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

Abstract

Background: Apple (Malus × domestica Borkh.) is one of the most important fruit crops in the world. Traditionally, vegetative propagation methods (including cutting, budding, and layering) are time-consuming (about three years), with low production rates and low success in obtaining virus-free plants. Objective: The present study was planned to investigate the in vitro propagation of apple (M. domestica) cultivars from nodal segments. Methodology: 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 the MS medium were assessed. The effect of full and half-strength MS medium on root induction was investigated. Results: Examination of the effects of MS medium supplemented with various concentrations of indole-3-acetic acid (IAA) and kinetin revealed that the 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 micro shoots 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 micro shoot among the apple cultivars. Among the cultivars, significantly the highest rooting rate(48.30%), root number (6.25), and root length (4.15cm) were recorded for cultivar ‘Princess’ on full-strength MS medium. Conclusion: PGR combination of IAA (1.0 mg/L) and kinetin (3.0 mg/L) was found to be the best for shoot proliferation. The shoot responses were found to increase with an increase in kinetin concentration combined with IAA at 1.00 mg/L.