Abstract: Tobacco seeds were used as explants to explore how to directly induce callus. The results showed that the callus induction of tobacco seeds was affected by different hormone ratios of 2,4-dichlorophe noxyacetic acid (2,4-D) and 6-benzylami nopurine (6-BA), and the combined use of hormones 2,4-D and 6-BA in the concentration range of 0.1-2.0 mg/L could induce callus, but different in size and quality. It was worth noting that when the seeds were cultured on the medium containing 1.0 mg/L 2,4-D + 1.0 mg/L 6-BA, callus was rapidly induced, but the callus mass was relatively loose. In comparison, the callus was more compact when the seeds were cultured on the medium containing 0.1 mg/L 2,4-D+1.0 mg/L 6-BA. Moreover, paraffin sections showed that the callus cells induced by the hormone combination of 1.0 mg/L 2,4-D+1.0 mg/L 6-BA were larger but irregularly arranged and most of them were non-embryonic cells. On the contrary, the callus cells induced by the hormone combination of 0.1 mg/L 2,4-D+1.0 mg/L 6-BA were small and regularly arranged, and most of them were embryonic cells. The results of this study provide new technical support for the induction of callus from tobacco seeds and facilitate the research on genetic transformation in tobacco.

Key words: tobacco, seed, callus induction, 2,4-D, 6-BA