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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Recognition of Verticillium effector Ave1 by tomato immune receptor Ve1 mediates Verticillium resistance in diverse plant species
Song, Yin - \ 2017
Wageningen University. Promotor(en): Bart Thomma; Pierre de Wit. - Wageningen : Wageningen University - ISBN 9789463437950 - 231
disease resistance - defence mechanisms - immunity - plant-microbe interactions - plant pathogens - verticillium dahliae - verticillium - tomatoes - solanum lycopersicum - receptors - genes - tobacco - nicotiana glutinosa - potatoes - solanum tuberosum - solanum torvum - humulus lupulus - cotton - gossypium hirsutum - transgenic plants - arabidopsis thaliana - ziekteresistentie - verdedigingsmechanismen - immuniteit - plant-microbe interacties - plantenziekteverwekkers - tomaten - receptoren - genen - tabak - aardappelen - katoen - transgene planten

Plant-pathogenic microbes secrete effector molecules to establish disease on their hosts, whereas plants in turn employ immune receptors to try and intercept such effectors in order to prevent pathogen colonization. Based on structure and subcellular location, immune receptors fall into two major classes; cell surface-localized receptors that comprise receptor kinases (RKs) and receptor-like proteins (RLPs) that monitor the extracellular space, and cytoplasm-localized nucleotide-binding domain leucine-rich repeat receptors (NLRs) that survey the intracellular environment. Race-specific resistance to Verticillium wilt in tomato (Solanum lycopersicum) is governed by the tomato extracellular leucine-rich repeat (eLRR)-containing RLP-type cell surface receptor Ve1 upon recognition of the effector protein Ave1 that is secreted by race 1 strains of the soil-borne vascular wilt Verticillium dahliae. Homologues of V. dahliae Ave1 (VdAve1) are found in plants and in a number of plant pathogenic microbes, and some of these VdAve1 homologues are recognized by tomato Ve1. The research presented in this thesis aims to characterize the role of the tomato cell surface-localized immune receptor Ve1, and its homologues in other diverse plant species, in Verticillium wilt resistance.

Identification of metabolites involved in heat stress response in different tomato genotypes
Paupière, Marine J. - \ 2017
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Arnaud Bovy; Yury Tikunov. - Wageningen : Wageningen University - ISBN 9789463431842 - 168
solanum lycopersicum - tomatoes - genotypes - heat stress - heat tolerance - pollen - metabolomes - metabolites - metabolomics - tomaten - genotypen - warmtestress - hittetolerantie - stuifmeel - metabolomen - metabolieten - metabolomica

Tomato production is threatened by climate change. High temperatures lead to a decrease of fruit set which correlates with a decrease of pollen fertility. The low viability of tomato pollen under heat stress was previously shown to be associated with alterations in specific metabolites. In this thesis, we used untargeted metabolomics approaches to broaden the identification of metabolites affected by heat stress. We assessed the suitability of pollen isolation methods for metabolomics analysis and considered the pitfalls for our further analysis. We explored the developmental metabolomes of pollen and anthers of different tomato genotypes under control and high temperature conditions and identified that microsporogenesis is a critical developmental stage for the production of mature and fertile pollen grain under heat stress. Several metabolites were putatively associated with tolerance to high temperature such as specific flavonoids, polyamines and alkaloids. These metabolites can be further used as markers in breeding programs to develop new genotypes tolerant to high temperatures.

Susceptibility genes : an additional source for improved resistance
Sun, Kaile - \ 2017
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Evert Jacobsen; Yuling Bai. - Wageningen : Wageningen University - ISBN 9789463431415 - 174
solanum tuberosum - potatoes - solanum lycopersicum - tomatoes - genes - susceptibility - plant pathogenic fungi - phytophthora infestans - disease resistance - plant breeding - aardappelen - tomaten - genen - vatbaarheid - plantenziekteverwekkende schimmels - ziekteresistentie - plantenveredeling

Potato is affected by several diseases. Although, resistance can be obtained by introgression of major resistance genes from wild species, this has rarely been durable. Hence, other sources of resistance are highly needed. New research with a focus on loss of function mutations has led to the identification of disease susceptibility (S) genes in plants. The research in this thesis was aimed at the identification and characterization of potato S genes involved in the interaction with Phytophthora infestans and Botrytis cinerea. We selected 11 Arabidopsis thaliana S genes and silenced their potato orthologs by RNAi in the potato cultivar Desiree. The silencing of six genes resulted in resistance to P. infestans. Moreover, silencing of StDND1 reduced the infection of B. cinerea. Microscopic analysis showed that spore attachment and/or germination of P. infestans and B. cinerea was hampered on the leaf surface of StDND1-silenced potato plants. On StDMR1- and StDMR6-silenced potato plants, hyphal growth of P. infestans was arrested by the hypersensitive response-like cell death. Our results demonstrate that impairment of plant S genes may open a new way for breeding potatoes with resistance to pathogens like P. infestans and B. cinerea.

