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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    Salt stress and fluctuating light have separate effects on photosynthetic acclimation, but interactively affect biomass
    Zhang, Yuqi ; Kaiser, Elias ; Marcelis, Leo F.M. ; Yang, Qichang ; Li, Tao - \ 2020
    Plant, Cell & Environment (2020). - ISSN 0140-7791 - 15 p.
    fluctuating light - light acclimation - photosynthesis - salt stress - stomatal conductance - tomato

    In nature, soil salinity and fluctuating light (FL) often occur concomitantly. However, it is unknown whether salt stress interacts with FL on leaf photosynthesis, architecture, biochemistry, pigmentation, mineral concentrations, as well as whole-plant biomass. To elucidate this, tomato (Solanum lycopersicum) seedlings were grown under constant light (C, 200 μmol m−2 s−1) or FL (5–650 μmol m−2 s−1), in combination with no (0 mM NaCl) or moderate (80 mM NaCl) salinity, for 14 days, at identical photoperiods and daily light integrals. FL and salt stress had separate effects on leaf anatomy, biochemistry and photosynthetic capacity: FL reduced leaf thickness as well as nitrogen, chlorophyll and carotenoid contents per unit leaf area, but rarely affected steady-state and dynamic photosynthetic properties along with abundance of key proteins in the electron transport chain. Salt stress, meanwhile, mainly disorganized chloroplast grana stacking, reduced stomatal density, size and aperture as well as photosynthetic capacity. Plant biomass was affected interactively by light regime and salt stress: FL reduced biomass in salt stressed plants by 17%, but it did not affect biomass of non-stressed plants. Our results stress the importance of considering FL when inferring effects of salt-stress on photosynthesis and productivity under fluctuating light intensities.

    The genetic and functional analysis of flavor in commercial tomato : the FLORAL4 gene underlies a QTL for floral aroma volatiles in tomato fruit
    Tikunov, Yury M. ; Roohanitaziani, Raana ; Meijer-Dekens, Fien ; Molthoff, Jos ; Paulo, Joao ; Finkers, Richard ; Capel, Iris ; Carvajal Moreno, Fatima ; Maliepaard, Chris ; Nijenhuis-de Vries, Mariska ; Labrie, Caroline W. ; Verkerke, Wouter ; Heusden, Adriaan W. van; Eeuwijk, Fred van; Visser, Richard G.F. ; Bovy, Arnaud G. - \ 2020
    The Plant Journal (2020). - ISSN 0960-7412
    2-phenylethanol - aroma - flavor - quantitative trait loci - Solanum lycopersicum - tomato - volatiles

    Tomato (Solanum lycopersicum L.) has become a popular model for genetic studies of fruit flavor in the last two decades. In this article we present a study of tomato fruit flavor, including an analysis of the genetic, metabolic and sensorial variation of a collection of contemporary commercial glasshouse tomato cultivars, followed by a validation of the associations found by quantitative trait locus (QTL) analysis of representative biparental segregating populations. This led to the identification of the major sensorial and chemical components determining fruit flavor variation and detection of the underlying QTLs. The high representation of QTL haplotypes in the breeders’ germplasm suggests that there is great potential for applying these QTLs in current breeding programs aimed at improving tomato flavor. A QTL on chromosome 4 was found to affect the levels of the phenylalanine-derived volatiles (PHEVs) 2-phenylethanol, phenylacetaldehyde and 1-nitro-2-phenylethane. Fruits of near-isogenic lines contrasting for this locus and in the composition of PHEVs significantly differed in the perception of fruity and rose-hip-like aroma. The PHEV locus was fine mapped, which allowed for the identification of FLORAL4 as a candidate gene for PHEV regulation. Using a gene-editing-based (CRISPR-CAS9) reverse-genetics approach, FLORAL4 was demonstrated to be the key factor in this QTL affecting PHEV accumulation in tomato fruit.

