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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

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Genetic diversity and evolution in Lactuca L. (Asteraceae) : from phylogeny to molecular breeding
Wei, Z. - \ 2016
Wageningen University. Promotor(en): Eric Schranz. - Wageningen : Wageningen University - ISBN 9789462576148 - 210
lactuca sativa - leafy vegetables - phylogeny - genetic diversity - domestication - molecular breeding - genomes - dna - quantitative trait loci - evolution - lactuca sativa - bladgroenten - fylogenie - genetische diversiteit - domesticatie - moleculaire veredeling - genomen - dna - loci voor kwantitatief kenmerk - evolutie

Cultivated lettuce (Lactuca sativa L.) is an important leafy vegetable worldwide. However, the phylogenetic relationships between domesticated lettuce and its wild relatives are still not clear. In this thesis, I focus on the phylogenetic relationships within Lactuca L., including an analysis of the wild Lactuca species that are endemic to Africa for the first time. The genetic variation of responses to salinity in a recombinant inbred line population, derived from a cross between the lettuce crop (L. sativa ‘Salinas’) and wild species (L. serriola), was investigated and the candidate gene in the identified QTL regions was further studied.

In Chapter 1, I introduce and discuss topics related to genetic diversity and evolution in Lactuca, including an overview of lettuce cultivars and uses, its hypothesized domestication history, the taxonomic position of Lactuca, current status of molecular breeding in lettuce and mechanisms of salinity tolerance in plants, especially the High-affinity K+ Transporter (HKT) gene family.

In Chapter 2, the most extensive molecular phylogenetic analysis of Lactuca was constructed based on two chloroplast genes (ndhF and trnL-F), including endemic African species for the first time. This taxon sampling covers nearly 40% of the total Lactuca species endemic to Africa and 34% of all Lactuca species. DNA sequences from all the subfamilies of Asteraceae in Genbank and those generated from Lactuca herbarium samples were used to elucidate the monophyly of Lactuca and the affiliation of Lactuca within Asteracaeae. Based on the subfamily tree, 33 ndhF sequences from 30 species and 79 trnL-F sequences from 48 species were selected to infer phylogenetic relationships within Lactuca using Randomized Axelerated Maximum Likelihood (RAxML) and Bayesian Inference (BI) analyses. In addition, biogeographical, chromosomal and morphological character states were analysed based on the Bayesian tree topology. The results showed that Lactuca contains two distinct phylogenetic clades - the crop clade and the Pterocypsela clade. Other North American, Asian and widespread species either form smaller clades or mix with the Melanoseris species in an unresolved polytomy. The newly sampled African endemic species probably should be excluded from Lactuca and treated as a new genus.

In Chapter 3, twenty-seven wild Lactuca species and four outgroup species were sequenced using next generation sequencing (NGS) technology. The sampling covers 36% of total Lactuca species and all the important geographical groups in the genus. Thirty chloroplast genomes, including one complete (partial) large single copy region (LSC), one small single copy region (SSC), one inverted repeat (IR) region, and twenty-nine nuclear ribosomal DNA sequences (containing the internal transcribed spacer region ) were successfully assembled and analysed. A methodology paper for which I am co-author, but is not included in this thesis, of the sequencing pipeline was published: ‘Herbarium genomics: plastome sequence assembly from a range of herbarium specimens using an Iterative Organelle Genome Assembly (IOGA) pipeline’. These NGS data helped resolve deeper nodes in the phylogeny within Lactuca and resolved the polytomy from Chapter 2. The results showed that there are at least four main groups within Lactuca: the crop group, the Pterocypsela group, the North American group and the group containing widely-distributed species. I also confirmed that the endemic African species should be removed and treated as a new genus.

In Chapter 4, quantitative trait loci (QTLs) related to salt-induced changes in Root System Architecture (RSA) and ion accumulation were determined using a recombinant inbred line population derived from a cross between cultivated lettuce and wild lettuce. I measured the components of RSA by replicated lettuce seedlings grown on vertical agar plates with different NaCl concentrations in a controlled growth chamber environment. I also quantified the concentration of sodium and potassium in replicates of greenhouse-grown plants watered with 100 mM NaCl. The results identified a total of fourteen QTLs using multi-trait linkage analysis, including three major QTLs associated with general root development (qRC9.1), root growth in salt stress condition (qRS2.1), and ion accumulation (qLS7.2).

