmineerders in kouseband en diverse bestrijdingsmethoden van Liriomyza spp. bladmineerders beschreven. Het effect van diverse bestrijdingsmethoden van bladmineerders en het effect ervan op de aanwezigheid van natuurlijke parasieten wordt weergegeven. Tot slot wordt besproken in hoeverre op basis van de beschikbare gegevens er mogelijkheden zijn voor een geïntegreerde of biologische bestrijding in kouseband
    Ecology and management of charcoal rot (Macrophomina phaseolina) on cowpea in the Sahel
    Ndiaye, M. - \ 2007
    Wageningen University. Promotor(en): Ariena van Bruggen, co-promotor(en): Aad Termorshuizen. - [S.l.] : S.n. - ISBN 9789085046646 - 114
    macrophomina phaseolina - vigna unguiculata - vignabonen - plantenziekten - plantenziekteverwekkende schimmels - geïntegreerde plagenbestrijding - teeltsystemen - compost - biologische bestrijding - sahel - niger - macrophomina phaseolina - vigna unguiculata - cowpeas - plant diseases - plant pathogenic fungi - integrated pest management - cropping systems - composts - biological control - sahel - niger
    Keywords: Senegal/Niger/rotation/millet/isolate characterization/fonio/compost amendment / bioagent/ Clonostachysrosea /solarization

    Cowpea ( Vignaunguiculata Walp.) is the most important pulse crop in theSahelwith nearly 12.5 million hectares per year and is a valuable source of protein for human and animal nutrition. The most limiting factors for crop growth in the Sahelian zone of West Africa are water and nutrient stress. The average cowpea yields in farmers' fields are low (0.2-0.5 ton/ha) and charcoal rot causes on average a yield loss of 10%, which is equivalent to 30.000 tons cowpea - an estimated value of $146 million for Niger and Senegal alone.Disease resistant or tolerant cultivars of cowpea against M . phaseolina are the most efficient control measures but such cultivars are not yet available. Solarization, addition of organic matter, maintenance of high soil moisture, fumigation and use of biocontrol agents have shown to be potential methods for control of soilborne pathogens.The objectives of the thesis is: 1)to characterize cowpea isolates of Macrophomina phaseolina prevalent in the different cowpea cropping systems in Niger and Senegal with respect to culture characteristics and host range; 2) to determine effects of rotation of cowpea with fonio and millet on M. phaseolina disease of cowpea, and production and survival of microsclerotia in soil; 3) to study the effects of compost and a biocontrol agent on M. phaseolina and charcoal rot on cowpea; 4) to study the effects of solarization alone or in combination with organic residues on M. phaseolina and charcoal rot on cowpea.

    Macrophominaphaseolina causes heavy yield loss to cowpea ( Vignaunguiculata ) grown in different cropping systems in the Sahel region ofAfrica. It was not known if cropping systems could influence physiological, genetic and pathogenic characteristics of M. phaseolina isolates. This study therefore aimed to analyze the population structure of M . phaseolina associated with three cropping systems in theSahel. Isolates were collected from soil and infected tissues of different cropping systems in Senegal and Niger and their growth potential at different temperatures, their morphology on PDA medium, their virulence on three cowpea cultivars and sequence analysis of the ITS (internal transcribed spacer) region of the nuclear ribosomal DNA gene studied.Isolates of M. phaseolina differed to a limited extent in temperature optimum, genetic make-up, and pathogenicity to cereal crops. The grouping according to physiological and genetic traits did not coincide with that based on pathogenicity. However, for the first time, we showed some specialization in pathogenicity to cereal crops except fonio ( Digitaria exilis )) for isolates obtained from fields grown to millet next to cowpea.

    Field observations and invitro studies indicated that fonio is a non-host to M. phaseolina , and millet a poor host, respectively. The influence of continuous cropping of these crops on soil inoculum density of M.phaseolinawas studied under field conditions. The data showed thatfonio was not infected by M. phaseolina , while the root systems of millet had low densities of microsclerotia. Cowpea yielded significantly more hay and pods after 3 years of fonio than after 3 years of millet. We conclude that rotation of cowpea with a gramineous crop may lead to a relatively fast decline of inoculum density. In the case of a high inoculum density, fonio can be grown for three years to reduce M . phaseolina densities in soil.

    A field experiment was conducted on the effect of compost on soil inoculum and symptom severity of charcoal rot. The experiment was carried out in naturally infested farmers' fields. The effect of 3 or 6 tons of compost and of 6 tons of compost supplemented with 50 kg NPK fertilizer ha -1 , applied in planting holes, on charcoal rot was assessed for three consecutive years. Besides, the combined effects of 3 tons of compost ha -1 and the biocontrol agent Clonostachysrosea (10 8 CFU's per g compost) on charcoal rot development and cowpea production were investigated. Our results indicated that in Sahelian sandy soil good control and substantial increase of cowpea yield can be achieved by soil amendment with 6 tons of compost ha -1 . An even greater yield increase is achieved by soil amendment with 6 tons of compost and 50 kg NPK ha -1 or 3 tons ha -1 of compost augmented by C.rosea .