    Detection of QTLs for genotype × environment interactions in tomato seeds and seedlings
    Geshnizjani, Nafiseh ; Snoek, Basten L. ; Willems, Leo A.J. ; Rienstra, Juriaan A. ; Nijveen, Harm ; Hilhorst, Henk W.M. ; Ligterink, Wilco - \ 2020
    Plant, Cell & Environment 43 (2020)8. - ISSN 0140-7791 - p. 1973 - 1988.
    high phosphate - low nitrogen - maternal environment - QTL × E - seed quality - seedling establishment - tomato

    Seed quality and seedling establishment are the most important factors affecting successful crop development. They depend on the genetic background and are acquired during seed maturation and therefor, affected by the maternal environment under which the seeds develop. There is little knowledge about the genetic and environmental factors that affect seed quality and seedling establishment. The aim of this study is to identify the loci and possible molecular mechanisms involved in acquisition of seed quality and how these are controlled by adverse maternal conditions. For this, we used a tomato recombinant inbred line (RIL) population consisting of 100 lines which were grown under two different nutritional environmental conditions, high phosphate and low nitrate. Most of the seed germination traits such as maximum germination percentage (Gmax), germination rate (t50) and uniformity (U8416) showed ample variation between genotypes and under different germination conditions. This phenotypic variation leads to identification of quantitative trait loci (QTLs) which were dependent on genetic factors, but also on the interaction with the maternal environment (QTL × E). Further studies of these QTLs may ultimately help to predict the effect of different maternal environmental conditions on seed quality and seedling establishment which will be very useful to improve the production of high-performance seeds.

    Revisiting the Role of Master Regulators in Tomato Ripening
    Wang, Rufang ; Angenent, Gerco C. ; Seymour, Graham ; Maagd, Ruud A. de - \ 2020
    Trends in Plant Science 25 (2020)3. - ISSN 1360-1385 - p. 291 - 301.
    CRISPR- mutagenesis - gain-of-function - mutants - ripening - tomato - transcription factors

    The study of transcriptional regulation of tomato ripening has been led by spontaneous mutations in transcription factor (TF) genes that completely inhibit normal ripening, suggesting that they are ‘master regulators’. Studies using CRISPR/Cas9 mutagenesis to produce knockouts of the underlying genes indicate a different picture, suggesting that the regulation is more robust than previously thought. This requires us to revisit our model of the regulation of ripening and replace it with one involving a network of partially redundant components. At the same time, the fast rise of CRISPR/Cas mutagenesis, resulting in unexpectedly weak phenotypes, compared with knockdown technology, suggests that compensatory mechanisms may obscure protein functions. This emphasises the need for assessment of these mechanisms in plants and for the careful design of mutagenesis experiments.

    Metabolic Model of the Phytophthora infestans-Tomato Interaction Reveals Metabolic Switches during Host Colonization
    Rodenburg, Sander Y.A. ; Seidl, Michael F. ; Judelson, Howard S. ; Vu, Andrea L. ; Govers, Francine ; Ridder, Dick de - \ 2019
    mBio 10 (2019)4. - ISSN 2150-7511
    metabolic modeling - metabolism - oomycetes - Phytophthora infestans - tomato

    The oomycete pathogen Phytophthora infestans causes potato and tomato late blight, a disease that is a serious threat to agriculture. P. infestans is a hemibiotrophic pathogen, and during infection, it scavenges nutrients from living host cells for its own proliferation. To date, the nutrient flux from host to pathogen during infection has hardly been studied, and the interlinked metabolisms of the pathogen and host remain poorly understood. Here, we reconstructed an integrated metabolic model of P. infestans and tomato (Solanum lycopersicum) by integrating two previously published models for both species. We used this integrated model to simulate metabolic fluxes from host to pathogen and explored the topology of the model to study the dependencies of the metabolism of P. infestans on that of tomato. This showed, for example, that P. infestans, a thiamine auxotroph, depends on certain metabolic reactions of the tomato thiamine biosynthesis. We also exploited dual-transcriptome data of a time course of a full late blight infection cycle on tomato leaves and integrated the expression of metabolic enzymes in the model. This revealed profound changes in pathogen-host metabolism during infection. As infection progresses, P. infestans performs less de novo synthesis of metabolites and scavenges more metabolites from tomato. This integrated metabolic model for the P. infestans-tomato interaction provides a framework to integrate data and generate hypotheses about in planta nutrition of P. infestans throughout its infection cycle.IMPORTANCE Late blight disease caused by the oomycete pathogen Phytophthora infestans leads to extensive yield losses in tomato and potato cultivation worldwide. To effectively control this pathogen, a thorough understanding of the mechanisms shaping the interaction with its hosts is paramount. While considerable work has focused on exploring host defense mechanisms and identifying P. infestans proteins contributing to virulence and pathogenicity, the nutritional strategies of the pathogen are mostly unresolved. Genome-scale metabolic models (GEMs) can be used to simulate metabolic fluxes and help in unravelling the complex nature of metabolism. We integrated a GEM of tomato with a GEM of P. infestans to simulate the metabolic fluxes that occur during infection. This yields insights into the nutrients that P. infestans obtains during different phases of the infection cycle and helps in generating hypotheses about nutrition in planta.

