Abstract:In order to get new informations on the interspecific relationship in the genus Secale and its phylogenetic relation to two related genera, Triticura and Aegilops, chloroplast(ct) DNAs were purified from five Secale species, and the restriction fragment patterns were analyzed by agarose gel electrophoresis of their BamHI, EcoRI, HindⅢ, KpnI, PstI, SalI, SmaI and XhoI digests The chloroplast genome sizes of all Secale species are very close to those of Triticura and Aegilops.The five Secale species did not show any great differences on the ctDNA restriction fragment patterns with each other. The ctDNAs of all four species, except S. silvestre, produced the identical patterns with the all enzymes, revealing no difference(?) among them (Fig. 1). The ctDNA of S. silvestre, when digested with BamHI, PstI and SinaI, showed one to three fragment differences from those of the other four species (Fig. 2, Fig. 3).The genetic distance between the chloroplast genomes of S. silvestre and the other four Secale species was compared with those observed chloroplast genomes known in Triticum and Aegilops (Fig. 4). From this figure, it is evident that the chloroplast genome diversification in Secale is much less. This fact suggests the recent origin of this genus, as previously indicated by the results of morphological, cytological, ecological and biochemical investigations.The genetic distances between the chloroplast genomes of S. cereale and selected Triticum and Aegilops species were calculated, based on which a dendrogram shown in Fig. 5 was drawn by cluster analysis. It clearly shows that the genus Secale is placed within the range of variation found in Triticum and Aegilops, so far as their chloroplast genomes are concerned.