Effect of dwarf genes on sizes and cellular characteristics of embryonic organs in near-isogenic lines of rice.

Abstract

The effect of dwarf genes of rice on the sizes of embryo and embryonic organs (coleoptile and radicle), was studied in relation to the length and number of cells of these organs. Nineteen kinds of dwarf near-isogenic lines which have the genetic background of the early variety 'Shiokari' were used. In most of the dwarf lines, sizes of either embryos or embryonic organs, or both were significantly smaller than those of their recurrent parent 'Shiokari'. But, sizes of embryo and embryonic organs of the d6-, d7-, dl2-, dl8k- and d47- lines were comparatively large. Cell numbers, especially those of radicles, in the dwarf lines whose embryonic organs were small, were reduced compared with those of 'Shiokari'. Furthermore, highly positive correlations were obtained between sizes of organs and cell numbers. In contrast, in most of the dwarf lines, cell lengths of coleoptile and radicle tended to be increased compared with those of 'Shiokari'. Correlations between sizes of the organs and cell lengths were nor significant or inexistent. Application of the principal component analysis enabled to clarify the features of dwarf lines on the basis of embryo and embryonic characters. From the results obtained, it was concluded that a considerable number of dwarf genes may manifest their effect on the embryonic characters, although the degree and pattern of their expression are different depending on the kinds of dwarf genes, and that the sizes of embryonic organs depend mainly upon the number of cells which constitute the organs.