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Functional characterization of cucumber (Cucumis sativus L.) Clade V MLO genes
Berg, J.A. ; Appiano, Michela ; Bijsterbosch, G. ; Visser, R.G.F. ; Schouten, H.J. ; Bai, Y. - \ 2017
cucumber - cucumis sativus - powdery mildew - MLO - susceptiblity genes - gene expression
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.
Combined biotic and abiotic stress resistance in tomato
Kissoudis, C. ; Chowdhury, R. ; Heusden, A.W. van; Wiel, C.C.M. van de; Finkers, H.J. ; Visser, R.G.F. ; Bai, Y. ; Linden, C.G. van der - \ 2015
Euphytica 202 (2015)2. - ISSN 0014-2336 - p. 317 - 332.
salt tolerance - oidium-neolycopersici - salinity tolerance - botrytis-cinerea - powdery mildew - abscisic-acid - plant-disease - phenotypic plasticity - solanum-lycopersicon - climate-change
Abiotic and biotic stress factors are the major constrains for the realization of crop yield potential. As climate change progresses, the spread and intensity of abiotic as well as biotic stressors is expected to increase, with increased probability of crops being exposed to both types of stress. Shielding crops from combinatorial stress requires a better understanding of the plant’s response and its genetic architecture. In this study, we evaluated resistance to salt stress, powdery mildew and to both stresses combined in tomato, using the Solanum habrochaites LYC4 introgression line (IL) population. The IL population segregated for both salt stress tolerance and powdery mildew resistance. Using SNP array marker data, QTLs were identified for salt tolerance as well as Na+ and Cl- accumulation. Salt stress increased the susceptibility of the population to powdery mildew in an additive manner. Phenotypic variation for disease resistance was reduced under combined stress as indicated by the coefficient of variation. No correlation was found between disease resistance and Na+ and Cl- accumulation under combined stress Most genetic loci were specific for either salt stress tolerance or powdery mildew resistance. These findings increase our understanding of the genetic regulation of responses to abiotic and biotic stress combinations and can provide leads to more efficiently breeding tomatoes and other crops with a high level of disease resistance while maintaining their performance in combination with abiotic stress.
How Specific is Non-Hypersensitive Host and Nonhost Resistance of Barley to Rust and Mildew Fungi?
Niks, R.E. - \ 2014
Journal of Integrative Agriculture 13 (2014)2. - ISSN 2095-3119 - p. 244 - 254.
quantitative trait loci - near-isogenic lines - powdery mildew - innate immunity - establishing compatibility - disease resistance - biotrophic fungi - puccinia-hordei - iii effector - cowpea rust
Full nonhost resistance can be defined as immunity, displayed by an entire plant species against all genotypes of a plant pathogen. Interesting biological questions are, whether the genes responsible for the nonhost status of a plant species have a general or a specific effectiveness to heterologous (“nonhost”) pathogens? Is the nonhost resistance to pathogens of plant species that are related to the nonhost based on R-genes or on other types of genes? We study this question in barley (Hordeum vulgare L.), which is a near-nonhost to several rusts (Puccinia) of cereals and grasses. By crosses and selection we accumulated susceptibility and developed an experimental line, SusPtrit, with high susceptibility to at least nine different heterologous rust taxa such as the wheat and Agropyron leaf rusts (P. triticina and P. persistens, respectively). At the microscopic level there is also some variation among barley accessions in the degree that the heterologous wheat powdery mildew (Blumeria graminis f.sp. tritici) is able to form haustoria in epidermal cells. So, also the genetics of the variation in level of nonhost resistance to heterologous mildew fungi can be studied in barley. Our data obtained on mapping populations involving three regular nonhost-immune accessions (Vada, Cebada Capa and Golden Promise) suggest that nonhost resistance is the joined effect of multiple, quantitative genes (QTLs) and very occasionally a major gene (R-gene?) is involved. Most QTLs have effect to only one or two heterologous rusts, but some have a wider spectrum. This was confirmed in a set of QTL-NILs. Those QTL-NILs are used to fine-map the effective genes. In some cases, a QTL region with effectiveness to several heterologous rusts might be a cluster of genes with a more narrow spectrum of effectiveness. Our evidence suggests that nonhost resistance in barley to rust and powdery mildew fungi of related Gramineae is not due to R-genes, but to pathogen species-specific quantitative resistance genes.