In Chapter 5, one of the identified QTL regions (qLS7.2) reported in Chapter 4 was found to contain a homolog of the HKT1 from Arabidopsis thaliana. I did a phylogenetic analysis of Lactuca HKT1-like protein sequences with other published HKT protein sequences and determined transmembrane and pore segments of lettuce HKT1;1 alleles, according to the model proposed for AtHKT1;1. Gene expression pattern and level of LsaHKT1;1 (L. sativa ‘Salinas’) and LseHKT1;1 (L. serriola) in root and shoot were investigated in plants growing hydroponically over a time-course. The measurements of Na+ and K+ contents were sampled at the same time as the samples used for gene expression test. In addition, I examined the 5’ promoter regions of the two genotypes. The results showed low expression levels of both HKT1;1 alleles in Lactuca root and relatively higher expression in shoot, probably due to the negative cis-regulatory elements of HKT1 alleles found in Lactuca promoter regions. Significant allelic differences were found in HKT1;1 expression in early stage (0-24 hours) shoots in and in late stage (2-6 days) roots. shoot HKT1;1 expression/root HKT1;1 expression was generally consistent with the ratios of Na+/K+ balance in the relevant tissues (shoot Na+/K+ divided by root Na+/K+).

In Chapter 6, I summarize and discuss the results from previous chapters briefly. The implications of Chapter 2 and 3 for Lactuca phylogenetics are discussed, including some key characters for the diagnosis of species within Lactuca, the use of herbarium DNA for NGS technology, and perspectives into Lactuca phylogeny. Future perspectives of genome-wide association mapping for lettuce breeding were also discussed. Lastly, I propose to integrate phylogenetic approaches into investigations of allelic differences in lettuce, not just associated with salinity stress but also with other stressed and beneficial characters, both within and between species.

Verkennen van nieuwe mogelijkheden voor de bestrijding van wortelduizendpoot in de glastuinbouw
Kruidhof, H.M. ; Bloemhard, C.M.J. - \ 2015
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1381) - 18 p.
slasoorten - lactuca sativa - glasgroenten - scutigerella immaculata - gewasbescherming - plagenbestrijding - fusarium oxysporum - glastuinbouw - lettuces - greenhouse vegetables - plant protection - pest control - greenhouse horticulture
In the autumn of 2014 many companies specialized in protected lettuce cultivation were confronted with severe plant damage. In several lettuce greenhouses garden centipedes were detected. This explorative study summarizes the available knowledge of garden centipedes, and describes new possibilities for their control (chapter 1). It also tested one of the new control options, i.e. luring the garden centipedes with CO2-capsules, in a laboratory set-up (chapter 2). At the concentration tested, no luring effect of the CO2-capsules on the garden centipedes could be detected.
At the same time it was found that many damaged lettuce plants suffered from Fusarium root damage. From research by the NVWA (Netherlands Food and Consumer Product Safety Authority) Fusarium was eventually identified as F. oxysporum lactucae. Finally, this seemed to be the most important culprit of the observed plant damage.
Genetic investigation of the nonhost resistance of wild lettuce, Lactuca saligna, to lettuce downy mildew, Bremia lactucae
Boer, E. den - \ 2014
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Marieke Jeuken; Rients Niks. - Wageningen : Wageningen University - ISBN 9789462572072 - 186
lactuca saligna - schimmelziekten - bremia lactucae - ziekteresistentie - terugkruisen - inteeltlijnen - genetische kartering - lactuca sativa - lactuca saligna - fungal diseases - bremia lactucae - disease resistance - backcrossing - inbred lines - genetic mapping - lactuca sativa


Downy mildew (Bremia lactucae) in lettuce (Lactuca sativa) is a devastating foliar disease causing high losses in lettuce cultivation. The wild lettuce and nonhost species, Lactuca saligna, is absolute resistant to downy mildew and cross-fertile with L. sativa, albeit with a low success rate and occasional reduced fertility and/or vitality in later inbred generations. This exceptional availability of hybrid plant offsprings creates a unique opportunity to study nonhost resistance by a genetic approach.

The L. saligna nonhost resistance genes might be more durable than the classical monogenic race-specific R genes that are mainly used in lettuce breeding. The identification of genes conferring nonhost resistance is a crucial step in its understanding and usage in breeding.

In this thesis the quantitative resistances of three backcross introgression lines (BILs), carrying an individual 30 to 50 cM long introgression segment from L. saligna in a L. sativa background, were fine mapped. Disease evaluation of sub-BILs with smaller introgression segments revealed that the resistance of all three BILs was explained by 17 sub-QTLs with a smaller and plant stage dependent effect, some segments reducing, others even promoting downy mildew infection.

Further the potential of stacking quantitative resistances of eight BILs per combinations of two was tested under field conditions. Only three out of ten double-combinations resulted in an increased resistance level compared to their parental individual lines, from which one had additive and two had epistatic interactions between the introgressions.

As the studies on individual QTL effects of BILs did not reveal potential genetic interactions that could explain the complete resistance of L. saligna, a novel approach was set out to search for indications of epistatic interactions. ‘Selective genotyping’ was applied on the phenotypic disease extremes of large F2 offsprings, in which multi-locus interactions between L. saligna alleles are still prevalent. In a kind of bulked segregant analysis approach four major resistance regions were identified. Preliminary results showed epistatic interactions between the regions on Chromosome 6 and 1 and between Chromosome 6 and 7.

