放射線處理한 벼 M₁이삭의 變異 sector에 關한 硏究

The Size of Mutated Sector in the M₁Panicle after Irradiation of Dormant Rice Seeds

When mature seeds of cereal crops are treated with mutagenes, there occurs frequently the deficit of homo-recessive mutant in the M₁ generation, thus the segregation of recessiveness deviating from the expected ratio of 0.25. This has been considered caused partly by the function of the mutated gene and partly by the chimaeric nature of the M₁ panicle. Studies on the M₂ segregation inevitably led to the assumption of the size of mutated sector in the M₁ panicle and to the speculation on the number of initial cells (in the seed embryo) which would later form the sporogenous tissue of the M₁ panicle. So far the views concerning the initial cell have been conflicting and controvertial. X-rayed rice seeds were sown directly in the pots and all the tillers including the lower ones were induced to full growth to examine whether there exists any difference in the segregation ratio among the tillers. No definite tendencies or regularities in the segregation ratio among the tillers were observed. If the number of initial cells varies with the order of tiller emergence, i.e., main culm having several and the upper tillers having only one cell, there would be certain definite tendency in the segregation ratio among the tillers, with the upper tillers approaching the expected ratio, which was not proved in the present experiment. As it is assumed that the mutated cell, mutated gamete, and homo-recessive mutant might be affected by many factors, it does’nt seem to be correct to speculate the sector size in the M₁ panicle and the number of initial cells in the seed embryo simply by the M₂ sgregation ratio.