Staff Publications

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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    Nieuwsbrief Basis juli 2014
    Balen, D.J.M. van; Haagsma, W.K. - \ 2014
    PPO AGV
    akkerbouw - bodemfactoren - proeven op proefstations - grondbewerking - biologische landbouw - organische stof - opbrengsten - arable farming - edaphic factors - station tests - tillage - organic farming - organic matter - yields
    Nieuwsbrief in het kader van de bodemprojecten op PPO-proefbedrijf Lelystad.
    Sleuventeelt appel binnen handbereik
    Maas, M.P. van der; Roelofs, P.F.M.M. ; Elk, P.J.H. van; Dieren, M.C.A. van - \ 2013
    De Fruitteelt 103 (2013)46. - ISSN 0016-2302 - p. 6 - 8.
    fruitteelt - vruchtbomen - malus - teeltsystemen - zandgronden - proefprojecten - fertigatie - plantenvoeding - groeieffecten - economische haalbaarheid - alternatieve methoden - bodemfactoren - fruit growing - fruit trees - cropping systems - sandy soils - pilot projects - fertigation - plant nutrition - growth effects - economic viability - alternative methods - edaphic factors
    Een economische prespectievenstudie toonde aan dat sleuventeelt geen luchtfietserij is. De plukgegevens van 2013 versterken dat beeld. Het onderzoek naar de teelt van appel in sleuven werd drie jaar geleden opgezet om een alternatief te vinden voor de chemische grondontsmetting op zandgronden. Inmiddels is dit systeem ook interessant voor andere gronden met slechte afwatering, slechte bodemstructuur of met zout veen of zout water in de ondergrond.
    Modelling of soil salinity and halophyte crop production
    Vermue, E. ; Metselaar, K. ; Zee, S.E.A.T.M. van der - \ 2013
    Environmental and Experimental Botany 92 (2013). - ISSN 0098-8472 - p. 186 - 196.
    gewasproductie - bodemfactoren - zoute gronden - halofyten - bodemwater - verzilting - modellen - crop production - edaphic factors - saline soils - halophytes - soil water - salinization - models - salt tolerance - root water - growth - plants - irrigation - stress - extraction - simulation - wheat - transpiration
    In crop modelling the soil, plant and atmosphere system is regarded as a continuum with regard to root water uptake and transpiration. Crop production, often assumed to be linearly related with transpiration, depends on several factors, including water and nutrient availability and salinity. The effect of crop production factors on crop production is frequently incorporated in crop models using empirical reduction functions, which summarize very complex processes. Crop modelling has mainly focused on conventional crops and specific plant types such as halophytes have received limited attention. Crop modelling of halophytes can be approached as a hierarchy of production situations, starting at the situation with most optimal conditions and progressively introducing limiting factors. We analyze crop production situations in terms of water- and salt limited production and in terms of combined stresses. We show that experimental data as such may not be the bottleneck, but that data need to be adequately processed, to provide the basis for a first analysis. Halophytic crops offer a production perspective in saline areas, but in other areas long-term use of low quality irrigation water for halophyte production can result in serious soil quality problems. An overview is given of potential problems concerning the use of (saline) irrigation water, leading to the conclusion that soil quality changes due to poor quality water should be considered in determining the areas selected for halophyte growing.
    Beworteling van grasland en droogtetolerantie : maatregelen voor een diepere beworteling
    Luske, B. ; Deru, J.G.C. ; Wosten, J.H.M. ; Faber, J.H. ; Eekeren, N.J.M. van - \ 2012
    Driebergen : Louis Bolk Instituut (Publicatie / Louis Bolk Instituut 2012-028 LbD) - 51
    graslanden - bewortelingsdiepte - zandgronden - bodem-plant relaties - bodemfactoren - droogteresistentie - grasslands - rooting depth - sandy soils - soil plant relationships - edaphic factors - drought resistance
