Frederic Chiroleu | CIRAD - Academia.edu (original) (raw)
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Papers by Frederic Chiroleu
Frontiers in Plant Science, 2015
Root and stem rot (RSR) disease caused by Fusarium oxysporum f. sp. radicis-vanillae (Forv) is th... more Root and stem rot (RSR) disease caused by Fusarium oxysporum f. sp. radicis-vanillae (Forv) is the most damaging disease of vanilla (Vanilla planifolia and V. × tahitensis, Orchidaceae). Breeding programs aimed at developing resistant vanilla varieties are hampered by the scarcity of sources of resistance to RSR and insufficient knowledge about the histopathology of Forv. In this work we have (i) identified new genetic resources resistant to RSR including V. planifolia inbreds and vanilla relatives, (ii) thoroughly described the colonization pattern of Forv into selected vanilla accessions, confirming its necrotic non-vascular behavior in roots, and (iii) evidenced the key role played by hypodermis, and particularly lignin deposition onto hypodermal cell walls, for resistance to Forv in two highly resistant vanilla accessions. Two hundred and fifty-four vanilla accessions were evaluated in the field under natural conditions of infection and in controlled conditions using in vitro plants root-dip inoculated by the highly pathogenic isolate Fo072. For the 26 accessions evaluated in both conditions, a high correlation was observed between field evaluation and in vitro assay. The root infection process and plant response of one susceptible and two resistant accessions challenged with Fo072 were studied using wide field and multiphoton microscopy. In susceptible V. planifolia, hyphae penetrated directly into the rhizodermis in the hairy root region then invaded the cortex through the passage cells where it induced plasmolysis, but never reached the vascular region. In the case of the resistant accessions, the penetration was stopped at the hypodermal layer. Anatomical and histochemical observations coupled with spectral analysis of the hypodermis suggested the role of lignin deposition in the resistance to Forv. The thickness of lignin constitutively deposited onto outer cell walls of hypodermis was highly correlated with the level of resistance for 21 accessions tested. The accumulation of p-coumaric and sinapic acids, two phenolic precursors of lignin, was observed in the resistant plants inoculated with Fo072, but not in the susceptible one. Altogether, our analyses enlightened the mechanisms at work in RSR resistant genotypes and should enhance the development of novel breeding strategies aimed at improving the genetic control of RSR of vanilla.
Scientific Reports, 2015
Of worldwide economic importance, Tomato yellow leaf curl virus (TYLCV, Begomovirus) is responsib... more Of worldwide economic importance, Tomato yellow leaf curl virus (TYLCV, Begomovirus) is responsible for one of the most devastating plant diseases in warm and temperate regions. The DNA begomoviruses (Geminiviridae) are transmitted by the whitefly species complex Bemisia tabaci. Although geminiviruses have long been described as circulative non-propagative viruses, observations such as long persistence of TYLCV in B. tabaci raised the question of their possible replication in the vector. We monitored two major TYLCV strains, Mild (Mld) and Israel (IL), in the invasive B. tabaci Middle East-Asia Minor 1 cryptic species, during and after the viral acquisition, within two timeframes (0-144 hours or 0-20 days). TYLCV DNA was quantified using real-time PCR, and the complementary DNA strand of TYLCV involved in viral replication was specifically quantified using anchored real-time PCR. The DNA of both TYLCV strains accumulated exponentially during acquisition but remained stable after viral acquisition had stopped. Neither replication nor vertical transmission were observed. In conclusion, our quantification of the viral loads and complementary strands of both Mld and IL strains of TYLCV in B. tabaci point to an efficient accumulation and preservation mechanism, rather than to a dynamic equilibrium between replication and degradation.
