The prerequisite to obtain success in the plants genetic transformation, and also for the fast multiplication of the modified genotype through the micropropagation, it is a efficient regeneration protocol. The objective of this work was to study the expression of the morphogenetic potential of thin fragments of apple tree leaves, and to optimize a regeneration protocol seeking futures works of genetic transformation. The completely randomized experimental design was used, in factorial outline 3 x 2 x 6, with three cultivate of apple tree (Galaxy, Maxigala and Mastergala), two explants types (thin fragments of leaves cut in the transversal and longitudinal direction), and six concentrations of thidiazuron (TDZ) in the culture medium (0; 4.54; 9.08; 13.62; 18.16 and 22.7 µM), totaling 36 treatments. The MS medium salts and vitamins were added of myo-inositol (100 mg.L-1), sucrose (30 g.L-1), agar (6 g.L-1) and 1.6 µM naphthaleneacetic acid (NAA). Flasks with capacity for 150 mL with 6 mL of culture medium were used. The explants were obtained of plants in vitro cultivated, in multiplication phase, 45 days after the inoculation, and they were constituted of fine fragments of the medium part of leaves, cut in the tranversal direction (length from 8 to 10 mm) or longitudinal (length from 10 to 12 mm), both with approximate width of 1 mm. The regeneration percentage, the intensity of callus formation and the number of shoots formed by explant were evaluated by the 45 days of cultivation. Starting from the obtained results it was ended that the expression of the morphogenetic potential of the thin fragments of leaf cut in the transversal direction is higher than those cut in the longitudinal direction, and its cultivation in culture medium with 4.54 µM of TDZ, propitiates, simultaneously, high regeneration percentage, great number of shoots formation and smaller callus intensity.
tissue culture; shoots regeneration; growth regulators; thidiazuron; explant type
