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Staff Publications

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

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

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

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    A comparative analysis of nonhost resistance across the two Triticeae crop species wheat and barley
    Delventhal, Rhoda ; Rajaraman, Jeyaraman ; Stefanato, Francesca L. ; Rehman, S. ; Aghnoum, R. ; McGrann, Graham R.D. ; Bolger, Marie ; Usadel, Björn ; Hedley, Pete E. ; Boyd, Lesley A. ; Niks, R.E. ; Schweizer, Patrick ; Schaffrath, Ulrich - \ 2017
    RWTH Aachen University
    wheat - barley - Blumeria - Magnaporthe - Puccinia - adapted isolate - non-adapted isolate - nonhost resistance - quantitative resistance - global transcriptome analysis
    Background Nonhost resistance (NHR) protects plants against a vast number of non-adapted pathogens which implicates a potential exploitation as source for novel disease resistance strategies. Aiming at a fundamental understanding of NHR a global analysis of transcriptome reprogramming in the economically important Triticeae cereals wheat and barley, comparing host and nonhost interactions in three major fungal pathosystems responsible for powdery mildew (Blumeria graminis ff. ssp.), cereal blast (Magnaporthe sp.) and leaf rust (Puccinia sp.) diseases, was performed. Results In each pathosystem a significant transcriptome reprogramming by adapted- or non-adapted pathogen isolates was observed, with considerable overlap between Blumeria, Magnaporthe and Puccinia. Small subsets of these general pathogen-regulated genes were identified as differentially regulated between host and corresponding nonhost interactions, indicating a fine-tuning of the general pathogen response during the course of co-evolution. Additionally, the host- or nonhost-related responses were rather specific for each pair of adapted and non-adapted isolates, indicating that the nonhost resistance-related responses were to a great extent pathosystem-specific. This pathosystem-specific reprogramming may reflect different resistance mechanisms operating against non-adapted pathogens with different lifestyles, or equally, different co-option of the hosts by the adapted isolates to create an optimal environment for infection. To compare the transcriptional reprogramming between wheat and barley, putative orthologues were identified. Within the wheat and barley general pathogen-regulated genes, temporal expression profiles of orthologues looked similar, indicating conserved general responses in Triticeae against fungal attack. However, the comparison of orthologues differentially expressed between host and nonhost interactions revealed fewer commonalities between wheat and barley, but rather suggested different host or nonhost responses in the two cereal species. Conclusions Taken together, our results suggest independent co-evolutionary forces acting on host pathosystems mirrored by barley- or wheat-specific nonhost responses. As a result of evolutionary processes, at least for the pathosystems investigated, NHR appears to rely on rather specific plant responses.
    A mixed-model QTL analysis for salt tolerance in seedlings of crop-wild hybrids of lettuce
    Wei, Z. ; Julkowska, M.M. ; Laloe, J.O. ; Hartman, Y. ; Boer, G.J. ; Michelmore, R.W. ; Tienderen, P.H. van; Testerink, C. ; Schranz, M.E. - \ 2014
    Molecular Breeding 34 (2014)3. - ISSN 1380-3743 - p. 1389 - 1400.
    quantitative trait loci - root-system architecture - salinity tolerance - high-density - plant-root - nonhost resistance - lactuca-saligna - downy mildew - linkage maps - bread wheat
    Cultivated lettuce is more sensitive to salinity stress than its wild progenitor species potentially due to differences in root architecture and/or differential uptake and accumulation of sodium. We have identified quantitative trait locis (QTLs) associated with salt-induced changes in root system architecture (RSA) and ion accumulation using a recombinant inbred line population derived from a cross between cultivated lettuce (Lactuca sativa ‘Salinas’) and wild lettuce (L. serriola). Components of RSA were quantified by replicated measurements of seedling growth on vertical agar plates containing different concentrations of NaCl in a controlled growth chamber environment. Accumulation of sodium and potassium ions was measured in replicates of greenhouse-grown plants watered with 100 mM NaCl water. A total of 14 QTLs were identified using multi-trait linkage analysis, including three major QTLs associated with general root development, root growth in salt stress condition, and ion accumulation. The three major QTLs, qRC9.1, qRS2.1, and qLS7.2, were linked with markers E35/M59-F-425, LE9050, and LE1053, respectively. This study provides regions of lettuce genome contributing to salt-induced changes in RSA and ion accumulation. Future fine-mapping of major QTLs will identify candidate genes underlying salt stress tolerance in cultivated lettuce.
