Opuntia ficus-indica (L.) Mill.: Cladode explants with several areoles, forchlorfenuron and indole-3-butyric acid for optimized in vitro culture and NPK controlled release fertilizer for direct ex vivo rooting

The genus Opuntia includes more than 300 species, with the most economically important being Opuntia ficus-indica. In this study, the in vitro propagation potential of the prickly pear cactus (O. ficus-indica (L.) Mill.) was evaluated. For shoot initiation (6 weeks, MS medium, 25 ± 1 °C, 24 h dark), three cladode explant types based on areole number (none, one, several), five BA (2, 3, 4, 5 and 6 mg L-1) and four IAA concentrations (0, 1, 1.5 and 2 mg L-1) were tested. The results showed 100% shoot induction by cladodes with several areoles under 6 mg L-1 BA + IAA (1-2 mg L-1), compared to cladodes with one (63.33-66.67%) or none areole (26.66-30%). For multiplication of in vitro shoots derived from areole stimulation, four cytokinins [6-benzyladenine (BA), kinetin (Kin), thidiazuron (TDZ), forchlorfenuron (CPPU)] alone and combined with two auxins [indole-3-acetic acid (IAA), 2,4-dichlorophenoxy acetic acid (2,4-D)] were tested (8 weeks, Murashige-Skoog medium, 25 °C, 16h photoperiod). These results showed significantly higher shoot number (5.10) and length (6.19 cm) under 5 mg L-1 CPPU and 5 mg L-1 CPPU + 0.5 mg L-1 2,4-D, respectively. For in vitro rooting, three auxins [indole-3-butyric acid (IBA), indole-3-acetic acid (IAA), α-naphthaleneacetic acid (NAA)] were applied (5 weeks, MS medium, 25 °C, 16-h photoperiod) and the results showed higher root number (19.06) with 0.5 mg L-1 IBA. For acclimatization, rooted microshoots (ex vitro) placed in a peat: vermiculite substrate and non-rooted microshoots (ex vivo) to the same substrate but supplemented with different concentrations (0, 0.8, 1.2, 1.6, 2 g alveoli-1) of a controlled release fertilizer (CRF, 15%N-9%P2O5-12%K2O). After 10 weeks in the greenhouse (24 ± 5 °C/ 18 ± 5 °C), 100% rooting (ex vivo) and survival (ex vitro, ex vivo) were recorded, nonetheless 1.2 g alveoli-1 CRF gave higher ex vivo root number (23.05).