In Normandy, flax is a plant of important economic interest because of its fibres. Fusarium oxysporum, a telluric fungus, is responsible for the major losses in crop yield and fibre quality. Several ...methods are currently used to limit the use of phytochemicals on crops. One of them is the use of plant growth promoting rhizobacteria (PGPR) occurring naturally in the rhizosphere. PGPR are known to act as local antagonists to soil‐borne pathogens and to enhance plant resistance by eliciting the induced systemic resistance (ISR). In this study, we first investigated the cell wall modifications occurring in roots and stems after inoculation with the fungus in two flax varieties. First, we showed that both varieties displayed different cell wall organization and that rapid modifications occurred in roots and stems after inoculation. Then, we demonstrated the efficiency of a Bacillus subtilis strain to limit Fusarium wilt on both varieties with a better efficiency for one of them. Finally, thermo‐gravimetry was used to highlight that B. subtilis induced modifications of the stem properties, supporting a reinforcement of the cell walls. Our findings suggest that the efficiency and the mode of action of the PGPR B. subtilis is likely to be flax variety dependent.
Bacillus subtilis strain ATCC 6633 is able to limit the wilt symptoms caused by the pathogenic fungus Fusarium oxysporum f. sp. lini on two Linum usitatissimum (flax) varieties, Aramis and Mélina and to induce modifications of the cell wall composition and stem thermal stability properties, suggesting a cell wall reinforcement.
Powdery mildew is one of the most important diseases of flax and is particularly prejudicial to its yield and oil or fiber quality. This disease, caused by the obligate biotrophic ascomycete
Oïdium ...lini
, is progressing in France. Genetic resistance of varieties is critical for the control of this disease, but very few resistance genes have been identified so far. It is therefore necessary to identify new resistance genes to powdery mildew suitable to the local context of pathogenicity. For this purpose, we studied a worldwide diversity panel composed of 311 flax genotypes both phenotyped for resistance to powdery mildew resistance over 2 years of field trials in France and resequenced. Sequence reads were mapped on the CDC Bethune reference genome revealing 1,693,910 high-quality SNPs, further used for both population structure analysis and genome-wide association studies (GWASs). A number of four major genetic groups were identified, separating oil flax accessions from America or Europe and those from Asia or Middle-East and fiber flax accessions originating from Eastern Europe and those from Western Europe. A number of eight QTLs were detected at the false discovery rate threshold of 5%, located on chromosomes 1, 2, 4, 13, and 14. Taking advantage of the moderate linkage disequilibrium present in the flax panel, and using the available genome annotation, we identified potential candidate genes. Our study shows the existence of new resistance alleles against powdery mildew in our diversity panel, of high interest for flax breeding program.
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•Potential for composites of 10 flax varieties was studied in 2 years with 3 techniques.•Significant differences between the two years could be shown for pultruded composites.•Flax ...varieties with reproducible above/below average properties could be identified.
The use of natural fibres such as flax in composite materials is an expanding market sector. Variability potentially exists at many points in the “plant-composite continuum”. In this study, the influence of i) variety, ii) growth year, and iii) processing technique on the mechanical properties of composites was tested. Ten varieties of flax grown in two consecutive years were processed by the following techniques: i) twin-screw extrusion and injection moulding, ii) vacuum assisted resin transfer moulding (VARTM) and iii) pultrusion. These processes differed in the fibre length, fibre orientation and polymer used, and so differed overall in the severity of the fibre treatments.
The two repetitions of growing in two subsequent years showed a significant influence on the morphology of the raw fibre bundles and the composite properties processed with VARTM and pultrusion technique. The year effect was overlapped by the severe processing influence using twin-screw extrusion and injection moulding, where no influence of the growing year was detectable in the mechanical properties of the composites and the morphology of the fibre bundles extracted from the composites.
Although the use of different processes on the same plant material causes large differences in the mechanical properties of the composites, we could identify plant varieties that showed consistently above average and below average performance with all processing techniques and over two years. This knowledge can be used as a basis for further breeding of flax varieties optimised for composite reinforcement.
•Two compounds are able to trigger several defense responses in flax.•They induce ROS production, callose deposition and several defense-related genes.•They do not impair plant growth and do not have ...antifungal activities.•They improve flax resistance against the pathogenic fungus Fusarium oxysporum.
Plants are surrounded by a diverse range of microorganisms that causes serious crop losses and requires the use of pesticides. Flax is a major crop in Normandy used for its fibres and is regularly challenged by the pathogenic fungus Fusarium oxysporum (Fo) f. sp. lini. To protect themselves, plants use “innate immunity” as a first line of defense level against pathogens. Activation of plant defense with elicitors could be an alternative for crop plant protection. A previous work was conducted by screening a chemical library and led to the identification of compounds able to activate defense responses in Arabidopsis thaliana. Four compounds were tested for their abilities to improve resistance of two flax varieties against Fo. Two of them, one natural (holaphyllamine or HPA) and one synthetic (M4), neither affected flax nor Fo growth. HPA and M4 induced oxidative burst and callose deposition. Furthermore, HPA and M4 caused changes in the expression patterns of defense-related genes coding a glucanase and a chitinase-like. Finally, plants pre-treated with HPA or M4 exhibited a significant decrease in the disease symptoms. Together, these findings demonstrate that HPA and M4 are able to activate defense responses in flax and improve its resistance against Fo infection.