    The combined effects of soil solarization and amendment with millet residues and paunch contents on the survival of M . phaseolina and development of charcoal rot of cowpea were assessed in a naturally infested soil.In amended plots, solarization increased the soil temperature to 50°C for at least 4 h day -1 during June, leading to a significant reduction of soil inoculum of M . phaseolina by 44%. Paunch amendment (3 tons ha -1 ) caused 66% reduction of initial inoculum in the solar-heated plots while millet amendment did not enhance microsclerotia reduction in solarized plots. These observations demonstrated that under conditions where solarization alone does not provide sufficient control, the combination with organic amendments improves yields and reduces infection by M . phaseolina . High-N containing amendments may be most effective, such as the paunch used in this study. Solarization as well as application and incorporation of millet residues or paunch content in moistened soil can double cowpea production in poor, naturally infested soil of the Sahelian zone and contribute to the management of paunch waste from slaughter houses in big cities.

    In conclusion the study indicated that M . phaseolinaisolates from different cropping systems in theSahelvary with respect to virulence and ability to cause infection on crop species and cultivars.For the first time we found isolates of C . rosea in theSahelthat are efficient at controlling M . phaseolina . In addition we showed that including fonio in the rotation scheme of cowpea and millet, adding millet residues or paunch contents with or without solar heating and application of 3 tons ha -1 of compost augmented with C . rosea reduced charcoal rot disease and increased cowpea yield. These methods can be integrated intodifferent combinations according to local conditions for managing charcoal rot.
    Socio-economic, agronomic and molecular analysis of yam and cowpea diversity in the Guinea-Sudan transition zone of Benin
    Zannou, A. - \ 2006
    Wageningen : Wageningen University and Research Centre (Tropical resource management papers no. 80) - ISBN 9789085850991 - 236
    boeren - kennis - inheemse kennis - communicatie - genetische bronnen van plantensoorten - pachyrhizus erosus - vignabonen - rassen (planten) - innovaties - bedrijfsvoering - benin - vigna unguiculata - yams - dioscorea - farmers - knowledge - indigenous knowledge - communication - plant genetic resources - pachyrhizus erosus - cowpeas - varieties - innovations - management - benin - vigna unguiculata - yams - dioscorea
    Socio-economic, agronomic and molecular analysis of yam and cowpea diversity in the Guinea-Sudan transition zone of Benin
    Zannou, A. - \ 2006
    Wageningen University. Promotor(en): Paul Richards; Paul Struik, co-promotor(en): V. Agbo; J. Zoundjihékpon. - Wageningen : WUR - ISBN 9789085044352 - 236
    farmers - knowledge - indigenous knowledge - communication - plant genetic resources - pachyrhizus erosus - cowpeas - varieties - innovations - management - benin - vigna unguiculata - yams - dioscorea - boeren - kennis - inheemse kennis - communicatie - genetische bronnen van plantensoorten - pachyrhizus erosus - vignabonen - rassen (planten) - bedrijfsvoering - benin - innovaties - vigna unguiculata - yams - dioscorea
    Keywords: Cowpea (Vigna unguiculata(L.) Walp.),yam ( Dioscorea spp. ), agro-biodiversity, farmer perception, market and consumer preferences, socio-cultural preferences, human and social capitals, genotype by environment interaction, socio-technical knowledge, domestication, inter-(trans)disciplinarity / Beta-gamma science.

    Management and use of yam and cowpea genetic resources analysed in this thesis are important to realize agricultural development inBenin, both on the short and long run. In this thesis the diversity of local varieties of yam and cowpea, often ignored by classical research, is analysed. Different meth­odological approaches, including technography, diagnostic study at village level, and joint farmer-researcher managed experimentation, have been combined with socio-cultural, market and consumer studies. Molecular tools have been used to assess the level of genetic diversity in these two crops.

    Socio-cultural determinants, market and consumers' preferences, and the morphological and agronomic characteristics of different varieties of these two crops are all relevant for social acceptability and adaptability, and for the adoption of new varieties by local subsistence farmers. Different yam and cowpea varieties are used for rituals each year. The yield performance varied from one variety to another, and within one variety, from one year to another (or one place to another) depending on variability in agro-climatic conditions. While any successful variety of yam or cowpea should be adapted to stressful agro-climatic or poor soil conditions, it should be also adapted to the often specific needs of the farmer and to his/her socio-cultural environment. Moreover, varieties need to satisfy consumer preferences and market demands. Often, one single variety of yam or cowpea cannot meet all these criteria. Given these multiple purposes and multiple objectives, adequate management of diversity of varieties is essential to farmers, as a strategy to cope with food security and income generation all year round.

    Prices of different varieties of yam and cowpea on the market reflect the food technological or taste characteristics perceived or recognized by consumers in these varieties. The market provides important information on diversity of varieties and on their characteristics.

