Molecular cytological diversity in cultivated rice Oryza sativa subspecies japonica and indica

Abstract

In cultivated rice Oryza sativa, although physiological and molecular biological studies have demonstrated the existence of a high intra-species diversity, there are few reports related to the molecular cytological diversity. To examine the molecular cytological diversity in O. sativa, a tandem repeat-sequence Os48 was visualized using fluorescence in situ hybridization (FISH) in various rice varieties. Diversity was reflected by differences in the number of FISH signals. The number of loci detected was almost the same among the O. sativa subspecies japonica varieties, but differed significantly among the O. sativa subspecies indica varieties. The difference in the number of Os48 loci reflected differences in the chromosomal structure. In O. sativa, repeat sequences of 45S rDNA were also mapped to distal region(s) of the chromosome(s). Two-colored FISH of rDNA and Os48 revealed a common chromosomal structure within japonica varieties and indica varieties, but a distinctly different structure between japonica and indica varieties. The present study indicated that there was less cytological diversity among japonica varieties than among indica varieties. FISH results also allowed considerations of the domestication of cultivated rice O. sativa.