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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    Effect van vruchtwisseling op Helminthosporium aantasting in maïs : pottenproef 2009
    Meier, R. ; Schepers, H.T.A.M. ; Schooten, H.A. van - \ 2009
    Lelystad : Praktijkonderzoek Plant & Omgeving, Sector AGV (PPO rapport ) - 17
    bladvlekkenziekte - helminthosporium - rotaties - maïs - maïskuilvoer - sporen - leaf spotting - helminthosporium - rotations - maize - maize silage - spores
    Bladvlekkenziekte in maïs veroorzaakt door de schimmel Helminthosporium spp., kwam tot voor kort nauwelijks voor in Nederland. In meer zuidelijke Europese landen, zoals Zuid-Duitsland, Oostenrijk en Frankrijk heerst de ziekte al langer. Schade in snijmaïs kan door massale aantasting aanzienlijk zijn wat tot uiting komt in lagere opbrengsten en lagere voederwaarde. Voor de korrelmaïs en ccm-telers betekent een aantasting reductie van de korrelopbrengst en mogelijk hogere droogkosten als gevolg van een negatief effect op het droge stof gehalte van de korrels. Een aantasting kan ook consequenties hebben voor het inkuilen en de bewaarbaarheid van snijmaïs. In 2009 is oriënterend onderzoek gestart naar het effect van vruchtwisseling op Helminthosporium aantasting. Hiertoe is in 2009 grond verzameld van maïspercelen waar in 2007 en/of 2008 maïs heeft gestaan die was aangetast door Helminthosporium. In een pottenproef is getest of er in deze grond levensvatbare sporen aanwezig waren die maïs konden aantasten.
    Overwintering van zwartvruchtrot
    Jong, P.F. de; Heijne, B. - \ 2007
    Randwijk : PPO sector Fruit (PPO rapport nr. 2007-20) - 31
    pyrus communis - peren - stemphylium vesicarium - plantenziekteverwekkende schimmels - hibernatie - sporen - infecties - nederland - pyrus communis - pears - stemphylium vesicarium - plant pathogenic fungi - hibernation - spores - infections - netherlands
    Zwartvruchtrot wordt veroorzaakt door de schimmel Stemphylium vesicarium. De geslachtelijke vorm is Pleospora allii. De schade die de ziekte kan veroorzaken is groot. Dit heeft tot gevolg dat de telers veel spuiten omdat ze hun gewas ziektevrij willen houden.
    Stemphy uitgebouwd met sporulatiemodel
    Jong, P.F. de; Boshuizen, A. - \ 2007
    De Fruitteelt 97 (2007)8. - ISSN 0016-2302 - p. 18 - 19.
    gewasbescherming - fruitteelt - peren - stemphylium vesicarium - plantenziekteverwekkende schimmels - schimmelbestrijding - fungiciden - sporulatie - sporen - modellen - plant protection - fruit growing - pears - stemphylium vesicarium - plant pathogenic fungi - fungus control - fungicides - sporulation - spores - models
    In 2006 is voor het eerst het sporulatiemodel van Stemphy voor zwartvruchtrot beproefd. Daarbij is gekeken of dit model de sporenvluchten goed voorspelde en of een bestrijding op basis van het model een gewenst resultaat op zou leveren. De eerste bevindingen zijn zeer hoopvol. Op verschillende plaatsen is ervaring opgedaan met het waarschuwingsmodel Stemphy van Bodata in de bestrijding van zwartvruchtrot. In 2006 is het eerste onderdeel hiervan, het infectiemodel, voor gebruik in de praktijk beschikbaar. Dit model wordt meegeleverd met het Mety-programma, dat door meer dan 150 fruittelers wordt gebruikt. De ervaringen met het Stemphy-model in de praktijk zijn positief
    Meeldauw in komkommer
    Gaag, D.J. van der; Dik, A.J. - \ 2004
    vruchtgroenten - komkommers - komkommerfamilie groenten - sphaerotheca - sporen - rassen (planten) - gewasbescherming - fruit vegetables - cucumbers - cucurbit vegetables - sphaerotheca - spores - varieties - plant protection
    De schimmel tast bladeren en stengels aan. Op de aangetaste delen ziet men wit schimmelpluis. Aantasting kost opbrengst. De veroorzaker van de ziekte is Sphaerotheca fusia. De schimmel kan alleen komkommerachtigen aantasten en groeit op levende plantendelen. De sporen (conidia) kunnen ongeveer een week overleven en kunnen met de wind over grote afstanden worden verspreid. Naast de vatbare rassen zijn er rassen met een redelijk niveau van partiële resistentie en rassen met een hoog niveau van partiële resistentie.
    Splash : the dispersal of fungal plant pathogens in rain events
    Pielaat, A. - \ 2000
    Agricultural University. Promotor(en): M.J. Jeger; F. van den Bosch. - S.l. : S.n. - ISBN 9789058082121 - 116
    plantenziekteverwekkende schimmels - sporen - pyrenopeziza brassicae - colletotrichum acutatum - verspreiding - regen - plant pathogenic fungi - spores - pyrenopeziza brassicae - colletotrichum acutatum - dispersal - rain

    Models were developed to study splash dispersal of fungal plant pathogens in space and time. The models incorporate the main mechanisms involved in splash dispersal, that is 1. A raindrop hits the thin water film on the crop surface containing spores and spores are dispersed in the splashing rain droplets, and 2. Splashed spores are redistributed in the crop and on the soil surface. A mechanistic random 'jump' model describes the stochastic processes of splash dispersal over a homogeneous surface from a point source. Numerical analysis showed the importance of ground cover and rain intensity as factors determining model output. More spores were splashed in high intensity rains and, simultaneously, more spores were removed from the system. A diffusion approximation was developed for this mechanistic model which could only be considered a reasonable approximation under certain limiting conditions.

