Enhancing Somatic Embryogenesis in Dendrobium discolor Lindl. through Optimized PGRs Addition: A Promising Approach for Mass Propagation

Somatic embryogenesis in orchids offers a fast and reliable way to grow new plants from cells, aiding propagation efforts. The present study evaluated the technique for SE production and plantlet regeneration of Dendrobium discolor. Thin cell layer (TCL) explants were treated with concentrations of 2.4-Dichlorophenoxyacetic acid (2.4-D) (1;2;3; and 4 mg/L) to induce callus formation of Den. discolor. The application of 2 mg/L 2.4-D effectively promoted the callus emergence rate of Den. discolor. During the proliferation and regeneration stage of SE, the induction of shoots and roots depends on a synergistic combination of auxin and cytokinin PGRs. Two-week-old culture of primary callus were transferred to proliferation media (1/2 MS) supplemented with thidiazuron (TDZ) and 1-Naphthaleneacetic acid (NAA) (0 mg/L TDZ+0 mg/L NAA, 0.15 mg/L TDZ+0.05 mg/L NAA, 0.3 mg/L TDZ+0.1 mg/L NAA, 0.6 mg/L TDZ+0.2 mg/L NAA, 0.9 mg/L TDZ+0.3 mg/L NAA). The best response observed was 0.6% coleoptilar embryo production from TCL’s embryonic callus on 0.15 mg/L TDZ+0.05 mg/L NAA. Plantlet was developed from SE in regeneration media (1/2 MS) supplemented with various combinations of 6-Benzylaminopurine (BAP) and NAA (0 mg/L BAP+0 mg/L NAA, 0.5 mg/L BAP+0.5 mg/L NAA, 1 mg/L BAP+1 mg/L NAA, 1.5 mg/L BAP+1, 5 mg/L NAA, 2 mg/L BAP + 2 mg/L NAA). The best response for plantlet regeneration was observed on 0.5 mg/L BAP+0.5 mg/L NAA. This study showed that the TCL embryogenesis protocol is promising for in vitro multiplication of Den. discolor.