Identification of environmentally stable QTL for resistance against Leptosphaeria maculans in oilseed rape (Brassica napus)

© The Author(s) 2015. This article is published with open access at Springerlink.com. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.Phoma stem canker, caused by Leptosphaeria maculans, is a disease of world-wide importance on oilseed rape (Brassica napus). Quantitative trait locus (QTL) mediated resistance against L. maculans in B. napus is considered to be race non-specific and potentially durable. Identification and evaluation of QTL for resistance to L. maculans is important for breeding oilseed rape cultivars with durable resistance. An oilseed rape mapping population was used to detect QTL for resistance against L. maculans in five winter oilseed rape field experiments under different environments. A total of 17 QTL involved in ‘field’ quantitative resistance against L. maculans were detected and collectively explained 51% of the phenotypic variation. The number of QTL detected in each experiment ranged from two to nine and individual QTL explained 2 to 25% of the phenotypic variation. QTL × environment interaction analysis suggested that six of these QTL were less sensitive to environmental factors, so they were considered to be stable QTL. Markers linked to these stable QTL will be valuable for selection to breed for effective resistance against L. maculans in different environments, which will contribute to sustainable management of the disease.Peer reviewe

Hypoxia response in Arabidopsis roots infected by Plasmodiophora brassicae supports the development of clubroot

BackgroundThe induction of alcohol fermentation in roots is a plant adaptive response to flooding stress and oxygen deprivation. Available transcriptomic data suggest that fermentation-related genes are also frequently induced in roots infected with gall forming pathogens, but the biological significance of this induction is unclear. In this study, we addressed the role of hypoxia responses in Arabidopsis roots during infection by the clubroot agent Plasmodiophora brassicae.ResultsThe hypoxia-related gene markers PYRUVATE DECARBOXYLASE 1 (PDC1), PYRUVATE DECARBOXYLASE 2 (PDC2) and ALCOHOL DEHYDROGENASE 1 (ADH1) were induced during secondary infection by two isolates of P. brassicae, eH and e2. PDC2 was highly induced as soon as 7 days post inoculation (dpi), i.e., before the development of gall symptoms, and GUS staining revealed that ADH1 induction was localised in infected cortical cells of root galls at 21 dpi. Clubroot symptoms were significantly milder in the pdc1 and pdc2 mutants compared with Col-0, but a null T-DNA insertional mutation of ADH1 did not affect clubroot susceptibility. The Arg/N-end rule pathway of ubiquitin-mediated proteolysis controls oxygen sensing in plants. Mutants of components of this pathway, ate1 ate2 and prt6, that both exhibit constitutive hypoxia responses, showed enhanced clubroot symptoms. In contrast, gall development was reduced in quintuple and sextuple mutants where the activity of all oxygen-sensing Group VII Ethylene Response Factor transcription factors (ERFVIIs) is absent (erfVII and prt6 erfVII).ConclusionsOur data demonstrate that the induction of PDC1 and PDC2 during the secondary infection of roots by P. brassicae contributes positively to clubroot development, and that this is controlled by oxygen-sensing through ERFVIIs. The absence of any major role of ADH1 in symptom development may also suggest that PDC activity could contribute to the formation of galls through the activation of a PDH bypass

Analyse intégrative de l interaction Arabidopsis thaliana Plasmodiaophora brassicae (vers l élucidation des mécanismes associés à la résistance partielle)