CO2 uit buitenlucht
Weel, P.A. van; Vanthoor, B.H.E. - \ 2016
Wageningen UR Glastuinbouw (Rapport GTB 1423) - 32 p.
glastuinbouw - kooldioxide - ventilatie - freesia - tomaten - greenhouse horticulture - carbon dioxide - ventilation - tomatoes
The supply of additional CO2 in a greenhouse will be restricted in the future. The concentration in outside air has risen above 400 ppm. This may open the possibility to blow this air through the canopy to increase growth. In this project, the vertical CO2 concentration was measured in a vertical plane within to the canopy under different combinations of window opening, the activation of vertical fans and with or without dosing of additional CO2. For a Freesia and a tomato crop the result was that without CO2 dosing it was possible to maintain a concentration of over 350 ppm in the canopy at 5-10 cm distance from the leaf surface when the ventilation windows were open. Since, this is below outside concentration, additional supply of outside air may be an advantage. When extra CO2 was supplied, a reduction in window opening and the use of a screen increased the concentration between the canopy. The vertical distribution of CO2 within the canopy was never a problem. It can be concluded that the crop resistance to take up CO2 for a tomato and freesia crop is small and with respect to the other CO2 resistances, the crop resistance can be neglected. A positive effect of the use of vertical fans or the use of high pressure misting in the tomato greenhouse was not found, due to the strategy to keep the ventilation windows wide open. The concentration at 5-10 cm distance from the leaf is not necessarily the same concentration around the stomata because of boundary layer resistance. The effect of the boundary layer resitance on CO2 uptake is described in the report of Plant Dynamics called “Effecten van grenslaagweerstand op de fotosynthese bij tomaat en Freesia”.
Vochtbeheersing in kassen en terugwinning van latente energie : Een verkenning naar vochtbeheersing in kassen en de mogelijkheden van het terugwinnen van de energie die opgesloten zit in de gewasverdamping
Weel, P.A. van; Zwart, H.F. de; Voogt, J.O. - \ 2016
Wageningen UR Gastuinbouw (Rapport GTB 1421) - 76 p.
kassen - kastechniek - tomaten - glastuinbouw - ontvochtiging - energiegebruik - energiebesparing - ventilatie - greenhouses - greenhouse technology - tomatoes - greenhouse horticulture - dehumidification - energy consumption - energy saving - ventilation
Dehumidification of a greenhouse by ventilation increases the energy input with 8-10 m3/m2.year of natural gas to compensate the heat losses. This study shows different methods to reduce those energy losses. A 25% reduction in ventilation is obtained by using heat exchangers connected to plastic distribution ducts or by using the Ventilationjet system. The sensible heat from the exhaust air can be used to heat the incoming outside air to greenhouse temperature. Heat exchangers with 100% efficiency to do that are available. The latent heat included in the water vapour leaving the greenhouse can be recovered by means of a condensating wall. A good working priciple is the Dewpoint Heat Exchanger in which outside air is wettened to reach the lowest possible temperature and then used to cool down the greenhouse air far below the temperature where condensation begins. The recovered latent heat must be stored in a water tank to use it in the heating pipes. Another approach is to skip ventilation and use a set of a cold and warm heat exchanger connected to a heat pump or to use a salt water absorber. The absorber opens the possibility to use solar or wind energy to dehumidify the greenhouse and collect 100% of the sensible and latent heat.
Stress speelt een belangrijke rol : inzicht in koploosheid groeit door gezamenlijk onderzoek
Groot, S.P.C. ; Kierkels, T. ; Heuvelink, E. - \ 2016
Onder Glas 13 (2016)8. - p. 30 - 31.
tuinbouw - groenten - landbouwkundig onderzoek - groeistoornis - plantenontwikkeling - verlichting - tomaten - capsicum - brassica - gypsophila - stresstolerantie - temperatuur - horticulture - vegetables - agricultural research - failure to thrive - plant development - lighting - tomatoes - stress tolerance - temperature

Jonge tomaten- en paprikaplanten, maar ook een aantal andere gewassen, houden soms opeens op met groeien. Koploosheid was lange tijd een lastig maar zeer slecht begrepen fenomeen. De laatste jaren is het inzicht in een stroomversnelling gekomen. In ieder geval is het aantal mogelijke oorzaken drastisch ingeperkt.
Susceptibility pays off: insights into the mlo-based powdery mildew resistance
Appiano, Michela - \ 2016
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Yuling Bai; Anne-Marie Wolters. - Wageningen : Wageningen University - ISBN 9789462579484 - 265
solanum lycopersicum - tomatoes - disease resistance - susceptibility - oidium neolycopersici - genes - gene expression - genomics - molecular breeding - plant breeding - tomaten - ziekteresistentie - vatbaarheid - genen - genexpressie - genomica - moleculaire veredeling - plantenveredeling

Powdery mildew (PM) is a worldwide-occurring plant disease caused by ascomycete fungi of the order Erysiphales. A conspicuous number of plant species are susceptible to this disease, the occurrence of which is increasing due to the influence of climate change. Symptoms are easy to recognize by the powdery whitish fungal structures growing on the surface of plant organs. Severe infections cause significant losses in crops, such as tomato, cucumber and wheat, as well as in ornamentals, like rose and petunia. Accordingly, breeding crops with a robust immunity to this disease is of great economic importance.

A significant step in this direction was the discovery of mlo (mildew locus o) mutant alleles of the barley HvMlo gene, which are responsible for the non-race specific resistance to the barley PM pathogen, Blumeria graminis f.sp. hordei (Bgh). During the years, this recessively inherited resistance was observed to be durable, contrary to the short life-span of resistances conferred by dominant resistance (R-) genes used in barley breeding programs. Studies on the histological mechanisms of the mlo-based resistance showed that the PM pathogen was stopped during penetration of the cell wall by the formation of a papilla. This structure prevents the formation of the feeding structure of the pathogen, called a haustorium.

