Induction of somatic embryogenesis in Tecomella undulata (Sm.) Seem using a pistillate explant

Abstract

Desert teak (Tecomella undulata (Sm.) Seem) a multipurpose ornamental tree native to the arid and semi-arid tropics has entered the endangered plant category mainly as a result of the species' ineffective seed reproduction system. The tree usually reproduces through a few root suckers in old stands. Conventional methods of plants multiplication could not offer a viable practice for its mass multiplication. Low adventitious rooting of the cuttings has been the principal cause of failure in its vegetative propagation. Hence, the present research was planned and conducted to evaluate the feasibility of somatic embryogenesis in this species, the pathway that bypasses the need for rooting stage by developing bipolar embryos. Ovary explant was cultured in modified Murashigue & Skoog (MS) medium supplemented with different auxins and cytokinins. The results showed α-naphthalene acetic acid (NAA) was superior in inducing embryogenic callus. NAA ranging 5.4-21.5 μM could induce the highest embryogenic calli which exhibited developing pro-embryogenic masses (PEM) and globular somatic embryos. The calli which were induced by the use of 2,4-dichlorophenoxyacetic acid (2,4-D) were poor in quality and showed no morphogenesis potency. Individual application of Thidiazuron (TDZ) and N6-benzyladenine (BA) induced good callogenesis at low concentrations but the calli were non-embryogenic with both. The proliferation of embryogenic calli was the best in a hormone-free medium. However, the media containing 40.5 and 54 μM NAA alone could induce somatic embryos along with callus proliferation. Low BA-contained medium (0.9-4.44 μM) led to recurrent somatic embryogenesis. Neither BA and GA3, nor the elevating sucrose concentration could cause further development and maturation of the somatic embryos induced during previous stages (callogenesis and callus proliferation). More research is required to optimize the maturation stage. The findings of the present study can be useful for future studies in the micropropagation of this recalcitrant specieslationships in Indian mustard under heat stress and the differential remobilization efficiencies in the advanced breeding lines.