Agronomic and Biochemical Responses of Blackberry to Alternative Deficit Irrigation Strategies to Increase Stress Tolerance

Increasingly severe drought increases the demand for clean water resources, which necessitates the economical use of water, especially in arid and semi-arid areas. Determining the stress tolerance of plants under different irrigation strategies is very important for selecting suitable plants for regions with water shortages. This study aimed to determine the water–yield relationships of blackberry, which is a plant allowing production in small areas and has a high economic return. In the study, the response of two different blackberry varieties (‘Bursa II’ and ‘Chester’) to five different irrigation levels, including intermittent water stress (IWS) and continuous water stress (CWS), was assessed in field conditions for 2 years (2021 and 2022). As a result of the research, the highest plant water consumption was calculated in ‘Bursa II’ (C<inf>B</inf>) and ‘Chester’ (C<inf>C</inf>) varieties with 571.8 and 481.2 mm, respectively, in full irrigation (I<inf>100</inf>) applications. The highest yield was obtained from C<inf>B</inf>I<inf>100</inf> treatment as 1444.8 kg da⁻¹ and 1610.5 kg da⁻¹ in the 2021 and 2022 trial years, respectively, and significant decreases were recorded in fruit yield under severe water stress conditions. While decreases were observed in physiological parameters such as stomatal conductance and leaf relative water content (LRWC) with increasing water stress, the amount of substances that caused oxidative damage such as H<inf>2</inf>O<inf>2</inf> and malondialdehyde increased. The results of the yield response factor (ky), an important parameter in evaluating the plant’s response to water stress, showed that blackberry, a perennial plant, can adapt to stress conditions. As a result, it was concluded that blackberry, which can tolerate moderate drought severity, can be recommended as an alternative plant for arid and semi-arid areas, and that it would be useful to try IWS on different plants sensitive to water restriction.