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Genetic variability in date palm genotypes collected from different regions of southern Tunisia was analyzed using a Start Codon Targeted (SCoT) marker system. Thirty-one accessions collected from three locations were investigated. One hundred and nine amplicons were produced among which 84 % were polymorphic. The PIC value and the Rp values testified of the efficiency of used primers. The percentage of polymorphic loci (Pp) varied from 44.57 to 83.70 %, Nei‘s gene diversity (H) from 0.175 to 0.273 with a mean of 0.228, and Shannon‘s information index (I) values ranging from 0.257 to 0.409 with an average value of 0.338 were illustrated. The Tunisian date palm populations exhibited high genetic differentiation (GST = 0.319) and gene flow (Nm = 1.063). The AMOVA analysis presented 70 % of the variation within the population and 30 % of the variation between them. Phylogenetic analysis and the Bayesian clustering approach also revealed high genetic variation among genetic variants with a net divergence of the wild insular population of Kerkennah from other cultivars. The present investigation suggests the effectiveness of the SCoT marker system to estimate the genetic diversity of Phoenix dactylifera genotypes.

Date palm is a relatively salt- and drought-tolerant plant and more recent efforts have been focused on recognizing genes and pathways that confer stress tolerance in this species. The cDNA start codon targeted marker (cDNA–SCoT) technique is a novel, simple, fast and effective method for differential gene expression investigation. In the present study, this technique was exploited to identify differentially expressed genes during several stress treatments in date palm. A total of 12 SCoT primers combined with oligo-dT primers amplified differentially expressed fragments among the stress treatments and control samples. Differentially expressed fragments were highly homologous to known genes or encoded unclassified proteins with unknown functions. The expression patterns of the genes that had direct or indirect relationships with salinity and drought stress response were identified and their possible roles were discussed. This study suggests that the cDNA-SCoT differential display method is a useful tool to serve as an initial step for characterizing transcriptional changes induced by abiotic stresses and provide gene information for further study and application in genetic improvement and breeding in date palm.

The cytochrome oxidase subunit I (COI) gene was amplified and analyzed for 70 Mediterranean Chondrosia reniformis, collected from eight localities in Tunisia. Polymorphism results revealed high values of haplotype diversity (Hd) and very low nucleotide diversity (π). Thus, these results suggest that our sponge populations of C. reniformis may have undergone a bottleneck followed by rapid demographic expansion. This suggestion is strongly confirmed by the results of neutrality tests and “mismatch distribution”. The important number of haplotypes between localities and the high genetic differentiation (Fst ranged from 0.590 to 0.788) of the current C. reniformis populations could be maintained by the limited gene flow Nm (0.10 - 0.18). Both haplotype Network and the biogeographic analysis showed a structured distribution according to the geographic origin. C. reniformis populations are subdivided into two major clades: Western and Eastern Mediterranean. This pattern seems to be associated with the well-known discontinuous biogeographic area: the Siculo-Tunisian Strait, which separates two water bodies circulating with different hydrological, physical, and chemical characteristics. The short dispersal of pelagic larvae of C. reniformis and the marine bio-geographic barrier created high differentiation among populations. Additionally, it is noteworthy to mention that the “Mahres / Kerkennah” group diverged from Eastern groups in a single sub-clade. This result was expected, the region Mahres / Kerkennah, presented a particular marine environment.