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.

Analysis of Genetic Diversity and Relationships in a Tunisian Fig （Ficus carica） Germplasm Collection by Random Amplified Microsatellite Polymorphisms

The random amplified mirosatellite polymorphism method was performed in a set of Tunisian fig landraces using eighteen primer combinations. A total of sixty three random amplified microsatellite polymorphism （RAMPO） markers were scored and used either to assess the genetic diversity in these cultivars or to detect cases of mislabeling. Opportunely, data proved that the designed procedure constitutes an attractive and fast method with low costs and prevents radio exposure. As a result, we have identified the primer combinations that are the most efficient to detect genetic polymorphism in this crop. Therefore, the derived unweighted pair-group method with arithmetic averages （UPGMA） dendrogram illustrates the genetic divergence among the landraces studied and exhibits a typically continuous variation. Moreover, no evident correlation between the sexes of trees was observed. In addition, using these markers, discrimination between landraces has been achieved. Thus, random amplified mirosatellite polymor- phism is proved to be powerful for characterizing the local fig germplasm.