A family tree for the olive tree
The olive tree, Olea europaea, has played an important role not only in agriculture but also in ancient as well as modern culture. Cultivated for its fruit and for oil derived from its fruit, the olive tree was domesticated long ago and has since spread from the Mediterranean to all corners of the world. However, the tree's exact roots, to play on words, were not well known. The 'Historical genomics of the mediterranean olive tree' (Genolive), with funding from a Marie Curie Fellowship, helped advance our knowledge of the olive tree's past, creating a family tree for the olive tree if you will. Genetic sequencing was used to differentiate between species that recolonised the Mediterranean region after the last glacial period and those arising from domestication. In particular, researchers studied the chloroplast DNA (cpDNA) of specimens located throughout the Mediterranean. The resulting genomes and genome datasets were analysed and revealed high levels of diversity in Morocco and southern Spain, the Aegean and the Levant, including Cyprus. In fact, evidence pointed to the Levant as the origin of the first cultivated olive tree. Data from the project also shed light on the how the olive tree migrated to Australia, where it has achieved the status of invasive species. In addition, genetic markers were developed that can be used to determine the source of olive oil purchased at the local market. Finally, a recommendation was made to collect and preserve genetic material from wild olive trees from around the Mediterranean before it's lost forever.