During the development of sub-BILs, a digenic hybrid incompatibility was observed: plants carrying a L. saligna segment on Chromosome 6 always required a L. saligna segment on Chromosome 4. Segregation analysis suggested a prezygotic reproductive barrier by non-transmission of one specific hybrid gametophyte (male and female).

In cooperation with the research group of Guido van den Ackerveken of University Utrecht a lettuce germplasm screening was conducted for candidate downy mildew effector proteins, which interact with resistance genes in lettuce and trigger a defence response. One of two responsive effector proteins, ‘BLG01’, triggered a hypersensitive cell death response in most tested L. saligna accessions and its response was mapped on Chromosome 9.

Despite the complex interactions between resistance QTLs, this thesis research has delivered many insights that are important steps forward towards understanding the incompatible interaction between B. lactucae and L. saligna and its future application in resistance breeding.

Physiology and genetics of root growth, resource capture and resource use efficiency in lettuce (Lactuca sativa L.)
Kerbiriou, P.J. - \ 2014
Wageningen University. Promotor(en): Edith Lammerts van Bueren; Paul Struik, co-promotor(en): Tjeerd-Jan Stomph. - Wageningen : Wageningen University - ISBN 9789462570863 - 179
lactuca sativa - slasoorten - cultivars - groei - wortels - scheuten - plantenontwikkeling - nutriëntengebruiksefficiëntie - voedingsfysiologie - watergebruiksrendement - genetische variatie - droogteresistentie - tolerantie van variëteiten - genotype-milieu interactie - biologische plantenveredeling - lactuca sativa - lettuces - cultivars - growth - roots - shoots - plant development - nutrient use efficiency - nutrition physiology - water use efficiency - genetic variation - drought resistance - varietal tolerance - genotype environment interaction - organic plant breeding
Biologische evenwicht in waterbassins : tuinen bij Wageningen UR Glastuinbouw (interview met Tycho Vermeulen)
Strating, J. ; Vermeulen, T. - \ 2013
Kas techniek 2013 (2013)3. - p. 24 - 25.
teeltsystemen - bladgroenten - lactuca sativa - hydrocultuur - waterbeheer - plantenziekten - landbouwkundig onderzoek - cropping systems - leafy vegetables - hydroponics - water management - plant diseases - agricultural research
De teelt van sla op water neemt internationaal een aardige vlucht. Maar hoewel de productiemethode veel voordelen biedt voor telers, lopen zij in de praktijk nog tegen problemen aan. Zo wordt het water besmet door pathogenen en andere organismen. Reden voor Wageningen UR Glastuinbouw om middels proeven te komen tot weerbaarder water.
Unravelling the resistance mechanism of lettuce against Nasonovia ribisnigri
Broeke, C.J.M. ten - \ 2013
Wageningen University. Promotor(en): Joop van Loon; Marcel Dicke. - S.l. : s.n. - ISBN 9789461735782 - 228
lactuca virosa - lactuca sativa - slasoorten - insectenplagen - nasonovia ribisnigri - plaagresistentie - verdedigingsmechanismen - gedrag bij zoeken van een gastheer - insect-plant relaties - lactuca virosa - lactuca sativa - lettuces - insect pests - nasonovia ribisnigri - pest resistance - defence mechanisms - host-seeking behaviour - insect plant relations

Aphids are serious pests of crop plant species, and host plant resistance is often the most effective and environmentally friendly control strategy to control these pests. One of these aphid pests is the black currant - lettuce aphid, Nasonovia ribisnigri (Mosely), an economically important pest of cultivated lettuce, Lactuca sativa L. Host plant resistance has been used since 1982 to control this aphid species and is mediated by the Nr-gene, originating from wild lettuce Lactuca virosa L. However, this resistance is not effective anymore, since N. ribisnigri aphids virulent to the Nr-resistance have been reported since 2007. The aim of this thesis was to unravel the mechanism of resistance mediated by the Nr-gene against N. ribisnigri, by behavioural studies on the aphids on both resistant and susceptible lettuce, to allow lettuce breeders to accelerate their resistance breeding programmes. Although the exact mechanism of Nr-mediated resistance remains unknown, the data in this thesis provide insight into this mechanism. The active site of the Nr-mediated resistance is mainly located in the phloem and some resistance might be encountered by the aphids along the pathway to the phloem. The inability of the avirulent aphids to feed from the resistant plant could be caused by the failure of aphids to suppress the wound response of the sieve element. The resistance factor(s) are only produced in the shoot, because grafts with resistant shoots and susceptible roots were resistant, whereas grafts with susceptible shoots and resistant roots remained susceptible. An intact vascular system is needed for full resistance, because both detached leaves and leaf disks of resistant lettuce plants were less resistant.

Variation in virulence was observed among populations of different geographical origin. Aphids from a highly virulent population performed equally well on both resistant and susceptible lettuce plants, whereas semi-virulent aphids performed better on susceptible lettuce plants. Both short-term and long-term virulence loss were observed for virulent aphid populations differing in virulence level, which indicates this virulence is associated with fitness costs. A possible mechanism underlying virulence in N. ribisnigri to the Nr-resistance is the presence of an effector protein in the salivary secretion of the aphids suppressing resistance. Virulent aphids seemed to actively suppress the resistance in lettuce against the avirulent aphids.

