Staff Publications

Staff Publications

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

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

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Ecological interactions shape the adaptive value of plant defence : Herbivore attack versus competition for light
Vries, Jorad de; Evers, Jochem B. ; Dicke, Marcel ; Poelman, Erik H. - \ 2019
Functional Ecology 33 (2019)1. - ISSN 0269-8463 - p. 129 - 138.
Brassica nigra - competition - ecological costs - functional-structural plant modelling - growth-defence trade-off - herbivore interactions - herbivory - plant - plant defence

Plants defend themselves against diverse communities of herbivorous insects. This requires an investment of limited resources, for which plants also compete with neighbours. The consequences of an investment in defence are determined by the metabolic costs of defence as well as indirect or ecological costs through interactions with other organisms. These ecological costs have a potentially strong impact on the evolution of defensive traits, but have proven to be difficult to quantify. We aimed to quantify the relative impact of the direct and indirect or ecological costs and benefits of an investment in plant defence in relation to herbivory and intergenotypic competition for light. Additionally, we evaluated how the benefits of plant defence balance its costs in the context of herbivory and intergenotypic competition. To this end, we utilised a functional-structural plant (FSP) model of Brassica nigra that simulates plant growth and development, morphogenesis, herbivory and plant defence. In the model, a simulated investment in defences affected plant growth by competing with other plant organs for resources and affected the level and distribution of herbivore damage. Our results show that the ecological costs of intergenotypic competition for light are highly detrimental to the fitness of defended plants, as it amplifies the size difference between defended and undefended plants. This leads to herbivore damage counteracting the effects of intergenotypic competition under the assumption that herbivore damage scales with plant size. Additionally, we show that plant defence relies on reducing herbivore damage rather than the dispersion of herbivore damage, which is only beneficial under high levels of herbivore damage. We conclude that the adaptive value of plant defence is highly dependent on ecological interactions and is predominantly determined by the outcome of competition for light.

Evolution of plant growth and defense in a continental introduction
Agrawal, A.A. ; Hastings, A.P. ; Bradburd, G.S. ; Woods, E.C. ; Züst, T. ; Harvey, J.A. ; Bukovinszki, T. - \ 2015
adaptation - coevolution - ecology - chemical - trade offs - butterflies - plant
Substantial research has addressed adaptation of nonnative biota to novel environments, yet surprisingly little work has integrated population genetic structure and the mechanisms underlying phenotypic differentiation in ecologically important traits. We report on studies of the common milkweed Asclepias syriaca, which was introduced from North America to Europe over the past 400 years and which lacks most of its specialized herbivores in the introduced range. Using 10 populations from each continent grown in a common environment, we identified several growth and defense traits that have diverged, despite low neutral genetic differentiation between continents. We next developed a Bayesian modeling approach to account for relationships between molecular and phenotypic differences, confirming that continental trait differentiation was greater than expected from neutral genetic differentiation. We found evidence that growth-related traits adaptively diverged within and between continents. Inducible defenses triggered by monarch butterfly herbivory were substantially reduced in European populations, and this reduction in inducibility was concordant with altered phytohormonal dynamics, reduced plant growth, and a trade-off with constitutive investment. Freedom from the community of native and specialized herbivores may have favored constitutive over induced defense. Our replicated analysis of plant growth and defense, including phenotypically plastic traits, suggests adaptive evolution following a continental introduction.
