**3. Conclusions**

Molecular markers have become an indispensable tool in plant breeding for both biodiversity studies and quality selection of products. Marker Assisted Selection (MAS) reduces entrie redundancy in germplasm collections, reveals cases of synonymy and homonymy in several crops, let a early selection of interesting lines in breeding programs Several classes of molecular markers (ISSR, AFLP, SSR) were screened on more than 80 olive cultivars of the Mediterranean basin at the DiBCA in approximately 10 years, passing from traditional lab protocols laborious, in some cases hazardous and subjected to many environmental variables, and arriving to the use of health-safe reagents and standardized procedures. In this sense, the efficacy and the advantages showed by SSR with respect to ISSR and AFLP is well known. In particular, in olive oil traceability they revealed their ability to amplify highly degraded DNA extracted from oil. SSR generally amplify fragments of 100-300 bp, while ISSR generate amplicons of higher molecular weight (500- 2000bp) and it can be argued that a degraded DNA from oil works better with short fragments. Furthermore, the step of enzymatic digestion in the AFLP can represent a severe bottleneck when processing degraded oil DNA. For all these reasons, SSR are now widely used for cultivar identification, while more needs to be done for their use in traceability. As an example, most of the PDO oils are multivarietal, so the traceability of a single cultivar becomes hard to be verified. Thus, approaches based on quantitative Real Time PCR can help to correctly define which cultivars are present in a certain oil and in which percentages. Indeed, if the approach is based on qualitative PCR, independently from the class of molecular marker, only monovarietal oils can be traced.

Genomes of several crops and woody species have been completely sequenced and characterized, while few is known about the olive genome. However, the increasing availability of Expressed Sequence Tags (EST) deduced from mRNA extracted from olive and annotated on the web (www.Oleadb.it) represent an interesting starting point for "candidate gene" approach, with the goal of a cultivar characterization based on gene functionality. It cannot be ignored that functional genomics offer the possibility not only to distinguish cultivars merely on restricted genomic areas often harbouring intronic regions, but it let the knowledge of how gene biodiversity in olive can lead to a certain organoleptic oil profile rather than to another.

Actually, the DiBCA is attempting researches on SSR alleles specific for some Southern Italian olive cultivars, while the approach of the "candidate gene" has been enterprised to isolate and characterize genes involved in the Kennedy pathway that leads to the syntesis or desaturation of long chain fatty acids in olive oil. In the future, the complete genome sequencing of olive will offer new opportunities to better understand the evolution, the existing biodiversity and the physiological aspects of a species that fused its hystory with that of mankind all over the Mediterranean basin in the last 5000 years.