    Based on the two-dimensional version of the mechanistic model an equation was developed for the total number of spores in the area surrounding an inoculum source over time, N(t). In addition, equations for the expected mean, E(r), and mean squared distance, E(r 2), spores travel during a rain event at a given time were developed. Observed data and model predictions showed that both N(t) and E(r 2) increased to a maximum over time and then declined due to spore removal from the system and depletion of spores at the source. Factors influencing the process could be assessed by changing parameter values.

    Upward displacement of lesions by stem extension and dispersal of fungal conidia by rain-splash are mechanisms contributing to within-crop disease spread. These mechanisms were incorporated into a model based on the interaction between winter oilseed rape and the light leaf spot pathogen ( Pyrenopeziza brassicae ) as an example. Experimental results showed that most conidia were dispersed during a 15 min duration of rainfall. The trajectory of a droplet depended on the impacted plant part, with a mean horizontal travel distance decreasing with increasing incident drop diameter and a maximum splash height which ranged from 0.3 cm when splashed from a flower up to 57 cm for a pod.

    These results were incorporated into the model. Stem extension was shown to be an important factor influencing vertical disease spread. Rain events contributed to the splash dispersal of conidia to the plant apex and resulting lesions were directed vertically by internode growth. Periods with frequent rain events in a dense crop canopy were most favorable for disease progress. The upward spread of light leaf spot on winter oilseed rape in experiments at the Institute of Arable Crops Research, Harpenden, UK, was similar to that predicted by the model. Finally, an analytical model was proposed to study the influence of crop characteristics and rain properties on the vertical spread of splashed spores. Splash dispersal was concentrated in the upper layers in a crop having a constant or increasing leaf surface area with height. The greatest splash probabilities occurred and most spores were intercepted in the layers just below the apex of a crop having a decreasing leaf surface area with height.

    Oospore populations of Peronospora viciae : quantification, germinability and survival
    Gaag, D.J. van der - \ 1997
    Agricultural University. Promotor(en): J.C. Zadoks; H.D. Frinking. - S.l. : Van der Gaag - ISBN 9789054856641 - 139
    plantenziekteverwekkende schimmels - erysiphales - meeldauw - micro-organismen - celdifferentiatie - sporen - plantenplagen - plantenziekten - epidemiologie - distributie - kieming - zaadkieming - kiemrust - plant pathogenic fungi - erysiphales - mildews - microorganisms - cell differentiation - spores - plant pests - plant diseases - epidemiology - distribution - germination - seed germination - seed dormancy

    Peronospora viciae causes downy mildew on pea, field and broad bean. Two pathogens can be distinguished, P. viciae f.sp. pisi on pea (Pisum sativum) and P. viciae f. sp. fabae on field and broad bean (Vicia faba). These pathogens form resting spores, called oospores, in their host plant tissue. The oospores infest the soil after decomposition of the surrounding plant tissue and are the means by which the pathogens survive in the absence of host plants. In the present thesis aspects of the population biology of the oospores were investigated. Numbers of oospores were determined by extraction from plant tissue or soil. A vital stain test and a germination assay were used to assess viability and germinability of oospore populations. Monoconidial isolates of the two pathogens were able to produce oospores in monoculture and thus both pathogens are homothallic. P. viciae f.sp. pisi had a minimum temperature of about 10°C for oospore production and P. viciae f.sp. fabae below 5°C Dry-stored oospores of P. viciae f.sp. pisi germinated in water and appeared independent of an exogenous chemical stimulus for germination. Germinability of these oospores increased with oospore age up to a certain point and was related to their infectivity in a bioassay. Dry-stored oospores of P. viciae f.sp. fabae did neither germinate in water nor did they infect seedlings in a bioassay. After incorporation in field soil, oospore populations of both pathogens declined rapidly, and small, probably non-random, proportions of the original oospore populations survived for more than a year. The ability of oospores of P. viciae f.sp. pisi to germinate in water declined rapidly after incorporation in soil. Low percentages of oospores extracted from soil germinated in water, but relatively high disease incidences were obtained after inoculation of pea seeds with these oospores which suggested that soilexposed oospores become dependent on a chemical stimulus for germination. Oospores of P. viciae f.sp. fabae were infective after incubation in field soil for two years.

    Use of unreduced gametes of diploid potato (Solanum tuberosum L.) for true potato seed [TPS] production through 4x-2x crosses
    Qu, D. - \ 1996
    Agricultural University. Promotor(en): E. Jacobsen, co-promotor(en): M.S. Ramanna; Z. Dewei. - S.l. : Qu - ISBN 9789054854838 - 104
    solanum tuberosum - aardappelen - zaden - zaadcontrole - sporen - plantenvermeerdering - gewassen - soorten - solanum tuberosum - potatoes - seeds - seed testing - spores - propagation - crops - species
    The thesis describes the genetic bases of 2n-pollen formation. A comparison was made of the frequencies of 2n-pollen production in a different environment using the progeny of diallel crosses between five well-known diploid clones and three clones of Solanum phureja. It was evident that this character has a complex type of inheritance; through repeated cycles of selection for 2n-pollen a four-fold increase could be achieved at population level. Through proper selection of diploid male parents it was established that 2n-pollen genotypes can be effective for transferring useful characters, like bacterial wilt resistance, in 4x-2x crosses. The progenies derived from 4x-2x, 4x-4x and 4x-selfings were compared to find the optimal breeding approach for the production of TPS varieties. There were clear indications that it was possible to breed TPS varieties directly by 4x-2x crosses. This means that the advantages of breeding at diploid level and the effective transfer of desirable Units by 2n-gametes can be used in the TPS breeding.
    Toepassing van pluggenteelt in de teelt van gezaaid bosplantsoen van Pseudotsuga menziesii en Pinus sylvestris
    Joustra, M.K. - \ 1995
    Boskoop : Proefstation voor de Boomkwekerij (Rapport / Boomteeltpraktijkonderzoek 29) - 35
    dozen - containers - nederland - houtachtige planten als sierplanten - potcultuur - plantpotten - plantenvermeerdering - onderzoek - zaden - sporen - slangen (buizen) - boxes - containers - netherlands - ornamental woody plants - pot culture - pots - propagation - research - seeds - spores - tubes
    On flowering and botanical seed production in potato (Solanum tuberosum L.)
    Almekinders, C.J.M. - \ 1995
    Agricultural University. Promotor(en): P.C. Struik. - S.l. : Almekinders - ISBN 9789054854159 - 133
    solanum tuberosum - aardappelen - zaden - sporen - plantenvermeerdering - voortplanting - solanum tuberosum - potatoes - seeds - spores - propagation - reproduction

    The use of true potato seed (TPS) as a propagule for potato tuber (Solanum tuberosum L.) production is a viable alternative to the use of seed tubers. For this technology to be successful, efficient production of high- quality botanical seed is crucial. The objectives of the research reported in this thesis were to define production practices that maximise quantity and quality of botanical seed produced, and to contribute to the understanding of above-ground development in potato.