After sequencing many plant genomes, we are discovering that MLO genes are not only typical of this cereal, but are ubiquitously present in higher plant species in multiple copies per species, forming a gene family. The impairment of some members of a number of ever increasing plant species lead to broad-spectrum resistance towards their adapted PM pathogens. For example, in tomato the ol-2 gene, naturally harbored by the cherry tomato Solanum lycopersicum var. cerasiforme, represents the loss-of-function allele of the SlMLO1 gene, conferring resistance to the PM pathogen Oidium neolycopersici (On). Consequently, the use of mlo mutants represents a suitable alternative to the classical use of R-genes in breeding programs.

In Chapter 2, we describe the in silico identification of the complete tomato SlMLO gene family using the available information in the SOL genomic network database. In total, 16 tomato SlMLO members were cloned from leaf, root, flower and fruit of the susceptible tomato cv. Moneymaker to confirm the sequences retrieved from the database and to verify their actual expression in these tissues. We observed the presence of various types of splicing variants, although their possible functional meaning has not been investigated. Motif analyses of each of the translated protein sequences and phylogenetic studies highlighted, on one hand, amino acid stretches that characterize the whole MLO family, and, on the other hand, stretches conserved in MLO homologs that are phylogenetically related. Following a gene expression study upon On inoculation, we identified members of the SlMLO family that are upregulated few hours after pathogen challenge. Except SlMLO1, none of the three newly identified homologs in clade V, thus phylogenetically close to SlMLO1, are induced. Interestingly, two homologs, each found in different clades, are upregulated similarly to SlMLO1. Using an RNAi approach, we silenced the additional clade V-SlMLO homologs, namely SlMLO3, SlMLO5 and SlMLO8, to investigate their possible role in PM resistance. We observed that none of these homologs if individually silenced, leads to PM resistance. However, if SlMLO5 and SlMLO8 are silenced together with SlMLO1, a significantly higher level of resistance is achieved compared to plants carrying the ol-2 allele. The role of SlMLO3 could not be verified. We, therefore, concluded that there are three SlMLO genes in tomato unevenly contributing to the PM disease, of which SlMLO1 has a major role.

Chapter 3 focuses on the components of the tomato mlo-based resistance. In Arabidopsis, it is known that four members of the SNARE protein family, involved in membrane fusion, are involved in mlo-based resistance. In this chapter, we focused on the identification of tomato homologs of the Arabidopsis syntaxin PEN1 (AtSYP121). Among the group of syntaxins identified in tomato, two were closely related to each other and also to AtPEN1, denominated SlPEN1a and SlPEN1b. Another Arabidopsis syntaxin that shows a high level of homology with PEN1, called SYP122, was also found to group together with the newly identified SlPEN1 genes. However, the role of SYP122 in plant immunity was not shown in literature. After obtaining individual silencing RNAi constructs, we transformed the resistant ol-2 line, and we challenged the obtained transformants with the adapted PM On, and the non-adapted Bgh. Interestingly, we observed a significant On growth and an enhanced Bgh cell entry only in SlPEN1a silenced plants but not in SlPEN1b silenced ones. We performed a protein alignment of tomato and Arabidopsis functional and non-functional PEN sequences. The presence of three differently conserved non-synonymous amino-acid substitutions is hypothesised to be responsible for the specialization in plant immune function.

In Chapter 4 and Chapter 5, we build up a body of evidence pointing to the fact that the function of the MLO susceptibility genes is highly conserved between monocot and dicot plant species.

In Chapter 4 we started by identifying and functionally characterizing two new MLO genes of Solanaceous crops affected by the PM disease, tobacco (Nicotiana tabacum) and eggplant (Solanum melongena). We named them NtMLO1 and SmMLO1 in the respective species, as they are the closest homologs to tomato SlMLO1. By overexpressing these genes in the resistant ol-2 line, we obtained transgenic plants that were susceptible to the PM pathogen On. This finding demonstrates that both heterologous MLO proteins can rescue the function of the impaired ol-2 allele in tomato. In addition, we found in tobacco NtMLO1 an amino acid (Q198) of critical importance for the susceptibility function of this protein.

In Chapter 5, we used the same approach adopted in Chapter 4 to show that other MLO proteins of more distant dicot species, like pea PsMLO1, can rescue the loss-of-function of the tomato ol-2 allele. And finally, we stretched this concept also to monocot MLO proteins, using barley HvMlo. While performing these experiments, we could verify that the function of the monocot and dicot susceptibility MLO proteins does not rely on the presence of class-specific conservation. The latter can be the reason for the phylogenetic divergence, placing monocot MLO proteins in clade IV and dicot MLO proteins in clade V of the phylogenetic MLO tree. However, functional conservation might depend on crucial shared amino acids of clade IV and V MLO proteins. Therefore, we also conducted a codon-based evolutionary analysis that resulted in the identification of 130 codons under negative selection, thus strongly maintained during evolution.

