Mineral nutrition of Curcuma longa L. in bioreactors affects subsequent development of curcuminoids following transfer to the greenhouse

• We examine the subsequence effects of in vitro factors on greenhouse response.
• The multi-factor design allowed us to optimize many factors at once.
• Plant density and mineral interactions affected curcuminoids concentrations.
• Low plant density and high P increase curcuminoids under low fertilizer treatment.
• High plant density and low P increase curcuminoids under high fertilizer treatment.

This work examined the concentrations of the curcuminoids in Curcuma longa L. from an experimental array (response surface method using D-optimal selection of treatments) of greenhouse plants repeated in both high and low-input fertilizer treatments. Curcuminoids concentrations in dry rhizomes were analyzed by HPLC–ESI–MS/MS. In vitro mineral concentrations (PO43−, Ca2+, Mg2+, and KNO3) and plant density significantly influenced the subsequent growth of turmeric plants in the greenhouse during a six-month growing season. In the high fertilizer treatments, the in vitro interaction of PO43− with Ca2+ and Mg2+ concentrations maximized curcumin and demethoxycurcumin concentrations in the rhizomes. The highest concentrations of curcumin and demethoxycurcumin were 154.7 ± 4.1 μg/g and 1258.9 ± 58.8 μg/g with 1.25 mM PO43−, 3 mM Ca2+, 1.5 mM Mg2+, and 60 mM KNO3 and with 18 or 11 buds/vessel respectively. Reducing KNO3 concentration to 20 mM at 1.5 mM Mg2+ and 9 mM Ca2+ maximized bisdemethoxycurcumin concentration to 25.0 ± 2.6 μg/g with 9 buds/vessel. The best induction media under the low-input fertilizer treatments had similar optimal set points for all three curcuminoids; curcumin, demethoxycurcumin, and bisdemethoxycurcumin concentrations were maximized to 201 ± 26.8 μg/g, 813 ± 138 μg/g, and 23.5 ± 4.6 μg/g respectively with 6 buds/vessel, 6.25 mM PO43−, 3 mM Ca2+, 1.5 mM Mg2+, and 60 mM KNO3. High plant density with moderate mineral concentrations in vitro increased curcumin/bisdemethoxycurcumin ratio to 17.5 ± 1.7 under low-input fertilizer. In the high fertilizer treatments, maximum concentrations of each curcuminoid had distinct mineral requirements, but in the nutrient limited treatments, all curcuminoids had similar optima for mineral concentrations and plant density requirements. With low-fertilizer input, the low in vitro plant density was the primary factor to maximize the concentration of curcuminoids in the rhizomes. The multi-factor design sufficiently identified the interactive effects among varied minerals on curcuminoids concentrations. This approach allows a propagation laboratory to develop propagation stock best suited to secondary metabolite production in the end-user facility.