Abstract: Some factors which affect somatic embryogenesis, maintaining embryogenic callus and plant regeneration in Indica rice were investigated. It was found that 6% sucrose was favorable for inducing embryogenic callus (E-callus) and 3% sucrose was favorable for maintaining both E-callus and plant regeneration. Rice explant (especially young panicle) was very sensitive in this research. The explant (especially young panicle) formed neither E-callus nor non-embryogenic callus (NE-callus). but developed bud directly when the medium was 2,4-D free but with kinetin and NAA added. The explant formed NE-callus with no embryogenesis emerged when only 2,4-D and NAA was added. E-callus emerged from the explants in the medium with NAA free and when 2,4-D and kinetin was added. It was concluded that 2,4-D and kinetin were the basic factors for somatic embryogenesis in Indica rice and that the effect of NAA was not obvious. Rice explant (especially young panicle) was very sensitive to 2,4-D and kinetin. Low concentration of these two hormones (0.2 mg/1) was favorable for the development of the explants. The suitable concentration for 2,4-D and kinetin was 1 mg/l for somatic embryogenesis in Indica rice. Lower concentration of ABA (0.136 mg/l) in the subculture medium was favorable for E-callus maintain in subculture passage. The green meristemoid which coald not develop further to plantlet in regeneration culture was found to be a major obstacle in E-callus regeneration of subculture passage. The solution of this problem will increase to a great extent the plant regeneration of E-callus in Indica rice.

Key words: Somatic embryogenesis, Sucrose, Hormone, Indica rice