5 research outputs found

    Rapid and sensitive methods for detection of Allorhizobium vitis, causal agent of grapevine crown gall

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    A rapid method and sensitive methods for extraction of bacterial DNA from pure culture and directly from plant materiel were compared in polymerase chain reaction with specific primers VCF3/VCR3 to see the reliable method that can used in the detection of tumorigenic strain of Allorhizobium vitis causal agent of grapevine crown gall. From the three tested methods of DNA extraction from pure culture, the alkaline method is the most effective technique for the extraction presenting a high sensitivity with a detection threshold equal to 5.104 CFU/ml. Five different protocols for extracting bacterial DNA from plant tissues of infected tomato, based on the use of an extraction buffer, were tested to see its usefulness in detecting pathogenic strain of A. vitisS4. Two protocols based on the use of Triton X-100 and Tween 20 were efficient for detecting A. vitis S4 directly from tomato tumors with a sensitivity of 103 CFU/ml for the both protocols. Consequently, these protocols were proposed as specific protocols for the detection of tumorigenic strain of A. vitis from symptomatic and asymptomatic plants

    La composition chimique et l’activité antibactérienne des huiles essentielles de quatre plantes aromatiques et médicinales marocaines contre Allorhizobium vitis

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    This study aims to investigate the chemical composition and inhibitory effects of four essential oils from Moroccan medicinal and aromatic plants: Rosmarinus officinalis L., Satureja calamintha L., Lavandula stoechas L. and Citrus aurantium L. on Allorhizobium vitis strain S4 causal agent of crown gall of grapevine. The identification of compounds was performed by GC-MS analysis. Furthermore, the antibacterial activity of each essential oil was evaluated using aromatogram test. Results showed that the major compounds are cineole (48.12%) and α-Pinene (13.48%) for R. officinalis, borneol (29.01%) and 1,8-Cineole (18.18%) for S. calamintha, linalool (25.76%) and camphor (21.09%) for L. stoechas, linalool (38.81 %) and limonene (37.93 %) for C. aurantium essential oil. All essential oils tested exhibit an antibacterial activity in vitro against A. vitis S4 with a percentage of inhibition and minimal inhibitory concentration values in the range of 7.5-25.88% and 0.15-20.00 mg/ml, respectively.Cette étude vise à étudier la composition chimique et l’activité antibactérienne des essentielles de quatre plantes aromatiques et médicinales marocaines : Rosmarinus officinalis L., Satureja calamintha L., Lavandula stoechas L. et Citrus aurantium L. sur l’agent causal de la galle du collet de la vigne Allorhizobium vitis la souche S4. L'identification des composés a été réalisée par la chromatographie en phase gazeuse couplée à la spectrométrie de masse (CG-SM). L'activité antibactérienne de chaque huile essentielle a été évaluée à l'aide d'un test d'aromatogramme. Les résultats ont montré que les principaux composés sont le cinéole (46,28%) et le camphre (12,32%) pour R. officinalis, le bornéol (23,89%) et le cinéole (18,18%) pour S. calamintha, le linalol (25,76%) et le camphre (21,09%) pour L. stoechas, limonène (34,56%) et oxyde de linalol (34,24%) pour l'huile essentielle de C. aurantium. Toutes les huiles essentielles testées présentent une activité antibactérienne in vitro contre A. vitis S4 avec un pourcentage d'inhibition (PI) et une concentration minimale inhibitrice (CMI) varient entre 7,5-25,88% et 0,15-20,00 mg/ml, respectivement

    Evaluation de la variabilité spatiotemporelle dans un verger d’olivier à travers des images multispectrales prises par un drone