    Aan de hand van de literatuur en langlopende proeven zijn de meest veelbelovende maatregelen om de bewortelingsdiepte van grasland te bevorderen op een rijtje gezet. Preventie van bodemverdichting door vertrapping en structuurschade en werken aan de herstelcapaciteit van de bodem is belangrijk. Maatregelen die hierbij horen zijn: verhogen van het organische stof gehalte, op peil houden van de pH en bevorderen van aantallen en activiteit van wormen. Ook kunnen er maatregelen genomen worden bij de inzaai van graslanden door snelgroeiende diepwortelende gewassen als dekvrucht te gebruiken en diepwortelende grassoorten of grasrassen te kiezen. Via de bemesting kan de beworteling verbeterd worden door de N-gift te verlagen, de N-gift uit te stellen na maaien en deze toe te dienen onder het maaiveld. Hoger maaien en minder frequent maaien of beweiden vallen ook onder de management opties voor een betere beworteling.
    Bodemweerbaarheid complex begrip voor onderzoek en praktijk (interview met G. van Os, J. Postma en A. van der Wurff)
    Dwarswaard, A. ; Os, G.J. van; Postma, J. ; Wurff, A.W.G. van der - \ 2012
    BloembollenVisie 2012 (2012)256. - ISSN 1571-5558 - p. 16 - 17.
    bloembollen - bodemfactoren - bodemonderzoek - bodemeigenschappen - weerstand - ziekteresistentie - landbouwkundig onderzoek - kennisoverdracht - ornamental bulbs - edaphic factors - soil testing - soil properties - resistance - disease resistance - agricultural research - knowledge transfer
    Wie pakweg tien jaar geleden in de bloembollensector begon over bodemweerbaarheid werd een beetje meewarig aangekeken. Nu is dat anders. Belangrijk, meer aan doen, dat zijn de opvattingen die een groeiende groep telers heeft. Om die reden wijdt BloembollenVisie een serie aan bodemweerbaarheid, bodemvruchtbaarheid en bodemleven. In de vierde aflevering is het woord aan drie onderzoekers van PRI en PPO van Wageningen UR die zich met deze drie onderwerpen bezighouden.
    Kan stikstofbemestingsadvies maïs flexibeler?, thema: duurzame mineralen BO-12.03-002-008
    Dijk, W. van; Berge, H.F.M. ten - \ 2011
    S.n.
    maïs - bemesting - stikstof - flexibiliteit - groeifactoren - bodemfactoren - efficiëntie - maize - fertilizer application - nitrogen - flexibility - growth factors - edaphic factors - efficiency
    Informatieposter stikstofbemestingsadvies bij maïs. Het huidige stikstofbemestingsadvies voor maïs houdt slechts in beperkte mate rekening met verschillen in groei- en bodemomstandigheden. Door hierop meer in te spelen, is stikstof mogelijk efficiënter inzetbaar. Bij lagere gebruiksnormen kunnen hierdoor opbrengstdervingen worden beperkt of voorkomen
    Schadelijke aaltjes liggen op de loer : Interview met Leendert Molendijk
    Meijering, Luuk ; Molendijk, L.P.G. - \ 2011
    Boerderij/Akkerbouw 96 (2011)19. - ISSN 0169-0116 - p. E12 - E114.
    nematiciden - gewasbescherming - akkerbouw - bodemkwaliteit - nematodenbestrijding - bodemfactoren - bodempathogenen - grondsterilisatie - nematicides - plant protection - arable farming - soil quality - nematode control - edaphic factors - soilborne pathogens - soil sterilization
    Het aantal percelen waarin schadelijke aaltjes voorkomen neemt langzaam toe. met voldoende kennis en de juiste maatregelen zijn ze goed te beheersen
    Toepassingsmogelijkheden van ziektewering in de praktijk
    Lamers, J.G. ; Westerdijk, C.E. - \ 2005
    Gewasbescherming 36 (2005)5. - ISSN 0166-6495 - p. 193 - 197.
    bodem - bodemfactoren - bodemeigenschappen - weerstand - bodemflora - bodembiologie - bodemfauna - ziekteresistentie - plantenziekten - gewasbescherming - triticum - gaeumannomyces - thanatephorus cucumeris - bloemkolen - suikerbieten - aardappelen - vollegrondsteelt - soil - edaphic factors - soil properties - resistance - soil flora - soil biology - soil fauna - disease resistance - plant diseases - plant protection - triticum - gaeumannomyces - thanatephorus cucumeris - cauliflowers - sugarbeet - potatoes - outdoor cropping
    In dit artikel gaat het over ziektewering voornamelijk als gevolg van biologische oorzaken. Dit is het gehele complex van bodemflora en -fauna die interacteren met het pathogeen, de omgeving en met het gewas. Er is een algemene ziektwering en een specifieke ziektewering te onderscheiden. Besproken worden de intensief onderzochte pathogeen-gewas combinaties tarwehalmdoder - tarwe en Rhizoctonia solani - bloemkool/suikerbiet/aardappel. Verder het maximaliseren van de bodemweerbaarheid en het tegengaan van verlaging van de bodemweerbaarheid
    Genoom analyse van ziektewerende bodems