    Development of an in vitro protocol to screen Clavibacter michiganensis subsp. michiganensis pathogenicity in different Solanum species.
    Mohd Nadzir, M.M. ; Vieira Lelis, Flavia ; Thapa, B. ; Ali, Afrida ; Visser, R.G.F. ; Heusden, A.W. van; Wolf, J.M. van der - \ 2019
    Plant Pathology 68 (2019)1. - ISSN 0032-0862 - p. 42 - 48.
    Clavibacter - Cmm - disease screening - in vitro - PathoScreen - tomato
    Clavibacter michiganensis subsp. michiganensis (Cmm) is a quarantine organism in Europe and in many other countries. It is one of the most severe bacterial pathogens affecting tomato. Screening tomato plants for their resistance level
    to Cmm requires a large amount of space under quarantine conditions and is therefore costly. This project developed a new inoculation protocol on in vitro tomato plants to facilitate a more economic and higher throughput disease screening. A new method using the PathoScreen system was tested to localize green fluorescent protein-tagged Cmm in planta and to quantify the pathogen based on the percentage of corrected GFP (cGFP%). The system was sensitive in detecting the GFP-tagged Cmm in the shoots, but in the roots a high autofluorescence masked detection and thus sensitivity of the assay. The in vitro protocol was tested on several wild relatives of tomato, which were previously screened in a greenhouse assay. The correlation between wilt symptoms in vitro and wilt symptoms in the greenhouse was overall moderate (r = 0.6462). The protocol worked well in differentiating the two parents that were used in the mapping studies. This study shows that the in vitro protocol can be efficiently used for resistance breeding in many tomato genotypes.
    DNA sequence and shape are predictive for meiotic crossovers throughout the plant kingdom
    Demirci, Sevgin ; Peters, Sander A. ; Ridder, Dick de; Dijk, Aalt D.J. van - \ 2018
    The Plant Journal 95 (2018)4. - ISSN 0960-7412 - p. 686 - 699.
    Arabidopsis thaliana - crossover - DNA shape - genome accessibility - machine learning - maize - meiotic recombination - prediction - rice - tomato

    A better understanding of genomic features influencing the location of meiotic crossovers (COs) in plant species is both of fundamental importance and of practical relevance for plant breeding. Using CO positions with sufficiently high resolution from four plant species [Arabidopsis thaliana, Solanum lycopersicum (tomato), Zea mays (maize) and Oryza sativa (rice)] we have trained machine-learning models to predict the susceptibility to CO formation. Our results show that CO occurrence within various plant genomes can be predicted by DNA sequence and shape features. Several features related to genome content and to genomic accessibility were consistently either positively or negatively related to COs in all four species. Other features were found as predictive only in specific species. Gene annotation-related features were especially predictive for maize, whereas in tomato and Arabidopsis propeller twist and helical twist (DNA shape features) and AT/TA dinucleotides were found to be the most important. In rice, high roll (another DNA shape feature) and low CA dinucleotide frequency in particular were found to be associated with CO occurrence. The accuracy of our models was sufficient for Arabidopsis and rice (area under receiver operating characteristic curve, AUROC > 0.5), and was high for tomato and maize (AUROC ≫ 0.5), demonstrating that DNA sequence and shape are predictive for meiotic COs throughout the plant kingdom.

    Quantitative Trait Loci in Solanaceae species
    Kuzniar, Arnold ; Singh, G. - \ 2018
    Wageningen University & Research
    plant breeding - plant genetics - quantitative trait locus - QTL - genetic marker - trait - Solanaceae - tomato - potato - FAIR data - RDF - SQLite - csv
    This tar archive contains experimental data on Quantitative Trait Loci (QTLs) mapped in Solanacea species. In particular, the QTL data were extracted from tomato- and potato-specific literature using the QTL TableMiner++ tool, and the resulting data were made available in machine-readable and semantically-interoperable formats: SQLite database (.db); comma-separated value file (.csv); RDF/Turle file (.ttl).