Epigenetic Basis of Morphological Variation and Phenotypic Plasticity in Arabidopsis thaliana
Kooke, R. ; Johannes, F. ; Wardenaar, R. ; Becker, F.F.M. ; Etcheverry, M. ; Colot, V. ; Vreugdenhil, D. ; Keurentjes, J.J.B. - \ 2015
The Plant Cell 27 (2015)2. - ISSN 1040-4651 - p. 337 - 348.
quantitative trait loci - dna methylation - transcription factor - qtl analysis - population - plant - inheritance - stability - evolution - performance
Epigenetics is receiving growing attention in the plant science community. Epigenetic modifications are thought to play a particularly important role in fluctuating environments. It is hypothesized that epigenetics contributes to plant phenotypic plasticity because epigenetic modifications, in contrast to DNA sequence variation, are more likely to be reversible. The population of decrease in DNA methylation 1-2 (ddm1-2)-derived epigenetic recombinant inbred lines (epiRILs) in Arabidopsis thaliana is well suited for studying this hypothesis, as DNA methylation differences are maximized and DNA sequence variation is minimized. Here, we report on the extensive heritable epigenetic variation in plant growth and morphology in neutral and saline conditions detected among the epiRILs. Plant performance, in terms of branching and leaf area, was both reduced and enhanced by different quantitative trait loci (QTLs) in the ddm1-2 inherited epigenotypes. The variation in plasticity associated significantly with certain genomic regions in which the ddm1-2 inherited epigenotypes caused an increased sensitivity to environmental changes, probably due to impaired genetic regulation in the epiRILs. Many of the QTLs for morphology and plasticity overlapped, suggesting major pleiotropic effects. These findings indicate that epigenetics contributes substantially to variation in plant growth, morphology, and plasticity, especially under stress conditions
Testing for disconnection and distance effects on physiological self-recognition within clonal fragments of Potentilla reptans
Chen, B. ; Vermeulen, P.J. ; During, H.J. ; Anten, N.P.R. - \ 2015
Frontiers in Plant Science 6 (2015). - ISSN 1664-462X - 9 p.
herb glechoma-hederacea - fragaria-chiloensis - nutrient availability - kin recognition - rooting volume - pot size - plant - integration - ramets - discrimination
Evidence suggests that belowground self-recognition in clonal plants can be disrupted between sister ramets by the loss of connections or long distances within a genet. However, these results may be confounded by severing connections between ramets in the setups. Using Potentilla reptans, we examined severance effects in a setup that grew ramet pairs with connections either intact or severed. We showed that severance generally reduced new stolon mass but had no effect on root allocation of ramets. However, it did reduce root mass of younger ramets of the pairs. We also explored evidence for physiological self-recognition with another setup that avoided severing connections by manipulating root interactions between closely connected ramets, between remotely connected ramets and between disconnected ramets within one genet. We found that ramets grown with disconnected neighbors had less new stolon mass, similar root mass but higher root allocation as compared to ramets grown with connected neighbors. There was no difference in ramet growth between closely connected- and remotely connected-neighbor treatments. We suggest that severing connections affects ramet interactions by disrupting their physiological integration. Using the second setup, we provide unbiased evidence for physiological self-recognition, while also suggesting that it can persist over long distances.
Using RNA-Seq to assemble a rose transcriptome with more than 13,000 full-length expressed genes and to develop the WagRhSNP 68k Axiom SNP array for rose (Rosa L.)
Koning, C.F.S. ; Esselink, G. ; Vukosavljev, M. ; Westende, W.P.C. van 't; Gitonga, V.W. ; Krens, F.A. ; Voorrips, R.E. ; Weg, W.E. van de; Schulz, D. ; Debener, T. ; Maliepaard, C.A. ; Arens, P.F.P. ; Smulders, M.J.M. - \ 2015
Frontiers in Plant Science 6 (2015). - ISSN 1664-462X - 10 p.
powdery mildew - markers - tool - identification - resistance - genome - diversity - sequences - platform - plant
In order to develop a versatile and large SNP array for rose, we set out to mine ESTs from diverse sets of rose germplasm. For this RNA-Seq libraries containing about 700 million reads were generated from tetraploid cut and garden roses using Illumina paired-end sequencing, and from diploid Rosa multiflora using 454 sequencing. Separate de novo assemblies were performed in order to identify single nucleotide polymorphisms (SNPs) within and between rose varieties. SNPs among tetraploid roses were selected for constructing a genotyping array that can be employed for genetic mapping and marker-trait association discovery in breeding programs based on tetraploid germplasm, both from cut roses and from garden roses. In total 68,893 SNPs were included on the WagRhSNP Axiom array. Next, an orthology-guided assembly was performed for the construction of a non-redundant rose transcriptome database. A total of 21,740 transcripts had significant hits with orthologous genes in the strawberry (Fragaria vesca L.) genome. Of these 13,390 appeared to contain the full-length coding regions. This newly established transcriptome resource adds considerably to the currently available sequence resources for the Rosaceae family in general and the genus Rosa in particular.
