Résumé
Biotechnological approaches play an increasing role in breeding strategies for oil palm. They are fully integrated in the rapid integration of genetic progresses aimed at broadcasting improved material to the planters. Clonal micropropagation: In the mid-seventies, the first results obtained by the strategy of reciprocal recurrent selection (RRS) and the emergence of the methods of cloning by in vitro culture led to the development of a technique of micropropagation through somatic embryogenesis which was tested initially in Côte d'Ivoire, then in Malaysia and Indonesia. This work established the utility of clonal micropropagation which was found to enable the production of high yielding clones. In addition, this development phase highlighted the difficulties related to scaling-up in relation to, on the one hand, mass production required to meet the needs of planters and, on the other hand, the genetic fidelity of the regenerated plant material. These two concerns led the Cirad-IRD team to look further into the underlying mechanisms involved in somatic embyogenesis and the somaclonal variation events induced by the regeneration techniques. The development of a regeneration protocol based on the use of embryogenic suspensions has provided us with a method which allows production on a large scale of single somatic embryos displaying structural similarities with zygotic seed embryos. Studies of the late phases of embryogenesis were carried out through the comparative analysis of the development and maturation of zygotic and somatic embryos. Research work resulted in a better understanding of the physiology of the somatic embryo during its development, the accumulation of various types of storage molecules and of the mechanisms of acquisition of tolerance to desiccation. These data are prerequisites for the production of embryos which can be stored, i.e. the production of artificial seeds and/or cryopreserved embryos. Structural and functional genomics: The Cirad/IRD laboratory is currently establishing a collection of systematically sequenced EST (Expressed Sequence Tag) cDNA clones representing genes expressed in specific tissues, developmental stages or environmental conditions of interest. Our aim is to assemble an extensive catalogue of oil palm genes which can be screened either on the basis of their sequence affinities (similarity to know genes of interest) or by using high throughput macro- or microarray screening to examine their expression patterns. In this connection, we are establishing a collection of EST clones as part of a French government-funded Genopole project. A key part of our EST project is centred on studying the functioning of the oil palm shoot apical meristem. Marker-assisted breeding is being implemented in a long-term multistage project in order to make optimum use of the existing network of field experiments by capitalising upon recent advances in molecular maker technology. Areas of interest include: molecular analysis of genetic diversity in both E. guineensis and E. oleifera germplasms; large scale development of PCR-based microsatellite marker; parallel development of three genome mapping and QTL detection projects studying key agronomic characters: resistance to Fusarium wilt in Africa; increased and stable oil palm production; and detection and introgression of E. oleifera genetic factors conferring resistance to Bud Rot in Latin America. A network of specifically designed field trials is used to validate QTL markers, to implement marker-assisted breeding strategies in oil palm, and to pursue physical mapping towards the characterisation, cloning and tagging of useful genes. Post-genomics: In order to tackle the problem of the mantled flowering abnormality, which is induced during the oil palm micropropagation process, the Cirad-IRD group has carried out studies of gene expression in tissue cultures as a means of establishing an early clonal conformity testing procedure. Today, a number of genes