    The battle in the apoplast: further insights into the roles of proteases and their inhibitors in plant-pathogen interactions
    Karimi Jashni, M. ; Mehrabi, R. ; Collemare, J. ; Mesarich, C.H. ; Wit, P.J.G.M. de - \ 2015
    Frontiers in Plant Science 6 (2015). - ISSN 1664-462X - 7 p.
    cf-2-dependent disease resistance - extracellular serine-protease - l. enhances resistance - class iv chitinases - phytophthora-infestans - cladosporium-fulvum - proteolytic-enzymes - antifungal activity - gene-expression - tomato
    Upon host penetration, fungal pathogens secrete a plethora of effectors to promote disease, including proteases that degrade plant antimicrobial proteins, and protease inhibitors (PIs) that inhibit plant proteases with antimicrobial activity. Conversely, plants secrete proteases and PIs to protect themselves against pathogens or to mediate recognition of pathogen proteases and PIs, which leads to induction of defense responses. Many examples of proteases and PIs mediating effector-triggered immunity in host plants have been reported in the literature, but little is known about their role in compromising basal defense responses induced by microbe-associated molecular patterns. Recently, several reports appeared in literature on secreted fungal proteases that modify or degrade pathogenesis-related proteins, including plant chitinases or PIs that compromise their activities. This prompted us to review the recent advances on proteases and PIs involved in fungal virulence and plant defense. Proteases and PIs from plants and their fungal pathogens play an important role in the arms race between plants and pathogens, which has resulted in co-evolutionary diversification and adaptation shaping pathogen lifestyles.
    Host plant resistance towards the cabbage whitefly in Brassica oleracea and its wild relatives
    Pelgrom, K.T.B. ; Broekgaarden, C. ; Voorrips, R.E. ; Bas, N. ; Visser, R.G.F. ; Vosman, B.J. - \ 2015
    Euphytica 202 (2015)2. - ISSN 0014-2336 - p. 297 - 306.
    aleyrodes-proletella homoptera - glucosinolate polymorphism - insect-resistance - cultivars - populations - fruticulosa - tomato - tabaci
    The cabbage whitefly (Aleyrodes proletella) is a phloem-feeding insect that is a serious problem in Brassica oleracea crops like Brussels sprouts, kale and savoy cabbage. In order to develop whitefly-resistant varieties it is essential to identify effective sources of resistance. In this study, we screened a large collection of 432 accessions, including wild material and landraces of Brassica oleracea as well as crop wild relatives, to determine whitefly performance in a no-choice field experiment. Putatively resistant accessions were further tested under greenhouse conditions. Resistant accessions were identified among B. oleracea var. capitata (cabbage) landraces and in the species B. villosa, B. incana and B. montana. Whereas resistance in cabbage is only expressed in plants of at least 12 weeks old, some wild relatives were already starting to express resistance at 6 weeks. This could open up possibilities for breeding cabbages that are resistant at a young(er) plant age. Our research also shows again the importance of crop wild relatives for finding pest resistances.
    Introgression Browser: High throughput whole-genome SNP visualization
    Aflitos, S.A. ; Sanchez Perez, G.F. ; Ridder, D. de; Fransz, P. ; Schranz, M.E. ; Jong, J.H.S.G.M. de; Peters, S.A. - \ 2015
    The Plant Journal 82 (2015)1. - ISSN 0960-7412 - p. 174 - 182.
    in-situ hybridization - alien chromosomes - recombination - tomato - markers - thaliana - potato - identification - organization - improvement
    Breeding by introgressive hybridization is a pivotal strategy to broaden the genetic basis of crops. Usually, the desired traits are monitored in consecutive crossing generations by marker-assisted selection, but their analyses fail in chromosome regions where crossover recombinants are rare or not viable. Here, we present the Introgression Browser (IBROWSER), a bioinformatics tool aimed at visualizing introgressions at nucleotide or SNP accuracy. The software selects homozygous SNPs from Variant Call Format (VCF) information and filters out heterozygous SNPs, Multi-Nucleotide Polymorphisms (MNPs) and insertion-deletions (InDels). For data analysis IBROWSER makes use of sliding windows, but if needed it can generate any desired fragmentation pattern through General Feature Format (GFF) information. In an example of tomato (Solanum lycopersicum) accessions we visualize SNP patterns and elucidate both position and boundaries of the introgressions. We also show that our tool is capable of identifying alien DNA in a panel of the closely related S. pimpinellifolium by examining phylogenetic relationships of the introgressed segments in tomato. In a third example, we demonstrate the power of the IBROWSER in a panel of 597 Arabidopsis accessions, detecting the boundaries of a SNP-free region around a polymorphic 1.17 Mbp inverted segment on the short arm of chromosome 4. The architecture and functionality of IBROWSER makes the software appropriate for a broad set of analyses including SNP mining, genome structure analysis, and pedigree analysis. Its functionality, together with the capability to process large data sets and efficient visualization of sequence variation, makes IBROWSER a valuable breeding tool.
