Menara gardens: a Moroccan olive germplasm collection identified by a SSR locus-based genetic study

The Menara gardens in Marrakech (Morocco), established in the 12th century, comprise more than 2000 olive trees. To assess the genetic diversity within these gardens, we performed SSR analysis of 128 randomly sampled olive trees. Using 15 SSR loci which revealed 70 alleles, we identified 16 distinct genotypes. The analysis of chloroplast DNA polymorphism allowed to identify 2 chlorotypes: COM1 for 2 genotypes and CE1 for all others. Among the 128 trees analysed, Picholine marocaine was the prevalent cultivar represented by 100 trees (78%), the 28 remaining trees being classified into 15 distinct genotypes. However, four genotypes were closely related to Picholine marocaine from which they probably derived through somatic mutations. The genotypic and genetic diversity observed in Menara gardens compared with the genotype diversity from different areas (North and Atlas); these facts support the hypothesis that these gardens have been planted with trees probably originating from different areas of Morocco. Our results point out an important concept for ex situ conservation: the assumption that local Moroccan olive germplasm was empirically, but not purposively, conserved already in Menara gardens.