ABSTRACT Pour prédire l'évolution de la maladie en tenant compte de l'hétérogénéi... more ABSTRACT Pour prédire l'évolution de la maladie en tenant compte de l'hétérogénéité géographique de l'île de la Réunion, nous avons développé un nouveau modèle nommé L SEIR. Par rapport aux modèles épidémiologiques classiques, son pouvoir de prédiction est plus grand grâce à l'introduction d'un stade larvaire et plus spécifique grâce à son application micro géographique, au niveau de la commune. (Résumé d'auteur)
ABSTRACT The status of knowledge on the entomofauna of La Réunion appears quite variable dependin... more ABSTRACT The status of knowledge on the entomofauna of La Réunion appears quite variable depending on the insect order considered. While Coleoptera and Lepidoptera have received sustained attention, it is only recently that some other groups such as Odonata, Dictyoptera, Thysanoptera or Hemiptera Auchenorrhyncha have been extensively studied. Other important orders such as Diptera and Hymenoptera appear to be far less known and will require extensive studies in the future. Within the on going process of the creation of a National Park in the highlands of La Réunion, a series of studies was initiated by the "Mission Parc National des Hauts de la Réunion", aiming at synthetising the current knowledge on various groups of plant and animals. CIRAD was in charge of the work on entomofauna. In collaboration with the Natural History Museum, the Insectarium of La Réunion and some individual specialists, an attempt was made to synthetize the current status of knowledge on the different insect orders based on existing literature records. The attention was focused on four groups (Odonata, Hemiptera Auchenorrhyncha, Coleoptera, Lepidoptera) selected on the base of their knowledge status or their possible interest as bio-indicators. All endemic taxa from La Réunion or from the Mascarenes were listed and their known geographical distribution precised. The corresponding database was used with GIS to draw maps of areas showing a particular interest for the conservation of these endemic taxa. Further studies should be conducted to extend to database to all orders of insects and other group of arthropods. (Texte intégral)
Conservation biological control implies an appropriate management of arthropod communities at sev... more Conservation biological control implies an appropriate management of arthropod communities at several trophic levels. Plant addition in agroecosystems has effects on upper trophic levels by providing basal resources and new habitats. The abundance and species richness of phytophagous and predatory arthropods may therefore be modified with a potential impact on pest control. Landscape characteristics and pesticide applications are also well known to influence the different trophic levels of the agroecosystems. However, simultaneous influences of these factors on different trophic levels are still poorly reported. In mango orchards in Reunion, we tested the hypothesis that species richness (SR) of two trophic levels (primary and secondary consumers), are determined by frequency of insecticides application (FIA), addition of cover plants and landscape features. To this end, we used mixed linear models on data on arthropods from extensive sampling (34738 individuals of 469 species in 20...
Phytopathology, 2015
For the development of pathogen-informed breeding strategies, identifying the microbial genes inv... more For the development of pathogen-informed breeding strategies, identifying the microbial genes involved in interactions with the plant is a critical step. To identify Type III effector (T3E) repertoires associated to virulence of the bacterial wilt (BW) pathogen Ralstonia solanacearum on Solanaceous crops, we used an original association genetics approach combining DNA microarray data and pathogenicity data on resistant eggplant, pepper and tomato accessions. From this first screen, twenty-five Type III effectors were further full-length PCR-amplified within a 35-strain field collection, to assess their distribution and allelic diversity. Six T3E repertoire groups were identified, within which 11 representative strains were chosen to challenge the BW-resistant eggplants "Dingras multiple Purple" and "AG91-25", and the tomato Hawaii 7996. The virulence or avirulence phenotypes could not be explained by specific T3E repertoires, but rather by individual T3E genes. We identified seven highly avirulence-associated genes, among which ripP2, primarily referenced as conferring avirulence to Arabidopsis thaliana. Interestingly, no T3E was associated to avirulence to both eggplants. Highly virulence-associated genes were also identified: ripA5_2, ripU, and ripV2. This study should be regarded as a first step towards investigating both avirulence or virulence function of the highlighted genes, but also their evolutionary dynamics in natural R. solanacearum populations.
Background and objectives: Bacterial blight of onion (BBO), a biennial plant species, is an emerg... more Background and objectives: Bacterial blight of onion (BBO), a biennial plant species, is an emerging disease now present in many onion-producing areas. The causal agent, Xanthomonas axonopodis pv. allii (Xaa), is seedborne (2). Although the importance of seedborne Xaa as an initial inoculum source associated with the early stages of epidemics has been reported (3), no study concerning the epidemiology of BBO in seed production fields was conducted. In addition, the process of contamination of onion seeds in diseased fields is not understood and has never been measured. Our objectives were to (i) describe the temporal and spatial dynamics of the disease in experimental onion seed production plots, and (ii) evaluate contamination rates of seeds from these plots. Materials and methods: Epidemic progress in experimental plots of 121 x 60 onion plants contaminated onion bulbs (random inoculation was performed on 0.27% of the plants) was monitored. This experiment was done in duplicate ov...