Combining a weed traits database with a population dynamics model predicts shifts in weed communities
Storkey, J. ; Holst, N. ; Bøjer, Q. ; Bigongiali, F. ; Bocci, G. ; Colbach, N. ; Dorner, Z. ; Riemens, M.M. ; Sartorato, I. ; Sønderskov, M. ; Verschwele, A. - \ 2015
Weed Research 55 (2015)2. - ISSN 0043-1737 - p. 206 - 218.
agricultural intensification - invertebrate abundance - functional diversity - assembly theory - climate-change - winter-wheat - plant - flora - management - competition
A functional approach to predicting shifts in weed floras in response to management or environmental change requires the combination of data on weed traits with analytical frameworks that capture the filtering effect of selection pressures on traits. A weed traits database (WTDB) was designed, populated and analysed, initially using data for 19 common European weeds, to begin to consolidate trait data in a single repository. The initial choice of traits was driven by the requirements of empirical models of weed population dynamics to identify correlations between traits and model parameters. These relationships were used to build a generic model, operating at the level of functional traits, to simulate the impact of increasing herbicide and fertiliser use on virtual weeds along gradients of seed weight and maximum height. The model generated ‘fitness contours’ (defined as population growth rates) within this trait space in different scenarios, onto which two sets of weed species, defined as common or declining in the UK, were mapped. The effect of increasing inputs on the weed flora was successfully simulated; 77% of common species were predicted to have stable or increasing populations under high fertiliser and herbicide use, in contrast with only 29% of the species that have declined. Future development of the WTDB will aim to increase the number of species covered, incorporate a wider range of traits and analyse intraspecific variability under contrasting management and environments.
How to assess species richness along single environmental gradients? Implications of potential versus realized species distributions
Goethem, T.M.W.J. van; Huijbregts, M.A.J. ; Wamelink, G.W.W. ; Schipper, A.M. - \ 2015
Environmental Pollution 200 (2015). - ISSN 0269-7491 - p. 120 - 125.
sensitivity distributions - field data - plant - diversity - abundance - macroinvertebrates - acidification - consequences - biodiversity - assemblages
Quantifying relationships between species richness and single environmental factors is challenging as species richness typically depends on multiple environmental factors. Recently, various methods have been proposed to tackle this challenge. Using a dataset comprising field observations of grassland vegetation and measured pH values, we compared three methods for deriving species richness response curves. One of the methods estimates species richness close to the maximum species richness observed at the sites, whereas the other two provide estimates of the potential species richness along the environmental gradient. Our response curves suggest that potential species richness of grasslands is slightly more sensitive to acidification than realized plant species richness. However, differences in corresponding environmental quality standards (EQS) for acidification were small compared to intrinsic spatial differences in natural soil pH, indicating that natural background values are more important to consider in the derivation of EQS for pH than methodological differences between the three approaches.
