Studies on mutations induced by radiations and chemicals. III. Variations of quantitative characteristics in M6 generation.

Rice seeds were treated with X-rays, thermal neutron or diepoxybutane at BNL in 1957. The progeny populations were cultured in every year without artiflcial selection until the M6 genetation. Variations of several quantitative characteristics related to grain yield were compared with those of controls (original variety) in M6 under randomized block design. The significant differences were found in mean values of the panicle weight per stock, weight of a panicle and panicle length among the treated and between treated and controls. These may be caused by natural selections during M2 - M6. Also were found some differences among treated and between treated and controls in variance of inter individuals of each population in the wgt, of paniclesper stock, number of panicles and stem length. The wgt of panicles per stock in X-rayed and diepoxybutane treated plots were enlarged in meanvalues and increased in inter-individual variances in M6, indicating that there are some possibilities. of obtaining high yield strains from these treated populations by selection. However, there was no difierence in mean values or variances between progeny derived from M2 which segregated chlorophyll mutations in M2 and that from M2 in which no chlorophyll mutations segregated. The prediction of frequencies of polygene mutations in progenies by that of chlorophyll mutations in M2 seems improbable, aithough it was reported that the frequencies of morphological mutations in M2 adults could be predicted by that of chlorophyll mutations in M2 nurseries.