Flax (Linum usitatissimum L.) is an economically important fiber and oil crop that has been grown for thousands of years. The genome has been recently sequenced and transcriptomics are providing ...information on candidate genes potentially related to agronomically-important traits. In order to accelerate functional characterization of these genes we have generated a flax EMS mutant population that can be used as a TILLinG (Targeting Induced Local Lesions in Genomes) platform for forward and reverse genetics.
A population of 4,894 M2 mutant seed families was generated using 3 different EMS concentrations (0.3%, 0.6% and 0.75%) and used to produce M2 plants for subsequent phenotyping and DNA extraction. 10,839 viable M2 plants (4,033 families) were obtained and 1,552 families (38.5%) showed a visual developmental phenotype (stem size and diameter, plant architecture, flower-related). The majority of these families showed more than one phenotype. Mutant phenotype data are organised in a database and can be accessed and searched at UTILLdb (http://urgv.evry.inra.fr/UTILLdb). Preliminary screens were also performed for atypical fiber and seed phenotypes. Genomic DNA was extracted from 3,515 M2 families and eight-fold pooled for subsequent mutant detection by ENDO1 nuclease mis-match cleavage. In order to validate the collection for reverse genetics, DNA pools were screened for two genes coding enzymes of the lignin biosynthesis pathway: Coumarate-3-Hydroxylase (C3H) and Cinnamyl Alcohol Dehydrogenase (CAD). We identified 79 and 76 mutations in the C3H and CAD genes, respectively. The average mutation rate was calculated as 1/41 Kb giving rise to approximately 9,000 mutations per genome. Thirty-five out of the 52 flax cad mutant families containing missense or codon stop mutations showed the typical orange-brown xylem phenotype observed in CAD down-regulated/mutant plants in other species.
We have developed a flax mutant population that can be used as an efficient forward and reverse genetics tool. The collection has an extremely high mutation rate that enables the detection of large numbers of independant mutant families by screening a comparatively low number of M2 families. The population will prove to be a valuable resource for both fundamental research and the identification of agronomically-important genes for crop improvement in flax.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Multitemporal satellite synthetic aperture radar (SAR) images are a useful source of information for geophysicists to monitor changing regions. In this paper, a new approach is proposed to extract ...from multitemporal SAR images two kinds of information: temporal changes (flooded areas, coastline erosion, etc.) and stable spatial features (roads, rivers, etc.). The novelty of the proposed approach is to detect simultaneously these two kinds of discontinuities. In a first step, the contrast and the heterogeneity information is extracted by a "multitemporal" application of the ratio of local means and by new three-dimensional texture parameters based on the log-cumulants. In a second step, the resulting attributes that measure the time variability or the presence of spatial features are merged. An interactive fuzzy fusion approach is proposed to provide end-users with a simple and easily understandable tool for tuning the change-detection results. The performances of the proposed attributes and fusion technique are presented on a set of seven multitemporal SAR images acquired by the European Remote Sensing (ERS-1) satellite.
Abstract In Normandy, flax is a plant of important economic interest because of its fibres. Fusarium oxysporum , a telluric fungus, is responsible for the major losses in crop yield and fibre ...quality. Several methods are currently used to limit the use of phytochemicals on crops. One of them is the use of plant growth promoting rhizobacteria (PGPR) occurring naturally in the rhizosphere. PGPR are known to act as local antagonists to soil‐borne pathogens and to enhance plant resistance by eliciting the induced systemic resistance (ISR). In this study, we first investigated the cell wall modifications occurring in roots and stems after inoculation with the fungus in two flax varieties. First, we showed that both varieties displayed different cell wall organization and that rapid modifications occurred in roots and stems after inoculation. Then, we demonstrated the efficiency of a Bacillus subtilis strain to limit Fusarium wilt on both varieties with a better efficiency for one of them. Finally, thermo‐gravimetry was used to highlight that B. subtilis induced modifications of the stem properties, supporting a reinforcement of the cell walls. Our findings suggest that the efficiency and the mode of action of the PGPR B. subtilis is likely to be flax variety dependent.
L’objectif de la thèse est d’améliorer les différents traitements et de proposer une visualisation claire et intuitive à l’opérateur des données en sortie d’un géoradar (radargramme) afin de pouvoir ...localiser de manière précise les réseaux de canalisations enfouis. Notamment, nous souhaitons mettre en évidence les hyperboles présentes dans les radargrammes car celles-ci sont caractéristiques de la présence d'une canalisation. Dans un premier temps nous nous sommes intéressés à la suppression de l’information inutile (clutter) pouvant gêner la détection des hyperboles. Nous avons ainsi proposé une méthode de filtrage du clutter et du bruit des radargrammes. Ensuite, nous avons travaillé sur l’élaboration d’une méthode permettant de détecter automatiquement les hyperboles dans un radargramme ainsi qu’une estimation de sa fonction mathématique dans des conditions quasi-temps réel. Et enfin nous avons également proposé une méthode de séparation de source permettant de distinguer le clutter et le signal utile du radargramme tout en ayant un impact minimal sur les hyperboles. Ces derniers travaux ouvrent d’autres possibilités pour le filtrage, le rehaussement ou la détection automatique d’hyperboles.