The molar H: Corg ratio of biochar is a key factor in mitigating N2O emissions from soil
Cayuela, M.L. ; Jeffery, S.L. ; Zwieten, L. van - \ 2015
Agriculture, Ecosystems and Environment 202 (2015). - ISSN 0167-8809 - p. 135 - 138.
greenhouse-gas emissions - rice - impact - straw - co2 - carbon - china - paddy - plant - denitrification
A previously published meta-analysis of biochar impacts on soil N2O emissions by Cayuela et al. (2014) found a “grand mean” reduction in N2O emissions of 54 ± 6% following biochar application to soil. Here we update this analysis to include 26 additional manuscripts bringing the total to 56 articles. The updated meta-analysis confirms that biochar reduces soil N2O emissions by 49 ± 5% (mean ± 95% confidence interval). Importantly, this meta-analysis has sufficient data to investigate the impact of biochar under field conditions, showing a statistically significant lower average reduction in the field (28 ± 16%) compared to controlled laboratory studies (54 ± 3%). A key finding is the importance of the molar H:Corg ratio of biochar in determining mitigation of N2O. Biochars with a molar H:Corg ratio 0.5 were less effective at 40 ± 16%. Together with previously published information, our new results suggest that a key mitigation mechanism is linked to the degree of polymerization and aromaticity of biochar.
How a long-lived fungus keeps mutations in check
Aanen, D.K. - \ 2014
Science 346 (2014)6212. - ISSN 0036-8075 - p. 922 - 923.
stem-cells - cancer - plant
An individual of the mushroom-forming fungus Armillaria bulbosa is among the largest and oldest of all living organisms: More than 1500 years old, it covers more than 15 ha and weighs more than 10,000 kg (1). Some trees can also reach ages of thousands of years (2). How can such long-lived organisms keep the number of deleterious mutations during somatic growth in check? In a recent paper in Mycologia, Anderson and Catona (3) report extremely low genetic variation, and by inference a very low mutation rate, in a long-lived individual of another fungus, Armillaria gallica (see the photo). This genomic stability is puzzling and unexpected, because the sequenced samples come from locations that are more than 100 m apart and presumably separated by many rounds of cell division
Genetic resources for quantitative trait analysis: novelty and efficiency in design from an Arabidopsis perspective
Wijnen, C.L. ; Keurentjes, J.J.B. - \ 2014
Current Opinion in Plant Biology 18 (2014). - ISSN 1369-5266 - p. 103 - 109.
genome-wide association - inbred line population - functional genomics - thaliana accession - induced mutations - natural variation - identification - plant - mutagenesis - phenotypes
The use of genetic resources for the analysis of quantitative traits finds its roots in crop breeding but has seen a rejuvenation in Arabidopsis thaliana thanks to specific tools and genomic approaches. Although widely used in numerous crop and natural species, many approaches were first developed in this reference plant. We will discuss the scientific background and historical use of mapping populations in Arabidopsis and highlight the technological innovations that drove the development of novel strategies. We will especially lay emphasis on the methodologies used to generate the diverse population types and designate possible applications. Finally we highlight some of the most recent developments in generating genetic mapping resources and suggest specific usage for these novel tools and concepts.
Effects of Dichrostachys cinerea (L.) Wight & Arn (Fabaceae) on herbaceous species in a semi-arid rangeland in Zimbabwe
Mudzengi, C. ; Kativu, S. ; Dahwa, E. ; Poshiwa, X. ; Murungweni, C. - \ 2014
Nature Conservation 7 (2014). - ISSN 1314-6947 - p. 51 - 60.
plant - invasibility - vegetation - invasions - ecosystem - botswana
Anthropogenic alteration of an environment and other disturbance regimes may enable the expansion of some native species into new geographical areas, a phenomenon observed with Dichrostachys cinerea. Five D. cinerea invaded sites, each approximately one hectare in size were assessed for the effects of D. cinerea on native herbaceous species diversity, richness, basal cover, litter cover, top hamper and plant vigour. The same attributes were studied in five uninvaded sites adjacent to, and equal in size to each invaded site. Forty herbaceous species were identified in the area. There were significant differences (P <0.05) noted in species richness, basal cover, litter cover, top hamper, plant vigour, and species diversities between invaded and uninvaded sites, with uninvaded sites recording higher values than invaded sites. Altitude, erosion and the edaphic variables pH, N, P and K, which were included as explanatory variables, also differed significantly (P
Genomic prediction based on data from three layer lines using non-linear regression models
Huang, H. ; Windig, J.J. ; Vereijken, A. ; Calus, M.P.L. - \ 2014
Genetics, Selection, Evolution 46 (2014). - ISSN 0999-193X - 11 p.