The original donor or the Nr-resistance, L. virosa accession IVT 280, was tested as possible source of new resistance against the virulent biotypes of N. ribisnigri and was foundfully resistant against virulent aphids, and can be exploited as a source of resistance in breeding for new resistance in cultivated lettuce.

A historical analysis of diversity trends in French and Dutch lettuce cultivars
Wouw, M.J. van de; Treuren, R. van; Hintum, T.J.L. van - \ 2013
Euphytica 190 (2013)2. - ISSN 0014-2336 - p. 229 - 239.
genetische erosie - genetische diversiteit - lactuca sativa - slasoorten - rassen (planten) - oude plantenrassen - diversiteit - frankrijk - nederland - bladgroenten - groenten - genetic erosion - genetic diversity - lettuces - varieties - old varieties - diversity - france - netherlands - leafy vegetables - vegetables - genebank collection - erosion
Using historical seed catalogues in combination with molecular fingerprinting data, diversity trends of lettuce, representing an important vegetable with active breeding programmes, were studied. Seed catalogues originating from France and the Netherlands from five different decades, the earliest dating from the 1840s, were checked for the occurence of lettuce cultivars. A total of 225 catalogues, with 7,311 records of lettuce, representing 878 different cultivars were found. The number of unique cultivars on offer by French and Dutch companies showed a small continuous increase until the 1960s, after which the number of cultivars on offer more than doubled to a total of 534 in the 1990s. Only a relatively small overlap between France and the Netherlands in the range of cultivars offered was observed. The 1960s appeared to be a period with many changes: the lowest genetic diversity in lettuce cultivars was found for this decade, whereas after the 1960s the number of companies supplying lettuce seeds reduced dramatically. The percentage of companies in a decade offering an identical cultivar decreased over time, and in the 1990s almost all cultivars were unique to only a single company. The possible relations of the observed trends with the developments in plant variety protection and in the plant breeding industry are discussed.
A genetic analysis of the introgression process from cultivated lettuce (Lactuca sativa L.) to wild prickly lettuce (L. serriola L.)
Uwimana, B. - \ 2011
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Rene Smulders; Clemens van de Wiel. - [S.l.] : S.n. - ISBN 9789461730312 - 144
lactuca sativa - lactuca serriola - wilde verwanten - hybridisatie - genetische analyse - introgressie - genenstroom - terugkruisen - plantenveredeling - lactuca sativa - lactuca serriola - wild relatives - hybridization - genetic analysis - introgression - gene flow - backcrossing - plant breeding

Many plant species can hybridise and produce fertile offspring. Hybridization between cultivated species and their wild relatives has raised concerns with regard to GM crops, as it constitutes a possible route along which the transgene could disperse from crops into related wild species, establish itself in the natural population, and persist under natural conditions. This may cause unintended ecological consequences such as the formation of more invasive weeds and genetic erosion. After crop-wild hybridization, the persistence of the hybrids and of the crop genes (including the transgenes) in later generations depends on their genetic make-up, which consists of specific combinations of wild and crop genomic segments, and on the environmental conditions. Therefore, knowledge on the dynamics of crop-wild hybridization and introgression using conventional crop varieties is needed as it constitutes the baseline for putting into perspective the effects of transgene introgression under natural conditions.

This study focused on understanding the genetic process of hybridization and introgression from cultivated to wild relative species using cultivated lettuce (Lactuca sativa L.) and its closest wild relative, prickly lettuce (L. serriola L.) as a crop-wild complex model. Natural populations of prickly lettuce in Europe were tested for the occurrence of crop-wild hybrids using Bayesian-based programmes (Structure, InStruct and NewHybrids) which returned a crop-wild hybrid occurrence of 7%. However, the geographical location of the hybrids led to the conclusion that crop-wild hybridization is not the cause of the recent northward spread of L. serriola in Europe.

To test for the importance of the crop genomic segments to the performance of lettuce crop-wild hybrids, three hybrid generations were created (F2 as a selfing generation, and BC1 and BC2, backcrossed to the wild genotype to mimick the introgression process) by crossing L. sativa (cv. Dynamite) with L. serriola collected from Eys (the Netherlands). The three populations were genotyped with Single Nucleotide Polymorphism markers for genetic analysis. Because of the importance of the abiotic stresses as selection factors under natural conditions and the prospective of generating GM crop varieties with enhanced abiotic stress tolerance, the three populations were evaluated for vigour at the rosette stage under greenhouse conditions of non-stress, drought, salinity and nutrient deficiency. The BC1 population was also evaluated under field conditions at two locations (Wageningen and Sijbekarspel, the Netherlands) for hybrid germination, vigour, survival and reproduction. Based on the location and allelic effect of the QTLs for germination, vigour, survival and reproductive traits in the current lettuce crop-wild cross, genomic regions were suggested where transgenes could be or could not be located in order to mitigate their persistence in crop-wild hybrids through genetic hitchhiking and background selection.