    Comprehensive metabolomics to evaluate the impact of industrial processing on the phytochemical composition of vegetable purees
    Lopez-Sanchez, P. ; Vos, R.C.H. de; Jonker, H.H. ; Mumm, R. ; Hall, R.D. ; Bialek, L. ; Leenman, R. ; Strassburg, K. ; Vreeken, R. ; Hankemeier, T. ; Schumm, S. ; Duynhoven, J.P.M. van - \ 2015
    Food Chemistry 168 (2015). - ISSN 0308-8146 - p. 348 - 355.
    mass-spectrometry - plant metabolomics - thermal treatments - vitamin-c - broccoli - tomato - fruit - antioxidant - cancer - l.
    The effects of conventional industrial processing steps on global phytochemical composition of broccoli, tomato and carrot purees were investigated by using a range of complementary targeted and untargeted metabolomics approaches including LC–PDA for vitamins, 1H NMR for polar metabolites, accurate mass LC–QTOF MS for semi-polar metabolites, LC–MRM for oxylipins, and headspace GC–MS for volatile compounds. An initial exploratory experiment indicated that the order of blending and thermal treatments had the highest impact on the phytochemicals in the purees. This blending-heating order effect was investigated in more depth by performing alternate blending-heating sequences in triplicate on the same batches of broccoli, tomato and carrot. For each vegetable and particularly in broccoli, a large proportion of the metabolites detected in the purees was significantly influenced by the blending-heating order, amongst which were potential health-related phytochemicals and flavour compounds like vitamins C and E, carotenoids, flavonoids, glucosinolates and oxylipins. Our metabolomics data indicates that during processing the activity of a series of endogenous plant enzymes, such as lipoxygenases, peroxidases and glycosidases, including myrosinase in broccoli, is key to the final metabolite composition and related quality of the purees.
    A bead-based suspension array for the multiplexed detection of begomoviruses and their whitefly vectors
    Brunschot, S.L. van; Bergervoet, J.H.W. ; Pagendam, D.E. ; Weerdt, M. de; Geering, A.D.W. ; Drenth, A. ; Vlugt, R.A.A. van der - \ 2014
    Journal of Virological Methods 198 (2014). - ISSN 0166-0934 - p. 86 - 94.
    leaf-curl-virus - time pcr assay - bemisia-tabaci - q biotypes - tomato - identification - geminiviruses - aleyrodidae - hemiptera - invasion
    Bead-based suspension array systems enable simultaneous fluorescence-based identification of multiple nucleic acid targets in a single reaction. This study describes the development of a novel approach to plant virus and vector diagnostics, a multiplexed 7-plex array that comprises a hierarchical set of assays for the simultaneous detection of begomoviruses and Bemisia tabaci, from both plant and whitefly samples. The multiplexed array incorporates genus, species and strain-specific assays, offering a unique approach for identifying both known and unknown viruses and B. tabaci species. When tested against a large panel of sequence-characterized begomovirus and whitefly samples, the array was shown to be 100% specific to the homologous target. Additionally, the multiplexed array was highly sensitive, efficiently and concurrently determining both virus and whitefly identity from single viruliferous whitefly samples. The detection limit for one assay within the multiplexed array that specifically detects Tomato yellow leaf curl virus-Israel (TYLCV-IL) was quantified as 200 fg of TYLCV-IL DNA, directly equivalent to that of TYLCVspecific qPCR. Highly reproducible results were obtained over multiple tests. The flexible multiplexed array described in this study has great potential for use in plant quarantine, biosecurity and disease management programs worldwide. (C) 2014 Elsevier B.V. All rights reserved.