    The first part of the study describes experiments on seed production under field conditions in three contrasting agro-ecological zones in Peru. Seed production is described as a function of number of flowers produced, berry set and number of seeds produced per berry. Hundred-seed weight is used as seed-quality parameter. In the second part of the thesis, flower production is analysed as a function of inflorescence production, number of flower primordia initiated per inflorescence and flower primordia survival.

    The results of the field experiments indicated that generally, later-produced inflorescences on a shoot or in a field, and later-produced flowers in an inflorescence have a lower berry set and produce fewer and smaller seeds per flower. The effect of the position of the flower in the inflorescence does not affect seed size in all cultivars. Hundred-seed weight of production from primary inflorescences was increased when later-produced inflorescences were not used for seed production, but this could not compensate for the reduction of seed yield. Increasing plant density reduced the number of inflorescences per shoot and the number of flowers per inflorescence. Flower production per m2 increased with plant density in two of the three cultivars used. Berry set, number of seeds per berry and 100-seed weight were reduced when comparing flowers at similar positions on the shoot. However, because increasing plant density shifted the flower production from later- to earlier- formed flowers, the effect on average berry set, number of seeds per berry and seed size of the total seed production was relatively small. The effect of plant density on seed production was largely determined by the effect on flower production. Artificial extension of the photoperiod and interruption of the night with incandescent light increased the flower production under warm tropical conditions. This effect was principally a result of an increased inflorescence production. Photoperiod treatments did not affect the seed production per flower.

    Experiments in controlled conditions showed that increasing photoperiod and temperature increased the production of inflorescence positions per shoot, number of flower primordia per inflorescence and flower primordia survival in the temperature range of 15-25 °C (24-h average). Shoot development and flowering in potato were quantified as functions of rates and durations of leaf and flower primordia initiation, and of stem production. Effects of increasing temperature and photoperiods on shoot development and flowering were a result of increasing thermal durations of stem production, and leaf and flower primordia production of individual stems. The effects on individual stems were, however, small compared to the effects on stem and inflorescence production.

    Conclusions from the study for practical TPS production are that the last produced flowers in a field have a strongly reduced potential for seed production and that seed production can be best increased by increasing flower production through longer photoperiods and higher temperatures.

    Op weg naar homozygote planten uit microsporen van bolgewassen : eindverslag van het project "In vitro selectie met behulp van microsporen bij bolgewassen"
    Bulk, R.W. van den; Vries-van Hulten, H.P.J. de; Dons, J.J.M. - \ 1994
    Wageningen : CPRO-DLO - 19
    embryokweek - embryozak - bloembollen - stuifmeel - sporen - weefselkweek - tulipa - lilium - in vitro selectie - embryo culture - embryo sac - ornamental bulbs - pollen - spores - tissue culture - tulipa - lilium - in vitro selection
    Revision of Ancylobotrys Pierre. Series of Apocynaceae XXXVII.
    Vonk, G.J.A. ; Leeuwenberg, A.J.M. ; Haegens, R.M.A.P. - \ 1994
    In: Series of revisions of Apocynaceae XXXVII, XXXVIII and pollination of Apocynaceae Wageningen : Agricultural University - ISBN 9789067543613 - 81
    apocynaceae - taxonomische revisies - bestuiving - embryozak - sporen - stuifmeel - apocynaceae - taxonomic revisions - pollination - embryo sac - spores - pollen
    The utilization of true potato seed (TPS) as an alternative method of potato production
    Tuku, B.T. - \ 1994
    Agricultural University. Promotor(en): P.C. Struik; H. Kidanemariam. - S.l. : Tuku - ISBN 9789054852537 - 131
    zaden - sporen - plantenvermeerdering - solanum tuberosum - aardappelen - zaailingcultuur - zaaibedden - ethiopië - seeds - spores - propagation - solanum tuberosum - potatoes - seedling culture - seedbeds - ethiopia

    Potato is grown as a rainfed and irrigated crop in the cooler highlands and mid-altitude regions of the tropics. Its productivity is very low mainly due to unavailability of healthy and sufficient amount of seed potatoes to the farmers. The utilization of true potato seed (TPS) can be considered as an alternative method to produce potatoes, thereby alleviating the problems associated with seed potatoes.

    The first aim of the research report in this thesis was to study problems related with poor TPS germination. The second aim was to determine the best growing season to grow TPS for seedling tuber production. The third aim was to develop appropriate seed bed management practices for maximum seedling tuber production.

    Increasing nitrogen fertilization to the mother plant enhanced the rate of gerniination of the TPS of the open pollinated progeny (AL 624) and reduced that of the hybrid progeny ( AL 624 x CIP 378371.5) without affecting the final germination percentages (FGP) of both progenies.

    TPS dormancy was effectively broken by soaking in 1000-1500 ppm GA 3 for 8 hrs. Treating TPS with water can also break dormancy and maintain about 70 % germination. The latter may be considered as a cheap, readiliy available and practical alternative method of breaking TPS dormancy under farmers' condition.

    The field and nursery experiments indicated that seedling tuber yields are very low during the rain season due to late blight ( Phytophthora infestans ) pressure, shorter sunshine hrs and a shorter growing season than the dry season.

