CALLUS INDUCTION AND PLANT REGENERATION IN ECHINOCACTUS PLATYACANTHUS

Abstract

The aim of this research was to establish the optimal conditions for micropropagation of E. platyacanthus, a cactus that is used as a source of water and fodder for livestock during the dry season. To this end, two experiments were carried out. In the first, seed germination on Murashige and Skoog (MS) medium with different concentrations of mineral salts (50, 75 and 100%) and sucrose (10, 20, 30 and 40 g L-1) was evaluated. From the first experiment, we selected three-month-old seedlings, approximately 1.0 cm in length, and from each one of them three explants were obtained; the explants, in turn, were placed on MS medium with different concentrations of benzyladenine (BA) (0.0, 0.5, 1.0 and 2.0 mg L-1) and naphthaleneacetic acid (NAA) (0.0, 0.2, 0.5 and 1.0 mg L-1). In both experiments the factors and levels were combined in a factorial arrangement and established in a completely randomized design. In all cases, the culture medium was supplemented with myo-inositol (100 mg L-1), thiamine (0.4 mg L-1) and agar (6 g L-1), and its pH was adjusted to 5.7. In the first experiment, we began recording the number of germinated seeds 15 days after sowing (DAS); in the second, 60 DAS the variables callus fresh weight, callus diameter, shoot number and length and root number and length were recorded. The data were subjected to analysis of variance and mean separation tests (Tukey, p≤0.05) using the SAS Version 9 statistical package (SAS, 2003). Seed germination began at 16 DAS and ended 37 days later (53 DAS). Salt proportions under or equal to 75% were associated with germination rates of 70%, statistically higher than those obtained with MS medium with 100% mineral salts. The highest callus fresh weight was obtained in BA concentrations at or above 1.0 mg L-1. NAA concentrations at or above 0.5 generated callus diameters two to three times greater than without the hormone (0.59 cm). The NAAA—BA interaction was significant in shoot height, with the highest value (0.68 mm) being obtained with 0.2 mg L-1 NAA and 0.5 mg L-1 BA. Root number and length were negatively affected by the BA concentration.