Plant pathogens structure arthropod communities across multiple spatial and temporal scales
Tack, A.J.M. ; Dicke, M. - \ 2013
Functional Ecology 27 (2013)3. - ISSN 0269-8463 - p. 633 - 645.
tobacco mosaic-virus - weed cirsium-arvense - shared host-plant - induced resistance - mediated interactions - phytopathogenic fungus - phytophagous insects - powdery mildew - rust fungus - interspecific interactions
Plant pathogens and herbivores frequently co-occur on the same host plants. Despite this, little is known about the impact of their interactions on the structure of plant-based ecological communities. Here, we synthesize evidence that indicates that plant pathogens may profoundly impact arthropod performance, preference, population dynamics and community structure across multiple spatial and temporal scales. Intriguingly, the effects of plantpathogenherbivore interactions frequently cascade up and down multiple trophic levels and explain variation in the arthropod community at spatial scales ranging from patterns within single host plants to entire landscapes. This review indicates that knowledge on pathogenherbivore interactions may be crucial for understanding the dynamics of terrestrial communities.
QTLs for resistance to the false brome rust Puccinia brachypodii in the model grass Brachypodium distachyon L.
Barbieri, M. ; Marcel, T.C. ; Niks, R.E. ; Francia, E. ; Pasquariello, M. ; Mazzamurro, V. ; Garvin, D.F. ; Pecchioni, N. - \ 2012
Genome 55 (2012)2. - ISSN 0831-2796 - p. 152 - 163.
agrobacterium-mediated transformation - quantitative trait loci - genetic-linkage map - one major locus - leaf rust - disease resistance - globodera-pallida - powdery mildew - barley genome - stripe rust
The potential of the model grass Brachypodium distachyon L. (Brachypodium) for studying grass–pathogen interactions is still underexploited. We aimed to identify genomic regions in Brachypodium associated with quantitative resistance to the false brome rust fungus Puccinia brachypodii. The inbred lines Bd3-1 and Bd1-1, differing in their level of resistance to P. brachypodii, were crossed to develop an F2 population. This was evaluated for reaction to a virulent isolate of P. brachypodii at both the seedling and advanced growth stages. To validate the results obtained on the F2, resistance was quantified in F2-derived F3 families in two experiments. Disease evaluations showed quantitative and transgressive segregation for resistance. A new AFLP-based Brachypodium linkage map consisting of 203 loci and spanning 812 cM was developed and anchored to the genome sequence with SSR and SNP markers. Three false brome rust resistance QTLs were identified on chromosomes 2, 3, and 4, and they were detected across experiments. This study is the first quantitative trait analysis in Brachypodium. Resistance to P. brachypodii was governed by a few QTLs: two acting at the seedling stage and one acting at both seedling and advanced growth stages. The results obtained offer perspectives to elucidate the molecular basis of quantitative resistance to rust fungi
Compatible Puccinia hordei infection in barley induces basal defense to subsequent infection by Blumeria graminis
Aghnoum, R. ; Niks, R.E. - \ 2012
Physiological and Molecular Plant Pathology 77 (2012)1. - ISSN 0885-5765 - p. 17 - 22.
f-sp-hordei - systemic acquired-resistance - erysiphe-graminis - induced accessibility - powdery mildew - leaf rust - papilla formation - spring barley - cell-death - inaccessibility
Rusts and powdery mildews employ different strategies to suppress defense during penetration. We observed that a compatible interaction of barley-Puccinia hordei induced increased penetration resistance to a challenge infection by powdery mildew. This induced resistance is local and its level is not determined by the virulence spectrum of the challenger isolate. Our data suggest that the inducer effect is due to rust-stoma communication during penetration, to the presence of the rust hyphae in the apoplast, or to penetration resistance mounted by the rust attacked mesophyll cells. We hypothesized that the rust “primes” the basal defense prior to the mildew infection
Mechanisms governing the responses to anthracnose pathogen in Juglans spp.
