Exploring the genetic diversity of monumental olive trees from southwestern Sicily

Sicily has a remarkably rich olive germplasm of autochthonous cultivars and centennial genotypes which could be used to breed resistant genotypes against emerging diseases, such as Xylella fastidiosa, and hostile climatic conditions. In this study, productive centennial monumental olive trees were identified on-farm from the southwestern part of the island, geolocated and characterized at both the morphological and molecular levels. The criterion of tree selection was based on their height, trunk size, and alleged age (more than 400 years old). For the phenotypical characterization, the main traits of leaf, fruit, and endocarp, were measured. A set of 10 highly polymorphic simple sequence repeat (SSR) markers were employed for the genetic characterization. Some of the centennial trees found showed a molecular profile identical to well-known local cultivars, therefore they can be considered “patriarch” trees (“mother plants”) of Sicilian cultivars, while others presented unique profiles. A significant level of still unexplored Sicilian olive genetic diversity was discovered potentially holding interesting biotic/abiotic resilience as well as architectural and plant vigor traits useful for breeding, which was well-preserved thanks to the community of local growers. The Department SAAF - University of Palermo has started the vegetative propagation of these trees in an ex situ collection for future characterization of biotic/abiotic stress resistance and agronomical performance as well as has undertaken initiatives to valorize these living monuments also by including their information and location in naturalistic itinerary guides.