    Overbeek, L.S. van; Speksnijder, A.G.C.L. - \ 2005
    Gewasbescherming 36 (2005)5. - ISSN 0166-6495 - p. 225 - 227.
    gewasbescherming - ziektepreventie - bodem - bodemfactoren - bodemeigenschappen - grondanalyse - bodemkunde - bodembiologie - bodemflora - bodemschimmelgroeiremming - antibiotica - antibacteriële eigenschappen - genen - genenbanken - dna-probes - dna - bodemvruchtbaarheid - plant protection - disease prevention - soil - edaphic factors - soil properties - soil analysis - soil science - soil biology - soil flora - soil fungistasis - antibiotics - antibacterial properties - genes - gene banks - dna probes - dna - soil fertility
    Het grootste deel van de micro-organismen in de bodem is niet bekend. Micro-organismen kunnen een stimulerende werking hebben op plant en dier en zelfs een beschermende functie uitoefenen. Opportunistische belagers van buitenaf kunnen worden afgeweerd door competitie en antibiotica productie. Beschreven wordt hoe via DNA technieken de bodempopulatie wordt gemonitord. Naast de aanwezigheid en diversiteit van micro-organismen wordt ook gekeken naar de aanwezigheid van genen die direct verantwoordelijk zijn voor bepaalde processen. Hiermee wordt een genenbank van werende bodems samengesteld. Deze genenbank wordt met DNA probes onderzocht op biologische activiteit. Onbekende antibiotica-genen worden verder onderzocht.
    Themanummer Bodemweerbaarheid
    Postma, J. ; Os, G.J. van; Schneider, J.M.H. - \ 2005
    Gewasbescherming 36 (2005)5. - ISSN 0166-6495 - p. 189 - 233.
    gewasbescherming - bodem - bodemfactoren - bodemeigenschappen - weerstand - ziekteresistentie - pathogenen - plant protection - soil - edaphic factors - soil properties - resistance - disease resistance - pathogens
    Inleidend hoofdstuk van het themanummer Bodemweerbaarheid van het tijdschrift Gewasbescherming. In dit hoofdstuk wordt het onderwerp afgebakend en uitgelegd waarom voor het thema 'Bodemweerbaarheid' is gekozen
    Bodemweerbaarheid tegen Rhizoctonia solani AG 2-1 in bloemkool
    Postma, J. ; Schilder, M.T. - \ 2005
    Gewasbescherming 36 (2005)5. - ISSN 0166-6495 - p. 208 - 211.
    gewasbescherming - plantenziekteverwekkende schimmels - plantenziekteverwekkers - bodemschimmels - thanatephorus cucumeris - waardplanten - brassica - bodemflora - weerstand - bodemfactoren - toegepast onderzoek - analyse - bloemkolen - plant protection - plant pathogenic fungi - plant pathogens - soil fungi - thanatephorus cucumeris - host plants - brassica - soil flora - resistance - edaphic factors - applied research - analysis - cauliflowers
    Rhizoctonia solani is een algemeen voorkomende bodemschimmel die bij diverse gewassen schade veroorzaakt. Dit pathogeen is moeilijk te bestrijden vanwege zijn goede overleving in de bodem. Bovendien kunnen geringe hoeveelheden van het pathogeen onder gunstige omstandigheden het gewas reeds ernstige schade toebrengen. De mate van schade is slecht te voorspellen. Het is gebleken dat onder bepaalde omstandigheden een hoge bodemweerbaarheid tegen Rhizoctonia kan ontstaan. Om meer inzicht te krijgen in het vóórkomen van bodemweerbaarheid en maatregelen die bodemweerbaarheid stimuleren, is hiernaar onderzoek gedaan bij R. solani AG 2-1 in bloemkool. De belangrijkste bevindingen zijn in dit artikel beschreven
    Beinvloedt mengteelt de ziektewerendheid van bodems tegen bodempathogenen?
    Hiddink, G.A. ; Termorshuizen, A.J. ; Raaijmakers, J.M. ; Bruggen, A.H.C. van - \ 2005
    Gewasbescherming 36 (2005)5. - ISSN 0166-6495 - p. 200 - 205.
    gewasbescherming - landbouwplantenteelt - cultuurmethoden - ziektepreventie - gemengde teelt - gewasmengsels - monocultuur - bodemschimmels - weerstand - bodem - bodemfactoren - grondanalyse - micro-organismen - microbiële flora - polymerase-kettingreactie - plant protection - crop husbandry - cultural methods - disease prevention - mixed cropping - crop mixtures - monoculture - soil fungi - resistance - soil - edaphic factors - soil analysis - microorganisms - microbial flora - polymerase chain reaction
