Transplant pre-chilling induces earlier flowering and fruiting for forcing-cultured June-bearing strawberries

Abstract

Advancing the flowering and fruiting to extend the shelf life possesses a great commercial value for industrial strawberry production. This study was conducted to investigate the effects of chilling and photoperiod on flower induction and fruit productivity in three June-bearing strawberries. The experiment was carried out in an industrial refrigeration warehouse and a greenhouse. One month-old cutting-propagated transplants were moved to and grown in rooms with an chilling air temperature of either 8 or 15 degrees C for 4 or 6 weeks starting on July 15. White LEDs with a 150 mu mol.m(-2).s(-1) PPFD were lit in these cold rooms for 11 hours (a short day) or 15 hours (a long day) to provide the necessary light for plant growth. The plants were transplanted to hydroponic systems in a greenhouse after being chilled. The results showed that chilling transplants at either 8 or 15 degrees C for either 4 or 6 weeks significantly promoted flower bud induction in all three cultivars, while the photoperiod supplied in cold rooms did not affect the flowering. Moreover, the time of initiation of the secondary inflorescence was not significantly affected by chilling, except in 'Kuemsil'. Fruits of 'Seolhyang' were ready to be harvested at the end of September, while those of 'Kuemsil' and 'Maehyang' were ready for harvest at the beginning of October, which corresponded to 52, 55, and 57 days earlier than that of their respective control, not chilled plants. The fruit yield decreased after chilling because the high temperature during fruiting in autumn resulted in a great number of small and decayed fruits. However, the soluble solids content and acidity of the fruits harvested on chilling-treated plants did not show any differences with those of the control, indicating that the flavor was marketable. In a conclusion, 4 weeks of chilling at 15 degrees C during the summer can be used for early flowering and fruiting in June-bearing strawberries. Further work should be focused on mitigating the problem of producing small and decayed fruits.