264 research outputs found
Efficacy of oral afoxolaner plus milbemycin oxime chewable (NexGard Spectra®, Merial) to prevent heartworm disease in dogs after inoculation with third stage larvae of Dirofilaria immitis
No full textThe novel combination of afoxolaner plus milbemycin oxime, NexGard Spectra®, was evaluated
against the migrating Dirofilaria immitis larvae in beagle dogs in two negative control, blinded
laboratory studies.
In each study, dogs were randomly allocated to an untreated control and a treated group of 10
dogs each. In each study, dogs were inoculated with third stage D. immitis larvae by
subcutaneous injection (50 larvae in the first, 100 larvae in the second study). The larvae had
grown into L3 stage in mosquitoes fed on blood obtained in the field from naturally infected dogs
in Italy (Lombardy for the first, Sardinia for the second study). Thirty-one days after inoculation,
each dog in the treated group was orally treated with NexGard Spectra® dosed as close as
possible to the minimum effective dose (2.5 mg/kg Afoxolaner + 0.5 mg/kg milbemycin oxime).
The control group remained untreated. All dogs were humanely euthanized and examined for
adult D. immitis 146 or 147 days after inoculation. In the first study, seven of the ten untreated
dogs were infected, harboring 1 to 5 adult D. immitis. In the second study, the ten untreated
dogs were positive and harbored 22 to 46 adult D. immitis. In both studies all treated dogs
remained free of heartworm infection as no D. immitis was recovered, demonstrating that the
novel combination of afoxolaner plus milbemycin oxime was 100% effective in preventing
heartworm disease in dogs
Dans un contexte de changement climatique, quels sont les impacts de la sécheresse sur la vigne et sur le devenir des vignobles ? L'exemple du Languedoc
No full textBranch Development Controls Leaf Area Dynamics in Grapevine (Vitis vinifera) Growing in Drying Soil
No full textCorrespondance: [email protected] audienceBackground and Aims Soil water deficit is a major abiotic stress with severe consequences for the development, productivity and quality of crops. However, it is considered a positive factor in grapevine management (Vitis vinifera), as it has been shown to increase grape quality. The effects of soil water deficit on organogenesis, morphogenesis and gas exchange in the shoot were investigated. Methods Shoot organogenesis was analysed by distinguishing between the various steps in the development of the main axis and branches. Several experiments were carried out in pots, placed in a greenhouse or outside, in southern France. Soil water deficits of various intensities were imposed during vegetative development of the shoots of two cultivars ('Syrah' and 'Grenache N'). Key Results All developmental processes were inhibited by soil water deficit, in an intensity-dependent manner, and sensitivity to water stress was process-dependent. Quantitative relationships with soil water were established for all processes. No difference was observed between the two cultivars for any criterion. The number of leaves on branches was particularly sensitive to soil water deficit, which rapidly and strongly reduced the rate of leaf appearance on developing branches. This response was not related to carbon availability, photosynthetic activity or the soluble sugar content of young expanding leaves. The potential number of branches was not a limiting factor for shoot development. Conclusions The particularly high sensitivity to soil water deficit of leaf appearance on branches indicates that this process is a major determinant of the adaptation of plant leaf area to soil water deficit. The origin of this particular developmental response to soil water deficit is unclear, but it seems to be related to constitutive characteristics of branches rather than to competition for assimilates between axes differing in sink strengt
Lebron-colon, mar Isabel B.S. University of Puerto Rico- humacao campus, 1998, 2005
No full textAn improved procedure for the purification of single wall carbon nanotubes produced by the HiPCO process has been developed. This improved procedure has the advantage of allowing successful purification of gram quantities of HiPCO SWNTs, in contrast to the literature procedure that report the purifications of less than 100 mg batches. Large amounts of purified carbon nanotubes are essential for their further use in the preparation of novel materials and components. Another advantage of this improved procedure is that it substantially reduced the amount of synthesis impurities, catalyst, and non-nanotube forms of carbon within the carbon nanotubes resulting in significant increases in their stability. A design of experiment (DOE) based optimization was utilized in the development of this improved purification method. A method was developed to produce stable suspensions of purified HiPCO SWNTs in DMF/NMP using ultra-sonication. The chemical reactivity of the purified HiPCO SWNTs in the presence of benzyne generated in situ by different approaches was studied. Functionalization of the SWNTs was successful when benzyne was generated in low concentration in situ from benzyene precursors. Thermal and spectroscopic analysis of the functionalized nanotubes confirm that Diels-Alder addition of benzyne to nanotubes had occurred. The extent of functionalization of the surface of the nanotubes was determined to range from 9 to 16 % based upon TGA. It was possible to form stable suspensions of the purified nanotubes treated with polycyclic aromatic hydrocarbon derivatives. These complexes nanotubes can be readily dispersed in organic solvents to provide colloidal suspensions that are stable for days at room temperature. It was shown that noncovalent functionalization allows more efficient dispersion of the purified single wall carbon nanotubes throughout a thermoplastic polyimide resulting in a substantially greater enhancement in the tensile strength and conductivity properties of the polymeric film than those realized with the incorporation of purified single carbon nanotubes which had not been functionalized
