Disinfected seeds were distributed between two layers of sterile filter paper soaked with 2.5% gibberellic acid (GA3) for 5 days. After this period, the seeds were mechanically scarified with a scalpel, and inoculated on ½ MS medium (half-strength of MS salts, MS vitamins, and 1.5% (w/v) sucrose) solidified with 0.7% agar (Merck), followed by incubation in a germinator with a photoperiod of 8 h using a total irradiance of 28.7 mol m−2 s−1 provided by cool-white fluorescent lamps and alternate temperatures (30 ◦C for 8 h and 20 ◦C for 16 h) for 60 days (Osipi and Nakagawa, 2005). In order to obtain primary cultures, shoot apices and nodal segments were excised from 30-day old seedlings, inoculated on ½ MSM medium (half-strength of MSM salts, MS vitamins and 1.5% (w/v) sucrose) solidified with 0.7% agar, and incubated under a 16-h photoperiod.