Adventitious Bud Formation Promoted by Auxin Treatment in Explants from the Apical Portion of Leaves in Begonia×tuberhybrida

Abstract

An in vivo method to promote adventitious bud formation in leaf apex explants of Begonia×tuberhybrida was developed based on exogenous treatment with BA, IAA and NAA. Endogenous IAA concentrations of the leaf blade were highest in the apical portion, followed by the middle and basal portions. Treatment with 0.5 mg L⁻¹ BA increased the percentage of adventitious bud formation to 15% from 0% at 0 mg L⁻¹ BA, but treatment with BA at concentrations higher than 0.5 mg L⁻¹ had no additional promotive effect. Adventitious bud formation was increased to 53% by treatment with 0.1 mg L⁻¹ IAA and 0.5 mg L⁻¹ BA, and inhibited by 1.0 and 5.0 mg L⁻¹ IAA. The optimal duration of treatment with 0.1 mg L⁻¹ IAA was 2–8 days after embedding. No explants formed adventitious buds when treated with fresh 0.1 mg L⁻¹ IAA at 2-day intervals until 16 days after initial embedding. Similar responses were observed in explants treated with 0.1 mg L⁻¹ NAA. These results suggested that temporary IAA treatment at 0.1 mg L⁻¹ during the initial period of embedding is an efficient in vivo method to induce adventitious bud formation in leaf apex explants in B.×tuberhybrida.