    Mengteelten worden veelal beschouwd als stabiele teeltsystemen met een grotere oogstzekerheid dan monoculturen en minder schade door pathogenen. Uit kasexperimenten waarin de ziektewerendheid tegen drie bodempathogenen werd bepaald van grond afkomstig van een mono- of mengteelt bleek dat de ziektewering niet werd verhoogd door de toepassing van een mengteelt in het veld. De ziektewerendheid van de bodem bleek meer afhankelijk van het gewas dat erop geteeld werd, waarbij de teelt van gerst de meest ziektewerende grond bleek op te leveren. Nitraat- en ammoniumconcentraties van de grond waren niet gecorreleerd met de ziektewerendheid. Ook blijkt dat mengteelt niet of in slechts geringe mate een correlatie heeft met de microbiële populatiesamenstelling buiten de rhizosfeer. Ook de microbiële activiteit in een mengteelt was niet hoger dan die van een monocultuur. Ondanks het feit dat de ziektewerendheid van grondmonsters niet werd verhoogd door het telen van een menggewas heeft de teeltwijze wel positieve effecten zoals een hogere opbrengst aan organische stof en minder problemen met ziekten en onkruiden in de geteelde menggewassen zelf
    3.3.2 Verbetering van bodemweerstand door middel van biotische en abiotische teeltmaatregelen: voordracht 4e Gewasbeschermingsmanifestatie 'Is het al tijd om te oogsten?'
    Korthals, G.W. ; Visser, J.H.M. ; Molendijk, L.P.G. - \ 2005
    Gewasbescherming 36 (2005)sup. - ISSN 0166-6495 - p. 42S - 43S.
    gewasbescherming - geïntegreerde bestrijding - bodemfactoren - bodemeigenschappen - ziektebestrijdende teeltmaatregelen - plant protection - integrated control - edaphic factors - soil properties - cultural control
    Beschrijving van het project "geïntegreerde en biologische beheersingsmaatregelen" binnen gewasbeschermingsprogramma 397-IV. In dit project zijn verschillende factoren bijeengebracht om de natuurlijke weerbaarheid van het systeem te beïnvloeden: biologische grondontsmetting, de teelt van afrikaantjes, compost, chitine en combinaties hiervan
    Productiviteit van korte vegetaties en beperkende factoren in relatie tot voedselrijkdom en vochttoestand van natuurterreinen; basisonderzoek voor ecologische nutriëntenmodellen
    Kemmers, R.H. ; Delft, S.P.J. van; Jansen, P.C. - \ 2001
    Wageningen : Alterra (Alterra-rapport 257) - 117
    vegetatie - bodemfactoren - hydrologische factoren - voedingsstoffen - productiviteit - modellen - voedingsstoffenbeschikbaarheid - bodemchemie - nederland - ecohydrologie - natuurgebieden - ecologie - hydrologie - natuurterrein - nutriënten - vegetation - edaphic factors - hydrological factors - nutrients - productivity - models - nutrient availability - soil chemistry - netherlands - ecohydrology - natural areas
    Op 39 standplaatsen met uiteenlopende bodemkundige en hydrologische omstandigheden zijn bodemkundige en hydrologische analyses uitgevoerd om empirisch-correlatief onderzoek te doen naar de productiviteit van de vegetatie en de aard van de beperkend factoren. Met de verkregen inzichten zullen de bestaande ecologische voorspellingsmodellen, die veronderstellen dat de productiviteit volledig wordt bepaald door de stikstofhuishouding, worden aangepast. Het blijkt dat in meer dan de helft van de standplaatsen behalve stikstof ook fosfor, kalium en vocht beperkend kunnen zijn. In grondwateronafhankelijke systemen blijkt de productie voornamelijk door vochtbeschikbaarheid te worden bepaald en in mindere mate door stikstof en fosfor. In grondwaterafhankelijke systemen kan de productie grotendeels worden verklaard uit de fosforvoorraden in de bodem. De beschikbaarheid daarvan wordt gereguleerd door ijzer en het luchtgehalte van de bodem. Kalium blijkt op vrijwel alle onderzochte plaatsen een beperkende factor te zijn. Aanbevolen wordt ecologische voorspellingsmodellen uit te breiden met de simulatie van de fosfor- en kaliumhuishouding en de vochtbeschikbaarheid om de productiviteit te kunnen voorspellen.
    Desiccation tolerance of somatic embryoids = [Uitdroogtolerantie van somatische embryoiden]
    Tetteroo, F.A.A. - \ 1996
    Agricultural University. Promotor(en): C.M. Karssen; F.A. Hoekstra. - S.l. : Tetteroo - ISBN 9789054855170 - 151
    somatische embryogenese - cytogenetica - plantenveredeling - bodemfactoren - klimaatfactoren - zouttolerantie - temperatuurresistentie - kouderesistentie - droogteresistentie - daucus carota - penen - somatische celgenetica - somatic embryogenesis - cytogenetics - plant breeding - edaphic factors - climatic factors - salt tolerance - temperature resistance - cold resistance - drought resistance - daucus carota - carrots - somatic cell genetics