    Effects of stacked quantitative resistances to downy mildew in lettuce do not simply add up
    Boer, E. den; Pelgrom, K.T.B. ; Zhang, N. ; Visser, R.G.F. ; Niks, R.E. ; Jeuken, M.J.W. - \ 2014
    Theoretical and Applied Genetics 127 (2014)8. - ISSN 0040-5752 - p. 1805 - 1816.
    backcross inbred lines - lactuca-saligna - bremia-lactucae - epistatic interactions - trait loci - 3 qtls - nonhost resistance - isogenic lines - heading date - wild lettuce
    Key message In a stacking study of eight resistance QTLs in lettuce against downy mildew, only three out of ten double combinations showed an increased resistance effect under field conditions. Abstract Complete race nonspecific resistance to lettuce downy mildew, as observed for the nonhost wild lettuce species Lactuca saligna, is desired in lettuce cultivation. Genetic dissection of L. saligna’s complete resistance has revealed several quantitative loci (QTL) for resistance with field infection reductions of 30–50 %. To test the effect of stacking these QTL, we analyzed interactions between homozygous L. saligna CGN05271 chromosome segments introgressed into the genetic background of L. sativa cv. Olof. Eight different backcross inbred lines (BILs) with single introgressions of 30–70 cM and selected predominately for quantitative resistance in field situations were intercrossed. Ten developed homozygous lines with stacked introgression segments (double combinations) were evaluated for resistance in the field. Seven double combinations showed a similar infection as the individual most resistant parental BIL, revealing epistatic interactions with ‘less-than-additive’ effects. Three double combinations showed an increased resistance level compared to their parental BILs and their interactions were additive, ‘less-than-additive’ epistatic and ‘more-than-additive’ epistatic, respectively. The additive interaction reduced field infection by 73 %. The double combination with a ‘morethan-additive’ epistatic effect, derived from a combination between a susceptible and a resistant BIL with 0 and 30 % infection reduction, respectively, showed an average field infection reduction of 52 %. For the latter line, an attempt to genetically dissect its underlying epistatic loci by substitution mapping did not result in smaller mapping intervals as none of the 22 substitution lines reached a similar high resistance level. Implications for breeding and the inheritance of L. saligna’s complete resistance are discussed.
    Golden SusPtrit: a genetically well transformable barley line for studies on the resistance to rust fungi
    Yeo Kuok San, F. ; Hensel, G. ; Vozábová, T. ; Martin-Sanz, A. ; Marcel, T.C. ; Kumlehn, J. ; Niks, R.E. - \ 2014
    Theoretical and Applied Genetics 127 (2014)2. - ISSN 0040-5752 - p. 325 - 337.
    quantitative trait loci - puccinia-hordei - mediated transformation - disease resistance - nonhost resistance - brassica-oleracea - pathogens - genes - defense - qtls
    Nonhost and partial resistance to Puccinia rust fungi in barley are polygenically inherited. These types of resistance are principally prehaustorial, show high diversity between accessions of the plant species and are genetically associated. To study nonhost and partial resistance, as well as their association, candidate gene(s) for resistance must be cloned and tested in susceptible material where SusPtrit would be the line of choice. Unfortunately, SusPtrit is not amenable to Agrobacterium-mediated transformation. Therefore, a doubled haploid (DH) mapping population (n = 122) was created by crossing SusPtrit with Golden Promise to develop a ‘Golden SusPtrit’, i.e., a barley line combining SusPtrit’s high susceptibility to non-adapted rust fungi with the high amenability of Golden Promise for transformation. We identified nine genomic regions occupied by resistance quantitative trait loci (QTLs) against four non-adapted rust fungi and P. hordei isolate 1.2.1 (Ph.1.2.1). Four DHs were selected for an Agrobacterium-mediated transformation efficiency test. They were among the 12 DH lines most susceptible to the tested non-adapted rust fungi. The most efficiently transformed DH line was SG062N (11–17 transformants per 100 immature embryos). The level of non-adapted rust infection on SG062N is either similar to or higher than the level of infection on SusPtrit. Against Ph.1.2.1, the latency period conferred by SG062N is as short as that conferred by SusPtrit. SG062N, designated ‘Golden SusPtrit’, will be a valuable experimental line that could replace SusPtrit in nonhost and partial resistance studies, especially for stable transformation using candidate genes that may be involved in rust-resistance mechanisms.