The thesis objective is to improve the different processing in order to make the data acquired by ground penetrating radar (B-scan) more understandable for the operators. Consequently, it will facilitate the pipe localisation. More particularly, we wish to highlight the hyperbolas in the B-scan because they point out the presence of a pipe. First of all, we are interested in removing all the useless information which might hide the hyperbolas. We proposed a filtering method removing unwanted reflections and noise. Then, we worked on an automatic hyperbola detection method and an estimation of their mathematical functions in quasi real time. Finally, we proposed a source separation method to distinguish the unwanted reflections from the hyperbolas with a minimal impact on them. This last work opens interesting perspectives in filtering, hyperbolas enhancement and hyperbola detection.
This paper presents an almost unsupervised fusion algorithm on linear features (LF) extraction in synthetic aperture radar (SAR) interferometric data, in particular for mangroves/shorelines and thin ...internal channels. The spatial information on LFs is first extracted in the coherence image, where they are wider and more visible: water regions (in particular thin internal channels) are dark areas (low coherence) due to the temporal decorrelation of backscattering signals in these and surrounding regions, whereas conventional vegetation regions are brighter areas (high coherence). These approximate locations of LFs are further refined by using the edge map coming from a semantic fuzzy fusion of the coefficient of variation (CV) and the ratio of local means (RLM) measured in the amplitude image. The final detection of LFs is then performed by merging the two fuzzy inputs: the spatial information and the edge location map. The membership degree statistics of CV and RLM semantic fusion measures are introduced in order to illustrate the location detection ability. The originality of this method in comparison with conventional approaches is in the fusion scheme that follows the interpreter behavior by using first the coherence image for a fuzzy detection where thin LFs are more visible, but have low location accuracy, and then the amplitude image where they are poorly visible, but with higher location accuracy, to obtain improved results. A quantitative performance evaluation is also presented. The method has been applied on real interferometric SAR images from European Remote Sensing satellites over the western part of Cameroon.
La mixité et le refus de l'hybridité Adveille, Marie-Hélène; DIAZ, Elvire; Finding, Susan (Trouvé) ...
Cahiers du MIMMOC,
11/2007
4-2007
Journal Article, Publication
Odprti dostop
Le thème de l’identité est au centre des contributions à ce numéro des Cahiers. Parmi les questionnements divers au sujet de l’identité, celui de l’identité plurielle, de la mixité et de l’hybridité ...a probablement été le plus posé ces dernières années, au vue des développements sociaux et politiques récents. C’est pourquoi les auteurs ont trouvé opportun de contribuer aux débats en analysant et en comparant les concepts de mixité et d’hybridité dans leurs différentes acceptations en France, au Royaume-Uni, en Ireland et en Espagne. Les contributions qui suivent sont des cas d’étude de l’acceptation des termes de mixité et d’hybridité principalement dans des pays anglophone mais aussi en France. Ils concernent essentiellement le monde contemporain et les dernières décennies. Ils font une large part au thème de l’ethnicité, mais également à d’autres formes de mixité et d’hybridité. Les articles de ce cahier sont le fruit des réflexions pendant deux journées d’études et de séminaires du Mimmoc (Equipe d’Accueil 3812). La première journée d’études, « Mixité », s’est tenue à l’Université de Poitiers le 29 avril 2005 avec le soutien du CRECIB (Centre de Recherches et d’Études de la Civilisation britannique). La deuxième journée à l’Université de Toulouse 2 Le Mirail, le 13 octobre 2006, sur « Le refus de l’hybridité culturelle » fut organisée par des chercheurs de TIDE (UMR 6588 CNRS). The theme of Identity is at the heart of the contributions to this issue of the Cahiers. Among the issues raised on the subject of identity, those pertaining to plural identity, diversity and hybridity, are probably the ones that have been most raised in recent years, in view of recent political and social developments. That is the reason why the authors felt that a contribution to the debate by comparing the concepts of diversity and hybridity in their varying acceptions in France, the United Kingdom, Ireland and Spain. The following contributions are case studies which mainly concern English-speaking countries and France. They look at the contemporary European world. Ethnicity is largely represented here as a theme, but other forms of diveristy and hybridity are also present. The present articles stem from two day conferences and seminars organised by the MIMMOC research team. The first day conference "Diversity" was held at Poitiers on 29th April 2005 with the help of the CRECIB (Centre de Recherches et d’Études de la Civilisation britannique). The second day conference was organised at the University of Toulouse 2 Le Mirail, on 13th October 2006, on the question of "Refusing cultural hybridity" organised by researchers from the TIDE (UMR 6588 CNRS) research team.
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