Abstract
BACKGROUND: The study focuses on the global challenge of drought stress, which significantly impedes wheat production, a cornerstone of global food security. Drought stress disrupts cellular and physiological processes in wheat, leading to substantial yield losses, especially in arid and semi-arid regions. The research investigates the use of Spirulina platensis aqueous extract (SPAE) as a biostimulant to enhance the drought resistance of two Egyptian wheat cultivars, Sakha 95 (drought-tolerant) and Shandawel 1 (drought-sensitive). Each cultivar's grains were divided into four treatments: Cont, DS, SPAE-Cont, and SPAE + DS. Cont and DS grains were presoaked in distilled water for 18 h while SPAE-Cont and SPAE + DS were presoaked in 10% SPAE, and then all treatments were cultivated for 96 days in a semi-field experiment. During the heading stage (45 days: 66 days), two drought treatments, DS and SPAE + DS, were not irrigated. In contrast, the Cont and SPAE-Cont treatments were irrigated during the entire experiment period. At the end of the heading stage, agronomy, pigment fractions, gas exchange, and carbohydrate content parameters of the flag leaf were assessed. Also, at the harvest stage, yield attributes and biochemical aspects of yielded grains (total carbohydrates and proteins) were evaluated. RESULTS: The study demonstrated that SPAE treatments significantly enhanced the growth vigor, photosynthetic rate, and yield components of both wheat cultivars under standard and drought conditions. Specifically, SPAE treatments increased photosynthetic rate by up to 53.4%, number of spikes by 76.5%, and economic yield by 190% for the control and 153% for the drought-stressed cultivars pre-soaked in SPAE. Leaf agronomy, pigment fractions, gas exchange parameters, and carbohydrate content were positively influenced by SPAE treatments, suggesting their effectiveness in mitigating drought adverse effects, and improving wheat crop performance. CONCLUSION: The application of S. platensis aqueous extract appears to ameliorate the adverse effects of drought stress on wheat, enhancing the growth vigor, metabolism, and productivity of the cultivars studied. This indicates the potential of SPAE as an eco-friendly biostimulant for improving crop resilience, nutrition, and yield under various environmental challenges, thus contributing to global food security.