From an economic point of view, citrus fruits occupy first place in terms of world fruit production, with 95 million tons produced annually. The Mediterranean basin accounts for 20% of the total by itself, with one major producer: Spain.

Because of their content of micronutrients (vitamin C, carotenoids, polyphenols, etc.), citrus fruits contribute to nutritional balance for both Northern and Southern populations. Nutritional and organoleptic qualities are thus important components of selection projects at the international level. This production network is confronted with increasing biotic and abiotic pressures, and global climate change has augmented the risk of extension of emerging diseases from hot regions to the Mediterranean Basin.

Within the framework of the development of integrated protection systems, the creation of varieties and graft suports which combine tolerance to these constraints and good quality characteristics constitutes a major challenge. Because of the length of the juvenile phase (5 to 10 years) and the large number of offspring to be analyzed, a knowledge of the physiological and genetic determinants of selected characteristics and the development of early selection markers are essential.
Compared to their economic importance, the international research plans are insufficient, and the establishment of close collaborations between groups seems necessary. The creation of an international consortium on sequencing and genomics of citrus fruit, which is currently underway, seems to be a step in the right direction. This project fits into studies on integrative biology being performed in the domains of the response to abiotic stress, quality development and developmental biology by French and Spanish pluridisciplinary groups engaged in projects for the creation of new varieties and graft supports. It should contribute to the development of a European pole for research on citrus fruit cultivation, and to a good positioning of French groups within the international consortium on citrus fruit genomics.