    This thesis describes the research performed on the subject "Desiccation tolerance in somatic embryoids". Somatic embryoids are bipolar structures formed in tissue culture, with both a shoot and a root apex, which resemble very much zygotic embryos found in seeds. Through simultaneous development of root and shoot, these embryoids can grow out into complete plantlets.

    In Chapter 2 we describe an optimized method to produce completely desiccation tolerant carrot ( Daucus carota ) embryoids. Using this method at least four different factors are important: developmental stage, abscisic acid (ABA) concentration, drying rate and rehydration mode. Embryoids may become desiccation tolerant when they have reached the torpedo stage of development. In contrast, at the earlier globular and heart stages, embryoids; never germinated after any drying treatment. Addition of at least 20 μM ABA to the pro-embryogenic masses after 7 days of culture in 2,4-dichlorophenoxyacetic acid-free B 5 medium was necessary to induce complete desiccation tolerance. Less ABA resulted in desiccation tolerance of the roots only, whereas high ABA (>80 μM) concentrations retarded developmental growth. Slow drying is essential for the acquisition of complete desiccation tolerance. Slowly dried embryoids (moisture content 0.05 g H 2 O.g 1dry weight) germinated for 100%. However, rapidly dried ones germinated for only 0-30%. Initially viable dry embryoids may suffer injury when they are imbibed in water without prehydration in water vapour. Hundred percent germination was reached by prehydration of the embryoids in moist air for 4 to 8 hours at 24°C before imbibition in B 5 medium. With the optimized protocol we were able to produce
    desiccation tolerant embryoids in two genotypes having completely different genetic backgrounds.

    With this manipulable protocol at hand, we have assessed damage associated with desiccation (Chapter 3). Fast drying caused loss of viability, and all K +and soluble carbohydrates leached from the embryoids within 5 min of imbibition. The phospholipid content decreased by about 20% and the free fatty acid content increased, which was not observed after slow drying. However, the extent of acyl chain unsaturation of the phospholipids was unaltered, irrespective of the drying rate. These results indicate that during rapid drying irreversible changes occur in the membranes which are associated with extensive leakage and loss of germinability. The status of membranes after 2 h of imbibition was analyzed in a freeze-fraction study and by Fourier transform infrared spectroscopy (FTIR). Rapidly dried embryoids had clusters of intramembraneous particles in their plasma membranes and the transition temperature (T m ) of isolated membranes was above room temperature. Membrane proteins were irreversibly aggregated in an extended β-sheet conformation and had a reduced proportion of α-helical structures. In contrast, the slowly dried embryoids had irregularly distributed, but nonclustered, intramembraneous particles, T m was below room temperature and the membrane proteins were not aggregated in a β-sheet conformation. We suggest that desiccation sensitivity of rapidly dried carrot embryoids is indirectly caused by an irreversible phase separation in the membranes due to deesterification of phospholipids and accumulation of free fatty acids.

    In Chapter 4 and 5 we have studied the role of the endogenous soluble carbohydrates during acquisition of desiccation tolerance. For carrot embryoids we demonstrated an apparent minimum requirement of umbelliferose plus sucrose for surviving severe dehydration, suggesting that these sugars play an important role in anhydrobiosis. We show with FT-IR spectroscopy, that both sucrose and umbelliferose depress the transition temperature (T m ) of dry liposomal membranes, which is evidence for their interaction with the phospholipid polar headgroups. Furthermore, both sugars prevent leakage from dry liposomes during drying and subsequent rehydration. We interpret this in the sense that both sugars are able to form a stable glass in the dry state. Fructose and glucose were lacking in dry viable embryoids. In the light of the plasticizing effect of these monosaccharides on sugar glasses, a stable glassy state seems important during anhydrobiosis of carrot somatic embryoids. We show that umbelliferose can protect a protein that is desiccation sensitive.