    Fine mapping quantitative resistances to downy mildew in lettuce revealed multiple sub-QTLs with plant stage dependent effects reducing or even promoting the infection
    Boer, E. den; Zhang, N. ; Pelgrom, K.T.B. ; Visser, R.G.F. ; Niks, R.E. ; Jeuken, M.J.W. - \ 2013
    Theoretical and Applied Genetics 126 (2013)12. - ISSN 0040-5752 - p. 2995 - 3007.
    backcross inbred lines - trait locus qtl - bremia-lactucae - leaf rust - durable resistance - stripe rust - genetic dissection - disease resistance - nonhost resistance - wild lettuce
    Previous studies on the genetic dissection of the complete resistance of wild lettuce, Lactuca saligna, to downy mildew revealed 15 introgression regions that conferred plant stage dependent quantitative resistances (QTLs). Three backcross inbred lines (BILs), carrying an individual 30–50 cM long introgression segment from L. saligna in a cultivated lettuce, L. sativa, background, reduced infection by 60–70 % at young plant stage and by 30–50 % at adult plant stage in field situations. We studied these three quantitative resistances in order to narrow down their mapping interval and determine their number of loci, either single or multiple. We performed recombinant screenings and developed near isogenic lines (NILs) with smaller overlapping L. saligna introgressions (substitution mapping). In segregating introgression line populations, recombination was suppressed up to 17-fold compared to the original L. saligna × L. sativaF2 population. Recombination suppression depended on the chromosome region and was stronger suppressed at the smallest introgression lengths. Disease evaluation of the NILs revealed that the resistance of all three BILs was not explained by a single locus but by multiple sub-QTLs. The 17 L. saligna-derived sub-QTLs had a smaller and plant stage dependent resistance effect, some segments reducing; others even promoting downy mildew infection. Implications for lettuce breeding are outlined.
    Specific In Planta Recognition of Two GKLR Proteins of the Downy Mildew Bremia lactucae Revealed in a Large Effector Screen in Lettuce
    Stassen, J.H.M. ; Boer, E. den; Vergeer, P.W.J. ; Andel, A. ; Ellendorff, U. ; Pelgrom, K.T.B. ; Pel, M. ; Schut, J. ; Zonneveld, O. ; Jeuken, M.J.W. ; Ackerveken, G. van den - \ 2013
    Molecular Plant-Microbe Interactions 26 (2013)11. - ISSN 0894-0282 - p. 1259 - 1270.
    backcross inbred lines - genetic-linkage map - disease resistance - phytophthora-infestans - nonhost resistance - avirulence genes - wild lettuce - pathogen - saligna - potato
    Breeding lettuce (Lactuca sativa) for resistance to the downy mildew pathogen Bremia lactucae is mainly achieved by introgression of dominant downy mildew resistance (Dm) genes. New Bremia races quickly render Dm genes ineffective, possibly by mutation of recognized host-translocated effectors or by suppression of effector-triggered immunity. We have previously identified 34 potential RXLR(-like) effector proteins of B. lactucae that were here tested for specific recognition within a collection of 129 B. lactucae-resistant Lactuca lines. Two effectors triggered a hypersensitive response: BLG01 in 52 lines, predominantly L. saligna, and BLG03 in two L. sativa lines containing Dm2 resistance. The N-terminal sequences of BLG01 and BLG03, containing the signal peptide and GKLR variant of the RXLR translocation motif, are not required for in planta recognition but function in effector delivery. The locus responsible for BLG01 recognition maps to the bottom of lettuce chromosome 9, whereas recognition of BLG03 maps in the RGC2 cluster on chromosome 2. Lactuca lines that recognize the BLG effectors are not resistant to Bremia isolate Bl:24 that expresses both BLG genes, suggesting that Bl:24 can suppress the triggered immune responses. In contrast, lettuce segregants displaying Dm2-mediated resistance to Bremia isolate Bl:5 are responsive to BLG03, suggesting that BLG03 is a candidate Avr2 protein.
