Effects of genetic, explant type, plant growth regulator and culture medium on in vitro regeneration of commercial Phalaenopsis orchid cultivars

The Phalaenopsis orchid is the most popular genus of Orchidaceae family with high marketability due to its butterfly shape and attractive flowers. The aim of this study was to investigate the effects of cultivar, explant type, plant growth regulators and culture medium on in vitro propagation of Phalaenopsis orchid. Experiment was conducted using 4 combined treatments of benzyladenine (BA) and indolebutyric acid (IBA) (BA 2 and 4 mg L-1 with IBA 0.5 and 1 mg L-1), 2 culture media (MS and Chen), 2 types of explants (leaf and stem), and 5 commercial cultivars of Phalaenopsis orchids. The findings revealed that the studied factors had significant effects on leaf and root primordia initiation, number of protocorms, and number of leaves and roots. Among the investigated cultivars, 2 cultivars: Nottingham and Dubrovnik showed earlier leaf and root primordia initiation. Two treatments including BA+IBA (2+0.5 mg L-1 and 2+1 mg L-1), and Chen culture medium showed faster primordia initiation significantly different from the other treatments. Leaf explants produced more protocorm than stem explants. The highest number of protocorms was belonged to Nottingham cultivar, and the treatment of BA+IBA (2 to 1 mg L-1) on Chen culture medium. The number of leaves and roots of in vitro plantlets were significantly affected by various factors so that, Dubrovnik had more leaves and the Nottingham had more roots than the other cultivars. The highest number of leaves was observed in BA+IBA (2+0.5 mg L-1) treatment, while the highest number of roots was belonged to BA+IBA (2+1 mg L-1) treatment. Comparing the media, Chen medium showed more positive effects on leaf and root number than MS medium. The results of this study indicated that the success of regeneration of Phalaenopsis cultivars in vitro is influenced by the characteristics of the cultivar, medium, and plant growth regulator treatments. Nottingham cultivar and leaf explant showed better regeneration rates in vitro. Increasing the concentration of BA from 2 to 4 mg L-1, increased the time required for leaf and root primordia initiation and prolonged the in vitro cultivation period.