In Vitro Regeneration of Coral Tree from Three Different Explants Using Thidiazuron

The coral tree (Erythrina variegate) is a multipurpose horticultural plant with a plethora of medicinally important alkaloids. Regeneration via tissue culture can provide an efficient alternative to seed-grown plantlets and reduce the cost of the plant significantly. Thidiazuron (TDZ) is an efficient plant growth regulator and is effective in numerous species. However, the response to it varies with the type and position of the tissue on the plantlet treated. This study was carried out to ascertain the best tissue types for micropropagation of the coral tree using TDZ. Three tissue types (shoot tip, nodal, and hypocotyl), originating from different strata of the plantlet were evaluated. Adventitious shoots were observed in all three explants at the tested concentrations. However the quality and the shoot number varied significantly with the type of explant. Explants with a meristematic zone (shoot tip and nodal) were more responsive to the treatment compared with hypocotyl tissue lacking preexisting meristem. Nodal explants produced the maximum number of shoots (about eight) per explant after 4 weeks of culture, whereas shoot tips produced about only five shoots per explant at an equimolar concentration (1.5 mu.m). Approximately three shoots were observed in hypocotyl explants. Moreover, growth and rooting of the regenerated shoots was influenced by the origin of the explants. The molecular characterization of the regenerants using intersimple sequence repeat (ISSR) markers revealed genetic homogeneity among regenerants. An efficient micropropagation method for the coral tree is described.