Authenticity of old cultivars in genebank collections: a case study on lettuce
Wouw, M.J. van de; Treuren, R. van; Hintum, T.J.L. van - \ 2011
Crop Science 51 (2011)2. - ISSN 0011-183X - p. 736 - 746.
genenbanken - slasoorten - aflp - oude plantenrassen - ex-situ conservering - cultivarauthenticiteit - lactuca sativa - rassen (planten) - cultivars - gene banks - lettuces - amplified fragment length polymorphism - old varieties - ex situ conservation - cultivar authenticity - varieties - genetic diversity - maintenance - accessions - longevity - level - l.
Ex situ collections in genebanks conserve many old cultivars that had disappeared from mainstream agriculture before modern genebanks were established. The collections incorporated cultivars from many sources, such as botanical gardens and working collections, sometimes with little further information on their origin. Many old cultivars with identical or synonymous names are maintained in multiple collections and often more than once within collections. This research investigates the authenticity of old cultivars in genebanks using a large lettuce (Lactuca sativa L.) collection as a case study. Accessions presumed to be identical, based on the cultivar names accompanying the accessions, were compared for their DNA marker profiles, based on amplified fragment length polymorphisms (AFLPs). Using the genetic similarity of these accessions, the probability of authenticity of the old cultivars maintained in the collection was estimated. Separate analyses were done for different classes of cultivars, on the basis of the year of release or the donor history of the cultivar. The two largest cultivar groups within the collection, Sans Rivale à Graine Blanche and Maikönig, were analyzed in detail. Nonauthenticity of the investigated cultivars appeared to be high. This was especially true for the oldest cultivars, but even for the cultivars released from the 1960s to 1990 it was estimated that approximately 10% was not authentic. Recommendations to improve authenticity of cultivars in ex situ collections were presented
Marker-assisted reduction of redundancy in a genebank collection of cultivated lettuce
Treuren, R. van; Groot, E.C. de; Boukema, I.W. ; Wiel, C.C.M. van de; Hintum, T.J.L. van - \ 2010
Plant genetic resources: characterization and utilization 8 (2010)2. - ISSN 1479-2621 - p. 95 - 105.
lactuca sativa - genenbanken - genetische merkers - genetische variatie - selectie - efficiëntie - moleculaire merkers - lactuca sativa - gene banks - genetic markers - genetic variation - selection - efficiency - molecular markers - wild potato germplasm - ex-situ conservation - lactuca-sativa l. - genetic diversity - aflp markers - duplication - rationalization - optimization
To reduce the level of redundancy in a collection of cultivated lettuce, data from 160 amplified fragment length polymorphism (AFLP) fragments and 10 polymorphic microsatellites were used in combination with passport data and morphological data, the latter obtained from an experimental field trial performed for verification purposes. Based on the observed distribution of the number of marker differences between and within accessions, a minimum of three AFLP differences and two microsatellite differences were regarded as levels warranting distinction between accessions in the redundancy analysis. The strategy followed in the redundancy analysis was mainly based on the confirmation of duplication by each of two independently generated data sources. The molecular data were used for the validation as well as the identification of potential duplicates, revealing a total number of 198 redundancies, corresponding to 12.9% of the total collection. Trueness to type, number of characterization and evaluation data, and collection management considerations, such as available seed quantities and germination percentages, were used as primary, secondary and tertiary criteria to decide which accession from duplication groups to maintain in the collection. Removal of accessions showed negligible effects on total collection diversity, as quantified for AFLPs and microsatellites, characterization and evaluation traits and resistance profiles against downy mildew pathotypes, indicating that the applied strategy was effective.
Effectiviteit van middelen tegen Rhizoctonia in sla en radijs
Hofland-Zijlstra, J.D. ; Paternotte, S.J. ; Janse, J. ; Slooten, M.A. van - \ 2008
Bleiswijk : Wageningen UR Glastuinbouw - 15
rhizoctonia - lactuca sativa - bladgroenten - raphanus - radijsjes - plantenziekten - glastuinbouw - gewasbescherming - plantenziektebestrijding - leafy vegetables - radishes - plant diseases - greenhouse horticulture - plant protection - plant disease control
