Kratom (Mitragyna speciosa), a tropical evergreen tree indigenous to Southeast Asia, has gained attention in recent years due to its potential as a natural medicine for pain management and its ability to alleviate symptoms associated with opioid withdrawal. These properties indicate that kratom could be a promising candidate for drug development aimed at addressing the opioid epidemic. Despite growing interest in kratom’s therapeutic applications, its domestic cultivation remains limited, and investigations on vegetative propagation methods are unavailable. The traditional propagation technique, i.e., rooting stem cuttings in greenhouse settings with misting systems, has resulted in inconsistent success and varying quality. To address these challenges and improve propagation efficiency, this study evaluated the use of an aeroponic system to root kratom cuttings in controlled environments under various conditions. Stem cuttings were cultured in aeroponic devices under three photoperiods provided by light-emitting diode (LED) lights in environmentally controlled rooms. Rooting percentages reached 87, 88, and 90% in six weeks under 10-, 14-, and 24-hr photoperiods, respectively. Cuttings rooted three days earlier under 24-hr compared to those rooted at 10- and 14-hr photoperiods. On the other hand, the 14-hr photoperiod led to the highest root dry mass,109% and 14% greater than the 10- and 24-hr treatments, respectively. Furthermore, propagules rooted under 14-hr photoperiod had the highest total root length, 92% and 33% greater than those rooted under 10- and 24-h photoperiods. Additionally, the 14-hr photoperiod significantly enhanced root projected area, surface area, root volume, and number of root forks by 82, 81, 80, and 124%, respectively compared to those rooted under the 10-hr photoperiod, although these enhanced parameters were not statistically different from those rooted under 24-hr photoperiod. Our results showed that photoperiod generally had little effect on rooting percentages, shoot growth (e.g. new leaf number and new leaf area), average root diameter, and number of root tips and crossings; higher rooting quality was produced under 14-hr photoperiod. These findings provide valuable insights for improving rooting of this novel medicinal plant.