    Loss of Function in Mlo Orthologs Reduces Susceptibility of Pepper and Tomato to Powdery Mildew Disease Caused by Leveillula taurica
    Zheng, Z. ; Nonomura, T. ; Appiano, M. ; Pavan, S.N.C. ; Matsuda, Y. ; Toyoda, H. ; Wolters, A.M.A. ; Visser, R.G.F. ; Bai, Y. - \ 2013
    PLoS ONE 8 (2013)7. - ISSN 1932-6203 - 14 p.
    real-time pcr - capsicum-annuum - subcellular-localization - nonhost resistance - gene-expression - oryza-sativa - cell-death - barley - family - identification
    Powdery mildew disease caused by Leveillula taurica is a serious fungal threat to greenhouse tomato and pepper production. In contrast to most powdery mildew species which are epiphytic, L. taurica is an endophytic fungus colonizing the mesophyll tissues of the leaf. In barley, Arabidopsis, tomato and pea, the correct functioning of specific homologues of the plant Mlo gene family has been found to be required for pathogenesis of epiphytic powdery mildew fungi. The aim of this study was to investigate the involvement of the Mlo genes in susceptibility to the endophytic fungus L. taurica. In tomato (Solanum lycopersicum), a loss-of-function mutation in the SlMlo1 gene results in resistance to powdery mildew disease caused by Oidium neolycopersici. When the tomato Slmlo1 mutant was inoculated with L. taurica in this study, it proved to be less susceptible compared to the control, S. lycopersicum cv. Moneymaker. Further, overexpression of SlMlo1 in the tomato Slmlo1 mutant enhanced susceptibility to L. taurica. In pepper, the CaMlo2 gene was isolated by applying a homology-based cloning approach. Compared to the previously identified CaMlo1 gene, the CaMlo2 gene is more similar to SlMlo1 as shown by phylogenetic analysis, and the expression of CaMlo2 is up-regulated at an earlier time point upon L. taurica infection. However, results of virus-induced gene silencing suggest that both CaMlo1 and CaMlo2 may be involved in the susceptibility of pepper to L. taurica. The fact that overexpression of CaMlo2 restored the susceptibility of the tomato Slmlo1 mutant to O. neolycopersici and increased its susceptibility to L. taurica confirmed the role of CaMlo2 acting as a susceptibility factor to different powdery mildews, though the role of CaMlo1 as a co-factor for susceptibility cannot be excluded.
    Convergent evidence for a role of WIR1 proteins during the interaction of barley with the powdery mildew fungus Blumeria graminis
    Douchkov, Dimitar ; Johrde, A. ; Nowara, D. ; Himmelbach, A. ; Lueck, S. ; Niks, R.E. ; Schweizer, P. - \ 2011
    Journal of Plant Physiology 168 (2011)1. - ISSN 0176-1617 - p. 20 - 29.
