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Accueil du site → Doctorat → Royaume-Uni → 1995 → Studies on somatic embryogenesis and development of DNA markers in date palm (Phoenix dactylifera L.)

University of London (1995)

Studies on somatic embryogenesis and development of DNA markers in date palm (Phoenix dactylifera L.)

Aitchitt, Mustapha

Titre : Studies on somatic embryogenesis and development of DNA markers in date palm (Phoenix dactylifera L.)

Auteur : Aitchitt, Mustapha.

Université de soutenance : University of London

Grade : Doctor of Philosophy (Ph.D.) : 1995

Résumé
This thesis presents results of studies on the development of an efficient date palm micropropagation procedure and DNA-based genetic markers. Earlier studies used high concentrations of auxins (2,4-D) for callus induction and maintenance which could jeopardise the genetic stability of culture derived date palms. Therefore, a series of experiments was carried Out to study the effects of three phenoxyacetic acid auxins, picloram, dicamba, and 2,4,5-T in comparison with 2,4-D on callogenesis and somatic embryogenesis. The results showed that relatively low concentrations of picloram can be substituted for 2,4-D to induce embryogenic calli. Date palm somatic embryos obtained using this procedure could be advanced to all stages of development leading finally to vigorous microplants. Well-developed secondary root systems were obtained with IBA treatments. The conditions for acclimatisation of such plantlets ex vitro were standardised by monitoring three key factors : root and stem structure prior to weaning, and the growth substrate used. A suitable in vitro plantlet structure for weaning in terms of roots and stem types was identified and growth environments also assessed by means of which over 90% of plantlets survived ex vitro. RFLP and RAPD approaches were used to identify and establish strategies for developing DNA-based markers with which to assess genetic variability in date palm. For this, initially, a procedure was developed for the extraction of total DNA from mature leaves. Pst I and EcoR I restriction fragments of date palm DNA were cloned using the plasmid vector pUC19. The cloned fragments were grouped into low, medium and high copy sequences and six of these were partially sequenced. The cloned DNAs were used as probes to detect restriction fragment polymorphisms in a set of date palm accessions in the Zagora germplasm collection of the Institut National de la Recherche Agronomique (INRA), Morocco. The PCR conditions for RAPD analysis of date palm DNA were optimised. A series of 10- mer random primers and date palm DNA based 20-mers were screened for their ability to generate RAPD polymorphisms. Sufficient polymorphisms were detected to enable genetic diversity studies to be performed on selected accessions. Some suggestions about the suitability of RFLP or RAPD-based DNA markers for date palm are presented and discussed. The significance of somatic embryogenesis micropropagation methods and genetic fingerprinting are discussed in the context of date palm improvement in general and more specifically with respect to the INRA date palm breeding programme in Morocco.

Mots clés : Oasis ecosystem Botany Agronomy Plant diseases Horticulture Botany Agronomy

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