Abscisic acid down-regulates hydraulic conductance of grapevine leaves in isohydric genotypes only
No full textPublished September 12, 2017.Plants evolved different strategies to cope with water stress. While isohydric species maintain their midday leaf water potential (ΨM) under soil water deficit by closing their stomata, anisohydric species maintain higher stomatal aperture and exhibit substantial reductions in ΨM. It was hypothesized that isohydry is related to a locally higher sensitivity of stomata to the drought-hormone abscisic acid (ABA). Interestingly, recent lines of evidence in Arabidopsis suggested that stomatal responsiveness is also controlled by an ABA action on leaf water supply upstream from stomata. Here, we tested the possibility in grapevine that different genotypes ranging from near isohydric to more anisohydric may have different sensitivities in these ABA responses. Measurements on whole plants in drought conditions were combined with assays on detached leaves fed with ABA. Two different methods consistently showed that leaf hydraulic conductance (Kleaf) was downregulated by exogenous ABA, with strong variations depending on the genotype. Importantly, variation between isohydry and anisohydry correlated with Kleaf sensitivity to ABA, with Kleaf in the most anisohydric genotypes being unresponsive to the hormone. We propose that observed response of Kleaf to ABA may be part of the overall ABA regulation of leaf water status.Aude Coupel-Ledru, Stephen D. Tyerman, Diane Masclef, Eric Lebon, Angélique Christophe, Everard J. Edwards, and Thierry Simonnea
A leaf gas exchange model that accounts for intra‐canopy variability by considering leaf nitrogen content and local acclimation to radiation in grapevine (Vitis vinifera L.)
No full textUnderstanding the distribution of gas exchange within a plant is a prerequisite for scaling up from leaves to canopies. We evaluated whether leaf traits were reliable predictors of the effects of leaf ageing and leaf irradiance on leaf photosynthetic capacity (Vcmax, Jmax) in field‐grown vines (Vitis vinifera L). Simultaneously, we measured gas exchange, leaf mass per area (LMA) and nitrogen content (Nm) of leaves at different positions within the canopy and at different phenological stages. Daily mean leaf irradiance cumulated over 10 d (PPFD10) was obtained by 3D modelling of the canopy structure. Nm decreased over the season in parallel to leaf ageing while LMA was mainly affected by leaf position. PPFD10 explained 66, 28 and 73% of the variation of LMA, Nm and nitrogen content per area (Na), respectively. Nitrogen content per unit area (Na=LMA×Nm) was the best predictor of the intra‐canopy variability of leaf photosynthetic capacity. Finally, we developed a classical photosynthesis‐stomatal conductance submodel and by introducing Na as an input, the model accurately simulated the daily pattern of gas exchange for leaves at different positions in the canopy and at different phenological stages during the season.EEA MendozaFil: Prieto, Jorge Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina. Institut National de la Recherche Agronomique; FranciaFil: Louarn, Gaëtan. Institut National de la Recherche Agronomique; FranciaFil: Perez Peña, Jorge Esteban. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; ArgentinaFil: Ojeda, Hernan. Institut National de la Recherche Agronomique. Unité expérimentale de Pech Rouge; FranciaFil: Simonneau, Thierry. Institut National de la Recherche Agronomique; FranciaFil: Lebon, Eric. Institut National de la Recherche Agronomique. Unité Mixte de Recherche; Franci
Physiological and genetic determinisms of water-use in grapevine
No full textLa raréfaction des ressources en eau associée au changement climatique menace particulièrement la durabilité de la viticulture en climat Méditerranéen. Pour y faire face, la création ou le choix de cépages économes en eau et suffisamment vigoureux en cas de déficit hydrique se présente comme un levier important. Une compréhension approfondie des mécanismes qui gouvernent le maintien de l'état hydrique par la plante est indispensable pour avancer dans cette direction. Dans ce travail les déterminants génétiques et physiologiques de l'utilisation de l'eau ont été explorés chez la vigne. Une descendance F1, issue d'un croisement entre les cépages Syrah et Grenache, a été soumise à deux scénarios hydriques dans des pots (bonne irrigation et déficit modéré) en combinant de nouveaux outils de phénotypage, une démarche de génétique quantitative (pour