DNA Composition and Mitotic Time Cycle Duration in the Evolution of Faba Bean and Its Wild Relatives
The ITS1-5.8S-ITS2 region of the 18S-28S nrDNA was sequenced in 49 Vicia species and subspecies selected from nine sections of the two subgenera to resolve taxonomic contradictions. Phylogenies derived from the internal transcribed spacer (ITS) sequences strongly support the view that both Vicia faba and Vicia bithynica are distant from the Narbonensis species complex (NSC) in section Faba. V. faba is more closely aligned with sections Peregrinae and Hypechusa, whereas V. bithynica is more closely aligned with section Vicia. Six synapomorphic substitutions unique to the NSC support a separate section for the Narbonensis complex. Vicia johannis subsp. johannis was the most diverged species within the NSC with high genetic distance between V. johannis subsp. johannis and remaining species and subspecies of the NSC. These results suggest that Vicia johannis subsp. johannis should be given species rank. The neighbor-joining and parsimony based trees supported the sections Vicia (after the exclusion of Vicia lathyroides) and Cracca (after the exclusion of Vicia vicioides and Vicia hirsuta). The section Hypechusa is polyphyletic and paraphyletic based on the present ITS sequence cladistic analysis. The x = 7 as the ancestral number for the genus is supported by the present study.