Pollegioni, P. ; Linden, C.G. van der; Belisario, A. ; Gras, M. ; Anselmi, N. - \ 2012
Journal of Biotechnology 159 (2012)4. - ISSN 0168-1656 - p. 251 - 264.
disease resistance genes - quantitative trait loci - black-walnut - population-genetics - medicago-truncatula - powdery mildew - bud burst - regia l. - binding - identification
Juglans nigra and Juglans regia are two highly economically important species for wood and fruit production that are susceptible to anthracnose caused by Gnomonia leptostyla. The identification of genotypes resistant to anthracnose could represent a valid alternative to agronomic and chemical management. In this study, we analyzed 72 walnut genotypes that showed a variety of resistance phenotypes in response to natural infection. According to the disease severity rating and microsatellite fingerprinting analysis, these genotypes were divided into three main groups: (40) J. nigra resistant, (1) J. nigra susceptible, and (31) J. regia susceptible. Data on leaf emergence rates and analysis of in vivo pathogenicity indicated that the incidence of anthracnose disease in the field might be partially conditioned by two key factors: the age and/or availability of susceptible leaves during the primary infection of fungus (avoidance by late flushing) and partial host resistance. NBS profiling approach, based on PCR amplification with an adapter primer for an adapter matching a restriction enzyme site and a degenerate primer targeting the conserved motifs present in the NBS domain of NBS-LRR genes, was applied. The results revealed the presence of a candidate marker that correlated to a reduction in anthracnose incidence in 72 walnut genotypes
Differential gene expression in nearly isogenic lines with QTL for partial resistance to Puccinia hordei in barley
Chen, X. ; Niks, R.E. ; Hedley, P.E. ; Morris, J. ; Druka, A. ; Marcel, T.C. ; Vels, S.A. ; Waugh, R. - \ 2010
BMC Genomics 11 (2010). - ISSN 1471-2164 - 13 p.
heterologous rust fungi - disease resistance - quantitative resistance - pathogen interactions - rhizoctonia-solani - natural-products - plant immunity - powdery mildew - sheath blight - cell-wall
Background - The barley-Puccinia hordei (barley leaf rust) pathosystem is a model for investigating partial disease resistance in crop plants and genetic mapping of phenotypic resistance has identified several quantitative trait loci (QTL) for partial resistance. Reciprocal QTL-specific near-isogenic lines (QTL-NILs) have been developed that combine two QTL, Rphq2 and Rphq3, the largest effects detected in a recombinant-inbred-line (RIL) population derived from a cross between the super-susceptible line L94 and partially-resistant line Vada. The molecular mechanism underpinning partial resistance in these QTL-NILs is unknown. Results - An Agilent custom microarray consisting of 15,000 probes derived from barley consensus EST sequences was used to investigate genome-wide and QTL-specific differential expression of genes 18 hours post-inoculation (hpi) with Puccinia hordei. A total of 1,410 genes were identified as being significantly differentially expressed across the genome, of which 55 were accounted for by the genetic differences defined by QTL-NILs at Rphq2 and Rphq3. These genes were predominantly located at the QTL regions and are, therefore, positional candidates. One gene, encoding the transcriptional repressor Ethylene-Responsive Element Binding Factor 4 (HvERF4) was located outside the QTL at 71 cM on chromosome 1H, within a previously detected eQTL hotspot for defence response. The results indicate that Rphq2 or Rphq3 contains a trans-eQTL that modulates expression of HvERF4. We speculate that HvERF4 functions as an intermediate that conveys the response signal from a gene(s) contained within Rphq2 or Rphq3 to a host of down-stream defense responsive genes. Our results also reveal that barley lines with extreme or intermediate partial resistance phenotypes exhibit a profound similarity in their spectrum of Ph-responsive genes and that hormone-related signalling pathways are actively involved in response to Puccinia hordei. Conclusions - Differential gene expression between QTL-NILs identifies genes predominantly located within the target region(s) providing both transcriptional and positional candidate genes for the QTL. Genetically mapping the differentially expressed genes relative to the QTL has the potential to discover trans-eQTL mediated regulatory relays initiated from genes within the QTL regions
Peroxidase profiling reveals genetic linkage between peroxidase gene clusters and basal host and non-host resistance to rusts and mildew in barley
Gonzalez, A.M. ; Marcel, T.C. ; Kohutova, Z. ; Stam, P. ; Linden, C.G. van der; Niks, R.E. - \ 2010
PLoS One 5 (2010)8. - ISSN 1932-6203 - 11 p.
