In vitro mineral nutrition of Curcuma longa L. Affects production of volatile compounds in rhizomes after transfer to the greenhouse

Background: Turmeric is a rich source of bioactive compounds useful in both medicine and cuisine. Mineral concentrations effects (PO₄ ^3-, Ca²⁺, Mg²⁺, and KNO₃) were tested during in vitro rhizome development on the ex vitro content of volatile constituents in rhizomes after 6 months in the greenhouse. A response surface method (D-optimal criteria) was repeated in both high and low-input fertilizer treatments. Control plants were grown on Murashige and Skoog (MS) medium, acclimatized in the greenhouse and grown in the field. The volatile constituents were investigated by GC-MS. Results: The total content of volatiles was affected by fertilizer treatments, and in vitro treatment with Ca²⁺ and KNO₃; but PO₄ ^3- and Mg²⁺ had no significant effect. The content was higher in the high-input fertilizer treatments (49.7 ± 9 mg/g DM) with 4 mM Ca²⁺, 60 mM KNO₃ and 5 mM NH₄ ⁺, than the low-input fertilizer (26.6 ± 9 mg/g DM), and the MS control (15.28 ± 2.7 mg/g DM; 3 mM Ca²⁺, 20 mM K⁺, 39 mM NO₃ ^-, 20 mM NH₄ ⁺, 1.25 mM PO₄ ^3-, and 1.5 mM Mg²⁺). The interaction of Ca²⁺ with KNO₃ affected curcumenol isomer I and II, germacrone, isocurcumenol, and β-elemenone content. Increasing in vitro phosphate concentration to 6.25 mM increased ex vitro neocurdione and methenolone contents. Conclusion: These results show that minerals in the in vitro bioreactor medium during rhizome development affected biosynthesis of turmeric volatile components after transfer to the greenhouse six months later. The multi-factor design identified 1) nutrient regulation of specific components within unique phytochemical profile for Curcuma longa L. clone 35-1 and 2) the varied phytochemical profiles were maintained with integrity during the greenhouse growth in high fertility conditions.