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A maize (Zea mays L.) field experiment conducted during the crop season 2022 at the Experimental Farm, Al-Mahnawiya, Extension Training Center, Babylon, Iraq, sought to evaluate the water stress tolerance of four maize cultivars under different irrigation regimes. The experiment used a randomized complete block design (RCBD) with a split-plot arrangement and three replications. Four irrigation treatments comprised the main plots: full irrigation (control), no irrigation during elongation (Gs-V7), no irrigation during grain-filling (Gs-R2), and no irrigation during elongation and grain-filling (Gs-V7+R2). The subplots included four maize cultivars: Furat, Dijlah, ZP, and Konsens. Leaf area decreased by 1873.76 cm2 plant-1 during the elongation stage (Gs-V7) due to non-irrigation. Nonirrigation during elongation (Gs-V7) and both elongation and grain-filling (Gs-V7+R2) reduced rows per ear, grains per row, and 500-grain weight at 11.65 and 11.02 rows ear-1, 26.77 and 23.23 grains row-1, and 54.90 and 63.94 g, respectively. Withholding irrigation during the elongation stage (Gs-V7), the filling (Gs-R2), and the elongation and filling phases all had decreased grain output. The lack of irrigation during the elongation stage (Gs-V7) boosted the ZmMYBE1 gene expression in vegetative phases. However, irrigation suppression did not impact the ZmMYBE1 gene expression in reproductive stages. The cultivar Furat had the most rows (17.58) and grains per row (37.58), and the cultivar Konsens had the maximum mean of 500-grain weight (84.36 g). [ABSTRACT FROM AUTHOR]

The influence of 24-epibrassinolide (EBR24), applied to leaves at a concentration of 5 μM, on plant physio-biochemistry and its reflection on crop water productivity (CWP) and other agronomic traits of six maize hybrids was field-evaluated under semi-arid conditions. Two levels of irrigation water deficiency (IWD) (moderate and severe droughts; 6000 and 3000 m3 water ha−1, respectively) were applied versus a control (well-watering; 9000 m3 water ha−1). IWD reduced the relative water content, membrane stability index, photosynthetic efficiency, stomatal conductance, and rates of transpiration and net photosynthesis. Conversely, antioxidant enzyme activities and osmolyte contents were significantly increased as a result of the increased malondialdehyde content and electrolyte leakage compared to the control. These negative influences of IWD led to a reduction in CWP and grain yield-related traits. However, EBR24 detoxified the IWD stress effects and enhanced all the above-mentioned parameters. The evaluated hybrids varied in drought tolerance; Giza-168 was the best under moderate drought, while Fine-276 was the best under severe drought. Under IWD, certain physiological traits exhibited a highly positive association with yield and yield-contributing traits or CWP. Thus, exogenously using EBR24 for these hybrids could be an effective approach to improve plant and water productivity under reduced available water in semi-arid environments.

The influence of 24-epibrassinolide (EBR24), applied to leaves at a concentration of 5 μM, on plant physio-biochemistry and its reflection on crop water productivity (CWP) and other agronomic traits of six maize hybrids was field-evaluated under semi-arid conditions. Two levels of irrigation water deficiency (IWD) (moderate and severe droughts; 6000 and 3000 m3 water ha−1, respectively) were applied versus a control (well-watering; 9000 m3 water ha−1). IWD reduced the relative water content, membrane stability index, photosynthetic efficiency, stomatal conductance, and rates of transpiration and net photosynthesis. Conversely, antioxidant enzyme activities and osmolyte contents were significantly increased as a result of the increased malondialdehyde content and electrolyte leakage compared to the control. These negative influences of IWD led to a reduction in CWP and grain yield-related traits. However, EBR24 detoxified the IWD stress effects and enhanced all the above-mentioned parameters. The evaluated hybrids varied in drought tolerance; Giza-168 was the best under moderate drought, while Fine-276 was the best under severe drought. Under IWD, certain physiological traits exhibited a highly positive association with yield and yield-contributing traits or CWP. Thus, exogenously using EBR24 for these hybrids could be an effective approach to improve plant and water productivity under reduced available water in semi-arid environments. [ABSTRACT FROM AUTHOR]