In Chapter 6 we introduce the PM disease in cucumber caused by Podosphaera xanthii (Px). We cloned the candidate susceptibility gene for PM in cucumber, CsaMLO8, from susceptible and resistant genotypes. The latter was described as an advanced cucumber breeding line characterized by hypocotyl resistance. In this line, we found the presence of aberrant splicing variants of the CsaMLO8 mRNA due to the insertion in its corresponding genomic region of a Class LTR retrotransposon. Heterologous expression of the wild-type cucumber allele in the tomato ol-2 line restored its PM susceptibility, while the heterologous expression of the aberrant protein variant failed to do so. This finding confirms that the resistance of the advanced cucumber breeding line is due to the disruption of the coding region of this gene. We also showed that the expression of CsaMLO8 in the susceptible genotype is induced by Px in hypocotyl tissue, but not in cotyledon or leaf. Finally, by examination of the resequencing data of a collection of 115 cucumber accessions, we found the presence of the TE-containing allele in 31 of them among which a wild cucumber accession that might have been used in breeding programs to obtain resistance to the PM disease in cucumber.

In Chapter 7 a novel loss-of-function allele of the SlMLO1 gene is described, designated m200. This allele was found in a resistant plant (M200) from a mutagenized tomato Micro-Tom (MT) population obtained with the chemical mutagen ethyl methanesulfonate (EMS). The m200 mutation corresponds to a nucleotide transversion (T à A) which results in a premature stop codon. The length of the predicted SlMLO1 protein in the M200 plant is only 21 amino acids, thus much shorter than the predicted protein of the previously described ol-2 allele, consisting of 200 amino acids. Thanks to the development of a High-Resolution Melting (HRM) marker designed to detect the m200 mutation, we observed that this allele confers recessively inherited resistance in backcross populations of the resistant M200 plant with MT and Moneymaker. Histological study showed that the resistance of the m200 mutant is associated with papilla formation. Finally, we compared the rate of On penetration in epidermal cells of m200 plants with the one of plants carrying the ol-2 allele and the transgenic plants in which multiple SlMLO homologs were silenced, generated in Chapter 2.

Ultimately, in Chapter 8 the results of the previous chapters are discussed in the context of 1) practical applications in breeding programs aimed at introducing the mlo-based resistance in new crops, 2) possible research aimed at unraveling the function of the MLO protein and 3) the role of other SNARE proteins.

