[Objective] Genomic in situ hybridization (GISH) was used to study the relationship between the two CCDD genomes of Oryza alta and Oryza latifolia. [Method] Total DNA of Oryza officinalis (C-genome) was used as a probe for genomic in situ hybridization on metaphase chromosomes from Oryza alta and Oryza latifolia, respectively. [Result] Under certain post-hybridization washing stringencies, C- and D-genome could be distinguished in CCDD genome type; there were huge differences in some CC chromosomes of Oryza alta, Oryza latifolia, and Oryza officinalis. The genome of Oryza latifolia was more original. [Conclusion] Comparative analysis of the Oryza species with identical genome type may facilitate to elucidate the possible approaches to plant genome evolution and species evolution.
