Comparison of the efficiency of synthetic auxins and biostimulants and two types of substrate in rooting of shoot cuttings in ‘Pi-ku 1’ rootstock

The low-cost propagation of semi-dwarf cherry rootstock is an essential issue in the production of maiden trees of this species. Among the promising rootstocks is ‘Pi-ku 1’, obtained in Germany. However, the possi-bility of its propagation using shoot cuttings has not been investigated. It was the purpose of this study. Two ways of cuttings treatment before placing them in the substrate were assessed. One used two preparations in powder (Rhizopon AA and Ukorzeniacz AB), and the second used two alcoholic auxin solutions (IAA and IBA). Instead of synthetic auxins, foliar spraying with two biostimulants was performed (Goteo and Bispeed). All the applied treatments increased the rooting percentage of ‘Pi-ku 1’ rootstock cuttings compared to the control from 5% for Rhizopon AA to 18.2% for auxin IBA. The exception was the lack of a positive effect of the Bispeed biostimulant (less than 5.2%). The use of synthetic auxins increased the number of cutting roots more than three times (IBA) or almost twice (Ukorzeniacz AB) and their length more than twofold (IAA, Rhizopon AA) in proportion to the control. The effect of synthetic auxin treatments on the remaining growth parameters under study was also positive. Foliar treatment of cuttings with biostimulants did not change their growth. Only in one of the two years of the study did the fresh mass of cuttings improve after using Goteo biostimulant (7.5%). As part of the experiment, the effect of two substrate types – peat mixed with perlite and peat with sand – was also tested. During the two years of research, the cuttings were rooted several percent better in peat and sand (2.7% – 2018 and 4.4% – 2019). Using peat with sand as a rooting substrate signifi-cantly improved the number and length of roots (11.90 and 125.10) of Pi-ku 1 rootstock cuttings compared to the second one (9.23 and 109.08, respectively). All treatments applied to cuttings, except two biostimulants, increased the amount of chlorophyll in the leaves.