Het Nieuwe Gewas : sturen van de plantvorm voor verhoogde lichtbenutting
Gelder, Arie de; Janse, Jan ; Warmenhoven, Mary - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1407) - 62
tomaten - solanum lycopersicum - kasgewassen - glasgroenten - glastuinbouw - energiebesparing - plantenontwikkeling - gewasteelt - licht - tomatoes - greenhouse crops - greenhouse vegetables - greenhouse horticulture - energy saving - plant development - crop management - light
Wageningen UR Greenhouse horticulture searched in the “The New Crop” project for the crop structure that best contributes to the goal of energy-efficient production and therefore energy saving, by removing 33, 44 or 55% of the leaves at a young stage. On October 10th 2014 the experiment started with topped plants of the tomato variety Brioso grafted on Maxifort. Dry matter production was lowest in the very open crop, however partitioning to the fruits was highest in that treatment. Therefore, this crop produced in the winter under assimilation lighting most. In summer, the standard treatment was the best and the production in this treatment was highest. The plants in the very open treatment were shorter and had smaller leaves than the plants of the standard treatment. This is might be due to a different red: far red ratio of light in the crop. Leaf picking at a young stage contributes to better distribution of assimilates to the fruits. This can be used as a crop management measure as the plant in winter develops too much leaves. The project was funded by the Dutch energy transition program “Kas als Energiebron”.
Plantmonitoring op basis van fotosynthese sensoren : ontwikkelen en testen van sensoren
Dieleman, Anja ; Bontsema, Jan ; Jalink, Henk ; Snel, Jan ; Kempkes, Frank ; Voogt, Jan ; Pot, Sander ; Elings, Anne ; Jalink, Vincent ; Meinen, Esther - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1405) - 86
teelt onder bescherming - glastuinbouw - kastechniek - sensors - fotosynthese - kooldioxide - energie - energiebesparing - verlichting - kunstlicht - kunstmatige verlichting - ventilatie - kunstmatige ventilatie - fluorescentie - tomaten - solanum lycopersicum - protected cultivation - greenhouse horticulture - greenhouse technology - photosynthesis - carbon dioxide - energy - energy saving - lighting - artificial light - artificial lighting - ventilation - artificial ventilation - fluorescence - tomatoes
The basic process for crop growth and production is photosynthesis. Measuring crop photosynthesis is therefore important to monitor the status of the crop and whether the greenhouse climate is set to the needs of the crop. In this project, two monitoring systems for crop photosynthesis were developed and tested. (1) The crop photosynthesis monitor is a soft sensor that can calculate the CO2 uptake of an entire crop. The basis for these calculations are the balance between CO2 supply and CO2 loss via ventilation and crop photosynthesis. By measuring the CO2 concentration and humidity inside and outside the greenhouse, the crop photosynthesis can be calculated. (2) The CropObserver is a fluorescence sensor that measures the light use efficiency of photosynthesis of a large crop area (3 x 3 m2). The crop receives light pulses from a laser in the top of the greenhouse, the sensor measures the fluorescence signal of the crop. Both sensors were tested in a tomato crop in 2014 with promising results. The sensors functioned without problems and delivered patterns of daily photosynthesis which matched the reference measurements reasonably well up to well.
White root tips supply plants with oxygen, water and nutrients : healthy roots are fundamental for a healthy plant
Heuvelink, E. ; Kierkels, T. - \ 2016
In Greenhouses : the international magazine for greenhouse growers 5 (2016)3. - ISSN 2215-0633 - p. 44 - 45.
tuinbouw - glastuinbouw - worteloppervlak - wortelharen - wortels - wateropname (planten) - voedselopname - opname (uptake) - calcium - tomaten - pythium - plantenontwikkeling - horticulture - greenhouse horticulture - rhizoplane - root hairs - roots - water uptake - food intake - uptake - tomatoes - plant development
The main, most important function of roots belonging to horticultural crops is the uptake of water and nutrients. Healthy roots are essential for a healthy plant. After all, if the uptake of water and nutrients is not functioning properly, then other aspects also leave a lot to be desired
Parthenocarp ras kan oplossing zijn bij vruchtzettingsproblemen
Heuvelink, E. ; Kierkels, T. - \ 2016
Onder Glas 13 (2016)5. - p. 12 - 13.
tuinbouw - glastuinbouw - groenten - tomaten - paprika's - komkommers - fotosynthese - vruchtzetting - groeiregulatoren - parthenocarpie - cytokininen - gibberellinen - auxinen - horticulture - greenhouse horticulture - vegetables - tomatoes - sweet peppers - cucumbers - photosynthesis - fructification - growth regulators - parthenocarpy - cytokinins - gibberellins - auxins
Samen met een goede fotosynthese staat voldoende vruchtzetting op de gedeelde eerste plaats bij het welslagen van de teelt van vruchtgroenten. Het zou echter veel gemakkelijker zijn als die bevruchting helemaal niet nodig was. Bij verscheidene gewassen is parthenocarpie inmiddels gewoon, maar bij een belangrijk deel blijft het zaak de juiste omstandigheden voor vruchtzetting te creëren.
2SaveEnergy-Gewächshaus- Produktion und Energieverbrauch
Kempkes, F.L.K. ; Janse, J. - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1404) - 46 p.
greenhouse horticulture - greenhouse crops - greenhouse technology - energy saving - energy consumption - isolation - isolation techniques - tomatoes - solanum lycopersicum - glastuinbouw - kasgewassen - kastechniek - energiebesparing - energiegebruik - isolatie - isolatietechnieken - tomaten
Energy savings through a greenhouse cover of insulation glass requires a large investment. In the search for a cheaper alternative by a consortium of companies consisting of VDH Plastic Greenhouses, Van der Valk Horti Systems, AGC Chemicals Europe en Boal Systems a Glass-Film-greenhouse cover, better known as the 2SaveEnergy greenhouse concept was realized in summer 2014. The combination of clear glass with a diffuse ETFE film and a double screen mounted at a distance of only a few centimetres, in the year 2015, resulted in a low energy consumption and a better than expected good tomato production. During cultivation, the principles of the new cultivation methods were used. With respect to the common practice, the energy consumption was more than 50% lower at a minimum equal production.
Teelt en energie 2SaveEnergy kas
Kempkes, F.L.K. ; Janse, J. - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1402) - 42 p.
glastuinbouw - kasgewassen - kastechniek - energiebesparing - energiegebruik - isolatie - isolatietechnieken - tomaten - solanum lycopersicum - greenhouse horticulture - greenhouse crops - greenhouse technology - energy saving - energy consumption - isolation - isolation techniques - tomatoes
Energy savings through a greenhouse cover of insulation glass requires a large investment. In the search for a cheaper alternative by a consortium of companies consisting of VDH Plastic Greenhouses, Van der Valk Horti Systems, AGC Chemicals Europe en Boal Systems a Glass-Film-greenhouse cover, better known as the 2SaveEnergy greenhouse concept was realized in summer 2014. The combination of clear glass with a diffuse ETFE film and a double screen mounted at a distance of only a few centimetres, in the year 2015, resulted in a low energy consumption and a better than expected good tomato production. During cultivation, the principles of the new cultivation methods were used. With respect to the common practice, the energy consumption was more than 50% lower at a minimum equal production.
Heat stress tolerance responses in developing tomato anthers
Bita, Elena - \ 2016
Wageningen University. Promotor(en): Gerco Angenent, co-promotor(en): Christian Bachem. - Wageningen : Wageningen University - ISBN 9789462577701 - 109 p.
tomatoes - solanum lycopersicum - anthers - heat stress - stress tolerance - heat tolerance - heat shock - transcriptomics - reproductive performance - gene expression profiling - meiosis - tomaten - helmknoppen - warmtestress - stresstolerantie - hittetolerantie - hitteshock - transcriptomica - voortplantingsvermogen - genexpressieprofilering - meiose

Global warming already has and will significantly impact crop productivity and yield in the near future. In order to meet the forecasted requirements of the future agricultural production, a proper assessment of crops environmental stress tolerance needs to be designed and implemented, from the laboratory to field. Genetic variation in the ability of tomatoes to set fruit under high temperature conditions has made selection for heat tolerance possible and multiple opportunities for improvement exist, as tolerance to high temperatures is a multi-genic character involving a complex network of chaperones and other protective proteins acting together to defend the cells from heat injury. Breeding programs involved in the development of heat tolerant cultivars should identify and make use of such tolerance traits already available in collected or wild germplasm.

