A comparative assessment of morphological and molecular characterization among three Ziziphus species

Genetic variability of 84 accessions of three Ziziphus species including Z. spina-christi, Z. nummularia and Z. mauritiana were analyzed using a combination of morphological traits and translation initiation codon (ATG) polymorphism. Both morphological and molecular data revealed a high level of inter and intra specific variations among the accessions. Accordingly, 90.49% of amplified fragments were polymorphic among the accessions with the mean values of 0.37 for polymorphic information content (PIC), 3.31 for resolving power (RP), and 1.95 for marker index (MI). The phylogenetic clustering clearly delineated the entire germplasm into three well supported distinct clusters according to the species sources. According to the Nei's genetic identity, Z. spina-christi and Z. nummularia were the most similar species and had high differentiation with Z. mauritiana. Moreover, the highest values for Shannon’s information index (I = 0.505) and gene diversity (h = 0.347) were recorded in Z. spina-christi indicating there is higher genetic diversity compared with two other species. Four private alleles were identified in two species which could be beneficial for accessions authentication in argumentative situations. Moreover, results of the Mantel test showed there were moderate correlation between molecular and morphological matrices. In addition, estimation of bivariate correlations revealed there were significant positive and negative correlations between different variables, which offer a practical application of this information during phenotype based selection in ber improvement programs. The results of this investigation highlight the efficiency of translation initiation codon polymorphism for genetic characterization and accurate authentication of Ziziphus accessions as well as detecting and tagging morphologically important traits in this genus that would be helpful for implementation of effective conservation strategies and even broaden current genetic diversity.