La hernie des crucifères, provoquée par le biotrophe Plasmodiophora brassicae, est une maladie majeure des Brassica cultivées. L association des méthodes culturales aux résistances génétiques est le seul moyen efficace de contrôler la maladie. Cependant, le succès des stratégies d introduction et la gestion raisonnée des résistances dans un objectif de durabilité nécessitent la compréhension de la fonction et des mécanismes associés aux différents facteurs de résistance. L espèce modèle Arabidopsis thaliana, également hôte de P. brassicae, présente une variabilité naturelle de réponse à la hernie des Crucifères. L objectif de ma thèse est de déterminer quels sont les facteurs génétiques de résistance et les voies métaboliques associées à la résistance partielle en se basant sur le modèle A. thaliana P. brassicae. La résistance partielle portée par l accession Bur-0 a été caractérisée à partir de deux populations en ségrégation (F2/3 et lignées recombinantes) issues de croisements entre Bur-0 et l accession sensible Col-0. Cette résistance partielle, de nature quantitative, est sous le contrôle d au moins quatre QTL additifs et quatre QTL épistatiques. Afin d identifier les voies métaboliques associées à la résistance partielle portée par l accession Bur-0, des analyses différentielles du transcriptome ont été réalisées, à l aide de la puce CATMA. La réponse de résistance partielle se caractérise principalement par l induction des voies de défense, la mise en place de mécanismes prévenant l expansino cellulaire et limitant le détournement du métabolisme carboné de l hôte par l agent pathogène.Clubroot, caused by the obligate biotroph Plasmodiophora brassicae, is one of the economically most important diseases of Brassica crops in the world. The development of resistant cultivars is currently the most efficient way to control clubroot in all Brassica crops. However, successful strategies for breeding and management of durable host-plant resistances require knowledge of clubfoot resistance gene fonctions and associated mechanisms. The model plant resistances require knowledge of clubroot resistance gene functions and associated mechanisms. The model plant Arabidopsis thaliana is also a host for clubroot and shows natural variation in the responses to clubroot. The present work aims to determine the genetic factors and metabolic pathwasys associated with partial resistance, using the A. thaliana P. brassicae pathosystem. A quantitative trait locus approach was carried out using two segregating potpulations (F2/3 and recombinant inbred lines) from crosses between the partially resistant accession Bur-0 and the susceptible one Col-0. Four additive QTLs and four epistatic regions controlling partial resistance to clubroot were identified. A functional genomic approach, using the CATMA whole genoe microarray, was then applied to measure changes in gene expression associated with partial quantitative resistance. We showed that partial clubroot resistance response was characterizd by an induction of classical plant defense responses, an active inhibition of cell enlargement and proliferation and a reduced metabolic diversion by the pathogen. In particular, this work highlighted the involvement of arginine metabolism in partial clubroot resistance.RENNES-Agrocampus-CRD (352382323) / SudocSudocFranceF

Vegetal biotechnologies and durable management of resistances versus biotic and abiotic stress: progress and challenges

Vegetal biotechnologies and durable management of resistances versus biotic and abiotic stress: progress and challenge

Une feuille de route pour la valorisation de l’immunité végétale en agriculture

International audienc

Hernie sur colza : la résistance variétale peut enfin être évaluée

National audienceLa résistance variétale du colza est un des meilleurs outils de protection contre la hernie des crucifères. Mais les moyens manquaient pour caractériser cette résistance et la présence de la maladie. Cela a changé

Identification of differentially expressed genes related to aberrant phenotypes in Brassica oleracea var. botrytis

The aberrant phenotype is characterized by the progressive expression of abnormal traits during vegetative growth affecting leaf thickness, shape and/or plant vigour. These striking morphological abnormalities do not appear to be caused by agronomical practices or pathogen infections. Furthermore, the aberrant phenotype, which is observed in 3-20% of cultivated cauliflowers, is not linked to DNA sequence or structural polymorphisms. To detect candidate genes related to the aberrant phenotype, we used amplified fragment length polymorphism on cDNA approach, sampling normal and aberrant F(1) hybrid plants several times before and after the expression of the aberrant phenotype. This screen led to the detection of 51 differentially expressed transcripts. Twenty-nine of these were homologous to annotated genes in genomic databases. We identified transcripts, which were differentially expressed before the expression of the aberrant trait with homology to genes involved in various abiotic stress responses. A non-specific lipid transfer protein homologue was also identified and given the role that these proteins play in epicuticular wax formation and leaf morphology, it may be implicated in the abnormal leaf shape phenotypes

Identification of quantitative trait loci controlling partial clubroot resistance in new mapping populations of Arabidopsis thaliana

To date, mechanisms of partial quantitative resistance, under polygenic control, remain poorly understood, studies of the molecular basis of disease resistance have mainly focused on qualitative variation under oligogenic control. However, oligogenic conferred resistance is rapidly overcome by the pathogen and knowledge of the relationship between qualitative and quantitative resistance is necessary to develop durably resistant cultivars. In this study, we exploited the Arabidopsis thaliana-Plasmodiophora brassicae pathosystem to decipher the genetic architecture determining partial resistance. This soil-borne pathogen causes clubroot, one of the economically most important diseases of Brassica crops in the world. A quantitative trait locus (QTL) approach was carried out using two segregating populations (F(2) and recombinant inbred lines) from crosses between the partially resistant accession Burren and the susceptible accession Columbia. Four additive QTLs (one moderate and three minor) controlling partial resistance to clubroot were identified, all the resistance alleles being derived from the partially resistant parent. In addition, four epistatic regions, which have no additive effect on resistance, were also found to be involved in partial resistance. An examination of candidate genes suggested that a potentially diverse array of mechanisms is related to the different QTLs. By fine-mapping and cloning these regions, the mechanisms involved in partial resistance will be identified

Evolution and variability of the cyst nematode virulence factor Gp-Rbp1 in South American populations of Globodera pallida".

Evolution and variability of the cyst nematode virulence factor Gp-Rbp1 in South American populations of Globodera pallida".Evolution and variability of the cyst nematode virulence factor Gp-Rbp1 in South American populations of Globodera pallida"