Effect of exogenous proline on drought stress tolerance in wheat (Triticum aestivum L.) cultivars

Due to the scarcity of irrigation water and to achieve maximum benefit from the available irrigation water, this study investigated the impact of exogenous proline application on drought tolerance in three wheat (Triticum aestivum L.) cultivars and evaluated their water use under stress conditions. A factorial field experiment was conducted using a split-split plot design with three factors at three levels each. The main plot factor was drought stress, with three levels: S1 (control) involved irrigation with 50 % of the available water between field capacity (FC) and wilting point(WP); S2 represented mild drought with 30 % available water (70 % reduction); S3 represented severe drought with 10 % available water (90 % reduction). The second factor (subplot) was proline concentration: P1 (0 mg L-1), P2 (25 mg L-1) and P3 (50 mg L-1). The third factor (sub-subplot) was wheat cultivar: Ibaa 99, Adnaniyah and Sham 6. A 90 % reduction in available water significantly decreased vegetative and yield parameters, including plant height (58.53 cm), spikes per plant (3.98), seeds per spike (37.86), total yield (3.47 tons·ha-1), flag leaf area (25.75 cm²), chlorophyllcontent and water use efficiency (1.6 kg grains m-3 water). The highest water use efficiency was recorded under 30 % available water, while the maximum grain yield (6.07 tons ha-1) was achieved under 50 % available water. Foliar application of 50 mg L-1 proline (P3) increased grain yield and improved water use efficiency to 1.61 kg grains m-3 water. Although interactions between drought stress and proline concentration were not statistically significant, Sham 6 consistently outperformed Ibaa 99 and Adnaniyah across most growth and yield parameters.