Abstract
Dormant seeds of a rice variety, "Norin No.29", were treated with nitrogen mustatd, methyl-bis-(2-chloroethyl)-amine hydrochloride, its N-oxide derivative, methyl-bis-(2-chloroethyl)-amine-N-oxide hydrochlorid. e, or X-radiation. Nitrogen mustard presents the more toxic effect on germinating ability than it is the case with X-ray or N-oxide treatments (Fig. 1). A chi-square-analysis performed after a correction of discontinuity for 2 x 2 table gave the indication on mutagenic action of nitrogen mustard (Table 2). In comparison with ionizing radiation (X-rays or fa.st neutrons), nitrogen m'u:stard snows a significant difference in its ability to induce the mutations destroying chlorophyll formation of striata type (Table 3) . This suggests the possibility of+ controlling experimentaily the mutation process of rice. When dormant seeds of rice were exposed to N-oxide of nitrogen mustard, it showed the same tendency in sterility of the treated generation, production of seedling mutants and, the relative frequency of chlorophyll mutations, as that found in X-rayed material (Fig. 4 and Table 3). For seeds, N-oxide mus't, however, be considered as a less favourable mutagen than X-radiation, as clear froicn the relation between the toxic and mutagenic effects shown in Fig. 5.
