Molecular phylogeny of Oryzeae (Poaceaf) based on DNA sequences from chloroplast, mitochondrial, and nuclear genomes

The phylogeny and evolutionary history of the rice tribe (Oryzeae) were explored using sequences Of like DNA fragments (matK, trnL, nad1, Adh2. and GPA1) from chloroplast. mitochondrial, and nuclear genomes, Results indicate that (1) Oryzeae is monophletic and falls into two main clades corresponding to the traditionally recognized subtribes: (2) previous recognition of three monotypic genera (Hydrochloa, Porteresia, and Prosphytochloa) is not justified: and (3) close affinities of the monoecious genera are not supported, suggesting the possibility of multiple origins of unisexual florets. Based on the magnitude of matK and GPA1 sequence divergence, we suggest that Oryza and Leersia branched off from the remaining genera of Oryzeae 20 million years ago (mya). and separated from each other similar to 14 mya. A divergence time of similar to 9 mya is obtained for the most basal split within Oryza. These estimates suggest that Oryzeae diverged during the Miocene, and thus imply that long-distance dispersal appears to be one of the important factors in the diversification of the tribe.