Abstract
Cytological and morphological studies were made on the F1 plants (OF1141 and OF1139) obtained from the crosses Oryza minuta Presl. (Y22, 2n=48, BBCC)×O. ridleyi Hook. (W0001, 2n=48) and O. officinalis Wall. (W1281, 2n=24, CC)×O. ridleyi. Morphological characteristics of both the F1 plants resembled their female parents, O. minuta and O. officinalis, more closely than O. ridleyi. Moreover, the F1 plants were especially characterized by producing runners. In somatic cells of the F1 plants, 2n=48 chromosomes for the former and 2n=36 for the latter were counted. At meiotic division of the former cross-combination, most chromosomes failed to make pairing. These results suggest that the genome constitutions of O. ridleyi differed from the genomes of O. minuta, B and C.
