A comprehensive effort was devoted to exploring, collecting and characterizing the local Maltese olive germplasm, often represented by ancient, monumental trees and by plants of uncertain origin. SSR and cp-SSR analysis of all samples enabled the identification of 46 genotypes and establishment of the correspondence between ancient trees, main local varieties and other Mediterranean cultivars. The application of plastid markers enabled identification of two lineages among Maltese genotypes, with more than 50% represented by lineage E2. Twenty-nine cases of grafting were identified among the various genotypes and lineages. In most cases, E1 canopies were grafted on E2 rootstocks, but reverse cases were also observed. The phylogenetic study of Maltese genotypes, together with hundreds of cultivars from the Mediterranean Basin and beyond, highlights the richness of Maltese olive diversity and drawing attention to the genetic similarity of some Maltese olive genotypes with neighboring Italian and Algerian varieties. These results underline the long-lasting presence of the olive in the country, contributing to the reconstruction of its phylogeny and demonstrating a possible autochthonous origin of many samples. Some still-living ancient trees are at serious risk of extinction due to abandonment, urban expansion and environmental threats. This study supports the preservation of the Maltese olive germplasm and highlights its importance as a rich genetic source to face new agronomical challenges and future climatic constraints.

A prospecting campaign in the Maltese Islands has ensured the survival of several ancient olive trees (Olea europaea L.), genetically distant from known cultivars. Most of these plants were abandoned or partially cultivated. A two-year evaluation of fruit characteristics and compositions was performed on samples collected from the main representatives of these indigenous genotypes. Analyses were carried out using Gas Chromatography, High-Performance Liquid Chromatography and Near Infrared Spectrometry. Among the fruit samples, a wide range of variations was observed. Some of the genotypes showed fruit traits suitable for table olive production. This is the case of samples with a pulp/pit ratio higher than four, such as 1Wardija, 1Caritas, 1Plattini, 1Bingemma Malta and 3Loretu, whilst 1Bidni, 1Mellieha, 2Qnotta, 3Loretu, 1Bingemma Malta and 1Caritas were suitable for dual purpose. The total phenol content ranged from 6.3 (1Wardija) to 117.9 (2Mtarfa) g/kg of fresh pulp. The average percentage of MUFA was quite low for most of the varieties. These genotypes, which presumably originated in the Maltese Islands and are well adapted to the local pedo-climatic conditions, are being propagated for the following evaluation of their bio-agronomical performance (production, suitability to intensive cultivation, environmental sustainability, product quality, etc.). The purpose is to select, among these local genotypes, the most outstanding varieties, in terms of phenolic and FA profile and agronomical potential, to spread into cultivation, thereby contributing to an increase in the quality of the local table and olive oil production, strongly linked to the territory.