Oil palm biotechnology: progress and prospects

Today, a range of biotechnological approaches, from somatic embryogenesis to biomolecular research, play an increasingly important role in breeding strategies for oil palm (Elaeis guineensis Jacq.). Clonal micropropagation. Methods of cloning by in vitro culture led to the development of a micropropagation technique for oil palm based on somatic embryogenesis which was tested at the pilot stage on elite genotypes, thus enabling the production of high oil yielding clones. This phase allowed the identification of limiting factors associated with scaling-up, with respect in particular to the scale of mass production required to meet the needs of planters and to the problem of ensuring genetic fidelity in the regenerated plant material. These two concerns led researchers to look further into the underlying physiological and/or molecular mechanisms involved in somatic embryogenesis and the somaclonal variation events induced by the in vitro cloning procedure. Structural and functional genomics. Marker-assisted breeding in oil palm is a long-term multi-stage project including: molecular analysis of genetic diversity in both E. guineensis and E. oleifera germplasms; large scale development of PCR-based microsatellite markers; and parallel development of three genome mapping and QTL detection projects studying key agronomic characters. Post-genomics. In order to tackle the problem of the mantled flowering abnormality, which is induced during the micropropagation process, studies of gene expression have been carried out in tissue cultures as a means of establishing an early clonal conformity testing procedure. It is important to assess what kind of methodology is the most appropriate for clonal conformity testing by comparing RNA, protein and DNA (PCR) based approaches. Parallel studies on genomic DNA methylation changes induced by tissue culture suggest that the latter may play an important role in the determination of the mantled abnormality. (Résumé d'auteur

Influence of Growth Regulators on Callogenesis and Somatic Embryo Development in Date Palm (Phoenix dactylifera L.) Sahelian Cultivars

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

L'intégration de l'ethnobotanique et de la génétique des populations met en évidence l'agrobiodiversité des palmiers dattiers de l'oasis de Siwa (Égypte) et leur importance pour l'histoire évolutive de l'espèce.

Crop diversity is shaped by biological and social processes interacting at different spatiotemporal scales. Here we combined population genetics and ethnobotany to investigate date palm (Phoenix dactylifera L.) diversity in Siwa Oasis, Egypt. Based on interviews with farmers and observation of practices in the field, we collected 149 date palms from Siwa Oasis and 27 uncultivated date palms from abandoned oases in the surrounding desert. Using genotyping data from 18 nuclear and plastid microsatellite loci, we confirmed that some named types each constitute a clonal line, i.e. a true-to-type cultivar. We also found that others are collections of clonal lines, i.e. ethnovarieties, or even unrelated samples, i.e. local categories. This alters current assessments of agrobiodiversity, which are visibly underestimated, and uncovers the impact of low-intensity, but highly effective, farming practices on biodiversity. These hardly observable practices, hypothesized by ethnographic survey and confirmed by genetic analysis, are enabled by the way Isiwans conceive and classify living beings in their oasis, which do not quite match the way biologists do: a classic disparity of etic vs. emic categorizations. In addition, we established that Siwa date palms represent a unique and highly diverse genetic cluster, rather than a subset of North African and Middle Eastern palm diversity. As previously shown, North African date palms display evidence of introgression by the wild relative Phoenix theophrasti, and we found that the uncultivated date palms from the abandoned oases share even more alleles with this species than cultivated palms in this region. The study of Siwa date palms could hence be a key to the understanding of date palm diversification in North Africa. Integration of ethnography and population genetics promoted the understanding of the interplay between diversity management in the oasis (short-time scale), and the origins and dynamic of diversity through domestication and diversification (long-time scale)

Abstracts

In order to better understand the developmental processes that govern the formation of somatic embryos in oil palm (Elaeis guineensis Jacq.), we investigated the transcription factor genes expressed during embryogenesis in this species. The AP2/EREBP transcription factor family includes the AP2 subgroup, which contains several proteins that play important roles in plant development. We identified and characterized EgAP2-1, which codes for a protein that contains two AP2 domains similar to those of the transcription factor BABYBOOM (BBM) and more generally AINTEGUMENTA-like (AIL) proteins of the AP2 subgroup. In a similar way to related genes from eudicots, ectopic expression of EgAP2-1 in transgenic Arabidopsis plants alters leaf morphology and enhances regeneration capacity. In oil palm, EgAP2-1 transcripts accumulate to the greatest extent in zygotic embryos. This expression pattern was investigated in more detail by in-situ hybridization, revealing that in both zygotic and somatic embryos, EgAP2-1 expression is concentrated in proliferating tissues associated with the early development of leaf primordia, root initials and provascular tissues. (Résumé d'auteur

Biotechnologies du palmier dattier

Le palmier dattier est une plante d'intérêt écologique, économique et social majeur pour de nombreux pays des zones arides qui comptent parmi les plus pauvres du globe. En effet, en créant au milieu du désert un microclimat favorable au développement de cultures sous-jacentes, le palmier dattier constitue l'axe principal de l'agriculture dans les régions désertiques et représente la principale ressource vivrière et financière des populations oasiennes. Pour traiter les problématiques liées à la culture du palmier au Maghreb, en Afrique et en Europe du Sud, 60 chercheurs font ici un bilan de leurs recherches sur l'évaluation, la conservation et la valorisation des ressources génétiques du palmier dattier, ouvrant ainsi de nouvelles perspectives pluridisciplinaires. L'ouvrage présente les dernières avancées scientifiques sur la production à grande échelle, les variations somaclonales et l'amélioration génétique. Enfin, il pose les bases de nouveaux projets internationaux sur la conservation des ressources génétiques du palmier dattier, un enjeu important pour développer l'agriculture oasienne

Sexer pour développer le dattier

Il existe très peu de programmes d'amélioration génétique du palmier-dattier. Pourtant, les besoins en plants résistants aux maladies ou aux stress abiotiques, essentiels à la sauvegarde et au développement des palmeraies, sont importants