    Mapping in the era of sequencing: high density genotyping and its application for mapping TYLCV resistance in Solanum pimpinellifolium
    Viquez-Zamora, M. ; Caro Rios, C.M. ; Finkers, H.J. ; Tikunov, Y.M. ; Bovy, A.G. ; Visser, R.G.F. ; Bai, Y. ; Heusden, A.W. van - \ 2014
    BMC Genomics 15 (2014). - ISSN 1471-2164 - 10 p.
    leaf-curl-virus - recombinant inbred lines - mass-spectrometry - lycopersicon-pimpinellifolium - tomato - infection - genes - metabolomics - inheritance - population
    Background A RIL population between Solanum lycopersicum cv. Moneymaker and S. pimpinellifolium G1.1554 was genotyped with a custom made SNP array. Additionally, a subset of the lines was genotyped by sequencing (GBS). Results A total of 1974 polymorphic SNPs were selected to develop a linkage map of 715 unique genetic loci. We generated plots for visualizing the recombination patterns of the population relating physical and genetic positions along the genome. This linkage map was used to identify two QTLs for TYLCV resistance which contained favourable alleles derived from S. pimpinellifolium. Further GBS was used to saturate regions of interest, and the mapping resolution of the two QTLs was improved. The analysis showed highest significance on Chromosome 11 close to the region of 51.3 Mb (qTy-p11) and another on Chromosome 3 near 46.5 Mb (qTy-p3). Furthermore, we explored the population using untargeted metabolic profiling, and the most significant differences between susceptible and resistant plants were mainly associated with sucrose and flavonoid glycosides. Conclusions The SNP information obtained from an array allowed a first QTL screening of our RIL population. With additional SNP data of a RILs subset, obtained through GBS, we were able to perform an in silico mapping improvement to further confirm regions associated with our trait of interest. With the combination of different¿~¿omics platforms we provide valuable insight into the genetics of S. pimpinellifolium-derived TYLCV resistance.
    Response of the zoophytophagous predators Macrolophus pygmaeus and Nesidiocoris tenuis to volatiles of uninfested plants and to plants infested by prey or conspecifics
    Lins, J.C. ; Loon, J.J.A. van; Bueno, V.H.P. ; Lucas-Barbosa, D. ; Dicke, M. ; Lenteren, J.C. van - \ 2014
    BioControl 59 (2014)6. - ISSN 1386-6141 - p. 707 - 718.
    borer tuta-absoluta - carnivorous arthropods - heteroptera miridae - biological-control - infochemical use - spider-mites - tomato - herbivores - bug - caliginosus
    Knowledge about the orientation mechanisms used by two important predaceous mirids (Macrolophus pygmaeus Rambour and Nesidiocoris tenuis (Reuter)) in finding their prey (whitefly Bemisia tabaci (Gennadius) and the tomato borer Tuta absoluta (Meyrick)) is limited. In a Y-tube olfactometer, we tested the behavioral responses of naïve and experienced predators to uninfested plants, herbivore-induced plant volatiles (HIPVs) from plants infested with T. absoluta and/or B. tabaci, the sex pheromone of T. absoluta, and volatiles produced by plants injured by the predators. Nesidiocoris tenuis responds to volatiles produced by uninfested plants only after experience with the plant, whereas naïve and experienced M. pygmaeus show positive chemotaxis. Both predators are attracted to volatiles from prey-infested plants, and we provide the first evidence that experience affects this response in M. pygmaeus. Infestation of the same plant by both prey species elicited similar responses by the two predators as plants infested by either herbivore singly. Neither predator responded to sex pheromones of T. absoluta. Macrolophus pygmaeus avoided plants injured by conspecifics, while N. tenuis females were attracted by such plants. The implications of these results for augmentative biological control are discussed.
    Responses of two Anthurium cultivars to high daily integrals of diffuse light
    Li, T. ; Heuvelink, E. ; Noort, F. van; Kromdijk, J. ; Marcelis, L.F.M. - \ 2014
    Scientia Horticulturae 179 (2014). - ISSN 0304-4238 - p. 306 - 313.
