| Seed shriveling caused by a gametocidal gene, Gcl H. TSUJIMOTO and K. TSUNEWAKI Lab. of Genetics, Fac. of Agriculture, Kyoto University, Kyoto 606, Japan A gametocidal gene kills its non-carrier female and male gametes which are produced by the hetero- or hemizygous plants for it. Such genes are known in several species of Aegilops having C, S or S1 genome. We introduced a gametocidal gene, Gc1, of Ae. speltoides into a common wheat, Triticum aestivum cv. Chinese Spring (CS), by backcross method (TSUJIMOTO & TSUNEWAKI 1984). The isogenic line of CS for Gc1 gene is not different in morphology from normal CS. This line, however, causes seed shriveling when it is crossed as male to some common wheat cultivars. No shriveled seeds are produced by the reciprocal cross, the isogenic line (female) x those cultivars (Fig. 1), or the cross between those cultivars and a carrier of other gametocidal genes as male. Occurrence of seed shriveling is greatly affected by the temperature about eight hours after the pollination. When temperature is lower than 17C, more than 75% of the seeds become shriveled, whereas it is higher than 22C, no seed shriveling occurs. Although most shriveled seeds do not germinate, some of them do germinate, giving rise to mutants with speltoid or half-awned spikes, or showing chlorosis in their leaves. Frequency of the mutants is higher in the F1 lines which show lower germination rate (Table 1). No chimeric plants which havd different types of spikes are obtained except a single plant. This fact indicates that the mutation occurs before the first zygotic cell division. Seed shriveling and mutation observed in the F1 plants are two symptoms of "hybrid dysgenesis" caused by the gametocidal gene in wheat. |