| In two crosses, T. boeoticum x T. urartu and T. monococcum
x T. urartu, having T. urartu as the male parent, seeds produced
were small and plumped. The germination rate of those seeds were 52.7% and
85.5%, respectively. Chlorosis was observed in these seedlings and in many
cases they died soon. In the crosses, Emmer x T. urartu and Timopheevi x T. urartu, having T. urartu as the male parent, the germination rate of these seeds were 51.8% and 61.6%, respectively. Chlorosis was also observed in these cross combinations, but almost all plants reached to the mature stage. Chromosome associations observed at MI of PMCs of F1 hybrids of Emmer x T. urartu and Timopheevi x T. urartu are listed in Table 3. Cytogenetical results obtained in this experiment indicate that the genome of T. urartu is homologous with the A-genome of T. boeoticum, which is also found in the Emmer and Timopheevi wheats. Therefore, T. urartu is not the donor of the B-genome as well as the G-genome. Also, when T. urartu was used for the male parent to the Einkorn group, the germination rate of those hybrids was high, but all plants could not get mature. Chlorosis was observed in all plants. On the other hand, when T. urartu was used for the female parent to the Einkorn group, the germination rate was extremely low. The F1 hybrids between T. urartu and T. boeoticum were highly sterile. There clearly exists a reproductive barrier between them. The backcross experiment does not support the hypothesis of JOHNSON et al.(1976) and DHALIWAL (1977) that the cytoplasm of T. urartu in combination with the genome of T. boeoticum inhibits the development of viable seeds. Literature Cited CHAPMAN, V., T.E. MILLER and R. RILEY 1976. Equivalence of the A genome of bread wheat and that of Triticum urartu. Genet. Res. Camb. 27: 69-76 DHALIWAL, H.S.1977. Basis of difference between reciplocal crosses involving Triticum boeoticum and T. urartu. Theor. Appl. Genet. 49: 283-286 DVORAK, J. 1976. The relationship between the genome of Triticum urartu and the A and B genomes of Triticum aestivum. Can. J. Genet. Cytol. 18: 371-377 GERLACH, W.L. 1977. N-banded karyotype of wheat species. Chromosoma Berl. 62: 49-56. JOHNSON, B.L. 1975. Identification of the apparent B genome donor of wheat. Can. J. Genet. Cytol. 17: 21-39 JOHNSON, B.L. and H.S. DHALIWAL 1976. Reproductive isolation of Triticum boeoticum and Triticum urartu and the origin of the tetraploid wheats. Amer.J. Bot. 63: 1088-1094 |
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