The Plant Biotechnologies and Genetic Resources Programme at CIRAD uses the latest technologies to make optimum use of plant genetic diversity, and thus to boost variety improvement operations of a wide range of tropical crops in a large array of environments. Biotechnology research for tropical crops develops new methods for optimum genetic resource management, facilitates the creation and identification of elite genotypes and participates in the rapid dissemination of selected varieties. The essential basis is a rational use of genetic diversity available from germplasm collections and the refinement of gene incorporation or introgression methodologies through accurate genome mapping, marker-assisted selection and/or cloning and genetic transformation. The strength of these activities rests on efficient collaborations with partners from the South, in both the public and private sectors, and integrated research on stations in the tropics. Such research is mainly successful because it is demand-oriented, based on a multidisciplinary approach, and often conducted, within a frame of international collaborations, in close involvement with other genotyping, transgenesis, robotics and cellular imagery units, and serve as a basis for innovative research, for adaptation before effective transfer to the research stations overseas, and for training. - Molecular analysis of genetic diversity being used for the constitution of core collections permits a better characterisation of the genomic richness of the species, including its cytoplasmic components, and a linkage to genetic mapping. Genome dosage, interspecific recombination and gene introgression are often the key to quality materials and breeding efficiency of a number of tropical crops which are derived from interspecific hybrids, both of natural and artificial origin. In situ hybridization on plant chromosomes was developed in order to study these aspects in particular crops such as sugarcane and banana-plantain. - Gen