Effect of plant growth regulators on the accumulation of indolizidine alkaloids in Securinega suffruticosa callus cultures

In the presented work, plant growth regulators (PGRs) were tested for their influence on biomass growth and accumulation of therapeutically-relevant indolizidine alkaloids in Securinega suffruticosa (Phyllanthaceae) callus cultures. The study included 9 auxins [2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid, indole-3-acetic acid (IAA), 4-chlorophenoxyacetic acid, indole-3-butyric acid, 4-amino-3,5,6-trichloropicolinic acid, β-naphthoxyacetic acid, 1-naphthaleneacetic acid, indole-3-propionic acid, one polar auxin transport inhibitor (2,3,5-triiodobenzoic acid) and 7 cytokinins [2-isopentenyladenine, 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea, N-(2-chloro-4-pyridinyl)-N′-phenylurea, diphenylurea, zeatin, kinetin (KIN), 6-benzylaminopurine]. The respective PGRs were applied at 0.5 and 5.0 mg l−1, together with 5.0 or 0.5 mg l−1 KIN or 2,4-D (for auxins and cytokinins, respectively). The calli subjected to different phytohormone combinations (39 modifications in total) were evaluated for growth and alkaloid content, and the results tested for statistical differences. The highest concentrations of securinine (1.73 mg g−1 DW) and allosecurinine (3.11 mg g−1 DW) were recorded in the callus grown in the presence of 0.5 mg L−1 IAA and 5.0 mg L−1 KIN. To the best of the authors’ knowledge, this is the first such comprehensive report concerning the influence of PGRs on alkaloid accumulation in plant in vitro cultures.