    basal host-resistance - defense-related genes - disease-resistance - functional assessment - winter-wheat - cell-death - f-sp - pathogen resistance - magnaporthe-grisea - nonhost resistance
    Pathogen attack triggers a multifaceted defence response in plants that includes the accumulation of pathogenesis-related proteins and their corresponding transcripts. One of these transcripts encodes for WIR1, a small glycine- and proline-rich protein of unknown function that appears to be specific to grass species. Here we describe members of the HvWIR1 multigene family of barley with respect to phylogenetic relationship, transcript regulation, co-localization with quantitative trait loci for resistance to the barley powdery mildew fungus Blumeria graminis (DC.) E.O. Speer f.sp. hordei, the association of single nucleotide polymorphisms or gene haplotypes with resistance, as well as phenotypic effects of gene silencing by RNAi. HvWIR1 is encoded by a multigene family of moderate complexity that splits up into two major clades, one of those being also represented by previously described cDNA sequences from wheat. All analysed WIR1 transcripts accumulated in response to powdery mildew attack in leaves and all mapped WIR1 genes were associated with quantitative trait loci for resistance to B. graminis. Moreover, single nucleotide polymorphisms or haplotypes of WIR1 members were associated with quantitative resistance of barley to B. graminis, and transient WIR1 gene silencing affected the interaction of epidermal cells with the pathogen. The presented data provide convergent evidence for a role of the HvWIR1a gene and possibly other family members, during the interaction of barley with B. graminis
    Loss of susceptibility as a novel breeding strategy for durable and broad-spectrum resistance
    Pavan, S.N.C. ; Jacobsen, E. ; Visser, R.G.F. ; Bai, Y. - \ 2010
    Molecular Breeding 25 (2010). - ISSN 1380-3743 - p. 1 - 12.
    powdery mildew resistance - systemic acquired-resistance - oryzae pv. oryzae - arabidopsis mutant cev1 - initiation-factor eif4e - lettuce-mosaic-virus - yellow-mottle-virus - gated ion-channel - barley mlo-gene - nonhost resistance
    Recent studies on plant immunity have suggested that a pathogen should suppress induced plant defense in order to infect a plant species, which otherwise would have been a nonhost to the pathogen. For this purpose, pathogens exploit effector molecules to interfere with different layers of plant defense responses. In this review, we summarize the latest findings on plant factors that are activated by pathogen effectors to suppress plant immunity. By looking from a different point of view into host and nonhost resistance, we propose a novel breeding strategy: disabling plant disease susceptibility genes (S-genes) to achieve durable and broad-spectrum resistance
    Basal host resistance of barley to powdery mildew: connecting quantitative trait loci and candidate genes
    Aghnoum, R. ; Marcel, T.C. ; Johrde, A. ; Pecchioni, N. ; Schweizer, P. ; Niks, R.E. - \ 2010
    Molecular Plant-Microbe Interactions 23 (2010)1. - ISSN 0894-0282 - p. 91 - 102.
    heterologous rust fungi - head blight resistance - defense-related genes - hordeum-vulgare l - pisum-sativum l. - disease-resistance - leaf rust - nonhost resistance - puccinia-hordei - spring barley
    The basal resistance of barley to powdery mildew (Blumeria graminis f. sp. hordei) is a quantitatively inherited trait that is based on nonhypersensitive mechanisms of defense. A functional genomic approach indicates that many plant candidate genes are involved in the defense against formation of fungal haustoria. It is not known which of these candidate genes have allelic variation that contributes to the natural variation in powdery mildew resistance, because many of them may be highly conserved within the barley species and may act downstream of the basal resistance reaction. Twenty-two expressed sequence tag or cDNA clone sequences that are likely to play a role in the barley-Blumeria interaction based on transcriptional profiling, gene silencing, or overexpression data, as well as mlo, Ror1, and Ror2, were mapped and considered candidate genes for contribution to basal resistance. We mapped the quantitative trait loci (QTL) for powdery mildew resistance in six mapping populations of barley at seedling and adult plant stages and developed an improved high-density integrated genetic map containing 6,990 markers for comparing QTL and candidate gene positions over mapping populations. We mapped 12 QTL at seedling stage and 13 QTL at adult plant stage, of which four were in common between the two developmental stages. Six of the candidate genes showed coincidence in their map positions with the QTL identified for basal resistance to powdery mildew. This co-localization justifies giving priority to those six candidate genes to validate them as being responsible for the phenotypic effects of the QTL for basal resistance
    Actin-Depolymerizing Factor2-Mediated Actin Dynamics Are Essential for Root-Knot Nematode Infection of Arabidopsis
    Clement, M. ; Ketelaar, T. ; Rodiuc, N. ; Banora, M.Y. ; Smertenko, A. ; Engler, G. ; Abad, P. ; Hussey, P.J. ; Almeida Engler, J. De - \ 2009
    The Plant Cell 21 (2009)9. - ISSN 1040-4651 - p. 2963 - 2979.
