Young panicles from 11 rice varieties, Zhenshan 97A (WA type cytoplasmic male-sterile (CMS) line, indica), Zhenshan 97B (WA type maintainer line, indica), IR24, IR26, Taiyin 1, Minghui 63 (WA type restorer line, indica), Hongyuan A (HL type CMS line, indica), Baoyuan A (BT type CMS line, indica), Nanguangzhan (genic male-sterile (GMS) line, indica), Nongken 58s (photoperiod-sensitive genic male-sterile rice (PGMR), japonica) and W6154s (thermosensitive genic male-sterile rice (TGMR), indica), were cultured on different media. Factors influencing callus induction and plant regeneration of young panicle were examined. The main results were as follows: All the explants of the 11 rice varieties cultured on the media containing 2,4-D could produce calli. The callus could be induced and the plantlet could be regenerated on one step culture (without transferring) in young panicle culture of japonica variety using 2,4-D free medium containing NAA 2 mg/L and KT 2 mg/L; while the young panicles from indica varieties showed direct budding and resulting in plantlet formation. This indicated 2,4-D played an important role in callus induction. KT inhibited callus induction obviously, but accelerated plant regeneration of young panicles in indica rice, and had fewer effects on plant regeneration of japonica rice. NAA 0.2 mg/L and ABA 0.1 mg/L, mannitol 2% and Vitamin B1 1 mg/L had some effects on callus induction and differentiation and accelerated callus growth and raised plant regeneration frequency. Inositol was not essential in media, adding it was to accelerate the growth of callus. The difference between male-sterile and fertile varieties on callus induction and plant regeneration frequency was not significant, even the plant regeneration frequency of some male-sterile varieties were higher than that of fertile varieties, viz. CMS had fewer effects on callus induction and plant regeneration frequency.

Key words: callus induction, in vitro culture, indica, japonica, Oryza sativa L., plant regeneration