Sequences Evolution and Population Structure of Tunisian Date Palm (<em>Phoenix dactylifera</em> L.) Revealed by Chloroplast DNA Markers

Date palm is present among the vital crops of arid and semiarid countries of North Africa and the Middle East. Chloroplast DNA is the best molecule for finding the evolutionary history of plant species. In the present study, cpDNA variation in date palm was estimated using the trnL-trnF intergenic spacer and psbZ-psbC region. The high AT values in both molecular markers may clarify the high proportion of transversions observed in this species. The neutrality tests, expansion parameter estimation (mismatch distribution), and haplotype network patterns proposed that demographic expansion had occurred in recent times. Furthermore, the taxa distribution is not related to geographical origins; neighbor-joining trees are clustered independently either from their geographic origin or from the sex of trees, suggesting a common genetic basis between different cultivars. Statistical analysis of chloroplast germplasm provides a means of assessing cytoplasmic gene flow, which occurred in Tunisian Phoenix dactylifera L. In fact, Nm was important between Tunisia and Eastern Arabic region (Nm = 2.57), which reflects high levels of connectivity between these population pairs. In conclusion, genomic studies prove date palm domestication happened in the Arabian Peninsula and showed an important gene flow with North African palm populations

Genetic Diversity and Structure of Tunisian Local Pear Germplasm as Revealed by SSR Markers

Growing pear has a long tradition in Tunisia, and numerous local cultivars possessing an excellent adaptability and resilience potential to climatic variation are present. This large adaptability is associated with an important genetic diversity, which is threatened to erosion. Appropriate measures have to be taken in order to properly evaluate and conserve this local material. Microsatellite markers were used to assess the level of genetic diversity among Tunisian pear germplasm, and compare it with some European varieties and wild pear species. 61 pear accessions representing eight groups (six groups from Tunisia, one from Northern Europe and another group composed of wild pear) have been genotyped using SSR markers derived from apple and pear. The pear accessions showed a significant polymorphism and 95 polymorphic alleles were found. The number of alleles per locus varied from 5 for CH04e03 locus to 14 for CH01d09 locus with an average of 9.4 alleles per locus. Moreover, the mean gene diversity (H-e) per locus ranged from 0.192 to 0.752. Genetic distance values and cluster analyses revealed high genetic similarities among the Tunisian groups. Factorial correspondence analysis (FCA) categorized the accessions into three independent groups where Tunisian local accessions agglomerated together distantly from European and wild pear accessions. Additionally, UPGMA dendrogram grouped accessions into two clusters, confirmed thereafter by the Bayesian model-based Structure analysis. The results showed 16 putative triploid accessions found in the local germplasm. This study provides valuable information to develop strategies of local pear conservation and use