dairy-cattle breeds - dimensionality reduction - gaussian kernel - accuracy - traits - values - validation - selection - pedigree - plant
Background - Most studies on genomic prediction with reference populations that include multiple lines or breeds have used linear models. Data heterogeneity due to using multiple populations may conflict with model assumptions used in linear regression methods. Methods - In an attempt to alleviate potential discrepancies between assumptions of linear models and multi-population data, two types of alternative models were used: (1) a multi-trait genomic best linear unbiased prediction (GBLUP) model that modelled trait by line combinations as separate but correlated traits and (2) non-linear models based on kernel learning. These models were compared to conventional linear models for genomic prediction for two lines of brown layer hens (B1 and B2) and one line of white hens (W1). The three lines each had 1004 to 1023 training and 238 to 240 validation animals. Prediction accuracy was evaluated by estimating the correlation between observed phenotypes and predicted breeding values. Results - When the training dataset included only data from the evaluated line, non-linear models yielded at best a similar accuracy as linear models. In some cases, when adding a distantly related line, the linear models showed a slight decrease in performance, while non-linear models generally showed no change in accuracy. When only information from a closely related line was used for training, linear models and non-linear radial basis function (RBF) kernel models performed similarly. The multi-trait GBLUP model took advantage of the estimated genetic correlations between the lines. Combining linear and non-linear models improved the accuracy of multi-line genomic prediction. Conclusions - Linear models and non-linear RBF models performed very similarly for genomic prediction, despite the expectation that non-linear models could deal better with the heterogeneous multi-population data. This heterogeneity of the data can be overcome by modelling trait by line combinations as separate but correlated traits, which avoids the occasional occurrence of large negative accuracies when the evaluated line was not included in the training dataset. Furthermore, when using a multi-line training dataset, non-linear models provided information on the genotype data that was complementary to the linear models, which indicates that the underlying data distributions of the three studied lines were indeed heterogeneous.
Identification of reference genes for gene expression studies during seed germination and seedling establishment Ricinus communis L.
Ribeiro de Jesus, P.R. ; Dekkers, S.J.W. ; Fernandez, L.G. ; Castro, R.D. De; Ligterink, W. ; Hilhorst, H.W.M. - \ 2014
Seed Science Research 24 (2014)4. - ISSN 0960-2585 - p. 341 - 352.
time rt-pcr - fatty-acid - jatropha-curcas - castor-oil - phosphoenolpyruvate carboxylase - arabidopsis - normalization - plant - cloning - family
Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) is an important technology to analyse gene expression levels during plant development or in response to different treatments. An important requirement to measure gene expression levels accurately is a properly validated set of reference genes. In this context, we analysed the potential use of 17 candidate reference genes across a diverse set of samples, including several tissues, different stages and environmental conditions, encompassing seed germination and seedling growth in Ricinus communis L. These genes were tested by RT-qPCR and ranked according to the stability of their expression using two different approaches: GeNorm and NormFinder. GeNorm and Normfinder indicated that ACT, POB and PP2AA1 comprise the optimal combination for normalization of gene expression data in inter-tissue (heterogeneous sample panel) studies. We also describe the optimal combination of reference genes for a subset of root, endosperm and cotyledon samples. In general, the most stable genes suggested by GeNorm are very consistent with those indicated by NormFinder, which highlights the strength of the selection of reference genes in our study. We also validated the selected reference genes by normalizing the expression levels of three target genes involved in energy metabolism with the reference genes suggested by GeNorm and NormFinder. The approach used in this study to identify stably expressed genes, and thus potential reference genes, was applied successfully for R. communis and it provides important guidelines for RT-qPCR studies in seeds and seedlings for other species (especially in those cases where extensive microarray data are not available)
Introduced tree species released from negative soil biota
Putten, W.H. van der - \ 2014
New Phytologist 202 (2014)2. - ISSN 0028-646X - p. 341 - 343.
