INTRODUCTION

     The olive tree has been widely spread across the Mediterranean region since ancient times. In fact, it is considered to be the first tree to have been introduced into agriculture, a long time after humankind learned to cultivate herbaceous crops. It was not domesticated until it was realised that it could be propagated very easily by rooting large propagules. Olive cultivation is believed to date back some 6000 years in the Fertile Crescent area from where it spread throughout the Mediterranean Basin. Eventually, every village (valley, oasis, etc) selected and cloned the best trees in terms of fruit size, oil content, etc., so giving rise to varieties (cultivated varieties, cultivars).

     The olive tree has been always dry-farmed, often with associated crops, either herbaceous or woody, and almost always in poor, marginal land. Most likely because of poor productivity, this kept people looking for new varieties through the ages. Such selections were first made from neighbouring forests and then from progeny from farther afield brought by the spread of civilisations from one area to another (e.g., Phoenicians, Greeks, Romans and Arabs throughout the Mediterranean and Spaniards and Portuguese from Europe to America). As a result, every olive area now has one, or at the most two or three main varieties, and several or many varieties of less importance in terms of crop area or productivity. Owing to the difficulties in the past of transporting the large propagules needed for propagation, the cultivars of each area have not travelled far from their places of origin and are found in adjacent areas.

     Numerous collections of cultivars are now held in the Mediterranean region. However, the structure and composition of genetic olive resources are not yet fully known, nor are all the existing cultivars held in collections. Moreover, it is known that sometimes the same genotype is named differently in different olive areas, even within the same country, and that different genotypes receive the same name.

     The project set out to find answers to these questions by conducting an indepth study of all the collections. To do so, a common methodology drawn up by a team of scientists has been applied by the participant institutions in their home countries.