    Based on the morphogenetic and physiological characteristics recognized by farmers as limitations, or as natural constraints in the proper use of seed tubers of different yam varieties, this thesis undertook a participatory technology development programme with farmers to improve the knowledge of both the researcher and the farmers of seed tuber propagation through induced sprouting, and through use of different parts of the tuber as planting materials. The thesis also pays attention to farmers' own experimentation in developing new yam varieties by domesticating wild yams, and shows that this activity - probably of ancient provenance inBenin- remains effective for farmers excluded by poverty from market participation. The improvement of the performance of these local
    varieties remains a major future task for researchers and policy-makers inBenin.

    Two major conclusions can be drawn from this thesis. The first is that both social and natural sciences are necessary contributors to the understanding of diversity in yam and cowpea varieties as managed and maintained by farmers. This diversity is expressed at the molecular level and at farm level, but is also highly relevant on the market and in the socio-cultural life of the farmers. The second conclusion relates to findings concerning the possibility of engaging farmers and researchers in joint study of yam and cowpea diversity, with beneficial practical consequences. Joint experimentation focused on varietal characterization, and the joint participatory technology development, indicated that more effective research results can be obtained when farmers' perceptions and depth of experience is fully incorporated in research design. In this regard, technography and diagnosis remain continuously reviewed, allowing the incorporation of new ideas or innovations and new stakeholders in the experimentation process. The results assessment with and by farmers remains an essential aspect of judging work in farmer conditions to improve local livelihoods. In particular, the thesis emphasizes that - through domestication of yam - the poor show that they can contribute actively to development of scientific perspectives. These aspects of the Convergence of Sciences as focused upon yam and cowpea varietal management embrace both an inter-disciplinary and trans-disciplinary research perspective. Cooperation and co-knowledge generation with farmers needs follow-up, and a scaling-up to reach other farmers. Specifically, it needs to be incorporated in the curricula of national research training systems.
    Input levels and intercropping productivity: exploration by simulation
    Wubs, A.M. ; Bastiaans, L. ; Bindraban, P.S. - \ 2005
    Wageningen : Plant Research International (Nota note 369) - 100
    sorghum bicolor - sorghum - vigna unguiculata - vignabonen - teeltsystemen - tussenteelt - simulatiemodellen - input van landbouwbedrijf - watergebruiksrendement - afrika - sorghum bicolor - sorghum - vigna unguiculata - cowpeas - cropping systems - intercropping - simulation models - farm inputs - water use efficiency - africa
    Voorstudie van het effect van verschillende niveaus van waterinput op een sorghum-cowpea intercrop
    Mechanisms underlying Cowpea mosaic virus systemic infection
    Santos Silva, M. - \ 2004
    Wageningen University. Promotor(en): R.W. Goldbach, co-promotor(en): Jan van Lent; Joan Wellink. - Wageningen : S.n. - ISBN 9789085040385 - 118
    koebonenmozaïekvirus - manteleiwitten - vigna unguiculata - beweging - plantenvirussen - ziekteresistentie - cowpea mosaic virus - coat proteins - vigna unguiculata - movement - plant viruses - disease resistance
    Systemic virus infection of plants involves; intracellularreplication, cell-to-cell movement within the inoculated leaf, and subsequently, long-distance spread to other plant parts via the vasculature (vascular movement).Cell-to-cell movement occurs through the plasmodesma (PD), which are regulated channels in the cell wall connecting adjacent cells. These PD are modified by plant viral movement proteins (MPs) to allow passage of a viral RNA-MP complex as happens with Tobacco mosaic virus (TMV),or virions as happens with Cowpea mosaic virus (CPMV). With the latter virus, virions move through tubules built-up from the MP (tubule-guided cell-to-cell movement). For vascular movement, viruses must enter (loading), translocate through, and exit (unloading) from the phloem. Phloem (un)loading occurs through specialized PD, named the pore-plasmodesma-unit (PPU), connecting the companion cell (CC) and sieve element (SE). The PPU allows passage of much larger molecules than mesophyll PD do. Because of the peculiarities inherent to phloem tissue (e.g. PPU), mechanisms of cell-to-cell movement are usually distinct from those of vascular movement (reviewed in Chapter 1) for the same virus. For instance, TMV requires the viral coat protein (CP) for transport of virions through PPU, but the CP is dispensable for cell-to-cell movement. The success of plant virus infection is also the consequence of an antagonistic balance between viral infection and plant host defence mechanisms that specifically target viral replication (e.g. RNA silencing), or movement (e.g. systemic acquired resistance). In this research thesis CPMV was used as a model for investigations on the mechanisms of systemic infection of plants. Since CPMV replication and cell-to-cell movement are well-investigated, the thesis research was concentrated on vascular movement of CPMV and on barriers imposed by different plant species against systemic infection by this virus.To examine the