The goal of this thesis was to characterize the response to high temperatures in meiotic tomato anthers with contrasting responses to heat and to identify genes that could be related to thermo-tolerance mechanisms during gamete development. Several molecular tools such as transcriptomic profiling by cDNA-AFLP and microarray analysis, RT-PCR or in situ RNA hybridisation were used to achieve this goal.

The second chapter reviews the effects of heat stress on reproductive flower development, candidate tolerance pathways and methods for production of heat tolerant crops.

The third chapter provides a general overview of the expression changes occurring in the developing anthers of a sensitive tomato genotype following exposure to a (short and) moderate high temperature stress (MHS). Using a combination of cDNA-AFLP, RT-PCR, and in situ RNA hybridisation, we characterized and verified the general transcriptional response to heat of tomato plants. Our results revealed that approximately 1% of the examined transcript-derived fragments exhibit alterations in expression pattern and the majority of these were down-regulated The putative functions associated with the genes identified by cDNA-AFLP indicated involvement of heat shock, metabolism, antioxidant and developmental processes. Based upon the observed transcriptional changes in response to MHS and on literature sources, we identified a number of candidate transcripts to be involved in heat-tolerance. The spatial expression of several such candidate genes was further examined using in situ RNA hybridisation and this showed that the investigated genes are expressed in the tapetum or/and in developing microspores. Furthermore, the expression of several candidate genes has been quantified by RT-PCR in additional genotypes with different degrees of heat tolerance. The results suggested a correlation between gene expression levels, pollen germination rates and tolerance to heat (Chapter 4).

In the fourth chapter we proceeded to profile the response to heat of meiotic anthers in a tolerant and a sensitive tomato genotype and investigated the expression of the identified candidate genes in several pairs of contrasting genotypes. Using microarray analysis (for an extensive overview of the meiotic response to heat) and RT-PCR, we were able to clearly distinguish differential responses of the tolerant genotype. After 2h of moderate heat stress, the heat-tolerant genotype exhibits fewer transcriptional changes than the heat-sensitive genotype. In the heat-tolerant genotype, the majority of changes in gene expression is represented by up-regulation, while in the heat-sensitive genotype there is a general trend to down-regulate gene expression soon after MHS. Moreover, the heat-tolerant genotype also shows a different level of constitutive gene expression profiles when compared to the heat-sensitive genotype indicating a difference in genetic adaptation with regards to increased temperatures. The putative functions associated with the genes identified by microarray profiling indicate involvement of heat shock, antioxidant, metabolic, and cell development pathways. Based upon the observed differences in response to MHS we selected a number of candidate transcripts involved in heat-tolerance and confirmed their expression pattern in different tomato genotypes with contrasting responses to heat. The results suggested that the candidate genes are involved in the activation of protection mechanisms in the tomato anthers during moderate heat stress and, could therefore contribute to normal growth and development of the male gametophyte and implicitly a successful fruit set under adverse temperatures.

In the fifth chapter we tested the hypothesis that heat tolerance is associated with maintenance of organ identity, fertility and lower ABA levels during heat stress (for several tomato genotypes) and analysed the dynamics of ABA accumulation under temperature stress in several tomato genotypes with contrasting responses to heat. Furthermore, pollen germination tests were performed and additional physiological aspects of anther development for each genotype were analysed as well. The general trend observed was the accumulation of lower relative levels of ABA at the end of the experimental period compared to the initial stages in more tolerant genotypes and of higher levels in the sensitive genotypes. We concluded from these results that the morphological changes in the floral tissues and the overall changes in ABA levels are correlated with the molecular responses under increased temperature in the genotypes analysed. Whether these correlations are causally related is not clear; therefore more research is needed to resolve these issues.

The sixth chapter examines our analysis of the heat stress response in meiotic tomato anthers in a broader scientific context. I discuss the different aspects of our results and present several candidate genes involved in plant thermo-tolerance. In addition, I also discuss the potential involvement of plant growth regulators in plants´ responses to heat stress and suggest various potential follow-up experimental strategies.

