Abstract
Sodium azide-induced damage in M1 generation and mutation in M2 Were analized in Japonica rice variety. In treatments of dormant seeds, germination rate and seedling griwtg were reduced in proportion to both the increase of sodium azide concentration and the prolongation of treatment time. Furthermore, sodium azide delayed the seed germination. When the extent of growth reduction and of the delay of germination were plotted against the "dose" (ConcentrationXSoaking duration) man entne lot of treat ments, these indices each fltted into a single "dose"-response curve. The higrhest frequency of chlorophyll mutation was 11.1 per cent per M1 panicle and 1.22 per cent per M2 seedling. With regard to mutation in agronomic characters, Iate heading, short culm, dwarf, and sterility appeared more frequently. In presoaked seeds, chlorophyll mutation was induced more frequently in the 6, 48 and 54 hour-presoaked seeds than 12 to 42 hour-presoaked seeds. However, M1 seed fertility remained almost the same level (about 90 per cent) during this presoaking period. From these results, it appears that sodium azide when applied at the DNA synthesis stage of the first cell division of germinating process, is more effective in the induction of mutation. It also appears that the mutagenic action of sodium azide can be affected by cellular metabolism during germination.
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