    radiation-use efficiency - structural plant-model - yield components - growth analysis - photosynthesis - tomato - interception - architecture - quality - biology
    Heavy shading is commonly applied during production of pot-plants in order to avoid damage caused by high light intensities; usually the daily light integral (DLI) is limited to 5–8 mol m-2 d-1 photosynthetically active radiation (PAR). However, shading carries a production penalty as light is the driving force for photosynthesis. Diffuse glass has been developed to scatter the incident light in greenhouses. This study aims at investigating the effect of diffuse glass cover and high DLI under diffuse glass cover on the growth of pot-plants; furthermore, to systematically identify and quantify the yield components which are influenced by these treatments. Experiments were carried out with two Anthurium andreanum cultivars (Royal Champion and Pink Champion) in a conventional modern glasshouse compartment covered by clear glass with DLI limited to 7.5 mol m-2 d-1 (average realized DLI was 7.2 mol m-2 d-1), and another two glasshouse compartments covered by diffuse glass with DLI limited to 7.5 (average realized DLI was 7.5 mol m-2 d-1) and 10 mol m-2 d-1 (average realized DLI was 8.9 mol m-2 d-1). Diffuse glass cover resulted in less variation of temporal photosynthetic photon flux density (PPFD) distribution compared with the clear glass cover. Under similar DLI conditions (DLI limited to 7.5 mol m-2 d-1), diffuse glass cover stimulated dry mass production per unit intercepted PPFD (RUE) in ‘Royal Champion’ by 8%; whilst this stimulating effect did not occur in ‘Pink Champion’. Under diffuse glass cover, biomass production was proportional to DLI in both cultivars (within the range 7.5–9 mol m-2 d-1). Consequently higher DLI led to more flowers, leaves and stems. Furthermore, high DLI resulted in more compact plants without light damage in leaves or flowers in both cultivars. ‘Pink Champion’ produced more biomass than ‘Royal Champion’ in all treatments because of higher RUE which resulted from a more advantageous canopy architecture for light capture and more advantageous leaf photosynthetic properties. We conclude that less shading under diffuse glass cover not only stimulates plant growth but also improves plant ornamental quality (i.e. compactness).
    Filamentous pathogen effector functions: of pathogens, hosts and microbiomes
    Rövenich, H. ; Boshoven, J.C. ; Thomma, B. - \ 2014
    Current Opinion in Plant Biology 20 (2014). - ISSN 1369-5266 - p. 96 - 103.
    chitin-triggered immunity - secreted fungal effector - potato famine pathogen - cladosporium-fulvum - protease inhibitor - magnaporthe-oryzae - plant-pathogens - genome evolution - tomato - virulence
    Microorganisms play essential roles in almost every environment on earth. For instance, microbes decompose organic material, or establish symbiotic relationships that range from pathogenic to mutualistic. Symbiotic relationships have been particularly well studied for microbial plant pathogens and have emphasized the role of effectors; secreted molecules that support host colonization. Most effectors characterized thus far play roles in deregulation of host immunity. Arguably, however, pathogens not only deal with immune responses during host colonization, but also encounter other microbes including competitors, (myco)parasites and even potential co-operators. Thus, part of the effector catalog may target microbiome co-inhabitants rather than host physiology.
    Functional analysis of the conserved transcriptional regulator CfWor1 in Cladosporium fulvum reveals diverse roles in the virulence of plant pathogenic fungi
    Ökmen, B. ; Collemare, J. ; Griffiths, S.A. ; Burgt, A. van der; Cox, R. ; Wit, P.J.G.M. de - \ 2014
    Molecular Microbiology 92 (2014)1. - ISSN 0950-382X - p. 10 - 27.
    avirulence gene avr9 - dna-binding domains - candida-albicans - alternaria-brassicicola - magnaporthe-grisea - master regulator - expression - tomato - family - penetration
    Fungal Wor1-like proteins are conserved transcriptional regulators that are reported to regulate the virulence of several plant pathogenic fungi by affecting the expression of virulence genes. Here, we report the functional analysis of CfWor1, the homologue of Wor1 in Cladosporium fulvum. ¿cfwor1 mutants produce sclerotium-like structures and rough hyphae, which are covered with a black extracellular matrix. These mutants do not sporulate and are no longer virulent on tomato. A CE.CfWor1 transformant that constitutively expresses CfWor1 produces fewer spores with altered morphology and is also reduced in virulence. RNA-seq and RT-qrtPCR analyses suggest that reduced virulence of ¿cfwor1 mutants is due to global downregulation of transcription, translation and mitochondrial respiratory chain. The reduced virulence of the CE.CfWor1 transformant is likely due to downregulation of effector genes. Complementation of a non-virulent ¿fosge1 (Wor1-homologue) mutant of Fusarium oxysporum f. sp. lycopersici with CfWor1 restored expression of the SIX effector genes in this fungus, but not its virulence. Chimeric proteins of CfWor1/FoSge1 also only partially restored defects of the ¿fosge1 mutant, suggesting that these transcriptional regulators have functionally diverged. Altogether, our results suggest that CfWor1 primarily regulates development of C.¿fulvum, which indirectly affects the expression of a subset of virulence genes.