characteristics of vascular movement in Vigna unguiculata (cowpea), GFP-expressing CPMV (CPMV-GFP) was mechanically inoculated to primary leaves and infection was followed over time (Chapter 2). CPMV-GFP was loaded into both major and minor veins of the primary leaves and unloaded exclusively from major veins, preferentially class III, in the secondary leaves similar to the route of photo-assimilates via phloem. Using electron microscopy, virus infection was observed in all vascular cell types of the loading and unloading sites, with the exception of CC and SE. Furthermore, tubules transporting virions were never found in the PD connecting; phloem parenchyma cells (PPC) and CC, or CC and SE (i.e. PPU). Since in cowpea the SE is symplasmically connected only to the CC, these observations suggest that, unlike cell-to-cell movement, CPMV vascular movement is not tubule-guided.Mutational analysis by reverse genetics is the most common approach to the study of viral factors necessary for vascular movement. CPMV requires its MP and both coat proteins (CPs) for tubule-guided cell-to-cell movement, deletion of any of these genes results in impeded local spread and this restriction severely hampers application of reverse genetics on CPMV for this purpose. In Chapter 3, an attempt was made to circumvent this problem by providing the CPs intrans by agroinfiltration in N. benthamiana to complement cell-to-cell movement of a CPMV mutant devoid of CPs (CPMV-DCP). The aim was to observe whether the mutant would exit from vascular tissue in the absence of CPs in the upper leaves. Whiletrans complementation of CPMV-DCP cell-to-cell movement was demonstrated in planta , the extent of spread was not sufficient to allow CPMV-DCP phloem loading, thus the phloem unloading of the mutant within the upper leaves could not be analysed. Immunoblot analysis of vascular sap from infected cowpea plants showed the presence solely of viral CPs. Furthermore, virions were found in the vasculature of CPMV-immune cowpea scions grafted on CPMV-inoculated susceptible rootstocks (Chapter 3). These results indicate that CPMV circulates in the vasculature in form of mature virions. However, it could not be unequivocally determined whether virions were located in the phloem or in the xylem. As systemic spread by xylem has been reported for beetle transmissible viruses like CPMV, beetle transmission was mimicked by gross-wound inoculation (Chapter 3). However, in this case, as with mechanical inoculation using an abrasive, CPMV spread systemically via the phloem, i.e. directed to sink-leaves solely like the flow of photo-assimilates. This confirms that phloem is the prevailing route for CPMV vascular movement.The potential role of RNA silencing during establishment of infection by CPMV was studied in Chapter 4. Using GFP-expressing CPMV constructs and N. benthamiana as host, the number of infection foci was recorded in the absence or presence of different viral suppressors of RNA silencing, i.e. potyviral HC-Pro, tospoviral NSs and cucumoviral 2b. Upon inoculation with CPMV in vitro transcripts, HC-Pro and NSs, but not 2b, significantly increased the number of CPMV primary infection foci. These results indicate that RNA silencing already has an impact on the establishment of infection even at an early stage. Interestingly, the stimulating effect of suppressors was not observed upon inoculation with virions. This effect may be explained by the recent finding (Lomonossoff, personal communication) that the small (S) CP acts as a suppressor of RNA silencing. To assess the effect of RNA silencing on viral local spread, GFP-expressing CPMV constructs impaired in local spread were tested in the presence or absence of HC-Pro or NSs. Neither of these proteins affected the progress of infection, indicating that RNA silencing does not play a major role in this stage. In Chapter 5, N. tabacum , a semi-permissive host of CPMV, was used to further unravel the viral systemic infection process. CPMV does not infect N. tabacum systemically despite extensive local spread in inoculated leaves. It is shown that neither incubation temperature nor RNA silencing-, salicylic acid- or ethylene-mediated resistance mechanisms are the limiting factor for CPMV systemic infection. Although CPMV-infected N. tabacum plants are normally asymptomatic, symptoms (i.e. necrotic lesions) in the inoculated leaves were observed at low (15 °C) temperature, but not systemic movement. Grafting experiments indicate that CPMV is not capable of phloem loading in N. tabacum , a finding that makes this plant species an interesting system for investigations of the host factors involved in CPMV vascular movement.Finally, in Chapter 6 possible mechanisms of vascular movement of CPMV are presented based on the results obtained in this thesis. Moreover, the various virus-host interactions, which contribute to the success or failure of systemic infection, are put into perspective.
    Biocontrol in store: spatial and behavioural aspects of foraging by Uscana lariophaga, egg parasitoid of Callosobruchus maculatus, in stored cowpea
    Stolk, C. - \ 2002
    Wageningen University. Promotor(en): J.C. van Lenteren; A. van Huis; W. van der Werf. - S.l. : S.n. - ISBN 9789058087416 - 160
    vignabonen - callosobruchus maculatus - voorraadplagen - biologische bestrijding - vigna unguiculata - trichogrammatidae - parasitoïden - voedingsgedrag - gedrag bij zoeken van een gastheer - cowpeas - vigna unguiculata - callosobruchus maculatus - stored products pests - trichogrammatidae - parasitoids - feeding behaviour - host-seeking behaviour - biological control

