https://doi.org/10.37229/fsa.fja.2026.05.09

Garlic (Allium sativum L.) is a vital crop with significant medicinal and culinary value, yet it is highly sensitive to water stress due to its shallow root system. This study was conducted during the 2022/2023 and 2023/2024 seasons at the El-Qanater El-Khiria Horticulture Research Station in Egypt to investigate the potential of foliar applications of melatonin (MT) and thiourea (TU) to mitigate the adverse effects of drought on garlic growth, yield, and storage ability. The experiment employed a split-plot design with three irrigation levels based on evapotranspiration (100%, 75% and 50% Etc) and three foliar treatments; melatonin (50 mg/l), thiourea (5 mM), and tap water as a control. Results indicated that water stress significantly reduced vegetative growth parameters, including plant length, leaves number, and bulb fresh weight, with the 50% ETc level yielding the lowest values. Conversely, the 100% ETc irrigation level (1468.36 m³ water/fed. as average of the seasons) with melatonin (50 mg/l), followed by 100% Etc with thiourea (5 mM), gave the highest growth and yield characteristics as well as reduced weight loss percentage during storage period. Foliar application of melatonin and thiourea effectively counteracted drought-induced Impairment. Melatonin treatment significantly improved plant length, bulb diameter, and total chlorophyll content, likely due to its role as an antioxidant and regulator of plant growth. Thiourea also enhanced physiological resilience by increasing proline accumulation and maintaining higher photosynthetic rates. 75% ETc irrigation level (1180.06 m³ water/fed. as average of the seasons) with melatonin (50 mg/l) increased water use efficiency. The highest proline levels were recorded under severe water stress (50% Etc at 891.46 m³ water/fed. as average of the seasons) when combined with melatonin, indicating enhanced osmotic adjustment. Overall, the study demonstrates that foliar applications of melatonin or thiourea can serve as effective strategies to improve the drought tolerance and productivity of garlic crops in arid and semi-arid regions.