plant - feedbacks - ecology
Over-expression of Arabidopsis AtCHR23 chromatin remodeling ATPase results in increased variability of growth and gene expression
Folta, A. ; Severing, E.I. ; Krauskopf, J. ; Geest, H.C. van de; Verver, J. ; Nap, J.P.H. ; Mlynarova, L. - \ 2014
BMC Plant Biology 14 (2014). - ISSN 1471-2229 - 18 p.
rna-seq - seed-germination - stress responses - root-growth - thaliana - plant - pickle - noise - identification - consequences
Background Plants are sessile organisms that deal with their -sometimes adverse- environment in well-regulated ways. Chromatin remodeling involving SWI/SNF2-type ATPases is thought to be an important epigenetic mechanism for the regulation of gene expression in different developmental programs and for integrating these programs with the response to environmental signals. In this study, we report on the role of chromatin remodeling in Arabidopsis with respect to the variability of growth and gene expression in relationship to environmental conditions. Results Already modest (2-fold) over-expression of the AtCHR23 ATPase gene in Arabidopsis results in overall reduced growth compared to the wild-type. Detailed analyses show that in the root, the reduction of growth is due to reduced cell elongation. The reduced-growth phenotype requires sufficient light and is magnified by applying deliberate abiotic (salt, osmotic) stress. In contrast, the knockout mutation of AtCHR23 does not lead to such visible phenotypic effects. In addition, we show that over-expression of AtCHR23 increases the variability of growth in populations of genetically identical plants. These data indicate that accurate and controlled expression of AtCHR23 contributes to the stability or robustness of growth. Detailed RNAseq analyses demonstrate that upon AtCHR23 over-expression also the variation of gene expression is increased in a subset of genes that associate with environmental stress. The larger variation of gene expression is confirmed in individual plants with the help of independent qRT-PCR analysis. Conclusions Over-expression of AtCHR23 gives Arabidopsis a phenotype that is markedly different from the growth arrest phenotype observed upon over-expression of AtCHR12, the paralog of AtCHR23, in response to abiotic stress. This demonstrates functional sub-specialization of highly similar ATPases in Arabidopsis. Over-expression of AtCHR23 increases the variability of growth among genetically identical individuals in a way that is consistent with increased variability of expression of a distinct subset of genes that associate with environmental stress. We propose that ATCHR23-mediated chromatin remodeling is a potential component of a buffer system in plants that protects against environmentally-induced phenotypic and transcriptional variation.
Holocene vegetation and fire dynamics in central-eastern Brazil: Molecular records from the Pau de Fruta peatland
Schellekens, J. ; Horak-Terra, I. ; Buurman, P. ; Silva, A.C. ; Vidal-Torrado, P. - \ 2014
Organic Geochemistry 77 (2014). - ISSN 0146-6380 - p. 32 - 42.
soil organic-matter - chromatography-mass-spectrometry - pyrolysis-gc-ms - humic substances - minas-gerais - isotopic composition - ombrotrophic peat - lignin - serra - plant
Tropical climate dynamics play a major role in the global climate system. Precipitation patterns in the Serra do Espinhaço Meridional (Minas Gerais, Brazil) are influenced by both the South Atlantic Convergence Zone (SACZ) and the Inter Tropical Convergence Zone (ITCZ). This makes the area important for the interpretation of climate dynamics. The composition of the Holocene Pau de Fruta peat deposit was analysed using pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS). Molecular records agreed well with d13C and d15N stable isotopes, C content and mineral content, and pollen records. Changes in peatland plant species composition and fire occurrence indicated several wet and dry periods for the Pau de Fruta peatland during the Holocene; from the beginning of the Holocene to 7400 cal yr BP (phase I; dry and cold), from 7400 to 4200 cal yr BP (phase II; wet and warm), from 4200 to 1000 cal yr BP (phase III; dry and warm), from 1000 to 400 cal yrBP (phase IV; wet and warm) and from 400 cal yr BP to the present (V). The hydrological shifts showed a chronology comparable with that described in other palaeoclimatic studies for central-eastern Brazil, indicating that local conditions agree with regional ones. Analytical Py of the peat deposit provided a multi-proxy record via the identification of specific markers for both peatland plants (vegetation) and charred material (fire), whereas the general chemistry provided information on the degree of decomposition of the organic matter. Molecular chemistry of the peat core sampled at high resolution provided insight into peatland C dynamics, which is important for the interpretation of C sequestration in tropical peatlands. Molecular aspects accurately reflected local environmental change. The general agreement of Py data with pollen and inorganic chemistry supports the use of the molecular approach, because it provides local proxy indicators for peatlands, avoiding a mixture of local and regional signals.
