Shortening of the Juvenile Phase of the Southern Highbush Blueberry (Vaccinium corymbosum L. interspecific hybrid) Grown in Controlled Rooms under Artificial Light

Abstract

We attempted to shorten the juvenile phase of southern highbush blueberries by using controlled rooms under artificial light. Seeds were extracted from fresh fruits and sowed in the Woody Plant Medium (WPM) immediately after harvest. When these seeds were irradiated with red LED, their germination rate was over 80% by the 35 days after sowing. The seedlings in the controlled room continued to grow without entering the dormant phase. Especially, maximum growth was observed under the long-day condition of 12-h light. Even under the short-day condition of 8-h light, increased growth was observed when grown at a high light intensity (400 μmol·m⁻²·s⁻¹). For the seedlings that were moved from the long-day controlled room to the short-day controlled room after 10 months, the ‘Misty’ seedlings flowered within 327 days after sowing while the ‘Sharpblue’ seedlings flowered within 357 days after sowing. Furthermore, when cultivated under the short-day condition at 400 μmol·m⁻²·s⁻¹ for the entire length of the experiment, the flowering of ‘Misty’ seedlings was observed within 300 days after sowing. The seedlings maintained under the short day condition of high light intensity flowered earlier than seedlings moved from the long-day controlled room to the short-day controlled room. Thus, southern highbush blueberries were successfully induced to flower in less than a year from seed planting, using a combination of techniques to promote germination and control the growth environment conditions in a controlled room.