The effects of zinc oxide nanoparticles loaded with IAA and IBA on in vitro rooting of apple microcuttings

Authors: SHABNAM ALIZADEH, HATİCE DUMANOĞLU

Abstract: In the micropropagation of difficult-to-root plants, the low rates of rooting cause high economic losses. The local apple (Malus domestica Borkh.) cultivar #67, which is highly resistant to fire blight disease, has been shown to have low rooting success. Nanoparticles loaded with auxins could increase the rooting success with their physicochemical properties. To increase rooting percentage, the effects of zinc oxide nanoparticles (nZnO), nZnO loaded with indole-3-acetic acid (IAA-nZnO) and indole-3-butyric acid (IBA-nZnO) at different concentrations (1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 mg L^-1) on in vitro rooting of microcuttings were investigated. The concentrations of auxin carried by the nanoparticles were 2.8, 5.7, 8.0, 10.8, 13.7, 16.0 μM IAA or 2.5, 4.4, 6.9, 9.3, 11.3, 13.8 μM IBA. The various concentrations of IAA (0.0, 2.8, 5.7, 11.4, 17.1 μM) and IBA (0.0, 2.5, 4.9, 9.8, 14.8 μM) were also examined. All substances as described previously were incorporated to half-strength Murashige and Skoog (½ MS) medium containing 2% sucrose at pH 5.8, and solidified with 0.7% agar. The microcuttings were cultured on these media for 5 days in the dark before being transferred to a 16 h photoperiod conditions at 25 ± 1 °C for 6 weeks. It was found that rooting did not occur at 0.0 μM IAA and IBA concentration and nZnO treatments. IBA-nZnO and IBA were more effective on the rooting of microcuttings. In the comparison of IBA-nZnO and IBA, the percentage of rooting was higher in IBA-nZnO (58.4%) than IBA (47.5%). In addition, 4.4 μM or 4.9 μM IBA, particularly, induced many favorable properties with high rooting percentage (62.7%) and root length (16.5 ± 3.5 mm) and a small callus diameter (5.3 ± 0.2 mm). In conclusion, IBA-nZnO loaded with 4.4 μM IBA could be a promising treatment for in vitro rooting of difficult-to-root apple cultivar #67.

Keywords: Auxin, Malus, micropropagation, nanotechnology, tissue culture

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