class-iii peroxidases - near-isogenic lines - disease resistance - puccinia-hordei - quantitative resistance - arabidopsis-thaliana - powdery mildew - consensus map - expression - diversity
Background - Higher plants possess a large multigene family encoding secreted class III peroxidase (Prx) proteins. Peroxidases appear to be associated with plant disease resistance based on observations of induction during disease challenge and the presence or absence of isozymes in resistant vs susceptible varieties. Despite these associations, there is no evidence that allelic variation of peroxidases directly determines levels of disease resistance. Methodology/Principal Findings - The current study introduces a new strategy called Prx-Profiling. We showed that with this strategy a large number of peroxidase genes can be mapped on the barley genome. In order to obtain an estimate of the total number of Prx clusters we followed a re-sampling procedure, which indicated that the barley genome contains about 40 peroxidase gene clusters. We examined the association between the Prxs mapped and the QTLs for resistance of barley to homologous and heterologous rusts, and to the barley powdery mildew fungus. We report that 61% of the QTLs for partial resistance to P. hordei, 61% of the QTLs for resistance to B. graminis and 47% of the QTLs for non-host resistance to other Puccinia species co-localize with Prx based markers. Conclusions/Significance - We conclude that Prx-Profiling was effective in finding the genetic location of Prx genes on the barley genome. The finding that QTLs for basal resistance to rusts and powdery mildew fungi tend to co-locate with Prx clusters provides a base for exploring the functional role of Prx-related genes in determining natural differences in levels of basal resistance.
An eQTL analysis of partial resistance to Puccinia hordei in barley
Chen, Xinwei ; Hackett, C.A. ; Niks, R.E. ; Hedley, P.E. ; Booth, C. ; Druka, A. ; Marcel, T.C. ; Vels, S.A. ; Bayer, M. ; Milne, I. ; Morris, J. ; Ramsay, L. ; Marshall, D. ; Cardle, L. ; Waugh, R. - \ 2010
PLoS One 5 (2010)1. - ISSN 1932-6203 - 15 p.
quantitative trait locus - density consensus map - false discovery rate - gene-expression - powdery mildew - leaf rust - flowering-time - stem rust - basal defense - arabidopsis
Background - Genetic resistance to barley leaf rust caused by Puccinia hordei involves both R genes and quantitative trait loci. The R genes provide higher but less durable resistance than the quantitative trait loci. Consequently, exploring quantitative or partial resistance has become a favorable alternative for controlling disease. Four quantitative trait loci for partial resistance to leaf rust have been identified in the doubled haploid Steptoe (St)/Morex (Mx) mapping population. Further investigations are required to study the molecular mechanisms underpinning partial resistance and ultimately identify the causal genes.Methodology/Principal Findings - We explored partial resistance to barley leaf rust using a genetical genomics approach. We recorded RNA transcript abundance corresponding to each probe on a 15K Agilent custom barley microarray in seedlings from St and Mx and 144 doubled haploid lines of the St/Mx population. A total of 1154 and 1037 genes were, respectively, identified as being P. hordei-responsive among the St and Mx and differentially expressed between P. hordei-infected St and Mx. Normalized ratios from 72 distant-pair hybridisations were used to map the genetic determinants of variation in transcript abundance by expression quantitative trait locus (eQTL) mapping generating 15685 eQTL from 9557 genes. Correlation analysis identified 128 genes that were correlated with resistance, of which 89 had eQTL co-locating with the phenotypic quantitative trait loci (pQTL). Transcript abundance in the parents and conservation of synteny with rice allowed us to prioritise six genes as candidates for Rphq11, the pQTL of largest effect, and highlight one, a phospholipid hydroperoxide glutathione peroxidase (HvPHGPx) for detailed analysis.Conclusions/Significance - The eQTL approach yielded information that led to the identification of strong candidate genes underlying pQTL for resistance to leaf rust in barley and on the general pathogen response pathway. The dataset will facilitate a systems appraisal of this host-pathogen interaction and, potentially, for other traits measured in this population
Screening of biocontrol agents for control of foliar diseases
Köhl, J. - \ 2009
In: Recent Developments in Management of Plant Diseases / Gisi, U., Chet, I., Gullino, M.L., Dordrecht Heidelberg London New York : Springer (Plant Pathology in the 21st Century, Vol. 1. Vol. 1, part 2) - ISBN 9781402088032 - p. 107 - 119.
