The systematic utilisation of descriptive morphological characters of the tree and various tree organs permits the characterisation and discriminatory identification of varieties, which shall be called cultivars or genotypes from now on without distinction.

The morphological characters that are to be used have been selected on the basis of the following:

• Consistency between individuals and between years for the same genotype. 
• Discriminatory capacity between different genotypes.
• Possibility of guaranteeing reliable, fast, cost-effective discriminatory identification.

        This text aims to describe the methodology to be used for describing varieties of olive held in collections or in the field by means of a set of 32 morphological characters (of the tree, the adult leaf, the inflorescence and of the well developed fruit and endocarp).

        The morphological characters have been arranged in terms of specific quantitative or qualitative descriptors. In the first case groups have been created with sufficiently broad intervals. These make it possible to grade real measurements according to a conventional, ascending scale of categories which is given in brackets. In the second case, the categories established are very simple and clearly identifiable.

        Fifteen of the characters considered are marked by an asterisk (*) to indicate that they are particularly useful since they enable discrimination between morphologically different cultivars.

        These discriminatory characters are very heritable. They are little influenced by the environment and have proven their worth in distinguishing between varieties, both in collections and in field surveys, which is why they will be used to determine the existence (within a collection or between collections) of morphologically different varieties.

        In principle, the quantitative and qualitative characters with less discriminatory capacity are only valid for characterising genotypes within a collection (or within an area and farming system if plant material is being surveyed in the field). Consequently, for descriptors of this type to be given their true relative value, the database of each collection begins with a series of details regarding the geographical location and growing conditions of the collection.