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.

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    Robustness and accuracy of Maxent niche modelling for Lactuca species distributions in light of collecting expeditions
    Cobben, M.M.P. ; Treuren, R. van; Castaneda-Alvarez, N.P. ; Khoury, C.K. ; Kik, C. ; Hintum, T.J.L. van - \ 2015
    Plant genetic resources: characterization and utilization 13 (2015)2. - ISSN 1479-2621 - p. 153 - 161.
    genetic-resources - absence data - prediction - asteraceae - lettuce
    Niche modelling software can be used to assess the probability of detecting a population of a plant species at a certain location. In this study, we used the distribution of the wild relatives of lettuce (Lactuca spp.) to investigate the applicability of Maxent species distribution models for collecting missions. Geographic origin data of genebank and herbarium specimens and climatic data of the origin locations were used as input. For Lactuca saligna, we varied the input data by omitting the specimens from different parts of the known distribution area to assess the robustness of the predicted distributions. Furthermore, we examined the accuracy of the modelling by comparing the predicted probabilities of population presence against recent expedition data for the endemic Lactuca georgica and the cosmopolitan Lactuca serriola. We found Maxent to be quite robust in its predictions, although its usefulness was higher for endemic taxa than for more widespread species. The exclusion of occurrence data from the perceived range margins of the species can result in important information about local adaptation to distinct climatic conditions. We discuss the potential for enhanced use of Maxent in germplasm collecting planning.
    Toxicity of Pyrrolizidine Alkaloids to Spodoptera exigua Using Insect Cell Lines and Injection Bioassays
    Nuringtyas, T.R. ; Verpoorte, R. ; Klinkhamer, P.G.L. ; Oers, M.M. van; Leiss, K.A. - \ 2014
    Journal of Chemical Ecology 40 (2014)6. - ISSN 0098-0331 - p. 609 - 616.
    tertiary amine - n-oxides - performance - herbivores - resistance - asteraceae - vulgaris - hybrids - plants
    Pyrrolizidine alkaloids (PAs) are feeding deterrents and toxic compounds to generalist herbivores. Among the PAs of Jacobaea vulgaris Gaertn, jacobine and erucifoline are the most effective against insect herbivores as indicated by correlative studies. Because little is known about the effect of jacobine and erucifoline as individual PAs, we isolated these compounds from their respective Jacobaea chemotypes. These PAs and other commercially available senecionine-like PAs, including senecionine, seneciphylline, retrorsine, and senkirkine, were tested as free base and N-oxide forms at a range of 0–70 ppm. Feeding bioassays using live insects are closer to the natural pattern but require relatively large amounts of test compounds. We, therefore, compared the toxicity of PAs using both Spodoptera exigua cell line and larval injection bioassays. Both bioassays led to similar results in the order of PA toxicity, indicating that the cell lines are a valuable tool for a first toxicity screen. Testing individual PAs, jacobine and erucifoline were the most toxic PAs, suggesting their major role in plant defense against generalist herbivores. Senkirkine and seneciphylline were less toxic than jacobine and erucifoline but more toxic than retrorsine. Senecionine was not toxic at the tested concentrations. For all toxic PAs, the free base form was more toxic than the N-oxide form. Our results demonstrate that structural variation of PAs influences their effectiveness in plant defense.
    Distribution of downy mildew (Bremia Lactucae Regel) resistances in a genebank collection of lettuce and its wild relatives
    Treuren, R. van; Arend, A.J.M. van der; Schut, J.W. - \ 2013
    Plant genetic resources: characterization and utilization 11 (2013)1. - ISSN 1479-2621 - p. 15 - 25.