apple scab pathogen - venturia-inaequalis - biological-control - botrytis-cinerea - trichoderma-harzianum - ulocladium-atrum - solar-radiation - powdery mildew - aphid honeydew - phyllosphere
Candidate antagonists for the development of biocontrol agents have to fulfill many criteria. The criterion often investigated first in detail is the antagonistic potential of candidates against the target pathogen. However, candidates must also have high ecological competence, must be suitable for an economically feasible production and must be safe in use. Consequently, a broad range of criteria must be tested to fulfill the key factors for success of a biocontrol product. Assays are needed to test such major criteria in simple and inexpensive high throughput systems to exclude candidates in an early stage which may show strong antagonisms but do not fulfill other major criteria for a successful commercialization. The case of a screening program aimed at the biological control of apple scab caused by Venturia inaequalis is presented and discussed. Keywords Biological control - Foliar diseases - Screening - Selection criteria
Patterns of genetic diversity and linkage disequilibrium in a highly structured Hordeum vulgare association-mapping population for the Mediterranean basin
Comodran, J. ; Thomas, W.T.B. ; Eeuwijk, F.A. van; Ceccarelli, S. ; Grando, S. ; Stanca, A.M. ; Pecchioni, N. ; Akar, T. ; Al-Yassin, A. ; Benbelkacem, A. ; Ouabbou, H. ; Bort, J. ; Romagosa, I. ; Hackett, C.A. ; Russel, J.R. - \ 2009
Theoretical and Applied Genetics 119 (2009)1. - ISSN 0040-5752 - p. 175 - 187.
multilocus genotype data - ssp-spontaneum - haplotype structure - powdery mildew - barley - genome - resistance - loci - polymorphism - cultivars
Population structure and genome-wide linkage disequilibrium (LD) were investigated in 192 Hordeum vulgare accessions providing a comprehensive coverage of past and present barley breeding in the Mediterranean basin, using 50 nuclear microsatellite and 1,130 DArT® markers. Both clustering and principal coordinate analyses clearly sub-divided the sample into five distinct groups centred on key ancestors and regions of origin of the germplasm. For given genetic distances, large variation in LD values was observed, ranging from closely linked markers completely at equilibrium to marker pairs at 50 cM separation still showing significant LD. Mean LD values across the whole population sample decayed below r 2 of 0.15 after 3.2 cM. By assaying 1,130 genome-wide DArT® markers, we demonstrated that, after accounting for population substructure, current genome coverage of 1 marker per 1.5 cM except for chromosome 4H with 1 marker per 3.62 cM is sufficient for whole genome association scans. We show, by identifying associations with powdery mildew that map in genomic regions known to have resistance loci, that associations can be detected in strongly stratified samples provided population structure is effectively controlled in the analysis. The population we describe is, therefore, shown to be a valuable resource, which can be used in basic and applied research in barley
Time for a shift in crop production: embracing complexity through diversity at all levels
Ostergard, H. ; Finckh, M.R. ; Fontaine, L. ; Goldringer, I. ; Hoad, S. ; Kristensen, K. ; Lammerts Van Bueren, E. ; Mascher, F. ; Munk, L. ; Wolfe, M.S. - \ 2009
Journal of the Science of Food and Agriculture 89 (2009)9. - ISSN 0022-5142 - p. 1439 - 1445.
earthworms aporrectodea-rosea - soil organic-matter - genotype-environment interactions - ecosystem services - wheat populations - powdery mildew - food security - agricultural sustainability - conservation tillage - carbon sequestration
A radical shift in our approach to crop production is needed to ensure food security and to address the problems of soil degradation, loss of biodiversity, polluted and restricted water supplies, coupled with a future of fossil fuel limitations and increasingly variable climatic conditions. An interdisciplinary network of European scientists put forward visions for future crop production embracing the complexity of our socio-ecological system by applying the principle of diversity at all levels from soil micro-organisms to plant varieties and cropping systems. This approach, integrated with careful deployment of our finite global resources and implementation of appropriate sustainable technology, appears to be the only way to ensure the scale of system resilience needed to cope with many of our concerns. We discuss some of the most important tools such as (i) building soil fertility by recycling of nutrients and sustainable use of other natural and physical resources, (ii) enhancing biological diversity by breeding of crops resilient to climate change and (iii) reconnecting all stakeholders in crop production. Finally, we emphasise some of the changes in agricultural and environmental regulation and policy needed in order to implement the visions.
