Effect of indole-3-butyric acid and gibberellic acid on rooting and growth of arracacha propagules

Ex situ conservation of Andean roots requires asexual propagation to maintain germplasm genetic integrity. This study evaluated the effects of phytohormones on adventitious root formation and growth in low-rooting arracacha (Arracacia xanthorrhiza) propagules (accession CUI15010083) from Colombia Germplasm Banks for Food and Agriculture. Indole-3-butyric acid (IBA; 7.5, 15.0, 1000 or 3000 mg L⁻¹) and gibberellic acid (GA; 50 or 100 mg L⁻¹) were applied at varying immersion times (1, 30 min for IBA; 5 min for GA), with a water-only control. Propagation was assessed across three phases: 1) water-based rooting, 2) acclimatization in soil, and 3) field transplant, measuring vigor, plant height, leaf length, and fresh/dry biomass. High IBA concentrations (1000-3000 mg L-¹; 1 min immersion) induced propagule mortality. Lower IBA doses (≤15 mg L⁻¹; 30 min immersion) enhanced root quality, producing propagules with intermediate root category scores, though statistically comparable to controls. GA treatments (≤100 mg L⁻¹; 5 min immersion) showed no biomass differences relative to controls. Low-concentration IBA stimulated early rooting, improving adventitious root development, survival, and subsequent growth. GA primarily promoted cell elongation, confirming its role as a vegetative growth enhancer.