Effects of repeated and alternate mutagenic method treatments with gamma-rays and ethyleneimine in successive generations on the genetic variability in rice (Studies on the utility of artificial mutations in plant breeding XIV.)

Abstract

In order to evaluate whether the recurrent mutagenic treatment in successive generations would be a useful tool for mutation breeding or not, seeds of a rice variety Gimbozu were subjected to repeated treatments with 10 and 20 kR ofL gamma-rays and 0.3 and (O. 5% solution of ethyleneimine (EI), and also to alternate treatments with lOkR gammarays and 0.3% EI, then seed fertility, chlorophyll mutation frequency and genetic variations of four agronomic traits were examined in the M1, M2 and M3 generation following the final treatment, respectively. In this report, the n th generation after m th treatment was represented by mRn. Seed fertlllty mR1:In the repeated treatments the mR1 seed fertility monotonously, decreased as the number of times of treatment advanced. This tendency was more remarkable in gamma-rays than in EI and at higher dosages than at lower dosages. In the alternate treatments, the change of the seed fertility clearly depended on the kind of mutagen used in the final treatment.