    genetic-resources - diversity - serriola - asteraceae - population - cultivars - cluster
    Genebanks serve as a rich source of diversity that can be exploited for crop improvement. However, large numbers of accessions usually have to be evaluated to find material with the characters of interest, and therefore, enhanced trait information can facilitate the more efficient selection of accessions by users. In this study, we report on the distribution of resistances to 28 races of downy mildew among 1223 genebank accessions of cultivated lettuce (Lactuca sativa L.) and 14 related wild species. Due to modern plant breeding, the overall level of resistance of cultivars released after 1950 appears to have increased two- to three-fold compared with varieties from earlier periods. Although fully resistant reactions could be observed among the accessions of cultivated lettuce for each of the 28 investigated races, the resistance probability was more than two-fold higher on average for accessions from the wild gene pool. In general, species of the primary gene pool appeared less resistant than those of the secondary or tertiary gene pool. Probabilities for examined Lactuca species ranged from 0.29 for L. serriola to 1.00 for L. perennis compared with 0.19 for cultivated lettuce, with lower overall resistance probabilities observed only for L. altaica, L. dregeana and L. tenerrima. For L. serriola, the closest relative of cultivated lettuce and the wild species with the highest number of examined accessions, resistance probabilities to each of the investigated downy mildew races were relatively high for populations originating from Eastern Europe and Northern Asia
    A Bayesian analysis of gene flow from crops to their wild relatives: cultivated (Lactuca sativa L.) and prickly lettuce (L. serriola L.) and the recent expansion of L. serriola in Europe
    Uwimana, B. ; Andrea, L. D'; Felber, F. ; Hooftman, D.A.P. ; Nijs, H.C.M. den; Smulders, M.J.M. ; Visser, R.G.F. ; Wiel, C.C.M. van de - \ 2012
    Molecular Ecology 21 (2012)11. - ISSN 0962-1083 - p. 2640 - 2654.
    genetically-modified crops - multilocus genotype data - populus-nigra l. - population-structure - sect lactuca - situ conservation - hybridization - asteraceae - hybrids - spp.
    Interspecific gene flow can lead to the formation of hybrid populations that have a competitive advantage over the parental populations, even for hybrids from a cross between crops and wild relatives. Wild prickly lettuce (Lactuca serriola) has recently expanded in Europe and hybridization with the related crop species (cultivated lettuce, L. sativa) has been hypothesized as one of the mechanisms behind this expansion. In a basically selfing species, such as lettuce, assessing hybridization in natural populations may not be straightforward. Therefore, we analysed a uniquely large data set of plants genotyped with SSR (simple sequence repeat) markers with two programs for Bayesian population genetic analysis, STRUCTURE and NewHybrids. The data set comprised 7738 plants, including a complete genebank collection, which provided a wide coverage of cultivated germplasm and a fair coverage of wild accessions, and a set of wild populations recently sampled across Europe. STRUCTURE analysis inferred the occurrence of hybrids at a level of 7% across Europe. NewHybrids indicated these hybrids to be advanced selfed generations of a hybridization event or of one backcross after such an event, which is according to expectations for a basically selfing species. These advanced selfed generations could not be detected effectively with crop-specific alleles. In the northern part of Europe, where the expansion of L. serriola took place, the fewest putative hybrids were found. Therefore, we conclude that other mechanisms than crop/wild gene flow, such as an increase in disturbed habitats and/or climate warming, are more likely explanations for this expansion.
    Genetic resources collections of leafy vegetables (lettuce, spinach, chicory, artichoke, asparagus, lamb’s lettuce, rhubarb and rocket salad): composition and gaps
    Treuren, R. van; Coquin, P. ; Lohwasser, U. - \ 2012
    Genetic Resources and Crop Evolution 59 (2012)6. - ISSN 0925-9864 - p. 981 - 997.
    genetische bronnen van plantensoorten - bladgroenten - databanken - genenbanken - cichorei - slasoorten - spinazie - plant genetic resources - leafy vegetables - databases - gene banks - chicory - lettuces - spinach - cichorium-intybus l - species relationships - cultivated lettuce - globe artichoke - aflp markers - asteraceae - identification - conservation - populations - redundancy
    Lettuce, spinach and chicory are generally considered the main leafy vegetables, while a fourth group denoted by ‘minor leafy vegetables’ includes, amongst others, rocket salad, lamb’s lettuce, asparagus, artichoke and rhubarb. Except in the case of lettuce, central crop databases of leafy vegetables were lacking until recently. Here we report on the update of the international Lactuca database and the development of three new central crop databases for each of the other leafy vegetable crop groups. Requests for passport data of accessions available to the user community were addressed to all known European collection holders and to the main collection holders located outside Europe. Altogether, passport data of 17,530 accessions from a total of 129 collections were collected. The four separate databases were made available on line via a common entry page accessible at Based on a literature study, an analysis of the gene pool structure of the crops was performed and an inventory was made of the distribution areas of the species involved. The results of these surveys were related to the contents of the newly established databases in order to identify the main collection gaps. Priorities are presented for future germplasm acquisition aimed at improving the coverage of the crop gene pools in ex situ collections.
