Enhancing Drought Tolerance in Food Crops: Recent Non-genetic Engineering Strategies
Abstract
This review synthesizes recent advances in non-genetic engineering strategies to enhance crop drought tolerance, focusing on phytohormones, priming, bioaugmentation, non-phytohormone organic supplementation, and inorganic supplementation. Across these approaches, drought resilience is consistently improved through coordinated regulation of antioxidant defense, osmotic adjustment, photosynthetic stability, water-use efficiency, and stress-responsive gene networks. Phytohormone applications, particularly melatonin, brassinosteroids, and jasmonates, enhanced drought tolerance by reducing reactive oxygen species and lipid peroxidation while strengthening antioxidant systems. Melatonin increased ascorbate (16.35%) and glutathione (91.49%) contents in kiwifruit and elevated antioxidant enzyme activities by up to 10.35% to 110.41% in oat seedlings. Photosynthetic performance also improved substantially, with net photosynthesis in brassinosteroid-treated plants increasing from 2.01 to 6.1 μmol CO₂/m²/s¹. Drought priming induced stress memory, improving hydraulic regulation and photosynthetic resilience, with recurrent priming increasing leaf water retention by 21.88% in tea plants. Bioaugmentation using arbuscular mycorrhizal fungi enhanced root volume by 172.11% in citrus and increased maize biomass by up to 1,189 to 2,062 g/plant under drought. Antioxidant enzyme activities were enhanced by up to 98.63%. Organic supplementation (e.g., seaweed extracts, fulvic acid, ethanol) improved leaf water content by ~50% and stomatal conductance by 46%, while inorganic amendments such as silicon and potassium increased yield by up to 55% and water-use efficiency by over 100% in some systems. Nanoparticles (ZnO, TiO₂, CeO₂) further improved drought tolerance but exhibited dose-dependent effects. Overall, integrated bioaugmentation and inorganic supplementation emerge as the most scalable strategies, while priming and phytohormones offer high mechanistic efficacy.