The aim of this study was to determine changes in the Knudson medium by supplementation with iodide potassium and cobalt chloride to improve the in vitro growth of Cattleya loddigesii Lindl. plantlets. In vitro seedlings of approximately 1 cm in length were inoculated on test tubes containing 15 mL of modified Knudson C medium, supplemented with iodide potassium (0; 0.45; 0.90 and 1.35 mg.L-1) and cobalt chloride (0; 0.015; 0.030 and 0.045 mg.L-1) in all possible combinations. The pH of the culture medium was adjusted to 5.8 ± 0.1 and solidified with 5 g.L-1 of agar before sterilization at 121°C and 1 atm per 20 minutes. The cultures were maintained in growth room with irradiance around 35 µmol.m-2.s-1, temperature at 25±1ºC and photoperiod of 16 hours. After 120 days, there were evaluated the number of roots, average length of roots and shoots and fresh weight of seedlings. The cobalt chloride at its highest concentration (0,045 mg L-1) added to the modified Knudson C without supplemental potassium iodide, gave the best results for the in vitro growth of Cattleya loddigesii seedlings.
Culture medium; Cattleya loddigesii Lindl.; micropropagation
