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). Twocolored 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.

Comparative Analyses in<b><i> Lotus</i></b>: The Cytogenetic Map of <b><i>Lotus uliginosus </i></b>Schkuhr

“…Although FISH has revealed intraspecific variation in the number and position of rDNA sites in plants, these changes generally occurred among different accessions and were conserved within an accession, as described for rice [Nakayama, 2005] and for most common bean accessions [Pedrosa-Harand et al, 2006]. In this later species, however, one wild accession presented a heteromorphism for the 45S rDNA similar to that observed in the present study.…”

Genetic variation in the chloroplast genome suggests multiple domestication of cultivated Asian rice (Oryza sativa L.)

“…The origin of temperate japonica varieties from tropical japonicas has also been proposed from other studies (Garris et al 2005;Londo et al 2006). Other explanations, such as independent origins of temperate and tropical japonicas from as yet unidentified O. rufipogon with Type F cp, may be less likely because of the relative lack of diversity in japonica varieties compared with indica varieties (Ishii et al 1988;Kadowaki et al 1988;Nakayama 2005). Cheng et al (2002) reported that the 2 ecotypes of O. sativa, indica and japonica, are distinguishable, almost exclusively, by the presence or absence of p-SINE1 members, which are nuclear genome sequences.…”