Frontiers in Plant Science, 2015
Root and stem rot (RSR) disease caused by Fusarium oxysporum f. sp. radicis-vanillae (Forv) is th... more Root and stem rot (RSR) disease caused by Fusarium oxysporum f. sp. radicis-vanillae (Forv) is the most damaging disease of vanilla (Vanilla planifolia and V. × tahitensis, Orchidaceae). Breeding programs aimed at developing resistant vanilla varieties are hampered by the scarcity of sources of resistance to RSR and insufficient knowledge about the histopathology of Forv. In this work we have (i) identified new genetic resources resistant to RSR including V. planifolia inbreds and vanilla relatives, (ii) thoroughly described the colonization pattern of Forv into selected vanilla accessions, confirming its necrotic non-vascular behavior in roots, and (iii) evidenced the key role played by hypodermis, and particularly lignin deposition onto hypodermal cell walls, for resistance to Forv in two highly resistant vanilla accessions. Two hundred and fifty-four vanilla accessions were evaluated in the field under natural conditions of infection and in controlled conditions using in vitro plants root-dip inoculated by the highly pathogenic isolate Fo072. For the 26 accessions evaluated in both conditions, a high correlation was observed between field evaluation and in vitro assay. The root infection process and plant response of one susceptible and two resistant accessions challenged with Fo072 were studied using wide field and multiphoton microscopy. In susceptible V. planifolia, hyphae penetrated directly into the rhizodermis in the hairy root region then invaded the cortex through the passage cells where it induced plasmolysis, but never reached the vascular region. In the case of the resistant accessions, the penetration was stopped at the hypodermal layer. Anatomical and histochemical observations coupled with spectral analysis of the hypodermis suggested the role of lignin deposition in the resistance to Forv. The thickness of lignin constitutively deposited onto outer cell walls of hypodermis was highly correlated with the level of resistance for 21 accessions tested. The accumulation of p-coumaric and sinapic acids, two phenolic precursors of lignin, was observed in the resistant plants inoculated with Fo072, but not in the susceptible one. Altogether, our analyses enlightened the mechanisms at work in RSR resistant genotypes and should enhance the development of novel breeding strategies aimed at improving the genetic control of RSR of vanilla.
Scientific Reports, 2015
Of worldwide economic importance, Tomato yellow leaf curl virus (TYLCV, Begomovirus) is responsib... more Of worldwide economic importance, Tomato yellow leaf curl virus (TYLCV, Begomovirus) is responsible for one of the most devastating plant diseases in warm and temperate regions. The DNA begomoviruses (Geminiviridae) are transmitted by the whitefly species complex Bemisia tabaci. Although geminiviruses have long been described as circulative non-propagative viruses, observations such as long persistence of TYLCV in B. tabaci raised the question of their possible replication in the vector. We monitored two major TYLCV strains, Mild (Mld) and Israel (IL), in the invasive B. tabaci Middle East-Asia Minor 1 cryptic species, during and after the viral acquisition, within two timeframes (0-144 hours or 0-20 days). TYLCV DNA was quantified using real-time PCR, and the complementary DNA strand of TYLCV involved in viral replication was specifically quantified using anchored real-time PCR. The DNA of both TYLCV strains accumulated exponentially during acquisition but remained stable after viral acquisition had stopped. Neither replication nor vertical transmission were observed. In conclusion, our quantification of the viral loads and complementary strands of both Mld and IL strains of TYLCV in B. tabaci point to an efficient accumulation and preservation mechanism, rather than to a dynamic equilibrium between replication and degradation.
