Alain Borgel

Institute of Research for Development, Marsiglia, Provence-Alpes-Côte d'Azur, France

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Publications (14)15.95 Total impact

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    ABSTRACT: This study presents an analysis of the impact of mycorrhizal inoculation on growth under salt stress of date palms cultivars Nakhla hamra (NHH) and Tijib known in the Sahel for their earliness in flowering and fruiting. The seedlings were grown in a greenhouse on a sandy substrate watered to field capacity every two days and were subjected to increasing levels of NaCl (0 , 1, 2 , 4, 6 , 8 and 16 g.L - 1) and then inoculated with 5 strains of Glomus (G. aggregatum , G. intraradices , G. verriculosum, G. mosseae , G. fasciculatum ). The experimental design was a randomized complete block with three factors (cultivars: Tijib and Nakhla Hamra x seven levels of NaCl concentrations x six levels of inoculum). The results showed that in the absence of NaCl, G. verriculosum significantly enhanced shoot growth: 33.5 cm against 30.3 cm in the control and roots growth: 81.5 cm against 78 cm in NHH, while in Tijib, the growth is stimulated by Glomus fasciculatum: 33.8 cm against 32.7 cm for stems and 90 cm against 86 cm for the roots of inoculated plants and controls. In contrast, in the presence of NaCl 8g.L -1, NHH has a better growth in the presence of G. intraradices: 37.3 cm against 30.6 cm for stems and 77 cm against 73 for roots, while Tijib grows better in the presence of G. fasciculatum with respectively 31.9 cm against 31.7 cm and 51.27 cm against 51.6 cm for stems and roots of inoculated plants and controls. Biochemical analyzes revealed that changes in levels of proline depend on the cultivar, the mycorrhizal strain used and concentrations of NaCl applied. These results open the prospect of using mycorrhizal fungi to improve the productivity of palm trees in the Sahel.
    Advances in Bioscience and Biotechnology 01/2014; 4:64-72.
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    ABSTRACT: This study provides a physiological analysis of somatic embryogenesis in four elite cultivars of date palms: Ahmar, Amsekhsi, Tijib, and Amaside, from the initial callogenesis to establishment and proliferation of embryogenic suspension cultures. Somatic embryos development and in vitro plants rooting were also studied. For each step, auxins and cytokinins concentrations were optimised. The primary callogenesis from leaf explants of seedlings appeared highly dependent on genotype. Ahmar (80%) and Amsekhsi (76%) appeared highly callogenic, whereas Tijib (10%) and Amaside (2%) produced low amounts of calluses. 2,4-Dichlorophenoxyacetic acid appeared favorable to the induction of primary callogenesis and its effect was enhanced by the addition of benzyl adenine or adenine sulfate. Secondary friable calli obtained from chopped granular calli were used to initiate embryogenic cell suspensions in media supplied with 2,4-dichlorophenoxyacetic acid. Suspension cultures showed a growth rate of fourfold after four subcultures in presence of 2,4-dichlorophenoxyacetic acid 2 mg/L. Our results showed that a seven-day transitory treatment with benzyl adenine 0,5 mg/L was necessary to optimize embryos development. Naphthalene acetic acid induced the development of primary orthogravitropic roots during embryos germination. The comparison with cytofluorometry of nuclear DNA amounts showed no significant difference in ploidy level between regenerated plants and seedlings.
    The Scientific World Journal 01/2012; 2012:837395. · 1.73 Impact Factor
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    ABSTRACT: Nine species (wild and cultivated) and some interspecific (wild × cultivated) hybrids were analysed by flow cytometry. This study confirms various polyploidy levels within cultivated species. DNA index varied by a factor of 1 to 3 for Dioscorea alata, 1 to 2.25 for Dioscorea bulbifera, and 1 to 2 for Dioscorea cayenensis-rotundata, depending on the clone or cultivar considered. In wild species, only one DNA index per species was obtained. Whenever a relationship between DNA index and chromosome number could be established, the size of genome 1C was evaluated in picograms and base pairs. Two genome sizes were observed: genome A in D. cayenensis-rotundata, Dioscorea abyssinica, Dioscorea mangenotiana, and Dioscorea praehensilis and genome B in Dioscorea togoensis. These genomes were small sizes, only 1.5 to 2.1 times larger than that of Arabidopsis. Key words: yams, Dioscorea, flow cytometry, DNA index, genome size.
