An Efficient Micropropagation System for the Vulnerable Wild Apple Species, Malus sieversii, and Confirmation of Its Genetic Homogeneity

Traditional cultivation methods used for domestic apples are not effective when applied for cultivation of the vulnerable wild apple Malus sieversii. However, this apple can be effectively grown using micropropagation, which is an established ex situ conservation tool. The study aimed to grow in vitro M. sieversii cultures using axillary buds as explant. To optimize the media and plant growth regulator combinations for successful in vitro culture, three different media were used: Quoirin and Lepoivre (QL), woody plant medium (WPM), and Murashige and Skoog (MS) containing four different concentrations of 6‑benzylaminopurine (BAP) combined with 0.2 mg/l or 0.5 mg/l of gibberellic acid (GA). Different concentrations of indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA) added to half-strength QL medium were used for optimizing the rooting medium. The combination of QL medium with 1.5 mg/l BAP and 0.01 mg/l IBA resulted in 100% shoot regeneration. The number of shoots (17.20 ± 0.64) and shoot length (2.80 ± 0.10 cm) were greatest when QL medium with 0.75 mg/l BAP and 0.2 mg/l GA was used. One hundred percent root development with the greatest number of roots per explant (8.13 ± 0.44) and longest root length (3.77 ± 0.23 cm) were achieved when half-strength QL medium with 0.5 mg/l of IBA was used. Simple sequence repeat analysis confirmed the reliability of this protocol for efficient large-scale micropropagation of M. sieversii. Through this study, an efficient micropropagation protocol that can be used for large-scale cultivation as well as germplasm conservation of M. sieversii was developed.