The Effect of Auxin on Vegetative Propagation of Idesia polycarpa Maxim

Idesia polycarpa is a deciduous ornamental tree with 10–20 cm panicles of yellow-green flowers in spring and summer turning to orange-red berries in fall and winter. There is no recent documentation of vegetative propagation protocols for I. polycarpa. The objective of this study was to evaluate the effectiveness of different harvest dates and auxin concentration combinations on rooting of shoot tip cuttings. In 2009, cuttings were collected at nine dates between June and August. At each collection date, five replications of five softwood cuttings were treated with three K-IBA auxin concentrations of 0, 5000, and 10000 mg∙L^-1 giving a total of 25 cuttings per treatment.  Increases in K-IBA up to 10000 mg∙L^-1 resulted in higher rooting percentages for most collection dates, though rooting percentage did not exceed 32 percent for any given treatment combination. Additionally, rooting percentages did not differ among cutting dates.  In 2010, a second study with four replications of five cuttings was conducted with two cutting collection dates (June and September), and three K-IBA auxin concentrations of 0, 10000, and 20000 mg∙L^-1.  The two cutting collection dates corresponded to two shoot tip cutting types, softwood (June) and semi-hardwood (September).  For softwood cuttings, the application of auxin improved rooting success versus the control from 0% to 60% and 75% for 10000 and 20000 mg∙L^-1, respectively. Rooting of semi-hardwood cuttings was improved to 40% and 45%. There was no statistical difference between the two high concentrations for both cutting types. For all rooted cuttings, softwood cuttings showed a greater root length (4.83 cm, length of longest root) compared to semi-hardwood cuttings (1.82 cm). These data indicate the necessity of supplemental auxin in rooting I. polycarpa cuttings and that softwood cuttings are preferable versus semi-hardwood cuttings.