Abstract
Cytogenetical studies of eight interspecific pentaploid hybrids among five Japanese and two Nepalese species of Agropyron are reported.
(1) The general characteristics of F1 hybrids were either intermediate between the parents or superior to those of the parent and (2) the hybrids were completely sterile.
From chromosome pairing of F1 hybrids, it was observed that the two genomes of three Japanese tetraploid species, Ag. ciliare, Ag. gmelini and Ag. yezoense, are identical with the corresponding two genomes of Japanese hexaploid species, Ag. humidum and Ag. tsukushiense. Two genomes of Nepalese tetraploid species, Ag. gmelini and Ag. semicostatum, are basically homologous with those found in Japanese species but some chromosomal differentiation must have taken place between Japanese and Nepalese genomes.
Summarizing the results obtained from tetraploid and hexaploid hybrids in the previous paper (Sakamoto and Muramatsu 1966) and the present results from pentaploid hybrids, genomic interrelationships in Japanese and Nepalese species were discussed. Genome formulae for three tetra- and two hexaploid Japanese species, and two tetraploid Nepalese species are given in Table 7.
Cytogenetical studies between Japanese and Nepalese species provide experimental evidences of genomic differentiation by geographical isolation, lasting a long time, of closely related species which are distributed in the same phyto-geographical area, the Sino-Japanese Region.