    plant-parasitic nematodes - filament turnover - nonhost resistance - in-vivo - adf/cofilin family - gene-expression - cell periphery - maize actin - giant-cells - cytoskeleton
    Reorganization of the actin and microtubule networks is known to occur in targeted vascular parenchymal root cells upon infection with the nematode Meloidogyne incognita. Here, we show that actin-depolymerizing factor (ADF) is upregulated in the giant feeding cells of Arabidopsis thaliana that develop upon nematode infection and that knockdown of a specific ADF isotype inhibits nematode proliferation. Analysis of the levels of transcript and the localization of seven ADF genes shows that five are upregulated in galls that result from the infection and that ADF2 expression is particularly increased between 14 and 21 d after nematode inoculation. Further analysis of ADF2 function in inducible RNA interference lines designed to knock down ADF2 expression reveals that this protein is required for normal cell growth and plant development. The net effect of decreased levels of ADF2 is F-actin stabilization in cells, resulting from decreased F-actin turnover. In nematode-infected plants with reduced levels of ADF2, the galls containing the giant feeding cells and growing nematodes do not develop due to the arrest in growth of the giant multinucleate feeding cells, which in turn is due to an aberrant actin network
    Plant invaders and their novel natural enemies: who is naive?
    Verhoeven, K.J.F. ; Biere, A. ; Harvey, J.A. ; Putten, W.H. van der - \ 2009
    Ecology Letters 12 (2009)2. - ISSN 1461-023X - p. 107 - 117.
    invasive exotic plants - release hypothesis - insect herbivores - biotic resistance - soil pathogens - secondary metabolites - competitive ability - ammophila-arenaria - nonhost resistance - biological-control
    Introduced exotic species encounter a wide range of non-coevolved enemies and competitors in their new range. Evolutionary novelty is a key aspect of these interactions, but who benefits from novelty: the exotic species or their new antagonists? Paradoxically, the novelty argument has been used to explain both the release from and the suppression by natural enemies. We argue that this paradox can be solved by considering underlying interaction mechanisms. Using plant defenses as a model, we argue that mismatches between plant and enemy interaction traits can enhance plant invasiveness in the case of toxin-based defenses, whereas invasiveness is counteracted by mismatches in recognition-based defenses and selective foraging of generalist herbivores on plants with rare toxins. We propose that a mechanistic understanding of ecological mismatches can help to explain and predict when evolutionary novelty will enhance or suppress exotic plant invasiveness. This knowledge may also enhance our understanding of plant abundance following range expansion, or during species replacements along successional stages
    Rin4 Causes Hybrid Necrosis and Race-Specific Resistance in an Interspecific Lettuce Hybrid
    Jeuken, M.J.W. ; Zhang, N. ; McHale, L.K. ; Pelgrom, K.T.B. ; Boer, E. den; Lindhout, P. ; Michelmore, R. ; Visser, R.G.F. ; Niks, R.E. - \ 2009
    The Plant Cell 21 (2009)10. - ISSN 1040-4651 - p. 3368 - 3378.
    cf-2-dependent disease resistance - backcross inbred lines - lactuca-saligna - bremia-lactucae - nonhost resistance - effector avrrpt2 - gene-expression - downy mildew - wild lettuce - arabidopsis
    Some inter- and intraspecific crosses may result in reduced viability or sterility in the offspring, often due to genetic incompatibilities resulting from interactions between two or more loci. Hybrid necrosis is a postzygotic genetic incompatibility that is phenotypically manifested as necrotic lesions on the plant. We observed hybrid necrosis in interspecific lettuce (Lactuca sativa and Lactuca saligna) hybrids that correlated with resistance to downy mildew. Segregation analysis revealed a specific allelic combination at two interacting loci to be responsible. The allelic interaction had two consequences: (1) a quantitative temperature-dependent autoimmunity reaction leading to necrotic lesions, lethality, and quantitative resistance to an otherwise virulent race of Bremia lactucae; and (2) a qualitative temperature-independent race-specific resistance to an avirulent race of B. lactucae. We demonstrated by transient expression and silencing experiments that one of the two interacting genes was Rin4. In Arabidopsis thaliana, RIN4 is known to interact with multiple R gene products, and their interactions result in hypersensitive resistance to Pseudomonas syringae. Site-directed mutation studies on the necrosis-eliciting allele of Rin4 in lettuce showed that three residues were critical for hybrid necrosis
    Resistance to cereal rusts at the plant cell wall - what can we learn from other host-pathogen systems?