Genetic dissection of Lactuca saligna nonhost resistance to downy mildew at various lettuce developmental stages
Zhang, N. ; Lindhout, P. ; Niks, R.E. ; Jeuken, M.J.W. - \ 2009
Plant Pathology 58 (2009)5. - ISSN 0032-0862 - p. 923 - 932.
adult-plant stages - backcross inbred lines - bremia-lactucae - puccinia-hordei - field-resistance - wild lactuca - leaf-rust - powdery mildew - grand-rapids - barley
This study used the pathosystem of lettuce (Lactuca spp.) and downy mildew (Bremia lactucae) as a model to investigate the inheritance of nonhost resistance, and focused on the contribution of quantitative trait loci (QTLs) to nonhost resistance at various developmental stages in the lettuce life cycle. A set of 28 backcross inbred lines (BILs) of L. saligna CGN05271 (nonhost) introgressions in a L. sativa cv. Olof (host) background identified 16 introgressions that contributed to resistance at various plant developmental stages: seedlings, young plants, adult plants in the greenhouse and adult plants in the field. This paper provisionally considered these introgressions to be 16 QTLs. Of these 16 QTLs, seven were identified previously and nine were new. For 15 QTLs (Rbq1, Rbq2, rbq3-7 and Rbq8-15), the resistance alleles were derived from the nonhost L. saligna; the resistance allele of the other QTL (Rbq16) was from the susceptible L. sativa cv. Olof. Of the 15 QTLs in L. saligna, only two, rbq5 and rbq7, were found to be effective at every plant developmental stage; the other 13 QTLs were only effective at certain developmental stages. Experiments with seven B. lactucae races did not provide evidence that any QTL was race-specific. The data suggest that nonhost resistance in L. saligna is the result of cumulative effects of many resistance QTLs operating at various developmental stages
Control of seed-borne pathogens on legumes by microbial and other alternative seed treatments
Tinivella, F. ; Hirata, L.M. ; Celan, M.A. ; Wright, S.A.I. ; Amein, T. ; Schmitt, A. ; Wolf, J.M. van der; Koch, E. ; Groot, S.P.C. - \ 2009
European Journal of Plant Pathology 123 (2009)2. - ISSN 0929-1873 - p. 139 - 151.
colletotrichum lindemuthianum - gewasbescherming - biologische bestrijding - plantextracten - ascochyta - geïntegreerde plagenbestrijding - biologische landbouw - zaadbehandeling - plant protection - biological control - plant extracts - integrated pest management - organic farming - seed treatment - growth-promoting rhizobacteria - systemic resistance - powdery mildew - clonostachys-rosea - fusarium-culmorum - bacillus-subtilis - salicylic-acid - root-rot - biocontrol - diseases
Greenhouse trials were carried out in order to test the efficacy of different seed treatments as alternatives to chemicals against Colletotrichum lindemuthianum cause of anthracnose on bean and Ascochyta spp. cause of Ascochyta blights on pea, respectively. Resistance inducers, commercially formulated microorganisms, non-formulated selected strains of different microorganisms (fungi, bacteria and yeasts) and plant extracts were applied as dry or liquid seed treatments on naturally infested seeds. Seedling emergence and disease incidence and/or severity were recorded. Almost all seed treatments turned out to be ineffective in controlling the Ascochyta infections, which is in line with the literature stating that these pathogens are difficult to control. The only alternative treatments that gave some control of Ascochyta spp. were thyme oil and a strain of Clonostachys rosea. The resistance inducers tested successfully controlled infections of bean by C. lindemuthianum. Among the formulated microorganisms, Bacillus subtilis-based formulations provided the best protection from anthracnose. Some strains of Pseudomonas putida, a disease-suppressive, saprophytic strain of Fusarium oxysporum and the mustard powder-based product Tillecur also proved to be effective against bean anthracnose. However, among the resistance inducers as well as among the other groups, certain agents caused a significant reduction of plant emergence. Different alternative seed treatments can therefore be used for the control of C. lindemuthianum on bean, while on pea only thyme oil and a strain of Clonostachys rosea showed some effectiveness against Ascochyta spp.