    Increased difficulties to control late blight in Tunisia are caused by a genetically diverse Phytophthora infestans population next to the clonal lineage NA-01
    Harbaoui, K. ; Hamada, W. ; Li, Y. ; Vleeshouwers, V.G.A.A. ; Lee, T.A.J. van der - \ 2014
    Plant Disease 98 (2014)7. - ISSN 0191-2917 - p. 898 - 908.
    genotypic diversity - durable resistance - potato - tomato - plant - netherlands - virulence
    In Tunisia, late blight caused by Phytophthora infestans is a serious threat to potato and tomato. The Mediterranean weather conditions can be conducive to infection in all seasons and the host crops, tomato and potato, are grown year round. Potato is planted and harvested in two to four overlapping intervals from August to June and tomato is grown both in open fields and in greenhouses. The consequences of these agricultural practices and the massive import of seed potato on the genetic variation of P. infestans are largely unknown. We conducted a survey in which 165 P. infestans isolates, collected from five subregions in Tunisia between 2006 and 2008, on which we studied genotypic diversity through nuclear (simple-sequence repeat [SSR]) markers and combined this with a previous study on their mitochondrial haplotypes (mtDNA). The phylogenetic analysis revealed the presence of a major clonal lineage (NA-01, A1 mating type, mitochondrial haplotype Ia). Isolates belonging to this clonal lineage were found in all regions and showed a relatively simple virulence pattern on a potato differential set carrying different Solanum demissum resistance genes. Apart from isolates belonging to this NA-01 clonal lineage, a group of isolates was found that showed a high genetic diversity, comprising both mating types and a more complex race structure that was found in the regions where late blight on potato was more difficult to control. The population on potato and tomato seems to be under different selection pressures. Isolates collected from tomato showed a low genetic diversity even though potato isolates collected simultaneously from the same location showed a high genetic diversity. Based on the SSR profile comparison, we could demonstrate that the four major clonal lineages found in the Netherlands and also in other European countries could not be found in Tunisia. Despite the massive import of potato seed from Europe, the P. infestans population in Tunisia was found to be clearly distinct
    OsJAR1 is required for JA-regulated floret opening and anther dehiscence in rice
    Xiao, Y. ; Charnikhova, T. ; Mulder, P.P.J. ; Heijmans, J. ; Hoogenboom, A. ; Agalou, A. ; Michel, C. ; Morel, J.B. ; Dreni, L. ; Kater, M.M. ; Bouwmeester, H.J. ; Wang, B. ; Zhu, Z. ; Ouwerkerk, P.B.F. - \ 2014
    Plant Molecular Biology 86 (2014)1-2. - ISSN 0167-4412 - p. 19 - 33.
    jasmonic acid biosynthesis - male-sterile mutant - l-isoleucine - methyl jasmonate - gene encodes - arabidopsis - enzyme - proteins - tomato - (+)-7-iso-jasmonoyl-l-isoleucine
    Jasmonates are important phytohormones regulating reproductive development. We used two recessive rice Tos17 alleles of OsJAR1, osjar1-2 and osjar1-3, to study the biological function of jasmonates in rice anthesis. The florets of both osjar1 alleles stayed open during anthesis because the lodicules, which control flower opening in rice, were not withering on time. Furthermore, dehiscence of the anthers filled with viable pollen, was impaired, resulting in lower fertility. In situ hybridization and promoter GUS transgenic analysis confirmed OsJAR1 expression in these floral tissues. Flower opening induced by exogenous applied methyl jasmonate was impaired in osjar1 plants and was restored in a complementation experiment with transgenics expressing a wild type copy of OsJAR1 controlled by a rice actin promoter. Biochemical analysis showed that OsJAR1 encoded an enzyme conjugating jasmonic acid (JA) to at least Ile, Leu, Met, Phe, Trp and Val and both osjar1 alleles had substantial reduction in content of JA-Ile, JA-Leu and JA-Val in florets. We conclude that OsJAR1 is a JA-amino acid synthetase that is required for optimal flower opening and closing and anther dehiscence in rice
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