    Collins, N.C. ; Niks, R.E. ; Schulze-Lefert, P. - \ 2007
    Australian Journal of Agricultural Research 58 (2007)6. - ISSN 0004-9409 - p. 476 - 489.
    powdery mildew resistance - barley epidermal-cells - disease resistance - nonhost resistance - puccinia-hordei - arabidopsis-thaliana - stripe rust - gene-expression - tip necrosis - subcellular-localization
    The ability of plant cells to resist invasion by pathogenic fungi at the cell periphery (pre-invasion resistance) differs from other types of resistance that are generally triggered after parasite entry and during differentiation of specialised intracellular feeding structures. Genetic sources of pre-invasion resistance such as mlo for barley powdery mildew and Lr34 for resistance to wheat leaf rust have proven to be broad-spectrum in effect and durable in the field. Continued breeding for this type of resistance (often quantitative in effect) is therefore considered an important strategy to protect cereal crops long-term against potentially devastating fungal diseases such as rusts. Considerable progress has been made in characterising genes and processes underlying pre-invasion resistance using mutant analysis, molecular genetics, gene cloning, and the model plant Arabidopsis, as well as comparative functional analysis of genes in Arabidopsis and cereals. This review summarises the current knowledge in this field, and discusses several aspects of pre-invasion resistance potentially pertinent to use in breeding; namely, biological cost of the resistance and effectiveness of individual resistance genes against multiple pathogen types. We show that mutations in Mlo, Ror1, and Ror2 genes known to affect powdery mildew pre-invasion resistance have no detectable effect on partial resistance to barley leaf rust as measured by latency period.
    The Arabidopsis defence response mutant esa1 as a tool to discover novel resistance traits against Fusarium diseases
    Hemelrijck, W. van; Wouters, P.F.J. ; Brouwer, M. ; Windelinckx, A. ; Goderis, I.J.W.M. ; Bolle, M.F.C. De; Thomma, B.P.H.J. ; Cammue, B.P.A. ; Delauré, S.L. - \ 2006
    Plant Science 171 (2006)5. - ISSN 0168-9452 - p. 585 - 595.
    in-vitro differentiation - f-sp cubense - enhanced resistance - bacterial diseases - nonhost resistance - fungal pathogens - head blight - plants - gene - oxysporum
    The Arabidopsis thaliana mutant esa1 was previously shown to exhibit enhanced susceptibility to the necrotrophic fungal pathogens Alternaria brassicicola, Botrytis cinerea and Plectosphaerella cucumerina. In this work, we tried to elaborate on this susceptibility by investigating whether the esa1 phenotype can be extended to Fusarium species, a genus that includes several economically relevant pathogens. We show that the esa1 mutant exhibits increased susceptibility to several Fusarium species, including Fusarium oxysporum f. sp. matthiolae, F. solani, and F. culmorum. Furthermore, we show that the causal agent of the Panama disease on banana, F. oxysporum f. sp. cubense, a pathogen for which wild-type A. thaliana shows non-host resistance, causes enhanced lesion formation on esa1 as compared to wild-type plants, suggesting that esa1 is more sensitive to F. oxysporum f. sp. cubense. In addition, we were able to show that the A. thaliana wild-type resistance phenotype towards the latter pathogen can be partially restored by expression of the pathogenesis-related proteins PR1 or PR5 from tobacco in esa1, suggesting that PR1 and/or PR5 expression may be useful traits to obtain enhanced resistance to F. oxysporum f. sp. cubense in banana. As such, esa1 proves to be an ideal model system for research on the plant's defense response against fungal pathogens in general and Fusarium species in particular
    Differences in intensity and specificity of hypersensitive response induction in Nicotiana spp. by INF1, INF2A, and INF2B of Phytophthora infestans
    Huitema, E. ; Vleeshouwers, V.G.A.A. ; Cakir, C. ; Kamoun, S. ; Govers, F. - \ 2005
    Molecular Plant-Microbe Interactions 18 (2005)3. - ISSN 0894-0282 - p. 183 - 193.