    Based on the nursery results, in the central highlands of Ethiopia, dry season production of seedling tubers in a seed bed substrate mix of 50 % forest soil and 50 % manure, and 40 - 80 g N per m 2bed were found to be suitable for the production of a maximum number of seedling tubers by direct sowing methods.

    Manipulation of seedling population in a seed bed is one method of producing a maximum number of usable seedling tubers. The results revealed that a plant density of 100 plants per m 2seed bed was optimal for the production of a maximum number of up to 1200 seedling tubers or a total tuber weight of 29 kg per m 2without hampering management operations such as weeding, fertilization and billing up.

    The research results showed that there is a considerable potential of alleviating the problems of seed potatoes by improving the TPS germination quality, seed bed production of seedling tubers and using them as seed potato source for subsequent growing seasons.

    The Tapetum: cytology, function, biochemistry and evolution
    Hesse, M. ; Pacini, E. ; Willemse, M.T.M. - \ 1993
    Berlin : Springer Verlag - ISBN 9783211824863 - 152
    biochemie - embryozak - metabolisme - stuifmeel - polymeren - sporen - celfysiologie - biochemistry - embryo sac - metabolism - pollen - polymers - spores - cell physiology
    The anther tapetum, present in all land plants, is a highly specialized, transient tissue surrounding the (micro-)spores and/or pollen grains during their development.Any tapetum malfunction causes male sterility. The exact knowledge of tapetum form and function therefore is indispensable not only for basic research, but also and especially in plant breeding and plant genetics.In fourteen contributions by reknown experts, a comprehensive account of the various characters and functions of the tapetum is provided, covering the areas of cytology, cytophysiology, biochemistry, tapetum development and function.
    Pollen tube - pistil interaction and fertilization in Lilium longiflorum
    Janson, J. - \ 1992
    Agricultural University. Promotor(en): M.T.M. Willemse. - S.l. : Janson - 145
    liliaceae - bestuiving - embryozak - sporen - stuifmeel - lilium longiflorum - liliaceae - pollination - embryo sac - spores - pollen - lilium longiflorum

    In this thesis the interaction between pollen tube growth and the pistil with the subsequent fertilization was studied both in intact flowers and after different flower manipulations and in vitro pollination. light and electron microscopy and electrophoresis were used.

    To achieve interspecific crosses in lily the cut-style pollination, in which the style is cut off just above the ovary and pollen grains are applied at the cut surface, is used. Just a few ovules are penetrated by a pollen tube. In an intraspecific compatible combination the penetration percentage of the ovules after cut-style pollination is however low as well. Complications occur in the interaction between the pollen tube and the ovule. It might be that the ovules lack an enhancement which takes place during pollination or germination at the stigma or during pollen tube growth in the style, which is absent after cut-style pollination.

    In chapter 1 a review is given of compatible, incompatible and interspecific pollen tube growth in Lilium, the guidance of the pollen tube and other aspects of the interactions between the pollen tubes and the pistil. Following this chapter interactions are first studied in an intact system of Lilium longiflorum .

    In chapter 2 the exudate production in the pistil, embryo sac development and pollen tube growth in L. longiflorum is studied and related to flower bud length and flowering stage. The exudate production on the stigma and in the style starts before the bud opens, as determined by cryo scanning electron microscopy. Just underneath the stigma the exudate first accumulates at the top of each secretory cell, followed by a merging of those accumulations as exudate production proceeds.

    After germination the pollen tubes grow across the stigma and enter the style in between the three stigma lobes. This growth over the stigma seems at least at first not directed. In the style the pollen tubes grow straight downward at a constant speed and are covered by exudate. As the pollen tube bundle reaches the ovary, the secretory pathway and thus also the pollen tube bundle is divided into three ovarian cavities. Hereby they spread out, but their growth is restricted to the area with secretory cells. The secretory cells covering the placenta are similar to those present in the stylar canal, although their surface shape is more spherical rather than elongated as in the style. The transfer wall of the placenta] cell is originating from fusing Golgi vesicles but the endoplasmic reticulum (ER) seems to have an important role as well.

    In between the two rows of ovules in one ovarian cavity a pollen tube bundle is formed in the exudate produced by the placental cells. After neglecting the first few ovules the pollen tubes bend from this bundle in between the ovules and grow towards the micropylar side. There they bend again to stay close to the secretory cells. At anthesis a part of the embryo sacs are in their seven-nucleate and six-cellate (the cell walls in the embryo sac were hard to detect after clearing) stage, i.e. mature. Penetration of the pollen tubes into the micropyle has only been observed in these ovules.

    About 8 days before anthesis exudate is observed in a flower bud. Pollen tube growth in the style is possible from seven days before anthesis. The pollen tube growth is then however strongly retarded compared with the pollen tube growth in a flower at anthesis. It seems that some pollen tubes are not covered by an exudate layer. Newly appearing pollen tube tips have a tendency to grow close to the secretory cells, resulting in a growth between these cells and preceding pollen tubes. If there is still little exudate produced it results in a lifting up of the pollen tubes, out of the exudate.

    The development of the embryo sacs in sector two (sector one is at the top and four is at the basis of the ovary) is ahead of the embryo sacs in the other sectors of the ovary. Pollination or pollen tube growth did not influence the development of the embryo sacs. When the pollen tubes formed after pollination of a flower bud finally reach the ovary, a part of the ovules have matured. From four days before till seven days after anthesis, pollination results in penetration of the ovules. The protein pattern of the ovules observed after electrophoresis did not show a consequent change in the period from anthesis till 9 days after anthesis or 7 days after pollination.

    In chapter 3 the ultrastructure of the embryo sac, the nucellus and parts of the micropyle of L.longiflorum is studied both before and after pollination. Before pollen tube penetration the three cells of the egg apparatus cannot be distinguished, neither in structure nor in their position. No filiform apparatus was detected, no degeneration of a synergid occurs without pollen tube penetration. The polar nuclei in the central cell do not fuse until fertilization. The metabolic activity of the cells of the egg apparatus and the central cell seems low. The nucleus of the most chalazal of the two antipodals has an irregular shape and in some embryo sacs a third antipodal cell, small in size and without a nucleus, is present. Pollen tube growth does not induce changes in the embryo sac.

