Axillary shoot growth of Phalaenopsis species in different types and concentrations of cytokinin in vitro

Phalaenopsis is one of the favorite genera in Orchidaceae family. In vitro culture is a very useful method for orchid propagation and conservation. Axillary shoot growth in vitro may reduce the possibility of somaclonal variation compared to protocorm-like body propagation method for Phalaenopsis. The study evaluates the axillary shoot growth of three species of Phalaenopsis in different types and concentrations of cytokinin. The plant materials used were young seedlings originated from seed germination. The experiment used a randomized complete block design with two factors. The first factor was the species of Phalaenopsis (P. cornu-cervi, P. amboinensis, and P. tetraspis), and the second one was the types of cytokinin (control without cytokinin, 22.2 μM benzylaminopurine (BAP), 11.1 μM kinetin (KIN), and 11.1 μM thidiazuron (TDZ)). A half strength of Murashige and Skoog (MS) medium supplemented with 15% coconut water and 0.53 μM NAA was used as a basal medium. The results showed that the highest percentage of explant-forming shoots was on P. amboinensis (66.7%) and P. cornu-cervi (55.6%) in 11.1 μM kinetin; while, P. tetraspis (100%) was in 11.1 μM TDZ. The interaction between Phalaenopsis species and cytokinins did not significantly affect the number of shoots, leaves, and roots. P. tetraspis produced the highest number of shoots (1.6 shoots), followed by P. amboinensis (0.7 shoots) and P. cornu-cervi (0.4 shoots). However, 22.2 μM BAP and TDZ tended to produce a higher shoot number than kinetin; while, kinetin promoted a higher number of roots than BAP and TDZ. 11.1 μM kinetin and 11.1 μM TDZ resulted in a better visual performance of shoot and leaf color than BAP treatments. The results suggested that the genetic background is the main factor to determine the axillary shoot growth in vitro.