Lateral Shoot Induction with Exogenous 6-benzylaminopurine Application at the Vegetative Growth Stage in Phalaenopsis
Ji Woo Park1,2, Nam Hyun Im1,2, Su Yong Shim2, Hyo Beom Lee1,2,3*
1Department of Agriculture, Forestry and Bioresources, Seoul National University, Seoul 08826, Korea
2Department of Horticultural Science & Biotechnology, Seoul National University, Seoul 08826, Korea
3Research Institute of Agricultural and Life Sciences, Seoul National University, Seoul 08826, Korea
Phalaenopsis is a monopodial orchid, and the number of flower-stalks is the primary indicator of commercial value in this orchid. We hypothesized that the induction of lateral shoots by exogenous cytokinin application could increase the number of inflorescence. This study was performed to determine whether exogenous 6-benzylaminopurine (BAP) application consistently results in lateral shoot induction in Phalaenopsis. In the first experiment, immature (8-month-old with 3 - 4 leaves) and mature (18-month-old with 6 - 7 leaves) Phalaenopsis Queen Beer ‘Mantefon’ plants were treated with either 0 or 100 mg·L-1 BAP as a foliar spray, 20 mL per plant, and twice in one-week interval, under 28℃ vegetative growth condition. In the second experiment, three different cultivars (‘Mantefon’, ‘Flamingo’, and ‘Surf Song’) of Phalaenopsis plants (9-month-old with 5-7 leaves) were treated with 10 mL of 0, 100, 200, or 400 mg·L-1 BAP as before. In both experiments, lateral shoot was induced only when BAP was applied. In the first experiment, lateral shoot formation percentages were 73% and 93% in immature and mature plants, respectively, when treated with 100 mg·L-1 BAP. The number of lateral shoot was significantly higher in mature plants. Immature plants produced 1.1 lateral shoots, whereas mature plants produced 2.1 lateral shoots, on average per each plant. In the second experiment, lateral shoot formation percentages and the number of lateral shoot significantly increased as BAP concentration increased, across all three cultivars tested. BAP concentration also had a significant effect on new leaf number and total leaf number. A significant difference was observed in the lateral shoot number among cultivars, indicating a different cultivar sensitivity to BAP treatment. Overall, these results demonstrate that lateral shoots are induced with exogenous BAP application at the vegetative growth stage in Phalaenopsis orchids, and mature plants and higher BAP concentrations result in greater response in terms of lateral shoot number and lateral shoot formation percentage. Lateral shoot induction is expected to increase flower-stalks, which would in turn increase commercial value of Phalaenopsis orchids.