| Discussion and Conclusion An independent major effect of cytoplasm was not detected in our experiments. The NC-type interaction was the most frequent cases in which the Ni x Ci interactions showed a strong complementation between nuclear genes and cytoplasmic genome in the same species, on the other hand, Ni x Cj interactions showed a deleterious effect owing to inharmonious combination of nuclear gene with cytoplasm being different species origin. These results indicate that the most suitable nuclear genes had been selected intensively under the background of cytoplasmic genome of the species. Thus the interaction effect is so strong as inducing chromosomal structural changes in the 1R (the case II-(1)-(i)) and as establishing a new composit genome from D and R genomes through 2D-2R substitution (the case II-(1)-(iii)). We can draw a conclusion for triticale breeding strategy that the elimination of deleterious interactions mainly caused by the Ni x Cj is essential to select the most suitable nuclear genotype under a given cytoplasm of TC, which lead to build up a harmonious combination of nuclear and cytoplasmic genomes. As for the choice of cytoplasm for TC, the wheat cytoplasm might be the best and the caudata could be next canditate in addition to rye (Sasaki et al 1986). References Nakata N, Muraoka S, Yasumuro Y and Sasaki M (1986a) Japan J Breed 36 (Supple 1): 122-123 (Japanese) Nakata N, Yasumuro Y. Hamaoka H and Sasaki M (1986b) Japan J Breed 36 (Supple 2): 154-155 (Japanese) Nakata N, Yasumuro Y and Sasaki M (1986c) WIS 63: 39-41 Nakata N, Haba Y, Yasumuro Y and Sasaki M (1989) Japan J Breed 38: (Supple 2): 328-329 (Japanese) Sasaki M and Yasumuro Y (1974) Japan J Breed 24 (Supple 2): 104-105 (Japanese) Sasaki M, Yasumuro Y and Nakata N (1983). 6th Int Wheat Genet Symp 1179-1184 Sasaki M, Muraoka S, Nakata N and Yasumuro Y (1986) Proc Int Triticale Symp 436-441 Sasaki M, Nakata N and Yasumuro Y (1986) Japan J Breed 36 (Supple 2): 152-153 (Japanese) Tokiwa K, Yasumuro Y, Nakata N and Sasaki M (1986) Japan J Breed 36 (Supple 1): 328-329 (Japanese) Yasumuro Y, Sasaki M and Nakata N (1983) Proc 6th Int Wheat Genet Symp 1145-1148 Yasumuro Y, Nakata N, Hirao A and Sasaki M (1985) J Fac Agr, Tottori Univ 20: 1-7 Yasumuro Y, Nakata.N, Kawahito S and Sasaki M (1987) Japan J Breed 37: 397-404 Yasumuro Y, Nakata Y, Fukumoto A and Sasaki M (1988) Proc 7th Int Wheat Genet Symp 681-686 |
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