Tissue culture response and in vitro plant regeneration of ‘Haruka’ ( Cerasus Sato-zakura Group ‘Haruka’), a new cultivar of Japanese flowering cherry

This study describes the in vitro regeneration of ‘Haruka’ plants, a new cultivar of Japanese flowering cherry registered in 2021 by the Japanese statutory authority. As this is a double-flowered cultivar produced by inter-specific hybridization, in vitro regeneration is an effective method for large-scale propagation. To promote proliferation, apical shoots were cultured on half-strength Murashige and Skoog medium supplemented with 5 μM 6-benzylaminopurine. The highest average of 7.8 shoots per explant was obtained at 15°C in the dark. Cultures were maintained in continuous darkness for 12 wk and then transferred to lighting conditions under a 16-h photoperiod at 25°C. Subsequently, a 100% rooting rate was obtained with the application of 1 μM indole-3-butyric acid in combination with 0.1 μM naphthaleneacetic acid. Additionally, the number of roots per shoot and the maximum length of roots were significantly higher under exposure to pink light illumination provided by cold cathode fluorescent lamps emitting red- and blue-colored light at a ratio of 80% and 20%, respectively. More than 95% of the regenerated plantlets survived after ex vitro acclimatization.