    To characterize desiccation tolerance we studied not only membranes and carbohydrate metabolism, but also the role of repiration (Chapter 6) and DNA replication (Chapter 7). Addition of ABA to developing carrot embryoids affected respiration and carbohydrate metabolism. Non- treated embryoids had a high level of respiration expressed per gram protein and consumed almost completely their endogenous carbohydrates during the ten day culture period. In contrast, embryoids grown with either 1.9 or 38 μM ABA, had a reduced respiration rate and maintained their carbohydrate contents at 20% of the DW. Embryoids acquired complete desiccation tolerance, when they were treated with 38 /AM ABA, whereas only 65% of the embryoids survived desiccation with 1.9 μM ABA. The reduced respiration of the developing embryoids might result in reduced free radical levels after dehydration, in this way preventing a subsequent viability loss. We suggest that there is a relation between viability loss due to desiccation and respiration rate, although the latter is not the only limiting factor involved.

    Employing flow cytometry we investigated the effect of ABA addition and slow drying on DNA replication and cell cycle activity of developing carrot embryoids. DNA replication was determined as percentage of 4C nuclei. Addition of ABA did not alter DNA replication and cell cycle during embryoid development in vitro, in spite of the putative quiescent state of the torpedo- shaped embryoids. In contrast, during slow drying the nuclei were preferentially arrested in the presynthetic G 0 /G 1 -phase, and the amount of G 2 nuclei decreased. Dry zygotic carrot embryos that are completely desiccation tolerant, did not contain any G 2 nuclei. The decline of G 2 nuclei in dry somatic embryoids seems to coincide with the increase in desiccation tolerance, which is incomplete compared to zygotic embryos. Our results suggest that in order to withstand anhydrobiosis, DNA replication may be controlled by the embryoid developmental program and by slow dehydration, but not by the plant growth regulator ABA.

    Finally, we performed scanning electron microscopy studies to establish the possible changes during desiccation (Chapter 8). Cryofixation and analysis by low temperature scanning electron microscopy (LTSEM) are excellently suitable to compare the morphology of specimens having different moisture contents. Using LTSEM we examined dry and hydrated carrot zygotic embryos and compared them with fresh, rapidly dried, and slowly dried carrot somatic embryoids, also after rehydration. Rapidly dried somatic embryoids were not able to germinate, whereas approximately 100% of slowly dried embryoids germinated. Somatic embryoids always had reduced and abnormal cotyledons, mostly fused, and the surface was irregular. The surface of the dry somatic embryoids was also more wrinkled than that of zygotic embryos. No morphological differences were detected between tolerant (slowly dried) and intolerant (rapidly dried) somatic embryoids before and shortly after rehydration. However, clear morphological differences were detected after imbibition for three days. Tolerant embryoids showed clear cell expansion, whereas intolerant ones did not. It is concluded that LTSEM is a very powerful technique to study plant materials in their native state.

