An Optimized Protocol for Indirect Organogenesis from Root Explants of Agapanthus praecox subsp. orientalis ‘Big Blue’

Abstract

Agapanthus praecox has become a burgeoning variety in the flower market due to its high ornamental value with unique large blue-purple inflorescence. For rapid entering into the market, tissue culture technology or organogenesis has an attractive application over the conventional reproduction approach. In this study, a highly efficient protocol based on indirect organogenesis has been successfully established for A. praecox subsp. orientalis ‘Big Blue’. Two types of explants, root tips versus root segments, were compared for callus induction frequency in response to the induction culture media. The induction media contain Murashige and Skoog’s (MS) Basal Salt supplemented with various concentrations of picloram (PIC), 2,4-Dichlorophenoxyacetic acid (2,4-D), thidiazuron (TDZ), kinetin (KT) and naphthalene acetic acid (NAA). Of the two types of explants, root tips were found to be more effective for callus induction than root segments. Among the induction media tested, the highest callus induction rate (100.00%) was achieved when cultured on MS supplemented with 2.0 mg/L PIC, 1.5 mg/L KT and 0.1 mg/L NAA, which was probably accredited to higher endogenous phytohormone contents, especially of 3-indoleacetic (IAA). The optimal medium for callus proliferation was MS + 1.0 mg/L PIC + 1.0 mg/L 6-BA + 0.4 mg/L NAA, and the fresh weight increased by 72.74%. After being transferred onto the adventitious bud induction medium for 25 days, shoots were dedifferentiated from the surface of the flourishing callus, which then developed to the plantlet with roots in 90 days. The plantlets were transplanted in a greenhouse with a survival rate of 92.86%. This study innovatively established an indirect organogenesis tissue culture system of A. praecox with roots as explants, which provided a practical reference in its application.