Climate change resulting in increasingly frequent and severe drought periods highlights the importance of research and breeding which aims to identify and produce better drought stress-tolerant wheat lines, thus increasing crop security. One of the most important components of surviving the drought period are the dynamics of root development, and the shape of root structure, which helps the plant through more efficient water absorption and also as an emergency reserve for "hard times" until the end of the generative phase.

In our experiments, we investigated the early root development of 18 winter wheat seedlings in a hydroponic system and the root structure of the same 18 full-grown (BBCH 85) wheat variates in greenhouse cultured in classified KH 30 sand in PVC tubes with 75 cm height and 11 cm diameter.

The seedlings were watered with Hoagland's solution in a half-strength dose. In order to osmotically inhibit the water absorption of the treated group, polyethylene glycol (PEG-6000) was applied at a concentration of 18%. After four days of treatment, the root parameters were measured using the WinRHIZO root scanner and software (Regent Instruments Ltd, Canada). As a result of PEG treatment, it is declarable, that the total length, surface and volume of the root in all varieties decreased, but the rate of the reduction showed significant differences among the varieties.

The greatest reduction was measured in the Babuna and Bayraktar varieties, where the reduction in length exceeded 90% (91.8%, 93.5%), while the decrease in root length of four varieties (Disponent, Aura, Salamouni and KWS Scirocco) didn't even reach 50%. All four varieties can be classified into middle and late ripening groups.

The decrease in root length (and volume) caused by PEG treatment during germination can be paralleled with the degree of drought tolerance simulated during field and rain shelter experiments. However, some cultivars, showing good drought tolerance under field conditions, did not tolerate water shortages well during the seedling stage.

Those wheats which grew in sand tubes and examined at BBCH 85 stage got complete water withdrawal from BBCH 30 stadium. As a result, total root length got significantly shorter in most of the varieties, but the average diameter got significantly thicker. Therefore, it was concluded that the water shortage resulted in a decrease in the total root length while the root volume increased under drought stress condition. The root surface area shoved high variability.

Acknowledgements: The researches were supported by the TKP2021-NKTA-06 project provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund and the Bolyai János Research Fund No: BO/00384/23/4