Auxins in the propagation of red-fleshed pitaya ‘Physical Graffiti’ (Selenicereus guatemalensis × S. undatus) cuttings in three substrates

The success of vegetative propagation in pitaya depends on both endogenous and exogenous factors, such as cutting size, the application of auxin-type growth regulators, and the substrate used. The objective of this study was to evaluate the effect of auxins (naphthaleneacetic acid [NAA] and indole-3-butyric acid [IBA]) and different substrates on the rooting of cuttings of various sizes in red-fleshed pitaya ‘Physical Graffiti’. A 3×2×3 factorial design was used, with the factors being: auxin concentration (NAA + IBA at 0, 20 + 5 and 40 + 10 ppm), cutting size (20 and 40 cm) and substrate type (sand; sand:vermicompost [1:1, w/w]; and vermicompost). Root length and number, as well as fresh and dry biomass of both roots and cuttings, were evaluated. Analyses included analysis of variance, Tukey’s multiple comparison tests, and Pearson correlations. The best rooting performance ‒measured as root length (15.8 cm), number of roots (80.5), fresh biomass (8.6 g), and dry biomass (3.3 g)‒ was obtained with 20 cm cuttings immersed for 30 seconds in a solution of 20 ppm NAA + 5 ppm IBA and grown in a sand:vermicompost substrate. The combination of NAA and IBA in mixed substrates represents a viable option to optimize propagation by cuttings of red- fleshed pitahaya ‘Physical Graffiti’.