Rhizoctonia is een veelvoorkomend probleem in sla en radijs en kan veel opbrengstverlies geven. Uit eerder onderzoek van Wageningen UR Glastuinbouw in radijs werd gevonden dat het enige toegelaten fungicide tegen Rhizoctonia in de praktijk niet voldoende werkt. Door het kleine middelenpakket in de bladgewassen was het daarom noodzakelijk om op zoek te gaan naar nieuwe alternatieven. Het doel van dit onderzoek was om onder gecontroleerde kascondities na te gaan welke middelen Rhizoctonia effectief kunnen bestrijden in sla en radijs en het middel Rizolex kunnen vervangen of aanvullen. De proeven zijn in de wintermaanden (december tot februari) uitgevoerd. Voor beide gewassen zijn een aantal veelbelovende alternatieven naar voren gekomen. Nieuwe effectieve middelen tegen Rhizoctonia in sla De slaplanten werd in diepe containers met zand geteeld en het zand was van tevoren besmet met Rhizoctonia. Twee middelen werden toegediend als grondbehandeling en de andere vier als bladbespuiting. Twee weken na planten werd de eerste bladaantasting door Rhizoctonia zichtbaar bij de controlebehandeling. Vanuit het blad groeide deze aantasting door naar de plantvoet. Planten die behandeld waren met Rizolex vertoonden in de laatste week vlak voor de oogst uitval doordat de aangetaste plantvoet afbrak. Twee middelen (oa. Signum die nog geen toelating heeft voor dit doel) die als bladbehandeling waren toegediend gaven een goede bescherming tegen aantasting van Rhizoctonia en presteerden beter dan Rizolex. De andere drie geteste middelen gaven geen betere bescherming ten opzichte van Rizolex. Nieuwe effectieve middelen tegen Rhizoctonia in radijs De radijszaden werden in diepe containers geteeld en het zand in alle containers was van tevoren besmet met Rhizoctonia. De middelen werden in overleg met de fabrikant toegediend als zaadbehandeling, bodem_ of bladbespuiting. Door de extra belichting kon na acht weken de proef worden geoogst. In de controlebehandelingen was gemiddeld 20% knoluitval door Rhizoctonia. De behandeling met Trianum (met de schimmel Trichoderma harzianum) reduceerde de aantasting met 35% ten opzichte van de controleplanten, maar dit gaf helaas nog steeds te veel uitval van knollen. Drie nieuwe middelen gaven net als Rizolex slechts 1% knolaantasting. Eén daarvan die als bladbehandeling was toegediend gaf groeiremming, maar reduceerde wel de aantasting evengoed als Rizolex. De behandeling waarbij Rizolex gecombineerd werd met een zaadbehandeling en een ander nieuw middel gaf geen enkele knolaantasting. Doordat de planten behandeld met de nieuwe middelen effectief Rhizoctonia aantasting bestreden, was de productie ook hoger dan van de planten in de controlebehandeling. Dit betekende vooral een hogere fractie van grove knollen (> 25 mm).
Ecology and risk assessment of E. coli O157:H7 and Salmonella typhimurium in the primary production chain of lettuce
Franz, E. - \ 2007
Wageningen University. Promotor(en): Ariena van Bruggen, co-promotor(en): Aad Termorshuizen. - [S.l.] : S.n. - ISBN 9789085047285 - 216
lactuca sativa - slasoorten - voedselbesmetting - escherichia coli - salmonella typhimurium - stalmest - risicofactoren - microbiële ecologie - bodem - biologische landbouw - biologische voedingsmiddelen - primaire productie - lactuca sativa - lettuces - food contamination - escherichia coli - salmonella typhimurium - farmyard manure - risk factors - microbial ecology - soil - organic farming - organic foods - primary production
Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratorysimulated lettuce production chain. Dairy cows were fed 3 different roughage types: high digestible grass silage + maize silage (6:4), low digestible grass silage and straw. Each was adjusted with supplemental concentrates to a high and low crude protein level. The pathogens were added to manure which was subsequently mixed (after 56 and 28 d for resp. E. coli O157:H7 and Salmonella serovar Typhimurium) with 2 pairs of organically and conventionally managed loamy and sandy soil. After another 14 d, iceberg-lettuce seedlings were planted and checked for pathogens after 21 d of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157: H7 in soil). Roughage type significantly influenced the decline rate of E. coli O157: H7 in manure with the fastest decline in manure from the pure straw diet and the slowest in manure from the grass-silage + maize-silage diet. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw compared to the manure from the grass-silage + maize-silage diet. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic compared to conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.
Quantitative detection of Salmonella enterica and the specific interaction with Lactuca sativa
Klerks, M.M. - \ 2007
Wageningen University. Promotor(en): Ariena van Bruggen, co-promotor(en): Carolien Zijlstra. - [S.l.] : S.n. - ISBN 9789085046745 - 184
