The M.9 rootstock is utilized in high-density apple orchards due to the low height of the plants, which facilitates care during cultivation and picking. Micropropagation can be utilized for its mass propagation, although rooting and acclimatization are impediments for the commercial use of this technology. This study was conducted in order to evaluate different levels of indolebutyric acid (IBA) in ex vitro rooting and simultaneous acclimatization of M.9 apple rootstock. The bases of the shoots resulting from the in vitro multiplication process, 2.5 to 3 cm in height and with two pairs of leaves, were immersed in concentrations of IBA of 0; 500; 1000 and 1500 mg.L-1, for 10 seconds and placed in Styrofoam trays with cells containing 50 ml of substrate containing carbonized rice husks + vermiculite (1:1, v/v). For 30 days the trays were kept in plastic boxes covered with glass tops to keep the environmental humidity high. The higher percentages of rooting (82 and 84%) were obtained in the treatments with 500 and 1000 mg.L-1, respectively The length of the roots, with an average of 4.2 cm, was not affected by the treatments applied. After this evaluation, the plants were cultivated in a greenhouse for 45 days, in containers with the substrate Plantmax® (Eucatex, São Paulo, BR). The levels of IBA utilized in the rhyzogenesis induction did not modify the number and the length of the roots or the number of leaves and the height of the plants although the highest survival of the plantlets after transplant to commercial packages (95%) was obtained with 500 mg.L-1of IBA.
Malus pumilla; micropropagation; substrate; indolbutiric-acid