The Phytophthora infestans avirulence gene Avr4 encodes an RXLR-dEER effector
Poppel, P.M.J.A. van; Jun Guo, J. ; Vondervoort, P.J.I. van de; Jung, M.W.M. ; Birch, P.R.J. ; Whisson, S.C. ; Govers, F. - \ 2008
Molecular Plant-Microbe Interactions 21 (2008)11. - ISSN 0894-0282 - p. 1460 - 1470.
broad-spectrum resistance - late blight resistance - host-plant cells - solanum-bulbocastanum - downy mildew - pathogen phytophthora - secreted proteins - innate immunity - powdery mildew - ipio gene
Resistance in potato against the oomycete Phytophthora infestans is conditioned by resistance (R) genes that are introgressed from wild Solanum spp. into cultivated potato. According to the gene-for-gene model, proteins encoded by R genes recognize race-specific effectors resulting in a hypersensitive response (HR). We isolated P. infestans avirulence gene PiAvr4 using a combined approach of genetic mapping, transcriptional profiling, and bacterial artificial chromosome marker landing. PiAvr4 encodes a 287-amino-acid-protein that belongs to a superfamily of effectors sharing the putative host-cell-targeting motif RXLR-dEER. Transformation of P. infestans race 4 strains with PiAvr4 resulted in transformants that were avirulent on R4 potato plants, demonstrating that PiAvr4 is responsible for eliciting R4-mediated resistance. Moreover, expression of PiAvr4 in R4 plants using PVX agroinfection and agroinfiltration showed that PiAvr4 itself is the effector that elicits HR on R4 but not r0 plants. The presence of the RXLR-dEER motif suggested intracellular recognition of PiAvr4. This was confirmed in agroinfiltration assays but not with PVX agroinfection. Because there was always recognition of PiAvr4 retaining the signal peptide, extracellular recognition cannot be excluded. Deletion of the RXLR-dEER domain neither stimulated nor prevented elicitor activity of PiAvr4. Race 4 strains have frame shift mutations in PiAvr4 that result in truncated peptides; hence, PiAvr4 is apparently not crucial for virulence.
Extensive colonization of apples by smut anamorphs causes a new posthavest disorder
Boekhout, T. ; Gildemacher, P.R. ; Theelen, B. ; Müller, W.H. ; Heijne, B. ; Lutz, M. - \ 2006
FEMS Yeast Research 6 (2006)1. - ISSN 1567-1356 - p. 63 - 76.
powdery mildew - sphaerotheca-fuliginea - bayesian-inference - biological-control - yeasts - fungi - phylloplane - antagonists - microflora - phylogeny
Colonization of apples by ballistoconidium-forming fungi causes a new disorder, here named 'white haze'. White haze may occur in mild form in the field, but only becomes problematic after Ultra-Low Oxygen storage, and, therefore, may be considered as a postharvest disorder. All isolates, obtained using the spore-fall method, were morphologically identified as anamorphs of smut fungi belonging to the genus Tilletiopsis. Sequence analysis of the D1/D2 and the ITS domains of the rDNA revealed nine novel taxa scattered among the Exobasidiomycetidae (Ustilaginomycetes). Field experiments confirmed the erratic incidence of white haze over the years, and the development of the disorder seems to be enhanced at lower temperatures and a high relative humidity. Several scab fungicide treatments showed diminishing effects on the incidence of white haze.
