Drought tolerance is expressed as the ability of a variety to maintain stable productivity during soil moisture shortages. The trait is manifested through biological drought escape in early-maturing forms, anatomical and morphological adaptations such as waxy bloom and leaf pubescence, as well as the physiological resistance of cellular systems to dehydration and high temperatures.
Tolerance assessment in the variety testing system is conducted by field comparison with a standard during adverse years, where the variety is rated in scores based on yield levels. Additionally, visual symptoms are taken into account, including leaf rolling, plant height, and the retention of green color (stay-green), as well as laboratory indicators of tissue water-holding capacity and proline accumulation.
The effectiveness of a variety depends on its plasticity and ability to pass through critical development phases, such as jointing or heading, without critical loss of productivity. Drought tolerance often correlates with overall adaptability to other stress factors; therefore, when selecting, it is important to consider the homeostatic nature of the variety and the results of trials in specific agro-climatic zones.