Ichizo NISHIYAMA
18, Hazamacho, Shugakuin, Sakyoku, Kyoto
In recent papers published in WIS, Nos. 49 and 50 (NISHIYAMA 1979a, b) abortive interspecific crosses in Aegilops, and Triticum were almost successfully interpreted by means of polar-nuclei activation (PNA) hypothesis.
The hypothesis is now applied to intergeneric hybridizations between Aegilops and Triticum which were previously made by many workers (Tables 1, 2). Eleven Aegilops and eight Triticum species are used in the present work. And their activating values, AV, (or response values, RV,) which are the same as those adopted in the previous interspecific crosses, are listed in the following:
The activation index of polar nuclei by a male nucleus in double fertilization is calculated from the formula AV/2RV(%) in each cross (Tables 1, 2). The index is closely related with development of hybrid seeds (Fig. 1). That is, in a total of 69 reciprocal crosses, AI less than 10 or 20%, 20-80%, 80-110%, and 110-250% generally indicate weakly developed seeds (W-type), barely viable; nearly normal seeds (N-type), viable; intermediate (Ps-type) between N- and E-type, partially viable; and empty, shrivelled seeds (E-type), inviable, respectively. However the hypothesis is hardly applicable to a few cases. In most of them crossing data were insufficient. Therefore, it has need to check them in detail.