    The Relationship between Structurally Different Pyrrolizidine Alkaloids and Western Flower Thrips Resistance in F2 Hybrids of Jacobaea vulgaros and Jacobaea aquatica
    Cheng, D. ; Kirk, H. ; Vrieling, K. ; Mulder, P.P.J. ; Klinkhamer, P.G.L. - \ 2011
    Journal of Chemical Ecology 37 (2011)10. - ISSN 0098-0331 - p. 1071 - 1080.
    senecio-jacobaea - n-oxide - hybridization - evolution - plants - asteraceae - biosynthesis - herbivores - responses - ecology
    Segregating plant hybrids often have more ecological and molecular variability compared to parental species, and are therefore useful for studying relationships between different traits, and the adaptive significance of trait variation. Hybrid systems have been used to study the relationship between the expression of plant defense compounds and herbivore susceptibility. We conducted a western flower thrips (WFT) bioassay using a hybrid family and investigated the relationship between WFT resistance and pyrrolizidine alkaloid (PA) variation. The hybrid family consisted of two parental (Jacobaea vulgaris and Jacobaea aquatica) genotypes, two F1 genotypes, and 94 F2 hybrid lines. The J. aquatica genotype was more susceptible to thrips attack than the J. vulgaris genotype, the two F1 hybrids were as susceptible as J. aquatica, and susceptibility to WFT differed among F2 hybrid lines: 69 F2 lines were equally susceptible compared to J. aquatica, 10 F2 lines were more susceptible than J. aquatica and 15 F2 lines were as resistant as J. vulgaris or were intermediate to the two parental genotypes. Among 37 individual PAs that were derived from four structural groups (senecionine-, jacobine-, erucifoline- and otosenine-like PAs), the N-oxides of jacobine, jaconine, and jacoline were negatively correlated with feeding damage caused by WFT, and the tertiary amines of jacobine, jaconine, jacoline, and other PAs did not relate to feeding damage. Total PA concentration was negatively correlated with feeding damage. Among the four PA groups, only the total concentration of the jacobine-like PAs was negatively correlated with feeding damage. Multiple regression tests suggested that jacobine-like PAs play a greater role in WFT resistance than PAs from other structural groups. We found no evidence for synergistic effects of different PAs on WFT resistance. The relationship between PA variation and WFT feeding damage in the Jacobaea hybrids suggests a role for PAs in resistance to generalist insects.
    Pyrrolizidine alkaloid variation in shoots and roots of segregating hybrids between Jacobaea vulgaris and Jacobaea aquatica
    Cheng, D. ; Kirk, H. ; Mulder, P.P.J. ; Vrieling, K. ; Klinkhamer, P.G.L. - \ 2011
    New Phytologist 192 (2011)4. - ISSN 0028-646X - p. 1010 - 1023.
    senecionine n-oxide - british-isles - natural hybridization - plant hybridization - chemical diversity - tyria-jacobaeae - asteraceae - speciation - evolution - translocation
    Hybridization can lead to novel qualitative or quantitative variation of secondary metabolite (SM) expression that can have ecological and evolutionary consequences.•We measured pyrrolizidine alkaloid (PA) expression in the shoots and roots of a family including one Jacobaea vulgaris genotype and one Jacobaea aquatica genotype (parental genotypes), two F1 hybrid genotypes, and 102 F2 hybrid genotypes using liquid chromatography–tandem mass spectrometry (LC-MS/MS).•We detected 37 PAs in the roots and shoots of J. vulgaris, J. aquatica and the hybrids. PA concentrations and compositions differed between genotypes, and between roots and shoots. Three otosenine-like PAs that only occurred in the shoots of parental genotypes were present in the roots of F2 hybrids; PA compositions were sometimes novel in F2 hybrids compared with parental genotypes, and in some cases transgressive PA expression occurred. We also found that PAs from within structural groups covaried both in the roots and in the shoots, and that PA expression was correlated between shoots and roots.•Considerable and novel variation present among F2 hybrids indicates that hybridization has a potential role in the evolution of PA diversity in the genus Jacobaea, and this hybrid system is useful for studying the genetic control of PA expression
    Effects of light, hydropriming and abiotic stress on seed germination, and shoot and root growth of pyrethrum (Tanacetum cinerariifolium
    Li, J. ; Jongsma, M.A. ; Wang, C.Y. - \ 2011
    Industrial Crops and Products 34 (2011)3. - ISSN 0926-6690 - p. 1543 - 1549.