Analysis of summer epidemic progress of apple scab at different apple production systems in the Netherlands and Hungary
Holb, I.J. ; Heijne, B. ; Withagen, J.C.M. ; Gáll, J.M. ; Jeger, M.J. - \ 2005
Phytopathology 95 (2005)9. - ISSN 0031-949X - p. 1001 - 1020.
venturia-inaequalis - disease-progress - powdery mildew - orchards - conidia - resistance - infection - spores - fungus - buds
Two, 4-year studies on summer epidemic progress of apple scab were conducted at Randwijk, the Netherlands, from 1998 until 2001 and at Eperjeske, Hungary, from 2000 until 2003. Disease assessments were made on scab-susceptible cv. Jonagold. A range of nonlinear growth functions were fitted to a total of 96 disease progress curves (3 treatment classes x 2 plant parts x 2 disease measures x 4 years x 2 locations) of apple scab incidence and severity. The three-parameter logistic model gave the most consistent fit across three treatment classes in the experiment (integrated, organic-sprayed, and organic-unsprayed). Parameters estimated or calculated from the three-parameter logistic function were used to analyze disease progress. These were disease incidence and severity on the day of the first assessment (Y-s); final disease incidence or upper asymptote for incidence (Y-if) or severity (Y-sf); fruit incidence and severity on day 40, after which no new lesions on fruits appeared (Y-40); leaf incidence and severity on day 75, at which shoot growth stopped (Y-75); relative (beta) and "absolute" (theta) rates of disease progress; inflection point (M); and area under the disease progress curve (AUDPC(5)) standardized by the duration of the total epidemic. Comparisons among disease progress curves were made by Correlation and factor analysis followed by Varimax rotation. There were large differences but high positive correlations among the parameters Y-s, Y-f, theta, and AUDPC(5) across the three treatment classes. In the factor analysis, two factors accounted for more than 85% of the total variance for both incidence and severity. Factor I gave an overall description of epidemic progress of both scab incidence and severity and included the parameters Y-f, Y-40, Y-75, theta, and AUDPCs. Factor 2 identified a relationship between the relative rate parameter (P) and the inflection point (M) for severity and a relationship between disease incidence and severity. For an integrated or an organic orchard, theta, AUDPC(5), and one of Y-f or Y-75 (because of the link with host phenology) can characterize apple scab epidemics during summer. Based on these findings, improved scab management approaches were provided for integrated and organic apple production systems.
Dispersal of Venturia inaequalis ascospores and disease gradients from a defined inoculum source
Holb, I.J. ; Heijne, B. ; Withagen, J.C.M. ; Jeger, M.J. - \ 2004
Journal of Phytopathology 152 (2004)11-12. - ISSN 0931-1785 - p. 639 - 646.
combating apple scab - eradicant fungicides - aerial concentration - powdery mildew - wind - epidemics - orchards - release - conidia - spores
Aerial concentration of ascospores of Venturia inaequalis and incidence of apple scab were monitored in an orchard during the ascospore release seasons in 1999, 2000 and 2001 on susceptible (Jonagold) and moderately resistant (Schone van Boskoop) apple cultivars. A 1-ha orchard was divided into an inoculum source block (approximately 0.34 ha) and an inoculum-free block (approximately 0.66 ha) where inoculum was excluded by covering the soil surface with polythene sheets. Ascospore numbers and disease incidence were measured within the inoculum-free block at different distances from the inoculum block. Ascospores were sampled with three Burkard volumetric spore traps located at 0, 21 and 45 m from the border of the inoculum block. To determine the incidence of infection, clusters of leaves were assessed at six distances from the border of the infected source from the time the first symptoms appeared. Each year, the aerial ascospore concentration significantly decreased with distance from the source, as did the incidence of infected clusters. Cultivar susceptibility to apple scab markedly influenced incidence of infected clusters and disease gradients. The effect of horizontal distance from the source was identifiable up to 18 m and 33 m for cv. Schone van Boskoop and cv. Jonagold, respectively, beyond which disease was negligible. The disease gradients for cultivar Jonagold in 1999, 2000 and 2001 were well described by an exponential model with gradient coefficients of -0.036, -0.042 and -0.047, respectively. The number of infected clusters at the source border for this cultivar differed significantly over the 3 years. A single exponential model with a gradient coefficient of -0.035 adequately described the disease gradients for cultivar Schone van Boskoop in each of the 3 years. Further analysis showed highly significant correlations (r > 0.85, P <0.01) between the annual cumulative spore catches and the annual mean number of infected leaf clusters in each year and for both cultivars. The aerobiological and epidemiological implications of these findings are discussed.