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Increasing the rate of biomass gain is one of the most important areas in the breeding of woody plants. However, the application of classical breeding approaches to woody plants is significantly limited due to the long breeding cycles of many species. The development of genetic engineering and genome editing technologies has made it possible to improve tree traits in a relatively short time. Genes for the biosynthesis of phytohormones are often the target of genetic manipulations aimed at accelerating plant growth. Gibberellin 20-oxidase is a key enzyme responsible for the active production of gibberellins in plants and is, therefore, a preferred target for genetic manipulation to increase growth rate. This paper presents an original study on the production of Populus×berolinensis K. Koch, transformed by gene encoding gibberellin 20-oxidase from Arabidopsis thaliana (L.) Heynh. (AtGA20ox1), and the initial evaluation of the phenotypic effects of the transformation. The main phenotypic manifestations of the transformation were a pronounced elongation of the stem due to an increase in the size of the internodes, a slight thinning of the stem, as well as lengthening and narrowing of the leaves. Our results showed that AtGA20ox1 gene overexpression in Berlin poplar leads to an acceleration of its growth by at least three times under in vitro conditions compared to control values. The negative effects of transformation, expressed in weak rooting or a high frequency of apical necrosis and observed in some transgenic strains at the initial stages of selection, do not appear in the three final selected strains. [ABSTRACT FROM AUTHOR] more...

The rapid advancement of genetic technologies has made it possible to modify various plants through both genetic transformation and gene editing techniques. Poplar, with its rapid in vitro growth and regeneration enabling high rates of micropropagation, has emerged as a model system for the genetic transformation of woody plants. In this study, Populus × berolinensis K. Koch. (Berlin poplar) was chosen as the model organism due to its narrow leaves and spindle-shaped crown, which make it highly suitable for in vitro manipulations. Various protocols for the Agrobacterium-mediated transformation of poplar species have been developed to date. However, the genetic transformation procedures are often constrained by the complexity of the nutrient media used for plant regeneration and growth, which could potentially be simplified. Our study presents a cheaper, simplified, and relatively fast protocol for the Agrobacterium-mediated transformation of Berlin poplar. The protocol involved using internode sections without axillary buds as explants, which were co-cultivated in 10 µL droplets of bacterial suspension directly on the surface of a solid agar-based medium without rinsing and sterile paper drying after inoculation. We used only one regeneration Murashige and Skoogbased medium supplemented with BA (0.2 mg·L−1), TDZ (0.02 mg·L−1), and NAA (0.01 mg·L−1). Acetosyringone was not used as an induction agent for vir genes during the genetic transformation. Applying our protocol and using the binary plasmid pBI121 carrying the nptII selective and uidA reporter genes, we obtained the six transgenic lines of poplar. Transgenesis was confirmed through a PCR-based screening of kanamycin-selected regenerants for the presence of both mentioned genes, Sanger sequencing, and tests for detecting the maintained activity of both genes. The transformation efficiency, considering the 100 explants taken originally, was 6%. [ABSTRACT FROM AUTHOR] more...