Characterization and conservation of “Olivo della Strega”: an ancient olive tree, precious resource for natural and cultural heritage.

The olive is a long-lived evergreen tree, capable of regenerating itself from any part of the plant (pollard tree). This characteristic has allowed the olive trees to survive across the centuries until they become real natural monuments. The aim of this work has been to study the monumental “Olivo della Strega” (“Witch’s Olive tree”) olive tree, located in the olive orchard of Santissima Annunziata church, in Magliano (Grosseto, Italy), a tree with a special place in local history and folklore and with estimated age over 700 years. The morphometric data of leaf, fruit, stone and pollen were used to characterize the phenotype, while genetic diversity was assessed on the basis of microsatellite markers. The morphological and genetic analysis pointed to two clearly distinguishable parts in the “Olivo della Strega” tree, called sample left (SL) and sample right (SR). This ancient plant consists of two different genotypes: one part (SL) was identified as cv Frantoio and the other (SR) as an unknown genotype. Moreover, traditional (in vivo conservation) and advanced techniques (cryopreservation) have made conservation achievable to preserve its genetic heritage. In particular “Olivo della Strega” pollen was stored for 1 year in liquid nitrogen. The morphology of pollen grains, viability and germinability of fresh and long term cryopreserved pollen were observed at different times during preservation, without revealing significant differences.