Identification of Dwarf Genes and Their Character Expression in the Isogenic Background

Abstract

The genic identification of dwarfness was conducted by crossings between different dwarf lines. The equivalence of the dwarf gene loci was shown as follows; d8=d11=d14 and dl5=dl6(d10). Non-allelic relations were recognized in 60 combinations of dwarf genes. In addition, unknown genotypes of ten dwarf lines were determined by test crossings. Further, a mutant line induced by gamma-irradiation was governed by d42 which belongs to the second linkage group. Twenty one kinds of near-isogenic lines were produced in successive backcrossings by using the leading variety in Hokkaido, Shiokari, as a recurrent parent. It was shown that the dwarf gehes insert their effects, to various characters and then, the traits of the 21 near-isogenic lines were compared with those of Shiokari. A trial classification was made depending on the distribution patterns of the elongated internodes allotting 21 dwarf near-isogenic lines to nine groups. Pleiotropic actions of the dwarf genes were prominient in grain and seedling characters. These dwarf genes were classified into 13 groups depending on grain length, grain width, grain shape index (length/width) and grain size index (length×width). Increment of grain length or width was recognized in several dwarf lines which belong to the semi-dwarf, while short round grains were produced in some lines which indicated the specific internode pattern. Thus, it is important in rice genetics and breeding to elucidate the genic pathway on morphogenesis and to estimate the genetic composition for the ideal plant type in the breeding of lodging resistance and high yielding capacity.