    When the pollen tube arrives at the nucellus the cuticle surrounding this nucellus is lifted up. Enzymatic digestion of the cell wall of the at this place one cell layer thick nucellus has to take place to create a pathway for the pollen tube to enter the embryo sac. After entering the embryo sac, the pollen tube grows along the inside of the nucellus and finally penetrates one of the three cells of the egg apparatus, now distinguished as the degenerated synergid. Shortly after fertilization two enucleate cytoplasmic bodies of a different ribosome density were observed in the degenerated plasma of the synergid and the pollen tube. These structures border both the central cell, the egg cell and each other and are most likely the two empty sperm cells. The sperm nucleus in the central cell is probably transported by ER and first makes contact with the haploid polar nucleus which is, as the triploid polar nucleus, connected with ER as well. In the egg cell another process is more likely, because here strands of ER were not observed. Here the nuclei line up before fusion. The cells of the embryo sac become more metabolic active after pollen tube penetration. In this chapter an attempt is made to relate ultrastructure to function and processes.

    In chapter 4 the pollen tube growth in the ovary after cut-style pollination was observed with scanning electron microscopy. Different flower manipulations were carried out in an attempt to elucidate the interaction between the pollen tube growth and the pistil. Until the arrival of the pollen tube at the inner integument, the pollen tube growth did not show any difference between cut-style and stigmatic pollination, as studied in chapter 2. Using cut-style pollination the pollen tubes either grew past the inner integument and ignored it, or grew along but not into the micropyle or penetrated the micropyle.

    Grafting a stigma just above the ovary did not influence the penetration percentage, nor did a possible activation of the ovary induced by pollination or pollen tube growth in the style or even in the ovary itself, preceding or during cut-style, interstylar or placental pollination in a pistil. The percentage of penetration after cut-style pollination increased however when the stylar part present at the ovary was left longer.

    The presence of the ovary did not influence the pollen tube growth in the style as determined after isolation of styles from the ovary and comparing the pollen tube length.

    When pollen grains and stigmatic exudate were applied through a slit half-way down the style of an intact pistil the pollen tube growth was not influenced by a simultaneous pollination at the stigma.

    In chapter 5 placental pollination was carried out predominantly with L.longiflorum to study the interaction between the pollen tube and the placenta with ovules. The percentage of penetrated ovules is low when compared with compatible pollination at the stigma. After placental pollination the pollen tube growth between the ovules seems directed and the pollen tubes do find the inner integument. A reaction to the inner integument or the micropyle is observed, but hardly results in ovule penetration. Embryos were found, but did not develop vigorously. The similarities and differences with cut-style pollination, in which the percentage of ovule penetration is also low, are discussed. Grafting a style with pollen tubes to the placenta increased the penetration percentage obtained after placental pollination five times.

    In chapter 6 the data from chapter 2 and 3 are combined in a reproductive calendar.

    In chapter 7 the reproduction is considered as a regulated interaction process. Previous experimental results are considered as aspects of the system and are discussed in this context.