    Cowpea ( Vigna unguiculata Walpers), an important crop for West African subsistence farmers, is often infested in storage by the bruchid beetle Callosobruchus maculatus Fabricius. The indigenous egg parasitoid Uscana lariophaga Steffan (Hym.: Trichogrammatidae) is responsible for substantial mortality of C. maculatus eggs and might therefore be used in a conservation strategy of biological control. This thesis focuses on foraging behaviour of U. lariophaga females in a spatial context. In stored cowpea, the bruchid oviposits in clusters. Uscana lariophaga is well adapted to such clusters, since it shows a strong arrestment response after an encounter with an unparasitized host. Previous investigations had already shown attraction of the parasitoid to host-related odours; it is now shown that directed search probably occurs at a short distance (4-6 beans) from the host patch. The probability that a host patch in stored cowpea is found decreases rapidly with increasing distance between the host patch and the site of release of the parasitoid. The 'critical distance' within which the host patch is quickly found by the parasitoid increases if more searching time is allowed. If an experienced parasitoid arrives in a host patch and encounters parasitized hosts, it is likely to superparasitize, but it will stop superparasitizing as soon as an unparasitized host has been encountered in the same patch. Superparasitism by experienced females is not due to failure in host discrimination, as appears from the fact that females adapt the sex ratio of their offspring during superparasitism. If no or few hosts are available, the parasitoid lives shorter than when many hosts are available. This reduced longevity at low host densities may be due to an increased walking activity at low host densities. Finally, the potential of a simulation model of U. lariophaga behaviour is shown, and consequences of behaviour for the prospects of biological control are discussed.

    Traditional African plant products to protect stored cowpeas against insect damage : the battle against the beetle
    Boeke, S.J. - \ 2002
    Wageningen University. Promotor(en): M. Dicke; J.J.A. van Loon; A. van Huis. - S.l. : S.n. - ISBN 9789058087362 - 151
    vigna unguiculata - vignabonen - callosobruchus maculatus - voorraadplagen - plantaardige insecticiden - insecticiden bevattende planten - vigna unguiculata - cowpeas - callosobruchus maculatus - stored products pests - botanical insecticides - insecticidal plants

    Seeds of the cowpea plant, Vigna unguiculata , a tropical crop, are very susceptible to attack by the cowpea beetle. This specialist beetle needs only the beans to reproduce rapidly.

    Most farmers in West Africa have few possibilities to treat the beans and they face their stored supply, on which they are dependent for their daily nourishment, be destroyed within a few months. From lack of other measures, these farmers traditionally used plants, stored together with the beans for protection. In the laboratory, such plants have been tested as powders and as extract for their effect against the beetle. Side effects on natural enemies of the beetle have also been tested for and in a review of the literature, effects on humans have been investigated. Together with the results from a field test in Africa, this gives a picture of the potency of local means to protect stored seeds against insects.

    Origin of the membrane compartment for cowpea mosaic virus RNA replication
    Carette, J.E. - \ 2002
    Wageningen University. Promotor(en): A. van Kammen; J. Wellink. - S.l. : S.n. - ISBN 9789058085573 - 120
    koebonenmozaïekvirus - dna-replicatie - membranen - vigna unguiculata - vignabonen - blaasjes - virusreplicatie - plantenziekten - cowpea mosaic virus - dna replication - membranes - vigna unguiculata - cowpeas - vesicles - viral replication - plant diseases

    Replication of many positive-stranded RNA viruses takes place in association with intracellular membranes. Often these membranes are induced upon infection by vesiculation or rearrangement of membranes from different organelles including the early and late endomembrane system. Upon infection of cowpea cells with cowpea mosaic virus (CPMV) typical cytopathological structures are formed, which consist of an amorphous matrix of electron-dense material traversed by rays of small membranous vesicles. This thesis describes the studies that were undertaken to define the cellular components involved in the establishment of the site of viral RNA replication consisting of vesiculated membranes and electron-dense material. Furthermore, the role of individual viral proteins as well as host proteins in this process was investigated.

    The use of plant material to protect stored leguminous seeds against seed beetles: a review
    Boeke, S.J. ; Loon, J.J.A. van; Huis, A. van; Kossou, D.K. ; Dicke, M. - \ 2001
    Leiden : Backhuys Publishers (Wageningen University papers 2001-3) - ISBN 9789057821004 - 108
    voorraadplagen - coleoptera - insecticiden bevattende planten - insectenplagen - insectenafweermiddelen - bruchidae - vigna unguiculata - fabaceae - zaden - overzichten - stored products pests - seeds - coleoptera - insecticidal plants - insect pests - insect repellents - bruchidae - vigna unguiculata - fabaceae - reviews
    The helper component-proteinase of cowpea aphid-borne mosaic virus
    Mlotshwa, S. - \ 2000
    Agricultural University. Promotor(en): A. van Kammen; J. Wellink; I. Sithole-Niang. - S.l. : S.n. - ISBN 9789058083401 - 111
    vigna unguiculata - vignabonen - potyvirus - kousenbandrolmozaïekvirus - pathogeniteit - weerstand - dna-sequencing - dna - genoomanalyse - genetische modificatie - genetische transformatie - ziekteresistentie - vigna unguiculata - cowpeas - potyvirus - blackeye cowpea mosaic virus - pathogenicity - resistance - dna sequencing - dna - genome analysis - genetic engineering - genetic transformation - disease resistance