    improve germination - hydration treatment - osmotic-stress - drought stress - salt stress - water - temperature - management - asteraceae - tolerance
    Poor germination and seedling establishment are major problems in arid and semi-arid environments, and these characteristics are considered to be important factors in later plant growth and yield. Laboratory experiments were conducted on freshly harvested pyrethrum (Tanacetum cinerariifolium) seeds to investigate the effects of light (influenced by the seeding method) and seed hydropriming on germination, and shoot and root growth at 25 °C. Exposure to light could reduce germination from 52% to 22% and increase the mean germination time (MGT) from 7 to 12 days. The responses of hydroprimed and unprimed seeds to salt and drought stress were determined at osmotic potentials of 0 (distilled water), -0.3, -0.6, -0.9, -1.2 MPa in NaCl and PEG6000. Seed germination and seedling growth were inhibited by increasing salt and drought stress. The germination percentage of unprimed seeds was reduced from 52% to 16% in -1.2 MPa NaCl, and no seeds germinated at osmotic potentials =-0.9 MPa PEG. Both shoot and root growth were inhibited at osmotic potentials =-0.9 MPa NaCl and =-0.6 MPa PEG. Hydropriming shortened the delay of MGT at all osmotic potentials, and improved the germination percentage in distilled water (from 52% to 59%) and resistance to salt stress with nearly double germination (from 16% to 29%) at the highest salt concentration. When non-germinated seeds were transferred to distilled water after 20 days of incubation in total up to 12–15% of NaCl and 25–27% of PEG stressed seeds did not recover. These results show that the inhibition of the germination and seedling growth at the same osmotic potential of NaCl and PEG resulted from drought stress rather than salt toxicity, and that hydropriming is an effective tool to improve the quality of pyrethrum seeds.
    Biosynthesis and localization of parthenolide in glandular trichomes of feverfew (Tanacetum parthenium L. Schulz Bip.)
    Majdi, M. ; Liu, Q. ; Karimzadeh, G. ; Malboobi, M.A. ; Beekwilder, J. ; Cankar, K. ; Vos, C.H. de; Todorovic, S. ; Simonovic, A. ; Bouwmeester, H.J. - \ 2011
    Phytochemistry 72 (2011)14-15. - ISSN 0031-9422 - p. 1739 - 1750.
    germacrene-a synthase - artemisia-annua l - sesquiterpene lactones - gene-expression - amorpha-4,11-diene synthase - developmental regulation - migraine prophylaxis - double-blind - in-vitro - asteraceae
    Feverfew (Tanacetum parthenium) is a perennial medicinal herb and is a rich source of sesquiterpene lactones. Parthenolide is the main sesquiterpene lactone in feverfew and has attracted attention because of its medicinal potential for treatment of migraine and cancer. In the present work the parthenolide content in different tissues and developmental stages of feverfew was analyzed to study the timing and localization of parthenolide biosynthesis. The strongest accumulating tissue was subsequently used to isolate sesquiterpene synthases with the goal to isolate the gene encoding the first dedicated step in parthenolide biosynthesis. This led to the isolation and charachterization of a germacrene A synthase (TpGAS) and an (E)-ß-caryophyllene synthase (TpCarS). Transcript level patterns of both sesquiterpene synthases were analyzed in different tissues and glandular trichomes. Although TpGAS was expressed in all aerial tissues, the highest expression was observed in tissues that contain high concentrations of parthenolide and in flowers the highest expression was observed in the biosynthetically most active stages of flower development. The high expression of TpGAS in glandular trichomes which also contain the highest concentration of parthenolide, suggests that glandular trichomes are the secretory tissues where parthenolide biosynthesis and accumulation occur.
