Science and Research Branch, Islamic Azad University, Tehran, Iran.
The genus Onobrychis is subdivided into two subgenera: Onobrychis and Sisyrosema. Phylogenetic relationships of 19 species of Onobrychis (Fabaceae: tribe Hedysareae) and one representative each of genera Eversmannia and Ebenus were estimated from DNA sequences of the internal transcribed spacer (ITS) region. Parsimony analysis of the ITS region formed a dendrogram with strong bootstrap support from two groups: Onobrychis subgen. Onobrychis (except O. laxiflora) is in one group and Onobrychis subgen. Sisyrosema is in the other. Within group I, species of the Onobrychis section and species of the Lophobrychis and Dendrobrychis sections form well supported branches A and B, respectively (BP=99% and 91%). The close association between the Onobrychis section and Lophobrychis and Dendrobrychis indicated there is strong sequence homology among them, suggesting that these species are closely related
in terms of phylogeny. Also there is strong sequence homology among sections of Sisyrosema subgen. (group II). Species of Heliobrychis, Hymenobrychis and Afghanicae form a branch (branch C) with 77% bootstrap support. Species of the Hymenobrychis section form a clade (clade F) with 82% bootstrap support, which indicates these species are closely related. The present nrDNA ITS data showed that Onobrychis subgen. Sisyrosema appears to be a well-supported monophyletic group (BP=77%), whereas the Onobrychis subgen. Onobrychis is not monophyletic due to the sister group relationship of one species of Onobrychis subgen. (O. laxifolra) to the subgen. Sisyrosema. Cluster analysis of morphological characters showed two major groups separating Onobrychis subgen. Onobrychis (except O. laxiflora) from Onobrychis subgen. Sisyrosema, which are in accordance with molecular phylogenetic groups.