Abstract: 【Objective】The aim of the experimeut is to study what the role of highly and moderately repetitive DNA sequences is play during the evolution process among different genomes in genus Oryza.【Method】 Fluorescence in situ hybridization (FISH) procedure and comparative genomic hybridization (CGH) were adopted for genome analysis of Oryza sativa, O. officinalis and O. meyeriana with C0t-1 DNA and genomic DNA from cultivated rice as probes. 【Result】The coverage percentage (%) and size (Mb) of C0t-1 DNA in cultivated rice, O. officinalis and O. meyeriana were 47.10±0.16, 38.61±0.13, 44.38±0.13 and 212.33±1.21, 269.42±0.89 and 532.56±1.68, respectively. While the coverage percentage and size of genomic DNA from O. sativa in O. officinalis and O. meyeriana were 91.0%, 93.6% and 634 Mb, 1123 Mb respectively, in which there are 365 Mb and 591 Mb in O. officinalis and O. meyeriana which come from O. sativa genomic DNA not from repetitive sequences of O. sativa, and the uncoverage size in O. officinalis and O. meyeriana were 64 Mb and 78 Mb, respectively. In addition homologous category on karyotype analysis of these three species, O. sativa, O. officinalis and O. meyeriana, was made according to C0t-1 DNA content. 【Conclusion】The results showed that highly and moderately repetitive sequences in Oryza genus were conserved during evolution over millions of years in crop species as the functional genes. The repetitive sequences reduplication might be one of the important causes of the genome enlargement of O. officinalis and O. meyeriana. O. officinalis genome enlarged more slowly compared to O. meyeriana. Based on the above results, it is concluded that the duplication, recombination, and gene selective deletion formed the two species, O. officinalis and O. meyeriana during millions of years of evolution.

Key words: C0t-1 DNA, CGH, Karyotype, O. officinalis, O. meyeriana