Genetical studies on heading rice plants : II. Gene-analysis on heading of some early heading mutants induced by X-ray

Abstract

Following the previous report (MATSUO and NAKAJIMA 1960), the authors made a study in the gene-analysis of some early heading mutants induced from Norin-No. 8 by X-ray. The materials were as follows: M₁ strain: 1O days earlier than the original variety under the natural condition, but 7 days later under the high temperatire and short day condition. M₂ strain: 40 days earlier; the non-sensible strain of the photoperiodic response on heading, and viridies type. M₄ strain: 20days earlier; the strain decreasing of the photoperiodic sensibility, and the short-culm and stiff-stow type. The F₂ segregations for heading time among the hybrids between original variety and each strain, and between each other strain were investigated. The results were as follows: (1) The earliness of these strains were attributable to the recessive mutation of one gene related to heading time in rice plants (cf. fig. 1 and table 1). (2) These gense which were related to the earliness of each strain were independent from each other (cf. fig. 2 and table 2). Therefore, it was suggested that there were 4 major genes for heading, especially, for photoperiodic sensibility, to say the lease of it. (3) It was evident that the gene related to the photoperiodic sensiblity in M₁ strain had also connection with the minimum heading duaration. The authors suggested that this fact was very important to genetical study of heading in rice plants. (4) Some changes of morphological or physiological characters of these strains, i.e. the sterility of M₂ strain under the short day condition, the stiff-strow type of M₄ strain, were also attributable to the recessive mutation of one gene, and these genes were independent of the genes related to heading time (tables 3, 4).