| Considerations on the involvements of genetical differences
with callus formation in wheat H. OGURA Laboratory of Genetics, Faculty of Agriculture, Kyoto University Kyoto 606, Japan Tissue culture of wheat and the related genera is not so advanced as compared with that of dicotyledonous plants and several monocotyledons. The conditions for callus initiation or subculturing have been reported by several workers (GAMBORG and EVELEIGH 1968; TRIONE et al. 1968; SHIMADA et al. 1969; UTSUMI 1969). However, there have been few reports indicating the redifferentiation conditions from wheat calluses. OUYANG et al. (1973) reported a successful haploid production from anther-derived calluses in hybrids of common wheat. In barley, haploid production by both anther and ovary culture method has been reproted (KASHA and KAO 1970; CLAPHAM 1973). Nevertheless, the most important step, i.e., redifferentiation conditions for practical plant breeding is still in question, in wheat and the related species. Probably due to various difficulties in wheat tissue culture, several studies of the other direction has been elaborated recently concerning the influence of genetic factors on callus formation. The genetic role of individual chromosomes or chromosome arms in callus formation has been reported, in anther culture of A genome aneuploids of common wheat (SHIMADA and MAKINO 1975). Cytoplasm effects on callus induction from wheat anthers have been reported, using the cytoplasm substitution lines of Chinese Spring wheat (OGURA and TSUNEWAKI 1974). These attempts may be useful to know the genetical factors involved in callus formation. Since wheat and a related genus Aegilops contain many species, their phylogenetical relationships have been revealed, and many kinds of hybrids, some sets of aneuploid series in Chinese Spring wheat and the cytoplasm substitution lines are available, wheat and the related genera seem to be one of the most suitable materials to investigate the genetical effects on callus formation. However, few studies have been known, on the influence of genome constitution on callus formation. In order to know which genome gives the highest callus formation, in response to the same auxin concentration, the writer exmained the degree of callus formation from the seedling roots and the anthers of several wheat, Aegilops and rye species. The protocols of the experiments are as follows: Sterilized soaked seeds of several wheat, Aegilops and rye species were placed on agar slant medium aseptically and cultured in vitro on an RM-1964 medium supplemented with 0.1 mg/l of 2,4-D, for the 2,4-D concentration applied was reported to be a threshold concentration of callus initiation from the seedling roots of wheat and Aegilops (UTSUMI 1969) and the validity of his result was ascertained before the present experiment. Anthers of these species and varieties were also inoculated on an RM-1964 medium containing 3 mg/l of 2,4-D, as described by OGURA and TSUNEWAKI (1974). The seeds were incubated in the dark and the anthers under constant fluorescent illumination of about 1,000 luxes, both were cultured with the constant temperature of 25+ or -1C. The pH of the media was adjusted to 5.8+ or -0.1 before autoclaving. Callus formation from germinated seedling roots was observed about 4 weeks after the initiation of the experiment. In the case of anther culture, callus formation was firstly observed about 6 weeks. The preliminary results of callus formation from seeds and anthers are presented in Table 1. The data on callus formation from seedling roots of wheat can roughly be interpreted that the feasibility of callus formation is in the following order; diploid, tetraploid and hexaploid. Callus formation from anthers was observed only in T. durum cv. reichenbachii and S. cereale cv. Imperial, the calluses of the latter being shown in Fig. 1. A marked effect on growth of anther-derived callus is seen in this figure. It seems that there are no relationships or parallelism between the data of seedling roots and the anthers. Supposing that some genetic factors are closely related to callus formation, the callus formation results from seedling roots, anthers or other parts of wheat plants should parallel. The present preliminary results are not clear-cut and of small scale. However, tissue culture studies of this direction should be advanced further, since genome level studies on callus formation in wheat may be more advantageous than other materials. (Recieved May 1. 1976) |