2007 Volume 57 Issue 1 Pages 73-78
The National Institute of Genetics (NIG), Mishima, Japan, maintains 1,725 accessions of 20 wild species of the genus Oryza, which have been collected from tropical and subtropical areas all over the world and covering all species in the genus except for O. schlechteri Pilger. A core collection of 282 accessions was chosen to represent the genetic spectrum of the whole NIG collection. The genome sizes of 39 accessions of Oryza core collection, covering all 20 species and 9 genome types, were measured based on both flow cytometry and microscopic observation. Most accessions showed good correspondence with respect to genome size within the same species and genome type, but showed significant differences between different genome types. In contrast to other species, however, CC, CCDD and HHJJ species showed significant variation within the same genome type. The total somatic chromosome length and ploidy level were also investigated for several accessions, and they correlated well with the DNA content. In this study, a simple flow cytometric analysis provided reliable results for genome size evaluation, and in addition, the genome size of five species was newly determined. Thus the DNA content, which is the simplest reliable indicator of genome variability, should be a good means of monitoring for evaluation and identification of Oryza germplasm.