ABSTRACT Pour prédire l'évolution de la maladie en tenant compte de l'hétérogénéi... more ABSTRACT Pour prédire l'évolution de la maladie en tenant compte de l'hétérogénéité géographique de l'île de la Réunion, nous avons développé un nouveau modèle nommé L SEIR. Par rapport aux modèles épidémiologiques classiques, son pouvoir de prédiction est plus grand grâce à l'introduction d'un stade larvaire et plus spécifique grâce à son application micro géographique, au niveau de la commune. (Résumé d'auteur)
ABSTRACT The status of knowledge on the entomofauna of La Réunion appears quite variable dependin... more ABSTRACT The status of knowledge on the entomofauna of La Réunion appears quite variable depending on the insect order considered. While Coleoptera and Lepidoptera have received sustained attention, it is only recently that some other groups such as Odonata, Dictyoptera, Thysanoptera or Hemiptera Auchenorrhyncha have been extensively studied. Other important orders such as Diptera and Hymenoptera appear to be far less known and will require extensive studies in the future. Within the on going process of the creation of a National Park in the highlands of La Réunion, a series of studies was initiated by the "Mission Parc National des Hauts de la Réunion", aiming at synthetising the current knowledge on various groups of plant and animals. CIRAD was in charge of the work on entomofauna. In collaboration with the Natural History Museum, the Insectarium of La Réunion and some individual specialists, an attempt was made to synthetize the current status of knowledge on the different insect orders based on existing literature records. The attention was focused on four groups (Odonata, Hemiptera Auchenorrhyncha, Coleoptera, Lepidoptera) selected on the base of their knowledge status or their possible interest as bio-indicators. All endemic taxa from La Réunion or from the Mascarenes were listed and their known geographical distribution precised. The corresponding database was used with GIS to draw maps of areas showing a particular interest for the conservation of these endemic taxa. Further studies should be conducted to extend to database to all orders of insects and other group of arthropods. (Texte intégral)
Conservation biological control implies an appropriate management of arthropod communities at sev... more Conservation biological control implies an appropriate management of arthropod communities at several trophic levels. Plant addition in agroecosystems has effects on upper trophic levels by providing basal resources and new habitats. The abundance and species richness of phytophagous and predatory arthropods may therefore be modified with a potential impact on pest control. Landscape characteristics and pesticide applications are also well known to influence the different trophic levels of the agroecosystems. However, simultaneous influences of these factors on different trophic levels are still poorly reported. In mango orchards in Reunion, we tested the hypothesis that species richness (SR) of two trophic levels (primary and secondary consumers), are determined by frequency of insecticides application (FIA), addition of cover plants and landscape features. To this end, we used mixed linear models on data on arthropods from extensive sampling (34738 individuals of 469 species in 20...
Phytopathology, 2015
For the development of pathogen-informed breeding strategies, identifying the microbial genes inv... more For the development of pathogen-informed breeding strategies, identifying the microbial genes involved in interactions with the plant is a critical step. To identify Type III effector (T3E) repertoires associated to virulence of the bacterial wilt (BW) pathogen Ralstonia solanacearum on Solanaceous crops, we used an original association genetics approach combining DNA microarray data and pathogenicity data on resistant eggplant, pepper and tomato accessions. From this first screen, twenty-five Type III effectors were further full-length PCR-amplified within a 35-strain field collection, to assess their distribution and allelic diversity. Six T3E repertoire groups were identified, within which 11 representative strains were chosen to challenge the BW-resistant eggplants "Dingras multiple Purple" and "AG91-25", and the tomato Hawaii 7996. The virulence or avirulence phenotypes could not be explained by specific T3E repertoires, but rather by individual T3E genes. We identified seven highly avirulence-associated genes, among which ripP2, primarily referenced as conferring avirulence to Arabidopsis thaliana. Interestingly, no T3E was associated to avirulence to both eggplants. Highly virulence-associated genes were also identified: ripA5_2, ripU, and ripV2. This study should be regarded as a first step towards investigating both avirulence or virulence function of the highlighted genes, but also their evolutionary dynamics in natural R. solanacearum populations.
Background and objectives: Bacterial blight of onion (BBO), a biennial plant species, is an emerg... more Background and objectives: Bacterial blight of onion (BBO), a biennial plant species, is an emerging disease now present in many onion-producing areas. The causal agent, Xanthomonas axonopodis pv. allii (Xaa), is seedborne (2). Although the importance of seedborne Xaa as an initial inoculum source associated with the early stages of epidemics has been reported (3), no study concerning the epidemiology of BBO in seed production fields was conducted. In addition, the process of contamination of onion seeds in diseased fields is not understood and has never been measured. Our objectives were to (i) describe the temporal and spatial dynamics of the disease in experimental onion seed production plots, and (ii) evaluate contamination rates of seeds from these plots. Materials and methods: Epidemic progress in experimental plots of 121 x 60 onion plants contaminated onion bulbs (random inoculation was performed on 0.27% of the plants) was monitored. This experiment was done in duplicate ov...