Effect of cytokinins on multiplication of stone fruit rootstocks in vitro

Abstract

Clonal rootstocks are actively used for stone fruit crops, and clonal micropropagation may be effectively applied for their propagation. However, to achieve high micropropagation efficiency, optimal growing parameters for explants should be selected including nutrient medium composition and phytohormone concentrations. The research goal was to evaluate the effect of various cytokinins (6-BAP, kinetin, TDZ) on shoot formation of clonal stone fruit rootstocks PK SK 1, PKG 18/3, and Druzhba in vitro. The maximum multiplication rate (5.5–7.9 shoots per explant) was provided by 6-BAP at 1.0 mg L. With kinetin (3.0 mg L) the number of shoots was 3.7-4.6 which was by 35-58% lower than the control; TDZ (0.3 mg L) gave 2.8–3.3 shoots. The combination of 6-BAP (0.5 mg L) and TDZ (0.25 mg L) had a synergistic effect (4.6-6.5 shoots) but was by 9-19 % lower than the control. The best microshoot length (2.1-2.3 cm) and leaf number (6.4-8.3) were also obtained with 6-BAP 1.0 mg L. Kinetin at 3.0 mg L provided shoot length of 1.8-2.2 cm and leaf number of 6.2-7.5 approaching the control. Thus, for the studied rootstocks, 6-BAP at 1.0 mg L is the most effective, and kinetin may be recommended for the elongation stage before rooting.