Abstract: Taxonomy is a tool for organism recognition, an understanding of phylogenetic relationships among organisms, a guide for germplasm utilization, and a common language for communication. Therefore, a taxonomic treatment needs to reflect our current understanding of such relationships. In nature, there are only two absolute units of living organisms: individuals and species. A species is a group of individuals who are connected to each other as a unit by their indispensable relationships of breeding. Reproductive separation is an essential boundary between species, and the only factor to form independent gene pools during organismal evolution. Since there is no absolute boundary among taxa above species, any taxonomic treatments above species cannot avoid arbitrariness. Nevertheless, some classification should be made for the convenience of their description, utility and/or study. This paper classifies the biosystematic relationships among taxa in Triticeae on the basis of genetic studies. The principles for our taxonomic treatment are: (1) reflecting the current understanding of the phylogeny among the species involved, (2) being convenient for germplasm utilization, and (3) avoiding unnecessary radical change apart from the tradition.

Key words: Taxonomy, genus, classification principle, biosystematics, genome.