lactuca sativa - slasoorten - salmonella - gastheer parasiet relaties - detectie - kwantitatieve technieken - polymerase-kettingreactie - methodologie - escherichia coli - pathogenen - uitbraken (ziekten) - gezondheid - lactuca sativa - lettuces - salmonella - host parasite relationships - detection - quantitative techniques - polymerase chain reaction - methodology - escherichia coli - pathogens - outbreaks - health
Effect of stale seedbed preparations and subsequent weed control in lettuce (cv. Iceboll) on weed densities
Riemens, M.M. ; Weide, R.Y. van der; Bleeker, P.O. ; Lotz, L.A.P. - \ 2007
Weed Research 47 (2007)2. - ISSN 0043-1737 - p. 149 - 156.
onkruidbestrijding - zaaibedbereiding - zaaibedden - onkruidwieders - eggen - schoffels - glyfosaat - rotatiewieders - lactuca sativa - slasoorten - weed control - seedbed preparation - seedbeds - weeders - harrows - hoes - glyphosate - rotary weeders - lactuca sativa - lettuces - soybean glycine-max - light environment - short-duration - germination - soil - dormancy - induction - tillage - photocontrol - sensitivity
The effects of stale seedbed preparations and several weed control methods on the emergence of weeds in lettuce were studied. The specific goal was to evaluate the use of a stale seedbed in combination with chemical or mechanical weed control methods in the field. Depending on location and year, stale seedbed preparations followed by weed control prior to planting reduced the amount of weeds during crop growth by 43¿83%. Control of the emerged seedlings after a stale seedbed preparation was more effective with glyphosate than with a rotary harrow. Covering the rotary harrow during control to prevent light reaching the soil improved its effect on the weed density during crop growth in two of 3 years. Radiation with far red light (FR) did not reduce the number of emerging weeds in this study. Mechanical control by finger weeder, torsion weeder and hoe was applied without stale seedbed preparations. These measures reduced the weed densities by 88¿99%, compared with the untreated control and were more effective than chemical weed control with carbetamide and chlorpropham. The results show that the stale seedbed technique in combination with mechanical control of emerging weeds can reduce the weed population during crop growth as effectively as chemical control. The technique may therefore help reduce the use of herbicides in lettuce crops in the future.
Low nitrate lettuce cultivations in greenhouses - Optimal control in the presence of measurable disturbances
Graaf, S.C. de - \ 2006
Wageningen University. Promotor(en): Gerrit van Straten, co-promotor(en): Hans Stigter. - [S.l.] : S.n. - ISBN 9085043786 - 138
lactuca sativa - slasoorten - cultuurmethoden - landbouwplantenteelt - teelt onder bescherming - optimalisatiemethoden - operationeel onderzoek - nitraat - wiskundige modellen - binnenklimaat - lactuca sativa - lettuces - cultural methods - crop husbandry - protected cultivation - optimization methods - operations research - nitrate - mathematical models - indoor climate
Inventarisatie uitval in sla
Paternotte, S.J. ; Janse, J. - \ 2005
Aalsmeer : Praktijkonderzoek Plant & Omgeving, Business Unit Glastuinbouw - 23
lactuca sativa - afwijkingen, planten - plantenziektebestrijding - glastuinbouw - slasoorten - bladgroenten - plant disorders - plant disease control - greenhouse horticulture - lettuces - leafy vegetables
In het najaar en de winter wordt in de teelt van sla op een aantal bedrijven wortelafsterving geconstateerd of valt een flink percentage planten uit. Het is niet duidelijk wat de oorzaak is van deze wortelafsterving. Het doel van dit onderzoek is te bepalen welke factoren een rol spelen bij deze wortelafsterving en plantuitval. Daarom zijn een aantal bedrijven bezocht en door middel van vraaggesprekken met telers en vragenlijsten gegevens over de teeltomstandigheden verzameld. Tevens zijn op de bedrijven monsters genomen van planten met wortelafsterving en/of van uitgevallen planten om deze te onderzoeken op de aanwezigheid van ziekteverwekkers. Bij drie adviseurs is informatie met betrekking tot uitval in sla verzameld. Op een oproep zich te melden als er op het bedrijf wegval of wortelafsterving werd geconstateerd hebben slechts 7 telers gereageerd. Uit ziek plantmateriaal van 5 bedrijven is Botrytis of Rhizoctonia geïsoleerd. In plantmateriaal met wortelafsterving afkomstig van de 2 overige bedrijven werden geen ziekteverwekkers gevonden. Het lijkt er het meest op dat een aantal teeltfactoren een rol spelen, waarbij plantactiviteit en waterhuishouding in het wortelmilieu belangrijke factoren zijn.
Romeinse sla (bindsla) : de vollegrondsteelt van A tot Z in beknopte vorm
Wijk, C.A.P. van - \ 2005
Lelystad : Praktijkonderzoek Plant & Omgeving B.V. (PPO publicatie nr. 340) - 21
