ARS | Publication request: PHYLOGENETIC RELATIONSHIPS OF THE MONOGENOMIC SPECIES OF THE WHEAT TRIBE, TRITICEAE, INFERRED FROM SEQUENCES OF THE INTERNAL TRANSCRIBED SPACER REGION IN NUCLEAR RIBOSOMAL DNA

Submitted to: Genome Research
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 1994
Publication Date: N/A

Technical Abstract: Sequences of the ITSs and 5.8S subunit ranging from 598 to 603 nucleotides of nuclear ribosomal DNA (rDNA) were obtained by direct double stranded sequencing of PCR amplified DNA. The sequences from 26 mono- genomic species of Triticeae, belonging to 17 genomes (A, B, D, E, F, G, H, I, J, K, N, O, P, S, T, R, and W) and a diploid out-group species, Bromus tectorum, were analyzed phylogenetically. A phylogenetic tree inferred from the ITS sequences of 24 Pooideae species indicates the position of Triticeae in the subfamily. Species of each genome clustered together as monophyletic groups and suggest that the designated genomes reflect biolog- ical relatedness. Hordeum (I) is the earliest diverging lineage within the tribe. Critesion (H), the closest relative of Hordeum, diverges next followed by Psathyrostachys (N). Four perennial genera, Agropyron (P), Australopyrum (W), Pseudoroegneria (S) and Festucopsis (G) form a sister group to the Med. region distributed lineage (annuals). Among the species uniquely distributed in the Med. region, two perennial genera, Lophopyrum (E) and Thinopyrum (J), are closest relatives to annual diploid wheat (A). Henrardia (O) and Eremopyrum (F) are clustered with Sitopsis (B) and Crithopsis (K). Taeniatherum (T) and Secale (R) form a monophyletic clade with the Med. distributed species. The unanticipated incongruency between the molecular and morphological phylogenies and biogeography of the tribe, suggest that the Triticeae species of the Mediterranean region are monophyletic and shared a Psathyrostachys-Hordeum-like ancestor with sister taxon distributed in the temperate region. Morphological similarities between the two are due to retention of ancestral characteristics. These data strongly suggest that Triticeae is an example parallel evolution.