African marigold (Tagetes erecta L.), a member of the Asteraceae family, contains valuable bioactive compounds like carotenoids (Lutein and zeaxanthin), utilized in supplements, food coloring, and poultry feed additives. In light of utilizing dry, low-yield lands, this study focused on enhancing African marigolds’ quantitative and qualitative characteristics through melatonin foliar treatments (0, 100, and 200 µmol) under varying stress levels (100 %, 80 %, 60 %, and 40 % FC) that were implemented as a factorial experiment using a completely randomized design with 4 replications. Results indicated deteriorating effects on African marigold flowers under increasing drought stress, mitigated by melatonin treatments that improved flower quality, reduced stress index, and enhanced agro-morphological traits. Melatonin treatments increased lutein and zeaxanthin content while maintaining chlorophyll, carotenoids, and plant growth under drought stress. Moreover, they reduced hydrogen peroxide, superoxide, electrolyte leakage, maintained protein content, DPPH activity, and enhanced antioxidant and osmolality capacity such as antioxidant enzymes activity (catalase, peroxidase, superoxide dismutase) proline and gamma-aminobutyric acid (GABA) content conferring drought resistance. The study suggests that the 200 µmol melatonin treatment shows superior efficacy in enhancing African marigold yield and quality in drought stress conditions.