    Cowpea aphid-borne mosaic potyvirus causes severe yield losses in cowpea, an important legume crop in semi-arid regions of Africa. We have elucidated the genomic sequence of the virus and subsequently focused our attention on the so-called helper component-proteinase (HC-Pro), a virus-encoded multifunctional protein with roles in different steps of the virus life cycle. Our study has shed more insight into some of the molecular properties of this protein. We have shown that HC-Pro is able to shut down host defense responses, and this puts HC-Pro at the core of the success of CABMV as a pathogen. The phenomenon also seems to benefit other viruses as they accumulate to higher levels and elicit enhanced symptoms in the presence of HC-Pro. On the other hand, we have found that the host does manifest an ability to counter the deleterious effects of HC-Pro. A full understanding of the molecular basis of this contest would enable the design of effective new strategies to protect plants from virus infections.

    Molecular characterisation of the cowpea mosaic virus movement protein
    Bertens, P. - \ 2000
    Agricultural University. Promotor(en): A. van Kammen; J. Wellink. - S.l. : S.n. - ISBN 9789058083104 - 144
    virologie - koebonenmozaïekvirus - vignabonen - vigna unguiculata - comovirus - transport - eiwitten - plasmodesmata - virology - cowpea mosaic virus - cowpeas - vigna unguiculata - comovirus - transport - proteins - plasmodesmata

    Virussen zijn subcellulaire parasieten die niet zelfstandig kunnen bestaan, maar cellen binnendringen en cellulaire mechanismen van hun gastheer gebruiken voor vermenigvuldiging. Virussen zijn verantwoordelijk voor vele ernstige ziektes bij mensen en dieren (zoals bijvoorbeeld griep, verkoudheid of AIDS), maar ook bij planten, waar virussen verantwoordelijk kunnen zijn voor de vernietiging van hele oogsten. Virussen zijn vrij eenvouding van structuur en bevatten een kleine hoeveelheid genetisch materiaal, dat uit DNA of RNA kan bestaan. Dit genoom is omgeven door een beschermende eiwitlaag, de mantel.

    Terwijl dierlijke virussen normaal cellen binnenkomen via chemische interacties met specifieke herkenningsmoleculen (receptoren) in de celmembraan, zijn celmembranen van plantencellen omhuld door een pantserbekleding van cellulose die een ondoordringbare hindernis vormt voor plantenvirussen. De meeste virussen kunnen een plant pas binnendringen na mechanische beschadiging of met behulp van een biologische vector (b.v. een bladluis of een ander insect) die de virussen tijdens het voeden rechtstreeks in een gastheercel binnenbrengen. In zo een initiëel geïnfecteerde cel wordt het virale genoom, dat uit één of meerdere DNA of RNA moleculen kan bestaan, vertaald in virale eiwitten die zorg dragen voor de replicatie van het virale genoom en de bemanteling van het virale RNA. Na deze vermenigvuldigingsstap verspreidt het virus zich verder door de plant en zal in eerste instantie de naburige cellen infecteren (via het zogeheten lokaal transport of cel-cel transport). Nadat een infectie de vaatbundels bereikt heeft, zullen virusdeeltjes zich via de vaatbundels door de rest van de plant verspreiden (het lange-afstands transport). In de hoger gelegen bladeren treedt het virus de vaatbundels weer uit, en verspreidt het zich opnieuw via cel-cel transport naar andere cellen van dat blad.

    Als een virus zich vanuit een initiëel geïnfecteerde cel naar naburige cellen wil verspreiden, stuit het opnieuw op de ondoordringbare celwand. Deze hindernis wordt met behulp van een speciaal mechanisme omzeilt. In de celwand zitten nauwe kanaaltjes, de plasmodesmata, die naburige cellen met elkaar verbinden. Deze kanaaltjes spelen een rol bij de verspreiding van (voedings)stoffen en worden door de plant gebruikt voor intercellulaire communicatie. Virussen zouden deze plasmodesmata kunnen gebruiken voor lokaal transport, ware het niet dat ze te groot zijn om door de kanaaltjes heen te kunnen gaan. De oplossing die virussen hebben ontwikkeld om dit probleem te omzeilen is even elegant als simpel: ze coderen voor een specifiek eiwit (het transporteiwit, afgekort MP voor het Engelse "movement protein"), die de diameter van plasmodesmata kan vergroten, waardoor transport van virusdeeltjes of complexen van viraal RNA en MP mogelijk wordt. In hoofdstuk 1 wordt een overzicht gegeven van virale MPs en de verschillende mechanismen die plantenvirussen hebben ontwikkeld om zich van cel naar cel te verspreiden.

