Genetic Resources, from Conservation to New Cultivars

The need for new olive cultivars is an ongoing process due to the continuous developments of new cultivation techniques. The olive is an old traditional crop domesticated from the wild at various locations around the Mediterranean basin, resulting in a vast number of different cultivars in the traditional olive regions. The preference of olives for cross pollination increased the diversity within local populations. Geological and climatic changes as well as natural and directed dispersal created geographically isolated populations. The phenotypic diversity was the basis for selection and thereafter breeding of new cultivars for the developing cultivation systems. Thus, conservation of the diverse genetic resources became a major issue in the breeding effort of cultivars suitable for the new developing intensive olive industry. Methodologies to shorten the juvenile period, and the accumulation of genetic information on character dominance and character linkage enhanced the efficiency of breeding and yielded a number of new olive cultivars but remained rather arbitrary and slow. Most of the characters which modern breeding aims for, such as response to fertigation, oil quantity, oil quality, tree form and various environmental resistances, are of multi gene nature. Thus, for modern targeted breeding more accurate markers for the different required traits are needed in addition to the phenotypic ones. Such markers are presently being developed using molecular methods such as SSR and SNPs based on analogous gene expression in model plants and previously selected series of crossings. The application of recent techniques such as 454 for sequencing the functional genome of some olive cultivars will enable a better choice of the parental plants in olive breeding. In some breeding programs the use DArT technology is applied for identifying markers for specific traits. A rapid advancement in olive breeding could be expected in the near future.