Ziekteweerbaarheid verhogen tegen wortelknobbelaaltjes (Meloidogyne spp.)
Kolk, J.P. van der; Voogt, W. ; Streminska, M.A. ; Wurff, A.W.G. van der - \ 2016
- 1 p.
tuinbouw - gewasbescherming - plagenbestrijding - meloidogyne - glastuinbouw - biologische bestrijding - compost - bodemvruchtbaarheid - tomaten - conferenties - biologische landbouw - plaagbestrijding met predatoren - vruchtgroenten - meloidogyne incognita - meloidogyne javanica - aaltjesdodende eigenschappen - plantenparasitaire nematoden - bodemweerbaarheid - horticulture - plant protection - pest control - greenhouse horticulture - biological control - composts - soil fertility - tomatoes - conferences - organic farming - predator augmentation - fruit vegetables - nematicidal properties - plant parasitic nematodes - soil suppressiveness
In de biologische glastuinbouw zijn bodem gebonden ziektes een groot knelpunt. Wortelknobbelaaltjes (Meloidogyne incognita en M. javanica) zijn belangrijke pathogenen die in de vruchtgroententeelt voor problemen zorgen.
Ontwikkeling systeemaanpak meeldauw
Hofland-Zijlstra, J.D. ; Breeuwsma, S.J. ; Noordam, Marianne - \ 2016
- 1 p.
biologische bestrijding - tuinbouw - glastuinbouw - bestrijdingsmethoden - meeldauw - kasproeven - potplanten - tomaten - gerbera - rosaceae - ziekteresistentie - biological control - horticulture - greenhouse horticulture - control methods - mildews - greenhouse experiments - pot plants - tomatoes - disease resistance
Doel van dit onderzoek is het ontwikkelen van een systeemaanpak voor de beheersing van meeldauw door de inzet van groene producten (laag-risico profiel) die een bijdrage leveren aan het versterken van natuurlijke afweerreacties. Poster van het PlantgezondheidEvent 2016.
Plaagbestrijding met omnivore roofwantsen
Messelink, G.J. ; Leman, A. ; Elfferich, Caroline ; Kruidhof, H.M. - \ 2016
Wageningen : Wageningen UR Glastuinbouw - 1 p.
bestrijdingsmethoden - tuinbouw - glastuinbouw - plagenbestrijding - reduviidae - tomaten - gerbera - rosaceae - trialeurodes vaporariorum - thrips - tuta - cyrtopeltis tenuis - control methods - horticulture - greenhouse horticulture - pest control - tomatoes
Het doel van dit project is om tot robuuste bestrijdingsmethoden van meerdere plagen te komen door inzet van omnivore roofwantsen in de gewassen tomaat, gerbera en roos, waarbij eigenschappen van het gewas en de omgeving worden aangepast voor een optimale vestiging en plaagbestrijding met minimale risico’s op gewasschade. De bestrijding richt zich op de plagen witte vlieg (gerbera, roos, tomaat) en Echinothrips (gerbera en roos) en op de invasieve plagen Tuta aboluta en Nesidiocoris tenuis (tomaat), maar is ook van nut voor andere plagen zoals spint, mineervlieg en bladluis. Poster van het PlantgezondheidEvent 2016.
Nederlandse handelsbalans tomaten
Jukema, G.D. - \ 2016
LEI Wageningen UR (Factsheet / LEI Wageningen UR 2016-012j) - 2 p.
handelsbalans - export - tomaten - nederland - balance of trade - exports - tomatoes - netherlands
In 2014 is de export van tomaten met 8% gestegen. De import is met ongeveer hetzelfde per-centage gedaald. Al met al verbeterde de handelsbalans voor tomaten met 12% tot € 1,2 mld. De belangrijkste afnemer van Nederlandse tomaten is en blijft Duitsland. Ongeveer de helft van alle tomaten ging naar onze oosterburen. Ook is Nederland op de Duitse markt hofleverancier. Voor 2015 wordt een stijging van de Nederlandse exportwaarde van tomaten geraamd.
Genetics and regulation of combined abiotic and biotic stress tolerance in tomato
Kissoudis, C. - \ 2016
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Gerard van der Linden; Yuling Bai. - Wageningen : Wageningen University - ISBN 9789462576568 - 212 p.
solanum lycopersicum - tomatoes - disease resistance - stress tolerance - defence mechanisms - plant diseases - abiotic injuries - stress response - phenotypic variation - genetic analysis - plant breeding - salt tolerance - tomaten - ziekteresistentie - stresstolerantie - verdedigingsmechanismen - plantenziekten - abiotische beschadigingen - stressreactie - fenotypische variatie - genetische analyse - plantenveredeling - zouttolerantie

Projections on the impact of climate change on agricultural productivity foresee prolonged and/or increased stress intensities and enlargement of a significant number of pathogens habitats. This significantly raises the occurrence probability of (new) abiotic and biotic stress combinations. With stress tolerance research being mostly focused on responses to individual stresses, our understanding of plants’ ability to adapt to combined stresses is limited.

In an attempt to bridge this knowledge gap, we hierarchized in chapter 1 existing information on individual abiotic or biotic stress adaptation mechanisms taking into consideration different anatomical, physiological and molecular layers of plant stress tolerance and defense. We identified potentially crucial regulatory intersections between abiotic and biotic stress signalling pathways following the pathogenesis timeline, and emphasized the importance of subcellular to whole plant level interactions by successfully dissecting the phenotypic response to combined stress. We considered both explicit and shared adaptive responses to abiotic and biotic stress, which included amongst others R-gene and systemic acquired resistance as well as reactive oxygen species (ROS), redox and hormone signalling, and proposed breeding targets and strategies.

In chapter 3 we focused on salt stress and powdery mildew combination in tomato, a vegetable crop with a wealth of genetic resources, and started with a genetic study. S. habrochaites LYC4 was found to exhibit resistance to both salt stress and powdery mildew. A LYC4 introgression line (IL) population segregated for both salt stress tolerance and powdery mildew resistance. Introgressions contributing to salt tolerance, including Na+ and Cl- accumulation, and powdery mildew resistance were precisely pinpointed with the aid of SNP marker genotyping. Salt stress (100mM NaCl) combined with powdery mildew infection increased the susceptibility of the population to powdery mildew in an additive manner, while decreasing the phenotypic variation for this trait. Only a few overlapping QTLs for disease resistance and salt stress tolerance were identified (one on a short region at the top of Chromosome 9 where numerous receptor-like kinases reside). Most genetic loci were specific for either salt stress tolerance or powdery mildew resistance indicating distinct genetic architectures. This enables genetic pyramiding approaches to build up combined stress tolerance.

