Post-aseptic adaptation and ex vitro propagation of Ukrainian cultivars of Paulownia Sieb. et Zucc.

Plantation forestry using highly productive and fast-growing plants involves the use of high-quality improved planting material for genetic constancy, which is solved by microclonal reproduction. However, the high survival rate and stability of plants obtained in vitro are realised as a result of post-aseptic adaptation of regenerants. Therefore, the research aims to improve the survival techniques of paulownia regenerants of the Ukrainian varieties “Feniks” and “Enerdzhy” ex vitro. The study was conducted in December 2021 on the Ukrainian paulownia varieties “Feniks” and “Enerdzhy”, cultivar “Feniks”. The survival rate, development of regenerants, and their damage by facultative saprophytic pathogens differed on substrates of organic (Eco Plus, La Flora, Jiffy, coconut peat, cotton wool) and mineral (vermiculite, perlite, sand) origin. The biological products “Rise P” and “Prestop” proved to be effective for the control of pathogenic microorganisms on substrates of organic origin. The technological feasibility of using perlite substrate is substantiated. The pathophysiology of ex vitro regenerants of paulownia under Fusarium is described. The thickness of the films used for sheltering influenced the regeneration, engraftment, microbial damage, and temperature of the wet chambers. Growing regenerants with covering films of different thicknesses showed a high survival rate in the variants with stretch films of 10 and 23 μm thickness. In the case of using polyethene films with thicknesses of 60, 80 and 100 μm, a sharp increase in temperature was observed, which was 48, 53 and 650C, respectively. At these high temperatures, most of the regenerants died, after which they were colonised by facultative saprophytes, and the tissues were completely macerated within two days. The optimal ratio of juvenility reduction and the acquisition of adaptive traits is characteristic of the second, third and fourth generation ex vitro. The expediency of propagation by stem cuttings up to the fourth generation, which preserves the regenerative ability of shoot cuttings, was substantiated. The practical results of the research are a protocol for growing paulownia plants in vitro and ex vitro on different types of substrates for use by institutions engaged in paulownia propagation