    Modelling the escape of Chondrostereum purpureum spores from a larch forest with biological control of Prunus serotina.
    Jong, M.D. de; Wagenmakers, P.S. ; Goudriaan, J. - \ 1991
    Netherlands Journal of Plant Pathology 97 (1991). - ISSN 0028-2944 - p. 55 - 61.
    celdifferentiatie - demonstratiebossen - afsterving - ziekten - bosschade - achteruitgang, bossen - bosplagen - bosbouw - micro-organismen - modellen - natuurlijke vijanden - parasitaire planten - plantenziekteverwekkende schimmels - sporen - theorie - bomen - onkruiden - larix - prunus serotina - chondrostereum purpureum - bosbescherming - experimentele bossen - bospathologie - wetenschap - cell differentiation - demonstration forests - dieback - diseases - forest damage - forest decline - forest pests - forestry - microorganisms - models - natural enemies - parasitic plants - plant pathogenic fungi - spores - theory - trees - weeds - larix - prunus serotina - chondrostereum purpureum - protection of forests - experimental forests - forest pathology - science
    Risico-analyse van gebeurtenissen die leiden tot infectie van non-target planten. Middels een theoretische benadering in de vorm van gesimuleerde spore-verspreiding binnen en buiten het bos, wordt de sporefractie berekend die zou kunnen ontsnappen uit het bos
    Inventarisatie van ziekten en plagen in veldbeemgras en Engels raaigras voor zaadproduktie in 1989
    Horeman, G.H. - \ 1990
    Lelystad etc. : PAGV [etc.] (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 119) - 29
    oogstschade - lolium - nederland - parasieten - poa - plantenvermeerdering - zaden - sporen - crop damage - lolium - netherlands - parasites - poa - propagation - seeds - spores
    Zaaizaad en pootgoedproduktie : de vermeerdering van pootaardappelen, graszaad en zaad van koolhybriden : onderwijselement : (F750 - 111)
    Mol, L. - \ 1990
    Wageningen : LU - 76
    koolsoorten - plantenvermeerdering - pootaardappelen - zaden - sporen - vegetatieve vermeerdering - voedergrassen - cabbages - propagation - seed potatoes - seeds - spores - vegetative propagation - fodder grasses
    Overzaaien van suikerbieten : een verslag van proeven in de jaren 1985 t/m 1987 in het kader van het project 56.8.12 Automatisering van de teeltbegeleiding bij suikerbieten
    Smit, A.L. - \ 1989
    Lelystad : PAGV (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 91) - 78
    beta vulgaris - nederland - beplanten - plantenvermeerdering - zaden - zaaien - sporen - suikerbieten - verplanten - beta vulgaris - netherlands - planting - propagation - seeds - sowing - spores - sugarbeet - transplanting
    Germination and appressorium formation of wheat leaf rust on susceptible, partially resistant and resistant wheat seedlings and on seedlings of other Gramineae species.
    Jacobs, Th. - \ 1989
    Netherlands Journal of Plant Pathology 95 (1989). - ISSN 0028-2944 - p. 65 - 71.
    triticum aestivum - tarwe - hexaploïdie - plantenziekteverwekkende schimmels - pucciniales - puccinia - hordeum vulgare - gerst - aegilops - sporen - plantenveredeling - ziekteresistentie - plaagresistentie - parasitisme - triticum aestivum - wheat - hexaploidy - plant pathogenic fungi - pucciniales - puccinia - hordeum vulgare - barley - aegilops - spores - plant breeding - disease resistance - pest resistance - parasitism
    Inzaai van enkele kruiden in soortenarm grasland bij verschillende inzaaifrequenties
    Altena, H.J. - \ 1988
    Wageningen : CABO (CABO - verslag nr. 77) - 14
    graslanden - hooiland - nederland - weiden - plantengemeenschappen - plantenvermeerdering - zaden - sporen - graslanden, gematigde streken - gematigde klimaatzones - grasslands - meadows - netherlands - pastures - plant communities - propagation - seeds - spores - temperate grasslands - temperate zones
    Bij het beheer van graslanden en wegbermen blijkt het vaak lang te duren, voordat zich nieuwe soorten in de vegetatie vestigen. De aanvoer van zaden van nieuwe soorten is een belangrijke beperkende factor. Inzaai van nieuwe soorten is een mogelijkheid om op korte termijn tot een groter soortenrijkdom te komen. In hoeverre hierbij spreiding in het tijdstip van inzaaien van invloed is op het kiemings- en vestigingssucces is bij gewoon biggekruid, margriet, smalle weegbree, echt knoopkruid en duizendblad op zandgrond en op komkleigrond onderzocht in de periode 1984-'87
    Perspectief van lupine voor zaadwinning
    Schroeder, J. - \ 1987
    In: Jaarboek 1987-1992 : verslagen van in 1987-1992 afgesloten onderzoekprojecten op Regionale Onderzoek Centra en het PAGV Lelystad : Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond (Publikatie / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond, Regionale Onderzoekcentra no. 38-64) - p. 181 - 186.
    lupinen - lupinus - plantenvermeerdering - zaden - sporen - lupins - lupinus - propagation - seeds - spores
    In 1985 en 1986 heeft een orienterend ondezoek plaatsgevonden naar de opbrengstmogelijkheden van witte lupine op zandgrond. Opbrengst en afrijping van de diverse onderzochte rassen bleven in beide jaren achter bij die van erwten en veldbonen. Dit was vooral in 1985 mede een gevolg van de slechte benutting van hoofdasbloeiwijzen. Het teelttechnisch onderzoek wordt voorlopig gestaakt
    De invloed van teeltmaatregelen bij winterkoolzaad op de zaadproduktie in Noord-Nederland
    Vreeke, S. - \ 1987
    Lelystad : Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 63) - 36
    brassica napus var. oleifera - teelt - cultuurmethoden - oogsten - nederland - plantenvermeerdering - koolzaad - zaden - sporen - brassica napus var. oleifera - cultivation - cultural methods - harvesting - netherlands - propagation - rape - seeds - spores
    Studies on germination and vigour of cabbage seeds = [Aspecten van de kieming van zaden van witte kool en savoiekool
    Liou, T.D. - \ 1987
    Agricultural University. Promotor(en): C.M. Karssen, co-promotor(en): H.L. Kraak. - S.l. : Liou - 101
    brassica oleracea - koolsoorten - karakteristieken - plantenvermeerdering - zaadcontrole - zaden - sporen - stratificatie (zaden) - brassica oleracea - cabbages - characteristics - propagation - seed testing - seeds - spores - stratification

    The effects of commercial storage of cabbage seeds on the germination of seeds and the emergence and growth of seedlings have been studied. Progressive ageing of seeds caused loss of seed vigour which resulted in poor emergence and growth of seedlings and the formation of abnormal seedlings. Loss of vigour was also observed indirectly in the controlled deterioration test (CD test) that speeds up the rate of ageing at controlled conditions. It was shown that the CD test gave the best indication of vigour loss. Low vigour seeds also differed from high vigour seeds in a more substantial loss of potassium ions during incubation in soil. Apart from seed vigour also soil conditions and other environmental factors influence the field performance that under certain atmospheric and soil conditions the best possible result is obtained.

    Pre-incubation of cabbage seeds in osmotic solution clearly showed that several aspects of seed ageing are reversible. Pretreated seeds germinated earlier and faster and produced more normal seedlings than untreated seeds. The mechanism of osmotic pretreatment was studied. It 'is unlikely that such treatment favours the accumulation of osmotic constituents. The leakage of K +was inhibited during osmotic incubation. Loss of vigour might be related to membrane damage.

