Abstract: Oryzeae (Poaceae) is a tribe belonging to Poaceae and consists of about 12 genera. This tribe contains many economically important species, and is distributed in tropical and temperate regions worldwide. Recently, investigation on the genus Oryza and its related genera in the Oryzeae has attracted much attention for their important economic value and taxonomic position in the study of plant biology in general. Although morphological and preliminary molecular evidence has shown that the tribe Oryzeae is a monophyletic group, there are still many questions as to its systematics and evolution to be answered. In this review, we briefly retrospect the history and progress of the studies on the classification and phylogeny of Oryzeae, including its establishment and systematic position, its circumscription and subdivision, the relationships of genera in the tribe, and the distribution and origin of the tribe. Recent results indicate that (1) Oryzeae is monophyletic and falls into two main clades corresponding to the traditionally recognized subtribes (Zizaniinae and Oryzinae); (2) Close affinities of the monoecious genera are not supported, suggesting the multiple origins of unisexual florets; (3) Previous recognition of three monotypic genera (Hydrochloa, Porteresia and Prosphytochloa) is not justified; (4) Based on dating using molecular clock approach, it is estimated that Oryza and Leersia branched off from the remaining genera of Oryzeae ~20 million years ago (MYA), and separated from each other ~14 MYA. A divergence time of ~9 MYA is also obtained for the most basal split within Oryza. In conjunction with our recent molecular studies, we present some progresses on the molecular phylogeny of Oryzeae and discuss the questions to be solved in the future study of this tribe.

Key words: Oryzeae, Poaceae, phylogeny, evolution, biogeography.