    Dit proefschrift beschrijft een onderzoek waarin het MP van het koebonenmozaïekvirus (op z'n Engels "cowpea mosaic virus" (CPMV) geheten) centraal staat. Dit virus infecteert voornamelijk tropische planten, waaronder kouseband ( Vigna unguiculata ), een plant waarvan de peulen vooral in Afrika en Zuid-Amerika een belangrijke voedingsmiddel zijn (kouseband is ook in Nederland op veel plaatsen te koop; voor een tip hoe deze te bereiden, kan de auteur van dit proefschrift benaderd worden). Een infectie van kouseband door CPMV wordt gekenmerkt door de vorming van milde tot hevige mozaïek-symptomen op geïnfecteerde bladeren, die tot afsterven van het blad kan leiden. Het genoom van CPMV bestaat uit een tweetal enkelstrengs RNA moleculen met een positieve polariteit. Deze RNA moleculen worden in een geïnfecteerde cel vertaald in een drietal polyeiwitten, die door een viraal enzym in stukken worden geknipt tot kleinere producten. De door het RNA1 gecodeerde eiwitten zijn betrokken bij de virale replicatie. De eiwitten die gecodeerd worden door RNA2, spelen een rol bij het cel-cel en het lange-afstands transport van CPMV. Dit zijn de twee manteleiwitten LCP en SCP, een 58K eiwit, dat nodig is voor replicatie van RNA2 en het MP.

    Met behulp van electronen-microscopische analyse zijn in CPMV-geïnfecteerd weefsel buisvormige structuren aangetroffen, die gevuld zijn met virusdeeltjes. Deze buizen steken door een gemodificeerde plasmodesma van een geïnfecteerde cel in het cytoplasma van een naburige cel. Soortelijke structuren zijn aangetroffen in protoplasten (geïsoleerde plantencellen) die geïnfecteerd zijn met CPMV en in protoplasten of insectencellijnen waarin alleen het MP specifiek tot expressie is gebracht. Deze experimenten laten zien dat voor de vorming van de buizen geen plasmodesmata nodig zijn. Biochemische analyse van de buizen heeft laten ziendat de buizen grotendeels of zelfs helemaal zijn opgebouwd uit het MP.

    Het proces van buisvorming gebeurd waarschijnlijk in een aantal stappen. Nadat het MP aangemaakt is in virale replicatie complexen moet het naar de celmembraan getransporteerd worden, waar het zich bij plasmodesmata zal ophopen en een buis zal vormen. Tijdens deze buisvorming worden de virusdeeltjes in de buis ingebouwd. De plasmodesma waarin de buis wordt gevormd, wordt drastisch gemodificeerd. Verschillende gebieden (domeinen) van het MP zullen een specifieke rol hebben en betrokken zijn bij een of meerdere van de hierboven beschreven stappen. In hoofdstuk 2 hebben we getracht zulke domeinen te vinden door met behulp van moleculair-biologische technieken mutaties aan te brengen binnen het MP en het effect hiervan op onder andere de buisvorming te onderzoeken. Uit de resultaten blijkt dat het resultaat van een subtiele mutatie heel drastisch kan zijn. Sommige mutaties hebben tot gevolg dat het MP geen buizen meer kan vormen. Virussen die dit mutant MP bezitten zijn niet meer in staat om zich te verspreiden in planten. Mutaties aangebracht op andere plaatsen in het MP lijken nauwelijks effect te hebben op de eigenschappen van het transporteiwit. We hebben ontdekt dat het N-terminale en het centrale deel van het MP nodig zijn voor het transport naar de plasmodesmata en voor de vorming van de buizen.

    Het volgen van een virusinfectie in levende planten is erg moelijk. Virussen zijn alleen maar te zien onder een electronenmicroscoop waarvoor men echter de delen van de plant die men wil onderzoeken moet fixeren. Door deze behandeling sterven de plantcellen en kunnen er allerlei ongewilde veranderingen (artefacten) optreden in het weefsel. Een paar jaar terug is er een nieuwe methode ontwikkeld om een virusinfectie in levende planten te volgen. Men maakt hiervoor gebruik van een fluorescent eiwit, het "green fluorescent protein" (GFP). Dit eiwit komt van nature voor in kwallen en heeft de bijzondere eigenschap om groen op te lichten (te fluoresceren) indien het wordt beschenen met UV-licht. Met behulp van moleculair-biologische technieken is dit GFP ingebouwd in CPMV. Als we planten hiermee infecteren, kunnen we de infectie in de tijd volgen door de planten onder een UV-lamp of onder een fluorescentie-microscoop te onderzoeken, zoals staat beschreven in de hoofdstukken 3 en 4.

