Optimization of Hormonal Compositions of Media for In vitro Propagation of Apple (Malus ×domestica Borkh.) Cultivars

Apple (Malus × domestica Borkh.) is one of most important fruit crop in the world. Traditionally, vegetative propagation methods (including cutting, budding, and layering) are time consuming (about three years), with a low production rates and low success in obtaining virus-free plants. The present study was planned to investigate the in vitro propagation of apple (M. domestica) cultivars from nodal segments. The Murashige and Skoog (MS) medium supplemented with sucrose and different concentrations of plant growth regulators (PGRs) were used for shoot proliferation and root induction. The optimal concentrations of PGRs in MS medium were assessed. The effect of full and half strength MS medium on root induction was investigated. Examination of the effects of MS medium supplemented with various concentrations of indole-3-acetic acid (IAA) and kinetin revealed that significantly highest shoot response was recorded for the ‘Princess’ cultivar with maximum shoot proliferation rate (65.25%), shoot number per explant (2.57), shoot length (7.28cm), and leaf number per shoot (6.15) after four weeks of culture. The root induction in microshoots of three apple cultivars was observed after 20 days of culturing. The strength MS medium (full and half) containing 1.5 mg/L IAA significantly affected (at P<0.05, chi square test) root induction in all three apple cultivars, especially rooting rate. However, there was no significant difference in root number and root length per microshoot among the apple cultivars. Among the cultivars, significantly highest rooting rate(48.30%), root number (6.25),and root length (4.15cm)were recorded for cultivar ‘Princess’ on full strength MS medium. PGR combination of IAA (1.0 mg/L) and kinetin (3.0 mg/L) was found to be the best for shoot proliferations. The shoot responses were found to increase with an increase in kinetin concentration combined with IAA at 1.00 mg/L.