    plant-disease resistance - fungal elicitor cryptogein - sterol carrier protein - potato-virus-x - nonhost resistance - pathogen phytophthora - gene-expression - functional expression - molecular-genetics - defense responses
    Elicitins form a family of structurally related proteins that induce the hypersensitive response (HR) in plants, particularly Nicotiana spp. The elicitin family is composed of several classes. Most species of the plant-pathogenic oomycete genus Phytophthora produce the well-characterized 10-kDa canonical elicitins (class I), such as INF1 of the potato and tomato pathogen Phytophthora infestans. Two genes, inf2A and inf2B, encoding a distinct class (class III) of elicitin-like proteins, also occur in P. infestans. Unlike secreted class I elicitins, class III elicitins are thought to be cell-surface-anchored polypeptides. Molecular characterization of the inf2 genes indicated that they are widespread in Phytophthora spp. and occur as a small gene family. In addition, Southern blot and Northern blot hybridizations using gene-specific probes showed that inf2A and inf2B genes and transcripts can be detected in 17 different P. infestans isolates. Functional secreted expression in plant cells of the elicitin domain of the inf1 and inf2 genes was conducted using a binary Potato virus X (PVX) vector (agroinfection) and Agrobacterium tumefaciens transient transformation assays (agroinfiltration), and resulted in HR-like necrotic symptoms and induction of defense response genes in tobacco. However, comparative analyses of elicitor activity of INF1, INF2A, and INF2B revealed significant differences in intensity, specificity, and consistency of HR induction. Whereas INF1 induced the HR in Nicotiana benthamiana, INF2A induced weak symptoms and INF2B induced no symptoms on this plant. Nonetheless, similar to INF1, HR induction by INF2A in N. benthamiana required the ubiquitin ligase-associated protein SGT1. Overall, these results suggest that variation in the resistance of Nicotiana spp. to P. infestans is shadowed by variation in the response to INF elicitins. The ability of tobacco, but not N. benthamiana, to respond to INF2B could explain differences in resistance to P. infestans observed for these two species.
    Lactuca saligna, a non-host for lettuce downy mildew (Bremia lactucae), harbors a new race-specific Dm gene and three QTL's for resistance
    Jeuken, M.J.W. ; Lindhout, P. - \ 2002
    Theoretical and Applied Genetics 105 (2002)2-3. - ISSN 0040-5752 - p. 384 - 391.
    nonhost resistance - wild lactuca - sativa - phytophthora - recognition - populations - genotypes - serriola - plants - level
    Lactuca sativa (lettuce) is susceptible to Bremia lactucae (downy mildew). In cultivated and wild Lactuca species, Dm genes have been identified that confer race-specific resistance. However, these genes were soon rendered ineffective by adaptation of the pathogen. Lactuca saligna (wild lettuce) is resistant to all downy mildew races and can be considered as a non-host. Therefore, L. saligna might be an alternative source for a more-durable resistance to downy mildew in lettuce. In order to analyze this resistance, we have developed an F2 population based on a resistant L. saligna 2 susceptible L. sativa cross. This F2 population was fingerprinted with AFLP markers and tested for resistance to two Bremia races NL14 and NL16. The F2 population showed a wide and continuous range of resistance levels from completely resistant to completely susceptible. By comparison of disease tests, we observed a quantitative resistance against both Bremia races as well as a race-specific resistance to Bremia race NL16 and not to NL14. QTL mapping revealed a qualitative gene (R39) involved in the race-specific resistance and three QTLs (RBQ1, RBQ2 and RBQ3) involved in the quantitative resistance. The qualitative gene R39 is a dominant gene that gives nearly complete resistance to race NL16 in L. saligna CGN 5271 and therefore it showed features similar to Dm genes. The three QTLs explained 51% of the quantitative resistance against NL14, which indicated that probably only the major QTLs have been detected in this F2 population. The perspectives for breeding for durable resistance are discussed
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