Development of a micropropagation protocol for Malus orientalis using axillary buds

Abstract

Caucasian apple trees (Malus orientalis) grow individually or in small groups with a scattered distribution pattern throughout the Hyrcanian forest. The wild gene pool in such trees has a high genetic diversity which is highly important for apple breeders. Micropropagation can be advantageous due to its quick propagation for apple breeders as well as its maintenance of in vitro and in vivo germplasm collection and exchange. Here, for the first time, we investigated the in vitro propagation of M. orientalis from three populations by collecting axillary buds and established a micropropagation protocol. Two strengths of Murashige and Skoog (MS) basal medium (full and half) in combination with different concentrations of 6-benzylaminopurine (BA) were tested for optimal multiplication. The interaction among the BA concentrations, MS strength, and populations was effective in the promotion of shoot development across the three populations. The average number of the produced shoots, shoot length, and number of leaves was significantly affected by this triple interaction. As a result, BA at the concentration of 0.4 mg L−1 worked for all the populations. The results showed that a rooting percentage of 77.8% was obtained on half strength Linsmaier and Skoog (LS) medium in combination with 0.9 mg L−1 3-indole butyric acid (IBA). However, the subculture of shoots on half strength LS medium supplemented with 0.9 mg L−1 IBA increased rooting percentage up to 96% and produced the highest number of roots (7.18 roots per shoot).