Genetic diversity of Tunisian melon (Cucumis melo. L) landraces and their relationships with introduced varieties as assessed by simple-sequence repeat (SSR) markers

The genetic diversity and the relationships among Tunisian melon landraces and introduced varieties belonging to different varietal groups were estimated using six simple-sequence repeat (SSR) markers. All loci were polymorphic and provided a total of 56 alleles, with an average of 9.33 alleles per locus. The allelic frequencies differed according to accessions, and particular alleles were found within several accessions. The polymorphism information content (PIC) values ranged from 0.568 to 0.866, with an average of 0.754, and the level of the genetic diversity differed according to sites. The genetic differentiation among landraces fit a model of isolation by distance; that among introduced varieties and landraces was high suggesting a low level of gene flow between the two sets of melons. The dendrogram based on Nei’s genetic distances produced two major groups of accessions. The inodorus introduced varieties were distinctly different from all other accessions. The dudaim accessions were clearly separated from the reticulatus ones which were dispersed among local landraces grouped according to their geographical origin. The close molecular relatedness between local landraces and reticulatus accessions indicates that local melons have been presumably developed from the group reticulatus introgressed with the inodorus one. Based on these findings, conservation strategies of landraces are discussed. Key words: Cucumis melo, genetic diversity, introduced varieties, SSR markers, Tunisian melon