The genus Oryza consists of two cultivated species (O. sativa L. and O. glaberrima Steud.) and approximately 20 wild relative species widely distributed in the pan-tropics. These species have been classified into four complexes following the Vaughan's taxonomic system([1]). The O. officinalis complex is the largest complex in the genus, which includes ten species, having BE, CC, on, and EE genomes in the diploids as well as BBCC and CCDD genomes in the tetraploids. The relationships among the BE, CC, and EE genomes still remain unclear, although previous studies have indicated certain affinities of these genomes([2-4]). Genomic in situ hybridization (GISH) is a powerful technique to detect the relationships among the related genomes at chromosome and DNA levels. The objective of the present study was to investigate the relationships among the BE, CC and EE genomes in the genus Oryza by the two-probe GISH.
