Effective scion propagation using light-emitting diode irradiation for nursery stock production in Japanese persimmon

The objectives of this study were to determine the developmental responses of Japanese persimmon seedlings (Diospyros kaki Thunb.) to variations in photoperiod and light conditions, and to develop an effective method for scion propagation using light-emitting diode (LED) irradiation for nursery stock production. Shoot length and number of nodes increased after an irradiation treatment of 20 h/day compared with that of 12 h/day. Shoot length under red LED light was significantly greater than under blue LED light in the 20 h/day treatment. The number of nodes also increased under red LED light compared to blue LED light. The number of leaf primordia was significantly larger in grafts in late July compared to late June. The survival rate of scions and the shoot lengths were greater for grafts in late July compared to late June. The number of buds in grafts in late July was significantly higher than in late June. Based on these results, we propose that twice grafts per year, consisting of a bark graft in February and a green graft in July, is a better alternative to the conventional once graft in Spring because of the higher survival rate of scions and their accumulation of larger numbers of buds. Our alternative method achieves up to a 6-fold improvement in scion propagation rate compared to the once graft approach.