Effects of Planting Time, Irrigation System, Rooting Medium, and IBA Concentration on Cutting Propagation of the Persimmon Dwarfing Rootstock 'MKRI'

摘要

A practical dwarfing rootstock for the persimmon (Diospyros kaki Thunb.), 'MKRI', is normally propagated by cuttings collected from root suckers. However, optimal conditions for propagating leaf-bud cuttings from this variety have not been researched. Thus, several methods influencing survival, rooting and root system structure were investigated in the present study. Cuttings planted in late June survived and rooted better than those planted in late July and August, and the rooted cuttings planted in late June also survived winter better. The two different irrigation methods, either a mist system, or a tray with a polyethylene tent (tray-polyethylene-tent, or TPT) did not significantly affect survival and rooting. However, the primary root length was longer in the TPT and the root dry weight was heavier under the mist system. Although the rooting medium did not significantly affect the survival of cuttings, the rooting percentage of cuttings planted in perlite was the lowest. The cuttings planted in peat in late June and placed under the mist system had adventitious root initials 17 days after planting and adventitious roots were observed on the cuttings by 22 days after planting. A quadratic regression curve predicted that the highest rooting percentage would result from treatment of 'MKRI' cuttings with approximately 2000 mg.L-1 indole-3-butyric acid (IBA), while a different curve predicted that the lowest root number would result from treatment with approximately 1000 mg.L-1 IBA. Interestingly, more than 50% of the cuttings treated with a quick dip in 0 mg.L-1 IBA successfully rooted. Although the treatment with a higher IBA concentration resulted in greater root system development on the rooted cuttings, treatment with very high IBA concentrations such as 4000 or 5000 mg.L-1 caused fading of leaves and dieback of cuttings.