A novel Botrytis species is associated with a newly emergent foliar disease in cultivated Hemerocallis
Grant-Downton, R.T. ; Terhem, R.B. ; Kapralov, M. ; Mehdi, S. ; Rodriguez-Enriquez, M.J. ; Gurr, S.J. ; Kan, J.A.L. van; Dewey, F.M. - \ 2014
PLoS ONE 9 (2014)6. - ISSN 1932-6203 - 11 p.
genetic-variation - south-carolina - plant - cinerea - host - infection - elliptica - fungi - armillaria - diversity
Foliar tissue samples of cultivated daylilies (Hemerocallis hybrids) showing the symptoms of a newly emergent foliar disease known as ‘spring sickness’ were investigated for associated fungi. The cause(s) of this disease remain obscure. We isolated repeatedly a fungal species which proved to be member of the genus Botrytis, based on immunological tests. DNA sequence analysis of these isolates, using several different phyogenetically informative genes, indicated that they represent a new Botrytis species, most closely related to B. elliptica (lily blight, fire blight) which is a major pathogen of cultivated Lilium. The distinction of the isolates was confirmed by morphological analysis of asexual sporulating cultures. Pathogenicity tests on Hemerocallis tissues in vitro demonstrated that this new species was able to induce lesions and rapid tissue necrosis. Based on this data, we infer that this new species, described here as B. deweyae, is likely to be an important contributor to the development of ‘spring sickness’ symptoms. Pathogenesis may be promoted by developmental and environmental factors that favour assault by this necrotrophic pathogen. The emergence of this disease is suggested to have been triggered by breeding-related changes in cultivated hybrids, particularly the erosion of genetic diversity. Our investigation confirms that emergent plant diseases are important and deserve close monitoring, especially in intensively in-bred plants.
Botrytis species: relentless necrotrophic thugs or endophytes gone rogue?
Kan, J.A.L. van; Shaw, M.W. ; Grant-Downton, R.T. - \ 2014
Molecular Plant Pathology 15 (2014)9. - ISSN 1464-6722 - p. 957 - 961.
sclerotinia-sclerotiorum - disease development - oxalic-acid - gray mold - cinerea - plant - infection - flowers - diversity - fruits
Plant pathology has a long-standing tradition of classifying microbes as pathogens, endophytes or saprophytes. Lifestyles of pathogens are categorized as biotrophic, necrotrophic or hemibiotrophic. Botrytis species are considered by many to be archetypal examples of necrotrophic fungi, with B.¿cinerea being the most extensively studied species because of its broad host range and economic impact. In this review, we discuss recent work which illustrates that B.¿cinerea is capable of colonizing plants internally, presumably as an endophyte, without causing any disease or stress symptoms. The extent of the facultative endophytic behaviour of B.¿cinerea and its relevance in the ecology and disease epidemiology may be vastly underestimated. Moreover, we discuss the recent discovery of a novel Botrytis species, B.¿deweyae, which normally grows as an endophyte in ornamental daylilies (Hemerocallis), but displays facultative pathogenic behaviour, and is increasingly causing economic damage. We propose that the emergence of endophytes ‘gone rogue’ as novel diseases may be related to increased inbreeding of hybrid lines and reduced genetic diversity. These observations lead us to argue that the sometimes inflexible classification of pathogenic microbes by their lifestyles requires serious reconsideration. There is much more variety to the interactions of Botrytis with its hosts than the eye (or the plant pathologist) can see, and this may be true for other microbes interacting with plants.
