Primary Selection and Secondary Diversification: Two Key Processes in the History of Olive Domestication

Knowledge on the crop domestication process is important from a cultural and agricultural standpoint since it can shed light on the origin and history of human civilizations as well as the management of genetic resources, while offering guidance for modern breeding. The olive tree ( Olea europaea ssp. europaea ) is the most iconic of the old crop species of the Mediterranean Basin (MB). Primary domestication from wild olive probably occurred around 6000 BP in the Middle East. However, the question remains as to whether cultivated olive derived from a single domestication event in the Levant, followed by secondary diversification, or whether it was the result of independent domestication events. Here, we analyzed a comprehensive sample collected from 35 wild populations (722 individuals) and 410 cultivars from across the MB using nuclear and plastid DNA markers. Our genetic investigations argue in favor of a single primary domestication event in the eastern MB, followed by diffusion of the first domesticated olive and diversification in the central and western MB as key processes in the olive tree history.