Genetic diversity and molecular evolution of the internal transcribed spacer (ITSs) of nuclear ribosomal DNA in the Tunisian fig cultivars (Ficus carica L.; Moracea)

Abstract

Abstract Nuclear ribosomal DNAs were explored to establish genetic relationships among Ficus carica cultivars and elucidate its molecular evolution. Results suggest the occurrence of haplotypic and nucleotide diversity. The neighbour-joining dendrograms show a continuous diversity that characterize local resources. Furthermore, our results demonstrated that the ITS2 spacer is seating to a larger number of substitutions than the ITS1 spacer. Sequence analysis demonstrates that the ITS2 spacer is evolving 1.12 times faster than the ITS1 one. The ratio of transition/transversion of 0.278 suggests that the 5.8S gene is evolving 2.84 and 3.20 times less rapidly than the spacers ITS1 and ITS2, respectively. Molecular evolution analysis confirmed an explicit rejection of the null hypothesis in F. carica . ITS1, ITS2 spacers and the 5.8S gene evolved under a strictly neutral model of molecular evolution. A scenario of positive selection and recent expansion of F. carica genotypes across Tunisia seems to be retained.