Soil is the first component of the environment that can be effected by GM plants, because they do not only consume the nutritive substances from the soil, but also release there different compounds during a growing period, and leave in the soil their remains. If the plants are modified to increase their resistance to plant pathogens, particularly bacteria, they can also affect the other microorganisms important for plant development. Also there are no considerable data about possible effect of GM plants on soil organic matter and chemical processes in soil. For the experiment it is planned to use transgenic potato plants (Solanum tuberosum L. cv. Desiree) expressing a chimerical gene for T4 lysozyme for protection against bacterial infections; - obtaining and short-term growing of GM plants in laboratory conditions; - extraction and collection of root exudates and microbial metabolites from rhizosphere; - analysis of these exudates by Pyrolysis-Field Ionisation Mass Spectrometry (Py-FIMS) in comparison with the exudates of wild-type plants and transgenic controls not harbouring the lysozyme gene, and with dissolved organic matter from non-cropped soil; - creation of 'fingerprints' for each new transgenic line in combination with certain soil on the basis of marker signals. Expected impacts: - New highly cost-effective express testing system for the risk assessment of genetically modified plants at the earliest stages of their introduction; - The conclusion about safety/danger of GM plants for the soil ecosystems; - Model for prediction of possible risk caused by GM plants.