Genetic characterization of Libyan date palm resources by microsatellite markers

Molecular typing of 377 female date palm trees belonging to 18 Libyan cultivars and representing common genotypes in the central Libyan oasis of Al Jufrah was performed using 16 highly polymorphic microsatellite or SSR loci. A total of 110 alleles with an average of 6.88 alleles per locus were scored indicating the high level of polymorphism existing among the cultivars thus allowing their genetic fingerprinting. Moreover 28 alleles out of 110 were fixed. All the cultivars were characterized by negative values of the Fixation Index (F) due to an excess of heterozygotes with respect to HW equilibrium. The pattern of genetic diversity among cultivars was estimated by codominant genetic distances and presented by principal coordinates analysis (PCoA). The observed pattern evidences the genetic diversity existing among cultivars that allow distinguishing them easily. The average dissimilarity internal to each cultivar ranged from 0 to 21. Seven cultivars showed value zero indicating no genetic difference within cultivar in agreement with their Fixation Index (F = 1). A varietal identification key was also built using multiloci genotyping with only three microsatellite loci that identified 23 alleles in total. The possibility to attribute the unknown male plant to a cultivar was also considered and male parentage analysis was performed. Fifty-five male plants out of 63 were assigned to a definite cultivar with high confidence level. The positive result obtained in identifying males confirmed the suitability of SSR for clone fingerprinting and cultivar identification, thus opening new prospects for date palm breeding.