Variations in Callus Formation from Seeds in Japonica, Indica, their Hybrids, and Large Grain Varieties in Rice

Abstract

On the culture media differing in the concentration of mineral microelements (B, Mn, Zn, I, Mo, Cu and Co), japoleica varieties except for Somewake and Daikoku 1 generally exhibited high abilities of callus formation. Indica and large grain varieties (assumed to be javanica type), japonica-indica hybrids, however, showed relatively poor and varying abilities of callus formation, especially on the mediurm with reduced mineral microelements. These results suggest that there may be different requirerments for the concentration of mineral microelements in callus formation among ecospecies and hybrids. From a comparison between Murasaki-Daikoku and Daikoku 1 having the same d-1 gene, it was presumed that the d-1 gene would not directly affect the callus formation, and some background genes, i. e. the suppressors may relate with the depresssion of callus formation. Likewise, it appears that semidwarf genes in Dee-geo-woo-gen and Taichung native 1 would not also suppress the calus formation. Slight depressions in many japonica-indica hybrids and IR-8, therefore, were attributed to some background genes, i. e. the sup-pressors of callus formation other than the semi-dwarf genes. Such suppressors appeared to occur most frequently in inedica and large grain varieties. Variations on morphological appearance of callus in japoleica, indica, their hybrids and large grain varieties were observed. The calluses of japonica and large grain varieties tended to be friable, those of japonica-iledica hybrids compact and those of indica intermediate. Diversities from the expected callus formation, i. e normal plant growth, white hairs, root cluster, white region and root-like structures were liable to occur most frequently in the hybrids. Necrosis and/or brownish color of calius tissues were likely to occur in the varieties which showed the reduced ability of callus formation.