    Teelt van Aster op substraat
    Labrie, Caroline - \ 2010
    floriculture - asteraceae - aster - cropping systems - all-year-round production - crop yield - crop quality - trials - on-farm research
    Cassini's Compositae genera: A nomenclatural and taxonomic assessment
    Flann, C.M. ; Greuter, W. ; Hind, D.J.N. - \ 2010
    Taxon 59 (2010)4. - ISSN 0040-0262 - p. 1206 - 1244.
    asteraceae - senecioneae - systematics - astereae - vaillant - names - genus
    Work on the Global Compositae Checklist has highlighted uncertainties and errors in the nomenclatural parameters of many genera and subgenera described by Henri Cassini. Problems concern rank (subgenus vs. genus); type designation; correct place of valid publication; alternative names; and other miscellaneous issues. An annotated list with correct nomenclatural information for 391 generic names or designations is provided, including types (newly designated here for 17 names) and one new combination (Gyptis tanacetifolia). The current taxonomic disposition of Cassini's genera and the accepted names for the listed typonyms are consistently mentioned. The familiar names Felicia and Chrysopsis, already conserved, are threatened by unlisted earlier synonyms, and currently used Fulcaldea turns out to be illegitimate. Proposals to deal with these problems by conservation are being presented separately
    Distribution of genetic diversity in wild European populations of prickly lettuce (Lactuca serriola): implications for plant genetic resources management
    Wiel, C.C.M. van de; Sretenovic Rajicic, T. ; Treuren, R. van; Dehmer, K.J. ; Linden, C.G. van der; Hintum, T.J.L. van - \ 2010
    Plant genetic resources: characterization and utilization 8 (2010)2. - ISSN 1479-2621 - p. 171 - 181.
    molecular markers - linkage map - asteraceae - evolution - netherlands - acquisition - cluster - spp. - aflp - l.
    Genetic variation in Lactuca serriola, the closest wild relative of cultivated lettuce, was studied across Europe from the Czech Republic to the United Kingdom, using three molecular marker systems, simple sequence repeat (SSR, microsatellites), AFLP and nucleotide-binding site (NBS) profiling. The ‘functional’ marker system NBS profiling, targeting disease resistance genes of the NBS/LRR family, did not show marked differences in genetic diversity parameters to the other systems. The autogamy of the species resulted in low observed heterozygosity and high population differentiation. Intra-population variation ranged from complete homogeneity to nearly complete heterogeneity. The highest genetic diversity was found in central Europe. The SSR results were compared to SSR variation screened earlier in the lettuce collection of the Centre for Genetic Resources, the Netherlands (CGN). In the UK, practically only a single SSR genotype was found. This genotype together with a few other common SSR genotypes comprised a large part of the plants sampled on the continent. Among the ten most frequent SSR genotypes observed, eight were already present in the CGN collection. Overall, the CGN collection appears to already have a fair representation of genetic variation from NW Europe. The results are discussed in relation to sampling strategies for improving genebank collections of crop wild relatives.
    Effects of landscape structure on genetic diversity of Geum urbanum L. populations in agricultural landscapes
    Schmidt, T. ; Arens, P.F.P. ; Smulders, M.J.M. ; Billeter, R. ; Liira, J. ; Augenstein, I. ; Durka, W. - \ 2009
    Flora 204 (2009)7. - ISSN 0367-2530 - p. 549 - 559.
    habitat fragmentation - f-statistics - land-use - flow - distance - biodiversity - asteraceae - ecology - systems - europe
    Plant species in fragmented populations are affected by landscape structure because persistence within and migration among inhabited patches may be influenced by the identity and configuration of surrounding habitat elements. This may also be true for species of the semi-natural vegetation in agricultural landscapes. To determine the effect of landscape elements we analyzed Wood Avens (Geum urbanum L.) populations within three 4×4 km2 agricultural landscapes in Germany, Switzerland and Estonia, which differ in levels of land use intensity and habitat fragmentation. Genetic variation was determined in 15 randomly selected populations in each landscape using 10 microsatellite loci. The landscape structure was assessed at two circles around each population, with radii defined by the range limits of spatial genetic autocorrelation. Multiple regression analysis was used to determine the influence of landscape structure variables for inter- and intrapopulation genetic diversity. Gene diversity was equally high in Germany (He=0.27) and Switzerland (He=0.26) but lower in Estonia (He=0.16). A high overall inbreeding coefficient (FIS=0.89) was found, as expected for a selfing breeding system in G. urbanum. Genetic differentiation among populations was high (overall FST=0.43, 0.48, and 0.45 in Estonia, Switzerland and Germany, respectively), and did not differ among the three landscapes. Only a moderate influence of individual land use types on genetic diversity within and among populations was found with some idiosyncratic relationships. Genetic variation within populations was correlated to the amount of hedgerows positively in Estonia but negatively in Switzerland. The study demonstrates that the distribution of individual land use types affects the genetic pattern of a common plant species. However, different variables were identified to influence the genetic structure in three different landscapes. This indicates a major influence of landscape-specific land use history and stochastic processes determining gene flow and plant population structure
    Acquisition and ecological characterization of Lactuca serriola L. germplasm collected in the Czech Republic, , Germany, the Netherlands and United Kingdom
    Lebeda, A. ; Dolezalova, I. ; Kristkova, E. ; Dehmer, K.J. ; Astley, D. ; Wiel, C.C.M. van de; Treuren, R. van - \ 2007
    Genetic Resources and Crop Evolution 54 (2007)3. - ISSN 0925-9864 - p. 555 - 562.
