Shoot Induction, Multiplication, Rooting and Acclimatization of Black Turmeric (Curcuma caesia Roxb.): An Important and Endangered Curcuma Species

Abstract

Curcuma caesia Roxb., commonly known as Kali Haldi or black turmeric, is one of the important species in the genus Curcuma. This species has been classified as one of the endangered Curcuma species due to the drastic decrement of this plant in its natural habitat. C. caesia has been overharvested for various purposes, including bioactive compound extraction to fulfill the pharmaceutical industry demand. Hence, this study was conducted to establish a protocol for the propagation of C. caesia via plant tissue culture techniques. In the shoot induction stage, three basal medium formulations, including Murashige and Skoog (MS medium), the combination of Murashige and Skoog macronutrients and B5 micronutrients (MSB5 medium) and woody plant medium (WPM medium) supplemented with 15 μM of 6-benzylaminopurine (BAP), were used. The results found that the MSB5 medium was the most suitable basal medium formulation for shoot induction of C. caesia. In the subsequent experiment, different types of cytokinin, including BAP, kinetin and 2-iP at concentrations of 5, 10, 15 and 20 μM, were fortified in the MSB5 medium for shoot multiplication. The shoot multiplication was further enhanced by supplementing the MSB5 medium with indole-3-butyric acid (IBA) or 1-napthaleneacetic acid (NAA) at the concentrations of 2, 4, 6 and 8 μM. The results showed that a combination of 15 μM of BAP and 6 μM of IBA significantly increased the shoot multiplication with 100% shoot induction, 3.53 shoots/explant, 10.81 cm of shoot length, 9.57 leaves, 0.486 g of leaves fresh weight and 0.039 g of leaves dry weight. After the multiplication, the rooting stage was carried out by altering the basal medium strength into half and full strength and supplementing with 2.5, 5, 7.5 and 10 μM of indole-3-acetic acid (IAA). The full strength of MSB5 medium supplemented with 5 μM of IAA exhibited the highest number of roots and length of roots, with 6.13 roots and 5.37 cm, respectively. After the rooting stage, the plantlets were successfully acclimatized in the potting medium with the combination of cocopeat and peatmoss, and the ratio of 1:1 was found to produce the highest survival rate with 77.78%. In conclusion, the protocol established in this study could be useful for large-scale raw material production, either for conservation or bioactive compound extraction.