    Canadian Journal of Botany 02/2011; 70(5):996-1000. · 1.40 Impact Factor
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    ABSTRACT: While callogenesis in date palm can be initiated by culturing immature leaf segments on medium containing 2,4-dichlorophenoxyacetic acid (2,4-D), it is difficult to obtain callus from certain genotypes. To better understand the mechanisms of callogenesis in date palm, we studied the developmental events underlying this process at the cellular level. The callogenic capacity of leaf segments depends on the state of cell differentiation. The most callogenic segments were within the leaf elongation zone, required polar auxin transport to initiate callogenesis and contained the highest quantities of free endogenous indole-3-acetic acid. At the cellular level, callus induction involves two spatially and temporally separated events. The first event involves cells from the fascicular parenchyma in an equatorial plane perpendicular to the vascular axis that within 2 days of culture in the presence of 2,4-D, acquire structural and ultrastructural features typically observed in meristematic cells. The second event occurs 3 days later and is characterised by the modification of adjacent perivascular sheath cells. The latter cells become callogenic in that they reinitiated their cell cycles and undergo cell division leading to callus formation. These data provide evidence that callus initiation in leaf vascular tissue of date palm involves a sequential response of two distinct cell types to auxin and requires polar auxin transport.
    Plant Cell Tissue and Organ Culture 01/2009; · 2.61 Impact Factor
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    ABSTRACT: The date palm is a dioecious perennial species of the Arecaceae for which in vitro micropropagation is essential to ensure the renewal of palm plantations. This study presents a histocytological analysis of the traditional Mauritanian Amsekhsi cultivar beginning from the initial callogenesis and continuing up to the establishment of the cellular embryogenic cell suspensions. The formation of somatic embryos and their development into rooted plants are also described. Foliar segments of seedlings cultured in the presence of 2,4-D produced primary calli that were chopped to produce fine friable granular calli that subsequently produced cellular suspensions when transferred to liquid medium. The somatic proembryos that developed after removal of the 2,4-D were plated on agar medium where they developed into rooted plants. Thin sections of tissue fragments taken at each stage of the process were stained using Periodic Acid Schiff and Naphthol Blue-Black. The first cellular divisions were localized close to the vascular vessels of the leaf. The primary calli were obtained within 2 months. Fine friable granular calli grew quickly after the primary calli were chopped. Individual embryogenic cells were identified that rapidly started to divide and developed into globular proembryos. In addition, in the microcalli, breaking zones appeared in the thick pectocellulosic walls which delimited the pluricellular proembryos. The anatomy of somatic embryos is similar to that of zygotic embryos despite a deficit in the accumulation of intracellular proteins. When rooted with NAA, the vitroplants developed a strong orthotropic taproot. This study contributes to understanding the whole process of somatic embryogenesis, but two specific questions remain to be answered: what factors are involved in the reactivation of the somatic cells at the beginning of the initial callogenesis, and why do the somatic embryos not accumulate proteins in their tissues during maturation?
    Annals of Botany 09/2006; 98(2):301-8. · 3.45 Impact Factor
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    ABSTRACT: osmotic stress induced by polyethylene glycol (PEG) or NaCl during the early stages of plant development. Two varieties Nakhla hamra (NHH) and Tijib widely cultivated in Mauritania were tested. NHH showed increasing of epicotyl length, primary root length, secondary root number and proline content when water deficit was induced by PEG. In contrast, on the basis of the same developmental and biochemical characters, the Tijib cultivar was more tolerant in salinity stress. This difference of cultivars’ behavior according the growth conditions is discussed.
    AFRICAN JOURNAL OF BIOTECHNOLOGY 09/2005; 4(9):968-972. · 0.57 Impact Factor
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    ABSTRACT: This is the first report of a systematic study of genes expressed by means of expressed sequence tag (EST) analysis in oil palm, a species of the Arecales order, a phylogenetically key clade of monocotyledons that is not widely represented in the sequence databases. Five different cDNA libraries were generated from male and female inflorescences, shoot apices and zygotic embryos and unidirectional systematic sequencing was performed. A total of 2411 valid EST sequences were thus obtained. Cluster analysis enabled the identification of 209 groups of related sequences and 1874 singletons. Putative functions were assigned to 1252 of the set of 2083 non-redundant ESTs obtained. The EST database described here is a first step towards gene discovery and cDNA array-based expression analysis in oil palm.
