The use of cellular mass propagation techniques through somatic embryogenesis (SE) often depends on the efficiency of early stage tissue culture. Indeed, the control of initiation of "high frequency" callus, primarily containing embryogenic cells is typically for use in a routine, or for application to several genotypes. Moreover, cellular proliferation through cell suspension, while maintaining embryogenic potential, is stressful for the cellular materialand may have dramatic effects on the regeneration process and the conformity of regenerated plants. For more than twenty years, CIRAD has been involved in developing SE on many tropical crops. Until now, the use of histological approaches allowed for improvement of the propagation techniques to reach pilot production. Mass production for commercial use, however requires better knowledge and control of the process. Molecular techniques will provide new tools for understanding gene expression involved in SE. The aim of the work presented here is to carry out a molecular analysis of SE on two tropical model plants: coffee-tree and banana. Our approach includes a molecular study of both key steps of the SE process (i.e. early stages and cell suspension). Molecular ressources such as Substractive Suppressive Hybridization (SSH) based on cDNA libraries have been developped and will be used for a transcriptome approach. In addition, a genome methylation study through Methylation Sensitive Amplification Polymorphism (MSAP) has been performed to evaluate genome structure change during SE. (Texte intégral)