    Production of conidia by Peronospora farinosa f. sp. spinaciae.
    Frinking, H.D. ; Stoel, M.C. van der - \ 1987
    Netherlands Journal of Plant Pathology 93 (1987). - ISSN 0028-2944 - p. 189 - 194.
    phytophthora - plantenziekteverwekkende schimmels - spinazie - spinacia oleracea - sporen - phytophthora - plant pathogenic fungi - spinach - spinacia oleracea - spores
    Oospore formation by Phytophthora infestans in host tissue after inoculation with isolates of opposite mating type found in The Netherlands.
    Frinking, H.D. ; Davidse, L.C. ; Limburg, H. - \ 1987
    Netherlands Journal of Plant Pathology 93 (1987). - ISSN 0028-2944 - p. 147 - 149.
    phytophthora - plantenziekteverwekkende schimmels - aardappelen - geslachtelijke voortplanting - solanum tuberosum - sporen - phytophthora - plant pathogenic fungi - potatoes - sexual reproduction - solanum tuberosum - spores
    Het drogen van graszaad op het landbouwbedrijf
    Jansen, J. - \ 1981
    Wageningen : IBVL (Publikatie / Instituut voor Bewaring en Verwerking van Landbouwprodukten 335) - 8
    drogen - plantenvermeerdering - zaden - sporen - voedergrassen - drying - propagation - seeds - spores - fodder grasses
    Overbrenging van Verticillium dahliae door spinazie-zaad
    Anonymous, - \ 1979
    Wageningen : Pudoc (Literatuurlijst / Centrum voor Landbouwpublikaties en Landbouwdocumentatie no. 4237)
    bibliografieën - distributie - epidemiologie - plantenziekten - afwijkingen, planten - plantenziekteverwekkende schimmels - plantenziektekunde - plantenplagen - gewasbescherming - plantenvermeerdering - zaden - spinazie - spinacia oleracea - sporen - bibliographies - distribution - epidemiology - plant diseases - plant disorders - plant pathogenic fungi - plant pathology - plant pests - plant protection - propagation - seeds - spinach - spinacia oleracea - spores
    Verslag van een studiereis naar Engeland, 19 - 23 december 1977
    Roelofsen, H.J. - \ 1978
    Wageningen : IVT (Rapport / Instituut voor de Veredeling van Tuinbouwgewassen no. 140) - 9
    groot-brittannië - plantenvermeerdering - zaden - sporen - opslag - great britain - propagation - seeds - spores - storage
    Invloed van herinzaai en stikstof op de opbrengst en botanische samenstelling van grasland : tweede verslag van een proef te Gilze van 1971 - 1974
    Woldering, J.J. - \ 1975
    Lelystad : Proefstation voor de Rundveehouderij (Rapport / Proefstation voor de Rundveehouderij 35) - 21
    zaden - sporen - plantenvermeerdering - graslanden - seeds - spores - propagation - grasslands
    In 1962 werd op een perceel. zandbouwland te Gilze (N.B.) een graslandproefveld aangelegd om de invloed van herinzaaien op de opbrengst en botanische samenstelling na te gaan bij twee stikstofniveaus. Een verslag van het onderzoek in de periode 1963 tot en met 1970 is gepubliceerd door G. Krist rapport nr. 7, oktober 1972 van het Proefstation voor de Rundveehouderij. Na 1970 is deze proef voortgezet tot begin 1974. Over deze periode worden de resultaten in dit verslag weergegeven
    Ecological aspects of seed health testing
    Limonard, T. - \ 1968
    Wageningen University. Promotor(en): A.J.P. Oort. - Wageningen : International Seed Testing Association - 167
    zaden - gezondheid - sporen - plantenvermeerdering - plantenziekteverwekkende schimmels - plantenziekten - plantenplagen - gewasbescherming - plantenziektekunde - afwijkingen, planten - methodologie - biologische technieken - experimenten - uitrusting - seeds - health - spores - propagation - plant pathogenic fungi - plant diseases - plant pests - plant protection - plant pathology - plant disorders - methodology - biological techniques - experiments - equipment

    The purpose of this study was to investigate the factors affecting the outcome of incubation methods used to test seeds for the presence of fungal pathogens. The reason for starting such an investigation was the poor reproducibility of the results of those methods.

    Chapter 3 starts with the observation that for a number of infections lower percentages are found on blotters with a relatively high moisture content than on blotters with a lower moisture content. This so-called 'wet blotter effect' (WBE) was found to be related to the speed of water uptake by the seeds; if the water uptake is relatively slow the effect does not show, whereas in the case of more rapid water absorption the effect can be noted. If the rate of water uptake of seeds without WBE was increased by presoaking them in water, a similar decrease was noted ('soak effect' or SE). WBE and SE could both be nullified by the addition of antibacterial antibiotics, and so were attributed to antagonism by saprophytic seed-borne bacteria.

    Factors stimulating bacterial development (higher temperature and pH, addition of nutrients or bacteria) were found to increase WBE and SE; factors stimulating fungi more than bacteria decreased or eliminated it. If one of both groups (bacteria or fungi) obtains the initial lead it will dominate and reduce the expression of the other group. Elimination of bacterial antagonism results in higher percentages of both pathogenic and saprohytic fungi found. The use of antibiotics eliminates bacterial antagonism as a source of variation.

    Bacterial antagonism in the agar method is often less important due to low pH of the medium. This offers an explanation for the higher agar than blotter percentages found for such an infection as Botrytis cinerea in flax seed. The hypochlorite pretreatment customary for the testing of most seeds by the agar method also restricts bacterial antagonism. Bacterial antagonism in agar tests may not only lower infection percentages found but also change the colony appearance. The addition of a small quantity of an antibiotic to the agar medium eliminates it altogether.

    The importance of the WBE and SE may vary with the sample, due to differences in the bacterial flora of the seeds. Plating soaked seeds on agar media yields hardly any pathogen, but agar media with antibiotics which were routinely used in all further work, more or less nullify the previous SE. Soaking in terramycin solution often gave increased percentages of the pathogen.

    The same factors stimulating bacterial antagonism in blotter tests also favour it in sand and soil.

    Chapter 4 starts with the observation that in case of Phoma valerianellae infection of corn salad seeds blotter tests with 2,4-D gave remarkably higher percentages than normal blotter tests. This led to the realization of the importance of the factor 'host vigour' in incubation methods. Various other treatments such as water soak, exhaustion, mutilation and freezing gave similar results. The reduction (2,4-D), elimination (freezing) or circumvention (agar method) of host vigour often lead to higher percentages being found for seed-borne infections. It also offers an explanation for the difference between blotter and agar test results for some infections. Reduction of the host vigour causes a shift from symptoms of the disease to signs of the pathogen to be looked for at inspection.

    The freezing of pre-incubated seed followed by a post-freezing incubation period (freezing method) was found to be promising for a number of infections. For some infections (e.g. Helminthosporium spp.) it simplifies inspection, no seedling structures being produced. Provided bacterial development is checked by means of antibiotics, fungi grow easier and more abundantly, probably due to increased leachage of nutrients from seeds. Fungal infections can therefore be more easily recognized and identified, and higher infection percentages may be found. Some seeds which are rich in easily available nutrients (e.g. wheat) must be protected from air-borne contamination. In the freezing method the trays with paper can be replaced by plastic sheets with depressions filled with liquid (containing e.g. antibiotics) for the seeds.

