Synergetic effects of TDZ with various phytohormones on high-frequency plant regeneration from mature nodal explants of Capparis decidua and their ex vivo implications

Capparis decidua (Forssk.) Edgew., is a well-known ornamental shrub of arid and semi-arid horticulture and agroforestry. This paper represents the synergism of thidiazuron (TDZ) with auxins and cytokinins for the development of an efficient shoot regeneration system from mature nodal explants. The optimum axillary shoot-bud differentiation occurred on Murashige and Skoog (Physiol Plant 15:473–497, 1962) medium augmented with 0.48 mg L⁻¹ TDZ and 0.1 mg L⁻¹ α-naphthaleneacetic acid (NAA). Shoot multiplication through repetitive transfer of mother explants was optimally achieved on MS medium having 0.24 mg L⁻¹ TDZ, 0.25 mg L⁻¹ 6-benzyladenine (BA), 0.1 mg L⁻¹ NAA, on which the maximum number of shoots (15.4 ± 0.92) were obtained after the third passage. Shoot amplification through subculturing was achieved on MS medium with 1.2 μg L⁻¹ TDZ, 0.75 mg L⁻¹ BA, 0.2 mg L⁻¹ Kinetin (Kin) and 150 mg L⁻¹ of ammonium sulphate [(NH₄)₂SO₄], on which the maximum shoot multiplication rate (40.6 ± 1.2 per culture vessel) was obtained. Microshoots were successfully rooted by in vitro and ex vitro methods. During in vitro rooting, more than 80% of the microshoots were rooted on MS¼ strength medium supplemented with 5.0 mg L⁻¹ Indole-3-butyric acid (IBA) and 200 mg L⁻¹ of activated charcoal (AC). For ex vitro rooting, pulse-treatment of 500 mg L⁻¹ IBA and 100 mg L⁻¹ β-naphthoxyacetic acid (NOA) for 5 min was found to be the best on which 94.66 ± 4.16% of the shoots produced 5.3 ± 0.64 roots per shoot of an average length 4.75 ± 0.89 cm. In comparison to plantlets developed from in vitro rooting, percentage survival of plants that rooted ex vitro was significantly (P < 0.05) higher. More than 93% of the micropropagated plants successfully survived in the field conditions. The young Ker fruits can be harvested twice a year (Mar–Apr and Jul–Aug). The present market prices of young and processed/dried Ker fruits are INR 250 to 300 and INR 1450 to 1500 per kg, respectively. The present protocol can be used for large-scale commercial propagation of this important ornamental and horticultural shrub.