| Results from the study of interactions involving T. durum or T.
aestivum genomes and cytoplasms of related Triticum and Aegilops
species can be summarized briefly (Maan, 1978) : 1) All diploid Triticum
and Aegilops species having cytogenetically distinct genomes also
have different cytoplasms, 2) certain polyploid species are cytoplasmically
similar to only one of their putative diploid progenitors ; this observation
indicates that this particular diploid contributed cytoplasm as well as
the nuclear genome to that polyploid. These results lead to the following
conclusions : 1. Cytyplasmic and genomic differences existed among the diploid species of Triticum and related general before some of them participated in the origin of polyploids. 2. Cytoplasmic and genomic similarities have persisted between related polyploids and their respective cytoplasm donor species. Cytoplasmic and genomic changes have been slow since the origin of the polyploids. Perhaps, cytoplasmic mutations were matched by compensating nuclear gene mutations and vice versa. The residual genetic similarities indicate that the cytoplasmic and nuclear genetic systems have been equally table during the evolution of related diploid and polyploid species, and major modifications may have occurred in the genomes contributed by the male progenitors, and 3. Nucleocytoplasmic compatibility may have been an important factor determining the success of the natural amphidiploids and polyploidy may be an evolutionary bypass to interspecific sterility due to cytoplasmic and genomic differences among the diploid species. Literature Cited BAHL, P.N, and S.S. MAAN. 1973. Crop Sci. 13: 317-320. KIHARA, H. 1951. Cytologia 16: 177-193. KIHARA, H. 1951 1959. Proc, 10th Int. Congr. Genet. 1: 142-171. KIHARA, H. 1951 1963. Seiken Zhio 15: 13-23. LAMPRECHT. H. 1945. Agri. Hortique Genetics Bot. 111: 45-60 MAAN, S.S. 1973. Proc. 4th. Int. Wheat Genet. Symp., Univ. Missouri, Columbia : 367-374. MAAN, S.S. 1975. pp 255-281. In M.K. Wali (ed.). Prairie : A Multiple view. Univ. N.D. Press, Grand Forks, ND. MAAN, S.S. 1976. Crop Sci. 16: 757-761. MAAN, S.S. 1977a. Euphytica 26: 601-613. MAAN, S.S. 1977b. Proc. 8th Eucarpia Congress, Madrid. Spain, pp 201-214. MAAN, S.S.1978. Proc. 5th Int. Wheat Genet. Symp. IARI. New Delhi : 232-260. MAAN, S.S. and K.A. LUCKEN. 1970. Euphytica, 18: 498-505. MAAN, S.S. and K.A. LUCKEN. 1971. J. Hered. 62: 352-355. MAAN, S.S. and K.A. LUCKEN. 1972. Crop Sci. 12: 360-364. TSUNEWAKI, K., Y. MUKAI, T. ENDO, S. TSUJI and M. MURATA. 1976. Japan J. Genet. 51: 175- 196. TSUNEWAKI, K., Y. MUKAI, T. and T.R. Endo. 1978. Proc. 5th Int. Wheat Genet. Symp., IARI. New Delhi: 261-272. |
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