EXPLORING GENETIC DIVERSITY OF PALESTINIAN OLIVE TREES | استكشاف التنوع الجيني لأشجار الزيتون الفلسطينية

The olive tree (Olea europaea L.) holds deep cultural, ecological, and economic importance in Palestine and the broader Mediterranean region. Despite the historical and environmental relevance of Palestinian olive populations, particularly ancient trees and traditional cultivars, their genetic diversity and structure have remained understudied. This research aims to genetically characterize 142 olive samples including ancient canopy trees, rootstocks, wild olives, and local cultivars. The sampling strategy was designed to cover diverse agro-ecological zones and land use types, with samples collected from five major olive-growing governorates in the West Bank: Jenin, Tubas, Nablus, Hebron, and Bethlehem. Leaf samples were collected and georeferenced using GPS, and basic morphological characteristics were documented to support field verification and traceability. The study employed ten highly polymorphic Simple Sequence Repeat (SSR) markers to assess allelic diversity, heterozygosity, population structure, and genetic differentiation. Results revealed substantial genetic variation among the sampled populations, with an average of 13.1 alleles per locus and high observed heterozygosity (Ho = 0.820) indicating high genetic diversity. Negative fixation indices at most loci indicated a healthy level of outcrossing and minimal inbreeding. The markers UDO-043, DCA3, DCA9, and GAPU103A exhibited the highest allelic richness, demonstrating their utility in distinguishing genotypes and identifying potential candidates for breeding programs. A Neighbor-Joining (NJ) phylogenetic tree and Principal Coordinates Analysis (PCoA) both confirmed the presence of genetically distinct clusters, with the Nabali (Baladi) cultivar dominating the clonal canopy group and diverse genotypes appearing among the rootstock and wild populations. Comparison with 746 international olive genotypes further underscored the genetic uniqueness of Palestinian olives, supported by a ΦPT value of 0.245 (P < 0.001) and Nei’s genetic distance of 0.604. These results affirm that Palestine harbors valuable and distinct olive genetic resources that have been shaped by centuries of local adaptation and traditional propagation practices. The findings emphasize the urgent need to conserve ancient olive orchards as critical genetic reservoirs. Strategies such as the establishment of national germplasm banks, re-genotyping of cultivar collections, and community-based conservation efforts are essential. This research contributes to a deeper understanding of olive biodiversity in Palestine and offers foundational data for sustainable breeding programs, conservation planning, and cultural heritage preservation in the face of climate change and agricultural modernization.