Effect of different plant growth regulators on callus induction in Catalpa bungei

The present study describes a reliable method for callus induction of Catalpabungei plant. Calli were in vitro initiated from leaves, stem and petiole segments using DKW basal media. The effect of combinations of BA (6-benzyl adenine) and NAA (α-naphthalene acetic acid) on callus induction was investigated. It was found that growth regulators and their concentrations have obvious effects on the callus induction, the increment of callus index and callus physical appearance. Moreover, callus was formed at different times among three kinds of explants that is, leaves, stem segment and petiole. The best callus induction capabilities were obtained with low levels of NAA in combinations with BA. However, supplemented medium with high concentrations of NAA led to relatively low callus frequency and the callus obtained turned to brown color. Generally, the highest frequencies of callus formation from leaves, stem and petiole explants were observed in the medium containing 0.05 mg l-1 of NAA and 5.0 mg l-1 of BA. However, petiole is the most potential explant for callus induction.   Key words: Catalpa bungei, tissue culture, plant growth regulators, callus.