    natural-populations - bremia-lactucae - asteraceae - spp.
    Expeditions were conducted in the Czech Republic, Germany, the Netherlands and United Kingdom in 2001 (partly 1998) to study Lactuca serriola L. (prickly lettuce, compass plant) geographic distribution, ecology, habitat characteristics and occurrence of diseases and pests on this species. During these missions the seed material of L. serriola L. was collected in an east¿west transect of these four countries. The European transect where seeds were collected and field observations were made represents a relatively large area between 2°34¿50¿¿ W¿17°32¿46¿¿ E and 47°40¿42¿¿¿54°04¿19¿¿ N. The seed material was used for regeneration, inclusion in the national genetic resources collections of individual countries and for research purposes in follow-up studies. During the missions, 50 locations with occurrence of L. serriola L. were visited (16 in Czech Republic and Germany, 10 in UK and 8 in the Netherlands). Individual seed lots of sixteen different plants were collected at each location (L. serriola L. population). Thus, in total 800 seed samples were collected. In Czech Republic and Germany L. serriola L. f. serriola dominated in all observed populations, in the Netherlands both f. serriola and f. integrifolia occurred in pure or mixed stands, whereas in the United Kingdom L. serriola L. f. integrifolia (S.F. Gray) S.D. Prince et R.N. Carter was dominant. L. serriola L. was recorded at various altitudes (¿4 to 410 m), different habitats (ditches, along roads, fields and field margins, ruderal places, pavements and parking sites, fallow fields), individual populations varied substantially in size (20 to >1000 plants), area covered (25¿10,000 m2), and the structure and character of associated plant communities. Natural infections by downy mildew (Bremia lactucae Regel) and powdery mildew (Golovinomyces cichoracearum (DC.) V.P. Gelyuta) were observed in some populations. B. lactucae Regel was recorded only in Czech Republic, G. cichoracearum (DC.) V.P. Gelyuta was more common in continental Europe. General and specific aspects of L. serriola L. geographic distribution and ecology are discussed.
    Teeltinnovatie Asterini
    Heij, G. - \ 2007
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten WUR Glastuinbouw ) - 15
    asteraceae - cultivars - rassen (planten) - cultuurmethoden - hergroei - teeltsystemen - teelt onder bescherming - nederland - glastuinbouw - asteraceae - cultivars - varieties - cultural methods - regrowth - cropping systems - protected cultivation - netherlands - greenhouse horticulture
    Houdbaarheidsonderzoek Gerbera - Uitgevoerd voor Syngenta Seeds B.V.
