Effects of a New Plant Growth Regulator on Callus Induction from Immature Embryo Explants of Korean Pine (Pinus koraiensis)

Somatic embryogenesis is currently the most promising technique for the large-scale production and breeding of conifer species. Nonetheless, the low explant induction rate in this process hampers the development of improved materials. In this study, three immature Korean pine (Pinus koraiensis) embryos capable of induction were used as experimental materials. Various concentrations of brassinolide (BL), melatonin (Mel), salicylic acid (SA), glutathione (GSH), and ascorbic acid (AsA) were added to induce embryogenic callus tissue. The results show that BL had the most significant positive effect on promoting induction and increasing explant survival. Mel was also found to slightly increase the induction and survival rates of explants. When 1.00 mgL-1 BL was added to the explants derived from stock tree I, which had strong self-induction ability, for 30 days, the callus induction rate rose to 400% compared to the control group. Following the addition of 25 mgL-1 Mel to stock tree I for 30 days, the callus induction rate further increased to 450% of the control group. The effect of GSH on callus induction was insignificant. The addition of 0.10 gL-1 to stock tree I for 30 days resulted in only a 150% higher induction rate compared to the control group. When 1.00 mgL-1 BL was applied to explants with weak self-induction ability (stock tree III) for 15 days, the callus induction rate increased to 600% of that of the control group. The callus induction rate further increased to 800% of the control group after 50 mgL-1 BL were added to stock tree III for 15 days. This study presents a method to improve the induction of embryogenic callus tissue in Korean pine.