    FEBS Letters 06/2005; 579(12):2709-14. · 3.58 Impact Factor
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    ABSTRACT: La multiplication végétative in vitro de plusieurs sous-espèces d'acacias sahéleins (#Acacia tortilis$ ssp. #raddiana$, #A. nilotica$ ssp. #adstringens$ et ssp. #tomentosa$) a été étudiée sous différents aspects : le microbouturage et, en particulier, le maintien de la rhizogenèse après plusieurs subcultures ; l'embryogenèse somatique à partir de plusieurs types d'explants ; la détection de variants sur la quantité d'ADN nucléaire parmi les régénérants de l'embryogenèse somatique. Deux protocoles sont proposés, le premier permet d'obtenir un enracinement normal, c'est-à-dire formé de pivots à partir de microboutures d'#A. tortilis$ ssp. #raddiana$ après plusieurs subcultures, l'autre permet de produire régulièrement des embryons somatiques de clones différents des espèces #A. tortilis$ ssp. #raddiana$, #A. nilotica$ ssp. #adstringens$ et ssp. #tomentosa$. La nature de l'auxine (acide indole butyrique, AIB, ou acide naphtalène acétique, ANA) utilisée pour induire la rhizogenèse des microboutures a une influence significative non seulement sur la fréquence de l'enracinement mais aussi sur la morphologie du système racinaire qui se met en place. La quantité d'ADN nucléaire des régénérants de l'embryogenèse somatique a été mesurée par cytométrie en flux. Dans plusieurs cas, des différences significatives par rapport aux témoins issus de graines ont été observées. Le passage par une phase de dédifférenciation peut provoquer un doublement de la quantité d'ADN par noyaux sur les jeunes embryons et les cals embryogènes. (Résumé d'auteur)
    01/1998;
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    ABSTRACT: In date palm (Phoenix dactylifera L. cv. Ahmar, Arecaceae), as for many monocotyledons, callogenesis is a prerequisite for the initiation of somatic embryogenesis, and requires the presence of auxin in the medium. Immature leaf explants were cultivated in medium supplemented with either 1 or 54μM 1-naphtaleneacetic acid in order to induce either rhizogenesis or callogenesis. Histological studies performed throughout the culture period established that precocious cell reactivation is similar in both morphogenetic pathways. Early cytological modifications are associated with cell reactivation and are observed in the pluripotent cells of perivascular sheaths. Divergence between the callogenesis and rhizogenesis pathways is observed later, during the subsequent determination and morphological differentiation phases. We established that in date palm, the rhizogenesis and callogenesis pathways are initiated from the same cell type, the ultimate developmental fate depending upon auxin concentration.
    Plant Cell Tissue and Organ Culture 98(1):47-58. · 2.61 Impact Factor
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    ABSTRACT: #Acacia tortilis$ ssp. #raddiana$ est l'unique représentant de l'espèce en Afrique de l'Ouest. Utilisé pour des besoins domestiques, cet arbre fourrager est essentiel au maintien du pastoralisme dans le Sahel. Au Sénégal, l'étude de sa diversité génétique a porté sur cinq systèmes enzymatiques (six locus et 20 allèles) et une quinzaine de sites répartis dans la région sahélienne du pays. Les zymogrammes obtenus montrent un grand nombre d'allèles et des différences d'intensité de bandes caractéristiques d'une hérédité tétrasomique des espèces tétraploïdes. Comme chez de nombreuses espèces arborées, la diversité intra-site est élevée avec une différenciation inter-site faible. Toutefois, le niveau de diversité est nuancé en fonction des conditions écologiques locales. Il est d'autant plus élevé que le peuplement se trouve à proximité d'un point d'eau accueillant les troupeaux pendant la saison sèche. Les résultats sont discutés en fonction de la polyploïdie de l'espèce, de la pression humaine et animalière, et du mode de dispersion des graines. La région de Podor semble, de par sa richesse allélique, être une priorité pour la conservation de la variabilité de cette espèce. (Résumé d'auteur)
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    M.H. Chevallier, Alain Borgel
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    ABSTRACT: Le genre #Acacia$ comprend environ 1 250 espèces dont la majorité est originaire d'Australie et seulement 134 d'Afrique. Certaines sont vitales pour l'économie locale des régions sahéliennes. L'étude de la variabilité génétique des populations naturelles est un préalable indispensable pour définir les stratégies de gestion des ressources génétiques. Une revue comparative des travaux sur l'organisation de la diversité génétique des arbres forestiers, des acacias et de quelques acacias africains est présentée. Les différents types de marqueurs ainsi que leurs méthodes d'analyse sont décrits. Malgré la disparité des mesures, une comparaison des niveaux de diversité des espèces est discutée en intégrant plusieurs échelles géographiques ou caractéristiques biologiques. La diversité génétique des arbres est la plus grande dans le monde végétal. L'aire de répartition et le système de reproduciton en sont les facteurs principaux. En revanche, la différenciation est faible entre les populations. Le genre #Acacia$ présente une structuration très hétérogène de la diversité. Par comparaison avec les acacias africains, les espèces australiennes sont les moins variables au niveau intra-population mais présentent une plus grande différenciation entre les populations qui correspondent à des régions géographiques bien séparées. L'allofécondation, qui est la règle générale, connaît quelques exceptions en particulier chez des espèces africaines qui supportent un fort taux d'autofécondation. Les différents niveaux de ploïdie et de quantité d'ADN nucléaire peuvent aussi expliquer le maintien de la diversité génétique et aident à la classification. Des résultats expérimentaux sur des marqueurs isoenzymatiques sont présentés sur les acacias africains. Ils mettent en évidence les relations taxonomiques dans deux complexes d'espèces agrégés autour de marqueurs communs et/ou de niveaux de ploïdie communs... (D'après résumé d'auteur)