    In chapter 5 it is observed that interfungal antagonism becomes more prominent when bacterial antagonism and host vigour are either not important or have been eliminated. It is consequently especially a problem in the agar method. Interfungal antagonism is influenced by incubation conditions, e.g. temperature. Its reduction by the use of hypochlorite pretreatment is rather non-selective, eliminating also part of the pathogen, although it may be all right for such deep-seated infections as Ascochyta spp. in pea and Phoma betae in beet seeds.

    More selective is the 'dry heat' pretreatment advocated by MALONE (1962) for H.avenae in oat seeds tested by the agar method. Its use was extended to other Helminthosporium spp. in oat and barley seeds but has the disadvantage of increased Mucor development in subsequent agar tests. In blotter tests with dry heat pretreatment Mucor presented no problem, but the results were not superior to those of the freezing method.

    A highly selective method is the use of peptone-PCNB agar for Fusarium spp. In this method neither bacterial and fungal antagonism nor host vigour play a role, so that very high infection percentages may be obtained. Tests carried out by this method are easy to prepare and to inspect.

    Another way to combat interfungal antagonism is the use of growth-restricting agents, such as oxgall, in agar media. This offered good prospects for the slow growing Septoria nodorum in wheat seed, which is otherwise easily suppressed by other fungi. The use of oxgall eliminates the need of surface disinfection which is an advantage as light infections of S.nodorum can be important.

    Chapter 6 deals with measurement of the severity of infection. Very light Fusarium infections of single seeds may be considered to be of little consequence. Their elimination by hypochlorite pretreatment can therefore be accepted and may be used as a correction of the very sensitive peptone-PCNB agar method. This led to considerations on the importance of inoculum potential and threshold level of infection. Seed health data are usually given in terms of percentage of infected seeds. Possible ways to correct them for inoculum potential were indicated, such as the use of pretreatments of standardized strength. This could perhaps compensate for the elimination of such factors as antagonism and host vigour.

    Chapter 7 describes experiments in which a large number of wheat seed samples containing Fusarium spp. and Septoria nodorum were tested in various ways. The results were then compared and correlation coefficients between them were computed. Although the latter were low, they were generally significant. The correlations of germination capacity with soil emergence decreased with temperature due to the presence of F. nivale. This pathogen only reduces emergence at lower temperatures, being of no consequence at higher ones. S.nodorum did not significantly reduce emergence in the samples used, although at lower temperatures it caused more abnormal seedlings to be produced. S. nodorum was always highly correlated with coleoptyle lesions.

    The blotter test for Fusarium spp. was shown to be very unreliable. The symptoms are hard to judge so that errors of judgment are easily made the presence of the different Fusarium spp. is not equally well indicated and other fungi e.g. S. nodorum may interfere by producing the same symptoms. The blotter test for S.nodorum is only good for a number of cultivars that produce the characteristic protuberance symptoms. For other cultivars the symptoms to be used are highly unreliable, especially if Fusarium spp. are present, which usually is the case. The agar method is therefore to be preferred, preferably without surface disinfection, but with e.g, oxgall added to the medium.

    It is suggested that due to the complex nature of the factors involved, which are moreover unpredictable the usefulness of correlation coefficients for seed-borne infections is very limited. Their main use may be in the comparison of various methods with seed ling performance in conditioned soil tests.

    In chapter 8 it is concluded from the preceding that the incubation conditions applied in seed health testsdo not only affect the expression of the pathogen in a direct way. They also affect the pathogen indirectly via the seed biotope (seed microflora and host seed or seedling). The seed biotope varies with the sample so that the most important source of variation is presented by the ecology of the germinating seed itself. Elimination and circumvention of these biotic factors, which also decreases the chances of errors of judgment, seem to offer the best prospects for the development of simple, cheap, fast and reproducible methods.

    Application of correction factors for inoculum potential may be important for a number of infections (e.g. Fusarium spp. in cereal seeds). Tolerances if used may be regarded as a correction for local agricultural conditions and should be based on the methods used for testing.

    De thermoresistentie van thermofiele sporenvormers bij verlaagde pH
    Juengst, H.F. - \ 1968
    Wageningen : Sprenger Instituut (Rapport / Sprenger Instituut no. 1635) - 55
    micro-organismen - celdifferentiatie - sporen - voedselmicrobiologie - ph - zuurgraad - waterstofionen - microorganisms - cell differentiation - spores - food microbiology - ph - acidity - hydrogen ions
    De zaadwinning van voederwikke : Proefveldresultaten in 1959, 1960 en 1961
    Kamp, T.C. van der - \ 1965
    Wageningen : [s.n.] (Mededeling / Proefstation voor de akker- en weidebouw, Wageningen no. 110) - 37
    nederland - plantenvermeerdering - zaden - sporen - vicia - netherlands - propagation - seeds - spores - vicia
    Zaaizaad en pootgoed in de Nederlandse landbouw
    Addens, N.H.H. - \ 1952
    Wageningen University. Promotor(en): W.J. Dewez. - Wageningen : Veenman - 282
    zaden - sporen - plantenvermeerdering - vegetatieve vermeerdering - zaadcontrole - nederland - pootaardappelen - aardappelen - seeds - spores - propagation - vegetative propagation - seed testing - netherlands - seed potatoes - potatoes
    The annual input for seed was about 7.5 % of the total cost of the crop; selection and testing of new varieties costed only 0. 1 %; plant breeding increased the return from field crops by at least + % annually. After an introduction to the theme of which these are some of the main results there are 8 further chapters, dealing with: standards for seed; use and handling of seed; purchase of seed by farmers; local and regional seed exhibitions; introduction of new crops and varieties; field inspection of crops for seed; the Plant Breeders' Decree (1941); the marketing of Dutch seeds and seed potatoes. Changes in the testing of seeds and seed potatoes are sketched for the last three quarters of a century. Measures, which Dutch breeders, seed-growers, seed-merchants and the government were taking to improve varieties, seeds and seed potatoes are reviewed and discussed.

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