la détection de QTLs) et des approches physiologiques. L'analyse de l'architecture génétique du maintien du potentiel hydrique par la plante, plus ou moins efficace en cas de déficit hydrique (i.e. iso- ou aniso-hydrique), a révélé un double déterminisme, impliquant non seulement la régulation stomatique de la transpiration mais également le maintien de la conductance hydraulique à travers la plante. Nous avons démontré l'existence d'une action indirecte de l'acide abscissique sur la fermeture stomatique à travers une diminution de la conductance hydraulique dans la feuille avec une variabilité génétique reliée aux comportements iso- ou aniso-hydriques. Par ailleurs, nous avons mis en évidence une variabilité génétique importante de la transpiration nocturne, liée à celle de l'efficience d'utilisation de l'eau, avec des déterminants génétiques et physiologiques que nous avons identifiés. Au-delà de l'utilité des QTLs détectés pour l'amélioration variétale, les résultats originaux de ce travail démontrent l'intérêt de la génétique quantitative pour progresser dans la compréhension de mécanismes physiologiques.In Mediterranean regions, water scarcity associated with climate change particularly threatens the sustainability of viticulture. Breeding grapevine for reduced water use and maintained production is therefore of major interest. This requires a comprehensive knowledge of the plant physiological responses to drought. In this study we focused on the determinism of transpiration rate as a key trait regulating water status in plant tissues, and on its relationship with water-use efficiency (WUE). We used a F1 progeny from a cross between cultivars Syrah and Grenache and combined powerful phenotyping tools on potted plants submitted to either well-watered or mild deficit conditions with quantitative genetics (for QTL detection) and physiological experiments. Analysis of the genetic control of water status maintenance in the plant, more or less efficient under soil water deficit (i.e. iso- or anisohydric), revealed a dual physiological determinism with a key role for plant hydraulic conductance beside that of stomatal control of transpiration. An indirect role of abscisic acid on stomatal conductance was also evidenced, mediated by the downregulation of leaf hydraulic conductance, with a genetic variability which correlated with genetic variation in iso- or aniso-hydric behaviour. We then revealed wide genetic variations in nocturnal transpiration, which correlated with variations in water use efficiency, and identified corresponding genetic and physiological determinants. In a final switch to the field, we showed consistency between QTLs detected for daytime WUE in pots and in the vineyard. Beyond the potential interest of the QTLs detected in this study for breeding prospects, this work demonstrated the benefits of quantitative genetics to shed light on ecophysiological and physiological processes
Soutenance d'HDR d'Annick Rivens Mompean
No full textmardi 27 novembre 2012, 14h30, Université du Havre, 25 rue Lebon, salle de soutenance du PRSH « Apprentissage des langues en autonomie dans un dispositif institutionnel avec le numérique : approche par la complexité » Composition du jury M. Jean-Claude Bertin (directeur), Professeur à l'Université du Havre Mme Sophie Bailly, Professeure à l'Université de Nancy M. Eric Bruillard, Professeur à l'ENS Cachan M. David Little, Professeur à Trinity College (Dublin) Mme Claire Tardieu, Professeure à..
Relationships between plant and soil water status in vine (Vitis vinigera L.)
No full textSoil water status and its effect on plant water status are commonly evaluated for water stress diagnosis in annual crops. We investigated the application of this method to vineyards, using the fraction of transpirable soil water (FTSW) to characterise the soil water deficit experienced by the plant. The stability of the relationship between FTSW and predawn leaf water potential ([psi]p) was analysed over two years (2000-2001), in two contrasted soils in vineyards in south eastern France, both planted with the cultivar Syrah, but grafted on different rootstocks (SO4 and 140Ru). FTSW was determined from soil moisture measurements performed with a neutron probe down to 2.5 m, under the rows and between the rows (3 replicates in each case). Vertical and horizontal variations in soil water content were analysed and the upper and lower limits of total vine's transpirable soil water (TTSW) were calculated for each soil. The lower limit was also compared with the value of soil moisture content determined at -1.5 MPa in the laboratory. FTSW could be calculated for the soil depth analysed, without distinguishing horizontal position (row or inter-row). The lower limit of TTSW for vine was higher than the soil water content at -1.5 MPa, except in the upper horizons (0-0.2 m) which are prone to soil evaporation. A single relationship between [psi]p and FTSW was obtained for the two vineyards and for the two years of measurement. This relationship was similar to that established by Lebon et al. (2003) on Gewürztraminer/SO4 in a vineyard in northern France. FTSW can therefore be used as an indicator of the water deficit experienced in vineyards, provided that TTSW is correctly estimated
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