Genetic Characterization of Olive Germplasm by Molecular Markers

The olive tree is a member of the Oleaceae family, which contains the genera Fraxinus, Forsythia, Forestiera, Ligustrum and Syringa, as well as the genus Olea. Commercial olives are products of the Olea europaea L. species. There are roughly 20 species of Olea found throughout tropical and subtropical regions of the world, but only O. europaea L. produces edible fruit. The fruit of olive trees can either be processed to make table olives or milled to produce olive oil. Of the many different varieties of olives, some olives are cultivated specifically for table consumption while the majority are used for oil extraction. The origin of O. europaea in the Mediterranean basin is not clear. Since olive cultivation has been practiced in all Mediterranean basin countries for many millenia, the presence of a large number of synonymic and homonymic species is very probable. The species’ poorly-defined genetic natures give rise to several problems, both for olive nurseries and for correctly estimating the platforms needed to properly classify and exploit olive products like canned olives and oil. From a commercial perspective, the Mediterranean basin grows many varieties of olive trees, and this region alone produces 99% and consumes 87% of the world’s olive oil. Thus, a solution to this problem is highly desirable. A formidable effort has been made to characterize olive germplasm using different types of biochemical and molecular markers. This review highlights the importance of studying the degree and distribution of genetic diversity for better exploitation of olive resources and for the design of plant breeding programmes. _____________________________________________________________________________________________________________