Chromosomal Localization Of RDNA In Species Of Subgenus Strobus (Pinus)

Pines have large genomes (>20000) composed of 90% highly repetitive DNA. The genus Pinus is divided into two subgenera: Strobus (Haploxylon) and Pinus (Diploxylon). Early investigations have shown that members of the subgenus Strobus generally have lager genomes than those of the subgenus Pinus. The genome structure of pines, however, is still poorly understood, as is the differentiation between the two subgenera at the genome level. Characterized as multigene families, the tandem repeated genes encoding 18S-25S and 5S ribosomal RNA are major components of the repetitive DNA in plant genome. Fluorescence in situ hybridization (FISH) has proved to be useful tool for chromosomal localization of 18S-25S rDNA and 5S rDNA. Although there have been a few reports available on rDNA FISH in Pinus species, almost all of them are on subgenus Pinus. There is virtually no report till today on the rDNA FISH characterization in subgenus Strobus. In this study, the 18S-25S rDNA and 5S rDNA were localized simultaneously on metaphase chromosomes of five species of subgenus Strobus, P. bungeana, P. koraiensis, P. armandii, P. wallichiana, and P. strobus by FISH. Combined with previous rDNA FISH reports on those species of subgenus Pinus, the comparison of the 18S-25S rDNA and 5S rDNA loci number and localization pattern between the two subgenera can be made, which is necessary to generalize the rDNA loci distribution pattern in Pinus. This study aimed to explore the genome organization and structure of Pinus. The main results and conclusions are followings:1. The karyotype analysis with 18S-25S rDNA and 5S rDNA markers...