| The data are simply summarized in a diagramatic illustration showing
the frequency distribution of the activation indices of the 58 crosses (Fig.
1). It is also indicated that the grouping of activation index series,
15-30, 30-60, 75-95 and 100-160% closely agrees with the grouping of W-,
N-, Ps- and E- types, respectively, including mean percentages of the seed
germination. It is of interest that the germination of Ps-type seeds greatly
varied from 7 to 100% though 57% in an average. Such a variability appears
to be attributed to the degree of abnormal seed development where environmental
conditions or modified factors if present might be more effective in the
other seed types. As discussed at length the polar-nuclei activation hypothesis is very well applicable for understanding of seed failure in interspecific crosses of Triticum. The supplement of some appropriate crossing data would assist the establishing of a more perfect cross-incompatibility system in the genus Triticum. Literature Cited DHALIWAL, H.S., 1977. Origin of Triticum monococcum L. WIS 44: 14-17. KATAYAMA, Y. 1933. Crossing experiments in certain cereals with special reference to different compatibility between the reciprocal crosses. Memoirs Coll. Agr., Kyoto Imp. Univ. No. 27: 1-75. KIHARA, H., Sh. WAKAKUWA and I. NISHIYAMA, 1929. Notes on species hybrids of Triticum (Japanese with English summary). Japan. J. Genetics 5: 81-87 LILIENFELD, F. und H. KIHARA, 1934. Triticum Timopheevi Zhuk. Cytologia 6: 87-122. NISHIYAMA, I. and T. YABUNO, 1978. Causal relationships between the polar nuclei in double fertilization and interspecific cross-incompatibility in Avena. Cytologia 43: 453-466. NISHIYAMA, I. and T. YABUNO, 1979. Triple fusion of the primary endosperm nucleus as a cause of interspecific cross-incompatibility in Avena. Euphytica 28 (in press). WAKAKUWA, Sh., 1934, Embryological studies on the different seed-development in reciprocal inter-specific crosses of wheat Japan. J. Bot. 7: 151-185. |
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