    In hoofdstuk 3 hebben we ons geconcentreerd op het C-terminale deel van het MP. Door de analyse van deletie-mutanten en hybride MPs (bestaande uit delen van het MP van het rode-klavervlekkenvirus en dat van CPMV) was het mogelijk om bijna op het aminozuur nauwkeurig de grens aan te geven van het domein dat betrokken is bij de vorming van buizen. De buizen gevormd door een MP mutant, waarin de laatste 10 aminozuren waren vervangen door GFP, bleken geen virusdeeltjes te bevatten. Blijkbaar blokkeert GFP het functioneren van een MP domein dat betrokken is bij de inbouw van virusdeeltjes in buizen. Indien een virus naast wild-type (normaal) MP ook een mutant MP (die geen functionele C-terminus heeft) bezit, verspreidt het virus zich toch door de plant. De buizen, die waarschijnlijk zowel uit het wild-type alsook het mutant MP bestaan, zijn niet helemaal netjes gevuld met virusdeeltjes. Af en toe lijkt er wat ruimte tussen de verschillende deeltjes te zitten. Deze resultaten geven aan dat alle C-termini nodig zijn voor het virale transport.

    Een van de bijzondere eigenschappen van GFP is, dat na fusie van GFP aan een ander eiwit (b.v. het MP), de intracellulaire localisatie van dat eiwit kan worden bekeken in levend materiaal. In hoofdstuk 4 hebben we de intracellulaire locatie van een aantal fusieproducten tussen GFP en het CPMV MP nader onderzocht. In eerste instantie hebben we een fusie gemaakt tussen het wild-type MP en GFP. Een virus coderend voor dit MP:GFP fusieproduct was in staat (fluorescente) buizen te maken in protoplasten. In planten hoopt het MP:GFP zich op als opvallende punten (spots) in de celwand. Deze plaatsen zijn waarschijnlijk de eerder aangehaalde gemodificeerde plasmodesmata, waar cel-cel verspreiding van het virus plaatsvindt. In sommige gevallen werden zelfs fluorescente buizen in de celwand aangetroffen. De infectie van dit genetisch gemodificeerde virus bleek echter beperkt tot enkele cellen. Vervolgens zijn een aantal van de in hoofdstuk 2 gekarakteriseerde MP mutanten gefuseerd aan GFP en is de localisatie van deze mutant MP:GFP eiwitten bekeken in protoplasten en planten. MPs die een mutatie bevatten in hun centrale deel bleken verstoord te zijn in het intracellulaire transport naar de celmembraan en hoopten zich op in het cytoplasma. Een van de mutant MP:GFPs hoopte zich tevens op in structuren die in de buurt van de celkern in het cytoplasma liggen. Waarschijnlijk zijn dit virale replicatie-complexen en is dit mutant MP:GFP niet in staat zich hieruit los te maken. Mutante MP:GFPs met veranderingen in het C-terminale deel van het MP werden wel naar de celmembraan getransporteerd, maar waren verstoord in de initiatie of elongatie van de buizen.

    We kunnen concluderen dat het in dit proefschrift beschreven onderzoek heeft geleid tot een beter inzicht in het mechanisme dat CPMV gebruikt voor zijn cel-cel verspreiding. Middels mutatie-analyse en door gebruik te maken van GFP hebben we een aantal functionele domeinen van het CPMV MP geïdentificeerd. We kunnen het MP grofweg in twee functionele domeinen verdelen. Een groot deel van de N-terminale en centrale gebieden van het eiwit zijn betrokken bij de vorming van buisvormige structuren in protoplasten en planten. Dit domein is onder te verdelen in gebieden die betrokken zijn bij het intracellulaire transport naar de plasmodesmata toe en in gebieden die een rol spelen bij de initiatie van buisvorming. Het C-terminale deel is niet betrokken bij buisvorming, maar speelt een rol bij de inbouw van virusdeeltjes in de buizen. De in dit proefschrift beschreven resultaten zullen worden gebruikt voor vervolgstudies, die onder andere gericht zullen zijn op de identificatie van gastheer-eiwitten die een interactie aangaan met het CPMV MP en op het ophelderen van het intracellulaire transport van het MP.

    Vruchtzetting en mate van vulling van de peulen in relatie tot plaats en tijdstip van de bloei bij Vigna unguiculata (L.) Walp.; Teelt van enkele gewassen op ruggen in de grote regentijd; vergelijkende opbrengstproef met de rijstcultivars IR 8 en Acorni bij drie plantdichtheden; Eerste aanplantingen van peulgewassen in de proeftuin Coebiti : 1. Observatieverplichtingen van soja, aardnoot en katjang idjo : 2. een stikstofnemestingsproef met soja en katjang idjo : 3. Een onderzoek naar het effekt van Rhizobiuminokulatie op opbrengst en stikstofgehalte van katjang idjo
    Hoving, E. - \ 1973
    Wageningen : Landbouwhogeschool (Celos rapporten no. 83)
    landbouwkundig onderzoek - onderzoeksprojecten - suriname - vigna unguiculata - vignabonen - plantenontwikkeling - ruggen - gewasteelt - opbrengsten - cultivars - plantdichtheid - peulgewassen - stikstofgehalte - bemesting - rhizobium - agricultural research - research projects - suriname - vigna unguiculata - cowpeas - plant development - ridges - crop management - yields - cultivars - plant density - legumes - nitrogen content - fertilizer application - rhizobium
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