    Noort, F.R. van; Esteban-Rodriquez, Angela - \ 2007
    Wageningen : Wageningen UR Glastuinbouw (Nota / Wageningen UR Glastuinbouw 481) - 14
    tuinbouw - gerbera - bloementeelt - asteraceae - rassen (planten) - potplanten - remmers - temperatuur - houdbaarheid (kwaliteit) - onderzoek - bemesting - horticulture - gerbera - floriculture - asteraceae - varieties - pot plants - inhibitors - temperature - keeping quality - research - fertilizer application
    Door Syngenta Seeds B.V. zijn tegelijkertijd verschillende onderzoeken uitgevoerd met potgerbera en met de meeste behandelingen zijn houdbaarheidonderzoek uitgevoerd om de invloed daarvan op de planten te vergelijken. Er zijn verschillen aangelegd tussen rassen, remstoffen, bemesting, daglengte en temperatuurverlaging drie weken voor afleveren en die worden achtereenvolgens in de hoofdstukken 2, 3, 4, 5 en 6 besproken. Om te onderzoeken of deze behandelingen invloed hebben op de houdbaarheid van potgerbera is vanaf week 45 tot week 52 een houdbaarheidsonderzoek uitgevoerd bij WUR Glastuinbouw (voorheen PPO Glastuinbouw) in Naalwijk. De planten zijn in week 45, 46 en 47 aangeleverd en hebben één week transportsimulatie gehad. Deze transportsimulatie houdt in dat de planten ingehoesd in dozen bij 20°C en 70% RV staan in een donkere cel. Na die week zijn de planten beoordeeld en in een uitbloeiruimte geplaatst bij een temperatuur van 20∘C, 60% Rv, 12 uur licht, 12 uur donker bij 14 μmol PAR licht (= 1000 lux – 3.4 w/m2) met licht van tl 58 watt, kleur 84. Dit zijn internationaal geldende afspraken. De planten zijn in de cel ogenschijnlijk niet achteruit gegaan, m.a.w. er is geen direct zichtbare schade ontstaan door de transportsimulatie
    Met yacòn de boer op : vaststellen van de grenzen aan bruikbaarheid, verwerkbaarheid en geschiktheid van yacòn
    Braaksma, A. ; Heijden, C.H.T.M. van der - \ 2007
    Wageningen : Wetenschapswinkel Wageningen UR (Rapport / Wetenschapswinkel Wageningen UR 233) - ISBN 9789085850755 - 20
    groenten - wortelgewassen als groente - productontwikkeling - beschrijvingen - recepten - voedselbereiding - verkleuring - inuline - asteraceae - nieuwe cultuurgewassen - vegetables - root vegetables - product development - descriptions - recipes - food preparation - discoloration - inulin - asteraceae - new crops
    Mogelijkheden biologische bestrijding van Agrobacterium in Aster
    Wubben, J.P. ; Wolf, J.M. van der - \ 2006
    Wageningen : PPO, Glastuinbouw (Rapporten PPO Glastuinbouw ) - 20
    asteraceae - aster - plantenziekteverwekkende bacteriën - rhizobium - asteraceae - aster - plant pathogenic bacteria - rhizobium
    Beheersstrategie suikerrot
    Scholte-Wassink, G.M. - \ 2004
    PPO BU Glastuinbouw (Rapporten PPO BU GlastuinbouwAalsmeer ) - 98
    asteraceae - gerbera - plantenziekten - suikers - sierplanten - plantenziektebestrijding - asteraceae - gerbera - plant diseases - sugars - ornamental plants - plant disease control
    Op basis van een overzicht van gegevens over bestrijdingsmogelijkheden van suikerrot met hierbij in het bijzonder aandacht voor Drosophila en Geotrichum, en de oorzaak van een verhoogde vatbaarheid van gerberaplanten voor de ziekte, zou een beheersstrategie ontwikkeld kunnen worden die de teler handvaten biedt6 om suikerrot te controleren.
    Reconstructing the origin of Helianthus deserticola: Survival and selection on the desert floor
    Gross, B.L. ; Kane, D.L. ; Lexer, C. ; Ludwig, F. ; Rosenthal, D.R. ; Donovan, L.A. ; Rieseberg, L.H. - \ 2004
    American Naturalist 164 (2004)2. - ISSN 0003-0147 - p. 145 - 156.
    boron toxicity tolerance - hybrid speciation - mediterranean populations - transgressive segregation - aquilegia-pubescens - water-stress - asteraceae - evolution - ancient - plants
    The diploid hybrid species Helianthus deserticola inhabits the desert floor, an extreme environment relative to its parental species Helianthus annuus and Helianthus petiolaris. Adaptation to the desert floor may have occurred via selection acting on transgressive, or extreme, traits in early hybrids between the parental species. We explored this possibility through a field experiment in the hybrid species' native habitat using H. deserticola, H. annuus, H. petiolaris, and two populations of early-generation (BC2) hybrids between the parental species, which served as proxies for the ancestral genotype of the ancient hybrid species. Character expression was evaluated for each genotypic class. Helianthus deserticola was negatively transgressive for stem diameter, leaf area, and flowering date, and the latter two traits are likely to be advantageous in a desert environment. The BC 2 hybrids contained a range of variation that overlapped these transgressive trait means, and an analysis of phenotypic selection revealed that some of the selective pressures on leaf size and flowering date, but not stem diameter, would move the BC2 population toward the H. deserticola phenotype. Thus, H. deserticola may have originated from habitat-mediated directional selection acting on hybrids between H. annuus and H. petiolaris in a desert environment.
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