Effects of synthetic auxins on the in vitro rooting of apple tree

Abstract

Apple shoots (Malus domestica, Borkh), cv. Fred Hough derived from in vitro multiplication process were inoculated in MS and MS/2 basal media added by growth substances indol acetic acid (IAA); indol butiric acid (IBA) and naphtalene acetic acid (NAA) at 0, 1, 3 and 5 µM. The media also included: MS vitamins, myo-inositol (100.0 mg/L); sucrose (30.0 g/L); agar (6.0 g/L). The pH was adjusted to 5.8 before autoclaving. The treatments were incubated in a growth room at 25±2^oC, 16 hours photoperiod under light intensity of 2,000 lux during 30 days. The treatments were replicated five times. Each replicate was composed by a 250 mL flask containing 40 mL medium with five explants. The medium MS/2 in all the tested concentrations was better than MS. The NAA and IBA, both at 3.0 µM on MS/2 showed similar effects as percentage of rooting and number of roots are concerned. However, NAA treated explants presented a higher callus incidence at the base of shoots along with thicker roots. IAA had a better response when used in higher concentrations but it did not achieve the performance of IBA ou NAA.