Studies on the Utility of Artificial Mutations in Plant Breedin : IX. Effects of Washing Temperature after EMS Soaking of Rice Seeds on Mutation Induction

Abstract

In order to determine the influence of washing temperature on mutagenic effects of EMS remaining in seeds after soaking-treatment, dry seeds of two rlce strains, cultivar Gimbozu and an albina-segregating strain derived from Gimbozu, Ivere soaked in EMS solution (0.8% or 0.9%) under four diffent temperatures (0'C-30'C) and washed with water at four degrees of temperature (10'C-40'C). As to Girnbozu, considerable infiuences of the temperature during washing were observed on injury of M₁ characters, such as germination rate, seedling height and seed fertility, and on frequency of mutations in chlorophyll, heading date and culm length in M₂ generation. Mutatino frequency in heading date and culm length was expressed with the percentage of M₂ plants falling outside the variation range of original variety defined with a certain confidence limit (cti), that is, with the percentage of those in the critical region of a=0.01. These effects remarkably depended not only upon washing temperature but also upon soaking temperature. As to the albina-segregating strain also, the same mutagenic effects of washing temperature as seen in Gimbozu were recognized on the frequency of somatic chlorophyll mutations induced on M1 plants. This suggests that somatic chlorophyll mutations are available for early determination of the mutagenic effect of some mutagen.