The Brassicaceae-Specific EWR1 Gene Provides Resistance to Vascular Wilt Pathogens
Yadeta, K.A. ; Valkenburg, D.J. ; Hanemian, M. ; Marco, Y. ; Thomma, B.P.H.J. - \ 2014
PLoS ONE 9 (2014)2. - ISSN 1932-6203 - 11 p.
asymmetric interlaced pcr - arabidopsis-thaliana - verticillium wilt - antimicrobial peptides - defense peptides - tomato ve1 - plant - dahliae - disease - proteins
Soil-borne vascular wilt diseases caused by Verticillium spp. are among the most destructive diseases worldwide in a wide range of plant species. The most effective means of controlling Verticillium wilt diseases is the use of genetic resistance. We have previously reported the identification of four activation-tagged Arabidopsis mutants which showed enhanced resistance to Verticillium wilt. Among these, one mutant also showed enhanced resistance to Ralstonia solanacearum, a bacterial vascular wilt pathogen. Cloning of the activation tag revealed an insertion upstream of gene At3g13437, which we designated as EWR1 (for Enhancer of vascular Wilt Resistance 1) that encodes a putatively secreted protein of unknown function. The search for homologs of Arabidopsis EWR1 (AtEWR1) in public databases only identified homologs within the Brassicaceae family. We subsequently cloned the EWR1 homolog from Brassica oleracea (BoEWR1) and show that over-expression in Arabidopsis results in V. dahliae resistance. Moreover, over-expression of AtEWR1 and BoEWR1 in N. benthamiana, a member of the Solanaceae family, results in V. dahliae resistance, suggesting that EWR1 homologs can be used to engineer Verticillium wilt resistance in non-Brassicaceae crops as well.
Diversity of crop development traits and nitrogen use efficiency among potato cultivars grown under contrasting nitrogen regimes
Ospina Nieto, C.A. ; Lammerts Van Bueren, E. ; Allefs, J.J.H.M. ; Engel, B. ; Putten, P.E.L. van der; Linden, C.G. van der; Struik, P.C. - \ 2014
Euphytica 199 (2014)1-2. - ISSN 0014-2336 - p. 13 - 29.
solanum-tuberosum l. - yield response - root-system - dry-matter - nitrate - fertilization - management - quality - index - plant
Potato (Solanum tuberosum L.) requires abundant nitrogen (N) to perform well and has low nitrogen use efficiency (NUE). We assessed phenotypic variation among 189 potato cultivars for NUE and the association between NUE and ecophysiological variables describing canopy development (CDv), under high and low N input. In 2009 and 2010, 189 cultivars were grown with N supply (soil N + fertiliser N) of 75 or 180 kg N/ha at Bant, the Netherlands. CDv was assessed weekly as the percentage of soil covered by green potato leaves (%SC). Data were analysed using a model that described CDv as a function of thermal time, based on the Beta function and estimates of cardinal temperatures. Nitrogen significantly affected model-derived, biologically relevant, curve-fit parameters for each cultivar. The t 1 (i.e., thermal time required to reach maximum soil cover (Vx)) was higher at low than at high N. Other parameters were higher at high than at low N, especially Vx and the period over which it was maintained. Nitrogen also affected tuber dry matter yield, tuber size and weight distributions, N content and N uptake but not tuber dry matter percentage. The total area under the %SC curve was highly correlated with yield in both years. Cultivars performing well under high N also performed well under low N. There was large variation in NUE component traits among cultivars; maturity type partially explained this variation. Variables of the CDv model captured this variation, N effects on light interception and its correlation with yield.
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