Rapid in vitro multiplication and ex vitro rooting of Malus zumi (Matsumura) Rehd

Micropropagation system of Malus zumi was optimized by studying the influence of plant growth regulators and culture conditions. The axillary buds were used for mutiplication of in vitro shoot culture on agar Murashige and Skoog (1962) (MS) medium with combination of 1 mg l⁻¹ BAP, 0.5 mg l⁻¹ NAA or 0.5 mg l⁻¹ IAA or 0.5 mg l⁻¹ IBA under 16 h photoperiod. The shoot growth in culture was not significantly affected within a broad range (5.0–7.0) of initial medium pH. The highest shoot (13) was obtained on medium containing 1.0 mg l⁻¹ BAP and 0.5 mg l⁻¹ IAA. Well-developed shoots, 35–50 mm in length, were successfully rooted ex vitro at 86.3% by a 2-h-treatment with aqueous solution containing MS salts and 100 mg l⁻¹ IBA prior to their planting in growing substrate composed of soil and vermiculite (1:1 v/v). The survival rate of transplantation reached 88.0% when transferred to field condition.