Fluorescence in situ hybridization （FISH） and comparative genomic hybridization （CGH） were applied to somatic chromosomes preparations of Oryza sativa, O. officinalis, and O. meyeriana with labeled probes of Cot-1 DNA and genomic DNA＇from the cultivated rice. The coverage percentage （%） and size （Mb） of Cot-1 DNA in O. sativa, O. officinalis, and O. meyeriana were 47.1 ±0.16, 38.61 ±0.13, 44.38＋_0.13, and 212.33 ± 1.21,269.42 ± 0.89, 532.56± 1.68 Mb, respectively. The coverage percentage and size of genomic DNA from O. sativa in O. officinalis and O. meyeriana were 91.0, 93.6% and 634, 1 123 Mb, respectively, in which 365 and 591 Mb in O. officinalis and O. meyeriana were from O. sativa genomic DNA, but not from repetitive sequences of O. sativa, and the uncoverage genome size in O. officinalis and O. meyeriana were 64 and 78 Mb, respectively. In addition, karyotype analysis was conducted based on the signal bands of Cot-1 DNA in O. sativa, O. officinalis, and O. meyeriana. The results showed that highly and moderately repetitive sequences in Oryza genus were conserved as the functional genes during evolution. The repetitive sequences reduplication may be one of the important causes of the genome enlargement of O. officinalis and O. meyeriana, and O. officinalis genome enlarged more slowly when compared with O. meyeriana. Based on the above results, it is concluded that O. officinalis and O. meyeriana were formed by reduplication, rearrangement, and gene selective loss during the evolution process.
LAN Wei-zhenHE Guang-cunWANG Chen-yiWU Shi-junQIN Rui
Fluorescence in situ hybridization (FISH)was applied to somatic chromosomes preparations of Oryza officinalis Wall. (CC), O. sativa L. (AA)×O. offi-cinalis F1 hybrid (AC), backcross progenies BC1 (AAC and ACC), O. latifolia Desv. (CCDD), O. alta Swallen (CCDD) and O. punctata Kotschy (BBCC) with a labelled probe of C0t-1 DNA from O. officinalis. In O. officinalis, the homologous chromosomes showed similar signal bands probed by C0t-1 DNA and karyotype analysis was conducted based on the band patterns. Using no blocking DNA, the probe identified the chromosomes of C genome clearly, but detected few signals on chromosomes of A genome in the F1 hybrid and two backcross progenies of BC1. It is obvious that the highly and moderately repetitive DNA sequences were considerably different between C and A genomes. The chromosomes of C genome were also discriminated from the chromosomes of D- and B-genome in the tetraploid species O. latifolia, O. alta and O. punctata by C0t-1 DNA-FISH. Compari-son of the fluorescence intensity on the chromo-somes of B, C and D genomes in O. latifolia, O. alta, and O. punctata indicated that the differentiations between C and D genomes are less than that be-tween C and B genomes. The relationship between C and D genomes in O. alta is closer than that of C and D genomes in O. latifolia. This would be one of thecauses for the fact that both the genomes are of the same karyotype (CCDD) but belong to different spe-cies. The above results showed that the C0t-1 DNA had a high specificity of genome and species. In this paper, the origin of allotetraploid in genus Oryza is also discussed.
