| Results and Discussion Transmission rates of the five umbellulata chromosomes through the female gamete in their monosomic addition type plants are given in Table 1. The transmission rates of the five chromosomes (average of the seven cytoplasms) ranged from 8.5% for Cu1 to 12.1% for Cu5 chromosome, but the difference among the chromosomes was not statistically significant. The transmission rates observed in the seven cytoplasms (average of the five chromosomes) ranged from 6.0% for the caudata cytoplasm to 15.1% for the squarrosa cytoplasm, but, again their difference was not statistically significant. This fact indicates no cytoplasms induced preferential transmission of the umbellulata chromosomes. Pollen and selfed seed fertilities of the monosomic and disomic addition lines are shown in Table 2, in comparison to those of the normal alloplasmic lines of CS as the control. The caudata and timopheevi cytoplasms caused complete male sterility in CS, as noticed earlier (TSUNEWAKI et al. 1976), while the addition of Cu1 chromosome resulted in remarkable restoration of the fertilities in both cytoplasms. The umbellulata cytoplasm caused partial reduction of seed fertility, that was greatly recovered by the same chromosome. Therefore, it can be concluded that the Cu1 chromosome carries a fertility-restoring gene(s) for the above three male sterile cytoplasms. Degree of the restoration was higher in the monosomic than in the disomic addition in all three cases, indicating that a single dose of the gene is as effective as its double dose in fertility restoration. If this gene could be successfully transferred into wheat genome, it will become valuable for hybrid wheat breeding. All Cu chromosomes tended to reduce fertilities when added in the double dose to fertile alloplasmic lines. Literature Cited KIMBER, G. 1967 The addition of the chromosomes of Aegilops umbellulata to Triticum aestivum (var. Chinese Spring). Genet. Res. 9: 111-114 TSUNEWAKI, K. and T. ENDO 1973 Genetic relatedness among five cytoplasms in Triticum and Aegilops. Proc. IV Int. Wheat Genet. Symp.: 391-397 TSUNEWAKI, K., Y. MUKAI, T. Ryu ENDO, S. TSUJI and M. MURATA 1976 Genetic diversity of the cytoplasm in Triticum and Aegilops. V. Classification of 23 cytoplasms into eight plasma types. Japan. J. Genet. 51: 175-191 |
| <-- Back |