ITS Regions in Diploids of Aegilops (Poaceae) and their Phylogenetic Implications

The nucleotide sequences of the internal transcribed spacer (ITS) of nuclear ribosomal DNA in nine diploid species representing six sections of Aegilops were determined by direct sequencing of PCR-amplified DNA fragments. These sequences were aligned with two ITS sequences of additional species from Genbank. Sequence divergences were estimated using Kimura two-parameter model, and the phylogenetic analyses were performed using the maximum parsimony (MP) and the neighbor-joining (NJ) methods with PAUP and PHYLIP, respectively. The sequence divergences between the diploid species varied from 0.5% to 4.68%. The resulting MP tree and NJ tree showed relatively congruent phylogenetic relationships among these species, except Ae. caudata. Particularly, Ae. speltoides was basal within the two trees. The paraphyletic relationships between Ae. speltoides and two species of Sect. Sitopsis, and between Ae. uniaristata and two species of Sect. Comopyrum were supported strongly. The ITS data suggest that currently recognized sections within Aegilops should be reconsidered.