ASHS 2015 Annual Conference

The Amelanchier spicata complex (dwarf serviceberry or shadbush) comprises North American shrubs in the Rosaceae with aesthetic value and edible fruits for humans and wildlife.  Our objective was to evaluate the effects of auxin concentration and method of auxin delivery (K-IBA in water vs. IBA in 50% ethanol) on adventitious root development of softwood stem cuttings from phenotypically distinct plants from two provenances in Maine.  Cuttings were treated with a quick-dip in IBA or K-IBA, at concentrations of 3000, 5000, and 8000 ppm.  Cuttings serving as controls were treated with distilled water or 50% ethanol.  After 52 days under mist, we recorded the percentage of cuttings that rooted, as well as a subjective assessment of rooting quality.  Provenance had a modest influence on rooting success, but data were pooled because there was no interaction between provenance and treatment.  Auxin treatment enhanced rooting percentage (75% with auxin and 50% without) and quality of roots on cuttings that rooted (mean scores of 3.1 with auxin and 2.1 without), but we found no differences in outcomes among auxin concentrations evaluated.  A. spicata was likewise insensitive to method of auxin delivery, as treatment with IBA or K-IBA produced similar results.  Since ~25% of cuttings failed to root despite auxin treatment, and root systems that developed were not consistently robust, factors other than auxin should be investigated to improve propagation of A. spicata as a commercial crop for horticulture in North America.