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Random amplified polymorphic DNA (RAPD) analysis using arbitrary 10-mer ohgonucleotide primers was employed in order to investigate the genetic fidelity of somatic embryogenesis-derived regenerants of oil palm {Elaeis guineensis Jacq). Clonal palms bearing the 'mantled' phenotype were identified in the field and the ability of RAPD markers to distinguish these variants from palms of the normal type was assessed. Of the 387 arbitrary primers used, 259 (67%) were successfully used to amplify oil palm DNA genomic fragments with consistently reproducible banding. Of these 387 primers, 73 (19%) primers enabled the identification of polymorphism between clones. No intraclonal variability and no differences between mother palms and regenerants could be identified using the total number of markers scored (8900). Twenty-four of these 73 primers were chosen for use in a larger experiment aimed at comparing, first, the mother palm genome with that of its clonal offspring and, second, true-to-type and variant regenerants. Thus, the regeneration protocol based on somatic embryogenesis set up for oil palm clonal propagation does not induce any gross genetic changes. The results obtained revealed however, that the RAPD approach is not suitable for the detection of the 'mantled' variant phenotype. The use of RAPD markers for the detection of somaclonal variation in oil palm is discussed.

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KEY MESSAGE : The long-term proliferation of embryogenic cell suspensions of oil palm is associated with changes in both genomic methylation rates and embryogenic capacities. In the aim of exploring the relationship between epigenetic stability and the long-term in vitro proliferation of plant tissues, we have studied changes in genomic DNA methylation levels in embryogenic suspensions of oil palm (Elaeis guineensis Jacq.). Five embryogenic callus lines were obtained from selected hybrid seeds and then proliferated as suspension cultures. Each clonal line obtained from a single genotype was subdivided into three independent subclonal lines. Once established, cultures proliferated for 12 months and genomic DNA was sampled at 4 months intervals for the estimation of global DNA methylation rates through high performance liquid chromatography (HPLC) quantitation of deoxynucleosides. Our results show that in vitro proliferation induces DNA hypermethylation in a time-dependent fashion. Moreover, this trend is statistically significant in several clonal lines and shared between subclonal lines originating from the same genotype. Interestingly, the only clonal line undergoing loss of genomic methylation in the course of proliferation has been found unable to generate somatic embryos. We discuss the possible implications of genome-wide DNA methylation changes in proliferating cells with a view to the maintenance of genomic and epigenomic stability.

-Breeding the oil palm (Elaeis guineensis Jacq.) for climate change requires multidisciplinary and collaborative research by nature: indeed -besides genetics and structural and functional genomics -almost all disciplines related to life sciences are involved. Research work also relies on the identification of genetic variation in the strategies of response to stress developed by the plant: this implies the exploration of resources provided by natural variation, germplasm collections, selected genitors from breeding programs together with material of interest collected from smallholders. The phenotyping of selected plant material under biotic/abiotic stress will involve new methods for high-throughput phenotyping and genomic approaches will be followed for the identification of genes underlying the variation of traits which will be used as selection targets. Also, improvements in understanding how climate change may influence chemical and physical processes in soils, how this may affect nutrient availability, and how the plant responds to changed availability of nutrients will also influence oil palm breeding programs. Molecular approaches and tools have great potential to optimize patterns of plant breeding, especially for perennial species. In recent years, there has been an exponential increase in molecular resources and methods aimed at identifying polymorphisms which control the traits of interest and exploring the mechanisms linking these polymorphisms to phenotypes. With genomic resources becoming increasingly available for the oil palm (sequencing, resequencing and chips development) the exploration of the genetic basis of complex traits such as oil yield or resistance to disease is now possible. Consequently the availability and sharing of such a large amount of data is currently reshaping most of oil palm breeding strategies.Keywords: adaptability / drought / genomics / phenotyping / plasticity / polymorphism / sex ratio Résumé -Sélection génétique du palmier à l'huile ( Elaeis guineensis Jacq. ) et changement climatique.La sélection génétique du palmier à huile pour faire face au changement climatique exige par nature une recherche pluridisciplinaire et collaborative : en effet, outre la génétique et la génomique structurelle et fonctionnelle, presque toutes les disciplines liées aux sciences de la vie sont impliquées. Ce travail de recherche intégratif nécessite également de pouvoir estimer la variation génétique dans les processus de réponse au stress développés par les plantes : il implique une exploration des ressources offertes par la variation génétique naturelle, les collections de germoplasme, les meilleurs géniteurs issus des programmes de sélection, ainsi que par le matériel d'intérêt recueilli auprès des petits exploitants. Le phénotypage du matériel végétal sélectionné sous stress biotique ou abiotique va impliquer de nouvelles méthodes de phénotypage à haut débit et des approches génomiques devront être suivies pour l'identification des gènes à la source de variations dans des car...

This study was conducted over a period of 20 years, to assess the problems involved in developing subcultures over a very long period, of oil palm (Elaeis guineensis Jacq.) somatic embryos which were maintained in vitro on a Murashige and Skoog mineral-based culture medium, without growth regulators. Analysis of the proliferation rate of the embryogenic cultures, along with the survivability of the regenerated plantlets after their transfer into soil and of the flowering of the derived adult palms has been conducted for cultures maintained in vitro during 1 to 20 years. From the ninth year of maintenance, the tissue quality of the somatic embryos gradually began to decline. However, after more than 20 years, 30% of the 20 clones tested still continued to proliferate satisfactorily on the same maintenance medium, keeping their multiplication potential intact. Even though a depressive effect of the age of the lines has been observed on the survival capacity of plants under natural conditions, it is noteworthy that among the clones originating from 20-year-old cultures only eight of them (40%) have exhibited the "mantled" floral abnormality. Different hypotheses concerning the origin of the disruptions observed on the in vitro cultures, plantlets and adult palms that occur over a very long period of in vitro conservation are discussed.

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In vitro micropropagation based on somatic embryogenesis provides an efficient means to multiply selected genotypes of oil palm (Elaeis guineensis Jacq.). Despite its considerable potential, somatic embryogenesis can yield plants bearing a homeotic flowering abnormality known as mantled. Because the mantled abnormality is epigenetic, it cannot be detected with conventional structural molecular markers. Thus, to develop a means of discriminating among callus cultures carrying or lacking the mantled abnormality, we used a gene expression approach. We describe two novel oil palm genes, EgM39A and EgIAA1, both of which display increased transcript accumulation in epigenetically abnormal calli. EgIAA1 codes for an oil palm relative of the Arabidopsis thaliana (L.) Heynh. AXR3/IAA17 protein involved in early auxin response and EgM39A codes for a protein of unknown function sharing sequence similarities with asparagine synthetases. In addition to their enhanced expression in somaclonal variant callus lines, both genes displayed increased transcript accumulation in response to auxin treatment. Normal seed-derived zygotic embryos germinated in the presence of auxin accumulated increased amounts of EgIAA1 transcripts after a few hours of treatment, suggesting a role in auxin response similar to that demonstrated for IAA genes in other species. The EgM39A gene also displayed enhanced transcript accumulation in auxin-treated zygotic embryos. Although only a small increase was seen after 24 h, greater changes were observed after 15 days. Both genes show potential as early markers of clonal conformity and may help to elucidate the nature of the epigenetic changes causing the mantled abnormality.