Effects of inorganic salts concentration and alternative plant growth regulators on the in vitro organogenesis of a new hybrid Cymbidium

Hybrid Cymbidium is an important ornamental resource as an orchid pot plant and in cut flower markets, so any protocol that can lead to its improved productivity in vitro is always welcome. Based on a cultivar “Memoria Amelia Earhart” that has not been yet studied, the effects on in vitro organogenesis in response to diluted Murashige and Skoog (MS) medium inorganics and plant growth regulators [PGRs: Epin-Extra® (24-epibrassinolide, 24-EpiB), Ribav-Extra® (RE), kinetin (KIN), thidiazuron (TDZ), 6-benzyladenine (BA), and indole-3-acetic acid (IAA)], either alone or as combinations between cytokinins and IAA, were assessed. Whole protocorm-like bodies (PLBs) served as the initial explant source. While full-strength MS medium benefited shoot growth, half-strength MS was optimal for rooting and PLB formation. The optimum concentrations of 24-EpiB were 104 % and 105 % for shoot growth and 106 % for PLB multiplication, and the maximum shoot growth was induced by RE at 104 % and BA at 4.4 μM or 13.3 μM. The simultaneous application of a cytokinin and IAA in MS had the greatest impact on PLB-related parameters. The number of PLBs per explant was improved by 11.6 μM KIN and 2.9 μM IAA, while 0.5 μM KIN and 2.9 μM IAA improved PLB size. The number of regenerated shoots was maximum in MS medium supplemented with 109 μM TDZ and 2.9 μM IAA, whereas the longest shoots formed in MS medium supplemented with 2.2 μM BA and 2.9 μM IAA. Using well-explored and unexplored PGRs, we devised an effective in vitro PLB-to-plantlet regeneration protocol for the hybrid Cymbidium “Memoria Amelia Earhart”.