    Invloed van plantverdeling, zaaitijdstip en koude - tolerantie op de stikstofbenutting door mais tijdens de jeugdgroei = Influence of plant spacing sowing time and cold tolerance on nitrogen efficiency of maize during juvenil stage
    Schans, D.A. van der; Dijk, W. van; Dolstra, O. - \ 1995
    Lelystad : PAGV (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 191) - 105
    bacteriën - klimaatfactoren - kouderesistentie - oogstschade - droogteresistentie - bodemfactoren - beschadigingen door vorst - maïs - stikstof - stikstofkringloop - plantenveredeling - plantdichtheid - planttijd - rijenafstanden - zouttolerantie - bodem - zaaitijd - temperatuurresistentie - zea mays - bacteria - climatic factors - cold resistance - crop damage - drought resistance - edaphic factors - frost injury - maize - nitrogen - nitrogen cycle - plant breeding - plant density - planting date - row spacing - salt tolerance - soil - sowing date - temperature resistance - zea mays
    Zaaitijdstip van vezelhennep
    Geel, W.C.A. van; Werf, H.M.G. van de - \ 1994
    In: Jaarboek 1993-1996 : verslagen van afgesloten onderzoeksprojecten op de regionale onderzoekcentra en het PAGV. Akkerbouw Lelystad : Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond [etc.] (Publikatie / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond, Regionale Onderzoekcentra No. 70a-81A) - p. 115 - 118.
    cannabis sativa - klimaatfactoren - kouderesistentie - droogteresistentie - bodemfactoren - hennep - plantenveredeling - planttijd - zouttolerantie - zaaitijd - temperatuurresistentie - oogsttoename - oogstverliezen - opbrengsten - cannabis sativa - climatic factors - cold resistance - drought resistance - edaphic factors - hemp - plant breeding - planting date - salt tolerance - sowing date - temperature resistance - yield increases - yield losses - yields
    De invloed is nagegaan van verschillende zaaitijdstippen op de nachtvorstgevoeligheid en op de opbrengst van vezelhennep
    Drought resistance in durum wheat
    Simane, B. - \ 1993
    Agricultural University. Promotor(en): P.C. Struik, co-promotor(en): R. Rabbinge. - S.l. : Simane - ISBN 9789054851622 - 159
    plantenveredeling - bodemfactoren - klimaatfactoren - zouttolerantie - temperatuurresistentie - kouderesistentie - droogteresistentie - triticum aestivum - tarwe - hexaploïdie - plant breeding - edaphic factors - climatic factors - salt tolerance - temperature resistance - cold resistance - drought resistance - triticum aestivum - wheat - hexaploidy

    Durum wheat is widely grown as a rainfed crop in the semi-arid tropics. Its production is low and variable from season to season due to frequent drought-stress. Characterization of target environment and employing both analytical and empirical breeding approaches would speed up progress in the development of cultivars with improved adaptation to the prevailing weather conditions.

    Analysis of historical weather data and a crop growth model were used to predict the growing season and the optimum plant growth cycle in six different ecological regions of Ethiopia. The matching of crop development to the prevailing soil water availability patterns is considered as a major step towards sustainable durum wheat production.

    High yield and yield stability are equally important breeding objectives under drought conditions. The cause-effect relationships of the duration of vegetative period, the duration of grain-filling period, yield components (number of spikes/m 2, kernels/spike, kernel weight) and grain yield revealed a complex pattern of relationships. Longer grain-filling period, increased number of kernels per spike and limited tillering were found to be associated with drought- resistance.

    Increasing water use efficiency is the major focus of the dryland cropping system. The different definitions of water use efficiency are explained. Water use efficiency on the basis of grain yield proved the most valuable parameter. The ratios of water used before anthesis and after anthesis by drought-resistant and -susceptible cultivars were different.

    Relative growth rate (RGR) and its components (leaf area ratio, LAR, and net assimilation rate, NAR) changed with growth stage and moisture availability. Drought-resistant cultivars were characterized by a fast growth rate in the beginning and slow growth later. Deep rooting and a low shoot:root ratio are effective components of drought-resistance.

    Durum wheat straw is one of the major feed sources. The quality of straw varied among cultivars, but did not correlate with drought-resistance. Drought-stress considerably improved straw quality, due to reduced remobilization of assimilates.

    The research showed that there is considerable potential to improve the current low and variable durum wheat production in the semi-arid regions.

    Adaptation of barley to harsh Mediterranean environments = Aanpassing van gerst aan ongunstige Mediterrane milieu's
    Oosterom, E. van - \ 1993
    Agricultural University. Promotor(en): J.E. Parlevliet; E. Acevedo. - S.l. : Van Oosterom - ISBN 9789054850595 - 141
    plantenveredeling - bodemfactoren - klimaatfactoren - zouttolerantie - temperatuurresistentie - kouderesistentie - droogteresistentie - hordeum vulgare - gerst - midden-oosten - plant breeding - edaphic factors - climatic factors - salt tolerance - temperature resistance - cold resistance - drought resistance - hordeum vulgare - barley - middle east

    Research Objectives

    Barley is in Syria the dominant crop in areas receiving less than 300 mm annual precipitation. Grain yield is often below 1 ton ha -1, and is reduced by low temperatures in winter and terminal drought stress in spring. Variation in the timing and intensity of the stresses, however, can cause considerable fluctuations in yield between both locations and seasons. For environments where low yields are predictable, but not the stresses causing these low yields, selection for a stable yield across years and a reduced risk of no grain yield, is more important than selection for yield potential. Breeding targeted at these environments, however, is hampered by genotypex environment interactions.