lactuca sativa - slasoorten - rassen (planten) - cultivars - rassen (taxonomisch) - cultuurmethoden - landbouwplantenteelt - nederland - vollegrondsteelt - lettuces - varieties - races - cultural methods - crop husbandry - netherlands - outdoor cropping
Korte teeltbeschrijving als onderdeel van het project Screening nieuwe gewassen/productinnovatie waarin van relatief onbekende gewassen of innovaties de teeltkansen voor vollegrond in Nederland in kaart worden gebracht. Romeinse sla is een van oudsher bekende slasoort die op beperkte schaal in Nederland werd geteeld en voornamelijk werd gebruikt als stoofgroente. Door de veranderende vraag naar meer hardere, beter versnijbare slasoorten voor gemengde slasoorten, de vraag naar Romeinse sla bij de allochtone bevolkingsgroep en sterkere en resistente eigenschappen van de rassen biedt Romeinse sla de Nederlandse tuinder hernieuwde afzetmogelijkheden
Temperatuurintegratie op heteluchtbedrijven met sla en radijs : onderzoek 2003-2004
Janse, J. ; Houter, G. ; Berkhout, B.A. - \ 2004
Naaldwijk : Praktijkonderzoek Plant & Omgeving, Business Unit Glastuinbouw - 47
lactuca sativa - slasoorten - raphanus sativus - radijsjes - temperatuur - energiebehoud - verwarming - glastuinbouw - lettuces - radishes - temperature - energy conservation - heating - greenhouse horticulture
Door de nieuwe energiewet hebben tuinders die gewassen telen met een lage energiebehoefte te maken met veel hogere energiekosten. Als het totale energiegebruik en de hoge uurpieken in gasverbruik verminderd zouden kunnen worden, zou dit voor de betreffende telers gunstig uit kunnen pakken. In eerder PPO-onderzoek is aangetoond dat toepassing van temperatuurintegratie (TI) bij buisverwarming veel perspectief biedt. Omdat zo’n 80 à 90% van de sla- en radijstelers gebruik maakt van heteluchtverwarming is voor deze groep een apart onderzoek uitgevoerd.
Zeven teelten in praktijk : teelthandleidingen voor biologisch geteelde gewassen
Sukkel, W. ; Leeuwen, W.K. van; Balen, D.J.M. van; Holwerda, J. - \ 2004
Lelystad : Praktijkonderzoek Plant & Omgeving B.V. (PPO 321) - 94
solanum tuberosum - aardappelen - triticum aestivum - tarwe - lactuca sativa - slasoorten - daucus carota - penen - allium porrum - preien - brassica oleracea var. capitata - koolsoorten - brassica oleracea var. gemmifera - spruitjes - kostenanalyse - biologische landbouw - landbouwplantenteelt - akkerbouw - vollegrondsteelt - teelthandleidingen - vollegrondsgroenten - cultuurmethoden - nederland - solanum tuberosum - potatoes - triticum aestivum - wheat - lactuca sativa - lettuces - daucus carota - carrots - allium porrum - leeks - brassica oleracea var. capitata - cabbages - brassica oleracea var. gemmifera - brussels sprouts - cost analysis - organic farming - crop husbandry - arable farming - outdoor cropping - cultivation manuals - field vegetables - cultural methods - netherlands
Teelthandleidingen voor biologisch geteelde consumptieaardappelen, granen, ijsbergsla, peen, prei, sluitkool en spruitkool. Het laatste hoofdstuk van het boek bestaat uit saldoberekeningen voor pootaardappel uit kleigebieden, vroege aardappelen, consumptieaardappelen uit kleigebieden, wintertarwe uit kleigebieden, zomertarwe uit kleigebieden, wintergerst uit kleigebieden, zomergerst uit kleigebieden, haver uit zandgebieden, winterrogge uit zandgebieden, triticale uit zandgebieden, ijssla (zomerteelt), bospeen (zomerteelt), grove peen (b-peen, bewaring), prei (vroeg herfst), witte kool (bewaring), witte kool (industrie), rode kool (bewaring), rode kool (industrie) en spruitkool (middenvroeg).
Deugdelijkheidsonderzoek van 4 middelen tegen valse meeldauw (Bremia lactuca) in sla
Haaring, M.A. ; Slooten, M.A. van - \ 2003
Naaldwijk : Praktijkonderzoek Plant & Omgeving, Business Unit Glastuinbouw - 17
bremia lactucae - lactuca sativa - slasoorten - gewasbescherming - pesticiden - landbouwkundig onderzoek - glastuinbouw - bladgroenten - nederland - lettuces - plant protection - pesticides - agricultural research - greenhouse horticulture - leafy vegetables - netherlands
Najaar 2003 is er door PPO-Business Unit Glastuinbouw in Naaldwijk onderzoek uitgevoerd naar de werking van nieuwe bestrijdingsmiddelen tegen Bremia lactuca in sla. Deze proef is een herhaling van het onderzoek van begin 2003. Naast de 3 middelen uit die betreffende proef is een vierde middel in dit onderzoek opgenomen. Het betreft de plantversterker c.q. bladmeststof Kendal. De middelen die in dit onderzoek zijn getest, zijn voorgedragen door LTO, de slacommissie en het PPO in samenspraak met de betreffende fabrikanten. Dit onderzoek werd gefinancierd door het PT. De betreffende fabrikanten leverden de te testen producten en bijhorende proefontheffingen. Omdat de geteste middelen voor de slateelt geen toelating hebben, worden ze in dit verslag onder code vermeld.
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