Abstract
1. It has been assumed by Japanese rice breeders that it is very hard or almost impossible to obtain superior varieties from, highly sterile intersubspeciflc hybrid(japonica X indica) for their high sterility a, nd complicate segregating behaviors. 2. In this report the writers present one example of obtaining some fertile constant new lines of rice from such highly sterile intersubspecific hybrid by bulk method. 3. The F1 between Murasakimuyozetsuto-japonica type, liguleless, short-grained, non-glutinous, long-awned variety and Koiketsu mochi. indica type, long grained, glutinous, awnless, variety-showed highly vigorous growth habit, but set only 23% fertile grain. 4. The progenies of these F1 plants were reared in bulk ori the relatively small area less than 1/20 acre from F2 to F6 geheration. 5. 45 plants were selected in F6 population and tested their segregating behavior in F7 and F8 generations by pedigree culture. 6. Two families and two single lines were determined to be new constant lines and some characters of these lines such as culm length, ear length, panicle number per plant, fertility, length and breadth of unhulled grain, grain, shape, and endosperm character wre tabulated i.n table 1, 2 and 3, with those of their parents and' F1 plants. 7. The writers briefiy discussed on the problem of utilization of such sterile intersubspecific hybrid for future rice breeding.