    This thesis had several aims. The first was the identification of a combination of morphological and physiological traits, or a plant ideotype, related to adaptation of barley to environments where both low temperatures early in the season and high temperatures and drought during grain filling (terminal drought) are likely. A next step was assessing the effect of plant ideotype on yield in contrasting environments and the identification of the most appropriate environment to select for plant ideotype and yield under stress. These results together culminated in the development of a selection procedure for breeding programs targeted at harsh Mediterranean environments.

    Results

    Adaptation of barley to Mediterranean environments depends on the development pattern of the apex. Within a group of 36 cultivars, four contrasting development patterns were distinguished, of which two were adapted. The first pattern constituted early heading spring types: they did not have a vernalization requirement, were cold sensitive, but avoided terminal drought stress. This pattern is especially adapted to Mediterranean environments with mild winters and terminal drought, like those in Jordan and North Africa. The second pattern represented medium early heading winter types. They had a mild vernalization requirement, a very rapid development in spring and are especially adapted to Mediterranean environments where both cold winters and terminal drought are likely, e.g., those in northern Syria. Two other development patterns, late heading spring types and late heading winter types, are unadapted to Mediterranean environments, because of an inadequate avoidance of terminal drought stress: the former group had a too slow development in spring, whereas in the second group development was delayed too much by a too high vernalization requirement. The development pattern of the apex thus depended on the vernalization requirement in winter and the response to photoperiod in spring.

    To select indirectly for development pattern, morphological traits were identified, which are related to the rate of development in winter or spring. In winter, a slow development was strongly associated with a plant ideotype, which could be described by a prostrate growth habit, dark plant colour, and cold tolerance. This ideotype was characteristic of winter types. In spring, a rapid development resulted in an early heading. Selection for these traits together thus enabled selection for an appropriate development pattern. The results indicate that it is the combination of traits, rather than an individual trait, which determines adaptation of barley to Mediterranean environments.

    Plant ideotype in winter and heading date both influence yield. Cold tolerance and a prostrate growth habit and dark plant colour in winter had a positive effect on yield in low-yielding (LY) environments, but a weakly negative effect in high-yielding (HY) environments. Early heading was very important in LY environments, but of minor importance in HY environments, apparently because terminal drought stress was less important in those environments. Early heading winter types thus had the highest yield in LY environments. This was caused by a fast crop growth rate in early spring, combined with a long green leaf area duration. In addition, the yield of early heading winter types was little affected by frost, what improved yield stability. The differences between HY and LY environments, concerning the effect of plant ideotype and heading date on yield, show that HY environments are not representative of LY environments. Selection for yield in HY environments has the risk of selection for a plant ideotype which is not adapted to LY environments.

    Implications for Plant Breeding

    Yield selection in early generations is difficult, especially under harsh conditions. Based on the results presented in this thesis, a selection procedure can be proposed, where ideotype breeding and empirical yield selection complement each other. In early generations (F 3 - F 4 ), selection must focus on the identification of ideotypes which are adapted to the LY target environment. This can be done in HY environments by selection for plant ideotype in winter and heading date in spring. In later generations, the adapted material can be tested for yield in the LY target environment; in addition, selection for other desirable traits can be done. Since empirical selection for yield in LY Mediterranean environments is most efficient if selection is carried out in representative LY environments, using adapted germplasm, the proposed combination of ideotype breeding and empirical yield selection seems to be efficient: it combines a low risk of losses of adapted germplasm in early generations with a relatively efficient empirical selection in later generations.

    The proposed selection procedure is easily applicable and can be used for many crops and types of stress environments. Essential is, before yield testing, the identification of a plant ideotype which is adapted to the dominant stresses in the LY target environment. Because landraces are often adapted to the local environment, landraces may be very useful in this identification.

    IVT - veredelingsmiddag 'Lichtbenutting door siergewassen' : 22 maart 1988, IAC, Wageningen
    Hogenboom, N.G. ; Kroon, G.H. ; Heyting, J. - \ 1988
    Wageningen : IVT - 7
    klimaatfactoren - kouderesistentie - droogteresistentie - bodemfactoren - energiebehoeften - kasgewassen - sierplanten - plantenveredeling - zouttolerantie - temperatuurresistentie - climatic factors - cold resistance - drought resistance - edaphic factors - energy requirements - greenhouse crops - ornamental plants - plant breeding - salt tolerance - temperature resistance
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