The history of olive cultivation in the southern Levant

Abstract

The olive tree (Olea europaea L. subsp. europaea var. europaea) is one of the most important crops across the Mediterranean, particularly the southern Levant. Its regional economic importance dates at least to the Early Bronze Age (~3600 BCE) and its cultivation contributed significantly to the culture and heritage of ancient civilizations in the region. In the southern Levant, pollen, pits and wood remains of wild olives (O. europaea subsp. europaea var. sylvestris) has been found in Middle Pleistocene sediments dating to approximately 780 kya, and are present in numerous palynological sequences throughout the Pleistocene and into the Holocene. Archeological evidence indicates the olive oil production from at least the Pottery Neolithic to Chalcolithic transition (~7600-7000 BP), and clear evidence for cultivation by, 7000 BP. It is hypothesized that olive cultivation began through the selection of local genotypes of the wild var. sylvestris. Local populations of naturally growing trees today have thus been considered wild relatives of the olive. However, millennia of cultivation raises questions about whether genuine populations of var. sylvestris remain in the region. Ancient olive landraces might thus represent an ancient genetic stock closer to the ancestor gene pool. This review summarizes the evidence supporting the theory that olives were first cultivated in the southern Levant and reviews our genetic work characterizing local ancient cultivars. The significance and importance of old cultivars and wild populations are discussed, given the immediate need to adapt agricultural practices and crops to environmental degradation and global climate change.

Keywords: archaeobotany; crop wild relatives; landraces; olives; palynology.

Figure 1

Naturally growing olives trees in the Galilee, Israel (A) showing a bushy Bonsai form with juvenile leaves, (B) a feral individual growing in the Negev desert.

Figure 2

The distribution of cultivated olive landraces and naturally growing trees in the area of Israel and the Palestinian Authority (presented in green color). Information was gathered from the BioGis, Israel biodiversity website (https://biogis.huji.ac.il/eng/home.html). Naturally growing feral trees are found throughout the cultivation area (Barazani et al., 2016), while genetic evidence of populations of the wild var. sylvestris were found in the presumed hypothetical distribution range of wild olives (Zohary et al., 2012) (diagonal stripe lines).

Figure 3

Rooting success (average ± std) of cuttings of MLL1 and MLL7. Leaf cuttings were taken from trees growing in a live germplasm collection (Gilat Research Center, Israel) and rooting success was evaluated over two subsequent years.

Figure 4

Results of the Multi-locus lineage (MLL) analysis of olive trees growing in traditional groves. (A) The analysis included trees that were sorted by their cultivar names: Souri (n=61), Souri Rumi (n=15), Nabali Baladi (n=16), Nabali Muhasan (n=24), and Malisi (n=7). The analysis also included representative samples belonging to MLL7 genetic group (n=17) (Barazani et al., 2014), and several Mediterranean cultivars, Arbequina, Coratina, Koroneiki, Picual, and Barnea (n=3-5). (B) The MLL characterization in the pie diagram is presented according to colors, e.g. Souri, Souri Rumi, Nabali Baladi and Malisi (n=4) were clustered together in the same MLL1 genetic group.