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    Precision Agriculture (PA) is a management strategy based on Information and Communication Technologies (ICT) used to assist management decisions with the aim to increase productivity, to reduce labor time and inputs needed, to improve benefits and to protect the environment. Techniques related to PA were initially used to monitor status of annual crops and they were recently adopted on fruit trees. Nevertheless, PA is still in its initiation phase in Morocco. Given the importance of olive in the national and international levels, applying this concept in the intensive and hyper-intensive production systems would be a reliable and cost-effective approach for the assessment of orchards health and nutritional status and then make reliable decisions. With the aim to assess the potential of multi-spectral images to inform on temporal and spatial variability characterizing an olive orchard, this study was carried out in an orchard of 22 ha, in Meknes region, Morocco, planted principally with “Picholine marocaine” variety. Four Unmanned Aerial Vehicle (UAV) flights, from June to November 2020, were performed and three vegetation indices (VIs) were computed: NDVI, GNDVI and NDRE. Spatial variability was assessed using variogram, a geostatistical tool, and temporal variability was evaluated using Spearman rank correlation and relative difference methods. The three VIs showed a weak temporal and spatial stability of trees which indicate an overall unstable canopy condition related to tree physiological behavior and environmental conditions (temperature and rainfall). Additionally, the observation of a potential stress was recorded firstly by NDRE, followed by NDVI and GNDVI. Results show promising perspectives of using remote sensing techniques to assess olive trees status and therefore support farmers in orchards management. Such challenge requires more in-depth work to develop in house models correlating VIs to agronomical parameters.L’agriculture de précision (AP) est un concept, basé sur les technologies de l’information et de communication (TIC), qui conjugue à la fois des objectifs agronomiques (amélioration du rendement et de la qualité des produits), économiques (minimisation des coûts de production) et environnementaux (meilleure utilisation des intrants). Les techniques relevant de l’AP ont été utilisées au premier abord sur les grandes cultures, mais ont été vite adoptées en arboriculture fruitière. Au Maroc, le recours à ce nouveau concept reste limité et encore moins au niveau de l’olivier. Etant donné l’importance de cette culture, tant à l’échelle nationale qu’internationale, le recours à l’AP comme moyen d’aide à la décision pour une gestion raisonnée et efficiente des vergers d’olivier; conduits en intensif et semi intensif; présente une approche prometteuse pour l’oléiculture marocaine. Le présent travail consiste à étudier le potentiel des images multispectrales pour déceler la variabilité spatiotemporelle pouvant caractériser un verger d’olivier. L’étude a été menée dans une oliveraie de 22 ha dans la région de Meknès, plantée par la variété « Picholine marocaine ». A partir des images multispectrales, prises sur 4 survols de drone (de juin à novembre), trois indices de végétation (IV) : NDVI, GNDVI et NDRE ont été dérivés. La variabilité spatiale a été évaluée à l'aide du variogramme, un outil géostatistique, alors que la variabilité temporelle a été évaluée à l'aide des méthodes de corrélation de Spearman Rank et des différences relatives. Les trois IVs ont montré une faible stabilité temporelle et spatiale au niveau du verger; une instabilité liée au comportement physiologique des arbres (la canopée particulièrement) et aux conditions environnementales (température et précipitations). En plus, la présence d’un stress potentiel a été enregistrée d'abord par le NDRE, puis par le NDVI et le GNDVI. Les résultats montrent des perspectives prometteuses d'utilisation des images multispectrales dans le cas des oliviers et invitent à un travail plus approfondi pour développer des modèles corrélant les IVs aux paramètres agronomiques qu’il serait utile de suivre

    Characterization and phylogenetic diversity of Allorhizobium vitis isolated from grapevine in Morocco

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    AIMS: Crown gall, a phytobacteriosis characterized by the formation of tumours on plant roots was observed in recently planted vineyards of the Meknes region (Morocco). The objective of this research was to analyze the diversity of pathogenic agrobacteria isolated from grapevine in Morocco. METHODS AND RESULTS: Eighty-two isolates from 11 affected vineyards were characterized by recA sequencing and were found to belong to A. tumefaciens genomospecies G1, G4 or G7, Rhizobium rhizogenes, and to Allorhizobium vitis. Only the A. vitis isolates appeared to be pathogenic on tomato and MLSA phylogenetic analyses revealed a weak genetic diversity, with the definition of only four genomic groups. Definition of the A. vitis genomic groups correlateds with specific pathogenic traits: indeed, genomic groups differed with respect to the severity of hypersensitive response symptoms on tobacco leaves, the intensity of necrotic response on grapevine explants, and opine profiles. Both vitopine and octopine were detected by UHPLC in tumors induced by isolates of three genomic groups, an opine signature scarcely ever reported. CONCLUSIONS: Allorhizobium vitis is the only causative agent of crown gall on grape in Morocco, pathogenic isolates can be separated into four genomic groups. SIGNIFICANCE AND IMPACT OF THE STUDY: This study of recently crown-gall-infested vineyards demonstrated that Allorhizobium vitis is the only causative agent and revealed the presence of non-pathogenic Agrobacterium strain within tumors. Moreover, as the genetic diversity of the A. vitis isolates is relatively narrow, this study lays the basis for further analyses on the evolution of the disease, on the dissemination of the pTi and more globally on the fate of the different genomic groups in this newly colonized environment
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