Abstract
Southeast Asia, stretching from the southern slopes of the Himalayas to Indonesia via China, Vietnam, Thailand and the Malaysian archipelago, is today considered as the true original cradle of citrus. In this area, the cultivation of certain citrus fruits dates back several millennia. The huge phenotypical diversity of citrus, the facility that citrus fruits have in hybridizing with many closely related species and genera, as well as in mutating spontaneously, did not facilitate the task of the first taxonomists. The citrus taxonomy still raises endless discussions among specialists. In this chapter, after a short discussion on the etymology of citrus names, we first present the traditional taxonomic system that is still actively used. Then, we review the recent knowledge on the phylogenetic origin of cultivated citrus and their implication in new taxonomic systems for citrus. Finally, we discuss the dispersion over the world of citrus from Asia and the role of the secondary center of diversification.