Rooting and acclimatization of in vitro produced plants of Prunus cerasus L. 'Ksenia'

Cherry (Prunus cerasus L.) is an economically important fruit crop in Central Europe. In Ukraine, it is cultivated on ca. 20 thousand hectares and new high-yielding cultivars with favorable traits are highly desirable. In cherry, all trees of a cultivar grown in farmers’ fields represent a single vegetatively propagated genotype. Micropropagation is widely used to quickly obtain sufficient quantities of plants with preserved genetic uniformity and of high phytosanitary quality, which is needed at introduction of new cultivars on the market. However, cultivar characteristics, explants origin, conditions of in vitro establishment, propagation, nutrient medium composition, etc., may have a significant impact at various stages of micropropagation. The final and most crucial stage of in vitro propagation is the rooting of explants and their adaptation to ex vitro conditions. The objective of this study was to develop an effective micropropagation technology for a new cultivar of Prunus cerasus L. ‘Ksenia’. We evaluated the effect of three types of auxins at different concentrations on rooting in vitro and the types of substrate for the acclimatization stage. For rooting, we used indole-3-butyric acid (IBA), naphthaleneacetic acid (NAA), and indole-3-acetic acid (IAA) at concentrations of 0.2, 0.5, 0.7, and 1 mg L^-1. The results revealed that NAA acid was the most effective. Its use, especially at low concentrations, ensures 100% rooting within 45 days of cultivation. The addition of IBA reduced rooting efficiency but positively influenced the number and length of the roots. The number of rooted microshoots did not exceed 50% when IAA was applied. For the adaptation of rooted microshoots, four types of substrate mixtures were evaluated, including peat, perlite, sand, and cocopeat. The mixture based on peat showed the high ratio of adapted plants (82-84%) and positively impacted the growth and development of plantlets during container cultivation. This method will be used as an element in the process of in vitro therapy for obtaining virus-free plants of this cultivar and establishing nuclear stock plants.