Patterns of genetic structure and evidence of gene flow among Tunisian Citrus species based on informative nSSR markers

This study investigates the extent of genetic diversity, phylogenetic relationships and the amount of gene flow among Tunisian Citrus species based on a set of 15 informative nuclear SSR molecular markers. Genotyping data highlighted an allelic richness among Tunisian Citrus species and has allowed the detection of 168 alleles among them 104.19 were effective. The partition of the total genetic diversity (HT = 0.832) showed that the highest amount of variation within the Citrus species is HS = 0.550, while the relative amount of the between-species genetic diversity GST does not exceed 0.338. This pattern of genetic structure was supported by low-to-moderate FST pairwise values and the presence of a gene flow (Nm) among the eight Citrus species. The lowest genetic differentiation was revealed between the species C. sinensis and C. insitorum (FST = 0.111, Nm = 1.99), while the highest genetic differentiation was recorded between the species C. aurantifolia and C. paradisi (FST = 0.367, Nm = 0.43). The established Neighbor Joining analysis showed that all genotypes were widely discriminated and clearly pooled according to their species of origin, with minor exceptions.