**1. Introduction**

A fundamental biotechnological method, genetic engineering, enables the production of plants with desired properties. Further breeding of obtained plants is possible by another biotechnological tool of great importance such as *in vitro* culture techniques. Applying of tissue culture procedures enables regeneration and multiplication of desired plants in controlled conditions in short time periods. Developing of plant tissue cultures also allows preservation and improvement of plant species endangered in nature, especially medicinal plant species such as e.g. common centaury (*Centaurium erythraea* Rafn.).

#### **1.1 Genetic transformations of plants**

Genetic engineering of plants represents a unique field of biotechnology where genes and other DNA sequences are manipulated to obtain plants with certain desired properties. The necessary steps in genetic engineering are the isolation and modification of the gene of interest, the vector construction, transformation and

the final selection of transgenic plants. Genetic transformation of plants implies stable incorporation of foreign genes into the plant genome [1]. Genetic transformation of plants can be very successfully achieved in two ways:


Direct gene transfer techniques are continually developing and improving over the years. However, a considerable variation in the stability, integration and expression of the introduced gene represent their significant deficiencies. On the other hand, techniques of gene transfer through bacteria of the genus *Agrobacterium* have proven to be very efficient and straightforward. These techniques allow a more precise and stable integration of the desired gene into the plant genome [2].