Considering that abiotic stress in nature can be of variable intensities, we evaluated selected ILs under combined stress with salinity ranging from mild to severe (50, 100 and 150mM NaCl) in chapter 4. Mild salt stress (50mM) increased powdery mildew susceptibility and was accompanied by accelerated cell death-like senescence. On the contrary, severe salt stress (150mM) reduced the disease symptoms and this correlated with leaf Na+ and Cl- content in the leaves. The effects of salt stress on powdery mildew resistance may be dependent on resistance type and mechanisms. Near Isogenic Lines (NILs) that carry different PM resistance genes (Ol-1 (associated with slow hypersensitivity response, HR), ol-2 (an mlo mutant associated with papilla formation) and Ol-4 (an R gene associated with fast HR) indeed exhibited differential responses to combined stress. NIL-Ol-1 resembled the LYC4 ILs response, while NIL-ol-2 and NIL-Ol-4 maintained robust resistance and exhibited no senescence symptoms across all combinations, despite the observed reduction in callose deposition in NIL-ol-2. Increased susceptibility, senescence and fitness cost of NIL-Ol-1 under combined stress coincided with high induction of ethylene and jasmonate biosynthesis and response pathways, highly induced expression of cell wall invertase LsLIN6, and a reduction in the expression of genes encoding for antioxidant enzymes. These observations underlined the significance of stress intensity and mechanism of resistance to the outcome of salt stress and powdery mildew combination, underscoring the involvement of ethylene signalling to the susceptibility response under combined stress.

To examine the significance of hormone signalling in combined stress responses we evaluated crosses of tomato hormone mutants notabilis (ABA-deficient), defenseless1 (JA-deficient) and epinastic (ET overproducer) with NIL-Ol-1, NIL-ol-2 and NIL-Ol-4 in chapter 5. The highly pleiotropic epinastic mutant increased susceptibility of NIL-Ol-1, but decreased the senescence response under combined stress, and resulted in partial breakdown of NIL-ol-2 resistance, accompanied by reduced callose deposition. The effects of ET overproduction on susceptibility were more pronounced under combined stress. ABA deficiency in notabilis on the other hand greatly reduced susceptibility of NIL-Ol-1under combined stress at the expense of stronger growth reduction, and induced ROS overproduction. Partial resistance breakdown in the ol-2xnotabilis mutant accompanied by reduced callose deposition was observed, and this was restored under combined stress. Jasmonic acid deficiency phenotypic effects in defenseless mutants were subtle with modest increase in susceptibility for NIL-Ol-1 and NIL-ol-2. For NIL-ol-2 this increased susceptibility was reverted under combined stress. NIL-Ol-4 resistance remained robust across all mutant and treatment combinations. These results highlight the catalytic role of ET and ABA signalling on susceptibility and senescence under combined stress, accentuating concomitantly the importance of signalling fine tuning to minimize pleiotropic effects.

The potential of exploiting transcription factors to enhance tolerance to multiple stress factors and their combination was investigated in chapter 6 through the identification and functional characterization of tomato homologues of AtWRKYs 11, 29, 48, 70 and 72. Thirteen tomato WRKY homologues were identified, of which 9 were overexpressed (using transformation with A. tumefaciens) and 12 stably silenced via RNAi in tomato cultivar Money Maker (MM). SlWRKY11-OE and SlWRKY23-OE overexpressors and RNAi lines of SlWRKY7 and SlWRKY9 showed both increased biomass and relative salt tolerance. SlWRKY6-OE exhibited the highest relative salt stress tolerance, but had strongly decreased growth under control conditions. Exceptional phenotypes under control conditions were observed for SlWRKY10-OE (stunted growth) and SlWRKY23-RNAi (necrotic symptoms). These phenotypes were significantly restored under salt stress, and accompanied by decreased ROS production. Both lines exhibited increased resistance to powdery mildew, but this resistance was compromised under salt stress combination, indicating that these genes have important functions at the intersection of abiotic and biotic stress adaptation. SlWRKY23 appears to have a key regulatory role in the control of abiotic stress/defense and cell death control.

Experimental observations are critically discussed in the General Discussion with emphasis on potential distinctive responses in different pathosystems and abiotic and biotic stress resistance mechanisms as well as genetic manipulations for effectively achieving combined stress tolerance. This includes deployment of individual common regulators as well as pyramiding of non-(negatively) interacting components such as R-genes with abiotic stress resistance genes, and their translation potential for other abiotic and biotic stress combinations. Understanding and improving plant tolerance to stress combinations can greatly contribute to accelerating crop improvement towards sustained or even increased productivity under stress.

De consument wil smaak...maar welke smaak?
Verkerke, W. ; Labrie, C.W. - \ 2016
Kas Magazine / TuinbouwCommunicatie 2016 (2016)01. - ISSN 1878-8408 - p. 20 - 22.
tuinbouw - tomaten - paprika's - meloenen - aardbeien - smaak - consumentenpanels - smaakonderzoek - marketing - modellen - horticulture - tomatoes - sweet peppers - melons - strawberries - taste - consumer panels - taste research - models
Marktgericht produceren begint bij de smaak. Maar van welke smaak houdt de consument? Wageningen UR Glastuinbouw ontwikkelde een meetmodel voor de smaak van tomaten, paprika's en meloenen en werkt nu aan de aardbei. Bovendien brengt het de smaak van consumententypen in kaart. "Als je de smaakvoorkeur van consumenten kent, dan kun je pas écht produceren voor de markt."
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